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To study an association between IL-6 signaling and resistance to radiotherapy of prostate cancer (PCa) and explore the molecular mechanisms involved. IL-6 expressing C4-2 and CWR22Rv1 (C4-2IL-6/CWRIL-6) and vector control (C4-2vec/CWRvec) cell lines were developed. Radiation-sensitivities of these cells were compared in clonogenic assay, Comet assay, and γH2AX staining. In xenograft animal studies, radiation-sensitivity of C4-2IL-6 cell-derived tumors vs. C4-2vec cell-derived tumors was investigated. To reveal IL-6 downstream molecules involved in DNA repair after radiation, qPCR and Western blot analyses as well as immunofluorescence staining were performed. Transcriptional control of IL-6 on ATM and ATR molecules was also investigated. We found C4-2IL-6 and CWRIL-6 cells survived better than their vector control cells after irradiation, and animal studies confirmed such in vitro results. We discovered that DNA repair-related molecules such as ATM, ATR, BRCA1, and BRCA2 were significantly upregulated in irradiated IL-6 expressing cells compared with vector control cells. We further defined that IL-6 signaling regulated cellular expressions of ATM and ATR at the transcriptional level through the activation of Stat3 signaling pathway. IL-6 leads to PCa resistance to radiation through upregulation of DNA repair associated molecules ATM, ATR, BRCA1, and BRCA2.

Background While androgen deprivation therapy (ADT) and radiotherapy (RT) are currently used together to treat locally advanced prostate cancer (PCa), RT might have the adverse effect of increasing the PCa androgen receptor (AR) protein expression, which might then increase the resistance to continued RT. Methods We used multiple assays for RT sensitivity, protein and RNA expression of AR and related DDR genes, ROS level, DNA damage/repair level, cell cycle and apoptosis. All statistical comparisons were analyzed with t-test or one-way ANOVA. Findings We demonstrated that RT induced AR expression in C4-2 and CWR22Rv-1 cells. We found that combining RT and ASC-J9®, but not the antiandrogen, Enzalutamide, could increase radiosensitivity via inducing DNA damage, altering the AR mediated and DNA repair pathways, and activating apoptosis. ASC-J9® had little effects on normal bladder cells. Interpretation Targeting ionizing radiation (IR)-increased AR with the AR degradation enhancer, ASC-J9®, could increase the radiosensitivity while sparing adjacent normal tissue. Mechanism dissection revealed that ASC-J9®, but not Enzalutamide, treatment could increase radiosensitivity via inducing DNA damage, altering DNA repair pathways, as well as activating the IR-induced apoptosis via suppressing the pATR-CHK1 signals. Importantly, results from preclinical studies using an in vivo mouse model also demonstrated that combining RT with ASC-J9® to target AR led to better therapeutic efficacy to suppress PCa progression., Highlights • ASC-J9• enhances efficacy of radiotherapy (RT) in PCa through both AR-dependent and AR-independent mechanistic pathways. • In AR-independent pathway, ASC-J9• increases endogenous ROS and DNA damage and makes PCa cells more sensitive to RT • ASC-J9• could also reduce the DNA damage repair after RT via suppression of AR dependent DDR genes and apoptotic pathway. • From pre-clinical mouse model, we found that combining RT and ASC-J9• can provide better efficacy than RT only.

Background Despite the overall success of radiotherapy, a significant number of patients develop radioresistance, which leads to local regional recurrence and distant metastasis. We studied whether repeated radiation treatment promotes androgen-independent survival of prostate cancer (PCa) cells and their metastatic potential. We also studied whether glucocorticoid receptor (GR) increase in radioresistant cells is associated with acquisition of these aggressive characteristics. Methods Radioresistant LNCaP (LNCaPR18) and C4-2 (C4-2R26) PCa sublines were developed by repeated radiation treatments of parental cells. Levels and activations of androgen receptor (AR) and GR in radioresistant PCa cells and respective parental cells were investigated in quantitative real-time polymerase chain reaction/Western blot analyses and immunofluorescence staining. Androgen-independent survival of radioresistant cells was tested in in vitro cell growth assays and the castration-resistant survival of these cell-derived tumors were investigated in mouse xenografts. Results Higher GR levels, but lower AR levels were detected in radioresistant cells than in parental cells. Radiation-induced GR upregulation was associated with increased intracellular cyclic adenosine monophosphate. As a consequence of GR activation, LNCaPR18 cells survived well in an androgen-depleted culture condition while parental cells could not. Results of in vivo mouse studies showed survival of LNCaPR18 cell-derived tumors in castrated mice while parental cell-derived tumors regressed. The growth of LNCaPR18 cell-derived tumors in castrated mice was impaired when treated with the anti-GR agent mifepristone. In experiments with C4-2/C4-2R26 cell sets, GR activation in C4-2R26 cells increased their metastatic potential. Conclusion GR activation in radioresistant cells mediates androgen independence and facilitates PCa progression.

Previous reports, including our experimental results, showed that macrophages migrate to prostate cancer (PCa) cells. We tested whether the migrated macrophages affect the susceptibility of castration-resistant PCa (CRPC) cells to cytotoxic actions of natural killer (NK) cells. We found treatment of tumor cells with the conditioned media (CM) of the PMA/IL-4 treated THP-1 cells (M2 type macrophages) (THP-1 CM) decreased the susceptibility of tumor cells to NK cell cytotoxicity, as a result of increased programmed death receptor ligand 1 (PD-L1) and decreased NK group 2D (NKG2D) ligands in CRPC cells. Meanwhile, the decreased susceptibility of tumor cells was also detected when NK cells were treated with THP-1 CM and used in NK cell cytotoxicity tests. Therefore, we observed higher resistance of CRPC cells when both tumor and NK cells were treated with THP-1 CM than when tumor cells or NK cells were individually treated. We further discovered that the PMA/IL-4 treated THP-1 cells secrete a high level of IL-6, so blocking the IL-6 action significantly decreased the PD-L1 level while recovering the NKG2D ligands, thus increasing the susceptibility of CRPC cells to NK cell action. Moreover, we discovered that JAK-Stat3 is the most critical IL-6 downstream signaling in triggering the THP-1 CM effect. Consequently, we found the susceptibility of CRPC cells to NK cells was increased when either JAK or Stat 3 inhibitor was added when tumor cells were treated with THP-1 CM, and that the best effect was observed when the JAK inhibitor and PD-L1 Ab were added together.

Cisplatin remains the most effective therapy for non-small cell lung cancer (NSCLC). We previously have found cisplatin-resistant lung cancer cells (A549CisR and H157CisR) were more resistant to natural killer (NK) cell-mediated cytotoxicity than parental cells. We also discovered that fatty acid synthase (FASN) levels in cisplatin-resistant cells were significantly higher than in parental cells. To reveal whether a link exists between the up-regulated FASN levels and higher resistance to NK cell cytotoxicity, we performed inhibition studies using a FASN inhibitor and applied the FASN knockdown approach. In both approaches, we found that the FASN inhibition/knockdown significantly increased the susceptibility of cisplatin-resistant cells to NK cell cytotoxicity. We further found such decreased susceptibility was associated with an increased programmed death receptor ligand (PD-L1) level in cisplatin-resistant cells. In mechanisms studies, TGF-β1 was found to be the FASN downstream signaling molecule that was responsible for modulating the PD-L1 levels in cisplatin-resistant cells. Accordingly, TGF-β1 inhibition resulted in significantly increased susceptibility of cisplatin-resistant cells to NK cell cytotoxicity. We suggest that the inhibition of FASN-TGFβ1-PD-L1 axis may improve the efficacy of immunotherapy in treating cisplatin-resistant lung cancer.

Background Obesity affects prostate cancer (PCa) progression, and the periprostatic adipose tissue adjacent to the prostate is considered a driving force of disease progression. Adipocytes are the main cell population in adipose tissues and their paracrine role contributes to PCa progression, however its implication in modulating immune reactions remains largely unknown. We investigated the adipocyte role in controlling the susceptibility of castration-resistant PCa (CRPC) cells to the cytotoxic action of natural killer (NK) cells. Methods Using primary NK cells as the NK cell source, NK cell cytotoxicities to CRPC cells, either control media treated or adipocyte-conditioned media (CM) treated, were tested in lactate dehydrogenase (LDH) release-based assays. The levels of programmed death receptor ligand (PD-L1) and NK group 2D (NKG2D) ligands in adipocyte CM-treated CRPC cells were analyzed in qPCR analyses. Effects of blocking adipocyte action on altering PD-L1/NKG2D ligand levels and the susceptibility of CRPC cells to NK cell cytotoxicity were investigated. Results We found NK cell cytotoxicity to CRPC cells decreases when tumor cells are treated with adipocyte CM associated with PD-L1 and NKG2D ligand level alterations. Further, we discovered that the JAK/Stat3 signaling pathway was responsible for the adipocyte CM effect. Two adipokine molecules, IL-6 and leptin, were shown to be important in activation of the JAK/Stat3 signaling in CRPC cells to modulate the PD-L1/NKG2D ligand level alteration. Adding the inhibitors of JAK/Stat3 signaling or neutralizing antibodies of IL-6 or leptin increased the susceptibility of CRPC cells to NK cell action. Conclusions Blocking the adipocyte effect by inhibiting the IL-6/leptin-JAK/Stat3 signaling axis may enhance NK cell mediated immunity to CRPC cells and this strategy may help to develop future therapeutics to treat obese PCa patients.

To investigate whether IL‐6 signaling affects the susceptibility of castration‐resistant prostate cancer (CRPC) cells to cytotoxic action of natural killer (NK) cells, CRPC cell lines (having different IL‐6 levels) were developed by lentiviral transduction. While observing no secreted IL‐6 level in parental C4‐2 and CWR22Rv1 cells, we found the IL‐6 expression/secretion in these cells was induced after the transduction process and the IL‐6 level difference in C4‐2siIL‐6/sc and CWR22siIL‐6/sc cell CRPC cell sets could be detected. We then found that IL‐6‐knockdown cells were more susceptible to NK cell cytotoxicity than control cells due to lowered programmed death receptor ligand 1 (PD‐L1) and increased NK group 2D (NKG2D) ligand levels. In animal studies, to concur with the in vitro results, we found that IL‐6‐expressing cell‐derived tumors were more resistant to NK cell action than the tumors of IL‐6‐knockdown cells. Further, we discovered that JAK‐Stat3 is the most critical IL‐6 downstream signaling that modulates PD‐L1/NKG2D ligand levels in CRPC cells. Furthermore, inhibition of the JAK or Stat3 signaling effectively increased the susceptibility of C4‐2sc and CWRsc cells to NK cell cytotoxicity. We observed the most effective cytotoxicity when the PD‐L1 Ab and JAK inhibitor (or Stat 3 inhibitor) were used together. These results suggest that the strategy of targeting IL‐6 signaling (or its downstream signaling) may enhance the NK cell‐mediated immune action to CRPC tumors, thus yielding clinical implications in developing future immunotherapeutics of exploiting this strategy to treat patients with CRPC.

Major progress has been made clinically in inhibiting the programmed death receptor 1 (PD-1)/PD-L1 interaction to enhance T cell-mediated immune function, yet the effectiveness of anti-PD-L1/PD-1 agents in enhancing natural killer (NK) cell’s function remains largely unknown. Susceptibilities of cisplatin-resistant A549CisR and H157CisR cells vs. parental cells to the cytotoxic action of NK cells were examined. We found cisplatin-resistant cells more resistant to NK cell cytotoxicity than parental cells. There were constitutively higher expressions of PD-L1 in A549CisR and H157CisR cells than in parental cells in vitro, as well as in H157CisR cell-derived tumors than H157P cell-derived tumors. In contrast, we observed that the expression of PD-1 in NK cells was induced after co-culture with cisplatin-resistant cells. We also observed increased susceptibility of cisplatin-resistant cells to NK cell cytotoxicity when neutralizing antibody of PD-1 or PD-L1 was added. Further, we found that the NK group 2, member D (NKG2D) ligand levels were lower in A549CisR and H157CisR cells than in parental cells. Meanwhile, we discovered that the MEK/Erk signaling pathway played a significant role in this regulation, and the addition of a MEK/Erk pathway inhibitor significantly enhanced the PD-L1 Ab effect in enhancing NK cell cytotoxicity to cisplatin-resistant cells.

// Ming Jing Shen 1, 2 , Li Jun Xu 1, 2 , Li Yang 1 , Ying Tsai 1 , Peter C. Keng 1 , Yongbing Chen 2 , Soo Ok Lee 1 and Yuhchyau Chen 1 1 Department of Radiation Oncology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA 2 Department of Cardiothoracic Surgery, The Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215004, P.R. China Correspondence to: Yuhchyau Chen, email: Yuhchyau_Chen@urmc.rochester.edu Soo Ok Lee, email: Soook_Lee@urmc.rochester.edu Keywords: PD-L1, NKG2D, NK cytotoxicity, MEK/Erk, radioresistant lung cancer Received: April 12, 2017 Accepted: June 28, 2017 Published: July 12, 2017 ABSTRACT We investigated whether radiation influences the susceptibility of non-small cell lung cancer (NSCLC) cells to NK cell mediated cytotoxicity. We found radiation treatment increased expression of programmed cell death ligand 1 (PD-L1), but decreased NK group 2, member D (NKG2D) ligand expressions in A549 and H157 NSCLC cells. Both types of changes would have protected tumor cells from the cytotoxic action of NK cells. Consistently, we detected similar alteration in these molecules in radioresistant A549R26-1 and H157R24-1 subline cells. Higher PD-L1 level was also observed in tumors of A549R26-1 cell-derived xenografts than tumors of parental A549 (A549P) cell-derived xenografts. Accordingly, we found radioresistant cells were more resistant to the cytotoxic action of NK cells than parental cells, and such resistance was decreased when neutralizing antibody (Ab) of PD-L1 was added to the radioresistant cell/NK cell co-cultures. In mechanism studies, we found that IL-6-MEK/Erk signaling contributed most significantly to the up-regulation of PD-L1/down-regulation of NKG2D ligands in radioresistant cells. The addition of the MEK/Erk inhibitor increased the susceptibility of A549R26-1 and H157R24-1 cells to NK-cell cytotoxicity while no significant effect was observed in parental cells. Moreover, we detected enhanced NK-cell cytotoxicity to radioresistant cells when PD-L1 Ab and MEK/Erk inhibitor were added together to co-cultures of tumor/NK cells compared to when PD-L1 Ab was used alone. We suggest that combined use of PD-L1 Ab and MEK/Erk inhibitor may offer better therapeutic benefits than PD-L1 Ab alone to treat NSCLC patients who are receiving radiotherapy or who are at the radioresistant stage.

In this study, in order to investigate the effects of increased macrophage infiltration to radioresistant lung tumors in regulating natural killer (NK) cell-mediated immunity, we examined whether the treatment of radioresistant cells with conditioned medium (CM) from phorbol myristate acetate (PMA)/interleukin (IL)-4 treated THP-1 cells (used as a tumor-associated macrophage source) leads to the development of the additional resistance of tumor cells to NK cell cytotoxicity. We found that the susceptibility of THP-1 CM-treated radioresistant cells to NK cell cytotoxicity was decreased compared to the non-treated cells. In addition, it was found that such a decreased susceptibility was associated with increased programmed death receptor ligand 1 (PD-L1) and decreased natural killer group 2D (NKG2D) ligand levels in tumor cells. We further discovered that the THP-1 cells secreted a high level of IL-6, and that blocking IL-6 action by the addition of a neutralizing antibody (Ab) for IL-6 into the THP-1 CM decreased the resistance of THP-1 CM-treated radioresistant cells to NK cell cytotoxicity. Moreover, we discovered that MEK/Erk was the most critical IL-6 downstream signaling pathway in triggering the THP-1 CM effect; thus, the addition of MEK/Erk inhibitor to THP-1 CM enhanced the susceptibility of the THP-1 CM-treated radioresistant cells to NK cell cytotoxicity. On the whole, the findings of this study suggest the existence of a malignant loop characterized by increased macrophage infiltration into radioresistant cells which, in turn, promotes the development of the additional resistance of these cells to NK cell cytotoxicity.

We observed cancer stem cell (CSC) population increase in radioresistant LNCaP (LNCaPR18) and C4-2 (C4-2R26) prostate cancer (PCa) cells compared with respective parental cells. Since the CD44 level increase was most significant in radioresistant PCa cells compared with parental cells among CSC markers tested, we isolated the CD44+ population from LNCaP/LNCaPR18 and C4-2/C4-2R26 cell sets via the immunomagnetic separation method and used them as CSC sources. We detected lower AR level, but higher glucocorticoid receptor (GR) level in CD44+ CSCs than CD44- non-CSCs. Higher GR level in CD44+ CSCs than CD44- cells was also detected when cells were isolated from mouse tumor tissues of LNCaPR18 cell and C4-2R26 cell-derived human xenografts and grown in culture. We then found blocking the GR signaling by adding the anti-GR agent mifepristone into the cell culture inhibited the CD44+ CSC growth while the addition of the anti-AR agent enzalutamide enhanced the CSC growth. In xenograft mouse studies in which tumors were developed from the injection of CD44+ CSCs of LNCaPR18 or C4-2R26 cell lines, retarded tumor growth in mifepristone-injected mice was observed compared with vehicle-treated mice. We next discovered the GR regulation of Wnt/β-catenin signaling pathway. We further found that the serum/glucocorticoid regulated kinase 1 (SGK1) is the GR downstream molecule that mediates Wnt/β-catenin signaling activation. Therefore, inhibition of either SGK1 or Wnt/β-catenin signaling impaired the in vitro CD44+ CSC growth. From these results, we suggest that blocking GR signaling or its downstream SGK1-Wnt/β-catenin signaling axis may suppress the radiation-induced CSC increase in PCa. KEY MESSAGES: Higher CSC population exists in radioresistant PCa cells than parental cells. Higher GR levels (and lower AR level) in CD44+ CSCs than CD44- non-CSCs. Use of anti-GR agent blocked the growth of CD44+ CSCs in in vitro/in vivo tests. GR downstream SGK1-Wnt/β-catenin signaling axis mediates the CSC increase. Targeting this signaling axis may enhance the radiotherapy efficacy in treating PCa.

// Li Yang 1 , Fuquan Zhang 1 , Xin Wang 1 , Ying Tsai 1 , Kuang-Hsiang Chuang 1 , Peter C. Keng 1 , Soo Ok Lee 1 , Yuhchyau Chen 1 1 Department of Radiation Oncology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA Correspondence to: Yuhchyau Chen, email: Yuhchyau_Chen@urmc.rochester.edu Soo Ok Lee, email: Soook_Lee@urmc.rochester.edu Keywords: non-small cell lung cancer, EMT, cisplatin-resistance, fatty acid synthase (FASN), TGF-β1 Received: May 04, 2016 Accepted: July 11, 2016 Published: July 25, 2016 ABSTRACT Cisplatin-resistant A549CisR and H157CisR cell lines were developed by treating parental A549 (A549P) and H157 (H157P) cells. These cisplatin-resistant cells showed slight growth retardation, but exhibited higher epithelial-mesenchymal transition (EMT) and increased metastatic potential compared to parental cells. We observed a highly up-regulated fatty acid synthase (FASN) level in A549CisR and H157CisR cells compared to parental cells and the up-regulation of FASN was also detected in A549P and H157P cells after short time treatment with cisplatin, suggesting that the high level of FASN in cisplatin-resistant cells may be from the accumulated cellular responses during cisplatin-resistance developmental process. We next investigated whether the inhibition of FASN by using a specific FASN inhibitor, cerulenin, can influence growth and EMT/metastatic potential of A549CisR and H157CisR cells. There was slight growth inhibition, but significantly reduced EMT/metastatic potential in cisplatin-resistant cells upon inhibitor treatment. The in vitro result was further investigated in orthotopic xenograft mouse models established with luciferase-tagged H157P and H157CisR cells. Mice were injected with cerulenin or vehicle after tumors were developed. No significant tumor regression was detected at the end of cerulenin treatment, but IHC staining showed higher expression of EMT/metastasis markers in H157CisR cell-derived tumors than H157P cell-derived tumors, and showed dramatic reduction of these markers in tumor tissues of cerulenin-treated mice, confirming the in vitro results. In mechanism dissection studies, we revealed the existence of the FASN-TGF-β1-FASN positive loop in A549CisR and H157CisR cells, but not in parental cells, which is believed to augment the FASN function in cisplatin-resistant cells.

Cisplatin-resistant A549 and H157 (A549CisR and H157CisR) non-small cell lung cancer cells show increased stemness of cancer stem cells (CSCs) compared to their parental cells. We investigated whether interleukin-6 (IL-6) signaling contributes to this increased stemness in cisplatin-resistant cells. When A549CisR and H157CisR cells were treated with neutralizing IL-6 antibody, decreased cisplatin resistance was observed, whereas IL-6 treatment of parental cells resulted in increased cisplatin resistance. Expression of the CSC markers was significantly upregulated in IL-6-expressing scramble cells (in vitro) and scramble cell-derived tumor tissues (in vivo) after cisplatin treatment, but not in IL-6 knocked down (IL-6si) (in vitro) cells and in IL-6si cell-derived tumor tissues (in vivo), suggesting the importance of IL-6 signaling in triggering increased stemness during cisplatin resistance development. Hypoxia inducible factors (HIFs) were upregulated by IL-6 and responsible for the increased CSC stemness on cisplatin treatment. Mechanism dissection studies found that upregulation of HIFs by IL-6 was through transcriptional control and inhibition of HIF degradation. Treatment of HIF inhibitor (FM19G11) abolished the upregulation of CSC markers and increased sphere formations in IL-6 expressing cells on cisplatin treatment. In all, IL-6-mediated HIF upregulation is important in increasing stemness during cisplatin resistance development, and we suggest that the strategies of inhibiting IL-6 signaling or its downstream HIF molecules can be used as future therapeutic approaches to target CSCs after cisplatin treatment for lung cancer.

With the rapid and exponential growth of Internet use worldwide, online learning has become one of the most widely used learning paradigms in the education environment. Yet despite the rapidly increasing cultural diversity of online learners, few studies have investigated the effectiveness of cross-cultural Online Learning Systems (OLS) using a suitable measurement to answer the question, “Do culturally different learners perceive OLS effectiveness differently?” The aim of this comparative study was to gain a better understanding of OLS effectiveness in a non-western culture by comparing cultural dimensions and learners’ perceived effectiveness of OLS (across the four pillars: technology/support, course, professor, & learner) among American and Malaysian learners. Results show that American learners perceived a slightly higher OLS effectiveness in terms of the course and professor pillars than Malaysian learners. In other words, the findings indicated that the cultural dimensions distinguishing American and Malaysian learners influenced those two groups’ perceived effectiveness of the course and professor pillars of the OLS.

Cisplatin-resistant (A549CisR and H292CisR) and radioresistant (A549R26 and H292R22) sub-line non-small cell lung cancer (NSCLC) cells were developed in our lab by long term treatment of parental cells with cisplatin or radiation. Our data showed no cross-resistance between these two sets of cell lines, indicating that molecular mechanisms of developing each resistance may be different. Using these sub-line cells, we sought to reveal the most significantly up-regulated molecules in cisplatin-resistant and radioresistant lung cancer cells, compared with parental cells. In qPCR analyses of screening DNA repair and cell survival-associated molecules, we identified NFκB and TNFα as the most significantly up-regulated molecules in cisplatin-resistant and radioresistant lung cancer cells, respectively, compared with parental cells. Western blot analysis of parental vs. resistant cells and the IHC staining of tumor tissues of A549P, A549CisR, and A549R26 cell-derived xenografts in mice confirmed such results. Next, studies using specific inhibitors of NFκB and TNFα and experiments using NFκB and TNFα-knocked down cells showed that inhibition or knockdown of NFκB overcame cisplatin-resistance, while inhibition or knockdown of TNFα increased radiosensitivity of radioresistant lung cancer cells. Therefore, these two molecules may be used as markers of the prognosis/diagnosis of individual resistance development during lung cancer treatment.

Radiation treatment induces neuroendocrine differentiation (NED) in non-small cell lung cancer (NSCLC) A549 and H157 cells, so higher NE-like features in radioresistant A549 (A549R26-1) and H157 (H157R24-1) cells are observed than in parental cells. We detected higher NED marker expressions in A549R26-1 cell-derived tumors than in A549 cell-derived tumors. In mechanism studies, we found that NED induction in A549R26-1 and H157R24-1 cells was accompanied by increased intracellular cAMP and IL-6 levels. Treatment of radioresistant lung cancer cells with the inhibitor (SQ22536) of adenylate cyclase (AC) which is the enzyme responsible for the cAMP production, or the neutralizing antibody (Ab) of IL-6, resulted in decreased NE-like features in radioresistant lung cancer cells. In addition, we found MEK/Erk is the signaling pathway that triggers the cAMP- and IL-6-mediated NED induction in radioresistant lung cancer cells. Also, we found that MEK/Erk signaling pathway inhibition decreased NED in radioresistant cells. Radioresistant lung cancer cells exhibiting high NE-like features also showed higher radioresistance and higher metastatic potential than parental cells. When we inhibited cAMP-, or IL-6-mediated pathways, or the downstream MEK/Erk signaling pathway, radiosensitivity of radioresistant lung cancer cells was significantly increased and their metastatic potential was significantly reduced. In in vivo mouse studies, reducing NED by treating mice with the MEK/Erk inhibitor increased radiosensitivity. Immunohistochemical staining of tumor tissues lowered expressions of the NED/epithelial-mesenchymal transition (EMT)/metastatic markers when mice were treated with the MEK/Erk inhibitor.

Development of cisplatin-resistance is an obstacle in non-small cell lung cancer (NSCLC) therapeutics. To investigate which molecules are associated with cisplatin-resistance, we analyzed expression profiles of several DNA repair and anti-apoptosis associated molecules in parental (A549P and H157P) and cisplatin-resistant (A549CisR and H157CisR) NSCLC cells. We detected constitutively upregulated nuclear ATM and cytosolic Mcl-1 molcules in cisplatin-resistant cells compared with parental cells. Increased levels of phosphorylated ATM (p-ATM) and its downstream molecules, CHK2, p-CHK2, p-53, and p-p53 were also detected in cisplatin-resistant cells, suggesting an activation of ATM signaling in these cells. Upon inhibition of ATM and Mcl-1 expression/activity using specific inhibitors of ATM and/or Mcl-1, we found significantly enhanced cisplatin-cytotoxicity and increased apoptosis of A549CisR cells after cisplatin treatment. Several A549CisR-derived cell lines, including ATM knocked down (A549CisR-siATM), Mcl-1 knocked down (A549CisR-shMcl1), ATM/Mcl-1 double knocked down (A549CisR-siATM/shMcl1) as well as scramble control (A549CisR-sc), were then developed. Higher cisplatin-cytotoxicity and increased apoptosis were observed in A549CisR-siATM, A549CisR-shMcl1, and A549CisR-siATM/shMcl1 cells compared with A549CisR-sc cells, and the most significant effect was shown in A549CisR-siATM/shMcl1 cells. In in vivo mice studies using subcutaneous xenograft mouse models developed with A549CisR-sc and A549CisR-siATM/shMcl1 cells, significant tumor regression in A549CisR-siATM/shMcl1 cells-derived xenografts was observed after cisplatin injection, but not in A549CisR-sc cells-derived xenografts. Finally, inhibitor studies revealed activation of Erk signaling pathway was most important in upregulation of ATM and Mcl-1 molcules in cisplatin-resistant cells. These studies suggest that simultaneous blocking of ATM/Mcl-1 molcules or downstream Erk signaling may recover the cisplatin-resistance of lung cancer.

Radiotherapy is effective in reducing primary tumors, however, it may enhance macrophage infiltration to tumor sites, accelerating tumor progression in several ways. We investigated whether radiation can increase macrophage infiltration into non-small cell lung carcinoma (NSCLC) cells. Analysis of in vitro macrophage (differentiated THP-1 cells) migration to either nonirradiated or irradiated tumor cells showed increased migration to the irradiated tumor cells. Because the IL-6 levels in A549 and H157 cells were significantly increased after irradiation, we then investigated whether this increased IL-6 level contributes to radiation-induced macrophage migration. Radiation-induced macrophage infiltration was reduced when IL-6 was knocked down in tumor cells, indicating a positive IL-6 role in this process. To validate this in vitro result, an orthotopic mouse model was developed using a luciferase-tagged H157siIL-6/scramble control (sc) cell set. After tumors developed, the lungs were irradiated, and infiltration of endogenous macrophages and tail-vein injected fluorescent macrophages to tumor sites was investigated. In both groups, increased macrophage infiltration was observed in H157sc cell-derived xenografts compared to H157siIL-6 cell-derived xenografts, confirming the positive IL-6 role in the radiation-induced macrophage infiltration process. In mechanistic dissection studies, radiation-induced up-regulation of CCL2 and CCL5 by IL-6 was detected, and blocking the action of CCL2/CCL5 molecules significantly reduced the number of migrated macrophages to tumor cells after irradiation. These results demonstrate that targeting the IL-6 signaling or CCL2/CCL5 molecules in combination with conventional radiotherapy potentially blocks undesired radiation-induced macrophage infiltration.

Osteoclasts (OC) are bone-resorbing, multinucleated cells that are generated via fusion of OC precursors (OCP). The frequency of OCP is elevated in patients with erosive inflammatory arthritis and metabolic bone diseases. Although many cytokines and cell surface receptors are known to participate in osteoclastogenesis, the molecular mechanisms underlying the regulation of this cellular transformation are poorly understood. Herein, we focused our studies on the dendritic cell-specific transmembrane protein (DC-STAMP), a seven-pass transmembrane receptor-like protein known to be essential for cell-to-cell fusion during osteoclastogenesis. We identified an immunoreceptor tyrosine-based inhibitory motif (ITIM) in the cytoplasmic tail of DC-STAMP, and developed an anti-DC-STAMP monoclonal antibody 1A2 that detected DC-STAMP expression on human tumor giant cells, blocked OC formation in vitro, and distinguished four patterns of human PBMC with a positive correlation to OC potential. In freshly isolated monocytes, DC-STAMPhigh cells produced a higher number of OC in culture than DC-STAMPlow cells and the surface expression of DC-STAMP gradually declined during osteoclastogenesis. Importantly, we showed that DC-STAMP is phosphorylated on its tyrosine residues and physically interacts with SHP-1 and CD16, an SH2-domain-containing tyrosine phosphatase and an ITAM-associated protein, respectively. Taken together, these data show that DC-STAMP is a potential OCP biomarker in inflammatory arthritis. Moreover, in addition to its effect on cell fusion, DC-STAMP dynamically regulates cell signaling during osteoclastogenesis. © 2012 American Society for Bone and Mineral Research

Background: One-third of US population is obese. The mortality of obese prostate cancer (PCa) patients is higher than non-obese patients, thus studying molecular mechanism of how obesity affects PCa progression has clinical relevance. The periprostatic adipose tissue adjacent to the prostate is considered a driving force of disease progression and adipocytes are the main cell population in adipose tissues. The paracrine role of adipocytes in PCa progression has been emphasized, but its implication in modulating immune reactions remains unknown. We investigated the role of adipocytes in the surveillance of castration-resistant PCa (CRPC) cells to immune actions. Especially we investigated the role of adipocytes in affecting tumor cell susceptibility to cytotoxic action of natural killer (NK) cells, as the strategy of improving the NK cell-mediated immunity is emerging as an immunotherapeutic option. Methods: Using primary NK cells as the NK cell source, NK cell cytotoxicities to CRPC cells, either control media treated or adipocyte-conditioned media (CM) treated, were tested in lactate dehydrogenase (LDH) release-based assays. The levels of programmed death receptor ligand (PD-L1) and NK group 2D (NKG2D) ligands in adipocyte CM-treated CRPC cells were analyzed in qPCR analyses. Effects of blocking adipocyte action on altering PD-L1/NKG2D ligand levels and the susceptibility of CRPC cells to NK cell cytotoxicity were investigated. Results: We found NK cell cytotoxicity to CRPC cells decreased when tumor cells were treated with adipocyte CM, and was associated with PD-L1 (up-regulation) and NKG2D ligand level (down-regulation) alterations. Further, we discovered that the JAK/Stat3 signaling pathway was activated by adipocyte CM. Two adipokine molecules, IL-6 and leptin, were shown to be important in the activation of the JAK/Stat3 signaling to modulate the PD-L1/NKG2D ligand level alterations in CRPC cells. Consequently, adding inhibitors of JAK/Stat3 signaling or neutralizing antibodies of IL-6 or leptin increased the susceptibility of CRPC cells to NK cell cytotoxic action. Conclusions and Impact: Results from our study showed the influence of adipocytes on tumor cells and resulted in reducing the susceptibility to NK cell-mediated antitumor immune function. This may be one of ways that adipocytes trigger CRPC cells to be more aggressive and out of immune surveillance control. Our study results showed that blocking the adipocyte effect by inhibiting the IL-6/leptin-JAK/Stat3 signaling axis enhanced the NK cell mediated immunity to CRPC cells. We suggest that this strategy can be applied to the development of future immune therapeutics to treat obese PCa patients. Citation Format: Lijun Xu, Mingjing Shen, Xiaodong Chen, Rongying Zhu, Dong-rong Yang, Ying Tsai, Peter Keng, Yuhchyau Chen, Soo Ok Lee. Adipocytes affect castration-resistant prostate cancer cells in resistance to cytotoxic action of NK cells through alterations of pd-l1/nkg2d ligand levels [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3147.

Cofilin, a ubiquitously expressed actin binding protein, is responsible for the formation of the actin cytoskeleton and is indispensable for cell cycle control. However, the association between cofilin expression and the cell cycle remains to be elucidated. In this study, we found that the expression level of cofilin upregulated in G(1) phase-arrested confluent cells, while knockdown of cofilin expression by small interference RNA (siRNA) in these cells led to a reduction in the population of G(1) cells. To investigate the role of cofilin in the control of G(1) phase progression, a tet-on gene expression system was introduced to overexpress different concentrations of cofilin in cells. The results showed that G(1) phase progression was blocked following induction of exogenous cofilin. A survey of the cell cycle proteins controlling the G(1) phase progression revealed that the cyclin-dependent kinase inhibitor (CKI) p27(kip1) was the primary molecule induced by overexpressed cofilin in a time and dose dependent manner. Upregulated p27(kip1) repressed phosphorylation of the retinoblastoma protein (Rb) mediated by cyclin D1/CDK4 activity. Conversely, siRNA against p27(kip1) expression in the cofilin overexpressing cells released the G(1) phase arrest. Furthermore, we found that overexpression of cofilin led to induction of p27(kip1) gene promoter transactivation using luciferase reporter gene assay. This effect was associated with increase of p27(kip1) mRNA transiently. In addition, inhibition of threonine-187 phosphorylation of p27(kip1) protein for ubiquitinyl-proteasomal mediated degradation was also involved in upregulation of p27(kip1). These data suggest that cofilin expression and its regulation of p27(kip1) expression is important for the control of G(1) phase progression.

Purpose Current biodosimetric techniques for determining radiation exposure have inherent delays, as well as quantitation and interpretation limitations. We have identified a new technique with the advantage of directly measuring circulating DNA by amplifying inter-B1 regions in the mouse genome, providing a sensitive method for quantitating plasma DNA. Methods and Materials Real-time quantitative polymerase chain reaction (PCR) was used to detect levels of DNA by amplifying inter-B1 genomic DNA in plasma samples collected at 0–48 h from mice receiving 0–10 Gy total- or partial-body irradiation ( 137 Cs γ-ray source at ≈1.86 Gy/min; homogeneity: ± 6.5%). Results The correlation coefficient between DNA levels and the threshold cycle value (C T ) was 0.996, and the average recoveries of DNA in the assay were 87%. This assay revealed that when BALB/c mice were exposed to 10 Gy total-body irradiation (TBI), plasma DNA levels gradually increased beginning at 3 h after irradiation, peaked at 9 h, and returned to baseline within 48 h. Increased plasma DNA levels were also detected following upper-torso or lower-torso partial-body irradiation; however, TBI approximately doubled those plasma DNA levels at the same radiation dose. This technique therefore reflects total body cell damage. The advantages of this assay are that DNA extraction is not required, the assay is highly sensitive (0.002 ng), and results can be obtained within 2.5 h after collection of plasma samples. Conclusions A radiation dose–dependent increase of plasma DNA was observed in the dose range from 2 to 10 Gy, suggesting that plasma DNA may be a useful radiation biomarker and adjunct to existing cell-based assays.

Neutrophils, the major phagocytes that form the first line of cell-mediated defense against microbial infection, are produced in the bone marrow and released into the circulation in response to granulocyte-colony stimulating factor (G-CSF). Here, we report that androgen receptor knockout (ARKO) mice are neutropenic and susceptible to acute bacterial infection, whereas castration only results in moderate neutrophil reduction in mice and humans. Androgen supplement can restore neutrophil counts via stabilizing AR in castrated mice, but not in ARKO and testicular feminization mutant (Tfm) mice. Our results show that deletion of the AR gene does not influence myeloid lineage commitment, but significantly reduces the proliferative activity of neutrophil precursors and retards neutrophil maturation. CXCR2-dependent migration is also decreased in ARKO neutrophils as compared with wild-type controls. G-CSF is unable to delay apoptosis in ARKO neutrophils, and ARKO mice show a poor granulopoietic response to exogenous G-CSF injection. In addition, AR can restore G-CSF–dependent granulocytic differentiation upon transduction into ARKO progenitors. We further found that AR augments G-CSF signaling by activating extracellular signal-regulated kinase 1/2 and also by sustaining Stat3 activity via diminishing the inhibitory binding of PIAS3 to Stat3. Collectively, our findings demonstrate an essential role for AR in granulopoiesis and host defense against microbial infection.

Purpose Poor local disease control remains a major obstacle for inoperable non-small cell lung cancer (NSCLC) after radiotherapy. We previously reported results of a phase I/II clinical study based on preclinical investigations of paclitaxel radiation interactions for inoperable locally advanced NSCLC, which yielded remarkable local tumor responses and durable in-field tumor control using schedule-dependent low-dose paclitaxel for radiosensitization. Given our unique results, we analyzed the tumor response kinetics and conducted a statistical modeling of tumor response to characterize this regimen. Methods and Materials A total of 104 chest CT scans from 27 patients treated in the clinical trial were evaluated. Tumor volumes were calculated by three-dimensional measurements of pretreatment and serial post-therapy CT scans. A nonlinear mixed effects model was used to model response kinetics. Results The average tumor volume reduction at 1 month post-therapy was 69.9 ± 22.6% (standard deviation), and was 80.6 ± 17.9% at the last follow-up. The nonlinear mixed effects model predicts that tumor volume will ultimately shrink by at least 75% for more than 75% of patients treated by this regimen. The model also suggests that maximum shrinkage is reached within 2 months after treatment. Conclusion Tumor volume response kinetics revealed a rapid shrinkage of gross tumors using schedule-dependent pulsed low-dose paclitaxel radiosensitization. This is contrary to the protracted tumor regression process observed in radiation alone or other chemoradiation combinations. Statistical modeling may prove useful in characterizing and comparing different therapeutic regimens.

Genotoxic stress activates the phosphatidylinositol 3-kinase like kinases (PIKKs) that phosphorylate proteins involved in cell cycle arrest, DNA repair, and apoptosis. Previous work showed that the PIKK ataxia telangiectasia mutated (ATM) but not ATR (ATM and Rad3-related) phosphorylates p53 (Ser15) during hyperoxia, a model of prolonged oxidative stress and DNA damage. Here, we show hSMG-1 is responsible for the rapid and early phosphorylation of p53 (Ser15) and that ATM helps maintain phosphorylation after 24 hours. Despite reduced p53 phosphorylation and abundance in cells depleted of hSMG-1 or ATM, levels of the p53 target p21 were still elevated and the G1 checkpoint remained intact. Conditional over-expression of p21 in p53-deficient cells revealed that hyperoxia also stimulates wortmannin-sensitive degradation of p21. SiRNA depletion of hSMG-1 or ATM restored p21 stability and the G1 checkpoint during hyperoxia. These findings establish hSMG-1 as a proximal regulator of DNA damage signaling and reveal that the G1 checkpoint is tightly regulated during prolonged oxidative stress by both PIKK-dependent synthesis and proteolysis of p21.

The tumor suppressor protein p53 activates growth arrest and proapoptotic genes in response to DNA damage. It is known that negative feedback by p21(Cip1/Waf1/Sdi1) represses p53-dependent transactivation of PUMA. The current study investigates PUMA feedback on p53 during oxidative stress from hyperoxia and the subsequent effects on cell survival mediated through p21 and Bcl-X(L). Deletion of PUMA in HCT116 colon carcinoma cells increased levels of p53 and p21, resulting in a larger G(1) population during hyperoxia. P21-dependent increase in Bcl-X(L) levels protected PUMA-deficient cells against hyperoxic cell death. Bax and Bak were both able to promote hyperoxic cell death. Bcl-X(L) protection against hyperoxic death was lost in cells lacking Bax, not PUMA, suggesting that Bcl-X(L) acts to inhibit Bax-dependent death. These results indicate that PUMA exerts a negative feedback on p53 and p21, leading to p21-dependent growth suppressive and survival changes. Enhanced survival was associated with increased Bcl-X(L) to block Bax activated cell death during oxidative stress.

Prolonged exposure to hyperoxia inhibits cell proliferation in G1via increased expression of p21. While p21 inhibits proliferating cell nuclear antigen (PCNA)-dependent DNA synthesis, it can also directly lower PCNA abundance; however, it is unclear whether loss of PCNA contributes to growth arrest. Here, we investigate how PCNA loss affects ability of p21 to exert G1growth arrest of lung epithelial cells exposed to hyperoxia. In A549 cells that express p21 and growth arrest in G1during hyperoxia, small interfering RNA (siRNA) knockdown of p21 led to G1checkpoint bypass, increased cell death, and restoration of PCNA expression. Conditional overexpression of the PCNA binding domain of p21 in H1299 cells that do not normally express p21, or exposure to hyperoxia, caused a time-dependent loss of PCNA. Titrating PCNA levels using siRNA to approximate the low amount observed in cells expressing p21 resulted in S phase arrest. While lowering PCNA by itself caused S phase arrest, the combination of hyperoxia and siRNA against PCNA dramatically reduced PCNA abundance resulting in G1arrest. G1growth arrest was markedly enhanced upon the addition of p21 to these cells. Our findings suggest a model in which reducing expression of the abundant protein PCNA allows the less abundant protein p21 to be more effective at suppressing the processivity functions of remaining PCNA, thereby fully exerting the G1checkpoint. Given that high p21 expression is often associated with lower PCNA abundance, our findings are suggestive of a global growth inhibitory mechanism involving p21-mediated PCNA suppression.

Background Local tumor control by standard fractionated radiotherapy (RT) remains poor because of tumor resistance to radiation (radioresistance). It has been suggested that cancer stem cells (CSCs) are more radioresistant than non-CSCs. In previous studies, we have shown IL-6 promotes self-renewal of CD133+ CSC-like cells. In this study, we investigated whether IL-6 plays roles not only in promoting self-renewal of CD133+ cells after radiation, but also in conferring radioresistance of CD133+ cells in NSCLC. Materials and methods To compare radiation sensitivity of CSCs and non-CSCs, CD133+ CSC-like and CD133- cell populations were isolated from two NSCLC cell lines, A549 and H157, by immunomagnetic separation and their sensitivities to ionizing radiation were investigated using the clonogenic survival assay. To further study the IL-6 effect on the radiosensitivity of CD133+ CSC-like cells, CD133+ cells were isolated from A549IL-6si/sc and H157IL-6si/sc cells whose intracellular IL-6 levels were manipulated via the lentiviral transduction with IL-6siRNA. Post-irradiation DNA damage was analyzed by γ-H2AX staining and Comet assay. Molecular mechanisms by which IL-6 regulates the molecules associated with DNA repair and anti-apoptosis after radiation were analyzed by Western blot and immunofluoresecence (IF) staining analyses. Results NSCLC CD133+ CSC-like cells were enriched upon radiation. Survival of NSCLC CD133+ cells after radiation was higher than that of CD133- cells. Survival of IL-6 expressing NSC LC CD133+ cells (sc) was higher than that of IL-6 knocked-down cells (IL-6si) after radiation. IL-6 played a role in protecting NSCLC CD133+ cells from radiation-induced DNA damage and apoptosis. Conclusions IL-6 signaling promotes DNA repair while protecting CD133+ CSC-like cells from apoptotic death after radiation for lung cancer. A combined therapy of radiation and agents that inhibit IL-6 signaling (or its downstream signaling) is suggested to reduce CSC-mediated radioresistance in lung cancer.

Cisplatin-based chemotherapy is currently the most effective treatment regimen for non-small cell lung cancer (NSCLC), but eventually tumor resistance develops which limits its success. The potential implication of IL-6 signaling in the cisplatin resistance of NSCLC was explored by testing whether NSCLC cells with different levels of intracellular IL-6 show different responses to the cytotoxic treatment of cisplatin. When the cisplatin cytotoxicity of the IL-6 knocked down human NSCLC cells (A549IL-6si and H157IL-6si) were compared with their corresponding scramble control cells (A549sc and H157sc), higher cisplatin cytotoxicity was found in IL-6 si cells than sc cells. Subcutaneous xenograft mouse models were developed using a pair of A549sc and A549IL-6si cells. When the tumor grew to about 400 mm2, mice were treated with cisplatin and tumor regression was monitored. Higher tumor regression was detected in the A549IL-6si xenografts compared to A549sc xenografts following cisplatin treatment. Immunostaining study results from tumor tissues also supported this finding. Expression of anti-apoptotic proteins Bcl-2 and Mcl-1 and DNA repair associated molecules ATM, CHK1, TP73, p53, and ERCC1 were significantly up regulated in cisplatin-treated A549sc and H157sc cells, but no increase was detected in A549IL-6si and H157IL-6si cells. Further inhibitor studies revealed that up regulation of these molecules by IL-6 may be through activation of IL-6 downstream signaling pathways like Akt, MAPK, Stat3, and Erk. These results provide potential for combining cisplatin and inhibitors of IL-6 signaling or its downstream signaling pathway as a future therapeutic approach in preventing development of cisplatin resistant NSCLC tumors.

We developed a simple, rapid and quantitative assay using the fluorescent probe PicoGreen to measure the concentration of ionizing radiation-induced double-stranded DNA (dsDNA) in mouse plasma, and we correlated this concentration with the radiation dose. With 70 μl of blood obtained by fingerstick, this 30 min assay reduces protein interference without extending sample processing time. Plasma from nonirradiated mice (BALB/c and NIH Swiss) was pooled, diluted and spiked with dsDNA to establish sensitivity and reproducibility of the assay to quantify plasma dsDNA. The assay was then used to directly quantify dsDNA in plasma at 0-48 h after mice received 0-10 Gy total-body irradiation (TBI). There are three optimal conditions for this assay: 1:10 dilution of plasma in water; 1:200 dilution of PicoGreen reagent in water; and calibration of radiation-induced dsDNA concentration through a standard addition method using serial spiking of samples with genomic dsDNA. Using the internal standard calibration curve of the spiked samples method, the signal developed within 5 min, exhibiting a linear signal (r(2) = 0.997). The radiation-induced elevation of plasma DNA in mice started at 1-3 h, peaked at 9 h and gradually returned to baseline at 24 h after TBI (6 Gy). DNA levels in plasma collected from mice 9 h after 0-10 Gy TBI correlated strongly with dose (r(2) = 0.991 and 0.947 for BALB/c and NIH Swiss, respectively). Using the PicoGreen assay, we observed a radiation dose-dependent response in extracellular plasma DNA 9 h after irradiation with an assay time ≤ 30 min.

Osteoclasts are essential cells for bone erosion in inflammatory arthritis and are derived from cells in the myeloid lineage. Recently, we reported that tumor necrosis factor-alpha (TNFalpha) increases the blood osteoclast precursor (OCP) numbers in arthritic patients and animals, which are reduced by anti-TNF therapy, implying that circulating OCPs may have an important role in the pathogenesis of erosive arthritis. The aim of this study is to investigate the mechanism by which TNFalpha induces this increase in OCP frequency. We found that TNFalpha stimulated cell division and conversion of CD11b+/Gr-1-/lo/c-Fms- to CD11b+/Gr-1-/lo/c-Fms+ cells, which was not blocked by neutralizing macrophage colony-stimulating factor (M-CSF) antibody. Ex vivo analysis of monocytes demonstrated the following: (i) blood CD11b+/Gr-1-/lo but not CD11b-/Gr-1- cells give rise to osteoclasts when they were cultured with receptor activator NF-kappaB ligand and M-CSF; and (ii) TNF-transgenic mice have a significant increase in blood CD11b+/Gr-1-/lo cells and bone marrow proliferating CD11b+/Gr-1-/lo cells. Administration of TNFalpha to wild type mice induced bone marrow CD11b+/Gr-1-/lo cell proliferation, which was associated with an increase in CD11b+/Gr-1-/lo OCPs in the circulation. Thus, TNFalpha directly stimulates bone marrow OCP genesis by enhancing c-Fms expression. This results in progenitor cell proliferation and differentiation in response to M-CSF, leading to an enlargement of the marrow OCP pool. Increased marrow OCPs subsequently egress to the circulation, forming a basis for elevated OCP frequency. Therefore, the first step of TNF-induced osteoclastogenesis is at the level of OCP genesis in the bone marrow, which represents another layer of regulation to control erosive disease.

The Rho–LIM-kinase (LIMK) signaling pathway, believed to be involved in the regulation of tumor invasion, specifically regulates the activity of cofilin. However, it is unclear whether cofilin plays a pivotal role in tumor invasiveness. In this paper we show using a tet-on gene expression system that over-expression of cofilin inhibits the invasiveness of human lung cancer H1299 cells. Over-expressed cofilin disrupts the actin cytoskeleton at the leading edge of the cell and up-regulates p27kip1, which is known to be involved in regulating cell motility. Removal of cofilin over-expression normalizes the p27kip1 level and concomitantly restores the invasiveness of the cultured cells. These findings suggest that excessive cofilin production might prevent cancer cell invasion.

Cofilin is an actin-associated protein that belongs to the actin depolymerization factor/cofilin family and is important for regulation of actin dynamics. Cofilin can import actin monomers into the nucleus under certain stress conditions, however the biological effects of nuclear transport are unclear. In this study, we found that over-expression of cofilin led to increased radiation sensitivity in human non-small lung cancer H1299 cells. Cell survival as determined by colony forming assay showed that cells over-expressing cofilin were more sensitive to ionizing radiation (IR) than normal cells. To determine whether the DNA repair capacity was altered in cofilin over-expressing cells, comet assays were performed on irradiated cells. Repair of DNA damage caused by ionizing radiation was detected in cofilin over-expressing cells after 24 h of recovery. Consistent with this observation, the key components for repair of DNA double-strand breaks, including Rad51, Rad52, and Ku70/Ku80, were down-regulated in cofilin over-expressing cells after IR exposure. These findings suggest that cofilin can influence radiosensitivity by altering DNA repair capacity.

Arsenic is a well known toxicant and carcinogen that is also effective as a chemotherapeutic in the treatment of acute promyelocytic leukemia. Although its effects on humans are well documented, arsenic's mechanism of action is not well understood. Its ability to act as a carcinogen and as a chemotherapeutic seems paradoxical. However, cancer cell transformation and cancer cell destruction can both occur through perturbations of the cell cycle machinery, making cell cycle function a likely target of arsenic action. Arsenic has previously been shown to inhibit cancer cell cycle progression, but the targeted cell cycle phase has been debated. This study was designed to identify the cell cycle phase at which U937 cells are most sensitive to arsenite-induced growth inhibition. Centrifugal elutriation was used to divide asynchronous cell cultures into specific cell cycle phase-enriched fractions. These fractions were monitored for cell cycle phase progression in the presence and absence of sodium arsenite. We found an overall reduction in cell cycle progression rather than induction of arrest at one specific checkpoint. G(2)/M is the phase most sensitive to arsenite-induced apoptosis. However, arsenite profoundly affects U937 cell growth by increasing the length of time it takes cells to transit each phase of the cell cycle. Future study of cell cycle inhibition by arsenic should consider that the effect may not be mediated by the major cell cycle checkpoints. Arsenic's ability to inhibit growth in any cell cycle phase may increase its value as a chemotherapeutic used together with other, more phase-selective agents, such as camptothecin.

The toroidal Rad9-Rad1-Hus1 checkpoint complex (9-1-1) is structurally similar to the proliferating cell nuclear antigen (PCNA), which serves as a sliding clamp platform for DNA replication and repair. 9-1-1 has been characterized as a sensor of DNA damage that functions in concert with the checkpoint control proteins ATM and ATR. However, recent data suggest that the 9-1-1 complex and its individual Rad9 component serve different and multiple functions in cells by sensing DNA damage, stimulating apoptosis, and regulating gene transcription. Recently it was reported that 9-1-1 interacts with and/or stimulates components of the base excision repair (BER) pathway including the S. pombe MutY homolog (MYH), human polymerase beta (Polbeta), and flap endonuclease 1 (FEN1). Furthermore, preliminary results indicate a stimulation of DNA ligase I. In this review, the likely direct participation of 9-1-1 in DNA repair is discussed.

The ataxia telangiectasia mutated (ATM) and ATR (ATM and Rad3-related) protein kinases exert cell cycle delay, in part, by phosphorylating Checkpoint kinase (Chk) 1, Chk2, and p53. It is well established that ATR is activated following UV light-induced DNA damage such as pyrimidine dimers and the 6-(1,2)-dihydro-2-oxo-4-pyrimidinyl-5-methyl-2,4-(1H,3H)-pyrimidinediones, whereas ATM is activated in response to double strand DNA breaks. Here we clarify the activation of these kinases in cells exposed to IR, UV, and hyperoxia, a condition of chronic oxidative stress resulting in clastogenic DNA damage. Phosphorylation on Chk1(Ser-345), Chk2(Thr-68), and p53(Ser-15) following oxidative damage by IR involved both ATM and ATR. In response to ultraviolet radiation-induced stalled replication forks, phosphorylation on Chk1 and p53 required ATR, whereas Chk2 required ATM. Cells exposed to hyperoxia exhibited growth delay in G1, S, and G2 that was disrupted by wortmannin. Consistent with ATM or ATR activation, hyperoxia induced wortmannin-sensitive phosphorylation of Chk1, Chk2, and p53. By using ATM- and ATR-defective cells, phosphorylation on Chk1, Chk2, and p53 was found to be ATM-dependent, whereas ATR also contributed to Chk1 phosphorylation. These data reveal activated ATM and ATR exhibit selective substrate specificity in response to different genotoxic agents.

It is well established that hyperoxia injures and kills alveolar endothelial and type I epithelial cells of the lung. Although type II epithelial cells remain morphologically intact, it remains unclear whether they are also damaged. DNA integrity was investigated in adult mice whose type II cells were identified by their endogenous expression of pro-surfactant protein C or transgenic expression of enhanced green fluorescent protein. In mice exposed to room air, punctate perinuclear 8-oxoguanine staining was detected in ∼4% of all alveolar cells and in 30% of type II cells. After 48 or 72 h of hyperoxia, 8-oxoguanine was detected in 11% of all alveolar cells and in >60% of type II cells. 8-Oxoguanine colocalized by confocal microscopy with the mitochondrial transmembrane protein cytochrome oxidase subunit 1. Type II cells isolated from hyperoxic lungs exhibited nuclear DNA strand breaks by comet assay even though they were viable and morphologically indistinguishable from cells isolated from lungs exposed to room air. These data reveal that type II cells exposed to in vivo hyperoxia have oxidized and fragmented DNA. Because type II cells are essential for lung remodeling, our findings raise the possibility that they are proficient in DNA repair.

This study investigates molecular mechanisms underlying cell cycle arrest when cells are exposed to high levels of oxygen (hyperoxia). Hyperoxia has previously been shown to increase expression of the cell cycle regulators p53 and p21. In the current study, we found that p53-deficient human lung adenocarcinoma H1299 cells failed to induce p21 or growth arrest in G1when exposed to 95% oxygen. Instead, cells arrested in S and G2. Stable expression of p53 restored induction of p21 and G1arrest without affecting mRNA expression of the other Cip or INK4 G1kinase inhibitors. To confirm the role of p21 in G1arrest, we created H1299 cells with tetracycline-inducible expression of enhanced green fluorescent protein (EGFP), EGFP fused to p21 (EGFp21), or EGFP fused to p27 (EGFp27), a related cell cycle inhibitor. The amino terminus of p21 and p27 bind cyclin-dependent kinases (Cdk), whereas the carboxy terminus of p21 binds the sliding clamp proliferating cell nuclear antigen (PCNA). EGFp21 or EGFp27, but not EGFP by itself, restored G1arrest during hyperoxia. When separately overexpressed, the amino-terminal Cdk and carboxy-terminal PCNA binding domains of p21 each prevented cells from exiting G1during exposure. These findings demonstrate that exposure in vitro to hyperoxia exerts G1arrest through p53-dependent induction of p21 that suppresses Cdk and PCNA activity. Because PCNA also participates in DNA repair, these results raise the possibility that p21 also affects repair of oxidized DNA.

Positive responses to combined androgen elimination therapy and radiation therapy have been well documented in the treatment of prostate cancer patients. The detailed mechanisms how androgen-androgen receptor (AR) cross talks to the radiation-related signal pathways, however, remain largely unknown. Here we report the identification of hRad9, a key member of the checkpoint Rad protein family, as a coregulator to suppress androgen-AR transactivation in prostate cancer cells. In vivo and in vitro interaction assays using Saccharomyces cerevisiae two-hybrid, mammalian two-hybrid, glutathione S-transferase pull-down, and coimmunoprecipitation methods prove that AR can interact with the C terminus of hRad9 via its ligand binding domain. The FXXLF motif within the C terminus of hRad9 interrupts the androgen-induced interaction between the N terminus and C terminus of AR. This interaction between AR and hRad9 may result in the suppression of AR transactivation, demonstrated by the repressed AR transactivation in androgen-induced luciferase reporter assay and the reduced endogenous prostate-specific antigen expression in Western blot assay. Addition of small interfering RNA of hRad9 can reverse hRad9 suppression effects, which suggests that hRad9 functions as a repressor of AR transactivation in vivo. Together, our data provide the first linkage between androgen-AR signals and radiation-induced responses. Further studies of the influence of hRad9 on prostate cancer growth may provide potential new therapeutic approaches.

Caffeic acid phenethyl ester (CAPE) is a biologically active ingredient of honeybee propoplis. The cytotoxicity and radiation sensitization effects of CAPE were evaluated in human lung cancer A549 cells and normal lung fibroblast WI-38 cells. A549 cells treated with 6 microg/ml CAPE showed marked growth inhibition (60%) at 48 hr after treatments. During the same time, the number of viable cells decreased to 46% of the control value. In contrast, WI-38 cells showed 20% growth inhibition with no change in the number of viable cells under the same treatment conditions. At 72 hr after CAPE treatment (6 microg/ml), the percentage of apoptotic cells in A549 cultures increased significantly to 67% and an S/G2 arrest was also detected in the culture. Furthermore, there was a significant decrease in the level of intracellular glutathione and hydrogen peroxide contents within one hr after CAPE treatment, and the expression of cyclin B1 was reduced 6 hr after treatment. The radiation sensitization effect of CAPE on A549 cells was determined from the clonogenic survival curves, and the results showed a small but significant difference in radiation survival between cells treated with or without CAPE. Taken together, our results suggest that the effects of CAPE on differential cytotoxicity, apoptosis, and radiosensitization are associated with glutathione depletion that occurred shortly after treatments.

Interleukin (IL)-1 is implicated in postmenopausal- and inflammation-mediated bone loss. Its expression is regulated by NF-kappaB and vice versa. To examine the role of NF-kappaB p50 and p52 (they are required for osteoclast formation during embryonic development) in IL-1-induced resorption, we used various NF-kappaB knockout (KO) mice, including p50-/- and p52-/- single KO, p50-/- and p52+/- (3/4KO), and p50-/- and p52-/- double KO (dKO) mice. IL-1 increased blood calcium and bone resorption in wild-type (wt), p50, and p52 single KO mice, but not in 3/4KO or dKO mice. Osteoclast formation was impaired in bone marrow cultures from 3/4KO compared with single KO and wt mice treated with IL-1. IL-1 receptor expression was similar in colony forming unit-granulocyte macrophage (CFU-GM) colony cells from wt and dKO mice. However, IL-1 promoted CFU-GM colony formation and survival as well as the formation, activity, and survival of osteoclasts generated from these colonies from wt mouse splenocytes, but not from dKO splenocytes. No difference in expression of the osteoclast regulatory cytokines, RANKL, and OPG, was observed in osteoblasts from wt and dKO mice. Thus, expression of either NF-kappaB p50 or p52 is required in osteoclasts and their precursors, rather than osteoblasts, for IL-1-mediated bone resorption.

Human salivary histatin 5 (Hst 5) is a nonimmune salivary protein with antifungal activity against an important human pathogen, Candida albicans. The candidacidal activity of histatins appears to be a distinctive multistep mechanism involving depletion of the C. albicans intracellular ATP content as a result of nonlytic ATP efflux. Hst 5 caused a loss of cell viability concomitant with a decrease in cellular volume as determined both by a classical candidacidal assay with exogenous Hst 5 and by using a genetically engineered C. albicans strain expressing Hst 5. Preincubation of C. albicans cells with pharmacological inhibitors of anion transport provided complete or substantial protection from Hst 5-induced killing and volume reduction of cells. Moreover, intracellular expression of Hst 5 resulted in a reduction in the population mean cell volume that was accompanied by an increase in the percentage of unbudded cells and C. albicans cells in the G 1 phase. Following expression of Hst 5, the smallest cells sorted by fluorescence-activated cell sorting from the total population did not replicate and were exclusively in the G 1 phase. Cells with intracellularly expressed Hst 5 had greatly reduced G 1 cyclin transcript levels, indicating that they arrested in the G 1 phase before the onset of Start. Our data demonstrate that a key determinant in the mechanism of Hst 5 toxicity in C. albicans cell s is the disruption of regulatory circuits for cell volume homeostasis that is closely coupled with loss of intracellular ATP. This novel process of fungicidal activity by a human salivary protein has highlighted potential interactions of Hst 5 with volume regulatory mechanisms and the process of yeast cell cycle control.