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Bafilomycin C1, which was isolated from Streptomyces albolongus in our previous work, exhibited strong cytotoxicity against several cancer cell lines. This study aimed to evaluate its antitumor effect on human hepatocellular cancer SMMC7721 cells and the underlying mechanism in vitro and in vivo. MTT assay revealed that bafilomycin C1 retarded SMMC7721 cell growth and proliferation. Western blot and real-time qPCR analysis revealed that bafilomycin C1 caused partial G0/G1 phase cell-cycle arrest, downregulated the expression of cyclin D3, cyclin E1, CDK2, CDK4, and CDK6 and upregulated the expression of p21. Moreover, bafilomycin C1 caused mitochondrial membrane dysfunction through oxidative stress. Furthermore, bafilomycin C1 decreased the expression of Bcl-2; increased the expression of Bax, p53, and P-p53; and increased cleavage of caspase-9 and caspase-3, thereby inducing the intrinsic caspase-dependent apoptotic pathway. In vivo experiments in mice suggested that bafilomycin C1 suppressed tumor growth with few side effects. Cell-cycle arrest and induced apoptosis in tumor tissues in a mouse model treated with bafilomycin C1 were demonstrated by histological analyses, western blot and TUNEL. These findings indicate that bafilomycin C1 may be a promising candidate for hepatic cellular cancer therapy.

Pituitary tumor-transforming gene-1 (PTTG1) encodes securin, a multifunctional protein involved in development of various types of cancer. Securin participates in the regulation of sister chromatids separation and the expression of multiple genes involved in the control of the cell cycle, metabolism, and angiogenesis. In several human cell lines, we have found a novel short isoform of securin mRNA, which does not contain exons 3 and 4. After the translation of this new mRNA, a shortened protein is produced that, like the full-size form, is able to activate the transcription of cyclin D3 gene (CCND3), which controls the G1/S transition and angiogenesis factors VEGFA (vascular endothelial growth factor), and FGF2 (fibroblast growth factor 2) in HEK293 cells. However, unlike the full-size protein, the short isoform of PTTG1 does not affect the MYC gene expression because it lacks the DNA-binding domain, which is needed for its interactions with the MYC promoter. Furthermore, the short form of securin does not influence the expression of MYC transcriptional targets, such as TP53 and IL-8. Thus, we found a novel isoform of securin which is able to activate a more restricted repertoire of genes compared to the full-size protein.

The role of progenitor/stem cells in pituitary tumorigenesis, resistance to pharmacological treatments and tumor recurrence is still unclear. This study investigated the presence of progenitor/stem cells in non-functioning pituitary tumors (NFPTs) and tested the efficacy of dopamine receptor type 2 (DRD2) and somatostatin receptor type 2 (SSTR2) agonists to inhibit in vitro proliferation. They found that 70% of 46 NFPTs formed spheres co-expressing stem cell markers, transcription factors (DAX1, SF1, ERG1) and gonadotropins. Analysis of tumor behavior showed that spheres formation was associated with tumor invasiveness (OR = 3,96; IC: 1.05-14.88, p = 0.036). The in vitro reduction of cell proliferation by DRD2 and SSTR2 agonists (31 ± 17% and 35 ± 13% inhibition, respectively, p < 0.01 vs. basal) occurring in about a half of NFPTs cells was conserved in the corresponding spheres. Accordingly, these drugs increased cyclin-dependent kinase inhibitor p27 and decreased cyclin D3 expression in spheres. In conclusion, they provided further evidence for the existence of cells with a progenitor/stem cells-like phenotype in the majority of NFPTs, particularly in those with invasive behavior, and demonstrated that the antiproliferative effects of dopaminergic and somatostatinergic drugs were maintained in progenitor/stem-like cells., (© 2017 UICC.)

Chronic lymphocytic leukaemia (CLL) is associated with apoptosis resistance and defective control of cell growth. Our study describes for the first time a critical role in CLL for the KRAB-zinc finger protein ZNF224. High ZNF224 transcript levels were detected in CLL patients with respect to control cells. Moreover, ZNF224 expression was significantly lowered after conventional chemotherapy treatment in a subset of CLL patients. By in vitro experiments we confirmed that ZNF224 expression is suppressed by fludarabine and demonstrated that ZNF224 is involved in apoptosis resistance in CLL cells. Moreover, we showed that ZNF224 positively modulates cyclin D3 gene expression. Consistently, we observed that alteration of ZNF224 expression leads to defects in cell cycle control. All together, our results strongly suggest that in CLL cells high expression level of ZNF224 can lead to inappropriate cell growth and apoptosis resistance, thus contributing to CLL progression. Targeting ZNF224 could thus improve CLL response to therapy., (© The Author 2016. Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.)

IGF-2 mRNA binding protein 3 (IGF2BP3, IMP-3) is a well-known post-transcriptional regulatory factor of gene expression, mainly involved in embryonic development and oncogenesis. We have previously demonstrated that a subset of IMP-3 targets, such as the mRNAs of cyclins D1, D3 and G1, are positively regulated by IMP-3, and that this regulation depends on nuclear localization of IMP-3. In the present study, we show that as a first step following a knock-down of IMP-3, the protein levels of the cyclins rapidly decrease, while their mRNAs remain stable and associated with the polyribosomes, though not translated. We have elucidated the molecular mechanisms of this regulation, demonstrating that IMP-3 and its protein partners ILF3/NF90 and PTBP1 bind to the 3'UTRs of the cyclin mRNAs and protect them from the translational repression induced by miRNA-dependent recruitment of AGO2/GW182 complex in human cancer cells.

Background/aim: The current study investigated the mechanisms underlying the antitumor activity of SB265610, a cysteine-amino acid-cysteine (CXC) chemokines receptor 2 (CXCR2) antagonist., Materials and Methods: Cell-cycle progression and regulatory molecules were assessed by flow cytometry, immunoblotting, real-time PCR and immunoprecipitation. Target validation was achieved via RNA interference., Results: G1 arrest induced by SB265610 occurred at concentrations lacking CXCR2 selectivity, persisted upon interleukin 8 (IL8) challenge, and did not affect IL8 downstream target expression. Profiling of G1 regulators revealed cyclin-dependent kinase 2 (CDK2) (Thr160) hypophosphorylation, cyclin D3 gene down-regulation, and p21 post-translational induction. However, only cyclin D3 and CDK2 contributed towards G1 arrest. Furthermore, SB265610 induced a sustained phosphorylation of the p38MAPK. Pharmacological interference with p38MAPK significantly abrogated SB265610-induced G1 arrest and normalized the expression of cyclin D3, with restoration of its exclusive binding to CDK6, but with weak recovery of CDK2 (Thr160) hypo-phosphorylation., Conclusion: The present study described the mechanisms for the anti-proliferative activity of SB265610 which may be of value in IL8-rich tumor microenvironments., (Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Deregulated mRNA translation has been implicated in disease development and in part is controlled by a eukaryotic initiation complex eIF4F (composed of eIF4E, eIF4G and eIF4A). We demonstrate here that the cap bound fraction from lymphoma cells was enriched with eIF4G and eIF4E indicating that lymphoma cells exist in an activated translational state. Moreover, 77% (110/142) of diffuse large B cell lymphoma tumors expressed eIF4E and this was associated with an inferior event free survival. Over-expression of wild-type eIF4E (eIF4E(WT)) but not cap-mutant eIF4E (eIF4E(cap mutant)) increased the activation of the eIF4F complex. Treatment with the active-site dual mTOR inhibitor CC214-1 reduced the level of the eIF4F complex by decreasing the cap bound fraction of eIF4G and increasing the levels of 4E-BP1. CC214-1 inhibited both the cap dependent and global protein translation. CC214-1 inhibited c-Myc, and cyclin D3 translation by decreasing polysomal fractions from lymphoma cells. Inhibition of eIF4E with shRNA further decreased the CC214-1 induced inhibition of the eIF4F complex, c-Myc, cyclin D3 translation, and colony formation. These studies demonstrate that the eIF4F complex is deregulated in aggressive lymphoma and that dual mTOR therapy has therapeutic potential in these patients.

Here we report that both PLCβ1a and PLCβ1b are relevant regulators of erythropoiesis in that kinamycin F, a potent inducer of γ-globin production in K562 cells, caused a selectively reduction of both PLCβ1 isozymes even though the results point out that the effect of the drug is mainly directed toward the expression of the PLCβ1a isoform. We have identified a different role for the two isozymes as regulators of K562 differentiation process induced by kinamycin F. The overexpression of PLCβ1b induced an increase in γ-globin expression even in the absence of kinamycin F. Moreover during K562 differentiation, cyclin D3 level is regulated by PLCβ1 signaling pathway. Namely the amplification of the expression of the PLCβ1a, but not of PLCβ1b, is able to maintain high levels of expression of cyclin D3 even after treatment with kinamycin F. This could be due to their different distribution in the cell compartments since the amount of PLCβ1b is mainly present in the nucleus in respect to PLCβ1a. Our data indicate that the amplification of PLCβ1a expression, following treatment with kinamycin F, confers a real advantage to K562 cells viability and protects cells themselves from apoptosis., (© 2014 Wiley Periodicals, Inc., A Wiley Company.)

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplastic disorder of immature hematopoietic precursors committed to T-cell lineage. T-ALL accounts for ~15% of pediatric ALL cases and is prone to early relapse. With new and improved treatment protocols, the prognosis of T-ALL has improved particularly in children; however, the outcome of relapsed T-ALL cases remains poor. The AIOLOS gene is necessary to control lymphocyte differentiation and may be a potential target of T-ALL therapy. In the present study, Jurkat cells were divided into three groups: untransfected (UT) control, lentiviral vector control (Lenti-Mock) and AIOLOS-overexpressing (Lenti-AIOLOS) groups. Lenti-AIOLOS Jurkat cells were constructed by lentiviral transduction; cell cycle analysis, apoptosis and cytotoxicity assays were then performed to evaluate the effects of AIOLOS on cell cycle distribution, apoptosis and cell chemosensitivity to etoposide of Jurkat cells in vitro. Moreover, the expression levels of genes associated with apoptosis and cell cycle were investigated by quantitative reverse transcription-polymerase chain reaction. Results showed that the percentage of Jurkat cells in the G0/G1 phase increased from 71.5 (UT) to 85.4% (Lenti-AIOLOS; P<0.05), yet the percentage of cells in the S-phase decreased from 15.1 (UT) to 11.6% (Lenti‑AIOLOS; P<0.05). The percentage of total apoptotic cells was significantly increased in the AIOLOS-transfected Jurkat cells (21.93%) compared with this percentage in the Lenti-Mock (13.35%) or the UT group (13.30%; P<0.05). Consistent with these results, AIOLOS overexpression induced P21 and P27 upregulation and CCND3 and SKP2 downregulation. Furthermore, AIOLOS overexpression synergistically increased the cytotoxic effects of etoposide and downregulated NF-κB expression. Our findings revealed that lentivirus-mediated AIOLOS overexpression in Jurkat cells induced cell apoptosis, arrested the cell cycle at the G0/G1 phase, and synergistically increased the sensitivity of Jurkat cells to etoposide by inhibiting NF-κB activity.

Isolated rat bone marrow stromal cells cultured in osteogenic medium in which the normal 5.6 mm glucose is changed to hyperglycemic 25.6 mm glucose greatly increase lipid formation between 21-31 days of culture that is associated with decreased biomineralization, up-regulate expression of cyclin D3 and two adipogenic markers (CCAAT/enhancer binding protein α and peroxisome proliferator-activated receptor γ) within 5 days of culture, increase neutral and polar lipid synthesis within 5 days of culture, and form a monocyte-adhesive hyaluronan matrix through an endoplasmic reticulum stress-induced autophagic mechanism. Evidence is also provided that, by 4 weeks after diabetes onset in the streptozotocin-induced diabetic rat model, there is a large loss of trabecular bone mineral density without apparent proportional changes in underlying collagen matrices, a large accumulation of a hyaluronan matrix within the trabecular bone marrow, and adipocytes and macrophages embedded in this hyaluronan matrix. These results support the hypothesis that hyperglycemia in bone marrow diverts dividing osteoblastic precursor cells (bone marrow stromal cells) to a metabolically stressed adipogenic pathway that induces synthesis of a hyaluronan matrix that recruits inflammatory cells and establishes a chronic inflammatory process that demineralizes trabecular cancellous bone.

Carnosol, an active constituent of rosemary, has been reported to possess anti-inflammatory and anticancer activities. However, the molecular mechanisms underlying the anticancer effects of carnosol remain poorly understood. In the present study, we found that carnosol significantly reduced the viability of human colon cancer (HCT116) cells in a concentration- and time-dependent manner. Treatment of cells with carnosol induced apoptosis, which was associated with activation of caspase-9 and -3 and the cleavage of poly-(ADP-ribose) polymerase (PARP). Incubation with carnosol elevated the expression of Bax and inhibited the levels of Bcl-2 and Bcl-xl. Carnosol induced expression of p53 and inhibited that of murine-double minute-2 (Mdm2). Moreover, carnosol generated reactive oxygen species (ROS), and pretreatment with N-acetyl cysteine abrogated carnosol-induced cleavage of caspase-3 and PARP. The constitutive phosphorylation, the DNA binding and reporter gene activity of signal transducer and activator of transcription-3 (STAT3) was diminished by treatment with carnosol. To further elucidate the molecular mechanisms of STAT3 inactivation, we found that carnosol attenuated the phosphorylation of Janus-activated kinase-2 (Jak2) and Src kinase. Pharmacological inhibition of Jak2 and Src inhibited STAT3 phosphorylation. Furthermore, carnosol attenuated the expression of STAT3 target gene products, such as survivin, cyclin-D1, -D2, and -D3. Taken together, our study provides the first report that carnosol induced apoptosis in HCT116 cells via generation of ROS, induction of p53, activation of caspases and inhibition of STAT3 signaling pathway.

Activation of astrocytes in central nervous system inflammation leads to a disturbance of crosstalk between astrocytes and neurons, and that this may contribute to the death of neurons. CDK11(p58) is a member of the large family of p34cdc2-related kinases. It specifically expresses in G2/M phase of the cell cycle and is closely related to cell cycle arrest and apoptosis. Here, we show that astrocyte-conditioned medium stimulated by lipopolysaccharide upregulates CDK11(p58) expression and meanwhile causes neuronal apoptosis. CDK11(p58) knockdown in PC12 cells represses neuronal apoptosis. CDK11(p58) overexpression in PC12 cells promotes neuronal apoptosis. AKT signaling pathway is involved in CDK11(p58)-induced neuronal apoptosis process.

The Adrenocorticotropic hormone (ACTH) and Pro-opimelanocortin (POMC) 1-28N-terminal peptide (N-POMC(1-28)) have been shown to act as an adrenal mitogen in vivo. A possible role for cyclin E in the zona glomerulosa (ZG) proliferation, following ACTH and/or N-POMC(1-28) administration, has been previously demonstrated. In this study, we investigated the effect of ACTH and N-POMC(1-28) on the expression of adrenal cortex proteins related to cell cycle control such as cyclins D and P27(kip1). The administration of N-POMC upregulated cyclin D1 and D2 expression in the outer zone of the adrenal cortex; cyclin D3 expression was upregulated in the cortex inner zone even after administration of ACTH. Both ACTH and N-POMC peptides induced a decrease in the P27(kip1) expression in the ZG. These novel findings suggest that the POMC-derivate peptides, ACTH and N-POMC, promote proliferation in the adrenal cortex by upregulating the D2 and D3 cyclins and downregulating the P27(kip1) expression., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Inorganic arsenic is a toxic environmental contaminant to which humans are mainly exposed through drinking water. This metalloid impairs functions of several key immune cells. Particularly, it reduces IL-2 secretion and proliferation of blood peripheral mononuclear cells stimulated by lectins that, however, do not mimic physiological T cell activation. The present study used isolated human T cells activated, in a more physiological manner, through stimulation with CD3/CD28 antibodies, to carefully analyze the impact of arsenic on T cell proliferation and cytokine expression. We demonstrate that non cytotoxic concentrations of sodium arsenite (As(III), 0.25-2μM) significantly reduce T cell proliferation by increasing the percentage of non dividing cells blocked in G1 phase and by preventing cyclin D3 and CDC25A expression. They also markedly, although not totally, reduces IL-2 expression at both mRNA and protein levels; however, metalloid-dependent inhibition of T cells could not be reversed by addition of recombinant IL-2. In addition, As(III) markedly reduces secretion of interferon-γ without impairing that of IL-4 and IL-13; it also decreases interferon-γ mRNA levels but increases those of IL-13. Finally, simultaneously to its immune effects, As(III) rapidly and potently increases expression of the redox-sensitive genes HMOX1, NQO1 and GCLM in activated T cells without altering the levels of reactive oxygen species. In conclusion, our results demonstrate that As(III) inhibits T cell proliferation, independently of IL-2, and alters the Th balance of cytokines secreted by co-stimulated T cells which thus constitute direct targets of this major environmental contaminant., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

The TNF ligand family member "B cell-activating factor belonging to the TNF family" (BAFF, also called BLyS, TALL-1, zTNF-4, and THANK) is an important survival factor for B and T cells. In this study, we show that BAFF is able to induce CD4(+) spleen T cell proliferation when co-stimulated with anti-CD3. Expression of phosphorylated FOXO3A was notably down-regulated and cyclins D2 and D3 were up-regulated and higher in the CD4(+) T cells when treated with BAFF and anti-CD3, as assessed by Western blotting. Furthermore, after FOXO3A was knocked down, expression of cyclin D1 was unchanged, compared with control group levels, but the expression of cyclins D2 and D3 increased, compared with the control group. In conclusion, our results suggest that BAFF induced CD4(+) spleen T cell proliferation by down-regulating the phosphorylation of FOXO3A and then activating cyclin D2 and D3 expression, leading to CD4(+) T cell proliferation., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Embryonal tumors constitute the most common malignant brain tumor group in children. Experimental results indicate that genes involved in cell cycle and signal transduction are deregulated in medulloblastoma (MB) and atypical teratoid/rhabdoid tumors (AT/RT). The cell cycle is regulated by protein complexes composed of a regulatory subunit called Cyclin and a catalytic domain named Cyclin-dependent kinase (CDK). Cyclins and CDKs are in turn regulated by cyclin-dependent kinase inhibitors (CDKI) which inhibit cell-cycle progression. Cyclins D and Cyclin E are important for the passage of cells through G1 to S phase. P-27, a member of the universal CDKI family, is important in regulating the G1/S transition. Thus, the purpose of this study was to investigate the expression of p-27, Cyclin D3, and Cyclin E, and their possible prognostic significance in pediatric embryonal brain tumors. We retrospectively evaluated 51 children with embryonal tumors that were treated surgically in our institute. All patients had regular follow up examinations. The streptavidin-biotin HRP method was performed on paraffin sections for detection of p-27, Cyclin D3, and Cyclin E. There were 42 cases of MB and nine cases of AT/RT. Cyclin D3 expression was detected in 11/42 MB and 3/9 AT/RT patients. Cyclin E expression was detected in 28/42 MB and 8/9 AT/RT patients. High expression of Ki-67 (>50 %) and p-27 (>50 %) was observed in 23.8-73.8 % of MB patients. Combined high Ki-67 and p-27 expression was observed in 21.4 % cases of MB. In these cases there was expression of Cyclin E in 88.8 % and Cyclin D3 in 22.2 % of MB. No significant correlation was found between Ki-67 and p-27, Cyclin D3, and E. No correlation was found between Cyclin D3, Cyclin E, p-27, and overall survival. Increased p-27 and Cyclin E expression was detected in a substantial number of MB patients and in nearly all AT/RT patients. Further studies on a larger number of patients are needed to clarify a possible correlation of p-27 and Cyclin E with tumor behavior.

The deregulation of microRNA (miRNA) is frequently associated with a variety of cancers, including hepatocellular carcinoma (HCC). In this study, we identified 10 upregulated miRNAs (miR-217, miR-518b, miR-517c, miR-520g, miR-519a, miR-522, miR-518e, miR-525-3p, miR-512-3p and miR-518a-3p) and 10 downregulated miRNAs (miR-138, miR-214, miR-214#, miR-27a#, miR-199a-5p, miR-433, miR-511, miR-592, miR-483-5p and miR-483-3p) by Taqman miRNAs array and quantitative real-time PCR (qRT-PCR) confirmation. Additionally, we investigated the expression and possible role of miR-138 in HCC. qRT-PCR results showed that miR-138 was downregulated in 77.8%(14/18) of HCC tissues compared with adjacent non-tumor tissues. Overexpression of miR-138 reduced cell viability and colony formation by induction of cell arrest in HCC cell lines and inhibited tumor cell growth in xenograft nude mice. The use of miR-138 inhibitor increased cell viability and colony formation in HCC cell lines and tumor cell growth in xenograft nude mice. Using TargetScan predictions, CCND3 was defined as a potential direct target of miR-138. Furthermore, CCND3 protein expression was observed to be negatively correlated with miR-138 expression in HCC tissues. The dual-luciferase reporter gene assay results showed that CCND3 was a direct target of miR-138. The use of miR-138 mimic or inhibitor could decrease or increase CCND3 protein levels in HCC cell lines. We conclude that the frequently downregulated miR-138 can regulate CCND3 and function as a tumor suppressor in HCC. Therefore, miR-138 may serve as a useful therapeutic agent for miRNA-based HCC therapy.

Aims: Pituitary prolactinoma is one of the estrogen-related tumors, some anti-estrogen compounds have suppressive effects on prolactinoma. Previous studies have suggested that resveratrol, a phytoestrogen, displays anti-estrogen and anti-tumor characteristics. Therefore, We determined whether resveratrol could inhibit the cell proliferation and decrease prolactin level in prolactinoma cell line, and identify the signaling pathways that mediate the effects of resveratrol., Main Methods: Prolactinoma cell line, GH3 cells were treated with resveratrol. Changes in proliferation, cell cycle, and apoptosis were assessed. The level of prolactin was assayed by Western blot or EIA. Expression of total Rb (retinoblastoma protein), phosphorylated Rb (pRb) and cyclin D3 were measured by Western blot. The changes of estrogen receptors and their roles in the effects of resveratrol were also determined., Key Findings: We report that resveratrol had a dose-dependent inhibitory effect on GH3 cell proliferation. Inhibitory effects of resveratrol persisted, even on removal of resveratrol. The growth-inhibitory effect of resveratrol was accompanied by decreased expression of cyclin D3 and pRb. In addition, resveratrol induced G0/G1 cell cycle block and apoptosis. Furthermore, resveratrol suppressed intracellular levels and release of prolactin. Finally, we show that two types of estrogen receptor were involved in the different effects of resveratrol., Significance: Taken together, we demonstrate that resveratrol could inhibit prolactinoma cell proliferation, induce cell cycle block and apoptosis, and decrease prolactin production and release, and estrogen receptors mediate its antitumor effects. And thus, these results lead us to propose developing resveratrol as a novel therapeutic agent for treatment of prolactinoma., (Copyright © 2011 Elsevier B.V. All rights reserved.)

RGS19 is a regulator of G protein signaling which is upregulated in ovarian cancers and its overexpression promotes cell proliferation in several mammalian cell types. Here we showed that cyclin D1/3 and Cdk6 were upregulated in HEK293 cells overexpressing RGS19, while INK4A and INK4B were reduced. Moreover, RGS19 augmented serum-stimulated PTEN/PDK/Akt and Rb phosphorylations in 293/RGS19 and Caco2/RGS19 cells. These changes were reversed upon the knockdown of RGS19. Consistent with an elevated Akt activity, increased levels of phosphorylated Bad and c-Raf and a diminished expression of TSC2 were detected, thus demonstrating that RGS19 can deregulate cell proliferation via multiple pathways., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

In our laboratory, a novel therapeutic probe, T11TS, a membrane glycoprotein, was isolated which had antineoplastic activity against experimental glioma. Development of a novel therapeutic strategy with T11TS has unearthed a newer dimension of its mechanism of action: modulation of the cell cycle. In this study, we have presented evidence to support the finding that T11TS induces G1 cell cycle arrest of rat glioma cells. Results of flow cytometric studies showed that the treatment produced a marked increase in the proportion of cells in the G1 phase. Flow cytometry, immunoblotting, immunoprecipitation, and kinase assays were performed for investigating the involvement of G1 cell cycle regulators. T11TS induces downregulation of the cyclin-D (1 and 3) expression with the concurrent upregulation of p21 and p27 and their concomitant association with cyclin-dependent kinase 4, proliferating cell nuclear antigen and cyclin E respectively leading to a decrease in cyclin-dependent kinase 4 kinase activity. A transient rise in retinoblastoma protein level and coordinated binding of retinoblastoma protein with E2F coincided with the accumulation of cells in G1 phase. Thus, our observations have uncovered an antiproliferative pathway for T11TS, causing retardation of glioma cell cycle.

Proteasome inhibitors and protease inhibitors are currently being discussed to be useful to sensitize drug-resistant cancer cells to chemotherapeutic agents or to act independently as single agents on drug-resistant cancer cells. We tested the effect of the clinically applied HIV protease inhibitor nelfinavir on ovarian cancer cells. Nelfinavir efficiently induced cell death in carboplatin-sensitive (SKOV3, OV-GH-5) and carboplatin-resistant (OVCAR3, OV-GH-1) ovarian cancer cell lines as well as in cancer biopsies and ascites samples from patients with recurrent ovarian cancer. Nelfinavir significantly changed the morphology of ovarian cancer cells, resulting in formation of large ER-derived vacuoles and induced upregulation of the hsp70 heat shock family member BiP (GRP78) which accumulated within swollen ER membranes. Upregulation of BiP and phosphorylation of eIF2alpha indicated induction of the unfolded protein response, which can cause cell cycle arrest and apoptosis. Correspondingly, we observed downregulation of cell cycle regulatory proteins after nelfinavir treatment, especially that of cyclin D3, and induction of apoptosis as confirmed by annexin binding. Because nelfinavir represents an already approved drug for use in humans with HIV infection, it could rapidly be tested in clinical studies as a potential treatment strategy against drug-resistant ovarian cancer.