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Background To analysis the clinical outcomes of concurrent chemoradiotherapy (CCRT) alone based on 10-year results for loco-regionally advanced nasopharyngeal carcinoma (LANPC), so as to provide evidence for individualized treatment strategy and designing appropriate clinical trial for different risk LANPC patients. Methods Consecutive patients with stage III-IVa (AJCC/UICC 8th) were enrolled in this study. All patients received radical intensity-modulated radiotherapy (IMRT) and concurrent cisplatin chemotherapy (CDDP). The hazard ratios (HRs) of death risk in patients with T3N0 was used as baseline, relative HRs were calculated by a Cox proportional hazard model to classify different death risk patients. Survival curves for the time-to-event endpoints were analyzed by the Kaplan–Meier method and compared using the log-rank test. All statistical tests were conducted at a two-sided level of significance of 0.05. Results A total of 456 eligible patients were included. With 12-year median follow-up, 10-year overall survival (OS) was 76%. 10-year loco-regionally failure-free survival (LR-FFS), distant failure-free survival (D-FFS) and failure-free survival (FFS) were 72%, 73% and 70%, respectively. Based on the relative hazard ratios (HRs) of death risk, LANPC patients were classified into 3 subgroups, low-risk group (T1-2N2 and T3N0-1) contained 244 patients with HR 5. The 10-year OS for patients in low-, medium-, and high-risk group were 86%, 71% and 52%, respectively. Significantly differences of OS rates were found between each of the two groups (low-risk group vs. medium-risk group, P vs. high-risk group, P vs. high-risk group, P = 0.002, respectively). Grade 3–4 late toxicities included deafness/otitis (9%), xerostomia (4%), temporal lobe injury (5%), cranial neuropathy (4%), peripheral neuropathy (2%), soft tissue damage (2%) and trismus (1%). Conclusions Our classification criteria demonstrated that significant heterogeneity in death risk among TN substages for LANPC patients. IMRT plus CDDP alone maybe suitable for low-risk LANPC (T1-2N2 or T3N0-1), but not for medium- and high-risk patients. These prognostic groupings provide a practicable anatomic foundation to guide individualized treatment and select optimal targeting in the future clinical trials.

Worldwide, nasopharyngeal carcinoma (NPC) is a rare head and neck cancer; however, it is a common malignancy in southern China. Radiotherapy is the most important treatment strategy for NPC. However, although radiotherapy is a strong tool to kill cancer cells, paradoxically it also promotes aggressive phenotypes. Therefore, we mimicked the treatment process in NPC cells in vitro. Upon exposure to radiation, a subpopulation of NPC cells gradually developed resistance to radiation and displayed cancer stem-cell characteristics. Radiation-induced stemness largely depends on the accumulation of the antiapoptotic myeloid cell leukemia 1 (MCL-1) protein. Upregulated MCL-1 levels were caused by increased stability and more importantly, enhanced protein synthesis. We showed that repeated ionizing radiation resulted in persistently enhanced reactive oxygen species (ROS) production at a higher basal level, further promoting protein kinase B (AKT) signaling activation. Intracellular ROS and AKT activation form a positive feedback loop in the process of MCL-1 protein synthesis, which in turn induces stemness and radioresistance. AKT/MCL-1 axis inhibition attenuated radiation-induced resistance, providing a potential target to reverse radiation therapy-induced radioresistance.

Objective: This study aimed to explore the clinical value of adjuvant chemotherapy (ACT) in locoregionally advanced nasopharyngeal carcinoma (LANC) following concurrent chemoradiotherapy (CCRT) and induction chemotherapy (ICT).Methods: We included 839 newly diagnosed LANC patients in the study. ICT plus CCRT (ICT+CCRT group) was administered to 443 patients and 396 patients who received ACT after receiving ICT plus CCRT (ICT+CCRT+ACT group). Univariate and multivariate Cox regression analyses were carried out in this study. Furthermore, to balance the study and control groups, propensity score matching (PSM) was applied.Results: 373 pairs of LANC patients were obtained after the PSM analysis. We found that ACT following ICT+CCRT had no significant effect on improving the survival of LANC patients. By further exploring the ICT+CCRT+ACT regimen, we excluded N0-1-positive patients and performed PSM in the ICT+CCRT and ICT+CCRT+ACT groups again. Each group consisted of 237 patients. Kaplan-Meier analysis revealed that there was a difference between the ICT+CCRT and ICT+CCRT+ACT groups in terms of the 5-year overall survival (OS) (78.9% vs. 85.0%, P = 0.034), disease-free survival (DFS) (73.4% vs. 81.7%, P = 0.029), and distant metastasis-free survival (DMFS) (84.9% vs. 76.0%, P = 0.019). In addition, the ICT+CCRT+ACT group had a higher incidence of grade 3-4 acute leukocytopenia/neutropenia.Conclusion: Compared with ICT+CCRT, ACT following ICT plus CCRT can reduce distant metastasis of N2-3-positive LANC and improve the OS and DFS of these patients, thus demonstrating higher clinical feasibility.

Aims: This study aimed to investigate the clinical value of induction chemotherapy (IC) with docetaxel, 5-fluorouracil plus nedaplatin followed by concurrent chemoradiotherapy (CCRT) with nedaplatin for locoregional advanced nasopharyngeal carcinoma (NPC). Materials and Methods: In total, 269 patients diagnosed with locoregional advanced NPC between June 2012 and June 2017 were retrospectively included and divided into two groups: IC (docetaxel plus nedaplatin and 5-fluorouracil) followed by nedaplatin-based CCRT (TNF + N group, n = 146) and IC (docetaxel plus cisplatin and 5-fluorouracil) followed by cisplatin-based CCRT (TPF + P group, n = 123). The Kaplan-Meier method and Cox proportional hazards model were applied to analyse survival and prognosis. After propensity score-matched (PSM), 113 patients remained in each group. Toxicities were compared between the two groups using the Chi-square test or Fisher's exact test. Results: The overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRRFS) rates of the TNF + N and TPF + P groups were 90.7% vs. 92.3% (P = 0.315), 78.9% vs. 79.4% (P = 0.715), 82.4% vs. 85.1% (P = 0.441) and 96.1% vs. 93.3% (P = 0.414), respectively, with no significant difference in 3-year survival outcome between the two groups, and this outcome was confirmed after using PSM analyses. In the PSM cohort, a significant higher frequency of grade 3/4 vomiting was observed in the TPF + P group compared to the TNF + N group (22.1% vs. 0%, P = 0.000). However, 15.9% of patients in the TNF + N group had grade 3/4 thrombocytopenia in comparison with 6.2% in the TPF + P group (P = 0.020). Conclusions: The TNF regimen followed by CCRT with nedaplatin is an alternative treatment strategy to the standard TPF regimen followed by CCRT with cisplatin for patients with locoregional advanced NPC.

BackgroundThe optimal second-line systemic treatment model for recurrent and/or metastatic head and neck squamous cell carcinoma (R/M HNSCC) remains controversial. A Bayesian network meta-analysis (NMA) was performed to address this issue with regard to efficacy and toxicity.MethodsBy searching MEDLINE (via PubMed), Embase, the Cochrane Central Register of Controlled Trials and Web of Science, we extracted eligible studies. Efficacy, represented as overall survival (OS) and progression-free survival (PFS), and overall toxicity, represented as ≥ grade 3 severe acute events (sAE), were assessed to compare the following 7 treatment models through an NMA: standard-of-care therapy (SoC), single targeted therapy different from SoC (ST), double targeted therapy (DT), targeted therapy combined with chemotherapy (T+C), single immune checkpoint inhibitor therapy (SI), double immune checkpoint inhibitor therapy (DI) and single chemotherapy different from SoC (SC). Rank probabilities according to the values of the surface under the cumulative ranking curve (SUCRA) were separately determined for efficacy and toxicity.ResultsIn total, 5285 patients from 24 eligible studies were ultimately screened, with 5184, 4532 and 4026 involved in the NMA of OS, PFS and sAE, respectively. All qualifying studies were absent from first-line immune checkpoint inhibitor therapy. In terms of OS, SI was superior to the other treatments, followed by DI, ST, T+C, SoC, DT and SC. Other than SI and SC, all treatments tended to be consistent, with hazard ratios (HRs) close to 1 between groups. For PFS, ST ranked first, while DT ranked last. For the toxicity profiles, compared with the other models, SI resulted in the lowest incidences of sAE, with statistical significance over SoC (odds ratio [OR] 0.31, 95% credible interval [CrI] 0.11 to 0.90), ST (OR 0.23, 95% CrI 0.06 to 0.86) and DT (OR 0.11, 95% CrI 0.02 to 0.53), while DT was the worst. When the SUCRA values of OS and sAE were combined, a cluster plot illustrated the superiority of SI, which demonstrated the best OS and tolerability toward sAE.ConclusionFor R/M HNSCC patients without immune checkpoint inhibitors in the first-line setting, SI may serve as the optimal second-line systemic treatment model, demonstrating the best OS and least sAE.

Nasopharyngeal carcinoma (NPC) is a highly aggressive tumor characterized by distant metastasis. Deletion or down-regulation of the tumor suppressor protein ras-association domain family protein1 isoform A (RASSF1A) has been confirmed to be a key event in NPC progression; however, little is known about the effects or underlying mechanism of RASSF1A on the malignant phenotype. In the present study, we observed that RASSF1A expression inhibited the malignant phenotypes of NPC cells. Stable silencing of RASSF1A in NPC cell lines induced self-renewal properties and tumorigenicity in vivo/in vitro and the acquisition of an invasive phenotype in vitro. Mechanistically, RASSF1A inactivated Yes-associated Protein 1 (YAP1), a transcriptional coactivator, through actin remodeling, which further contributed to Platelet Derived Growth Factor Subunit B (PDGFB) transcription inhibition. Treatment with ectopic PDGFB partially increased the malignancy of NPC cells with transient knockdown of YAP1. Collectively, these findings suggest that RASSF1A inhibits malignant phenotypes by repressing PDGFB expression in a YAP1-dependent manner. PDGFB may serve as a potential interest of therapeutic regulators in patients with metastatic NPC.

Marked up-regulation of aldose reductase (AR) is reportedly associated with the development of hepatocellular carcinoma (HCC). We investigated how aberrantly overexpressed AR might promote oncogenic transformation in liver cells and tissues. We found that overexpressed AR interacted with the kinase domain of AKT1 to increase AKT/mTOR signaling. In both cultured liver cancer cells and liver tissues in DEN-induced transgenic HCC model mice, we observed that AR overexpression-induced AKT/mTOR signaling tended to enhance lactate formation and hepatic inflammation to enhance hepatocarcinogenesis. Conversely, AR knockdown suppressed lactate formation and inflammation. Using cultured liver cancer cells, we also demonstrated that AKT1 was essential for AR-induced dysregulation of AKT/mTOR signaling, metabolic reprogramming, antioxidant defense, and inflammatory responses. These findings suggest that aberrantly overexpressed/over-activated hepatic AR promotes HCC development at least in part by interacting with oncogenic AKT1 to augment AKT/mTOR signaling. Inhibition of AR and/or AKT1 might serve as an effective strategy for the prevention and therapy of liver cancer.

Ras association domain family member 6 (RASSF6) has been shown to act as a tumor suppressor and predictor of poor prognosis in renal cell carcinoma (RCC). However, little is known about the effects of RASSF6 on sorafenib resistance or the underlying mechanism. Here, we show that RASSF6 expression positively correlates with sorafenib sensitivity in RCC cells and human samples. Stable ectopic overexpression of RASSF6 in RCC cell lines reduces resistance to sorafenib in vitro and in vivo. At a molecular level, RASSF6 activates the JNK signaling pathway, which further contributes to Mcl-1 inhibition. Suppression of the JNK pathway can partially restore Mcl-1 expression and sorafenib resistance. Together, these findings suggest that RASSF6 inhibits sorafenib resistance by repressing Mcl-1 through the JNK-dependent pathway. RASSF6 may serve as a novel regulator for sorafenib therapy in RCC.

This study aimed to examine expression and microstructural distribution of prestin in outer hair cells, and the effect of dose and time of radiation on prestin expression in the BALB/c mouse. We also investigated the molecular biological characteristics of prestin and possible mechanisms of sensorineural hearing loss caused by radiation. Seventy 4-week-old mice were randomly divided into four groups, including one control group and three experimental groups. Each experimental group was randomly divided into two groups, which were killed to collect specimens of the cochlea on the 3rd and 7th days after exposure to different doses of 8, 12, and 16 Gy radiation. These cochleas were embedded in paraffin, and then cut into sections. The sections were immunostained with anti-prestin antibodies. The distribution of prestin was observed under optical microscopy and the density of prestin-positive expression was quantitatively calculated by Image-Pro Plus. Prestin had high expression in the lateral membrane and low expression in the cytoplasm of outer hair cells above the nucleus. The density of prestin protein expression of the basal turn was not significantly different after exposure to the different doses of radiation compared with the control group, but up-regulation occurred after radiation in the apex turn. We conclude that prestin protein is mainly expressed in the lateral membrane above the nucleus. Prestin protein may be responsible for the mechanism of injury to the inner ear caused by radiation.

Background Cranial radiation therapy has been used for the treatment of primary and metastatic brain tumors. A prominent feature of brain injury induced by the radiation therapy is hippocampal dysfunction, characterized by a decline in memory. Cdk5 plays an important role in memory formation. Abnormal Cdk5 activity is associated with neuronal apoptosis induced by neurotoxic stimuli. However, the roles of Cdk5 in hippocampal apoptosis in response to X-ray irradiation have not been explored. Methods The expression of Cdk5 activators, p35 and p25, in hippocampal neurons was tested in both in vivo animal and in vitro couture after X-ray irradiation. Results After X-ray irradiation at 20 Gy and 30 Gy in rats, the number of hippocampal neuronal pyknosis was increased, but the number of hippocampal neuron was decreased, in the hippocampal CA1 region of rats. In these animals undergone with X-ray irradiation, the expression of p35 was significantly down-regulated, but it was up-regulated in p25. These opposite expressions were also shown in the primary cultured hippocampal neurons with 30 Gy irradiation. The apoptosis induced by X-ray irradiation were significantly prevented by the pretreatment of Cdk5 inhibitor, roscovitine, in both in vivo and in vitro settings. Conclusions X-ray irradiation resulted in a hippocampal neuronal apoptosis through up-regulation of p25, the Cdk5 activator. Hyperactivity of Cdk5 was involved in the pathogenesis of X-ray irradiation-induced hippocampal neuronal apoptosis. Blockade of Cdk5 signal pathway effectively protected neurons from the irradiation-induced brain injury.

To define the planning target volume (PTV) margins in intensity-modulated radiotherapy (IMRT) for prostate cancer without imaging guidance using B-mode acquisition and targeting (BAT) ultrasound-based prostate localization.Ten patients with prostate cancer underwent BAT ultrasound alignment before each IMRT session. The set-up deviations, each consisting of isocenter displacements in 3 directions (anterior-posterior, right-left lateral, and superior-inferior), were recorded for a total of 225 times and analyzed with Kolmogorov-Smimov (K-S) method.The isocenter shift in each direction, which represented an average from all the patients, was 3.56∓2.71 mm, 4.08∓3.99 mm, and 3.20∓2.92 mm in the lateral (RL), anteroposterior (AP), and superior-inferior (SI) dimensions, respectively, and the deviations in each direction conformed to a normal distribution (P=0.806, P=0.061, and P=0.106, respectively). In the absence of imaging guidance for IMRT for prostate cancer, the PTV margin should expand by 8.97 mm in the right, 1.87 mm in the left, 12.05 mm in the anterior, 3.91 mm in the posterior, 9.06 mm in the superior and 2.66 mm in the inferior to allow 95% isodose curve to cover 90% of the clinical target volume.The ultrasound imagining guided localization, with simple operation, nonirradiation and small systemic error, can be real-time corrected.

Objective: To describe in as much detail as possible the method for ablating the ventromedial shell of the nucleus accumbens (NAc) and investigate the efficacy and safety of the ablation treatment. Methods: Sixty-five patients with drug addictions received operations within the time frame from 2004 to 2009. The ablation targets were located in the bilateral medial posterior inferior shell of the NAc. Intraoperative electrophysiological monitoring was performed. Results: Tissue impedance in the shell of the NAc varied from 185 to 355 Ω. When stimulated with a low frequency (2 Hz) and a voltage above 3 V, 57 out of 65 (87.7%) patients experienced slight throbbing sensations. During the lesion procedure, fever was detected on the head and face of 59 patients (90.8%), the heart rate decreased in 19 cases (29.2%), and restlessness, irritability and hyperalgia were noted for all patients. Among the 65 patients, 52 (80%) no longer experienced a psychological craving for the drug. Conclusions: The shell of the NAc may be a promising surgical target for psychosurgery. Electrophysiological recordings revealed that the shell is indeed an appropriate structure.

To evaluate the effect of COX-2 silencing on the radiosensitivity of a nasopharyngeal carcinoma (NPC) cell line C666-1.Anti-COX-2 C666-1 cell line with COX-2 gene silencing mediated by shRNAmir lentiviral vector and the control cell line Anti-GL-2 C666-1 were exposed to various radiation doses. The clonogenic survival assay and curve fitting was used to calculate the radiobiological parameters and the sensitization enhancement ratio after the radiation. Cell cycle changes were assessed after the exposure by flow cytometric analysis. In a BALB/c nude mouse model, the growth curve of the xenografts was generated and the tumor growth inhibition rate was calculated.Compared with the control cells, Anti-COX-2 C666-1 cells showed obviously lowered values of SF2, D0 and Dq but significantly increased α/β with a sensitivity enhancement ratio of 1.4014. COX-2 gene silencing increased the inhibition rate of the tumor xenografts after the radiation, and caused also decreased percentage of G2/M arrest resulting from the exposure.Stable COX-2 silencing in NPC cells can improve the effect of radiotherapy both in vitro and in vivo. By changing the radiobiological parameters, genetically based COX-2 inhibitor may be a potentially promising radiosensitizer of NPC.

To investigate radiation-induced cell cycle changes of human breast cancer stem cells enriched by suspension culture.The tumorigenicity of human breast cancer stem cell line MCF-7 cultured in serum-free media was confirmed in NOD/SCID mice, and the radiosensitivity of the cells was tested by clone formation assay following radiation exposure. Flow cytometry was performed to evaluate radiation-induced cell cycle changes, and the protein expression of pCDC25C (ser216) was measured by Western blotting.After the exposure to 2 Gy radiation, the survived fraction of the cells in suspension culture and those in adherent culture was 0.856 ∓ 0.061 and 0.783 ∓ 0.097, respectively, and the cells in suspension culture showed an obviously greater capacity of tumorigenicity in NOD/SCID mice. The radiation exposure resulted in an obvious increase in the proportion of G2 phase cells from (22.03 ∓ 2.12)% to (45.83 ∓ 2.25)% and significantly increased the expression of pCDC25C (ser216).Radiation- induced G2 phase arrest may contribute to the resistance of the breast cancer stem cells to radiotherapy.

To study the protective effect of ginsenoside Rg1 on cultured rat hippocampal neurons against radiation injury and explore new therapies for preventing radiation encephalopathy.Rat hippocampal neurons cultured for 12 days were subjected to a single-dose X-ray exposure of 30 Gy. 4',6-diamidino-2-phenylindole (DAPI) staining was used to detect the neuronal apoptosis and NOS activity kit utilized to evaluate NOS activity in the cells after the exposure.Nuclear condensation was detected in (25.3-/+3.57)% of the neurons 24 h after 30 Gy X-ray exposure, a rate significantly higher than that in the control cells [(1.95-/+0.78)%, P0.01]. In the neurons pretreated with ginsenoside Rg1, only (7.43-/+1.51)% of the cells presented with nuclear condensation after the exposure, significantly different from the rates in the control cultures and the exposed cultures (P0.01). The NOS activity of exposed cultures was 6.46-/+0.95 U/ml, significantly higher than that in the control cultures (3.20-/+0.70 U/ml, P0.01). The NOS activity of the neurons pretreated with ginsenoside Rg1 was 3.85-/+0.69 U/ml, significantly different from that in the control cultures (P0.05) and the exposed cultures (P0.01).Ginsenoside Rg1 offers significant protective effect on rat hippocampal neurons from radiation-induced apoptosis by reducing the activity of NOS.

To determine the repair half-time (T1/2), a speed parameter of sub-lethal damage repair (SLDR), of human nasopharyngeal carcinoma (NPC) cell lines CNE1, HONE1, C666-1 and CNE2.A total radiation dose of 8 Gy divided into 4+4 Gy was delivered to the cell lines at the interval of 0 s, 15 s, 30 s, 1 h, 2 h, 4 h or 6 h. The cell survival fractions were determined using the standard cell clonogenic assay. The curves of the changes in the surviving cell fraction after a total dose of 8 Gy, as a function of the interval between the two doses of 4 Gy, were fitted manually, and the T1/2 of each cell line was calculated according to the curves.The T1/2 of CNE1, HONE1, C666-1 and CNE2 were 18 s, 22 s, 29 s and 27 s, respectively.The speed of SLDR of NPC cells is quite rapid, indicating that the fraction delivery time longer than 20 s might decrease the effect of radiotherapy.

To investigate the relationship between human multidrug resistancel gene (MDR1) polymorphisms and the radiosensitivity of nasopharyngeal carcinoma (NPC).Blood samples were collected from 59 NPC patients, who were devided into radiosensitive or radioresistant groups according to their responses to radiation therapy. The genotypes for MDR1 polymorphisms (G2677T in exon 21 and C3435T in exon 26) and their haplotypes were determined by PCR and restriction fragment length polymorphism analysis. The results were further confirmed by sequencing.The 3435CC genotype was associated with a significantly better response to radiotherapy than combined 3435 CT and TT genotype (P=0.026). The 2677GG genotype was also associated with a better response in comparison with combined 2677 GT and TT genotype, but this relation was not statistically significant. Patients with 2677G-3435C haplotype had a significant better response to radiotherapy than those with the other haplotypes (P=0.017).The MDR1 G2677T and C3435T polymorphisms may help predict the response to radiotherapy in NPC patients.

To silence annexin II gene expression by using small interference RNA (siRNA) in prostate cancer cell line PC3.For in vitro transcription, four sequences of 29-nucleotide DNA template oligonucleotides were designed, and one pair of the sequences were complementary to annexin II gene. The other pair was negative control. The 8 nucleotides at the 3' end of each oligonucleotide were complementary to the T7 Promoter Primer. The sense and antisense siRNA templates were transcribed by T7 RNA polymerase and the resulting RNA transcripts were hybridized to create dsRNA. The siRNA was transfected into prostate cancer cell PC3. For assaying the efficiency of siRNA, confocal microscopy, Northern blotting, and Western blotting were employed to examine the expression of annexin II protein and its mRNA. 3H thymidine was used to measure DNA synthesis.The siRNA sequence specific to annexin II gene was capable of inhibiting the expression of annexin II protein and its mRNA. And cellular DNA synthesis was significantly reduced in siRNA transfected cells.The protocol for the synthesis of siRNA by T7 RNA polymerase is feasible. Annexin II might be involved in DNA synthesis.

Temozolomide (TMZ) is an oral alkylating agent with established effects on the central nervous system of glioblastoma (GBM) patients. Clinical trials have demonstrated a significant impact on overall survival (OS) with TMZ. Ever since, several TMZ regimens have been designed to improve treat

To investigate protein kinase C (PKC) expression and its association with multidrug resistance (MDR) in KBV200 cells.KBV200 cells were preincubated with PKC activator phorbol-12-myristate-13-acetate (PMA, 200 nmol/L) and PKC activity was assayed by measurement of peptide substrate (32)P incorporation from [gamma-(32)P]ATP, with the cells without PMA preincubation serving as the control. Western blotting was performed for assessing the expression of PKC isoform, and the cell inhibition rate was evaluated by MTT assay.PMA preincubation of the cells significantly enhanced the activity of the total PKC and the membrane fraction, but lowered the PKC activity of the cytosol fraction, as compared with the cells without PMA treatment (P0.01). PKC-alpha expression was upregulated in the membrane fraction and down-regulated in the cytosol fraction in KBV200 cells after PMA preincubation. PKCbeta expression was slightly elevated in the cytosol fraction but exhibited no obvious changes in the membrane fraction after PMA pretreatment of the cells. The values of IC(50) of vincristine and adriamycin in PMA-treated cells were increased to 2275.5 nmol/L and 233.25 nmol/L, respectively (P0.01).PMA can increase the multidrug resistance of KBV200 cells, which suggests the possible involvement of PKC in the mechanism of multidrug resistance of tumor cells.

To observe the effects of functional inhibition of p-glycoprotein on radiosensitivity of drug-resistant MCF-7/Adr tumor cells.Flow cytometry was used to examine the dynamic changes of apoptosis rate and mitochondrial membrane potential (deltapsim) in verapamil-treated and untreated MCF-7/Adr cells after the X-ray exposure.The apoptotic rate of verapamil-treated cells was 25.53%+/-2.85%, 30.43%+/-2.21%, 39.03%+/-2.60% at 6, 12, and 24 h after X-ray exposure, respectively, and was 16.13%+/-1.16%, 21.73%+/-1.31%, and 27.53%+/-2.55% for the untreated cells. The mean fluorescence intensity of verapamil-treated cells was 75.27+/-4.90, 96.47+/-5.59, 57.77+/-2.55, respectively, at the corresponding time points, in comparison with the intensity of 54.17+/-4.05, 62.30+/-5.93, and 39.53+/-2.65 for the untreated cells. The apoptosis rate and deltapsim of the treated cells were significantly higher than those in the untreated cells at each of the specified time point (P0.01), and in the former cells, the apoptosis rate reached the maximum at 24 h (F=47.870, P=0.000) and the deltapsim at 12 h after X-ray exposure (F=74.485, P=0.000).The radiosensitivity of MCF-7/Adr cells is increased after functional inhibition of p-glycoprotein, possibly in relation to the alteration of deltapsim.

To examine the changes in the function and expression of multidrug resistance gene (mdr1) and P-gly-coprotein (P-gp) in nasopharyngeal carcinoma (NPC) CNE1 cell following irradiation for determining the sequential order of radiotherapy and chemotherapy in the treatment of NPC.The expressions of mdr1 gene and its protein P-gp as well as the function of P-gp efflux were examined in CNE1 cells before and after irradiation exposure by reverse transcriptional polymerase chain reaction (RT-PCR), Western blotting and flow cytometry, respectively.Irradiation of CNE1 cells induced a long-term overexpression of mdr1 gene and P-gp and reduction in intracellular daunorubicin accumulation.Irradiation decreases the chemotherapy sensitivity of CNE1 cell, and induction chemotherapy should be therefore performed before radiotherapy in the treatment of advanced NPC.

To investigate the association of protein kinase C (PKC) isoforms and multidrug resistance (MDR) mechanism in KBV200 cells.Western blotting was utilized to examine the expression and subcellular distribution of PKC isoforms were measured in KBV200 cells with MDR and drug-sensitive KB cells, and the fluorescence intensity of PKC isoforms was detected by flow cytometry (FCM).KBV200 cells possessed higher PKC activities, with increased percentage of membrane fraction. As compared with parental KB cells, the expression of PKCalpha was significantly increased in KBV200 cells, while PKCbeta and epsilon expressions remained unchanged, and PKCgamma and zeta failed to be detected. Fluorescence intensity of PKCalpha in KBV200 cells was increased.PKC might contribute to MDR phenotype in KBV200 cells, and of the isoforms so far detected, PKCalpha might play an important role in MDR phenotype.

To investigate the relationship between protein kinase C (PKC) and multidrug resistance (MDR) in cancer cell line KBV200.MTT assay was used to evaluate the IC50 of vincristine (VCR) and adriamycin (ADR) in KB cell line and its VCR-resistant derivative KBV200 cells. PKC activities in the 2 cell lines were assayed by measuring the incorporation of (32)P from [gamma-(32)P] ATP into the peptide substrates.The IC50 values of VCR and ADR in KBV200 cells was 64.03 and 18.8 folds greater than those in KB cells. PKC activities of the membrane and cytosol fraction in KBV200 cells were increased compared with that in KB cells, with the total PKC activity 1.12-fold higher. Phorbol-12-myristate-13 -acetate increased PKC activity of the membrane fraction and IC50 values of KBV200 cells, while staurosporine worked to the opposite effects.PKC may contribute to MDR mechanism in KBV200 cells.

To investigate the expression of c-myc in drug-resistant MCF-7/Adr human breast cancer cells and the counteractive effect of c-myc antisense oligonucleotide on their drug-resistance.Flow cytometry was performed to examine c-myc expression in multi-drug resistant MCF-7/Adr cell line and its parental cell line MCF-7. The IC50 value of doxorubicin was evaluated by MTT assay.MCF-7/Adr cell line was shown to have a significantly higher expression rate of c-myc than its parent cell line MCF-7 (70.48% vs 46.02%). The IC50 value of doxorubicin was (22.00+/-1.92) micomol/L in MCF-7/Adr cells, which was significantly decreased to (9.60+/-1.04) micromol/L (P0.05) after coincubation with 4 micromol/L c-myc antisense oligonecleotide.c-myc expression is up-regulated in MCF-7/Adr cells as compared with their parent cell line MCF-7. Inhibition of c-myc expression may partially reverse the resistance of MCF-7/Adr against doxorubicin, suggesting that c-myc may be involved in the mechanism of drug-resistance of tumor cells.