DNA-dependent protein kinase activity and radiosensitivity of nasopharyngeal carcinoma cell lines CNE1/CNE2.

The present study investigated the relationship between DNA-dependent protein kinase (DNA-PK) and radiosensitivity of nasopharyngeal carcinoma (NPC) cell lines. The dose-survival relationship for NPC cell lines, CNE1 and CNE2, was analyzed using clonogenic formation assay, the activity of DNA-PK of the two cell lines was measured using the Signa TECT DNA-PK assay kit, and the localization and expression of Kus (a heterodimer) and DNA-PKcs protein in CNE1 and CNE2 before irradiation and 15 min, 1 h, 6 h, 12 h, 24 h after 4 Gy irradiation were analyzed by immunofluorescence, laser scanning confocal microscope (LSCM) and Western blot. The results showed that the surviving fraction of CNE1 was higher than that of CNE2 at each dose. The DNA-PK activity of CNE1 was also significantly higher than that of CNE2 before and after irradiation (P<0.05), while the expression of total Ku70/Ku80 in CNE1 and CNE2 had no significant difference. Increasing translocation of Ku70 and Ku80 from the cytoplasm to the nuclei in the two cell lines was observed with increase of irradiation time as detected by Western blot, and the immunofluorescence of the DNA-PK complex subunits showed greater nuclear translocation in CNE1 than CNE2 after irradiation. The results suggest that the relatively higher radio-resistance of CNE1 correlates with the higher activity of DNA-PK as compared to that of more radiosensitive CNE2 (or lower radio-resistance) before and after irradiation. Thus, DNA-PK activity may be a useful predictor of radiosensitivity of NPC.

[Correlation of DNA-PK activity with anti-cancer drug-sensitivity in human gliomas].

OBJECTIVE: To investigate the relationship between DNA-dependent protein kinase (DNA-PK) activity and anti-cancer drug sensitivity in human glioma tissues. METHODS: Human glioma specimens were primarily cultured and its sensitivity to several anti-cancer drugs were evaluated by MTT assay. Nuclear protein was extracted from the glioma sample of the same patient and its DNA-PK activity was determined by a biotinylated DNA-PK assay with p53-derived peptide as a specific substrate. RESULTS: DNA-PK activity varied widely among these glioma samples. Of all 36 samples, 16 showed higher DNA-PK activity (relative activity > or = 0.40) and 20 samples with lower DNA-PK activity (relative activity < 0.40). The gliomas sensitive to DDP and VCR as evaluated by inhibition rate (IR > or = 50%) under plasma peak concentration (PPC) showed lower DNA-PK activity than the resistant ones (IR < 50%) (t = -3.445, P < 0.01). Furthermore, the gliomas with higher DNA-PK activity showed lower inhibition rate (IR < 50%) than those with lower DNA-PK activity ones (t = -2.145, P < 0.05). CONCLUSION: DNA-PK activity is significantly associated with anti-cancer drug sensitivity to DDP and VCR in human gliomas. DNA-PK activity could be used as a new biomarker for the chemotherapy sensitivity of human gliomas.

Overexpression of IL-7 enhances cisplatin resistance in glioma.

Cisplatin is one of the most commonly used chemotherapeutic agents for glioma patients. In this study, array comparative genomic hybridization (aCGH) was used to identify genes associated with cisplatin resistance in a human glioma cell line. The cisplatin-resistant U251/CP2 cell line was derived by stepwise selection using cisplatin. The genetic aberrations of the U251 parental cell line and the U251/CP2 cells were analyzed using aCGH. RT-PCR was used to detect the expression of the altered genes revealed by aCGH. The sensitivity of glioma cells to cisplatin was determined by using the MTT assay. Apoptosis was detected using flow cytometry and western blot analysis. The IC 50 value of cisplatin in U251/CP2 cells was five times higher than its IC 50 in U251 cells. The U251 cells lost at least one copy each of the CFHR1 and CFHR3 genes, and both CFHR1 and CFHR3 were homozygously deleted in U251/CP2 cells. The U251/CP2 cells gained two to three copies of C8orf70 and IL-7 genes. IL-7 mRNA expression was studied in 12 glioma cell lines, and expression was positively correlated with the IC 50 of cisplatin. Furthermore, IL-7 mRNA expression was also positively correlated with the IC 50 of cisplatin in 91 clinical glioma specimens. Additionally, treatment with recombinant human IL-7 (rhIL-7) enhanced cisplatin resistance and increased the relative growth rate of the glioma cells. Moreover, the apoptosis induced by cisplatin could be inhibited by IL-7. In conclusion, our results suggest that IL-7 may play an important role in cisplatin resistance in glioma.

Glioblastoma stem cells resistant to temozolomide-induced autophagy.

BACKGROUND: Recent studies have demonstrated the existence of a small fraction of cells with features of primitive neural progenitor cells and tumor-initiating function in brain tumors. These cells might represent primary therapeutic target for complete eradication of the tumors. This study aimed to determine the resistant phenotype of glioblastoma stem cells (GSCs) to temozolomide (TMZ) and to explore the possible molecular mechanisms underlying TMZ resistance. METHODS: Freshly resected glioblastoma specimen was collected and magnetic isolation of GSCs was carried out using the Miltenyi Biotec CD133 Cell Isolation kit. The cytotoxic effect of TMZ on CD133(+) and CD133(-) glioblastoma cells was determined by using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Autophagy-related proteins (Beclin-1, LC3 and Atg5) and cleaved caspase-3 (p17) were analyzed by Western blotting. Immunofluorescent staining was used to detect Atg5, glial fibrillary acidic protein (GFAP) and CD133 expression in glioblastoma cells. Statistical analysis was carried out using SPSS 10.0 software. For all tests, the level of statistical significance was set at P < 0.05. RESULTS: CD133(+) glioblastoma cells exhibited neurosphere-like growth in vitro and high expression of CD133 stem cell marker. The growth-inhibiting rate in CD133(-) glioblastoma cells treated with 5 or 50 micromol/L TMZ was significantly higher than that in CD133(+) glioblastoma cells ((14.36 +/- 3.75)% vs (2.54 +/- 1.36)% or (25.95 +/- 5.25)% vs (2.72 +/- 1.84)%, respectively, P < 0.05). Atg5, LC3-II and Beclin-1 levels were significantly lower in CD133(+) glioblastoma cells than those in autologous CD133(-) cells after TMZ treatment (P < 0.05). Caspase-3 was mildly activated only in CD133(-) glioblastoma cells after exposure to TMZ (P < 0.05). Immunofluorescent staining revealed elevated expression of Atg5 in GFAP(+) cells following TMZ treatment. CONCLUSIONS: The GSCs display strong capability of tumor's resistance to TMZ. This resistance is probably contributed by the CD133(+) cells with down-regulation of autophagy-related proteins. Future treatment should target this small population of cancer stem cells in tumors to improve survival of patients.

Activities of DNA-PK and Ku86, but not Ku70, may predict sensitivity to cisplatin in human gliomas.

OBJECTIVE: This study was designed to investigate the relationship between activities of DNA-dependent protein kinase (DNA-PK), its subunits Ku86/Ku70, and sensitivities to cisplatin in human glioma samples. METHODS: Thirty-six glioma samples from patients without prior treatment before neurosurgery were included in this study. The sensitivities to cisplatin as indicated by IC(50) (the inhibitory concentration leading to 50% cell death) were assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenytetrazolium (MTT) assay; activities of DNA-PK and Ku70/Ku86 were analyzed by SigmaTECT DNA-Dependent Protein Kinase Assay System and Ku70/Ku86 DNA Repair Kit, respectively. RESULTS: Sensitivities to cisplatin correlated with the activities of DNA-PK/Ku86, but not with the Ku70 or other clinical parameters such as age, sex of the patients, pathological gradings of the tumors, or tumor size. The levels of DNA-PK activities also associated with pathological grading and Ku86, but not with other clinical parameters. The tumors of the patients who failed to respond to cisplatin-based chemotherapy tended to display higher activity levels of DNA-PK and Ku86. Furthermore, platinum-based chemotherapy did not result in significant changes of DNA-PK/Ku activities in four matched samples before and after chemotherapy. CONCLUSION: Pretreatment determination of DNA-PK/Ku86 activities might be helpful in identifying patients who will actually benefit from platinum-based treatment.

[Predictive value of in vitro MTT assay chemosensitivity test of cytotoxic drug activity in cervical cancer].

BACKGROUND & OBJECTIVE: In recent years, the neoadjuvant chemotherapy for cervical cancer has evoked more and more attention and has been used widely. But the chemosensitivity of individuals to various antitumor drugs is different. This study was to investigate the chemosensitivity of cervical cancer cells to antitumor drugs using in vitro MTT assay chemosensitivity test. METHODS: The sensitivity of fresh human cervical cancer cells from 32 patients to 9 cytotoxic drugs was tested using in vitro MTT assay. RESULTS: The cytotoxic activities of the 9 drugs for cervical cancer were in sequence from high to low as follows: liposomal paclitaxel, taxol, carboplatin (CBP), ifosfamide (IFO), etoposide (VP-16), 5-fluorouracil (5-FU), cisplatin (DDP), bleomycin (BLM), and cyclophosphamide (CTX). Generally, cervical cancer cells were more sensitive to paclitaxel, taxol, and CBP than to other drugs (P<0.05) with inhibition rates of 56.56%, 55.66%, and 46.81%, respectively. Stage Ib1 cervical cancer cells were more sensitive to taxol, paclitaxel, and CBP than to other drugs with inhibition rates of 58.71%, 53.00%, and 49.25%, respectively; stage Ib2 cervical cancer cells were more sensitive to paclitaxel and taxol than to other drugs with inhibition rates of 65.26% and 50.06%. Both moderately and poorly differentiated squamous cell cancer cells were more sensitive to taxol, paclitaxel, and CBP than to other drugs with inhibition rates of 52.01%, 49.21%, and 40.02% for the former, and 60.02%, 61.16%, and 48.75% for the latter. CONCLUSIONS: MTT assay, a sensitive and widely used chemosensitivity testing method, is helpful in sensitive drug screening and neoadjuvant chemotherapy regimen selection for cervical cancer. Cervical cancer cells are more sensitive to paclitaxel, taxol, and CBP than to other tested drugs in this study.

[Individualized chemotherapy based on drug sensitivity and resistance assay and MGMT protein expression for patients with malignant glioma--analysis of 42 cases].

BACKGROUND & OBJECTIVE: Malignant glioma cells are resistant to most chemotherapeutic agents. Nitrosourea and temozolomide (TMZ) are main agents for treating malignant glioma. Resistance of malignant glioma to these agents is frequently associated with high levels of DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). This study was to evaluate the efficacy of individualized chemotherapy, according to chemotherapy sensitivity and resistance assays (CSRAs) and MGMT expression pattern, on malignant glioma, and observe the adverse events. METHODS: The pathologically confirmed malignant glioma patients, treated by operation at Cancer Center of Sun Yat-sen University from Dec. 2001 to Feb. 2006, were enrolled. The fresh tumor tissues obtained during operation were immediately sent for CSRAs using MTT assay. The expression of MGMT protein was detected by immunohistochemistry. After radiotherapy,the patients received chemotherapy according to the results of CSRAs and MGMT expression. The patients were evaluated for response to chemotherapy according to WHO criteria, and for toxicity according to National Cancer Institute (NCI) criteria. RESULTS: Forty-two patients were evaluated for response to chemotherapy. Seven patients received 2 chemotherapy regimens consecutively, therefore, overall 49 cases were evaluable. Of the 49 cases, 6 (12%) achieved complete remission (CR), 10 (20%) achieved partial remission (PR), 20 (41%) had stable disease (SD), and 13 (27%) had progressive disease (PD). The objective response rate (CR and PR) was 33%, and the disease control rate (CR, PR, and SD) was 73%. Hematologic toxicities were the main adverse events observed in this study, included grade IV anemia (1%), grade III-IV leukopenia (28%), and grade III-IV thrombocytopenia (8%). Non-hematologic toxicities mainly included nausea/vomit, fatigue, and alopecia. CONCLUSION: Individualized chemotherapy based on in vitro CSRAs and MGMT expression for patients with malignant glioma could improve overall response rate.