Radioresistance in a tumour cell line correlates with radiation inducible Ku 70/80 end-binding activity.

PURPOSE: The aims of the present study were to better understand the role of Ku 80, which is involved in double-strand break repair in mammalian cells in the mechanism of radiation resistance and to verify the possibility of increasing cell radiosensitivity by targeted inhibition of Ku autoantigen 80 (Ku 80). MATERIALS AND METHODS: Western blot and electrophoretic mobility shift assay (EMSA) were performed on the human bladder carcinoma cell line RT112 (radioresistant) and on the human colorectal carcinoma cell line SW48 (radiosensitive) to assess the expression levels of DNA-dependent protein kinase (DNA-PK) components and the DNA-binding activity of the Ku 70/80 heterodimer after exposure to radiation, respectively. Ku 80 silencing was carried out with the use of small interfering RNA (siRNA). RESULTS: Greater differences in the DNA-binding activity of Ku 70/80 and Ku 80 phosphorylation level were observed in RT112 as compared to SW48 after X-ray treatment. There is no correlation between Ku expression and DNA-binding activity at lower doses. A significant increase in nuclear Ku 80 expression was observed one hour after the exposure, only at the higher doses, while the DNA-PK catalytic subunits (DNA-PKcs) and Ku 70 levels did not change significantly. Inhibition of Ku 80 expression by siRNA induced radiosensitivity in the RT112 cell line. CONCLUSIONS: Our data demonstrate that in a bladder tumour cell line up-regulation of Ku end-binding activity without any marked change in Ku expression underlie radiation resistance.

Conservative treatment of invasive bladder carcinoma by transurethral resection, protracted intravenous infusion chemotherapy, and hyperfractionated radiotherapy: long term results.

BACKGROUND: Organ preservation has been investigated in patients with muscle-invasive bladder carcinoma over the past decades as an alternative to radical cystectomy. The majority of studies reported that trimodal schedules, including transurethral resection of bladder tumor (TURB), radiotherapy (RT), and chemotherapy, are a feasible and safe organ-sparing approach without deferring the survival probability. However, to the authors' knowledge the best combination of RT and chemotherapy has yet to be well defined. The current study evaluated the long-term results of a schedule of concurrent cisplatin and 5-fluorouracil (5-FU) administered as protracted intravenous infusions (PVI) during hyperfractionated radiotherapy (HFRT) with organ-sparing intent in patients with infiltrating transitional cell carcinoma of the bladder (TCCB). METHODS: Seventy-seven patients with a classification of T2-T4aN0M0 TCCB were enrolled in the current study. After a complete TURB and bladder mapping, 42 of 77 patients underwent 2 cycles of induction chemotherapy. All 77 patients underwent HFRT and a schedule of cisplatin (4-6 mg/m(2) per day) and 5-FU (180-220 mg/m(2) per day) as concomitant PVI (radiochemotherapy [RCT]). Six to 8 weeks after RCT, patient response was evaluated by computed tomography scan, urine cytology, and TURB. Patients who achieved a complete response (CR) were followed at regular intervals. For patients with residual or recurrent invasive tumor, salvage cystectomy was recommended. RESULTS: Seventy-two patients were evaluable for response: 65 achieved a CR (90.3%) and 7 (9.7%) achieved a partial response. No significant difference was observed for the different prognostic factors with the exception of stage of disease (T2 [95.7%] vs. T3-T4a [80.0%]; P = 0.04). The observed toxicity, mainly hematologic, was higher among the patients who received induction chemotherapy compared with the patients who did not receive induction chemotherapy, even though the difference was not statistically significant. After a median follow-up of 82.2 months (range, 30-138 months), 44 of 65 (57.1%) patients who achieved a CR were alive. Of these 44 patients, 33 had tumor-free bladders. The 5-year overall, bladder-intact, tumor-specific, disease-free, and cystectomy-free survival rates for all 77 patients were 58.5%, 46.6%, 75.0%, 53.5%, and 76.1%, respectively. No associations were observed in overall and tumor-specific survival with different prognostic factors. CONCLUSIONS: Combined treatment appeared to provide high response rates and can be offered as an alternative option to radical cystectomy in selected patients who refuse or are unsuitable for surgery.

Accelerated hyperfractionated radiotherapy and concurrent protracted venous infusion chemotherapy in locally advanced head and neck cancer.

Concurrent radiotherapy and chemotherapy result in a significant benefit with respect to induction chemotherapy followed by radiotherapy or radiotherapy alone, although with a significant increase of toxicity. To discover a more tolerated and effective chemoradiation regimen, the feasibility and efficacy of a hyperfractionated accelerated irradiation with concurrent protracted venous infusion chemotherapy was investigated. Sixty-five patients with advanced head and neck cancer underwent a definitive (53 patients) or a postoperative adjuvant (12 patients) chemoradiation treatment. Chemotherapy consisted of an intravenous protracted infusion of 5 and 200 mg/m /d cisplatin and 5-fluorouracil, respectively. Radiotherapy consisted of a split-course accelerated hyperfractionation of two 150-cGy (split twice a day) or three 100-cGy fractions per day (split three times a day) at more than 6-hour intervals, for 2 weeks followed, after a 1-week interruption, by 2-to-3-week treatment, with the same fractionation schedule, to a total dose of 60 Gy to 69 Gy. Confluent mucositis was tolerable and was the cause of treatment delay of more than 10 days in only 20% of patients. Grade 3 or greater systemic toxicity occurred only in 9 of 65 (14%) patients and was never the cause of drug dose reduction. Complete responses were observed in 69% of patients with gross diseases. At a median follow-up of 43.5 months, 45% of patients were alive and free of disease and 38% died of cancer. The 5-year actuarial local regional failure was 35%. The 5-year actuarial disease-specific survival was 50%. Preservation of larynx function was achieved in 47% of living patients and in 74% of all patients, with advanced tumors of the laryngopharynx. The long-term results of this study suggest that this chemoradiation regimen has the potential of achieving a significant improvement over standard therapy while avoiding significant toxicity.

Radiosensitization by oxaliplatin in a mouse adenocarcinoma: influence of treatment schedule.

PURPOSE: The aim of our study was to investigate if oxaliplatin (1-OHP) could be used as a radiosensitizer in vivo. MATERIALS AND METHODS: Experiments were performed in mice (C3D2F1) bearing a transplanted mammary carcinoma in a foot. Drugs, 1-OHP and cis-diammine-dichloro-platinum (CDDP), were administered i.p. Results were analyzed in terms of tumor growth delay (TGD). RESULTS: 1-OHP and CDDP were tested in single doses of 6 and 10 mg/kg body weight. Administration of either 1-OHP or CDDP produced a significant TGD but only with the dose of 10 mg/kg. Single dose combined X-ray (10 Gy) and 1-OHP (6 and 10 mg/kg) treatments were performed with different sequences and time intervals (1 h, 4 h, and 24 h). All TGDs of these combined treatments were uniform among themselves (indicating that sequence and time interval did not influence the results), and did not depend on the drug dose. In X-ray (10 and 20 Gy) and 1-OHP (6 and 10 mg/kg) combined treatment, the TGDs increased only with X-ray dose. Different 1-OHP administration schedules were performed for fractionated experiments: two treatments every 4 days. The least toxic protocol (1-OHP total dose from 6 to 14 mg/kg) was selected for combined treatments with 10 daily X-ray treatments of 2 Gy. A clear drug dose-effect relationship was observed in those treatments with 1-OHP doses from 10 to 14 mg/kg. CONCLUSION: Although low-dose 1-OHP did not induce a TGD when administered alone, in combined protocols it increased X-ray efficacy.