Mechanism of double-base lesion bypass catalyzed by a Y-family DNA polymerase

As a widely used anticancer drug, cis-diamminedichloroplatinum(II) (cisplatin) reacts with adjacent purine bases in DNA to form predominantly cis-[Pt(NH3)2{d(GpG)-N7(1),-N7(2)}] intrastrand cross-links. Drug resistance, one of the major limitations of cisplatin therapy, is partially due to the inherent ability of human Y-family DNA polymerases to perform translesion synthesis in the presence of DNA-distorting damage such as cisplatin–DNA adducts. To better understand the mechanistic basis of translesion synthesis contributing to cisplatin resistance, this study investigated the bypass of a single, site-specifically placed cisplatin-d(GpG) adduct by a model Y-family DNA polymerase, Sulfolobus solfataricus DNA polymerase IV (Dpo4). Dpo4 was able to bypass this double-base lesion, although, the incorporation efficiency of dCTP opposite the first and second cross-linked guanine bases was decreased by 72- and 860-fold, respectively. Moreover, the fidelity at the lesion decreased up to two orders of magnitude. The cisplatin-d(GpG) adduct affected six downstream nucleotide incorporations, but interestingly the fidelity was essentially unaltered. Biphasic kinetic analysis supported a universal kinetic mechanism for the bypass of DNA lesions catalyzed by various translesion DNA polymerases. In conclusion, if human Y-family DNA polymerases adhere to this bypass mechanism, then translesion synthesis by these error-prone enzymes is likely accountable for cisplatin resistance observed in cancer patients

Multicenter phase II study of docetaxel plus oxaliplatin combination chemotherapy in patients with advanced gastric cancer: Daegu Gyeongbuk Oncology Group

The present study was conducted to evaluate the efficacy and safety of a combination regimen of docetaxel plus oxaliplatin in patients with advanced gastric cancer. Patients with previously untreated metastatic or recurrent, measurable gastric cancer received intravenous docetaxel 65 mg m−2 plus oxaliplatin 120 mg m−2 on day 1 based on a 3-week cycle. Forty-two patients were enrolled in the current study, among whom 39 were assessable for efficacy and all assessable for toxicity. One complete response and 18 partial responses were confirmed, giving an overall response rate of 45.2% (95% confidence interval (CI); 31.7–59.7%). At a median follow-up of 7.7 months, the median time to progression and median overall survival was 5.7 (95% CI; 4.3–7.2) months and 9.9 (95% CI; 7.8–12.0) months, respectively. Grade 3/4 neutropenia occurred in 11 patients (26.1%) and febrile neutropenia was observed in four patients (9.5%). The common non-haematologic toxicity was fatigue (grade 1/2, 61.9%) and nausea (grade 1/2, 47.7%). The combination of docetaxel and oxaliplatin was found to be well tolerated and effective in patients with advanced gastric cancer

Επίδραση των φυσικών και γεωμετρικών χαρακτηριστικών των αδρανών στις ιδιότητες των κονιαμάτων

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