HTERT gene expression levels and telomerase activity in drug resistant MCF-7 cells

Cancer cells and some highly proliferative normal cells can stabilize telomere lengths by telomerase, which adds hexameric repeats to the ends of linear chromosomes. In this study, the activity of telomerase reverse transcriptase (hTERT) and its gene expression levels were investigated in paclitaxel, docetaxel, vincristine and doxorubicin resistant human MCF-7 breast adenocarcinoma cells. Materials and Methods: Resistant cell lines were developed by stepwise selection of cells (MCF-7/S) in increasing doses of paclitaxel (MCF-7/Pac), docetaxel (MCF-7/Doc), vincristine (MCF-7/Vinc) and doxorubicin (MCF-7/Dox). Antiproliferative effects of anticancer drugs were evaluated by XTT assay and IC50 values for different drugs were determined from cell proliferation curves. Expression levels of hTERT gene in sensitive and resistant cells were analyzed by RT-PCR. TRAP-Silver Staining assay was used to evaluate telomerase activities in these cells. Results: When drug resistant and sensitive MCF-7 cells were compared no significant differences were observed in hTERT expression levels and telomerase enzyme activities. Conclusion: This report demonstrates that drug resistance developed against paclitaxel, docetaxel, vincristine and doxorubicin in MCF-7 cells is independent of the expression of hTERT gene and telomerase activity.В опухолевых клетках, а также некоторых нормальных клетках с высоким пролиферативным потенциалом длина теломеров может стабилизироваться за счет фермента теломеразы, добавляющего гексамерные повторы к концам линейных хромосом. Цель: проанализировать активность обратной транскриптазы теломеразного комплекса и экспрессию гена теломеразы в клетках MCF-7 аденокарциномы молочной железы человека, устойчивых к паклитакселу, доцетакселу, винкристину и доксорубицину. Материалы и методы: сублинии клеток MCF-7, обладающих лекарственной резистентностью, были полу- MCF-7, обладающих лекарственной резистентностью, были полу -7, обладающих лекарственной резистентностью, были получены путем селекции исходных клеток при культивировании их в присутствии возрастающих доз паклитаксела (MCF-7/Pac), доцетаксела (MCF-7/Doc), винкристина (MCF-7/Vinc) и доксорубицина (MCF-7/Dox). Антипролиферативный эффект противоопухолевых препаратов определяли в ХТТ-тесте. Величины IC50 для различных препаратов определяли по кривым пролиферации клеток. Уровень экспрессии гена hTERT в чувствительных и резистентных клетках анализировали методом ОТ-ПЦР. Теломеразную активность определяли с помощью набора TRAPeze. Результаты: проанализированные резистентные линии клеток MCF-7 не отличались от исходной линии ни по уровню экспрессии гена hTERT, ни по уровню теломеразной активности. Выводы: развитие лекарственной резистентности к паклитакселу, доцетакселу, винкристину и доксорубицину в клетках MCF-7 не связано с изменениями экпрессии гена hTERT или уровня теломеразной активности в них

An improved quantitative detection of telomerase activity in cervical and endometrial carcinoma

31st Congress of the Federation-of-European-Biochemical-Societies (FEBS) -- JUN 24-29, 2006 -- Istanbul, TURKEYWOS: 000238914001243…Federat European Biochem So

The protective role of melatonin in experimental hypoxic brain damage

Background: It is known that oxygen-derived free radicals play an important role in the pathogenesis of brain injury. Melatonin is a powerful scavenger of the oxygen free radicals. In this study, the protective effect of melatonin against the damage inflicted by reactive oxygen species during brain hypoxia was investigated in newborn rats using biochemical parameters

Synergistic effects of ion transporter and MAP kinase pathway inhibitors in melanoma

New therapies are required for melanoma. Here, we report that multiple cardiac glycosides, including digitoxin and digoxin, are significantly more toxic to human melanoma cells than normal human cells. This reflects on-target inhibition of the ATP1A1 Na(+)/K(+) pump, which is highly expressed by melanoma. MEK inhibitor and/or BRAF inhibitor additively or synergistically combined with digitoxin to induce cell death, inhibiting growth of patient-derived melanomas in NSG mice and synergistically extending survival. MEK inhibitor and digitoxin do not induce cell death in human melanocytes or haematopoietic cells in NSG mice. In melanoma, MEK inhibitor reduces ERK phosphorylation, while digitoxin disrupts ion gradients, altering plasma membrane and mitochondrial membrane potentials. MEK inhibitor and digitoxin together cause intracellular acidification, mitochondrial calcium dysregulation and ATP depletion in melanoma cells but not in normal cells. The disruption of ion homoeostasis in cancer cells can thus synergize with targeted agents to promote tumour regression in vivo