The role of apoptotic cell death in the radiosensitising effect of gemcitabine

Abstract

BACKGROUND: The aim of this study was to evaluate the radiosensitising effect of gemcitabine, in terms of cell-cycle progression, induction of apoptosis, and to investigate the molecular events regulating apoptosis. METHODS: Tumour cells were treated with gemcitabine, radiation, or the combination. 0 -72 h after treatment, cells were collected for cell-cycle analysis and apoptosis determination. Caspase 8 and 9, Bid and tBid expression were determined by western blot. The mitochondrial membrane potential was determined using flow cytometry. An RT 2 Profiler PCR Array for human apoptotic genes was performed after the combination or TRAIL treatment. RESULTS: Gemcitabine and radiation resulted in an early S-phase block immediately after treatment, after which the cells moved synchronously through the cell cycle. When cell-cycle distribution returned to pre-treatment levels, an increased induction of apoptosis was observed with activation of caspase 8 and 9 and a reduction of the mitochondrial membrane potential. Gene expression after treatment with radiosensitising conditions was comparable with expression after the TRAIL treatment. CONCLUSION: A role for the cell-cycle perturbations and the induction of apoptosis could be attributed to the radiosensitising effect of gemcitabine. Apoptosis induction was comparable with the apoptotic pathway observed after the TRAIL treatment, that is the involvement of the extrinsic apoptosis pathway.

PTK6 Potentiates Gemcitabine-Induced Apoptosis by Prolonging S-phase and Enhancing DNA Damage in Pancreatic Cancer

“…However, many cancer cells including the pancreatic cancer cells we tested here have p53 mutations or deletions and we suspected that an alternative apoptotic signal pathway, the "extrinsic" pathway, initiated by Caspase-8 activation might regulate gemcitabine-induced apoptosis in pancreatic cancer. Pauwels demonstrated that gene expression patterns in apoptotic signaling changed similarly in pancreatic cancer cell lines exposed to gemcitabine and radiation to the changes observed after treatment with TRAIL, which activates the "extrinsic" apoptotic pathway (34). Our study clearly indicated that PTK6-regulated gemcitabine-induced apoptosis requires Caspase-8 and suggests the importance of the extrinsic apoptotic pathway in pancreatic cancer.…”

Gemcitabine-Based Chemoradiation in the Treatment of Locally Advanced Head and Neck Cancer: Systematic Review of Literature and Meta-Analysis

“…dFdCTP directly interferes with DNA synthesis in tumor cells through inhibition of DNA polymerization and incorporation of the fraudulent nucleotide into the growing DNA strand [31]. Finally, gemcitabine can be incorporated into RNA and can induce apoptosis [24,32].…”

“…In addition, it has synergistic activity with cisplatin and radiosensitizing properties [23][24][25][26][27][28][29]. Gemcitabine as a prodrug requires intracellular activation by phosphorylation to gemcitabine diphosphate (dFdCDP) and gemcitabine triphosphate (dFdCTP) for its antitumor activity [30].…”

Difluorodeoxyuridine plasma concentrations after low-dose gemcitabine during chemoradiation in head and neck cancer patients

“…In addition to its cytotoxic effects, gemcitabine has potent radiosensitizing properties, as shown both in preclinical and clinical settings, with in vitro radioenhancement factors up to three, depending upon schedule and concentration (8). The current evidence suggests that accumulation in the S phase of the cell cycle, depletion of dATP pools, reduction of apoptotic threshold, inhibition of DNA synthesis and reduction of DNA repair might contribute to, or might even be essential for gemcitabine-mediated radiosensitization (9)(10)(11)(12)(13).…”