Gefitinib enhances the effects of combined radiotherapy and 5-fluorouracil in a colorectal cancer cell line.

PURPOSE: In a phase I/II trial, patients with locally advanced rectal cancer received preoperative radiotherapy (RT) and concurrent with 5-fluorouracil (5-FU) and gefitinib. Results were promising. To elucidate the molecular and biological effects, we replicated the schedule in the LoVo human colorectal adenocarcinoma cell line. METHODS: RT (2 Gy daily for 3 days), 5-FU (0.3, 0.6, 1.25, 2.5, 5, 10 µM) and gefitinib (0.2, 0.4, 0.8 µM) were administered alone, in double combinations and all together. We assessed viable cells, cell cycle, cyclin, p53 and p21 expression, signalling pathways by means of phosphorylated epidermal growth factor receptor (p-EGFR), p-AKT and p-ERK 1-2 and clonogenic capacity. RESULTS: RT and 5-FU were cytotoxic. Gefitinib was cytostatic. RT reduced clonogenic capacity more than 5-FU. 5-FU induced more cell death than RT, but surviving cells were proliferative (cyclins and p-EGFR increased). 5-FU + RT had a synergistic effect. Gefitinib, enhancing G1 accumulation, reduced proliferation of cells surviving 5-FU and 5-FU + RT. It slightly increased the cytotoxicity of RT and 5-FU. CONCLUSIONS: As gefitinib limited the proliferation rate of cells surviving 5-FU and 5-FU + RT in the LoVo cell line, it may be a useful addition to chemotherapy and RT in rectal cancer patients.

Exploring the radiosensitizing potential of AZD8931: a pilot study on the human LoVo colorectal cancer cell line.

AIM: To explore the radiosensitizing effect of AZD8931, a novel equipotent and reversible inhibitor of signaling by EGFR (HER1), HER2 and HER3 receptors, focusing on cell cycle progression, apoptosis and clonogenic capacity in the human LoVo colorectal cancer (CRC) cell line, also in comparison with the EGFR-blocking monoclonal antibody Cetuximab or the EGFR tyrosine kinase selective small molecular inhibitor Gefitinib. MATERIALS AND METHODS: Cells were pretreated with EGFR inhibitors for 5 consecutive days and then exposed or not to ionizing radiation (IR) (2 Gy daily for 3 consecutive days). Cell proliferation, cell cycle progression and apoptosis were evaluated by flow cytometry and enzyme-linked immunosorbent assay (ELISA), clonogenic potential and radiosensitivity were studied by colony formation assay. RESULTS: AZD8931 induced cell cycle arrest and apoptosis more effectively than Gefitinib and Cetuximab and, more importantly, it was significantly more potent than Gefitinib and Cetuximab in radiosensitizing cells. This radiosensitizing action by AZD8931 mainly occurred by markedly reducing cell cycle progression into S phase, the most radioresistant phase of cell cycle, secondly by inducing apoptosis and reducing clonogenic survival. CONCLUSIONS: Our results show that AZD8931 increases IR efficacy in LoVo cells, suggesting that it works as a potent radiosensitizer, even more efficient than Gefitinib and Cetuximab, opening new pathways of investigation for further in vitro and in vivo studies aimed at confirming its potential to improve local radiotherapy in CRC.