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.