Mutations in KRAS influence the behavior and response of colorectal cancer cells to 5-FU based radiochemotherapy combined with receptor tyrosine kinase inhibitors

Mutations of the proto-oncogene KRAS are supposed to lead to an increased activity of KRAS inducing a constitutive activation of the downstream MAPK signaling pathway. The aim of the work was to investigate the behavior of colorectal cancer cell line SW48 with different mutations in KRAS and their response to a combined radiochemotherapy (RCT) in the presence of different receptor tyrosin kinase inhibitors (RTKI). The colorectal cancer cell line SW48 carrying either KRAS wild-type or the KRAS mutations p. G12V, p. G12D and p. G13D were used. Cell proliferation, migration and invasion assays were performed to further characterize the cells. Activation of MAPK signaling pathway was assessed by Western blots. The sensitivity of the cell lines to a 5-FU based RCT and in the presence of RTKIs Erlotinib und AEW541 was demonstrated by colony formation assays. No difference in proliferation was seen between cells with KRAS wild-type and KRAS mutations. Cells with p. G12V demonstrated the most aggressive behavior in migration and invasion assays. No relevant difference in the phosphorylation status of MAPK component ERK was observed after different stimuli. The most sensitivity to a 5-FU based RCT in the presence of RTKI was found in SW48 cells carrying the p. G13D mutation. SW48 cells carrying the p. G12D showed the most resistance to a 5-FU based RCT in the presence of RTKI. In our experiments a constitutive activation of the MAPK pathway could not be shown despite the different KRAS mutated SW48 cells. SW48 cells with p. G12V demonstrated the most aggressive behavior. Further, we observed that different KRAS mutations have different sensitivity to a 5-FU based RCT in combination with RTKI.