KRAS mutations influence the cellular behavior and response of CRC cells to a 5-Fluorouracil (FU) based radiochemotherapy combined with receptor tyrosine kinase inhibitors

Aims: 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 SW 480 with different mutations in KRAS and their response to a combined radiochemotherapy (RCT) in the absence or presence of different receptor tyrosine kinase inhibitors (RTKI).

Methods: The colorectal cancer cell line SW 480 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 RTKI was demonstrated by colony formation assays.

Results: Highest proliferation was observed in SW480-p.G13D cells whereas SW480-p.G12V cells demonstrated the most aggressive behavior in migration and invasion assays. No difference in the phosphorylation status of MAPK component ERK was observed after different stimuli. The lowest sensitivity to RCT was found in SW480 cells carrying the p.G13D mutation. In these cells, treatment with the EGF-receptor inhibitor erlotinib in addition to RCT lead to the most prominent induction of cell death compared to cells with other KRAS mutations. SW 480 cells with wild-type KRAS showed the lowest resistance to RCT combined with IGF-IR receptor inhibitor NVP-AEW 541.

Conclusion: In our experiments a constitutive activation of the MAPK signaling pathway could not be shown despite the different cellular behavior of KRAS mutated SW 480 cells. Further, we observed that different KRAS mutations have different sensitivity to a RCT in combination with RTKI.