Modulation of fibroblasts phenotype by colorectal cancer cells-secreted factors is mostly independent of oncogenic KRAS

KRAS mutations have been shown to extend their oncogenic effects beyond the cancer cell, influencing the tumor microenvironment components. Herein, we studied the impact of mutant KRAS on the modulation of cancer-associated fibroblasts (CAFs) pro-tumorigenic properties. To do so, we challenged CCD-18Co normal-like colon fibroblasts with control media (DMEM alone and DMEM+rhTGF{beta}1 media), and conditioned media from control and KRAS silenced colorectal cancer (CRC) cells. Two mutant KRAS CRC cell lines-HCT116 and LS174T, were used. Major pro-tumorigenic fibroblasts phenotypic features, such as -SMA expression, TGF{beta}1 and HGF production, extracellular matrix components and metalloproteinases expression, collagen contraction and migration capacities, were analyzed upon fibroblast challenging with cells conditioned media. Our results showed that the mutant KRAS CRC cells-secreted factors are capable of turning normal-like fibroblasts into CAF-like by modulating -SMA expression, TGF{beta}1 and HGF production and migration capacity, though in a cell line-specific manner. In this scenario, oncogenic KRAS showed to play a secondary role, regulating only discrete features in each cancer cell-educated fibroblasts. For instance, in HCT116, KRAS impairs fibroblasts migration and in LS174T it promotes -SMA expression. In summary, our work suggests that mutant KRAS does not play a major role in controlling the CRC cell secreted factors that modulate fibroblasts behavior. This KRAS-independent modulation of fibroblast pro-tumorigenic features is likely to negatively impact the response to KRAS inhibitors, thus standing as a putative mechanism of resistance to KRAS-inhibition, with possible therapeutical relevance.