Mutant KRAS Promotes NKG2D + T Cell Infiltration and CD155 Dependent Immune Evasion.

Background/Aim: Roles for mutant (mt) KRAS in the innate immune microenvironment in colorectal cancer (CRC) were explored. Materials and Methods: Human CRC HCT116-derived, mtKRAS-disrupted (HKe3) cells that express exogenous mtKRAS and allogenic cytokine-activated killer (CAK) cells were co-cultured in 3D floating (3DF) culture. The anti-CD155 antibody was used for function blocking and immunohistochemistry. Results: Infiltration of CAK cells, including NKG2D(+) T cells, into the deep layer of HKe3-mtKRAS spheroids, was observed. Surface expression of CD155 was found to be up-regulated by mtKRAS in 3DF culture and CRC tissues. Further, the number of CD3(+) tumor-infiltrating cells in the invasion front that show substantial CD155 expression was significantly larger than the number showing weak expression in CRC tissues with mtKRAS. CD155 blockade decreased the growth of spheroids directly and indirectly through the release of CAK cells. Conclusion: CD155 blockade may be useful for therapies targeting tumors containing mtKRAS.