YY1 as a mediator to enhance the resistance of KRAS mutant colorectal cancer cells to cetuximab.

Abstract

Cetuximab has been indicated as the mainstay of metastatic colorectal cancer (CRC) therapy, of which application was impeded by chemoresistance that was casually attributed to KRAS mutation. This study sought to determine whether YY1 mediated the resistance of CRC cells harbouring KRAS mutation (KRASmut) to cetuximab. The expression of YY1 between cetuximab response and resistance was investigated in cancerous tissues from CRC patients received cetuximab therapy comprising eight KRAS wild-type (KRASwt) and 12 KRASmut. The relationship between YY1 expression and cetuximab resistance was explored based on KRASmut and KRASwt CRC cell lines. To explore the role of YY1 in the cetuximab resistance of KRASmut CRC cells, the response to cetuximab was investigated in cetuximab-resistant cells (SW620-R) with YY1 silence and cetuximab sensitive cells (HCT116) with YY1 overexpression. EGFR/Akt/ERK signalling activation, as well as mRNA and active GTP-bound KRAS level were assessed after the treatment. In KRASmut CRC tissues, YY1 expression was correlated with the histological grade and the cetuximab resistance. Significantly markable differences in YY1 expression between cetuximab-resistant and the parental cell lines were found in KRASmut cells. Silencing YY1 resensitized SW620-R cells to cetuximab and led to an elevation of the active GTP-binding KRAS. Conversely, the capability against cetuximab and GTP-binding KRAS activation of HCT116 cells was enhanced by overexpressing YY1. The blockage of EGFR/Akt/ERK signalling by cetuximab was re-observed in SW620-R cells after silencing YY1 but impaired in HCT116 by overexpressing YY1. The YY1 mediates the resistance of KRASmut CRC cells to cetuximab.