Activation of NF-κB Is a Novel Target of KRAS-Induced Endometrial Carcinogenesis

Purpose: Although the KRAS mutation is one of critical genetic alterations in endometrial carcinogenesis, the downstream targets are not known. Experimental Design: In this study, we investigated the molecular targets of KRAS signals, using tumorigenic cells with oncogenic KRAS mutation established from telomerase reverse transcriptase ( TERT )-immortalized endometrial epithelial cells. Results: We first confirmed that the RAF-ERK pathway, but not the PI3K-Akt pathway, was activated in KRAS tumorigenic cells. However, the introduction of constitutively active MAP/ERK kinase into immortalized cells to mimic RAF-ERK activation failed to obtain tumorigenic phenotypes, indicating the existence of other carcinogenic pathways triggered by KRAS . Recent evidence suggestive of linkage with KRAS signals prompted us to examine the involvement of NF-κB in endometrial carcinogenesis. We found that the DNA-binding activity of NF-κB was markedly elevated in KRAS tumorigenic cells compared with TERT -immortalized cells. Furthermore, the ability of NF-κB to activate the target gene promoters significantly increased in KRAS tumorigenic cells. Introduction of a mutant IκB that is resistant to degradation and thereby enhances the inhibitory effect on NF-κB largely abrogated the transformed phenotypes of KRAS tumorigenic cells. Thus, oncogenic KRAS signals contributed to the tumorigenic phenotypes of endometrial cells by activating the transcription function of NF-κB. Conclusions: These findings clearly show that NF-κB activation is a novel target of oncogenic KRAS in endometrial carcinogenesis, implying the potential utility of NF-κB inhibitors for endometrial cancer chemoprevention, especially with KRAS mutation. Clin Cancer Res; 17(6); 1341–50. ©2011 AACR .