OCT4-mediated transcription confers oncogenic advantage for a subset of gastric tumors with poor clinical outcome.

Deregulated transcription programs and signaling pathways are the critical factors involved in the process of carcinogenesis. Signaling pathway-based classification of tumors is expected to pave the way for the development of targeted therapeutics. We investigated the OCT4-mediated transcription program in the gene expression profiles of 939 gastric tumor samples. A set of 84 genes showing positive correlation with the activation pattern of the available OCT4 gene sets were found to consistently express in diffuse, poorly differentiated, and stage-III gastric tumors with poor prognosis. We also developed stable OCT4-silenced gastric cancer cells and the resultant gene expression changes were investigated by genome-wide mRNA profiling. Functional genomic investigation of the genes downregulated in OCT4-silenced cells and the pathways co-activated with OCT4 gene set across gastric tumors revealed the positive association of dysregulated OCT4 with TGF-β, GLI, PRC2/EzH2, Wnt, KRAS, STK33, and YAP signaling pathways in diffuse subtype gastric tumors. Elevated expression of OCT4 gene set was identified to represent the previously described EMT_UP as well as the GENOMICALLY STABLE subtypes of gastric tumors. Integrative genomic screening of the drug sensitivity of gastric cancer cells in correlation with the expression of OCT4 gene set across drug sensitivity databases revealed the inhibitors of tyrosine kinases, HDAC, and HSP90 to have a negative correlation and needs to be investigated for their potential therapeutic features for the subset of OCT4-activated gastric tumors. Thus, the subset of gastric tumors with OCT4 activation, the associated oncogenic signaling pathways, and potential therapeutic candidates were identified for the development of targeted therapeutic strategies.