Id1, Spp1andPak3are biomarkers ofSmad4and TGF-β1 dependency in conditional intestinal adenoma, organoids and colorectal cancer

Abstract

AbstractThe evolutionarily conserved TGF-β signalling pathway suppresses cell growth, yet loss of function results in cancer phenotypes. Here, we evaluate loss of the TGF-β pathway signal transduction regulator, Mothers against decapentaplegic homolog 4 (Smad4) with respect to intestinal adenoma phenotypes and specific TGF-β dependent gene expression. ConditionalLgr5-Creactivation (Apcfl/flSmad4fl/flLgr5CreERT2) resulted in loss of function ofApcandSmad4, reduced small intestinal adenoma burden, yet discordant development of large caecal adenoma with nuclear localisation of phospho-Smad2/3.ApcΔ/ΔSmad4Δ/Δadenoma organoids resisted TGF-β1 induced cell death and EMT (IC50534pM) compared toApcΔ/ΔSmad4+/+(IC5024pM). TGF-β1 (390pM) modified adenoma bulk mRNA gene expression (RNA-Seq), with decreasedId1and highSpp1inApcΔ/ΔSmad4Δ/Δ. Single cell RNAseq of caecal adenoma identifiedLgr5low, Pak3highandId1lowprogenitor populations inApcΔ/ΔSmad4Δ/Δ, that also correlated with poor prognosis in colorectal cancer (TCGA).Smad4loss of function-TGF-β1 dependentId1low,Spp1highandPak3highin intestinal epithelial progenitor cells are specific gene-pathway biomarkers for further evaluation in intestinal cancers.