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NODAL/TGF? signalling mediates the self-sustained stemness induced by PIK3CA ^H1047R homozygosity in pluripotent stem cells.

ABSTRACT: Activating PIK3CA mutations are known "drivers" of human cancer and developmental overgrowth syndromes. We recently demonstrated that the "hotspot" PIK3CA ^H1047R variant exerts unexpected allele dose-dependent effects on stemness in human pluripotent stem cells (hPSCs). In the present study, we combine high-depth transcriptomics, total proteomics and reverse-phase protein arrays to reveal potentially disease-related alterations in heterozygous cells, and to assess the contribution of activated TGF? signalling to the stemness phenotype of homozygous PIK3CA ^H1047R cells. We demonstrate signalling rewiring as a function of oncogenic PI3K signalling strength, and provide experimental evidence that self-sustained stemness is causally related to enhanced autocrine NODAL/TGF? signalling. A significant transcriptomic signature of TGF? pathway activation in heterozygous PIK3CA ^H1047R was observed but was modest and was not associated with the stemness phenotype seen in homozygous mutants. Notably, the stemness gene expression in homozygous PIK3CA ^H1047R iPSCs was reversed by pharmacological inhibition of NODAL/TGF? signalling, but not by pharmacological PI3K? pathway inhibition. Altogether, this provides the first in-depth analysis of PI3K signalling in human pluripotent stem cells and directly links strong PI3K activation to developmental NODAL/TGF? signalling. This work illustrates the importance of allele dosage and expression when artificial systems are used to model human genetic disease caused by activating PIK3CA mutations.

SUBMITTER: Madsen RR

PROVIDER: S-EPMC7969366 | biostudies-literature |

REPOSITORIES: biostudies-literature

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