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A Tissue-Specific Tankyrase Inhibitor Drives Key Developmental and Oncogenic Pathways

ABSTRACT: Tissue-specific regulation of WNT and YAP/TAZ signaling is critical for optimal organismal growth, development, and maintenance. Uncontrolled activity often leads to developmental abnormalities and aggressive cancers. Tankyrase (TNKS) is a poly-ADP-ribose polymerase (PARP) that controls both WNT and YAP/TAZ signaling. However, it is unclear how TNKS activity is regulated in a tissue and cell-type specific manner. Here, we identified the previously uncharacterized prostate-associated gene 4 (PAGE4) as a tissue-specific TNKS inhibitor. Structural and biochemical studies revealed that mechanistically PAGE4 inhibits TNKS through hijacking TNKS substrate binding pockets leading to the stabilization of TNKS substrates. In vitro cell culture and in vivo zebrafish and transgenic mouse model studies showed that PAGE4 is a potent inhibitor of TNKS and WNT signaling. Interestingly, PAGE4 is physiologically restricted to expression in select tissues and cell types, including WNT producing prostatic fibroblasts where spatiotemporal regulation of WNT signaling is critical for proper organ development. Surprisingly, PAGE4 is aberrantly expressed in hepatocellular carcinomas that bypass TNKS through mutant CTNNB1 driven WNT signaling. In vitro and in vivo tumorigenic studies revealed that PAGE4 initially function as a tumor suppressor through inhibition of WNT signaling, but upon CTNNB1 mutation becomes an oncogenic driver through YAP/TAZ signaling. Thus, we establish PAGE4 as a robust tissue-specific TNKS inhibitor that physiologically coordinates developmental WNT signaling, but genetic aberration during cancer progression re-wire PAGE4 into pro-oncogenic YAP/TAZ pathway.

ORGANISM(S): Homo sapiens

PROVIDER: GSE141323 | GEO | 2020/12/01

REPOSITORIES: GEO

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Project description:Uncontrolled Transforming growth factor-beta (TGFβ) signaling promotes aggressive metastatic properties in late-stage breast cancers. However, how TGFβ-mediated cues are directed to induce late-stage tumorigenic events is poorly understood, particularly given that TGFβ has clear tumor suppressing activity in other contexts. Here we demonstrate that the transcriptional regulators TAZ and YAP (TAZ/YAP), key effectors of the Hippo pathway, are necessary to promote and maintain TGFβ-induced tumorigenic phenotypes in breast cancer cells. Interactions between TAZ/YAP, TGFβ-activated SMAD2/3, and TEAD transcription factors reveal convergent roles for these factors in the nucleus. Genome-wide expression analyses indicate that TAZ/YAP, TEADs and TGFβ-induced signals coordinate a specific pro-tumorigenic transcriptional program. Importantly, genes cooperatively regulated by TAZ/YAP, TEAD, and TGFβ, such as the novel targets NEGR1 and UCA1, are necessary for maintaining tumorigenic activity in metastatic breast cancer cells. Nuclear TAZ/YAP also cooperate with TGFβ signaling to promote phenotypic and transcriptional changes in non-tumorigenic cells to overcome TGFβ repressive effects. Our work thus identifies crosstalk between nuclear TAZ/YAP and TGFβ signaling in breast cancer cells, revealing novel insight into late-stage disease-driving mechanisms. Expression profiling was conducted following the repression of the transcriptional regulators TAZ and YAP (TAZ/YAP), the TEAD family of transcription factors (TEAD1/2/3/4), or the TGFb signaling pathway (with SB-431542, an inhibitor of the TBRI recpeptor) in human MDA-MB-231-LM2 breast cancer cells treated with TGFβ1. Human MDA-MB-231-LM2-4 breast cancer cells were transfected with control siRNA, or siRNAs targeting TAZ/YAP or all four TEADs and were treated 24 hours later with 500pM TGFβ1 or 5mM SB-431542 for an additional 24 hours. Total RNA was isolated and twelve microarrays in total were performed, with each condition carried out three times on separate days. The Boston University Microarray Core generated the data using the Affymetrix Human Gene 1.0 St Array.

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A Tissue-Specific Tankyrase Inhibitor Drives Key Developmental and Oncogenic Pathways

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