YAP and TAZ, transcriptional co-activators and the downstream effectors of the Hippo pathway, are often hyperactivated in diverse cancers where they promote tumor growth. Inhibiting the activity of YAP/TAZ is thus an attractive strategy for the treatment of cancer. However, our findings challenge the idea that YAP/TAZ are simply tumor-promoting. Studying mouse models of liver cancer, we found that YAP/TAZ activity in peritumoral hepatocytes exerts a tumor-suppressive function. While deleting Yap/Taz in tumor cells led to tumor regression, deleting Yap/Taz in peritumoral hepatocytes unexpectedly accelerated tumor growth. Even more strikingly, tumor cells no longer required YAP/TAZ when surrounded by Yap/Taz mutant hepatocytes. These results cannot be explained by a simple mechanism whereby YAP/TAZ directly (cell autonomously) promote the proliferation and survival of tumor cells. Rather, they imply that YAP/TAZ act through a non-cell autonomous mechanism of cell competition, whereby cells with higher YAP/TAZ activity outcompete cells with lower levels. Consequently, experimental hyperactivation of YAP in peritumoral hepatocytes triggered tumor regression. We thus propose that YAP/TAZ activity dictates cellular “fitness”: YAP/TAZ are tumor promoting when higher in tumor cells, but tumor suppressing when higher in tumor-surrounding cells. These findings shift our understanding of YAP/TAZ in cancer: rather than being purely oncogenic, their activity in normal cells can lead to the suppression of tumor growth. These effects raise critical questions for YAP/TAZ-targeted therapies, suggesting that inhibiting YAP/TAZ indiscriminately may, in some contexts, accelerate tumor progression rather than suppress it. Georg Halder. The paradox of YAP/TAZ in cancer biology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr SY28-01.

BACKGROUND & AIMS:Metabolic dysfunction-associated steatotic liver disease (MASLD) and its advanced form, metabolic dysfunction-associated steatohepatitis (MASH), are leading risk factors for liver cancer. While inflammation and fibrosis are known to promote tumorigenesis in MASH, the role of early MASLD in cancer initiation is unclear. Here, we investigated how steatosis alone, without significant fibrosis and inflammation, influences liver cancer development in mouse models. METHODS:We fed mice a Western diet to induce early-stage MASLD, characterized by steatosis and mild hepatitis without fibrosis, and triggered liver tumorigenesis by hydrodynamic tail vein injection of plasmids encoding oncogenes. We combined this with genetic manipulation of Hippo signaling and assessed tumor development using histology and single-nucleus RNA sequencing. RESULTS:Western diet suppressed liver tumor development by promoting the elimination of tumor-initiating cells. This effect was not due to a direct impact on oncogene-expressing cells, but rather to increased competitiveness of the surrounding hepatocytes. Mechanistically, the Western diet activated the Hippo pathway effectors Yap and Taz in steatotic hepatocytes, enabling them to outcompete tumor-initiating cells. Progression to advanced MASH abrogated this tumor-suppressing effect, allowing tumor development. CONCLUSIONS:Steatotic hepatocytes in early MASLD activate a Yap/Taz-dependent cell competition program that can suppress tumor initiation. This tumor-suppressive effect is lost in advanced MASH, where inflammation, fibrosis and other defects undermine the competitiveness of non-mutant hepatocytes. The tumor-suppressive effect of early MASLD adds a new layer to our understanding of how fitness landscapes and cell interactions shape cancer risk during chronic liver disease. IMPACT AND IMPLICATIONS:We found that early stages of steatotic liver disease (MASLD) can suppress tumor initiation in mouse models of liver cancer by triggering Yap/Taz-mediated cell competition. This reveals an unexpected tumor-suppressive role for early MASLD and highlights the importance of non-cell autonomous mechanisms during tumor initiation. Since Hippo-YAP/TAZ signaling is deregulated in many cancers, similar mechanisms may operate in other tissues.

Figure S1 shows A) Fraction of transfected cells after re-expression of NF2 in HEK293 and NF2-mutant mesothelioma cell lines. The proliferation of NF2-mutant mesothelioma cell lines, but not the NF2 wild-type HEK293 cells, is suppressed by NF2 overexpression. B) Effect of SWTX-143 on the proliferation of the Hippo-wild type mesothelioma cell line H2062.

Figure S3 shows Heatmap of differential pathway analysis comparing the tumors of vehicle and SWTX-143-treated mice.

Tracking cell death in vivo can enable a better understanding of the biological mechanisms underlying tissue homeostasis and disease. Unfortunately, existing cell death labeling methods lack compatibility with in vivo applications or suffer from low sensitivity, poor tissue penetration, and limited temporal resolution. Here, we fluorescently labeled dead cells in vivo with Trypan Blue (TBlue) to detect single scattered dead cells or to generate whole-mount three-dimensional maps of large areas of necrotic tissue during organ regeneration. TBlue effectively marked different types of cell death, including necrosis induced by CCl4 intoxication in the liver, necrosis caused by ischemia-reperfusion in the skin, and apoptosis triggered by BAX overexpression in hepatocytes. Moreover, due to its short circulating lifespan in blood, TBlue labeling allowed in vivo “pulse and chase” tracking of two temporally spaced populations of dying hepatocytes in regenerating mouse livers. Additionally, upon treatment with cisplatin, TBlue labeled dead cancer cells in livers with cholangiocarcinoma and dead thymocytes due to chemotherapy-induced toxicity, showcasing its utility in assessing anticancer therapies in preclinical models. Thus, TBlue is a sensitive and selective cell death marker for in vivo applications, facilitating the understanding of the fundamental role of cell death in normal biological processes and its implications in disease.

In the mammalian liver, hepatocytes exhibit diverse metabolic and functional profiles based on their location within the liver lobule. However, it is unclear whether this spatial variation, called zonation, is governed by a well-defined gene regulatory code. Here, using a combination of single-cell multiomics, spatial omics, massively parallel reporter assays and deep learning, we mapped enhancer-gene regulatory networks across mouse liver cell types. We found that zonation affects gene expression and chromatin accessibility in hepatocytes, among other cell types. These states are driven by the repressors TCF7L1 and TBX3, alongside other core hepatocyte transcription factors, such as HNF4A, CEBPA, FOXA1 and ONECUT1. To examine the architecture of the enhancers driving these cell states, we trained a hierarchical deep learning model called DeepLiver. Our study provides a multimodal understanding of the regulatory code underlying hepatocyte identity and their zonation state that can be used to engineer enhancers with specific activity levels and zonation patterns.

Figure S4 shows A) Immunofluorescence stainings of lung sections from mice with mesothelioma after 2 weeks after Adeno-Cre injection, stained for Vimentin (green) and Mesothelin (red). B) Picture of an H&E staining of a lung section from a mouse with mesothelioma that was treated with SWTX-143 for one week.

Hyperactivation of YAP/TAZ, the Hippo pathway downstream effectors, is common in human cancer. The requirement of YAP/TAZ for cancer cell survival in preclinical models, prompted the development of pharmacological inhibitors that suppress their transcriptional activity. However, systemic YAP/TAZ inhibition may sometimes have unpredictable patient outcomes, with limited or even adverse effects because YAP/TAZ action is not simply tumor promoting but also tumor suppressive in some cell types. Here, we review the role of the Hippo pathway in distinct tumor cell populations, discuss the impact of inhibiting Hippo output on tumor growth, and examine current developments in YAP/TAZ inhibitors.

Figure S2 shows A) Heatmap showing YAP signature genes in vehicle and SWTX-143-treated kidney cancer cell line. B) Gene Set Enrichment Analysis of the YAP signature.

Abstract The Hippo pathway and its downstream effectors, the YAP and TAZ transcriptional coactivators, are deregulated in multiple different types of human cancer and are required for cancer cell phenotypes in vitro and in vivo, while largely dispensable for tissue homeostasis in adult mice. YAP/TAZ and their main partner transcription factors, the TEAD1–4 factors, are therefore promising anticancer targets. Because of frequent YAP/TAZ hyperactivation caused by mutations in the Hippo pathway components NF2 and LATS2, mesothelioma is one of the prime cancer types predicted to be responsive to YAP/TAZ-TEAD inhibitor treatment. Mesothelioma is a devastating disease for which currently no effective treatment options exist. Here, we describe a novel covalent YAP/TAZ-TEAD inhibitor, SWTX-143, that binds to the palmitoylation pocket of all four TEAD isoforms. SWTX-143 caused irreversible and specific inhibition of the transcriptional activity of YAP/TAZ-TEAD in Hippo-mutant tumor cell lines. More importantly, YAP/TAZ-TEAD inhibitor treatment caused strong mesothelioma regression in subcutaneous xenograft models with human cells and in an orthotopic mesothelioma mouse model. Finally, SWTX-143 also selectively impaired the growth of NF2-mutant kidney cancer cell lines, suggesting that the sensitivity of mesothelioma models to these YAP/TAZ-TEAD inhibitors can be extended to other tumor types with aberrations in Hippo signaling. In brief, we describe a novel and specific YAP/TAZ-TEAD inhibitor that has potential to treat multiple Hippo-mutant solid tumor types.

Abstract Many cancers harbor mutations in the Hippo pathway that lead to constitutive activation of the transcriptional co-activators YAP/TAZ that then bind the transcription factor TEAD and drive aberrant transcription of target genes involved in cell proliferation and tumor progression. Hyperactivation of YAP/TAZ has also been associated with resistance to targeted therapies, including MAPK pathway inhibitors. To target cancers that bear mutations in the Hippo pathway or are resistant to therapies due to YAP/TAZ activation, we developed SW-682, a pan-TEAD small molecule inhibitor that blocks TEAD-dependent transcription by binding to the palmitoylation pocket of all TEAD isoforms. In vitro, SW-682 inhibited the proliferation of human Hippo-mutant mesothelioma cells with nanomolar potency, with little to no effect on Hippo wild-type tumor cells. SW-682 down-regulated TEAD-dependent reporter gene expression in a dose-dependent manner, while having no effect on reporters monitoring other pathways. In vivo, daily oral administration of SW-682 to adult mice resulted in tumor regression in Hippo-mutant mesothelioma models and caused down-regulation of expression of the TEAD-dependent genes CCN1 and CCN2 and a YAP gene signature, as measured by qPCR or RNA-seq analysis. SW-682 has a favorable PK profile with good oral bioavailability in the mouse and was well tolerated with no signs of body weight loss. To test the hypothesis that TEAD inhibition can overcome YAP-driven resistance mechanisms, we explored SW-682 in combination with MEK inhibitors in several in vitro and ex vivo patient-derived tumor models including BRAF and NRAS mutated melanoma. Moreover, to identify new indications that may benefit from TEAD inhibition, we screened patient-derived 3D organoid tumor cells and matching patient-derived xenograft models that have been molecularly profiled. In summary, SW-682 is a potent and selective investigational TEAD inhibitor which demonstrated anti-tumor effects in models harboring aberrant expression of the Hippo pathway, suggesting therapeutic potential in multiple Hippo-mutant solid tumors. Citation Format: Lei Chen, Paula Milani de Marval, Kendall Powell, Mark Johnson, Greg Falls, Brian Lawhorn, Aurélie Candi, Amuri Kilonda, Bart Vanderhoydonck, Arnaud Marchand, Matthias Versele, Georg Halder, Stephen L. Gwaltney, Adeela Kamal. SW-682: A novel TEAD inhibitor for the treatment of cancers bearing mutations in the Hippo signaling pathway. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4964.

Wound response programs are often activated during neoplastic growth in tumors. In both wound repair and tumor growth, cells respond to acute stress and balance the activation of multiple programs, including apoptosis, proliferation, and cell migration. Central to those responses are the activation of the JNK/MAPK and JAK/STAT signaling pathways. Yet, to what extent these signaling cascades interact at the cis-regulatory level and how they orchestrate different regulatory and phenotypic responses is still unclear. Here, we aim to characterize the regulatory states that emerge and cooperate in the wound response, using the Drosophila melanogaster wing disc as a model system, and compare these with cancer cell states induced by rasV12scrib-/- in the eye disc. We used single-cell multiome profiling to derive enhancer gene regulatory networks (eGRNs) by integrating chromatin accessibility and gene expression signals. We identify a 'proliferative' eGRN, active in the majority of wounded cells and controlled by AP-1 and STAT. In a smaller, but distinct population of wound cells, a 'senescent' eGRN is activated and driven by C/EBP-like transcription factors (Irbp18, Xrp1, Slow border, and Vrille) and Scalloped. These two eGRN signatures are found to be active in tumor cells at both gene expression and chromatin accessibility levels. Our single-cell multiome and eGRNs resource offers an in-depth characterization of the senescence markers, together with a new perspective on the shared gene regulatory programs acting during wound response and oncogenesis.

Many cancers harbor mutations in the Hippo pathway that lead to constitutive activation of the transcriptional co-activators YAP/TAZ that then bind the transcription factor TEAD and drive aberrant transcription of target genes involved in cell proliferation and tumor progression. Hyperactivation of YAP/TAZ has also been associated with resistance to targeted therapies, including MAPK pathway inhibitors. To target cancers that bear mutations in the Hippo pathway or are resistant to therapies due to YAP/TAZ activation, we developed SW-682, a pan-TEAD small molecule inhibitor that blocks TEAD-dependent transcription by binding to the palmitoylation pocket of all TEAD isoforms. In vitro, SW-682 inhibited the proliferation of human Hippo-mutant mesothelioma cells with nanomolar potency, with little to no effect on Hippo wild-type tumor cells. SW-682 down-regulated TEAD-dependent reporter gene expression in a dose-dependent manner, while having no effect on reporters monitoring other pathways. In vivo, daily oral administration of SW-682 to adult mice resulted in tumor regression in Hippo-mutant mesothelioma models and caused down-regulation of expression of the TEAD-dependent genes CCN1 and CCN2 and a YAP gene signature, as measured by qPCR or RNA-seq analysis. SW-682 has a favorable PK profile with good oral bioavailability in the mouse and was well tolerated with no signs of body weight loss. To test the hypothesis that TEAD inhibition can overcome YAP-driven resistance mechanisms, we explored SW-682 in combination with MEK inhibitors in several in vitro and ex vivo patient-derived tumor models including BRAF and NRAS mutated melanoma. Moreover, to identify new indications that may benefit from TEAD inhibition, we screened patient-derived 3D organoid tumor cells and matching patient-derived xenograft models that have been molecularly profiled. In summary, SW-682 is a potent and selective investigational TEAD inhibitor which demonstrated anti-tumor effects in models harboring aberrant expression of the Hippo pathway, suggesting therapeutic potential in multiple Hippo-mutant solid tumors. Citation Format: Lei Chen, Paula Milani de Marval, Kendall Powell, Mark Johnson, Greg Falls, Brian Lawhorn, Aurélie Candi, Amuri Kilonda, Bart Vanderhoydonck, Arnaud Marchand, Matthias Versele, Georg Halder, Stephen L. Gwaltney, Adeela Kamal. SW-682: A novel TEAD inhibitor for the treatment of cancers bearing mutations in the Hippo signaling pathway. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4964.

Cell type identity is encoded by gene regulatory networks (GRN), in which transcription factors (TFs) bind to enhancers to regulate target gene expression. In the mammalian liver, lineage TFs have been characterized for the main cell types, including hepatocytes. Hepatocytes cover a relatively broad cellular state space, as they differ significantly in their metabolic state, and function, depending on their position with respect to the central or portal vein in a liver lobule. It is unclear whether this spatially defined cellular state space, called zonation, is also governed by a well-defined gene regulatory code. To address this challenge, we have mapped enhancer-GRNs across liver cell types at high resolution, using a combination of single cell multiomics, spatial omics, GRN inference, and deep learning. We found that cell state changes in transcription and chromatin accessibility in hepatocytes, liver sinusoidal endothelial cells and hepatic stellate cells depend on zonation. Enhancer-GRN mapping suggests that zonation states in hepatocytes are driven by the repressors Tcf7l1 and Tbx3, that modulate the core hepatocyte GRN, controlled by Hnf4a, Cebpa, Hnf1a, Onecut1 and Foxa1, among others. To investigate how these TFs cooperate with cell type TFs, we performed anin vivomassively parallel reporter assay on 12,000 hepatocyte enhancers and used these data to train a hierarchical deep learning model (called DeepLiver) that exploits both enhancer accessibility and activity. DeepLiver confirms Cebpa, Onecut, Foxa1, Hnf1a and Hnf4a as drivers of enhancer specificity in hepatocytes; Tcf7l1/2 and Tbx3 as regulators of the zonation state; and Hnf4a, Hnf1a, AP-1 and Ets as activators. Finally, taking advantage ofin silicomutagenesis predictions from DeepLiver and enhancer assays, we confirmed that the destruction of Tcf7l1/2 or Tbx3 motifs in zonated enhancers abrogates their zonation bias. Our study provides a multi-modal understanding of the regulatory code underlying hepatocyte identity and their zonation state, that can be exploited to engineer enhancers with specific activity levels and zonation patterns.

The Hippo signaling pathway is widely considered a master regulator of organ growth because of the prominent overgrowth phenotypes caused by experimental manipulation of its activity. Contrary to this model, we show here that removing Hippo transcriptional output did not impair the ability of the mouse liver and Drosophila eyes to grow to their normal size. Moreover, the transcriptional activity of the Hippo pathway effectors Yap/Taz/Yki did not correlate with cell proliferation, and hyperactivation of these effectors induced gene expression programs that did not recapitulate normal development. Concordantly, a functional screen in Drosophila identified several Hippo pathway target genes that were required for ectopic overgrowth but not normal growth. Thus, Hippo signaling does not instruct normal growth, and the Hippo-induced overgrowth phenotypes are caused by the activation of abnormal genetic programs.

Background: The Hippo pathway is an evolutionarily conserved signaling cascade whose deregulation can promote excessive cell proliferation and tumor development. Pathway output is mediated by the YAP and TAZ transcriptional co-activators, which bind to TEAD family transcription factors to drive target gene expression. Genomic aberrations in Hippo pathway components result in constitutive activation of YAP/TAZ, as seen with NF2 mutations in subsets of mesothelioma and other cancers. Hyperactivation of YAP/TAZ has also been associated with resistance to a variety of targeted agents, including EGFR and CDK4/6 inhibitors, suggesting that targeting the pathway may have utility as part of rationally selected combinations, in addition to genomically-informed monotherapy applications. Activity of the YAP/TAZ-TEAD complex thus represents a compelling pharmacologic target, due to its essential role in the pathway, and the presence of a conserved druggable site in TEAD that is required for transcriptional function. Results and Discussion: Using biophysical techniques, we identified novel small molecules that bind to the TEAD auto-palmitoylation pocket. Initial hits were optimized for antagonism of TEAD-based transcription and drug-like properties, ultimately producing highly potent and orally bioavailable TEAD inhibitors. These compounds selectively inhibited the proliferation of cancer cell lines harboring genomic alterations in the Hippo pathway with low nM potency. In vivo models of Hippo pathway-altered xenografts showed consistent monotherapy activity, with dose-dependent and durable tumor regressions achieved at well-tolerated doses. Further characterization of these compounds as monotherapies and as part of rationally-designed combination regimens is ongoing. Citation Format: Adeela Kamal, Aurélie Candi, Matthias Versele, Bart Vanderhoydonck, Arnaud Marchand, Ron de Jong, Thuy Hoang, Georg Halder, Patrick Chaltin, Stephen L. Gwaltney, Mike Burgess. Novel antagonists of TEAD palmitoylation inhibit the growth of Hippo-altered cancers in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3945.

Activated hepatic stellate cells (aHSC) are the main source of extra cellular matrix in liver fibrosis. Activation is classically divided in two phases: initiation and perpetuation. Currently, HSC-based therapeutic candidates largely focus on targeting the aHSCs in the perpetuation phase. However, the importance of HSC initiation during chronic liver disease (CLD) remains unclear. Here, we identified transcriptional programs of initiating and activated HSCs by RNA sequencing, using in vitro and in vivo mouse models of fibrosis. Importantly, we show that both programs are active in HSCs during murine and human CLD. In human cirrhotic livers, scar associated mesenchymal cells employ both transcriptional programs at the single cell level. Our results indicate that the transcriptional programs that drive the initiation of HSCs are still active in humans suffering from CLD. We conclude that molecules involved in the initiation of HSC activation, or in the maintenance of aHSCs can be considered equally important in the search for druggable targets of chronic liver disease.

BACKGROUND AND AIMS:Earlier diagnosis and treatment of intrahepatic cholangiocarcinoma (iCCA) are necessary to improve therapy, yet limited information is available about initiation and evolution of iCCA precursor lesions. Therefore, there is a need to identify mechanisms driving formation of precancerous lesions and their progression toward invasive tumors using experimental models that faithfully recapitulate human tumorigenesis.APPROACH AND RESULTS:To this end, we generated a mouse model which combines cholangiocyte-specific expression of KrasG12D with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-induced inflammation to mimic iCCA development in patients with cholangitis. Histological and transcriptomic analyses of the mouse precursor lesions and iCCA were performed and compared with human analyses. The function of genes overexpressed during tumorigenesis was investigated in human cell lines. We found that mice expressing KrasG12D in cholangiocytes and fed a DDC diet developed cholangitis, ductular proliferations, intraductal papillary neoplasms of bile ducts (IPNBs), and, eventually, iCCAs. The histology of mouse and human IPNBs was similar, and mouse iCCAs displayed histological characteristics of human mucin-producing, large-duct-type iCCA. Signaling pathways activated in human iCCA were also activated in mice. The identification of transition zones between IPNB and iCCA on tissue sections, combined with RNA-sequencing analyses of the lesions supported that iCCAs derive from IPNBs. We further provide evidence that tensin-4 (TNS4), which is stimulated by KRASG12D and SRY-related HMG box transcription factor 17, promotes tumor progression.CONCLUSIONS:We developed a mouse model that faithfully recapitulates human iCCA tumorigenesis and identified a gene cascade which involves TNS4 and promotes tumor progression.