Abstract B018: Dual roles of LATS1/2 in ovarian cancer reveal critical context dependence of hippo pathway signaling

The Hippo signaling pathway, through the core kinases LATS1 and LATS2, plays a critical role in regulating tissue homeostasis, proliferation, and organ size by phosphorylating and inactivating the transcriptional coactivator YAP (Yes-associated protein). While LATS1/2 are often described as tumor suppressors in various solid cancers, their mechanistic contribution to ovarian cancer remains incompletely characterized. The prevailing model posits that low LATS1/2 expression leads to YAP activation and transcription of oncogenic genes, thereby promoting tumor progression. However, our study identifies an unexpected dual role of LATS1/2 in ovarian cancer, revealing context-dependent effects on cell survival and YAP function. This study aims to define the mechanisms underlying that dichotomy. To investigate the functional consequences of LATS1/2 expression in ovarian cancer, we used two high-grade serous ovarian cancer cell lines with low endogenous LATS1/2 expression—TOV3041G and OV1946—to assess the impact of LATS1 or LATS2 overexpression, introduced via lentiviral transduction. Functional assays demonstrated significantly reduced proliferation, migration, and invasion in both cell lines upon LATS1 or LATS2 overexpression, supporting their canonical tumor-suppressive roles. Surprisingly, the knockdown of LATS1/2 via siRNA in OVCAR8 cells resulted in decreased proliferation—opposite to expectations based on known Hippo-YAP pathway functions. To explore this paradox, we performed RNA-sequencing combined with TCGA, which revealed enrichment of apoptotic signatures in LATS1/2 knockdown cells. Subsequent validation confirmed increased apoptotic activity, including elevated caspase-3/7 activity (measured by Caspase-Glo 3/7 assay), increased Annexin V binding, and 7-AAD uptake, consistent with early and late apoptotic events. To investigate whether the altered phenotype was associated with dysregulated YAP signaling, we assessed YAP subcellular localization using immunofluorescence and nuclear-cytoplasmic fractionation. These analyses revealed a marked failure of YAP to translocate into the nucleus in LATS1/2 knockdown cells, despite unchanged total YAP protein levels. In addition, qPCR analysis showed reduced expression of canonical YAP target genes, CTGF and CYR61, indicating suppressed YAP-driven transcription in the knockdown cells. These findings suggest that in certain ovarian cancers, loss of LATS1/2 expression does not activate YAP but instead disrupts its nuclear localization and function, leading to apoptotic cell death. This highlights a previously unrecognized context-specific vulnerability where ovarian cancer cells may rely on minimal LATS1/2 activity to sustain YAP function and survival. Our results challenge the simplistic view of LATS1/2 as uniformly tumor-suppressive and suggest that their role in ovarian cancer may be more nuanced and cell-type dependent. Understanding this dualistic behavior could uncover therapeutic opportunities for selectively targeting YAP signaling in ovarian tumors with divergent LATS1/2 dependencies. Citation Format: Yalun Zhu, Barbara Vanderhyden. Dual roles of LATS1/2 in ovarian cancer reveal critical context dependence of hippo pathway signaling [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr B018.