SUMMARY Activating mutations in KRAS are among the most frequent events in diverse human carcinomas and are particularly prominent in human pancreatic ductal adenocarcinoma (PDAC). An inducible KrasG12D-driven mouse model of PDAC has established a critical role for sustained KrasG12D expression in tumor maintenance, providing a model to determine the potential for, and the underlying mechanisms of, KrasG12D–independent PDAC recurrence. Here we show that some tumors undergo spontaneous relapse and are devoid of KrasG12D expression and downstream canonical MAPK signaling and instead acquire amplification and overexpression of the transcriptional co-activator Yap1. Functional studies established the role of Yap1 and the transcriptional factor Tead2 in driving KrasG12D–independent tumor maintenance. The Yap1/Tead2 complex acts cooperatively with E2F transcription factors to activate a cell cycle and DNA replication program. Our studies, along with corroborating evidence from human PDAC models, portend a novel mechanism of escape from oncogenic Kras addiction in PDAC.

The signaling mechanisms between prostate cancer cells and infiltrating immune cells may illuminate novel therapeutic approaches. Here, utilizing a prostate adenocarcinoma model driven by loss of Pten and Smad4, we identify polymorphonuclear myeloid-derived suppressor cells (MDSCs) as the major infiltrating immune cell type and depletion of MDSCs blocks progression. Employing a novel dual reporter prostate cancer model, epithelial and stromal transcriptomic profiling identified Cxcl5 as a cancer-secreted chemokine to attract Cxcr2-expressing MDSCs and, correspondingly, pharmacological inhibition of Cxcr2 impeded tumor progression. Integrated analyses identified hyperactivated Hippo-YAP signaling in driving Cxcl5 upregulation in cancer cells through YAP-TEAD complex and promoting MDSCs recruitment. Clinico-pathological studies reveal upregulation and activation of YAP1 in a subset of human prostate tumors, and the YAP1 signature is enriched in primary prostate tumor samples with stronger expression of MDSC relevant genes. Together, YAP-driven MDSC recruitment via heterotypic Cxcl5-Cxcr2 signaling reveals effective therapeutic strategy for advanced prostate cancer. Significance We demonstrate a critical role of MDSCs in prostate tumor progression and discover a cancer cell non-autonomous function of Hippo-YAP pathway in regulation of Cxcl5, a ligand for Cxcr2 expressing MDSCs. Pharmacologic elimination of MDSCs or blocking the heterotypic CxCl5-Cxcr2 signaling circuit elicits robust anti-tumor responses and prolongs survival.

With 5-year survival rates remaining constant at 6% and rising incidences associated with an epidemic in obesity and metabolic syndrome, pancreatic ductal adenocarcinoma (PDAC) is on track to become the second most common cause of cancer-related deaths by 2030. The high mortality rate of PDAC stems primarily from the lack of early diagnosis and ineffective treatment for advanced tumors. During the past decade, the comprehensive atlas of genomic alterations, the prominence of specific pathways, the preclinical validation of such emerging targets, sophisticated preclinical model systems, and the molecular classification of PDAC into specific disease subtypes have all converged to illuminate drug discovery programs with clearer clinical path hypotheses. A deeper understanding of cancer cell biology, particularly altered cancer cell metabolism and impaired DNA repair processes, is providing novel therapeutic strategies that show strong preclinical activity. Elucidation of tumor biology principles, most notably a deeper understanding of the complexity of immune regulation in the tumor microenvironment, has provided an exciting framework to reawaken the immune system to attack PDAC cancer cells. While the long road of translation lies ahead, the path to meaningful clinical progress has never been clearer to improve PDAC patient survival. Pancreatic ductal adenocarcinoma (PDAC) pathogenesisOn gross inspection, PDAC presents as a poorly demarcated, firm white-yellow mass, with the surrounding nonmalignant pancreas typically showing atrophy, fibrosis, and dilated ducts due to the obstructive effects of expanding carcinoma. Microscopically, these neoplasms vary from well-differentiated gland-forming carcinomas to poorly differentiated "sarcomatoid" carcinomas diagnosed only upon immunolabeling due to predominant mesenchymal features (Hruban et al. 2007). PDAC evolves from well-defined precursor lesions that, in the context of their genetic features, define the genetic progression model of pancreatic carcinogenesis (Yachida et al. 2010). Early disease histology manifests as several distinct types of precursor lesions-the most common are microscopic pancreatic intraepithelial neoplasia (PanIN), followed by the macroscopic cysts; namely, the intraductal papillary mucinous neoplasm (IPMN) and mucinous cystic neoplasm (MCN) (Matthaei et al. 2011). Since most PDAC cases become clinically apparent at advanced stages, major opportunities to reduce mortality rest with diagnostics and treatments that would enable the reliable identification and elimination of high-risk precursor lesions. Thus, the identification of these precursor lesions has provided an essential framework to define the genomic features that drive progression to advanced disease and develop effective screening and targeted therapeutics for earlier stage disease (Eser et al. 2011).The noninvasive PanIN lesions were formerly classified into three grades according to the extent of cytological and architectural atypia: PanIN1A (flat lesion) and PanIN1B (micropapillary...

Our study highlights the overactivated neddylation pathway in lung cancer development and as a promising therapeutic target.

Current treatment regimens for pancreatic ductal adenocarcinoma (PDAC) yield poor 5-year survival, emphasizing the critical need to identify druggable targets essential for PDAC maintenance. We developed an unbiased and in vivo target discovery approach to identify molecular vulnerabilities in low-passage and patient-derived PDAC xenografts or genetically engineered mouse model-derived allografts. Focusing on epigenetic regulators, we identified WDR5, a core member of the COMPASS histone H3 Lys4 (H3K4) MLL (1-4) methyltransferase complex, as a top tumor maintenance hit required across multiple human and mouse tumors. Mechanistically, WDR5 functions to sustain proper execution of DNA replication in PDAC cells, as previously suggested by replication stress studies involving MLL1, and c-Myc, also found to interact with WDR5. We indeed demonstrate that interaction with c-Myc is critical for this function. By showing that ATR inhibition mimicked the effects of WDR5 suppression, these data provide rationale to test ATR and WDR5 inhibitors for activity in this disease.