Pancreatic ductal adenocarcinoma (PDAC) is characterized by a high degree of inflammation and profound immune suppression. Here we identify Yes-associated protein (Yap) as a critical regulator of the immunosuppressive microenvironment in both mouse and human PDAC. Within Kras:p53 mutant pancreatic ductal cells, Yap drives the expression and secretion of multiple cytokines/chemokines, which in turn promote the differentiation and accumulation of Myeloid-derived suppressor cells (MDSCs) both in vitro and in vivo. Pancreas-specific knockout of Yap or antibody-mediated depletion of MDSCs promoted macrophage reprogramming, reactivation of T cells, apoptosis of Kras mutant neoplastic ductal cells, and pancreatic regeneration after acute pancreatitis. In primary human PDAC, YAP expression levels strongly correlate with a MDSC gene signature, and high expression of YAP or MDSC-related genes predicts decreased survival in PDAC patients. These results reveal multifaceted roles YAP in PDAC pathogenesis and underscore its promise as a therapeutic target for this deadly disease.

The acquisition of stemness is a hallmark of aggressive human hepatocellular carcinoma (hHCC). The stem cell marker OCT4 is frequently expressed in HCCs, and its expression correlates with those of putative cancer stem cell (CSC) markers and CSC properties. Here, we describe a novel mechanism of CSC maintenance by SRY through OCT4. We previously reported that Sry is involved in tumor malignancy in rodent HCCs. However, the oncogenic function of SRY in hHCCs is poorly understood. Ectopic expression of SRY increased multiple stem cell factors, including OCT4 and CD13. The OCT4 promoter contained SRY-binding sites that were directly activated by SRY. In HCC-derived cells, SRY knockdown decreased OCT4 expression and cancer stem-like phenotypes such as self-renewal, chemoresistance, and tumorigenicity. Conversely, OCT4 and SRY overexpression promoted cancer stem-like phenotypes. OCT4 knockdown in SRY clones downregulated the self-renewal capacity and chemoresistance. These data suggest that SRY is involved in the maintenance of cancer stem-like characteristics through OCT4. Moreover, CSCs of HCCderived cells differentiated into Tuj1-positive neuron-like cells by retinoic acid. Noteworthily, SRY was highly expressed in some hHCC patients. Taken together, our findings imply a novel therapeutic strategy against CSCs of hHCCs. STEM CELLS 2015;33:2652-2663 SIGNIFICANCE STATEMENTWe demonstrated that SRY, sex-determining factor, is involved in maintenance of cancer stemlike properties such as self-renewal, chemoresistance, and tumorigenicity through upregulation of OCT4. SRY induced the expression of ES markers and cancer stem cell (CSC) markers in HCCderived cell lines. CSC of HCC-derived cell lines differentiated to neuronal cells and hepatocytes, indicating that CSCs of HCC have multipotency. Our data ssuggest that SRY and OCT4 enhance cancer stem-like features, and it can be a potential target of differentiation therapy.

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Highlights d Yap maintains the global metabolic transcriptional program in conjunction with Myc d Yap ablation triggers metabolic crisis and regresses earlystage pancreatic tumors d Yap ablation de-represses Sox2 and acinar lineage genes via DNA demethylation d Sox2 restores Myc and metabolic homeostasis in Yap-null pancreatic tumor cells

Sgf29, a component of the SPT-ADA-GCN5 acetyltransferase (SAGA) complex, binds H3K4me2/3 marks and leads to histone H3 acetylation. Previously, we found that downregulation of Sgf29 suppresses c-Myc-mediated malignant transformation. Nonetheless, the upstream regulator of the Sgf29 gene is not yet known. Here, we report that Sry (sex-determining region Y), an HMG (high-mobility group) domain containing transcription factor, directly upregulates Sgf29 gene expression. Sry expression was deregulated in two out of the four tested male rodent hepatocellular carcinoma (rHCC) cell lines. Luciferase reporter and chromatin immunoprecipitation assays indicated that Sry could bind HMG-boxes in the proximal promoter region of the Sgf29 gene. Knockdown of Sry robustly lowered anchorage-independent growth, invasiveness and tumorigenicity of rHCC cells, whereas ectopic expression of Sry conferred more malignant properties. Thus, these data show that Sry is involved in male-specific malignant conversion of rHCCs via Sgf29 upregulation.

Deregulated c-Myc expression is a hallmark of many human cancers. We have recently identified a role of mammalian homolog of yeast SPT-ADA-GCN5-acetyltransferas (SAGA) complex component, SAGA-associated factor 29 (SGF29), in regulating the c-Myc overexpression. Here, we discuss the molecular nature of SFG29 in SPT3-TAF9-GCN5-acetyltransferase complex, a counterpart of yeast SAGA complex, and the mechanism through which the elevated SGF29 expression contribute to oncogenic potential of c-Myc in hepatocellularcarcinoma (HCC). We propose that the upstream regulation of SGF29 elicited by sex-determining region Y (Sry) is also augmented in HCC. We hypothesize that c-Myc elevation driven by the deregulated Sry and SGF29 pathway is implicated in the male specific acquisition of human HCCs.

The subpopulation of cancer stem cells (CSCs) in tumor tissues drives tumorigenesis and causes the infiltration of cancer cells to surrounding tissues. CSCs are considered to induce tumor initiation, progression, and relapse. Conventional chemotherapies eliminate bulk tumors; however, CSCs evade most therapies. We recently showed that differentiation of CSCs in hepatocellular carcinoma diminished malignant phenotypes. The best strategy for CSC-targeting therapy is yet unknown, however, it appears that differentiation therapy would be effective for certain types of tumors. In this review, we discuss the characteristics of CSCs and prospective use of differentiation therapy for cancer stem cells.

Lineage plasticity has been proposed as a major source of intratumoral heterogeneity and therapeutic resistance. Here, by employing an inducible genetic engineered mouse model, we illustrate that lineage plasticity enables advanced Pancreatic Ductal Adenocarcinoma (PDAC) tumors to develop spontaneous relapse following elimination of the central oncogenic driver - Yap. Transcriptomic and immunohistochemistry analysis of a large panel of PDAC tumors reveals that within high-grade tumors, small niches of PDAC cells gradually evolve to re-activate pluripotent transcription factors (PTFs), which lessen their dependency on Yap. Comprehensive Cut&Tag analysis demonstrate that although acquisition of PTF expression is coupled with the process of epithelial-to-mesenchymal transition (EMT), PTFs form a core transcriptional regulatory circuitry (CRC) with Jun to overcome Yap dependency, which is distinct from the classic TGFb-induced EMT-TF network. A chemical-genetic screen and follow-up functional studies establish Brd4 as an epigenetic gatekeeper for the PTF-Jun CRC, and strong synergy between BET and Yap inhibitors in blocking PDAC growth.