Ovarian clear-cell carcinoma (OCCC) is an aggressive form of ovarian cancer with high mutation rates. gene expression comparisons support a role for IL-6 inflammatory cytokine signaling in OCCC pathogenesis. We further show that and mutations cooperate to promote tumor growth through sustained IL-6 overproduction. Our findings establish an epistatic relationship between SWI/SNF chromatin remodeling and PI3K pathway mutations 2-Atractylenolide in OCCC and demonstrate that 2-Atractylenolide these pathways converge on pro-tumorigenic cytokine signaling. We propose that ARID1A protects against inflammation-driven tumorigenesis. (β-CATENIN) mutations have historically been associated with Type I tumors at varying frequencies whereas Type II tumors are largely defined by high frequency (p53) mutations and chromosome instability6 7 8 Therefore EOC consists of a heterogeneous group of cancers each with unique clinical challenges and biology. Ovarian clear-cell carcinoma (OCCC) is the most common Type I tumor accounting for 5-25% of all EOC cases with incidence varying between populations9 10 11 Endometriosis is recognized as a significant risk factor for OCCC12 13 14 Among all EOC subtypes OCCC has the worst prognosis if diagnosed at an advanced stage of disease because of poor response rates to platinum-based chemotherapy9 10 15 16 Consequently survival rates for women with advanced stage OCCC are low9 10 15 16 Although OCCC is the second leading cause of death from ovarian cancer the etiology and pathogenesis of this devastating disease are poorly understood. Recent genome sequencing efforts support a strong genetic contribution to OCCC etiology based upon the discovery of high frequency (up to 50%) tumor mutations17 18 is also somatically mutated in another Type I EOC endometrioid carcinoma and several other gynecologic cancers including uterine clear-cell and endometrioid carcinomas cervical carcinoma and uterine carcinosarcoma19 20 Additional tumor sequencing studies have detected recurrent mutations in several non-gynecologic cancers and taken together components of the SWI/SNF complex are mutated in at least 20% of human cancer19 21 22 23 ARID1A is a subunit within the SWI/SNF chromatin remodeling complex that facilitates target substrate recognition however its role in OCCC tumor initiation and progression has yet to be fully elucidated24. Genetically engineered mouse models offer the opportunity 2-Atractylenolide to investigate the contribution of genetic factors to EOC etiology and pathogenesis25. In this regard early research using mouse models of EOC established causative roles for coexistent mutations in PTEN and KRAS or PTEN and WNT/β-CATENIN pathways in endometrioid EOC7 8 Recently Guan and and mutations in cancer causation. We further provide new mechanistic insight into OCCC pathogenesis by establishing a functional link between coexistent mutations and IL-6 signaling. Results Generation of a novel conditional allele To establish a functional role for mutations in ovarian clear-cell tumorigenesis we generated a novel conditional allele ((Fig. 1A B). embryos 2-Atractylenolide die around gastrulation thus they are not amenable to efficient protein extraction27. In light of its early embryonic lethality we monoalleliclly inactivated in embryonic tissues (via allele in the whole animal. Using this approach we observed an expected 50% reduction in total protein from whole embryo lysates (Fig. 1C D). We next sought to inactivate ARID1A in the OSE. To do this we employed the intrabursal Adenovirus CRE-mediated (AdCRE) recombination system7 29 Efficient CRE-mediated genetic recombination was consistently observed in the OSE and outer epithelial layers of tissues confined to the bursal space (Fig. 1F H I). We performed a series of intrabursal AdCRE injections on two independent cohorts of mice (n=42) and followed them for approximately one year. The mice remained tumor-free with no significant changes in survival other than age-related mortality similar to the phenotypes reported by Guan mutations require additional mutational SMAD4 “hits” in the OSE before tumorigenesis can ensue26. Figure 1 A new conditional allele to explore ARID1A tumor suppressor function mutations initiate ovarian cancer To explore this further we focused on the cancer proto-oncogene PIK3CA (Phosphatidylinositol-4 5 3 catalytic subunit alpha or p110α) which also has high OCCC mutation rates30 31 Recently coexistent mutations were reported in gastric cancer32. Additionally it has been observed that OCCC tumors harboring mutations display concomitant loss of.