NF-kB Signaling In Cancer Cells Research Articles

Abstract 5461: B7-H3 regulates NF-kB signaling in cancer cells by modulating the degradation and re-synthesis of IkBα

Abstract B7-H3, a B7 homologue, is highly expressed on tumors and tumor vasculature. Although its role as a T cell inhibitor or co-stimulator is still under investigation, high expression of membranous B7-H3 in the tumor compartment is correlated with poor overall survival. NF-kB activation, standing at the intersection between inflammation and cancer, can lead to both the production of cytokines that engage the innate immune system, as well as pro-proliferative signals in cancer. B7-H3 has been shown to enhance and suppress inflammatory signaling by modulating NF-kB. However, the mechanism by which this occurs in cancer cells remains unknown. In this study, we aim to understand how B7-H3 modulates the NF-kB pathway in order to regulate incoming inflammatory signals in cancer cells. The human colon cancer cell line, HCT116, was stably transfected with a transcriptionally-coupled post-translational NF-kB luciferase reporter comprising of the inhibitor of NF-kB, IkBα, fused to firefly luciferase and placed downstream of an NF-kB responsive promoter, kB5. This construct allows for the real-time readout of the degradation of IkBα and NF-kB driven transcriptional re-synthesis of IkBα in response to a stimulus. The reporter cell line was treated with two stimulants, TNFα and flagellin, that activate NF-kB through different pathways and to different degrees with or without treatment with human B7-H3. Treatment of the reporter cell line with B7-H3 alone did not induce IkBα degradation or re-synthesis. However, stimulation of the reporter cell line with TNFα or flagellin in combination with B7-H3 attenuated the degradation of IkBα and its re-synthesis compared to stimulation with TNFα or flagellin alone. Maximal re-synthesis of IkBα when stimulated with TNFα was 8.25 ± 1.51 fold (S.D.) and significantly increased compared to cells additionally treated with B7-H3 (5.83 ± 1.23 fold, p = .01). In addition, peak degradation time of IkBα when cells were stimulated by TNFα was 45 ± 5 min (S.D.), and significantly shorter than when cells were also treated with B7-H3 (61.67 ± 2.89 min, p = .01). Similar trends were observed when cells were treated with both flagellin and B7-H3 compared to stimulation with flagellin alone. These studies show that B7-H3 suppresses the response of colon cancer cells to incoming inflammatory stimuli and attenuates NF-kB signaling by tempering the kinetics and dynamics of IkBα. Citation Format: Sarah Glazer, Seth Gammon, David Piwnica-Worms. B7-H3 regulates NF-kB signaling in cancer cells by modulating the degradation and re-synthesis of IkBα [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5461.

Abstract TMEM-017: COLLAGEN TYPE XI ALPHA 1 (COL11A1) IS A NOVEL STROMAL MEDIATOR OF CHEMORESISTANCE

Abstract Despite an initial satisfactory response to platinum and taxane-based regimens, approximately 80% of ovarian cancer patients will succumb to chemoresistant recurrent disease. Thus, there is a dire need to understand the mechanism by which tumor cells develop resistance to subsequent therapies after first-line cisplatin treatment. We previously identified that collagen type XI, alpha 1 (COL11A1) is a novel biomarker associated with poor survival, metastasis, and chemoresistance in ovarian cancer. COL11A1 is expressed in a subset of α-SMA-positive cancer-associated fibroblasts (CAFs) adjacent to tumor cells. COL11A1 expression in peritumoral CAFs increases during ovarian cancer progression, with the highest expression in recurrent tumors. However, the functional significance of stromal COL11A1 in ovarian cancer progression and chemoresistance is largely unknown. To determine the role of stromal COL11A1 in chemoresistance, we generated COL11A1-overexpressing TRS3 ovarian fibroblasts, co-cultured them with A2780 and OVCAR3 ovarian cancer cells, and measured cancer cell sensitivity to cisplatin. Our data showed that ovarian cancer cells become resistant to cisplatin when cultured in direct contact with COL11A1-overexpressing fibroblasts as well as in fibroblast conditioned media. Furthermore, full-length COL11A1 protein, extracted from A204 cell line, increased cisplatin resistance in ovarian cancer cells, suggesting that COL11A1 is sufficient to induce chemoresistance. Interestingly, culture of cancer cells on full-length COL11A1 protein resulted in increased number of ALDHhigh cancer stem-like cells and activation of Akt, the principal mediator of pro-survival signaling. To further dissect the mechanism by which COL11A1 leads to cisplatin resistance in tumor cells, we performed RNA-seq analysis of tumor cells after COL11A1 overexpression. Our data showed that COL11A1 did not change the levels of genes involved in cisplatin transport and DNA repair pathway in cancer cells, which are well-established mechanisms to confer cisplatin resistance. Rather, COL11A1 increased the expression of pro-inflammatory genes, some of which are known to confer chemoresistance in ovarian cancer. Consistently, our Western data showed that COL11A1 activates NF-kB signaling in cancer cells, a central pathway regulating pro-inflammatory genes. Collectively, our data suggest that COL11A1 contributes to chemoresistance possibly due to an increased survival of ALDHhigh cancer stem-like cells through activation of pro-inflammatory signaling. Citation Format: Miran Rada, Catherine Eldred, Jessica Sage, Sandra Orsulic and Dong-Joo Cheon. COLLAGEN TYPE XI ALPHA 1 (COL11A1) IS A NOVEL STROMAL MEDIATOR OF CHEMORESISTANCE [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-017.