Abstract 3325: The role of MyD88 in chemoresistance, differentiation and hypoxia in cancer stem cells
Authors: Cooke Aoife A. , Gasch Claudia E. , Gallagher Michael F. , O'Leary John J. 
Published: August 2012

Ovarian cancer is the leading cause of gynaecological cancer death worldwide. This high mortality is caused in large part by development of chemoresistant recurrent disease. In primary tumours differentiation status of the tumour is considered a key prognostic factor however in recurrent disease this is no longer the case, suggesting that in recurrent tumours the differentiation status of the tumour has no bearing on the response to chemotherapy. The origins of recurrent disease may be explained by the cancer stem cell (CSC) theory. CSCs are a minority population of cancer cells with stem like properties including enhanced proliferation. The adaptor molecule myeloid differentiation-primary response gene (88) (MyD88), is a key constituent of the toll like receptor 4 (TLR4) pathway. In normal circumstances TLR pathways mediate the body's response to pathogens; however MyD88 has been recently suggested as a possible marker of cancer stemness in ovarian cancer. This work investigates the involvement of MyD88 in the CSC response to chemotherapy, differentiation stimulus and hypoxia treatment. Cell line experiments were carried out in two CSC lines: NTera2 and 2102Ep. NTera2 cells readily differentiate in response to retinoic acid (RA) treatment while 2102Ep cells are nullipotent and resist differentiation via RA. NTera2 cells are more chemosensitive than 2102Ep cells. Cells were incubated in the presence of both retinoic acid and a platinum based chemotherapy drug, both in isolation and in various combinations. RNA was isolated from treated cells, cDNA was synthesised and interrogated for TLR4/MyD88 expression via Q-PCR. To assess whether MyD88 was necessary and/or sufficient for the normal cell response, MyD88 was knocked down in cells via siRNA transfection, and overexpressed via insertion of an overexpression plasmid. The effect of these alterations on the cell lines response to chemotherapy, differentiation stimulus and hypoxia was then measured. The downstream effect of ablation of the MyD88 signal was also assessed using an Affymetrix array, and the chemokine and cytokine expression profile of both cell lines in all treatments was assessed using Quantibody arrays from RayBiotech. MyD88 expression was shown to be affected by chemotherapy, differentiation stimulus and hypoxic treatments. Furthermore when cells were pre-treated with differentiation stimulus or chemotherapy, their normal responses were altered. So far, our work has shown that ablation of the MyD88 signal in nullipotent 2102Ep cells removes their ability to resist differentiation via RA. To close this mechanism we have also shown that overexpression of MyD88 in pluripotent NTera2 cells allows them to resist differentiation via RA. Functional analysis of the role of MyD88 in chemotherapy and hypoxia resistance is currently being assessed. This and the mechanisms involved will be detailed, along with the chemokine/cytokine profile of treated cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3325. doi:1538-7445.AM2012-3325