Alterations in MyD88 and microRNA Expression Are Associated with Chemoresistance in Epithelial Ovarian Cancer.
Charles D'Adhemar, Sharon A O'Toole, Britta Stordal, Cara M Martin, Lynda McEvoy, Darragh J Crowley, Orla M Sheils, John J O'Leary. Trinity College Dublin, Ireland
Background: The prognosis of epithelial ovarian cancer (EOC) is poor, in part due to the high frequency of chemoresistance. The Toll-like receptor-4 pathway is thought to mediate some of this resistance, particularly via the adaptor protein MyD88. We previously described different clinicopathologic features associated with TLR-4/MyD88 expression in EOC, including predominance of MyD88 expression in serous carcinomas and significantly reduced survival if MyD88+. We examined the expression of MyD88 in chemosensitive and chemoresistant EOC cells, together with two microRNAs that regulate the TLR-4/MyD88 pathway (miR-21 & miR-146a), to assess the direct association between biological behaviour, MyD88 and its molecular regulators.
Design: Archival paraffin-embedded EOC samples (n=22) were divided into type 1 (MyD88+) or type 2 (MyD88-) based on previous immunohistochemical (IHC) expression. Pure tumour samples were obtained using laser capture microdissection, and RNA extracted for gene (n=22) and miRNA analysis (n=18). RNA was extracted from 8 human cancer cells lines, EOC lines 59M, SK-OV-3, A2780 & IGROV-1, and cervical cancer cells KB-3-1, as well as chemoresistant cancer cells A2780cis (Cisplatin-resistant), IGROV-1CDDP (Cisplatin & Paclitaxel-resistant) and KB-8-5-11 (Paclitaxel-resistant). Expression of TLR-4 & MyD88 genes and miRNAs miR-21 & miR-146a was assessed using TaqMan® Real-Time PCR.
Results: TLR-4 & MyD88 gene expression in archival patient samples showed marked heterogeneity but MyD88 expression correlated with previous IHC categorisation into type 1 and 2 tumours. In cell lines MyD88 was expressed (relative to A2780 which is MyD88-) in 59M, SK-OV-3, IGROV-1 & KB-3-1. However, MyD88 expression was significantly increased in all 3 chemoresistant cell lines (A2780cis, IGROV-1CDDP & KB-8-5-11). MicroRNA analysis in archival samples showed significantly increased expression of miR-21 and miR-146a in MyD88- cancers. Similarly, increased miR-146a was detected in those EOC and cervical cells with increased MyD88 expression, particularly A2780cis & KB-8-5-11, although miR-21 was decreased in A2780cis cells.
Conclusions: Our results demonstrate significant alterations in MyD88 expression between chemosensitive and chemoresistant ovarian cancer cells, and significant changes in microRNA expression between MyD88+ & MyD88- cancers. This provides further evidence that MyD88 expression, in part regulated by miR-21 and miR-146a, is associated with adverse biological characteristics including resistance to standard platinum and taxane-based chemotherapies, with consequent reduced survival.
Category: Gynecologic & Obstetrics
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 117, Tuesday Afternoon