The MyD88+ Phenotype Is an Adverse Prognostic Factor in Epithelial Ovarian Cancer

Abstract

The prognosis of epithelial ovarian cancer is poor in part due to the high frequency of chemoresistance. Recent evidence points to the Toll-like receptor-4 (TLR4), and particularly its adaptor protein MyD88, as one potential mediator of this resistance. This study aims to provide further evidence that MyD88 positive cancer cells are clinically significant, stem-like and reproducibly detectable for the purposes of prognostic stratification. Expression of TLR4 and MyD88 was assessed immunohistochemically in 198 paraffin-embedded ovarian tissues and in an embryonal carcinoma model of cancer stemness. In parallel, expression of TLR4 and MyD88 mRNA and regulatory microRNAs (miR-21 and miR-146a) was assessed, as well as in a series of chemosensitive and resistant cancer cells lines. Functional analysis of the pathway was assessed in chemoresistant SKOV-3 ovarian cancer cells. TLR4 and MyD88 expression can be reproducibly assessed via immunohistochemistry using a semi-quantitative scoring system. TLR4 expression was present in all ovarian epithelium (normal and neoplastic), whereas MyD88 was restricted to neoplastic cells, independent of tumour grade and associated with reduced progression-free and overall survival, in an immunohistological specific subset of serous carcinomas, p<0.05. MiR-21 and miR-146a expression was significantly increased in MyD88 negative cancers (p<0.05), indicating their participation in regulation. Significant alterations in MyD88 mRNA expression were observed between chemosensitive and chemoresistant cells and tissue. Knockdown of TLR4 in SKOV-3 ovarian cells recovered chemosensitivity. Knockdown of MyD88 alone did not. MyD88 expression was down-regulated in differentiated embryonal carcinoma (NTera2) cells, supporting the MyD88+ cancer stem cell hypothesis. Our findings demonstrate that expression of MyD88 is associated with significantly reduced patient survival and altered microRNA levels and suggest an intact/functioning TLR4/MyD88 pathway is required for acquisition of the chemoresistant phenotype. Ex vivo manipulation of ovarian cancer stem cell (CSC) differentiation can decrease MyD88 expression, providing a potentially valuable CSC model for ovarian cancer.

A novel serum microRNA panel to discriminate benign from malignant ovarian disease

“…More recently MyD88 protein expression was shown to be a significantly poor factor in EOC by our group and others [49,62]. …”

“…The TLR4 gene is a validated target of the let-7i miRNA and our group has just recently demonstrated that overexpression of TLR4/MyD88 is an adverse prognostic marker in ovarian cancer [49]. We have shown that overexpression of TLR4 and MyD88 results in a shorter progression free survival and overexpression of MyD88 in a shorter overall survival.…”

Pooled Clustering of High-Grade Serous Ovarian Cancer Gene Expression Leads to Novel Consensus Subtypes Associated with Survival and Surgical Outcomes

“…The s2.IMM subtype showed significant up-regulation of antigen presentation machinery (e.g. TAP1 , PSMB8 and PSMB9 ); and its top subtype marker TAP1 was highly correlated with expression of PD-L1 (R Spearman = 0.72; p < 2.2E-16, Supplementary Figure 18), a marker has recently been associated with increasing tumor infiltrating T-cells and favorable prognosis in HGSOC (30). Finally, our analysis involving unsupervised clustering showed that the TGF-beta pathway is up-regulated in the mesenchymal subtype (q-value=1.5 x 10 −4 , Supplementary Table 13), which carries a worse prognosis (Figure 2A).…”

The inflammatory microenvironment in epithelial ovarian cancer: a role for TLR4 and MyD88 and related proteins

“…A few prior investigations demonstrated that high expression of either TLR4 or MyD88 in EOC tissues is associated with poor survival rates [8, 9, 21]. However, these studies failed to examine the prognostic importance of combined expression of TLR4 and MyD88, as suggested by in vitro studies.…”