Human Epididymis Secretory Protein 4 (HE4) Compromises Cytotoxic Mononuclear Cells via Inducing Dual Specificity Phosphatase 6.

Nicole E James,Richard G Moore,Kyu-Kwang Kim,Rakesh K Singh,Clinton O Chichester,Ting C Zhao,Evelyn Cantillo,Naohiro Yano,Rachael B Rowswell-Turner,Matthew T Oliver,Paul A Disilvestro,Jennifer R Ribeiro

doi:10.3389/fphar.2019.00216

Abstract

While selective overexpression of serum clinical biomarker Human epididymis secretory protein 4 (HE4) is indicative of ovarian cancer tumorigenesis, much is still known about the mechanistic role of the HE4 gene or gene product. Here, we examine the role of the secretory glycoprotein HE4 in ovarian cancer immune evasion. Through modified subtractive hybridization analyses of human peripheral blood mononuclear cells (PBMCs), we have characterized gene targets of HE4 and established a preliminary mechanism of HE4-mediated immune failure in ovarian tumors. Dual specificity phosphatase 6 (DUSP6) emerged as the most upregulated gene in PBMCs upon in vitro exposure to HE4. DUSP6 was found to be upregulated in CD8+ cells and CD56+ cells. HE4 exposure reduced Erk1/2 phosphorylation specifically in these cell populations and the effect was erased by co-incubation with a DUSP6 inhibitor, (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI). In co-culture with PBMCs, HE4-silenced SKOV3 human ovarian cancer cells exhibited enhanced proliferation upon exposure to external HE4, while this effect was partially attenuated by adding BCI to the culture. Additionally, the reversal effects of BCI were erased in the co-culture with CD8+ / CD56+ cell deprived PBMCs. Taken together, these findings show that HE4 enhances tumorigenesis of ovarian cancer by compromising cytotoxic CD8+ and CD56+ cells through upregulation of self-produced DUSP6.

Highlights

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer death in women, and the deadliest of all gynecologic cancers
Incubations with BCI (1 μM) alone showed no significant effects on SKOV3 cell proliferation, Ki67 expression, or apoptosis. These findings suggest that Human epididymis secretory protein 4 (HE4) enhances tolerance of cancer cells against immunocompetent mononuclear cells via the up-regulation of Dual specificity phosphatase 6 (DUSP6) in peripheral blood mononuclear cells (PBMCs)
We have begun to delineate another vital function of HE4 in disrupting immune cell function, which has implications for immune system targeting of tumor cells

Summary

Introduction

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer death in women, and the deadliest of all gynecologic cancers. Standard first-line therapy consists of debulking surgery followed by taxane-platinum chemotherapy (Kim et al, 2012) While targeted therapies such as bevacizumab and olaparib are approved to treat EOC, these treatments have not led to an improvement in overall survival (Yap et al, 2009). One promising new area of investigation lies in understanding how tumors develop immune tolerance and evade elimination by cytotoxic lymphocytes Immune checkpoint molecules such as PD-1, CTLA4, TIM3, IDO, and others act to suppress T cell activation, helping tumor cells escape immune targeting and elimination (Zhao and Subramanian, 2018). A greater understanding of factors that contribute to immune evasion in EOC is required in order to develop treatments that have the ability to reactivate the body’s immune response to tumors

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