CLIC1 and CLIC4 complement CA125 as a diagnostic biomarker panel for all subtypes of epithelial ovarian cancer

Bipradeb Singha,Ronny Drapkin,Rugang Zhang,Sandra L Harper,Qin Liu,David W Speicher,Mark G Cadungog,Stephanie Jean,Mark E Borowsky,Aaron R Goldman,Katherine M Aird,Benjamin G Bitler

doi:10.1038/s41598-018-32885-2

Abstract

New plasma and tissue biomarkers of epithelial ovarian cancer (EOC) could improve early diagnosis and post-diagnosis clinical management. Here we investigated tissue staining and tissue secretion of CLIC1 and CLIC4 across EOC subtypes. CLIC1 and CLIC4 are two promising biomarkers we previously showed were elevated in EOC patient sera. Individually, CLIC1 or CLIC4 stained larger percentages of malignant tumors across all EOC subtypes compared with CA125, particularly early stage and mucinous tumors. CLIC4 also stained benign tumors but staining was limited to nuclei; whereas malignant tumors showed diffuse cellular staining of stromal and tumor cells. Both proteins were shed by all EOC subtypes tumors in short term organ culture at more consistent levels than CA125, supporting their potential as pan-subtype serum and tissue biomarkers. Elevated CLIC4 expression, but not CLIC1 expression, was a negative indicator of patient survival, and CLIC4 knockdown in cultured cells decreased cell proliferation and migration indicating a potential role in tumor progression. These results suggest CLIC1 and CLIC4 are promising serum and tissue biomarkers as well as potential therapeutic targets for all EOC subtypes. This justifies development of high throughput serum/plasma biomarker assays to evaluate utility of a biomarker panel consisting of CLIC1, CLIC4 and CA125.

Highlights

Epithelial ovarian cancer (EOC) consists of four major subtypes that are quite different from each other at the genetic level, and most previously identified biomarkers differ significantly between subtypes[1]
In this study we evaluated the utility of CLIC1 and CLIC4 as EOC tissue biomarkers because we previously showed they are promising EOC serum biomarkers[25,27] and have intriguing, but incompletely understood roles in EOC tumor progression
These results suggest that a biomarker panel consisting of CLIC1, CLIC4 and cancer antigen 125 (CA125) should outperform individual biomarkers for staining ovarian tumor specimens and could potentially be used in a serum screen assay for all EOC subtypes

Summary

Introduction

Epithelial ovarian cancer (EOC) consists of four major subtypes (serous, clear cell, endometrioid, and mucinous) that are quite different from each other at the genetic level, and most previously identified biomarkers differ significantly between subtypes[1]. IHC can provide additional insight as to whether proteins of interest are produced by all EOC subtypes in parallel with determining their potential utility as tissue biomarkers Both CLICs stained tumor tissues from all EOC subtypes, including early stage and low-grade tumors, which resulted in better sensitivity than CA125 alone at the tissue level. Elevated CLIC4 expression was a negative indicator of patient survival, and knockdown of either CLIC4 or CLIC1 in cultured cells significantly decreased cell migration and colony formation These results suggest that a biomarker panel consisting of CLIC1, CLIC4 and CA125 should outperform individual biomarkers for staining ovarian tumor specimens and could potentially be used in a serum screen assay for all EOC subtypes. Taken together with the prior patient serum studies, the IHC and tumor secreteome strongly indicate that investing the needed effort and cost to develop high throughput serum/plasma assays for CLIC1 and CLIC4 are justified

Methods

Results

Conclusion