Abstract
Epithelial ovarian cancer (EOC) is a leading cause of cancer-related mortality in the United States due to the late-stage disease at diagnosis. Overexpression of GRP78 and PDI following endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) promote growth and invasion in cancer. To identify novel prognostic biomarkers in EOC, here we determined the expression of ER stress-associated proteins (GRP78, ATF6 and PERK) and correlated with clinical outcome in EOC. Tissue microarray (TMA) samples from 415 tissues collected from three cancer centers (UM, USC, and KCCRI) were used to assess the expression levels of ER-associated proteins using immunohistochemistry (IHC). We observed that the expression levels of GRP78 (p < 0.0001), ATF6 (p < 0.0001), and PERK (p < 0.0001) were significantly increased in specimens of EOC compared to normal tissues, including in the serous subtype (p < 0.0001). Previously we reported that high expression of PDI correlated with poor patient survival in EOC. Here we showed that overexpression of GRP78 and PDI protein expression correlated with poor patient survival (p = 0.03), while low expression of combined GRP78 and PDI correlated with better survival (p = 0.01) in high-grade serous. The increased expression of ER stress-associated proteins in EOC suggests a role for ER stress and the UPR in EOC. More importantly, our results demonstrate that GRP78 and PDI are potential biomarkers for EOC and could be used as dual prognostic markers.
Highlights
Epithelial ovarian cancer (EOC) is a leading cause of cancer-related mortality in the United States due to the late-stage disease at diagnosis
GRP78 is well-known as a master regulator of endoplasmic reticulum (ER) stress, the clinicopathologic significance of GRP78 in EOC has not been well studied
We demonstrate that the expression of GRP78 is higher in EOC patient tissues compared to non-tumor tissues, but more importantly, it correlates with poor patient survival in high-grade serous type EOC
Summary
Epithelial ovarian cancer (EOC) is a leading cause of cancer-related mortality in the United States due to the late-stage disease at diagnosis. Overexpression of GRP78 and PDI following endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) promote growth and invasion in cancer. To identify novel prognostic biomarkers in EOC, here we determined the expression of ER stress-associated proteins (GRP78, ATF6 and PERK) and correlated with clinical outcome in EOC. The activation of the unfolded protein response (UPR) and overexpression of chaperone proteins, 78 kDa glucose-regulated protein (GRP78) and protein disulfide isomerase (PDI), following ER stress promotes growth, survival, and invasion[7,8,9,10,11,12,13]. Dysfunction of PDI in certain diseases causes additional ER stress due to the accumulation of unfolded proteins leading to initiation of the UPR. Evidence suggests that targeting GRP78 and PDI could be an efficacious therapeutic option for EOC28
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