Haptoglobin expression correlates with tumor differentiation and five-year overall survival rate in hepatocellular carcinoma

Abstract

Elevated serum haptoglobin (Hp) is identified as a prognostic marker in multiple types of solid tumors, which is correlated with poor prognosis. HCC is one of the major causes of cancer deaths in worldwide, which remains poor prognosis and is clinically urgent for discovering early diagnostic markers. However, except for serum Hp, the correlation of tumor Hp expression with hepatocellular carcinoma (HCC) progression is still unclear. In this study, we evaluated and identified the tissue Hp expression as a prognostic marker to predict the survival rate of HCC patients. To evaluate the prognostic value of Hp expression for HCC, two cohorts were enrolled in our study, including total 130 matched pair tissue sections (both adjacent non-tumorous and tumor tissue derived from same patient) of HCC patients from Changhua Christian Hospital (CCH) and total 316 RNA-seq data with clinical information of HCC patients from The Cancer Genome Atlas (TCGA) database. In contrast to other types of cancers, HCC tumor tissues have lower Hp protein expression in CCH cohort and have lower Hp mRNA expression in TCGA cohort as compared with adjacent non-tumorous tissues (p < 0.001). Moreover, lower Hp expression is significantly correlated with different stages of HCC cancer differentiation in CCH cohort (one-way ANOVA, p < 0.001). Most importantly, lower Hp expression is highly correlated with poor five-year overall survival rate in TCGA cohort (p < 0.01). Based on our data, we conclude that tissue Hp expression positively correlates with better HCC tumor differentiation and increased five-year overall survival rate of HCC patients. The results indicated that tissue Hp is potentially a prognostic marker for HCC patients. Our findings may further provide a new insight of effective treatments along with biopsy diagnosis of HCC patients.

Fig 1. Hp protein expression and cancer differentiation analysis of CCH HCC patients.

(A) An example of Hp IHC staining in adjacent non-tumorous tissues and tumor tissues under 100X and 400X magnification. (B) Hp protein expression analysis between matched pair adjacent non-tumorous tissues and tumor tissues of HCC patients from CCH (p < 0.001). (C) Boxplot of Hp protein expression in adjacent non-tumorous tissues and three stages HCC cancer differentiation (well, moderate, and poor) (p < 0.001). (D) The schematic diagram interpreted the correlation between Hp expression and HCC cancer differentiation (p < 0.001). (E) An example of IHC staining for measuring the Hp protein expression at the junction area between adjacent non-tumorous tissue and tumor tissue.

Fig 2. Hp gene expression and five-year overall survival rate analysis in TCGA HCC patients.

(A) The boxplot demonstrated Hp gene expression level between adjacent non-tumorous tissues and tumor tissues in TCGA HCC patients (p < 0.001). (B) The Hp expression plot showed a total of 316 HCC patients that are ordered by Hp mRNA expression values (RPKM) from the lowest to the highest. The X-axis represents the accumulative number of HCC patients and the Y-axis represents Hp expression value in RPKM. The dashed line shows optimal cut point which dichotomized HCC patients into high (red) and low (green) Hp expression groups. (C) The p-value plot displayed the survival significance of each potential cut point of Hp expression measurement. According to each cut point, HCC patients are dichotomized into high and low Hp expression groups, and are calculated by log-rank test for survival significances. The X-axis represents the accumulative number of HCC patients on the order same as the Hp expression plot in panel B and the Y-axis represents raw p-values on a log10 scale. The optimal cut point is colored in red and is indicated by dashed line. (D) The Kaplan-Meier plot of HCC survival analysis. HCC patients were dichotomized into low Hp expression group (n = 34) and high Hp expression group (n = 282). The Kaplan-Meier survival curve showed high tumor Hp expression group has increased five-year overall survival rate, comparing with low tumor Hp expression group in TCGA HCC patients (p < 0.001).