Impact of bromodomain-containing protein 4 (BRD4) and intestine-specific homeobox (ISX) expression on the prognosis of patients with hepatocellular carcinoma' for better clarity

Abstract

Epigenetic regulation is important for cancer tumor metastasis and progression, including lung and liver cancer. However, the mechanism of epigenetic regulation in liver cancer leaves much to be discussed. According to a previous study, p300/CBP-associated factor (PCAF) mediated epithelial-mesenchymal transition (EMT) and promotes cancer metastasis by recruiting intestine-specific homeobox (ISX) and bromodomain-containing protein 4 (BRD4) in lung cancer. To figure out whether the three genes are also expressed in patients with hepatocellular carcinoma (HCC) or not, and their correlation with patients' outcome, BRD4, PCAF, and ISX messenger RNA (mRNA) expression levels in 377 patients with HCC were investigated using quantitative polymerase chain reaction and confocal fluorescence imaging. The correlation of the gene expression (PCAF, ISX, and BRD4) in liver cancer is also being investigated. Here, we show that the mRNA expression of PCAF, BRD4, and ISX in 377 paired specimens from patients with HCC, and the adjacent normal tissues exhibited a tumor-specific expression pattern, highly correlated with disease pathogenesis, patient survival time, progression stage, and poor prognosis. The results show that ISX and BRD4 can potentially be a target for improving the survival rate.

Keywords: BRD4; HCC; ISX.

FIGURE 1

Linear trend analyze of ISX and BRD4. (A‐C), The mRNA expression of ISX has positive correlation with the tumor grade(a), size(B), and stage(C). (D‐F), The mRNA expression of BRD4 has positive correlation with the tumor grade(D), size(E), and stage(F)

FIGURE 2

Western blot analysis of ISX, BRD4, and PCAF in HCC tissues (T1‐5) and adjacent liver tissues (A1‐5). Actin was used as a loading control

FIGURE 3

PCAF, BRD4 determined by Western blot in anti‐ISX immunoprecipitates of tumor tissues from patients with liver cancer

FIGURE 4

mRNA expression of ISX strongly correlated with those of BRD4(A) and PCAF(B) in patients with HCC (Pearson's correlation coefficient, r = 0.8587 and 0.8028, respectively, p < 0.0001)

FIGURE 5

Kaplan–Meier survival curve analysis. (A–C), The Kaplan–Meier survival curve was used to analyze survival correlation between patients (n = 377) with HCC and ISX (A),BRD4(B), and PCAF (C) levels. On the basis of the cut‐off values of fold differences, the study population was dichotomized into the “high” and “low” expression groups. p‐values were calculated by log‐rank (Mantel–Cox) test comparing the two Kaplan–Meier curves. (D and E), The Kaplan–Meier survival curve was used to analyze survival correlation between patients (n = 377) with HCC and ISX–BRD4 (D) and BRD4–PCAF (E) levels. On the basis of the cut‐off values of fold differences, the study population was dichotomized into the “high” and “low” expression groups. p‐values were calculated by log‐rank (Mantel–Cox) test comparing the two Kaplan–Meier curves