Integrator complex subunit 6 (INTS6) inhibits hepatocellular carcinoma growth by Wnt pathway and serve as a prognostic marker

Background: Integrator complex subunit 6 (INTS6) was found to play a tumour suppressing role in certain types of solid tumours. In this study, we wanted to determine the expression level of INTS6 in hepatocellular carcinoma (HCC) and evaluate its clinical characteristics and mechanisms in HCC patients (Lui and Lu, European Journal of Cancer, 51:S94, 2015).

Methods: First, we used a microarray analysis to explore the mRNA expression levels in HCC and paired normal liver tissues; second, we used qRT-PCR to measure the INTS6 mRNA levels in a cohort of 50 HCC tissues and adjacent normal liver tissues; third, we used Western blot analyses to detect the INTS6 protein levels in 20 paired HCC and normal liver tissues; fourth, we used immunohistochemistry to determine the INTS6 expression levels in 70 archived paraffin-embedded HCC samples. Finally, we investigated the suppressive function of INTS6 in the Wnt pathway.

Results: Herein, according to the microarray data analysis, the expression levels of INTS6 were dramatically down-regulated in HCC tissues vs. those in normal liver tissues (p<0.05). qRT-PCR and Western blot analyses showed that the INTS6 mRNA and protein expression was significantly down-regulated in tumour tissues compared to the adjacent normal liver tissues (p<0.05). Immunohistochemical assays revealed that decreased INTS6 expression was present in 62.9% (44/70) of HCC patients. Correlation analyses showed that INTS6 expression was significantly correlated with serum alpha-fetoprotein levels (AFP, p =0.004), pathology grade (p =0.005), and tumour recurrence (p =0.04). Kaplan-Meier analysis revealed that patients with low INTS6 expression levels had shorter overall and disease-free survival rates than patients with high INTS6 expression levels (p =0.001 and p =0.001). Multivariate regression analysis indicated that INTS6 was an independent predictor of overall survival and disease-free survival rates. Mechanistically, INTS6 increased WIF-1 expression and then inhibited the Wnt/β-catenin signalling pathway.

Conclusion: The results of our study show that down-regulated INTS6 expression is associated with a poorer prognosis in HCC patients. This newly identified INTS6/WIF-1 axis indicates the molecular mechanism of HCC and may represent a therapeutic target in HCC patients.