Examination of the epidermal growth factor 3 (HER3) dysregulations in hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide with a particularly high mortality rate. Treatment options for HCC are limited. Curative treatments including surgical resection and liver transplantation are only applicable to early diagnosed patients. For advanced HCC patients, the currently available first-line molecularly targeted medications are suffering from low rates of response and high inter-patients variability providing limited survival benefits. Receptor tyrosine kinases (RTKs) are plasma membrane-associated protein kinases which control the activation of intracellular signal transductions in response to the extracellular stimuli. Activation of specific RTKs has been implicated in various kinds of human cancers, and pharmacological inhibition of cancer associated RTKs is one of the key strategies of modern targeted therapy. However, a comprehensive and systematic assessment of the RTKs dysregulations in terms of expression and mutation in HCC is still much awaited. In this study, RNA-sequencing analysis was performed in paired HCC tissues to examine the expression profiles of 58 RTKs. Also, the mutational status of these RTKs in HCC tissues was examined by targeted DNA-sequencing analysis. Our systemic analyses have revealed that Epidermal Growth Factor Receptor 3 (HER3) was significantly upregulated and recurrently mutated in HCC. Independent qPCR analysis for HER3 in 101 paired HBV-associated HCC tumor and non-tumorous samples validated that HER3 was upregulated in HCC. More importantly, upregulation of HER3 was found to be significantly correlated with the presence of metastatic features of HCC including tumor microsatellite formation (p=0.015) and venous invasion (p=0.001). Neuregulin-1 (NRG-1) is the best-known ligand for HER3. Stimulation of HER3 activation by the ligand NRG-1 could induce HER3 phosphorylation, and activate the downstream PI3K/AKT and MAPK signaling pathways, and signficantly promoted the proliferation and migration of HCC cells. Conversely, CRISPR/Cas9-mediated HER3 knockout in Huh7 and PLC cells significantly reduced the NRG-1 induced functional changes. Consistently, our preliminary results demonstrated that HER3 knockout Huh7 cells forms relatively smaller tumors in a subcutaneous tumor xenograft model in vivo. Together, our results demonstrated that HER3 dysregulation plays a supporting role in HCC development. Targeting HER3 may potentially derive new therapeutic strategy for treatment of HCC.