Abstract
Hepatocellular carcinoma (HCC) is the most common liver cancer and has a poor prognosis. miR-302a is an important regulator of tumor occurrence and deterioration, while MAP3K2 and PBX3 genes are involved in cancer cell proliferation and apoptosis. In this study, the expression of miR-302a and MAP3K2/PBX3 were evaluated by qPCR in liver cancer cell lines. Next, the target relationship between miR-302a and MAP3K2/PBX3 was verified using luciferase assays. Meanwhile, the expression correlation between miR-302a and target genes was analyzed in cancer tissue and para-cancerous tissue. In addition, an increased miR-302a level in HepG2 cells and SMMC-7721 cells were achieved through transfection with miR-302a mimics, and the effects on HepG2 cell and SMMC-7721 cell proliferation, apoptosis and MAPK pathways were determined using MTT, flow cytometry, qPCR and western blot assays. The results showed that liver cancer cell lines exhibited low miR-302a expression and MAP3K2 and PBX3 were confirmed to be the target genes of miR-302a. Meanwhile, the HE results showed that cells became enlarged with loose cytoplasm and formed balloon-like lesions in HCC specimens and we found a significant negative correlation between miR-302a and MAP3K2/PBX3 expression. In addition, treatment with miR-302a mimics inhibited HepG2 cells and SMMC-7721 cells proliferation and increased the apoptosis rate. Further research revealed that the MAPK key factors p-p38, p-ERK1/2 and p-JNK were significantly reduced in miR-302a transfected cells and MAP3K2/PBX3 silenced cells. Besides, MAP3K2 and PBX3 overexpression in miR-302a mimics-treated cells exerted the opposite effects. In conclusion, miR-302a inhibited proliferation and promoted apoptosis in human hepatoma cells by targeting MAP3K2 and PBX3.
Highlights
Hepatocellular carcinoma (HCC) is one of the most frequently diagnosed cancers and a major cause of cancer-related death worldwide
The miR-302a expression level is significantly lower in gastric cancer (GC), and its low expression is frequently accompanied by positive lymph node metastasis, advanced TNM stage and great invasion depth and significantly associated with shorter disease-free and overall survival of GC patients[11]
Results showed that low miR-302a expression was found in liver cancer cell lines (HepG2, Bel-7402, SMMC-7721 and PLC) compared with control group (L02) cells (Fig. 1A) (P < 0.01)
Summary
HCC is one of the most frequently diagnosed cancers and a major cause of cancer-related death worldwide. PBX3 is found to participate in the regulation of a variety of tumors, such as glioma[15], gastric cancer (GC)[20] and invasive prostate cancer[21], and elevated PBX3 expression significantly promote tumor cell proliferation. Both MAP3K2 and PBX3 participate in HCC regulation[20,22,23,24]. PBX3 knockdown inhibits MAPK pathway activation in glioma cells. The results indicate miR-320 may suppress glioma cell growth through targeting PBX3 and regulating MAPK pathway[30]. The data will lay a theoretical foundation for HCC early diagnosis and treatment
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