The lncRNA HULC functions as an oncogene by targeting ATG7 and ITGB1 in epithelial ovarian carcinoma

Cell Death Dis. 2017 Oct 12;8(10):e3118. doi: 10.1038/cddis.2017.486.

Abstract

Highly upregulated in liver cancer (HULC) is a long noncoding RNA (lncRNA), which has recently been identified as a key regulator in the progression of hepatocellular carcinoma, gliomas and gastric cancer. However, its role in epithelial ovarian carcinoma (EOC) remains unknown. In this study, HULC expression was examined in EOC, borderline and benign ovarian tumors, and normal ovarian tissues by RT-PCR. Ovarian cancer cell phenotypes, as well as autophagy-associated proteins were examined after HULC overexpression or downregulation by plasmid or small interfering RNA (siRNA) transfection, respectively. LncRNA-protein interactions were examined by ribonucleoprotein immunoprecipitation (RIP) assays. We found that HULC expression levels were higher in EOC tissues than normal samples. HULC overexpression induced cell proliferation, migration, invasion, whereas reduced cell apoptosis in vitro and induced tumor growth in vivo. In contrast, downregulation of HULC by siRNA transfection reduced cell proliferation, migration and invasion, and induced cell apoptosis and autophagy. Our results showed that HULC overexpression reduced ATG7, LC3-II and LAMP1 expression, while inducing SQSTM1 (P62) and ITGB1 expression. HULC downregulation had the opposite effects. Furthermore, RIP indicated that ATG7 interacted with HULC; ATG7 downregulation also induced cell proliferation, reduced apoptosis and inhibited autophagy in vitro by reducing LC3-II and LAMP1 expression, while inducing SQSTM1 expression. Furthermore, ATG7 co-transfection with HULC reversed the oncogenic effects of HULC both in vitro and in vivo; however, downregulating ATG7 did not affect cell migration and invasive ability. We found that ITGB1 siRNA co-transfection with HULC reversed the function of HULC in inducing ovarian cancer cell migration and invasive ability. Taken together, our results show that HULC may promote ovarian carcinoma tumorigenesis by inhibiting ATG7 and inducing progression by regulating ITGB1.

MeSH terms

  • Animals
  • Apoptosis / genetics
  • Autophagy / genetics
  • Autophagy-Related Protein 7 / genetics
  • Autophagy-Related Protein 7 / metabolism*
  • Carcinogenesis / genetics*
  • Carcinoma, Ovarian Epithelial
  • Cell Line, Tumor
  • Cell Movement / genetics
  • Cell Proliferation / genetics*
  • Female
  • Humans
  • Integrin beta1 / genetics
  • Integrin beta1 / metabolism*
  • Lysosomal Membrane Proteins / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Microtubule-Associated Proteins / metabolism
  • Neoplasms, Glandular and Epithelial / genetics*
  • Neoplasms, Glandular and Epithelial / pathology*
  • Oncogenes / genetics
  • Ovarian Neoplasms / genetics*
  • Ovarian Neoplasms / pathology*
  • RNA Interference
  • RNA, Long Noncoding / genetics*
  • RNA, Small Interfering / genetics
  • Sequestosome-1 Protein / genetics
  • Sequestosome-1 Protein / metabolism

Substances

  • HULC long non-coding RNA, human
  • Integrin beta1
  • LAMP1 protein, human
  • Lysosomal Membrane Proteins
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • RNA, Long Noncoding
  • RNA, Small Interfering
  • SQSTM1 protein, human
  • Sequestosome-1 Protein
  • ATG7 protein, human
  • Autophagy-Related Protein 7