MiR-93 Promotes Tumorigenesis and Metastasis of Non-Small Cell Lung Cancer Cells

NSCLC and miR-93

Background

  • Non-small cell lung cancer (NSCLC) accounts for approximately 85% of clinical lung cancer cases.
  • MicroRNA-93 (miR-93) acts as an oncomiR in many human cancers, including NSCLC.
  • The mechanism of miR-93 involvement in NSCLC was previously unknown.
  • This study aimed to reveal and explain this mechanism to contribute to developing new diagnostic biomarkers and individualized therapeutic tools.

Methods

  • MiR-93 expression was determined in NSCLC cell lines A549, H1975, and H1299.
  • Cells were transfected with:
    • Control plasmids (Mock group).
    • MiR-93 overexpression plasmids (miR-93 Up group).
    • MiR-93 inhibitor plasmids (miR-93 Down group).
  • Effects of miR-93 on cell proliferation, migration, and invasion were determined.
  • In vivo effects of miR-93 on tumor metastasis were determined in an NSCLC xenograft mouse model.
  • Molecular mechanisms were investigated via dual luciferase reporter assay and western blotting.

Results

  • MiR-93 expression levels were significantly greater in NSCLC cell lines than in normal lung epithelial cells.
  • Cell proliferation, migration, and invasion were significantly stimulated by miR-93 upregulation (all P<0.05) and inhibited by miR-93 downregulation.
  • Dual luciferase reporter assay demonstrated that miR-93 directly bound with the 3′-untranslated region of the tumor suppressor gene LKB1.
  • Western blotting analysis indicated that miR-93 activated the PI3K/Akt pathway by inhibiting LKB1, PTEN, and p21.
  • Increased expression of miR-93 induced significant hepatic metastasis of lung cancer in the xenograft mouse model.

MiR-93 effects on cell lines

  • MiR-93 expression in A549, H1975, and H1299 cells was 2.57, 3.17, and 3.72-fold higher, respectively, than in BEAS-2B cells (all P<0.001).
  • The number of colonies formed by A549 cells in the Mock group, the miR-93 Up group, and the miR-93 Down group were 198±\pm18, 266±\pm25, and 123±\pm23, respectively.
  • The colonies formed by H1299 cells in the Mock group, the miR-93 Up group, and the miR-93 Down group numbered 57±\pm5, 86±\pm11, and 24±\pm10, respectively.

MiR-93 and LKB1

  • Analysis indicated that LKB1, PTEN, and CDKN1A were candidate targets of miR-93.
  • 293T cells transfected with miR-93 mimic had 64% lower luciferase activity than parental 293T cells, 293T cells transfected with the control plasmid, or 293T cells transfected with the plasmid expressing LKB1 mutant 3′-UTR (all P<0.01).

In vivo

  • Tumors from miR-93 Down A549 cells had significantly lower rates of pleural dissemination and hepatic metastasis than controls.
  • The miR-93 Down group had a lower rate of pleural dissemination than the Mock group (80% vs 100%, P<0.05) and no hepatic metastasis (0 vs 80%, P<0.01).
  • The survival time of miR-93 Down group was significantly longer than that of Mock group (P=0.039), with the median survival time was 58 days vs 53 days.

Conclusion

  • Overexpression of miR-93 facilitates tumorigenesis and metastasis of NSCLC.
  • These findings provide novel insight into the mechanism of miR-93 involvement in NSCLC, suggesting that miR-93 may serve as a potential therapeutic target.
  • MiR-93 promotes lung cancer proliferation and metastasis both in vitro and in vivo and identified LKB1 as a novel target of miR-93 in NSCLC.
  • MiR-93 inhibits LKB1, PTEN, and CDKN1A, thereby activating proliferation and metastases through the PI3K/Akt pathway in NSCLC.
  • The tumorigenic activity of miR-93 is mediated by activation of the oncogenic PI3K/Akt pathway through inhibition of LKB1, PTEN, and p21 expression.