RESUMEN
The incidence and associated mortality of lung cancer in tin miners in Gejiu County and farmers in Xuanwei Country, Yunnan Province have been very high in the world. Current published literatures on the molecular mechanisms of lung cancer initiation and progression in Gejiu and Xuanwei County are still controversial. Studies confirmed that microRNA-34a (miR-34a) functioned as a vital tumor suppressor in tumorigenesis and progression. However, the role and precise mechanisms of miR-34a and its regulatory gene network in initiation and progression of lung cancer in Gejiu and Xuanwei County, Yunnan Province, have not been elucidated. In the current study, we first found that miR-34a was downregulated in Gejiu lung squamous carcinoma YTMLC-90, Xuanwei lung adenocarcinoma XWLC-05, and other non-small cell lung carcinoma (NSCLC) cell lines, and miR-34a overexpression inhibited cell proliferation, migration and invasion, as well as induced cell apoptosis in YTMLC-90 and XWLC-05 cells. Our findings revealed that miR-34a is critical and cannot be considered as the area-specific non-coding RNA in initiation and progression of lung cancer in Gejiu and Xuanwei County. Next we revealed that miR-34a overexpression suppressed lung cancer growth and metastasis partially via increasing PTEN but reducing CDK6 expression that might lead to subsequent inactivation of PI3K/AKT pathway. Furthermore, our findings demonstrated that YY1 functioned as a tumor suppressor gene in initiation and progression of lung cancer in Gejiu and Xuanwei County. In conclusion, our findings in the study confirmed that miR-34a overexpression could simultaneously suppress tumor growth and metastasis and play a vital role in tumorigenesis and progression of NSCLC via increasing PTEN and YY1 expression, but decreasing CDK6. Most interestingly, our findings also raised doubts about the current ideas about these area-specific diseases.
RESUMEN
Lung cancer is the most prevalent and observed type of cancer in Xuanwei County, Yunnan, South China. Lung cancer in this area is called Xuanwei lung cancer. However, its pathogenesis remains largely unknown. To date, a number of studies have shown that microRNA (miR)218 functions as a tumor suppressor in multiple types of cancer. However, the role of miR218 and its regulatory gene network in Xuanwei lung cancer have yet to be investigated. The current study identified that the expression levels of miR218 in XWLC05 cells were markedly lower compared with those in immortalized lung epithelial BEAS2B cells. The present study also demonstrated that overexpression of miR218 could decrease cell proliferation, invasion, viability and migration in Xuanwei lung cancer cell line XWLC05 and NSCLC cell line NCIH157. Additionally, the results revealed that overexpression of miR218 could induce XWLC05 and NCIH157 cell apoptosis by arresting the cell cycle at G2/M phase. Finally, the present study demonstrated that overexpression of miR218 could lead to a significant increase in phosphatase and tensin homolog (PTEN) and YY1 transcription factor (YY1), and a decrease in Bcell lymphoma 2 (BCL2) and BMI1 protooncogene, polycomb ring finger (BMI1) at the mRNA and protein level in XWLC05 and NCIH157 cell lines. However, we did not observe any remarkable difference in the roles of miR218 and miR218mediated regulation of BCL2, BMI1, PTEN and YY1 expression in the progression of Xuanwei lung cancer. In conclusion, miR218 could simultaneously suppress cell proliferation and tumor invasiveness and induce cell apoptosis by increasing PTEN and YY1 expression, while decreasing BCL2 and BMI1 in Xuanwei lung cancer. The results demonstrated that miR218 might serve a vital role in tumorigenesis and progression of Xuanwei lung cancer and overexpression of miR218 may be a novel approach for the treatment of Xuanwei lung cancer.