miR-10b Downregulated by DNA Methylation Acts as a Tumor Suppressor in HPV-Positive Cervical Cancer via Targeting Tiam1

Abstract

Background/Aims: microRNAs (miRNAs) are known to act as oncogenes or tumor suppressors in diverse cancers. Although miR-10b is an oncogene implicated in many tumors, its role in cervical cancer (CC) remains largely unclear. Here, we investigated the function and underlying mechanisms of miR-10b in human CC. Methods: Quantitative RT-PCR was used to measure miR-10b expression in CC and normal tissues, and its association with clinicopathologic features was analyzed. Methylation of CpG sites in the miR-10b promoter was analyzed by methylation sequencing. Cell proliferation, apoptosis, migration, and invasion assays were used to elucidate the biological effects of miR-10b and expression of the target gene was assayed with Western blot. Results: miR-10b was downregulated in CC tissues compared with normal tissues, and less miR-10b expression was associated with larger tumors, vascular invasion and HPV-type 16 positivity. miR-10b expression decreased in HeLa (HPV18-positive) and SiHa (HPV16-positive) cells compared with C-33A (HPV-negative), but increased after treatment with 5-Aza-CdR. Methylation ratio of site -797 in the miR-10b promoter in C-33A was lower than that in HeLa and SiHa. Further analysis indicates that site -797 is located within a transcription factor AP-2A (TFAP2A) binding element. Functionally, overexpression of miR-10b in HeLa and SiHa suppressed cell proliferation, migration and invasion, and induced apoptosis and miR-10b downregulation had opposite effects. Mechanistically, T-cell lymphoma invasion and metastasis 1 (Tiam1) was identified as a direct and functional target of miR-10b. Conclusion: miR-10b acts as a tumor suppressor in CC by suppressing oncogenic Tiam1, and its expression may be downregulated through methylation of TFAP2A binding element by HPV.

Tiam1 high expression is associated with poor prognosis in solid cancers

“…[41] Consistently, many studies implied that Tiam1 overexpression exhibited an accelerative effect in regulating malignant cell proliferation in a wide range of cancers, including hepatocellular carcinoma, [42–44] oral cancer, [45] lung cancer, [35] esophageal cancer, [46,47] pancreatic cancer, [13,48] ovarian cancer, [49] cervical cancer, [33,50] colon cancer, [51–54] gastric cancer, [55] osteosarcoma, [56,57] nasopharyngeal cancer, [14] laryngeal cancer, [31] and cholangiocarcinoma. [58] Besides, lots of studies indicated that upregulation of Tiam1 could protect malignant cells from apoptotic death in esophageal cancer, [46,47] cervical cancer, [50] laryngeal cancer, [31] retinoblastoma, [59] and colon cancer. [54] Third, a few recent studies demonstrated that Tiam1 was able to promote of angiogenesis cervical [33] and lung cancer.…”

MicroRNA Regulation of the Small Rho GTPase Regulators—Complexities and Opportunities in Targeting Cancer Metastasis

“…The stable expression of these two miRNAs inhibited Rac activation, cell growth, migration and invasion, as well as induced apoptosis by regulating TIAM1 expression. Furthermore, these results translated to mice as the expressions of miR-10a and miR-10b were found to reduce tumor growth and metastasis in esophageal squamous cell carcinoma [391] and cervical cancer [393], respectively. It was found that miR-10b was epigenetically silenced by DNA methylation [393,394], suggesting that demethylating agents could reactivate tumor suppressors to combat cancer progression.…”

“…Although originally identified as a Rac-specific GEF, studies have also identified GEF effects on RhoA and CDC42, albeit to a less efficient extent [226], where TIAM1 operates as a potent oncogene. Two members of the miR-10 family (miR-10a and miR-10b) have been shown to function as tumor suppressors by directly targeting TIAM1 [391][392][393][394]. The expression of these two miRNAs were found to be significantly reduced in tumor tissue compared to the matched normal tissue [391,393,394].…”

“…Two members of the miR-10 family (miR-10a and miR-10b) have been shown to function as tumor suppressors by directly targeting TIAM1 [391][392][393][394]. The expression of these two miRNAs were found to be significantly reduced in tumor tissue compared to the matched normal tissue [391,393,394]. The stable expression of these two miRNAs inhibited Rac activation, cell growth, migration and invasion, as well as induced apoptosis by regulating TIAM1 expression.…”

Microarray screening of differentially expressed genes after up-regulating miR-205 or down-regulating miR-141 in cervical cancer cells

“…Most mature miRNAs inhibit gene expression by cutting target messenger RNA(mRNAs) or inhibiting mRNAs’ translation by binding to the 3 ’-UTRs of mRNAs. (6) More and more reports have shown that miRNA plays an important role in the proliferation, apoptosis, invasion and migration of tumor cells. Abnormal expression of miRNA can be used for tumor classification, diagnosis and prognosis.…”