Study of potential targets of miR-143 in cervical cancer

Abstract

Cervical cancer is a common gynaecological malignancy worldwide, with more than 450,000 incidences every year. Its etiology has been well documented to be associated with persistent infection with high-risk genotypes of human papillomavirus (HPV). The carcinoma can be screened by convention Pap smear and liquid-based cytology. Although preventable, cervical cancer remains a primary cause of death from cancer in developing countries where cytological screening is not so available. In the past decades, many studies have been carried out to explore molecular screening or diagnosis of cervical cancer, such as HPV DNA testing, histological or cytological biomarkers.

Micro RNAs, small non-coding RNA molecules of 18-25 nucleotides in length, areaberrantly expressed in various cancers. MiR-143 was reported consistently downregulated in cervical cancer tissues and cell lines, but its functional roles in cervical carcinogenesis has not been clearly illustrated.

Ten miR-143 downstream target genes were chosen and their expression levels in five cervical cancer cell lines (HeLa, SiHa, CaSki, C4-I and C33A) were investigated. In general, the gene expressions of candidates are upregulated in our cell lines with lowmiR-143 level. To further identify specific miR-143 targets in cervical cancer for biomarkers, protein expressions of TARDBP, ERK5, KRAS and PHF6were significantly downregulated upon miR-143 overexpression. Hence, miR-143 level is inversely correlated with the mRNA and protein expressions of these target genes.

Immunohistochemical study of ERK5 and TARDBP on FFPE samples including normal cervix, CINs and SCC cases showed that both ERK5 and TARDBP were positively stained in SCC samples, whereas weaker staining was found in CINs (both LSILs and HSILs) for both antigens. Thus, the intensity of positive staining ascended with the histological grading: LSIL, HSIL and SCC samples. Such differential expression pattern supports ERK5 and TARDBP as specific markers for high grade cancerous lesions.

In summary, two targets of miR-143, ERK5 and TARDBP, could be specific markers for high-grade lesion of cervical cancer. This is supported by their transcript and protein expressions inversely associated with miR-143 level, and that their strong immunohistochemical positivity in SCC samples. Their underlying molecular mechanisms involved in carcinogenesis and possible future applications require more in-depth researches.