Piwil2 modulates the proliferation and metastasis of colon cancer via regulation of matrix metallopeptidase 9 transcriptional activity.

Piwi-like protein 2 (Piwil2) has recently emerged as a putative oncogene which is amplified in several human malignancies. However, the role of Piwil2 in colon cancer remains poorly understood. The aim of this study was to investigate the clinical and pathological significance of Piwil2, and the possible role in the proliferation and metastasis of colon cancer. Primary colon cancer paired with adjacent normal colon tissue and lymph node metastasis (LNM) lesions in 66 patients' tissue microarrays (TMA) were used to determine the expression of Piwil2. Knocked down Piwil2 expression in SW620 and SW480 colon cancer cell lines was performed to evaluate the role of Piwil2 in cell proliferation, invasion, metastasis in vitro and tumorigenicity in vivo. The possible roles of Piwil2 in the regulation of a 2 kb matrix metallopeptidase 9 (MMP9) promoter fragment and on the regulation of apoptotic pathways were evaluated by using a luciferase reporter construct and Western blots, respectively. Significantly higher expression levels of Piwil2 were observed in primary colon cancer tissue and in LNM in comparison with normal colon mucosa. Piwil2 expression significantly correlated with more aggressive clinical and pathological parameters with poorer five-year metastasis-free survival and overall survival. Piwil2 silencing significantly reduced cancer cell proliferation, colony formation ability and increased apoptosis in vitro and inhibited tumor growth in vivo. Piwil2 knockdown also attenuated migration and invasion of colon cancer cells via modulation of MMP9 transcriptional activities. Our results indicate that Piwil2 moderates the proliferation and metastasis potential of colon cancer.