HIWI2 induces G2/M cell cycle arrest and apoptosis in human fibrosarcoma via the ROS/DNA damage/p53 axis

Piwi-like RNA-mediated gene silencing 4 (PIWIL4) or HIWI2, are seen deregulated in human cancers and possibly play critical roles in tumorigenesis. It is unknown what role HIWI2 plays in the regulation of fibrosarcoma, an early metastatic lethal type of soft tissue sarcoma (STS). The present study aimed to investigate the role of HIWI2 in the tumorigenesis of fibrosarcoma. The expression of HIWI2 in HT1080 fibrosarcoma cells was determined by qRT-PCR and western blotting. The MTT assay, colony formation assay, cell cycle, and PE-AnnexinV/7AAD apoptosis assay using flow cytometry, DNA laddering assay, comet assay, and γH2AX accumulation assay were performed to study the effect of HIWI2 overexpression in HT1080 cells. Further, the effect of silencing of HIWI2 was determined by cell viability assay, transwell migration, and invasion assay. HIWI2 is under-expressed in STS cell lines and tissues, which is associated with poor disease-free survival, disease-specific survival, and progression-free survival of the patients. Overexpression of HIWI2 in HT1080 cells causes DNA damage by increasing intracellular ROS by inhibiting the expression of antioxidant genes (SOD1, SOD2, GPX1, GPX4, and CAT). Furthermore, an increase in H2AX phosphorylation was observed, which activates p53 that promotes p21 expression and caspase-3 activation, leading to G2/M phase cell cycle arrest and apoptosis. HIWI2 silencing, on the contrary, promotes cell growth, migration, and invasion by activating MMP2 and MMP9. These results are the first to show that HIWI2 acts as a tumor suppressor in fibrosarcoma by modulating the ROS/DNA damage/p53 pathway. [Display omitted] •HIWI2 is downregulated in fibrosarcoma cells compared to normal fibroblast cells.•Lower expression of HIWI2 is associated with poor patients' survival.•Overexpression of HIWI2 induces G2/M phase cell cycle arrest and apoptosis.•HIWI2 induces DNA damage mediated p53 activation by increasing intracellular ROS.•Silencing of HIWI2 enhances migration and invasion through MMP2/9 activation.