Deficiency of TRDMT1 impairs exogenous RNA-based response and promotes retrotransposon activity during long-term culture of osteosarcoma cells.

TRDMT1 methyltransferase is postulated to be a novel target in anticancer therapy as TRDMT1-mediated RNA methylation is involved in DNA damage response (DDR) and TRDMT1 deficient cells are sensitive to PARP1 inhibitors. However, the effects of TRDMT1 gene knockout (KO) during cancer cell selection upon drug stimulation and the involvement of exogenous RNA were not addressed. In the present study, osteosarcoma (OS) cells lacking active TRDMT1 gene were subjected to short-term treatment of etoposide in the presence of exogenous RNA and long-term effects were analyzed after drug removal. Changes in cell proliferation and cell viability, genetic stability and DDR, telomere length and shelterin complex, retrotransposon activity and the levels of selected pro-inflammatory cytokines were considered. Long-term selection of TRDMT1 KO OS cells resulted in modified DDR, changes in telomere length and increased retrotransposon activity that was modulated by the addition of exogenous RNA. Thus, TRDMT1 gene KO may promote cellular and genetic heterogeneity that may modulate cancer cell responses to chemotherapeutic drugs.