P12.54.A MOLECULAR MECHANISMS OF ANEUPLOIDY AND GLIOBLASTOMA AGGRESSIVENESS INDUCED BY DIAPH3 LOSS

Abstract BACKGROUND Diaphanous-related formin 3 (Diaph3) belongs to the formin family of dimeric multidomain proteins that are master regulators of actin and microtubule dynamics. It plays a role in the cytoskeleton remodeling, more specifically in both cytokinesis and karyokinesis. In the mouse brain, loss of Diaph3 induced aneuploidy followed by massive apoptosis in neural stem cell, leading to microcephaly. Given the potential role of aneuploidy in cancer development, we are interested to unravel whether Diaph3 depletion during gliomagenesis could aggravate glioblastoma (GBM) aggressiveness. MATERIAL AND METHODS To analyze whether Diaph3 is a potential therapeutic target in human GBM, we used siRNA mediated depletion of Diaph3 in a panel of GBM cell lines (U251 and U87). RESULTS Our results showed that siRNA-mediated depletion of Diaph3 in p53 mutated GBM cells (U251 cells) disrupted microtubules and caused mitotic defects such as multipolar mitosis. The observed phenotype is typically an indication of aneuploidy, leading us to investigate it as our next step. Karyotyping showed an increase in aneuploidy in Diaph3-depleted U251 cells. Since it has been shown that numerical abnormalities in chromosomes segregation could trigger DNA damage response (DDR), we hypothesize that the loss of Diaph3 induces increased activity of the DDR pathway and we aimed to decipher their underlying molecular mechanism. CONCLUSION We believe that this study may provide insights into the mechanisms by which Diaph3 prevents aneuploidy in glioblastoma cells but also, more generally, into the role of aneuploidy in gliomagenesis. Potentially uncovering new therapeutic targets and advancing our understanding of tumor progression and genome stability in gliomas.