gms | German Medical Science

Objective: Survivin, belonging to the family of Inhibitor of Apoptosis proteins (IAP), is overexpressed in a broad variety of different tumor entities, even gliomas. Besides its role and function in apoptosis, Survivin is part of the chromosomal passenger complex which is involved in chromosome biorientation, spindle assembly checkpoint and cytokinesis. In previous studies we have shown that targeting Survivin in U87-MG glioblastoma cells by shRNA mediated knockdown led to defective mitosis and resulted in a transient p53-dependent G1 arrest. In this study we sought to elucidate the interconnection between Survivin’s role in mitosis and p53 activation and subsequent cell cycle arrest after Survivin-RNAi.

Method: U87-MG glioma cells were transduced using retroviral short-hairpin RNAs targeting Survivin or Luciferase, respectively. Subsequently, cells were subjected to Western blot-, flow cytometry- and immunofluorescence analysis.

Results: Confocal laser scanning microscopy revealed DNA lesions in U87-MG cells transduced with shRNA targeting Survivin but not in control cells, as indicated by yH2AX and activated DNA damage kinase ATM foci. Furthermore, foci for yH2AX and activated ATM (S1981) were colocalized and occurred only in polyploid Survivin-depleted U87-MG cells. A combined DNA-antibody FACS analysis revealed a correlation between increased yH2AX expression and increasing DNA content in Survivin-depleted U87-MG wild type and p53-deficient cells suggesting that DNA damage occurs as a consequence of mitotic errors e.g. false kinetochor-microtuble (merotelic) attachments. U87-MG and U87-MGshp53 cells with stable knockdown of Survivin showed after a cultivation period of 3 weeks a dramatic decrease in clonogenic survival irrespective of p53 status when compared to shLuciferase-transduced cells.

Conclusions: Our results suggest that interference with Survivin’s chromosomal passenger function leads to glioma cell death irrespective of p53 status. Therefore, inhibiting Survivin by RNAi or small molecule suppressants might be a promising strategy for targeting primary as well as secondary glioblastoma.