Abstract 3975: PID1, a new growth-inhibitory gene, sensitizes brain tumor cell lines to chemotherapy

Abstract

Abstract BACKGROUND: Phosphotyrosine Interaction Domain containing protein-1 (PID1) is a gene discovered in 2006 in the context of obesity, which we recently showed inhibits growth of brain tumor cell lines and its mRNA level is directly correlated with survival of patients with gliomas and medulloblastomas (Erdreich-Epstein et al, Clin Cancer Res, In Press). PID1 mRNA was lower in more aggressive medulloblastomas and gliomas, and patients whose tumor had higher PID1 mRNA had longer survival. Moreover, overexpression of PID1 markedly decreased 2D colony formation in cell lines of medulloblastomas, GBM and atypical teratoid rhabdoid tumors (ATRT). The growth-inhibitory effect was due to both decreased proliferation and increased cell death. METHODS/RESULTS: COSMIC showed no mutations of PID1 in brain tumors, suggesting that PID1 was not a formal tumor suppressor gene. Therefore, we hypothesized that PID1 may sensitize brain tumor cells to therapy, and thus account for the longer survival in patients with higher PID1 mRNA. Indeed, while both cisplatin (10µg/ml) or transient PID1 overexpression increased apoptosis of glioma and medulloblastoma cell lines (indicated by increased AnnexinV and mitochondrial depolarization), combining cisplatin with PID1 caused a markedly higher apoptosis. Moreover, knockdown of PID1 by siRNA inhibited the cisplatin-induced mitochondrial membrane depolarization and apoptosis (AnnexinV), suggesting that PID1 may be required for cisplatin-induced apoptosis. Taken together, this suggests a sensitizing effect of PID1 to chemotherapy in both glioma and medulloblastoma cell lines. Intriguingly, PID1 mRNA and protein both increased in response to etoposide (5µg/ml), vincristine (50ng/ml) or cisplatin (5µg/ml) in a time- and dose-dependent manner in the brain tumor cell lines. This chemotherapy-induced increase in PID1 mRNA was blocked by inhibitors of NFKB, suggesting that regulation of PID1 may be an NFKB-dependent mechanism. Ongoing work seeks to decipher the mechanism of these effects and test them in vivo in mouse models. CONCLUSIONS: Our data suggest that PID1 acts to sensitize glioma and medulloblastoma cells to chemotherapy, possibly explaining the correlation between higher PID1 mRNA and survival in patients. Citation Format: Jingying Xu, Xiuhai Ren, Anthony Tran, Gregory M. Shackleford, Anat Erdreich-Epstein. PID1, a new growth-inhibitory gene, sensitizes brain tumor cell lines to chemotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3975. doi:10.1158/1538-7445.AM2014-3975