Abstract 3825: Inhibitory effect of PID1 in medulloblastomas, gliomas and ATRT.

Abstract

Abstract The recently identified PID1 (Phosphotyrosine Interaction Domain containing 1) is a modulator of insulin signaling in adipocytes and muscle cells. Using a number of independent datasets we show that mean PID1 mRNA was lower in unfavorable medulloblastomas (subgroups 3 and 4) and in glioblastomas compared with favorable medulloblastomas (SHH and WNT subgroups) or normal brain, respectively. Higher PID1 mRNA correlated with longer progression-free survival and overall survival in medulloblastoma patients and with longer overall survival in glioma patients. Ectopic expression of PID1 in medulloblastoma, glioblastoma and ATRT (atypical teratoid rhabdoid tumor) cell lines inhibited colony formation by 68% ± 3.5 (p<0.0001 in total of 24 experiments in triplicates) compared with controls. PID1 effects on apoptosis and proliferation were demonstrated by increased sub-G0/G1 and annexinV staining, decreased S-phase. Additionally, PID1 induced mitochondrial depolarization in the medulloblastoma, glioblastoma, and ATRT cell lines. In keeping with PID1 having a PTB (phosphotyrosine binding) domain, endogenous PID1 co-immunoprecipitated with the low density lipoprotein receptor-related protein-1 (LRP1, which is a potential binding partner for PID1 via its C-terminal NPXY motif). However, PID1 with mutated PTB domain retained its inhibitory effects on colony formation, suggesting that other domains of PID1 mediated (or contributed to) PID1’s inhibitory effect. Analysis of PID1 domains comprising its N-terminal region (D1), C-terminal region (D3) and middle region (D2), each comprising approximately 1/3 of the protein, revealed that indeed, each 1/3 of PID1 inhibited colony formation at least as efficiently as full length PID1. Interestingly, although by itself D2 was more inhibitory than full length PID1, when it was combined with D3, which was also inhibitory by itself, we observed marked mitigation of the inhibitory effect of the combined D2+D5 fragment on colony formation, suggesting functional intramolecular interactions in PID1. These data suggest for the first time that PID1 has a tumor suppressor-like effect in brain tumors and shed light on the molecular mechanism of its inhibitory action. Citation Format: Anat Erdreich-Epstein, Xiuhai Ren, Hong Zhou, Richard Sposto, Lingyun Ji, Stefan Pfister, Marcel Kool, Shahab Asgharzadeh. Inhibitory effect of PID1 in medulloblastomas, gliomas and ATRT. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3825. doi:10.1158/1538-7445.AM2013-3825