Poster Presentation Advances in Neuroblastoma Research Congress 2016

BMCC1, a tumor suppressor protein that facilitates DNA-damage response and apoptosis, is associated with favorable prognosis of neuroblastoma (#238)

Yasutoshi Tatsumi 1 , Islam Mohammad 1 , Miki Ohira 1 2 , Yohko Nakamura 1 , Akira Nakagawara 3
  1. Chiba Cancer Center Research Institute, Chiba, Japan
  2. Research Institute for Clinical Oncology, Saitama Cancer Center, Saitama, Japan
  3. Saga Medical Center KOSEIKAN, Saga, Japan

Background: BCH motif-containing molecule at the carboxyl terminal region 1 (BMCC1)/PRUNE2 is highly expressed in patients with favorable neuroblastoma. It encodes a 340-kDa protein with a conserved BNIP2 homology scaffold domain that may regulate signaling networks and multiple cellular functions, including apoptosis. Recent studies have suggested that BMCC1 acts as a tumor-suppressor because of its loss-of-function mutation or down-regulation in several types of tumors.

Methods: Quantitative RT-PCR was employed for the detection of BMCC1 mRNA expression in 102 primary neuroblastoma samples. To assess the functional role of BMCC1 in neuroblastoma, we performed the overexpression and/or knockdown of BMCC1 and E2F1 in neuroblastoma cell lines expressing BMCC1, such as SK-N-AS and NBL-S cells. To introduce DNA damage into neuroblastoma cell lines, cisplatin, adriamycin, or VP-16 was used.

Results: From a clinical perspective, multivariate analysis showed that the BMCC1 expression level was highly associated with survival after controlling for other well-known prognostic factors, such as MYCN, INSS stage, age, and TrkA expression level, indicating that the BMCC1 expression level acts as a reliable independent prognostic factor from these existing factors in the neuroblastoma patients. Our functional analysis demonstrated that BMCC1 was induced by DNA damage, one of the triggers of apoptosis, and it was transactivated by an ATM-E2F1-dependent mechanism. Accordingly, we investigated whether BMCC1 expression impacts intracellular signals involved in the regulation of apoptosis and found that BMCC1 promotes apoptosis at multiple steps in the AKT-mediated survival signal pathway via its BNIP2 homology domain. These steps include physical interaction with BCL2 and attenuation of the AKT-dependent inhibition of FOXO3a functions, such as the transcriptional induction of BIM and phosphorylation of ATM after DNA damage.

Conclusion: Our findings suggest that the downregulation of BMCC1 expression facilitates tumor development and genomic instability of neuroblastoma by abrogating apoptosis and ATM-mediated DNA damage repair.