1. ¹Division of Oncology, The Children's Hospital of Philadelphia, 3615 Civic Center Boulevard, Philadelphia, PA 19104-4318, USA
2. ²Department of Pediatrics, University of Pennsylvania School of Medicine, 3620 Hamilton Walk, Philadelphia, PA 19104-6055, USA
3. ³Westat Biostatistics and Data Management Core, The Children's Hospital of Philadelphia, 3535 Market Street, Suite 1035, Philadelphia, PA 19104, USA

Correspondence: MD Hogarty, Division of Oncology, Children's Hospital of Philadelphia, 3615 Civic Center Boulevard, 9 North ARC (Suite 902C), Philadelphia, PA 19104-4318, USA. Tel: +215 590 3931; Fax: +215 590 3770; E-mail: hogartym@email.chop.edu

Received 5 May 2009; Revised 6 October 2009; Accepted 7 October 2009; Published online 6 November 2009.

Abstract

Bcl-2 family proteins regulate mitochondrial apoptosis downstream of diverse stressors. Cancer cells frequently deregulate Bcl-2 proteins leading to chemoresistance. We have optimized a platform for solid tumors in which Bcl-2 family resistance patterns are inferred. Functional mitochondria were isolated from neuroblastoma (NB) cell lines, exposed to distinct BH3-domain peptides, and assayed for cytochrome c release. Such BH3 profiles revealed three patterns of cytochrome c response. A subset had a dominant NoxaBH3 response implying Mcl1 dependence. These cells were more sensitive to small molecules that antagonize Mcl1 (AT-101) than those that antagonize Bcl-2, Bcl-xL and Bcl-w (ABT-737). A second subset had a dominant BikBH3 response, implying a Bcl-xL/-w dependence, and was exquisitely sensitive to ABT-737 (IC₅₀ <200 nM). Finally, most NB cell lines derived at relapse were relatively resistant to pro-death BH3 peptides and Bcl-2 antagonists. Our findings define heterogeneity for apoptosis resistance in NB, help triage emerging Bcl-2 antagonists for clinical use, and provide a platform for studies to characterize post-therapy resistance mechanisms for NB and other solid tumors.