Targeting Chaperone Dependence in Rhabdomyosarcoma
Amit J. Sabnis MD, Bivona LaboratoryUCSF Helen Diller Family Comprehensive Cancer Center
UCSF Benioff Children’s Hospital
Two Paradigms for Developing Cancer Therapies
Oncogene Dependence Non-Oncogene Dependence
Luo J et al., Cell 2009
HSP70 Chaperones are Cellular Buffers Against Proteotoxic Stress
Hypothesis: HSP70 inhibition will engage stress responses in rhabdomyosarcoma cells
and lead to cell death.
The HSP70 Inhibitor MAL3-101 Induces Apoptosis in Rhabdomyosarcoma (RMS) Cells
• Patient-derived rhabdomyosarcoma cell lines RMS13, Rh41, and Rh18 show micromolar sensitivity to MAL3-101.
• MAL3-101 induces apoptosis in sensitive cell lines.
RMS13 Cells: 24 Hr Treatment
The Integrated Stress Response (ISR) Links Chaperone Failure to Apoptosis
Hypothesis: Activation of the integrated stress response leads to cell death after MAL3-101 treatment.
Probing the Mechanism of Action of MAL3-101 with Derived Isogenic Resistant Cell Lines
Parental Line(MAL3-101 Sensitive)
Isogenic Resistant Lines(MAL3-101 Resistant)
2 Month MAL3-101
Dose Escalation
Treat with MAL3-101Measure Integrated Stress Response
RMS13 I.R. #1 - 4
Conclusions
• MAL3-101 is an HSP70 inhibitor that induces apoptosis in rhabdomyosarcoma cells.
• Apoptosis is a consequence of engaging the integrated stress response, and is CHOP dependent.
• Failure to upregulate CHOP after HSP70 inhibition is a biomarker of resistance to MAL3-101.
• Loss of CHOP causes partial resistance to MAL3-101.
Future Directions
• Test whether other stress sensors cooperate with the ISR in inducing apoptosis after HSP70 inhibition.
• Carry out an unbiased shRNA screen to comprehensively identify mechanisms underlying resistance in I.R. lines.
• Test MAL3-101 for activity in explant models of RMS as a prelude to clinical use.
Acknowledgements
Bivona LabTrever BivonaJonathan ShueAnin SayanaLuping LinCollin BlakelyEvangelos Pazarentzos
Support
Damon Runyon-Sohn Pediatric Cancer Fellow (A.J.S.)
St. Baldrick’s Foundation Fellow (A.J.S.)
HCIA Award (T.B.)
CollaboratorsJeff Brodsky (U. Pittsburgh)
Chris GuerrieroPeter Walter (UCSF)
Diego Acosta-AlvearCarmela Sidrauski
Jonathan Weissman (UCSF)Jason Gestwicki (UCSF)