Therapeutic targeting of the MYC signal by inhibition of histone chaperone FACT in neuroblastoma — ASN Events
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  3. Therapeutic targeting of the MYC signal by inhibition of histone chaperone FACT in neuroblastoma

Therapeutic targeting of the MYC signal by inhibition of histone chaperone FACT in neuroblastoma (#154)

Joanna Tsang 1 , Daniel R Carter 1 2 , Jayne Murray 1 , Belamy B Cheung 1 2 , Laura Gamble 1 , Selina Sutton 1 , Jessica Koach 1 , Heyam Kalla 1 , Sarah Syed 1 , Andrew J Gifford 1 3 , Patrick Y Kim 1 , Tao Liu 1 2 , Katerina V Gurova 4 5 , Andrei V Gudkov 4 5 , Murray D Norris 1 , Michelle Haber 1 , Glenn M Marshall 1 6
  1. Children’s Cancer Institute Australia, Lowy Cancer Research Centre, University of New South Wales, Randwick, NSW, Australia
  2. School of Women's & Children's Health, University of New South Wales, Randwick, NSW, Australia
  3. Department of Anatomical Pathology (SEALS), Prince of Wales Hospital, Randwick, NSW, Australia
  4. Buffalo BioLabs Inc., , Buffalo, NY, USA
  5. Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY, USA
  6. Kids Cancer Centre, Sydney Children’s Hospital, Randwick, NSW, Australia

Amplification of the MYCN oncogene occurs in approximately 25% of paediatric neuroblastoma patients and predicts poor prognosis and treatment resistance. As a transcription factor, development of targeted therapies for MYCN has proven difficult. We identified the histone chaperone, Facilitates Chromatin Transcription (FACT), as a mediator of the MYC signal and novel therapeutic target in the disease. FACT consists of two subunits, Suppressor of Ty 16 and Structure Specific Recognition Protein 1 (SPT16, SSRP1) which are highly dependent on each other for regulation of expression and function. Moreover, a FACT-inhibitor CBL0137 has shown promising pre-clinical evidence as an anti-cancer agent. We present here molecular mechanisms by which FACT inhibition is able to interupt the MYCN signal in neuroblastoma.

Both FACT subunits are significantly associated with poor overall and event-free survival in two cohorts of primary neuroblastoma patients. siRNA knock down of MYCN significantly diminished SPT16 and SSRP1 mRNA and protein expression in MYCN-amplified neuroblastoma cell lines. Chromatin immunoprecipitation assays demonstrate significant enrichment of MYCN at the E-box motif of the SPT16 core promoter. Conversely siRNA knockdown of SSRP1 and SPT16 led to a decrease in MYCN mRNA and protein expression whereas, overexpression of SSRP1 and/or SPT16 led to an increase in MYCN protein levels. In addition, cycloheximide assays showed SSRP1 or SPT16 knockdown markedly reduced MYCN protein half-life suggesting FACT regulates MYCN protein levels by two discrete mechanisms, at the transcriptional and post-translational level. Altogether this describes a FACT/MYCN positive feedback loop.

In vitro, both FACT knockdown or treatment with CBL0137 are able to decrease MYCN protein expression, cell viability and colony formation in MYCN over expressing cells. This is recapitulated in vivo, showing a strong therapeutic benefit against MYCN-driven neuroblastoma. Together the results suggest a novel mechanism for new treatment strategies in MYCN-driven neuroblastoma.