Poster Presentation Advances in Neuroblastoma Research Congress 2016

Inhibition of STAT3 with the generation 2.5 antisense oligonucleotide, AZD9150, decreases tumor-initiating potential of neuroblastoma cells and increases their chemosensitivity (#184)

Carol J Thiele 1 , Seiichi Odate 1 , Veronica Veschi 1 , Norris Lam 1 , Shuang Yan 1
  1. National Cancer Institute, Bethesda, MD, United States

In neuroblastoma (NB), cytokines activating STAT3 have been associated with poor patient outcome, chemoresistance and have been proposed to mediate survival of a rare population of NB tumor-initiating cells. Thus targeting STAT3 may be an important therapeutic strategy for high-risk NB. To determine the biologic consequences of STAT3 ablation, we evaluated pharmacogenomic inhibition of STAT3 using AZD9150, a 16-nucleotide antisense oligonucleotide targeting STAT3 that is now in adult Phase I/II clinical trials. Studies were performed in MYCN-wt (AS) and MYCN-amplified (NGP, IMR32) NB cell lines. AZD9150 treatment caused a 70% reduction in  STAT3 mRNA and protein levels causing decreases in STAT3 target genes, such as CyclinD1, D3, and MYC/MYCN. In vivo, AZD9150 treatment of established tumors had little effect on xenograft growth despite significant decreases in STAT3, P-STAT3 and target gene expression compared to ASO, a control anti-sense treatment. To assess whether inhibition of STAT3 altered the tumor-initiating potential of NB cells, varying numbers of tumor cells from the ASO or AZD9150 treated mice were re-implanted and secondary tumor growth assessed. At 2x105 and 2x104 ASO-treated NB cell inoculums, 100% of mice had tumors while at similar cell doses only 40 and 20%, respectively of AZD9150-treated mice had tumors. Limiting dilution analyses indicated that the precursor frequency for tumor-initiating cells in ASO-treated tumors was 1/5178 cells, but in the AZD9150-treated tumors only 1/187030 cells was competent to initiate tumor growth (P=1.93e-08). Since tumor-initiating or stem-like tumor cells are frequently more resistant to cytotoxic agents, we evaluated inhibition of STAT3 combined with cisplatin. In established NB tumor xenografts, STAT3 inhibition combined with cisplatin caused a 30% decrease in tumor size (P=0.0092) and increased the survival of AZD9150-treated tumor-bearing mice compared to ASO-treated mice (P=0.026). Our study supports the development of strategies targeting STAT3 in combination with conventional chemotherapy for patients with high-risk NB.