Role of Sp1, p300 and CBP in PAX3-FOXO1A expression. ARMS cells were transfected with siSp1 (A), sip300 (B) and siCBP (C) for 72 hr, and whole cell lysates were analyzed by western blots.
ARTICLE ABSTRACT
Alveolar rhabdomyosarcoma (ARMS) is a devastating pediatric disease driven by expression of the oncogenic fusion gene PAX3-FOXO1A. In this study, we report overexpression of the nuclear receptor NR4A1 in rhabdomyosarcomas that is sufficient to drive high expression of PAX3-FOXO1A there. RNAi-mediated silencing of NR4A1 decreased expression of PAX3-FOXO1A and its downstream effector genes. Similarly, cell treatment with the NR4A1 small-molecule antagonists 1,1-bis(3-indolyl)-1-(p-hydroxy or p-carbomethoxyphenyl)methane (C-DIM) decreased PAX3-FOXO1A. Mechanistic investigations revealed a requirement for the NR4A1/Sp4 complex to bind GC-rich promoter regions to elevate transcription of the PAX3-FOXO1A gene. In parallel, NR4A1 also regulated expression of β1-integrin, which with PAX3-FOXO1A, contributed to tumor cell migration that was blocked by C-DIM/NR4A1 antagonists. Taken together, our results provide a preclinical rationale for the use of NR4A1 small-molecule antagonists to treat ARMS and other rhabdomyosarcomas driven by PAX3-FOXO1A. Cancer Res; 77(3); 732–41. ©2016 AACR.
