The HDAC3–SMARCA4–miR-27a axis promotes expression of the PAX3:FOXO1 fusion oncogene in rhabdomyosarcoma

Abstract

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood with an unmet clinical need for decades. A single oncogenic fusion gene is associated with treatment resistance and a 40 to 45% decrease in overall survival. We previously showed that expression of this PAX3:FOXO1 fusion oncogene in alveolar RMS (aRMS) mediates tolerance to chemo- and radiotherapy and that the class I–specific histone deacetylase (HDAC) inhibitor entinostat reduces PAX3:FOXO1 protein abundance. Here, we established the antitumor efficacy of entinostat with chemotherapy in various preclinical cell and mouse models and found that HDAC3 inhibition was the primary mechanism of entinostat-induced suppression of PAX3:FOXO1 abundance. HDAC3 inhibition by entinostat decreased the activity of the chromatin remodeling enzyme SMARCA4, which in turn de-repressed the microRNA miR-27a. This re-expression of miR-27a led to PAX3:FOXO1 mRNA destabilization and chemotherapy sensitization in aRMS cells in culture and in vivo. Furthermore, a phase I clinical trial (ADVL1513) has shown that entinostat is tolerable in children with relapsed or refractory solid tumors and is planned for phase I-b cohort expansion or phase II clinical trials. Together, these results implicate an HDAC3–SMARCA4–miR-27a–PAX3:FOXO1 circuit as a driver of chemoresistant aRMS and suggest that targeting this pathway with entinostat may be therapeutically effective in patients.

Sodium butyrate inhibits migration and induces AMPK‐mTOR pathway‐dependent autophagy and ROS‐mediated apoptosis via the miR‐139‐5p/Bmi‐1 axis in human bladder cancer cells

“…11 HDACs, which target lysine residues, are epigenetic determinants that are essential for transcriptional regulation via promoting chromatin condensation. 50,51 Tsung-Hua Hsieh and colleagues reported that acetylating RUNX3 enhanced the binding of the RUNX3/ p300 complex to the miR-125a-5p promoter and that silencing RUNX3 had the same biological effect as decreasing miR-125a-5p in human breast cancer cells. RUNX3 plays an important role in transcriptional regulation and the biological effect of miR-125a-5p.…”

Evaluation of entinostat alone and in combination with standard‐of‐care cytotoxic agents against rhabdomyosarcoma xenograft models

“…Our in vivo results can be compared with those of Abraham et al., who described testing for the entinostat and actinomycin D for a single mouse model of ARMS, and to those of Bharathy et al., who studied entinostat in combination with vincristine for PDX models of ARMS . Abraham et al.…”

“…Bharathy et al used entinostat administered daily for 21 days at doses of 4 or 25 mg/kg, producing daily exposure to high entinostat levels in contrast to the exposure profile observed in the clinical setting. 37 The impact of the addition of entinostat to the activity of vincristine for the PDX models tested was modest and did not result in statistically significant differences in tumor volume. We confirm that entinostat can cause the slowing of tumor growth for ARMS models, as In summary, we have evaluated entinostat at a dose and schedule of administration that designed to simulate entinostat exposure in patients, within the limitations imposed by mouse versus human differences in entinostat pharmacokinetics.…”

“…Bharathy et al. used entinostat administered daily for 21 days at doses of 4 or 25 mg/kg, producing daily exposure to high entinostat levels in contrast to the exposure profile observed in the clinical setting . The impact of the addition of entinostat to the activity of vincristine for the PDX models tested was modest and did not result in statistically significant differences in tumor volume.…”

“…33 When given on a weekly schedule, entinostat produces C max 25 and to those of Bharathy et al, who studied entinostat in combination with vincristine for PDX models of ARMS. 37 Abraham et al used a higher dose of entinostat (10 mg/kg with reduction to 5 mg/kg for toxicity) and a duration of treatment (9 days) than we used. Toxicity limited their ability to compare treatment arms beyond 7 days from treatment initiation.…”