RUNX2 inhibition disrupts a PAX3::FOXO1-RUNX2 feed-forward loop and dismantles oncogenic gene programs in...

Area of Science:

• Oncology
• Molecular Biology
• Pediatric Cancer Research

Background:

• Fusion-positive rhabdomyosarcoma (FP-RMS) is an aggressive pediatric cancer with poor survival rates, particularly for metastatic disease.
• The PAX3::FOXO1 fusion gene drives FP-RMS but is not currently a targetable therapeutic protein.
• There is a critical need for novel therapeutic targets in FP-RMS.

Purpose of the Study:

• To identify druggable targets in fusion-positive rhabdomyosarcoma.
• To investigate the role of RUNX2 as a potential therapeutic target in FP-RMS.

Main Methods:

• Performed mRNA sequencing on RMS patient tumors and FP-RMS cell lines (Rh30, Rh4).
• Conducted in vitro loss-of-function studies using RNAi and the small molecule CADD522 to inhibit RUNX2.
• Performed in vivo studies using conditional and pharmacologic inhibition of RUNX2 in a xenograft model.

Main Results:

• RUNX2 was identified as the top druggable dependency in FP-RMS.
• RUNX2 suppression inhibited FP-RMS cell growth, induced myogenic differentiation and apoptosis, and mimicked PAX3::FOXO1 suppression.
• RUNX2 inhibition significantly reduced tumor growth in vivo.
• A feed-forward loop between PAX3::FOXO1 and RUNX2 was elucidated, where PAX3::FOXO1 upregulates RUNX2, and RUNX2 supports PAX3::FOXO1 expression.

Conclusions:

• RUNX2 is a critical therapeutic target in fusion-positive rhabdomyosarcoma.
• Targeting RUNX2 presents a promising new strategy for treating this aggressive pediatric cancer.
• Understanding the PAX3::FOXO1-RUNX2 regulatory loop provides mechanistic insight into FP-RMS pathogenesis.