PAX3-FOXO1 Induces Cannabinoid Receptor 1 to Enhance Cell Invasion and Metastasis

Abstract

Alveolar rhabdomyosarcoma (ARMS) is a muscle-derived childhood tumor characterized by production of oncogenic PAX3/7-FOXO1 chimeric transcription factors. While downstream targets of the PAX3-FOXO1 oncoprotein in ARMS have been defined, the functional relevance of these targets is unclear. Here, we show that upregulation of the cannabinoid receptor 1 (Cnr1/Cb1) by PAX3-FOXO1 in mouse primary myoblasts and ARMS cell lines, contributes to PAX3-FOXO1 phenotypes, both in vivo and in vitro. In primary myoblasts, Cnr1 was dispensable for PAX3-FOXO1 to mediate cell proliferation, differentiation, or transformation; however, Cnr1 function was essential to increase the invasive capacity conferred by PAX3-FOXO1 overexpression in these cells. Genetic or pharmacologic abrogation of Cnr1 inhibited the enhanced basement membrane invasion induced by PAX3-FOXO1. Cnr1 loss by either route also dramatically reduced lung metastasis formation. Taken together, our findings strongly implicate Cnr1 as a novel tractable target to inhibit ARMS invasion and metastasis. Cancer Res; 71(24); 7471-80. Ó2011 AACR.

PAX3-FOXO1A Expression in Rhabdomyosarcoma Is Driven by the Targetable Nuclear Receptor NR4A1

“…Previous studies showed that PAX3-FOXO1A plays an important role in ARMS cell migration/invasion (37,38) and this is confirmed in Rh30 cell lines where transfection of siPAX3-FOXO1A decreased migration in a Boyden chamber assay (Fig. 5A).…”

Helicase CHD4 is an epigenetic coregulator of PAX3-FOXO1 in alveolar rhabdomyosarcoma

“…To examine whether the fusion protein indeed binds to target genes together with CHD4, we first validated selected PAX3-FOXO1 target genes with a known role in FP-RMS pathology, in 2 different FP-RMS cell lines (RH4 and RMS) 72 hours after induction of CHD4 depletion ( Figure 6A) (22,36,(44)(45)(46). We observed similar modulation of target gene levels by depleting CHD4 or PAX3-FOXO1.…”

“…Besides the PAX3-FOXO1 target genes already examined in our primary siRNA screen, we found that CHD4 inhibition had a strong impact on expression of anaplastic lymphoma kinase (ALK) and cannabinoid receptor 1 (CB1), both PAX3-FOXO1 target genes that have been implicated in the tumor biology of FP-RMS (44,45). In particular, expression of CB1 has been correlated with increased invasiveness of FP-RMS tumors (45). Therefore, our data suggest that CHD4 expression is required to coregulate a subset of PAX3-FOXO1 target genes that are necessary and sufficient to promote FP-RMS survival.…”

Comprehensive Genomic Analysis of Rhabdomyosarcoma Reveals a Landscape of Alterations Affecting a Common Genetic Axis in Fusion-Positive and Fusion-Negative Tumors

“…High-resolution SNP arrays corroborated 90% of high confidence SV when a copy number change was present (see Methods). Forty-eight genes were recurrently affected by SV, including genes previously implicated in RMS pathology ( MIR17HG, CNR1, CDKN2A ) (14-16), tyrosine kinase signaling ( ERBB4, RPTOR, FRS2, CACNA1A ) and muscle development ( NRG1, FOXP2 ) (Supplementary Table S4). Frequently (341/553, 61%), junction events occurred in areas of complex rearrangement or tandem duplications most often associated with regions of high copy number amplification.…”