Small molecule intervention of actin-binding protein profilin1 reduces tumor angiogenesis in renal cell carcinoma.

Angiogenesis plays a key role in the development and progression of renal cell carcinoma (RCC). Actin-binding protein profilin-1 (Pfn1) is overexpressed in clear cell RCC predominantly in tumor-associated vascular endothelial cells (ECs). We previously demonstrated that that EC-selective (over)expression of Pfn1 accelerates RCC progression, and conversely, genetic loss of EC-Pfn1 dramatically inhibits tumor angiogenesis impeding tumor initiation and/or progression in RCC, suggesting that Pfn1 could be an actionable therapeutic target in RCC. In this study, we demonstrate that 4,4'-((4-bromophenyl)methylene)bis(3,5-dimethyl-1H-pyrazole), a small molecule that we had previously identified as an inhibitor of Pfn1-actin interaction, directly binds to Pfn1 and attenuates tumor angiogenesis when directly administered into subcutaneous RCC tumors. Next, as a proof-of-concept, we demonstrate that Pfn1 inhibitor is amenable to microbubble encapsulation and release in the tumor microenvironment (TME) by ultrasound-mediated disruption of circulating microbubbles to achieve anti-angiogenic and anti-tumor benefit. Finally, we undertook a chemical optimization approach to design and synthesize 4,4'-((4-(trifluoromethyl)phenyl)methylene)bis(3,5-dimethyl-1H-pyrazole), a structural analog of our originally identified inhibitor, that exhibits improved anti-angiogenic efficacy. In summary, our findings suggest that tumor-localized release of Pfn1 inhibitor could be a potential therapeutic strategy in RCC.