Abstract 571: Angiopoietin-like 4 as a potential therapeutic target for clear cell renal carcinoma
Authors: Jin Zeng , De Umasankar , Wang Lei , Kleberg Jeremy , Zhang Weizhou , Kolb Ryan 
Published: April 2023

Abstract
Renal cell carcinoma (RCC) is the 7th most common type of cancer, with over 400,000 new cases each year and 170,000 deaths worldwide. RCCs are grouped into several histological subtypes, with clear cell renal cell carcinoma (ccRCC) being the most common and most aggressive type. The first line of therapy for ccRCC is tyrosine kinase inhibitors (TKIs) which target multiple kinases including the VEGF receptor. The treatment can be used alone or in combination with immune checkpoint inhibitors. However, most patients develop resistance to the TKIs within six months of treatment. Therefore, our aim is to develop novel single or combinatorial therapies and discover ways to overcome the resistance to TKIs. By analyzing TCGA and published datasets from GEO, we found that angiopoietin-like 4 (ANGPTL4) is significantly elevated in both the WT and TKI-resistant ccRCC tumors. ANGPTL4 has been shown to participate in angiogenesis in several other tumor models, and blocking ANGPTL4 with an antibody in vitro, reduces the angiogenic potential of 786-O and RCC4 human ccRCC cell lines, suggesting a pro-angiogenic effect of ANGPTL4 in ccRCC. Knockout of ANGPTL4 in Caki-1 xenograft tumor model significantly reduced tumor angiogenesis and increased vessel normalization, as evidenced by increased expression of VEGFR2 and adhesion molecules on endothelial cells. The increased normalization of blood vessels is an indication of the therapeutic potential of combing anti-ANGPTL4 therapy with immune checkpoint inhibitors. Furthermore, both knockout of ANGPTL4 in 786-O cells and treatment of 786-O tumor-bearing mice with an ANGPTL4 blocking antibody significantly reduced tumor growth. To illustrate the mechanism of ANGPTL4-induced angiogenesis, we performed live cell receptor capturing to find cANGPTL4 binding partners on the cell membrane of human endothelial cells. After the mass spectrometry analysis, several novel receptors were found, and the top candidate is endothelial cell surface chemotaxis receptor (ECSCR), which is highly expressed on endothelial and adipocytes. Previous studies have shown that ECSCR can potentiate angiogenic signaling, which is similar to our data showing that ANGPTL4 can synergistically increase FGF2-induced angiogenesis. Thus, ANGPTL4 may promote angiogenesis in ccRCC by potentiating other angiogenic signaling via interaction with ECSCR. To summarize, we demonstrated the pro-angiogenic potential of ANGPTL4 in ccRCC and its critical role in tumor development. Knockout or antibody-mediated inhibition of ANGPTL4 reduced tumor angiogenesis and growth and increased vessel normalization. This data supports the therapeutic potential of ANGPTL4 targeted treatment in ccRCC.
Citation Format: Zeng Jin, Umasankar De, Lei Wang, Jeremy Kleberg, Weizhou Zhang, Ryan Kolb. Angiopoietin-like 4 as a potential therapeutic target for clear cell renal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 571.