Abstract B001: Calcitonin receptor-like receptor agonists induce p44/42 MAPK phosphorylation in VEGF-A-stimulated human blood endothelial cells after bevacizumab treatment
Authors: Morfitt Matthew A. , Greenman John , Maraveyas Anthony , Nikitenko Leonid L. 
Published: August 2023

Abstract
Introduction. Clear cell renal cell carcinoma (ccRCC) is a highly vascularized and clinically aggressive cancer. In the UK, there are around 9000 diagnoses and 3000 deaths annually. Targeted therapies that inhibit angiogenic regulators, such as bevacizumab (monoclonal antibody which inhibits vascular endothelial growth factor A, VEGF-A), have limited efficacy due to drug resistance. Expression of calcitonin receptor-like receptor (CLR) is upregulated in ccRCC and correlates with disease outcome. The expression of adrenomedullin (AM), peptide agonist of CLR and angiogenic factor, is upregulated in ccRCC. We hypothesized that the CLR signaling axis acts as an alternative pathway that enables resistance to drugs targeting the VEGF-A pathway in ccRCC. In the present study, we aimed to determine whether this signaling axis remains active in VEGF-A-stimulated and bevacizumab-treated human endothelial cells. Methods. Primary human dermal blood vessel endothelial cells (HDBEC; PromoCell) were characterized by immunofluorescence utilizing pan-endothelial (cluster of differentiation 31 and 144, CD31 and CD144, and von Willebrand factor, vWF) and lymphatic-specific (lymphatic vessel endothelial hyaluronan receptor 1, LYVE-1, and prospero homeobox 1, PROX1) markers and confocal microscopy. The activities of CLR agonists (AM; intermedin, IMD; calcitonin gene-related peptide, CGRP; 10−12 - 10−6 M at 10 min) and VEGF-A (50 ng/ml over 30-minute time course) were measured by analyzing phosphorylation of p44/42 mitogen-activated protein kinases (MAPK) using immunoblotting. HDBEC were pre-treated with bevacizumab or human IgG1 at 250 ng/ml and then stimulated with individual CLR agonists at 10−6 M for 10 minutes. Experiments were repeated at least three times. Data were analyzed using Shapiro-Wilk normality, unpaired statistics and appropriate multiple comparisons tests utilizing GraphPad Prism and p&lt;0.05 interpreted as significant. Results. HDBEC were a pure population. AM, IMD and CGRP induced p44/42 MAPK phosphorylation at 10−6 M (p&lt;0.05). For all three CLR agonists and VEGF-A, p44/42 MAPK phosphorylation peaked after 10 minutes of incubation (p&lt;0.05). Bevacizumab treatment at 250 ng/ml was sufficient to inhibit VEGF-A-induced p44/42 MAPK phosphorylation (p&lt;0.05). AM, IMD and CGRP were all able to induce phosphorylation of p44/42 MAPK after bevacizumab treatment (p&lt;0.01). Conclusions. The findings that CLR agonists induce p44/42 MAPK phosphorylation in VEGF-A-stimulated HDBEC after bevacizumab treatment support our hypothesis. This work provides a foundation for investigating the role of the CLR signaling axis in mechanisms of ccRCC resistance to drugs targeting the VEGF-A pathway.
Citation Format: Matthew A. Morfitt, John Greenman, Anthony Maraveyas, Leonid L. Nikitenko. Calcitonin receptor-like receptor agonists induce p44/42 MAPK phosphorylation in VEGF-A-stimulated human blood endothelial cells after bevacizumab treatment [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr B001.