Abstract 520: Repurposing verteporfin: anti-metastatic properties associate with extracellular matrix modulation in osteosarcoma

Osteosarcoma (OS) is the most common primary bone cancer; 20% of OS patients present with metastasis at diagnosis, with more than 80% of those cases having spread to the lungs. Lack of treatments for metastatic disease leads to poor survival outcomes, making it imperative to find better therapies. Verteporfin (VP), a photosensitizer used for the treatment of age-related macular degeneration, targets the hippo signaling pathway via YAP1, while also inhibiting autophagy mediators through the formation of crosslinked oligomers, all without direct photoactivation. The purpose of this study was to assess VP’s effect on OS lung colonization, biomechanical properties, and extracellular matrix modulation independent of photoactivation. K7M2 OS cells or PBS were tail vein injected into BALB/c mice, and K7M2 injected mice were assigned to receive intraperitoneal 20 mg/kg VP or vehicle twice a week, starting at day 2 post-injection. Histological analysis of H&E and Masson’s trichrome stained sections was performed using QuPath on lung tissue collected on days 4, 8, 16, and 24 to assess metastatic burden and collagen content, respectively. Biomechanical analysis was performed with a custom indenter setup on lung samples with and without lesions to measure tissue stiffness. Insoluble protein contents were analyzed via mass spectrometry. Subsequently, in-vitro analysis was performed in K7M2 cells following treatment with 0.09 μM, 1.5 μM, 7.5 μM VP or vehicle for 24 hours, controlling for light. Fibronectin (FN) and tumor-related FN isoform (EIIIA, EIIIB, and IIICS) levels were assessed at the mRNA level via RT-qPCR on cell and lung samples, and FN protein expression was analyzed through immunofluorescence microscopy of cultured K7M2 cells. Histological analysis of day 24 lung samples highlighted a significant reduction in metastatic burden following VP treatment. Interestingly, stiffness was unchanged across day 4 and 24 in lung samples from vehicle-treated mice; however, VP treated samples showed a small yet significant increase. Collagen levels in metastases and stroma from vehicle and VP injected mice were unchanged throughout OS progression, though mass spectrometry identified FN enrichment in lung tissue from VP treated mice. FN mRNA levels were unchanged in cell lysates; conversely, lung samples highlighted reduced FN mRNA with metastasis, with VP restoring levels to that of normal lung. EIIIB FN was found to be decreased with metastasis, though largely variable with VP treatment. In cultured cells, FN protein expression increased parallel to VP concentration, with unchanged distribution. Results point towards VP effectively reducing OS metastasis to the lungs in parallel to increases in stiffness and FN expression. Further research on the role of the ECM, including FN and its isoforms, will further our understanding of the anti-metastatic properties of VP. Citation Format: Danny Carreira, Anita K. Luu, Carey E. Dougan, Shelly R. Peyton, Geoffrey A. Wood, Brenda L. Coomber, Alicia M. Viloria-Petit. Repurposing verteporfin: anti-metastatic properties associate with extracellular matrix modulation in osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 520.