Abstract 137: Type XII collagen is elevated in serum from patients with solid tumors: A non-invasive biomarker of activated fibroblasts

Background: The tumor microenvironment (TME) and extracellular matrix (ECM) are critical to tumor progression and treatment outcomes. Collagens, the main ECM components, influence cell signaling, migration, and tumor invasion. Type XII collagen is essential for type I collagen assembly and stabilizes the ECM. It is predominantly produced by cancer-associated fibroblasts (CAFs), and its upregulation is linked to poor survival in several cancers. This study developed and validated an ELISA to measure circulating type XII collagen as a potential cancer biomarker. Methods: A monoclonal antibody targeting the C-terminal of type XII collagen was used to develop a competitive ELISA (nordicPRO-C12) for detecting type XII collagen fragments in serum from cancer patients (n=230) and healthy controls (n=33). Type XII collagen expression was also assessed by Western blot in supernatants and lysates from CAFs and normal fibroblasts (NFs) derived from pancreas, lung, colon, and breast tissues, under both TGFβ-stimulated and non-stimulated conditions. Results: The nordicPRO-C12 assay showed high specificity and robustness, detecting significantly elevated serum PRO-C12 levels in patients with prostate, breast, melanoma, lung, gastric, pancreatic, head and neck, and colorectal cancers (p < 0.005 for all). The assay effectively distinguished cancer patients from healthy controls, with high AUROCs for breast (0.95), prostate (0.92), lung (0.92), gastric (0.88), melanoma (0.83), pancreatic (0.80), and head and neck cancers (0.76). These findings were supported by COL12A1 expression data from TCGA and GTEx. Western blot analysis confirmed increased type XII collagen expression in both CAFs and NFs after TGFβ stimulation, highlighting TGFβ's role in ECM remodeling and type XII collagen regulation in cancer and normal microenvironments. Conclusion: This study highlights PRO-C12 as a promising non-invasive biomarker for cancer detection and monitoring. The ability to quantify type XII collagen fragments provides insights into cancer progression. While these results are encouraging, further studies are required to validate PRO-C12's diagnostic and prognostic potential across cancers, potentially expanding its application to clinical practice. Citation Format: Marina Crespo-Bravo, Annika Hettich, Jeppe Thorlacius-Ussing, Thomas R. Cox, Morten A. Karsdal, Nicholas Willumsen. Type XII collagen is elevated in serum from patients with solid tumors: A non-invasive biomarker of activated fibroblasts [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 137.