Abstract 3860: Drug resistance-mediating collagens (drmCOLs) are themselves druggable by an FDA/EMA-approved medicine to cause cancer cell arrest and apoptosis: Proof-of-conceptin vitro

Abstract Purpose of study: Tumor-generated collagen types I and III, identified two decades ago as factors of progression-free interval and survival in ovarian cancer (https://pubmed.ncbi.nlm.nih.gov/12468338/), mediate chemotherapeutic resistance, as do types VI and XI (https://pubmed.ncbi.nlm.nih.gov/34645978/, Table S1). All occur in pan-cancer gene signatures (https://pubmed.ncbi.nlm.nih.gov/27609069/). Collagens require Pro/Lys hydroxylation by 2-oxoacid utilizing dioxygenases (2OUDs) for native fold-dependent secretion and extracellular function; underhydroxylated collagens misfold and clog the endoplasmic reticulum. The HAG mechanism resolves 2OUD catalysis at orbital level, classifies all possible 2OUD inhibitors (https://pubmed.ncbi.nlm.nih.gov/6281585/), and is ‘seminal ‘ (https://pubmed.ncbi.nlm.nih.gov/7857312/) for development of collagen-suppressive drugs. We read the collagen-suppressive potential of the lifelong administered medicine deferiprone (DEF) off the HAG mechanism. Hypothesis: By blocking ligand reaction-driven ferryl formation in 2OUD catalysis, DEF at clinical range (10-150 µM) causes misfolded drmCOLs to trigger the unfolded protein response (UPR), effecting proliferative arrest and apoptosis preferentially of cancer cells. Methods: Genetically defined cell line models for high grade serous ovarian cancer (KURAMOCHI), uterine serous cancer (ARK1), normal matrix (MRC5); metabolic labeling; RNA-seq; flow cytometry. Results: In MRC5, DEF inhibited [3H]Pro/[3H]Lys hydroxylation, not incorporation. Cells expressed numerous COL mRNAs, e.g. 32 in ARK1 that suffice to generate 21 of 28 types of collagen; mRNAs for types I, VI, and XI/II predominated. Intracellular drmCOLs were confirmed by flow cytometry, using sequence-specific antibodies against COL1A1 (NBP1-77457AF700), COL3A1 (ab237239), COL6A1 (sc-377143), and COL11A2 (bs-2924R-A350). Within 48 hrs, DEF caused COL1A1/COL3A1/COL11A2 reactivity to increase up to 3-fold over controls; after 96 hrs, reactivity returned to control values in MRC5, remained elevated in KURAMOCHI, and rose further in ARK1, revealing cell-specific UPR set points. DEF at 48 hrs caused COL6A1 mRNA to decrease yet COL6A1 reactivity to increase in ARK1, evidencing the adaptive UPR ineffectively controls the accumulation of proteotoxic collagen. Activation of the ablative UPR, via enhanced DDIT3, XBP1, TRIB3, BAK1, PMAIP1, and HRK expression, coincided with a decline in cancer cell count by >80% within 96 hrs, an effect not observed in MRC5. Conclusions: HAG mechanism-defined inhibitors of drmCOL hydroxylation, pioneered by DEF, activate cytoreductive UPR effects in cancer cells preferentially. DEF use lacks adverse UPR or matrix effects, encouraging a pilot trial and 2OUD inhibitor development for oncological indication. Citation Format: Spencer M. Goering, Sukhwinder Singh, Bernadette M. Cracchiolo, Angela A. Sadev, Isabel W. Cracchiolo, Mainul Hoque, Axel-Rainer Hanauske, Yasmin Abedin, Hartmut Martin Hanauske-Abel. Drug resistance-mediating collagens (drmCOLs) are themselves druggable by an FDA/EMA-approved medicine to cause cancer cell arrest and apoptosis: Proof-of-conceptin vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3860.