Abstract A063: Targeting calreticulin acetylation to enhance tumor immunogenicity in prostate cancer

Abstract Prostate cancer remains the most commonly diagnosed malignancy in men in the United States and the second leading cause of cancer-related mortality. Identifying new molecular mechanisms that influence tumor–immune interactions is essential for improving therapeutic outcomes. Calreticulin (CRT), an endoplasmic reticulum (ER) chaperone, can translocate to the cell surface where it functions as a damage-associated molecular pattern (DAMP) during immunogenic cell death (ICD), serving as an “eat-me” signal that links the stressed tumor cell to innate immune recognition and subsequent adaptive T-cell activation. Although CRT expression in prostate epithelial cells is known to be androgen-regulated, the mechanism governing its surface localization is poorly understood. Post-translationally modified forms of CRT have been detected at the cell surface, yet its potential acetylation-dependent trafficking has not been examined, despite proteome-wide studies identifying numerous acetylated proteins in prostate cancer. Here, we investigated the role of CRT acetylation in its surface translocation in prostate cancer models. Using 7,8-diacetoxy-4-methylcoumarin (DAMC) as an exogenous acetyl donor, we evaluated surface and intracellular expression of wild-type and lysine-mutant (K206R/K207R/K209R) GFP-tagged CRT in LNCaP cells for later comparison with primary prostate epithelial cells. Cells were treated with DAMC (100 µM) in combination with trichostatin A (50 nM) and thapsigargin (100 nM) for 24 h. Immunofluorescence analysis demonstrated increased surface CRT in treated cells compared with controls, with a positive correlation between surface CRT and lysine acetylation signals. Surface protein isolation and immunoblotting confirmed CRT at the plasma membrane, although acetyl-lysine signal was diminished, suggesting that acetylation facilitates CRT trafficking but may be reversed or transferred upon membrane localization. Experiments with mutant CRT isoforms and analysis assessing whether DAMC-induced CRT acetylation is accompanied by other hallmarks of ICD, including extracellular ATP and HMGB1 release are ongoing to determine whether acetylation enhances the full immunogenic signature of dying prostate cancer cells. These findings support a model in which CRT acetylation enhances its surface exposure and immunogenic function, providing a novel mechanism by which post-translational modification can modulate tumor immunogenicity. Elucidating this pathway may reveal new strategies to exploit the prostate tumor microenvironment, enhance immune recognition of prostate cancer cells, and inform combination approaches with immunotherapy or radiation. Citation Format: Courtney Thomas, Janiyah Vogle, Kandace Rankin, Emmanuel Frimpong, Kayla Glover. Targeting calreticulin acetylation to enhance tumor immunogenicity in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr A063.