Abstract 2146: Race-related differential immunoreactivity of enolase autoantibodies in patients with prostate cancer
Authors: Cheng Kai Wen , Osterman Carlos J. Diaz , Santiago Krystal , Reeves Michael , Lozano Diano , Ochoa Pedro , Duran Alfonso , Mirshahidi Saied , Hu Brian R. , Almaguel Frankis , Casiano Carlos A. 
Published: March 2024

INTRODUCTION AND OBJECTIVE: Enolase-1 (ENO1) and -2 (ENO2) are implicated in tumor metabolic and aggressive functions. Like prostate specific membrane antigen (PSMA), they localize to the tumor cell surface and are potential theranostics targets. ENO autoantibodies were reported by our group in prostate cancer (PCa) patients but their immunoreactivity to ENO1/2 isoforms was not defined. Differential ENO immunoreactivity in docetaxel-resistant (DR) PCa cells between African American (AA) and European American (EA) PCa patients was also reported. Our objective was to investigate the role of ENO isoforms in the race-related differential ENO immunoreactivity of PCa patients.

METHODS: PCa patient sera (41 AA, 68 EA) were obtained from Loma Linda University Biospecimen Laboratory. Western blotting (WB) analysis, using patient sera and monoclonal antibodies to ENO1 and ENO2, was done against lysates from docetaxel-sensitive (DS) and DR PCa cell lines and against recombinant (rec) ENO1 and ENO2 to assess ENO isoform expression and detect ENO autoantibodies. Scratch-wound assay was performed to evaluate AA and EA anti-ENO driven inhibition of DR PCa cell migration. Student’s T-test and Chi-squared analyses were performed with p&lt;0.05 deemed significant.

RESULTS: ENO1 expression was robust in all assessed DS and DR cell lines. ENO2 was detected in DS cells but was significantly reduced in DR cells. PSMA expression was lost in cells expressing ENO1 and neuroendocrine markers. Anti-ENO EA sera reacted in WB with the expected 50 kD band in both DS and DR PCa cells, but anti-ENO AA sera reacted preferentially with this band in DS cells. Strong immunoreactivity was noted against recENO1 in AA and EA sera (7% vs 28%, p&lt;0.01) and against recENO2 in AA and EA sera (24% vs 35%, p=0.23). EA, but not AA, ENO autoantibodies significantly inhibited DR cell migration, and their pre-absorption with recENO1 diminished this inhibitory effect.

CONCLUSIONS: Autoantibodies to ENO1 and ENO2 were identified in EA and AA PCa patient sera. Weaker ENO1 immunoreactivity was seen in sera from AA PCa patients, corresponding with weaker inhibition of DR PCa cell migration compared to EA patient sera. Unlike PSMA and ENO2, ENO1 expression was robust in neuroendocrine-like DR PCa cell lines. Future studies will correlate the presence of ENO autoantibodies with clinicopathologic parameters in a larger patient cohort. Defining mechanisms underlying the race-related differential ENO immunoreactivity may identify novel biological determinants of PCa health disparities and uncover the theranostic potential of tumor surface ENO1.

Citation Format: Kai Wen Cheng, Carlos J. Diaz Osterman, Krystal Santiago, Michael Reeves, Diano Lozano, Pedro Ochoa, Alfonso Duran, Saied Mirshahidi, Brian R. Hu, Frankis Almaguel, Carlos A. Casiano. Race-related differential immunoreactivity of enolase autoantibodies in patients with prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2146.