Abstract PO2-13-06: Analysis of Antibody Response to SV-BR-1-GM Therapeutic Vaccine in Breast Cancer Patients Using Human Protein Microarrays: Potential Correlations with Therapy Response
Authors: Lopez-Lago Miguel , Chang Mingjin , Priore Giuseppe Del , Bhardwaj Vikas , Cournoo Patience , Ramos Pedro , Hulett Tyler , Wiseman Charles , Williams William 
Published: May 2024

Abstract
Background: Therapeutic cancer vaccines aim to stimulate the immune system by utilizing tumor antigens to trigger an antitumor response. In our clinical trials, we have focused on evaluating the efficacy of the breast cancer cell line secreting GM-CSF, SV-BR-1-GM as a therapeutic vaccine, and we have observed encouraging clinical outcomes. The SV-BR-1-GM regimen has been used alone (“monotherapy”, ClinicalTrials.gov NCT03066947 – study completed) and in combination with checkpoint inhibitors (“combination”, ClinicalTrials.gov NCT03328026 – study ongoing). To further improve the therapeutic efficacy of this vaccine we have initiated a study to characterize patient’s immune response to this treatment. It has been demonstrated that cancer vaccines can generate both humoral and cellular immune responses. However, predicting immune responses to cancer vaccines, especially when whole cells are employed as immunogens, presents significant challenges. We present here a preliminary analysis of the antibody response to SV-BR-1-GM in breast cancer patients using antigen arrays. Methods: Large-scale protein arrays are versatile and sensitive platforms for antibody specificity evaluation. The HuProt™ Human Proteome Microarray (CDI Laboratories, Inc., Baltimore, Maryland, United States) provides the largest number of unique, full-length, individually purified human proteins on a single microscope slide. This allows thousands of interactions to be profiled in a high-throughput manner. We utilized here an unbiased human protein microarray platform encompassing &gt;21,000 proteins and isoforms from ~19,000 unique genes to identify IgG and IgM responses against self-antigens elicited by treatment. Serum samples from SV-BR-GM-treated patients were analyzed, comparing pre- and post-treatment. The human serum samples were probed at 1:1000 dilution. After sample processing and data collection the raw signal intensities on all arrays were quantile normalized using CDI software. Heatmaps were generated using MetaboAnalyst 5.0, which utilizes the R pheatmap package (version 0.7.7). For paired analysis, fold changes (FCs) were calculated by determining the ratio between paired pre- and post-treatment samples, resulting in one FC per pair. The means of these FCs (pair means) were then computed. ANOVA tests were performed using the RStatix R package, which automatically determines the appropriate Type I, II, or III errors for the analysis. Results: By using this approach, we were able to evaluate a broader range of antigens compared to previous investigations. Using a variety of statistical approaches, potential correlations with patient survival on SV-BR-1-GM were evaluated. Antibody responses to galectin antigens demonstrated the most consistent relationships with survival. Further confirmation with additional patients and prospective analysis are needed to fully understand relationships with clinical benefit and survival.
Citation Format: Miguel Lopez-Lago, Mingjin Chang, Giuseppe Del Priore, Vikas Bhardwaj, Patience Cournoo, Pedro Ramos, Tyler Hulett, Charles Wiseman, William Williams. Analysis of Antibody Response to SV-BR-1-GM Therapeutic Vaccine in Breast Cancer Patients Using Human Protein Microarrays: Potential Correlations with Therapy Response [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-13-06.