Abstract PS2-12-02: An Innovative Postbiotic Product Based on Sequential Fermentation of L.paracasei NPB01 and L.rhamnosus GG Demonstrates Antitumor Activity against Breast Cancer

Abstract Backgroud. Breast cancer (BC) is the most common and deadly cancer affecting women globally. While traditional treatments are used, factors limit their effectiveness, such as tumor heterogeneity, drug resistance, and non-targeted actions on cancer cells. Emerging evidence highlights the role of gut microbiota in modulating breast cancer risk, treatment response, and recurrence through various mechanisms, including the production of biologically active compounds and metabolites. These non-viable microbial products and metabolic byproducts from probiotic fermentation, known as postbiotics, exert beneficial effects on the host without the need for live microorganisms. Postbiotics derived from Lacticaseibacillus species represent a novel class of therapeutics with potential anti-cancer properties. In this study, we investigated the therapeutic effects of an innovative postbiotic product (iPB), developed through sequential fermentation of L.paracasei NPB01 and L.rhamnosus GG, in BC experimental models. Methods. The following cell lines were used to represent main BC subtypes: MCF7 cells (HR+/HER2-), MDA-MB-231 (triple negative breast cancer), SKBR3 (HER2+). MCF-10A (normal breast epithelial cells) and Caco-2 (enterocytes) cell lines were used as control. Cell viability was assessed by colony formation assay. Apoptosis was evaluated using Annexin V and 7-AAD staining and HLA class I surface expression was quantified by flow cytometry. Wound healing assay was applied to investigate the inhibitory effect of iPB on cell migration. Results. The iPB exposure resulted in >50% colony formation reduction in MCF7, MDA-MB-231 and SKBR3 cells starting from 0.5 mg/ml for 72 h. Furthermore, the iPB significantly increased early apoptotic cell rate in MCF7 cells starting at 0.5 mg/ml for 96 h. A similar trend was observed in MDA-MB231 and SKBR3 cells exposed to 5 mg/ml for 96 h iPB, as well as significant increase in late apoptotic cells detected by 7-AAD. On the contrary, control cells (MCF-10A, Caco-2) viability remained unaffected by the iPB exposure up to 5 mg/ml for 96 h. Evaluation of HLA class I surface expression revealed up to 30% increase in HLA class I expression in MCF7 cells induced by iPB starting at 0.5 mg/ml for 96 h, MDA-MB-231 cells at 1 mg/ml for 72 h, and SKBR3 cells at 5 mg/ml for 72 h, but there was no significant changes in MHC class I expression in control cells. Finally, the results of wound healing analysis revealed that iPB induced an up to 30% reduction in cell migration in all BC cell models, compared to the untreated cells where it induced a full wound closure. Conclusions. The iPB product reduces cell viability and cell migration in all main BC subtypes. These effects parallel with HLA class I surface expression increase in all BC cell phenotypes, potentially enhancing immunogenicity. These findings suggest that this iPB product may represent a promising novel agent in BC treatment and prevention. Citation Format: R. Berni Canani, C. Luongo, L. Pisapia, R. Di Santillo, A. Gaeta, C. Scocco, M. Michelini, V. Mauriello, A. Cadavere, C. Messuri, S. Chumsri, D. Mussallem. An Innovative Postbiotic Product Based on Sequential Fermentation of L.paracasei NPB01 and L.rhamnosus GG Demonstrates Antitumor Activity against Breast Cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-12-02.