Combining clinical cyclophosphamide with a novel Lactobacillus strain enhances apoptosis in cervical cancer cells

Background Cervical cancer remains a major global health burden among women. Despite the effectiveness of chemotherapeutic agents such as Cyclophosphamide (CTX), severe systemic toxicity and drug resistance limit their clinical potential. This study investigated the synergistic antitumor effects of CTX in combination with a novel Lactobacillus strain using a transwell co-culture system that enables paracrine interactions without direct bacterial contact. Methods HeLa cervical cancer cells were exposed to CTX, Lactobacillus , or their combination. Cell viability was evaluated using the MTT assay, while apoptosis was assessed through flow cytometry. Expression levels of Caspase-3, Caspase-9, Bax, Bcl-2 , and P53 were determined via quantitative real-time PCR. Results A pronounced synergistic cytotoxic effect was observed in the combined treatment group. The IC 50 of CTX decreased more than 400-fold, while maintaining strong antiproliferative activity (50.16 ± 2.31% cell viability). This fold change was calculated based on the ratio of IC 50 values of CTX in monotherapy versus CTX in combination with Lactobacillus casei Ab.343 SH in the Transwell co-culture system. Gene expression analysis revealed significant upregulation of Caspase-3, Caspase-9 , and Bax, with concurrent downregulation of Bcl-2, indicating activation of the intrinsic apoptotic pathway. The results suggest that Lactobacillus -derived metabolites enhance CTX-induced apoptosis via non-contact signaling mechanisms.. Conclusion Combining CTX with this probiotic strain substantially enhances apoptosis and cytotoxicity in cervical cancer cells while potentially lowering the required chemotherapeutic dose. This combination therapy highlights a promising and safe adjuvant strategy to improve clinical outcomes in cervical cancer treatment.