The role of the gut microbiota in colorectal cancer (CRC) development has garnered attention, highlighting probiotics as potential adjuncts in CRC prevention and treatment. In recent years, probiotics and their derivatives have demonstrated mechanisms that may contribute to anticancer properties. This study investigates the cytotoxic effects of Bifidobacterium bifidum KCTC 3357, Lacticaseibacillus rhamnosus KCTC 5033, Limosilactobacillus reuteri VA 103, Bacillus galactosidilyticus VA 107, and Lactococcus taiwanensis VE101 on CT-26 mouse colon carcinoma cells using live cells, heat-killed cells (paraprobiotics), and cell-free supernatants (CFS, postbiotics) through an MTT assay. The results indicate that live bacterial strains, such as KCTC 3357, VA 103, and VA 107, promoted CT-26 cell viability, while heat-killed cells and CFS exhibited dose-dependent cytotoxicity. Inactivated forms of KCTC 3357 and VE 101, as well as CFS at 10 mg/mL concentration of KCTC 5033, VA 103, and VE 101, showed the strongest antiproliferative effects. These findings suggest that non-viable probiotic derivatives, such as paraprobiotics and postbiotics, offer promising therapeutic potential for CRC, providing a safer and more stable alternative to live probiotics. However, further research is required to explore their mechanisms of action, in vivo efficacy, and potential clinical applications.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    Cell culture
    Bacterial strain and growth condition
    Preparation of live, heat-killed, and cell-free supernatantforms of bacterial strains
    Cytotoxicity assessment using MTT assay
    Statistical analysis
RESULTS
    Cytotoxicity of live bacterial derivatives on CT-26 cells
    Effect of paraprobiotics on the viability of CT-26 cells
    Cytotoxicity of postbiotics (CFS) on CT-26 cells
DISCUSSION
ACKNOWLEDGEMENTS
REFERENCES

• Ched Nicole Turbela Aguilar(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Said Abdi Salad(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Tran Xuan Ngoc Huy(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Trang Thi Nguyen(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Seong Eun Cho(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Suk Kim(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea) Corresponding author
• Chaerim Park(V1bio Inc., B-1605, 167, Songpa-daero, Sonpa-gu, Seoul 05855, Korea)
• Hee Chol Kang(V1bio Inc., B-1605, 167, Songpa-daero, Sonpa-gu, Seoul 05855, Korea)
• Il-Hwan Kim(V1bio Inc., B-1605, 167, Songpa-daero, Sonpa-gu, Seoul 05855, Korea)