Abstract. Breast cancer is one of the most common malignancies affecting women worldwide. The induction of apoptosis is an important therapeutic strategy for controlling tumour progression. Probiotic bacteria, particularly Lactiplantibacillus plantarum, have attracted considerable attention because of their potential anticancer properties. This study aimed to investigate the effects of live and heat-killed Lactiplantibacillus plantarum bacteria and their extracellular compounds on the expression of apoptosis-related genes in MCF-7 breast cancer cells. The MCF-7 cells were treated with live bacterial cells (LB), heat-killed bacterial cells (HKB), and extracellular compounds of L. plantarum. Total RNA was extracted, reverse transcribed into cDNA, and subjected to quantitative real-time PCR (qRT-PCR). The gene expression of caspase 9, Bax, Bcl-2 and caspase 3 in MCF-7 cells treated with Lactobacillus plantarum (live, heat-killed, and extracellular compounds) was determined by qRT-PCR using SYBR Green Master Mix, and GADPH expression was used as a housekeeping gene. Treatment with L.