Lactiplantibacillus plantarum Induces Apoptosis in Melanoma and Breast Cancer Cells

Abstract

Despite the notable advancements witnessed in the past decade in medical and health research domain, cancer remains a prominent global cause of mortality. Moreover, the conventional treatments employed to combat this disease have been found to considerably compromise the quality of life experienced by patients due to its severe side effects. Recent in vitro studies revealed encouraging findings on the potential beneficial effects of probiotics as adjuvants of anticancer therapy, and even as possible agents for the prevention and treatment of various types of malignancies. From this standpoint, the primary objective of this work was to investigate the anticancer properties of Lactiplantibacillus plantarum (LP) and elucidate its underlying mechanism of action. In order to investigate this matter, several doses of LP (ranging from 10⁵ to 10¹⁰ CFU/mL) were examined in relation to melanoma cancer cell lines (A375) and breast cancer cell line (MCF-7). The cell viability findings, which were substantiated by morphological investigations and annexin V/PI assay, indicated that LP exerted inhibitory effects on cellular activity and triggered apoptosis. Additionally, upon further investigation into its mechanism, it was observed through the apoptosis assay and Western blot analysis that the administration of LP resulted in an elevation of pro-apoptotic BAX protein levels and an upregulation of cleaved poly-ADP-ribose polymerase (PARP) protein expression. Conversely, the levels of anti-apoptotic Bcl-2 protein were found to decrease in the A375 and MCF-7 cell lines. These findings provide insight into the pro-apoptotic mechanism of action of LP in these specific cell lines.

Keywords: Lactiplantibacillus plantarum; apoptosis; breast cancer; cytotoxicity; melanoma.

Figure 1

Cell viability of HaCaT (A), A375 (B), and MCF-7 (C) cells following 48 h treatment with LP 10⁵–10¹⁰ CFU/mL and 5-FU (10 μΜ). The results are expressed as viability percentage in comparison with the control group, considered 100% (* p < 0.05 and *** p < 0.001). The data represent the mean values ± SD of three independent experiments performed in triplicate.

Figure 2

The impact of 48 h treatment with 10¹⁰ CFU/mL LP on HaCaT, A375, and MCF-7 cell lines; beta-actin—green staining and nuclei—blue staining. The yellow arrows indicate signs of apoptosis.

Figure 3

Identification of apoptosis in A375 cells after (LP 10¹⁰ CFU/mL) by the annexin V/PI double staining: viable cells (left bottom), early apoptotic cells (right bottom), late apoptotic cells (right top), and necrotic cells (left top).

Figure 4

Identification of apoptosis in MCF-7 cells after (LP 10¹⁰ CFU/mL) by the annexin V/PI double staining: viable cells (left bottom), early apoptotic cells (right bottom), late apoptotic cells (right top), and necrotic cells (left top).

Figure 5

Effect of 10¹⁰ CFU/mL LP on BAX (A) and Bcl-2 (B) protein levels in HaCaT, A375, and MCF-7 cell lines after 48 h treatment. The results were reported as mean values ± SD with p < 0.001 (***) when compared to their respective control. All experiments were performed in triplicate.

Figure 6

Determination of cleaved PARP protein expression in HaCaT, A375, and MCF-7 cells. The results were normalized against the beta-tubulin loading control and the control group. The statistical differences vs. control were determined using one-way ANOVA analysis followed by Tukey’s multiple comparisons post-test ( ** p < 0.01, and *** p < 0.001).