Inhibitory Effects of Probiotic Lactobacillus on the Growth of Human Colonic Carcinoma Cell Line HT-29

Abstract

This study was conducted to investigate the inhibitory effect of Lactobacillus cells and supernatants on the growth of the human colon cancer cell line HT-29. Our study results indicated that the PM153 strain exhibits the best adhesion ability and the highest survival in the gastrointestinal tract simulation experiment. Furthermore, after an 8-h co-culture of PM153 and HT-29 cells, the PM153 strain can induce the secretion of nitric oxide from the HT-29 cells. In addition, after the co-culture of the BCRC17010 strain (10⁸ cfu/mL) and HT-29 cells, the Bax/Bcl-2 ratio in the HT-29 cells was 1.19, which showed a significant difference from the other control and LAB groups (p < 0.05), which therefore led to the inference that the BCRC17010 strain exerts a pro-apoptotic effect on the HT-29 cells. Upon co-culture with HT-29 cells for 4, 8 and 12 h, the BCRC14625 strain (10⁸ cfu/mL) demonstrated a significant increase in lactate dehydrogenase (LDH) activity (p < 0.05), causing harm to the HT-29 cell membrane; further, after an 8-h co-culture with the HT-29 cells, it induced the secretion of nitric oxide (NO) from the HT-29 cells. Some lactic acid bacteria (LAB) strains have ability to inhibit the growth of the colorectal cancer cell line HT-29 Bax/Bcl-2 pathway or NO production. In summary, we demonstrated that the BCRC17010 strain, good abilities of adhesion and increased LDH release, was the best probiotic potential for inhibition of HT-29 growth amongst the seven LAB strains tested in vitro.

Keywords: Bax/Bcl-2 ratio; HT-29 cells; Lactobacillus; interleukin-8; lactate dehydrogenase.

Figure 1

Survival of lactic acid bacteria in simulated gastric juice (A) pH 2.0 (B) pH 3.0.

Figure 1

Survival of lactic acid bacteria in simulated gastric juice (A) pH 2.0 (B) pH 3.0.

Figure 2

(A) Measurement of cytotoxicity on HT-29 cell line by lactic acid bacteria supernatants after 24 h incubation; (B) Measurement of cytotoxicity (%) on HT-29 cell line by lactic acid bacteria strains after 4, 8, 12 h incubation. cytotoxicity (%) = [(Experimental OD₄₉₀ − Spontaneous negative control OD₄₉₀)/Maximum LDH release positive control OD₄₉₀] × 100.

Figure 3

Effect of BCRC14625 supernatant on the level of Bax/Bcl-2 in the HT-29 cell line. The control means untreated cells. (A) Protein products of Bax and Bcl-2 extracted from the HT-29 cell line; (B) Bars represent the protein expression ratio of Bax/Bcl-2 in the HT-29 cell line.

Figure 4

Four lactic acid bacteria (10⁹ cfu/mL) in HT-29 for 8 h after on the level of Bax/Bcl-2 in HT-29 cell line. The control means untreated cells. ^a–d Values with different symbols are significantly different at the level of p < 0.05 by One-way ANOVA.

Figure 5

NO production was used by (A) lactic acid bacteria supernatant on HT-29 cell line after 24 h or four lactic acid bacteria strains on HT-29 cell line after (B) 4 h (C) 8 h incubation. The control means untreated cells. Data are expressed as means ± SD, ^a–e Values with different symbols are significantly different in the same LAB strain group at the level of p < 0.05 by One-way ANOVA.

Figure 5

NO production was used by (A) lactic acid bacteria supernatant on HT-29 cell line after 24 h or four lactic acid bacteria strains on HT-29 cell line after (B) 4 h (C) 8 h incubation. The control means untreated cells. Data are expressed as means ± SD, ^a–e Values with different symbols are significantly different in the same LAB strain group at the level of p < 0.05 by One-way ANOVA.