The effects of probiotics and Actinomyces naeslundii on oral carcinogenesis

Abstract

Oral cancer is one of the subclassification of head and neck cancer, which is one of the most prevalent cancers globally with high incidence and mortality rate. 90% of oral cancer constitutes of oral squamous cell carcinoma (OSCC). The prognosis status of the patients after treatment is determined by the relapse of the secondary oral tumour. The relapse of the secondary oral tumour leads to poor prognosis status of patients, hence reducing its five-year survival rate. Recently, probiotics have been heavily studied due to its health benefits and its contribution to cancer prevention. This study aimed to identify the anti-cancer properties of probiotics in oral carcinogenesis. A systematic review and meta-analysis were conducted to identify the list of probiotics that have a prominent effect on oral carcinogenesis. The identified probiotics were Acetobacter syzygii, Lactobacillus plantarum, Lactobacillus salivarius REN and AJ2. These probiotics elicited several effects against oral cancer, including anti-proliferative effects, modulation of protein expression, and apoptosis. The meta-analysis of the present study showed that L. salivarius REN is associated with a lower risk of oral carcinogenesis by 95%, with (OR=0.05, P<0.05). Thus, the ability of L. salivarius REN as an inhibitory agent for oral carcinogenesis is identified. Actinomyces naeslundii is one of the early oral colonisers that is associated with oral biofilm development. However, the previous study has discovered the presence of A. naeslundii in polymicrobial biofilms was able to reduce the biofilm biomass and activity of the oral pathogens. Hence, this study also aimed to identify the protein similarities between L. salivarius REN and A. naeslundii using in silico analysis. From the analysis, elongation factor Tu (EF-Tu) protein was identified with percent similarities of 79.5% in the present study. EF-Tu is a translation factor protein that is responsible for the modulation of the immune response. In addition, C. albicans is an opportunistic yeast that frequently isolated from the oral cavity. The previous study has shown that C. albicans is associated with oral carcinogenesis. The present study aims to determine the potential of A. naeslundii as an oral probiotic against oral carcinogenesis. The aggregation assay of the bacterium with C. albicans was conducted. The polymicrobial interactions of clinical strain C. albicans (ALC2) with A. naeslundii in nutrient broth exhibited lower co-aggregation compared to the auto-aggregation indicating the ability of A. naeslundii to reduce colonisation of C. albicans by inhibiting candidal dimorphism. In conclusion, L. salivarius REN could be a potential inhibitory agent against oral carcinogenesis. The high percentage protein similarities between L. salivarius REN with A. naeslundii shown the potential of A. naeslundii as an oral probiotic which able to inhibit oral carcinogenesis.