Investigating the Effects of Lactobacillus Casei on Gene Expression of CLR, TLR-4, and NF-ĸb in Oral Rat Cancer Induced by 4-Nitroquioline 1-Oxide

Abstract

Background: Oral squamous cell carcinoma (OSCC) is the leading cause of mortality due to oral cancer. The anti-tumor effects of Lactobacillus casei (L. casei) on various tumors have been investigated, but the molecular mechanisms involved in these beneficial effects are not yet well understood. This study aimed to assess the anti-tumor effects of L. casei on the gene expression of receptors associated with the pathway pathogen recognition receptors, including tool-like receptor 4 (TLR4), and C-type lectin receptor (CLR) in the OSCC animal model induced by 4-Nitroquioline 1-Oxide (4NQO).

Methods: In this study, Twenty-eight male Wistar rats were divided into four groups of seven rats each: 1 (Control); 2 (4NQO-treated); 3 (live probiotic L. casei before and after treatment with 4NQO); 4 (live probiotic L. casei after treating with 4NQO). To induce the oral SCC model, the tongue of rats was treated with 4NQO solution using brush three times a week, and tongue carcinogenesis was followed for 16 consecutive weeks. Groups 3 and 4 received the 5×10⁸ cfu/kg body weight live probiotic L. casei through oral gavage. The tissue sections were stained with hematoxylin and eosin (H&E) for pathological examination. Real-time polymerase chain reaction (RT-PCR) was used to assess the TLR4, DC-SIGN, Bcl-2, and NF-κB gene expression levels in the blood samples of rats.

Results: According to the pathological findings, a well-differentiated invasive SCC was developed in > 77% of rats after 16 weeks of 4NQO treatment. Rats gavaged with the probiotic L. casei showed potent anticancer effects. Analysis of real-time PCR data showed the highest NFĸB gene expression in Group 4 compared to other groups (p-value < 0.001). Also, overexpression of the Bcl-2 gene was observed in Group 4 (p-value < 0.001). In addition, the expression of TLR4 and DC-SIGN genes in NQO-induced OSCC rat models that received L. casei was higher than in other groups (p-value < 0.05).

Conclusion: The present study's findings suggest that probiotic L. casei can be a potential strategy for treating OSCC by activating the NFĸB signaling cascade through increased expression of TLR4 and Dc-SIGN. However, more studies are needed in this regard.