# Intratumoral Staphylococcus pseudintermedius Promotes Proliferation and Migration of CMT-U27 Cells Through the TLR2/PI3K/Akt Signaling Pathway

## TL;DR

This study shows that a specific bacteria found in dog mammary tumors promotes cancer cell growth and movement through a key signaling pathway.

## Contribution

The study identifies Staphylococcus pseudintermedius as a driver of canine mammary tumor progression via the TLR2/PI3K/Akt pathway.

## Key findings

- Staphylococcus pseudintermedius promotes proliferation and migration of CMT-U27 cells.
- The TLR2/PI3K/Akt pathway is activated by Staphylococcus pseudintermedius in tumor cells.
- Inhibiting TLR2 reduces expression of genes linked to cancer progression.

## Abstract

Increasing evidence suggests that intratumoral microorganisms and their metabolites can modulate cancer initiation and progression. However, the composition and functional roles of intratumoral bacteria in canine mammary tumors remain unclear. This study investigated the intratumor microbiome in dogs with mammary tumors. Amplicon sequencing revealed that both the species richness and diversity of intratumor microbiome in tumor tissues were significantly lower than in non-tumorous healthy mammary tissues. Statistical analysis indicated that Burkholderiales and Roseateles were significantly enriched in tumor tissues at different taxonomic levels. Subsequently, bacteria originating from five different genera were isolated from clinical mammary tumor tissues, among which Staphylococcus pseudintermedius was the most frequently isolated species. Functional assays demonstrated that Staphylococcus pseudintermedius promoted the proliferation and migration of canine mammary cancer cells by activating the TLR2/PI3K/Akt pathway. This study revealed a functional link between tumor-associated bacteria and cancer progression, providing further theoretical support for the close relationship between intratumor microbiome and canine mammary tumors.

Increasing evidence suggests that intratumoral microorganisms and their metabolites can modulate cancer initiation and progression. However, the composition and functional role of intratumoral bacteria in canine mammary tumors (CMTs) remain unclear. In this study, we investigated the functional significance of tumor-derived Staphylococcus in CMTs, focusing on its effects on the proliferation and migration of CMT-U27 cells. 16S rRNA sequencing revealed reduced alpha diversity in CMT tissues, with Staphylococcus pseudintermedius identified as the most frequently isolated species. Functional assays, including CCK-8, wound healing, RT-qPCR, and Western blot analyses, demonstrated that intratumoral Staphylococcus pseudintermedius significantly enhanced cellular proliferation and migration. Mechanistically, Staphylococcus pseudintermedius significantly upregulated the expression of TLR2, as well as the phosphorylation levels of PI3K, Akt and P70S6K. The inhibition of TLR2 using C29 suppressed the mRNA expression of VEGF, MMP9, MMP2, and EGFR. Collectively, these findings indicate that intratumoral Staphylococcus pseudintermedius promotes the proliferation and migration of CMT-U27 cells through activation of the TLR2/PI3K/Akt pathway, highlighting a functional link between tumor-associated bacteria and cancer progression.