1117P - Intratumoral microbiota is associated with prognosis in Chinese patients with skin melanoma

Background

Skin melanoma, particularly acral melanoma, is known for its poor prognosis, often exacerbated by infections and chronic ulcers. Recent research has highlighted the significant role of intratumoral microbiota in various cancers, but its impact remains less understood in Chinese patients with skin melanoma. This study aims to investigate the intratumoral microbiota in melanoma among this group and explore its potential influence on disease progression.

Methods

One hundred melanoma tissue samples from stage III/IV skin or acral melanoma patients at Sun Yat-sen University Cancer Center, collected between 2015 and 2021, were retrospectively collected and underwent LPS immunohistochemistry (IHC). Kaplan-Meier analysis was used to assess the relation of LPS expression and patients overall survival. Microbial diversity was analyzed through 16S rRNA sequencing. Spatial transcriptomics was applied to map LPS-positive and LPS-negative regions, enabling the exploration of transcriptional differences and cell distributions.

Results

Patients with high LPS levels exhibited a median overall survival (mOS) of 13.7 months (95% CI, 10.6–16.9), which was shorter compared to those with low LPS levels, who had not yet reached median survival. Analysis of tumor microbiota revealed significant diversity, with high proportions of Bifidobacterium, Vibrio, Bacillus, Clostridium sensu stricto, and Pseudomonas, among which Pseudomonas was the dominant genus. Spatial transcriptomic analysis of LPS-positive melanoma tissues showed an increased proportion of M2 macrophages and a decreased proportion of effector T cells. Gene set enrichment analysis (GSEA) further indicated the activation of epithelial-mesenchymal transition (EMT) pathways.

Conclusions

High levels of microbiota within melanoma tissues are correlated with poor overall survival and may facilitate tumor immune evasion and metastasis.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.