BACTERIOME ANALYSIS IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA

INTRODUCTION AND OBJECTIVES: Esophageal cancer ranks among the ten most frequent types of cancer worldwide and in Brazil. In our country, esophageal squamous cell carcinoma (ESCC) corresponds to more than 80% of diagnosed cases. It is associated with well-established risk factors such as exposure to tobacco, alcohol, consumption of hot drinks, and its incidence is more pronounced in individuals belonging to the most vulnerable sections of society. In this context, socioeconomic status (SES), being a complex trait, requires different variables that are used as a proxy in an attempt to measure it, such as education. However, other aspects cannot be ignored when evaluating their association with the development of the ESCC. From a biological perspective, diet and changes in the esophageal bacteriome have already been associated with the risk of ESCC, since its specific richness and constitution may be affected by environmental exposures. Based on this, the objective of this work was to initially characterize the esophageal bacterial communities of patients diagnosed with ESCC at the National Cancer Institute (INCA) and subsequently evaluate their association with SES. MATERIAL AND METHODS: The esophageal bacteriome profile was obtained by sequencing the V4 region of the bacterial 16S rRNA gene, using Illumina MiSeq. After sequencing, low-quality reads were excluded using standard parameters in QIIME. The filtered reads were clustered into operational taxonomic units (OTU) against the Human Oral Microbiome Database (HOMD) reference sequence collection. All statistical analyzes were performed in R environment, using specific packages. RESULTS AND CONCLUSION: The bacteriome of tumor and adjacent non-tumor tissue from 34 patients diagnosed with ESCC was analyzed. Pairwise comparison of the two tissue types showed no differences in alpha or beta diversity. On the other hand, we identified 33 differentially represented OTUs. Among them, the genera Actinobacillus and Streptococcus were less represented in tumor tissue compared to adjacent non-tumor tissue; while the genus Neisseria was more represented in tumor tissue when compared to adjacent non-tumor tissue. We also evaluated bacteriome variations within non-tumor tissues and tumors according to education levels (< 8 years vs ≥ 8 years of formal education) and found no differences in alpha and beta diversity, nor identified significantly represented OTUs. But the core microbiome analysis showed that patients with higher education levels had a higher number of core genera in both tissues. CONCLUSION: Although preliminary, our data show that the esophageal bacteriome is affected during carcinogenesis and that SES might be associated with some of the observed changes.