Microbiomic differences at cancer-prone oral mucosa sites with marijuana usage

Abstract

Marijuana smoke contains cannabinoids, immunosuppressants, and a mixture of potentially-mutagenic chemicals. In addition to systemic disease, it is thought to contribute to oral disease, such as tooth loss, tissue changes in the gums and throat, and possibly oral pharyngeal cancer. We used a cross-sectional study of 20 marijuana users and 19 control non-users, to determine if chronic inhalation-based exposure to marijuana was associated with a distinct oral microbiota at the two most common sites of head and neck squamous cell carcinoma (HNSCC), the lateral border of the tongue and the oral pharynx. At the tongue site, genera earlier shown to be enriched on HNSCC mucosa, Capnocytophaga, Fusobacterium, and Porphyromonas, were at low levels in marijuana users, while Rothia, which is found at depressed levels on HNSCC mucosa, was high. At the oral pharynx site, differences in bacteria were distinct, with higher levels of Selenomonas and lower levels of Streptococcus which is what is seen in HNSCC. No evidence was seen for a contribution of marijuana product contaminating bacteria to these differences. This study revealed differences in the surface oral mucosal microbiota with frequent smoking of marijuana.

Figure 1

Boxplots of Shannon Diversity Index, Margalef Richness, and Pielou’s Evenness compare marijuana nonusers and marijuana (MJ) users for taxa identified at the two mucosal sites. The Student’s t test compared the significance of taxa differences for users and nonusers using each test. (A) Shannon, tongue t < 0.831 and oral pharynx t < 0.249. (B) Margalef, tongue t < 0.717 and oral pharynx t < 0.204. (C) Evenness, tongue t < 0.819 and oral pharynx, t < 0.507.

Figure 2

Bar plot of most common genera found at the two mucosal sites in marijuana users and control nonusers.

Figure 3

Taxa identified as distinct between marijuana, M, and control, C, groups at the two sites using LEfSe analysis. (A) LDA scores show significant differences in bacteria at the lateral border of the tongue in the marijuana and control nonusers. (B) Cladogram constructed shows the phylogenetic distribution of the differentially abundant taxa. (C) LDA scores show differences at the oral pharynx in the marijuana group and the controls. (D) Cladogram reveals phylogenetic distribution of differentially abundant taxa at the oral pharynx site in the marijuana and control groups.