Variation in oral microbiome is associated with future risk of lung cancer among never-smokers

Abstract

Objective: To prospectively investigate whether diversity in oral microbiota is associated with risk of lung cancer among never-smokers.

Design and setting: A nested case-control study within two prospective cohort studies, the Shanghai Women's Health Study (n=74 941) and the Shanghai Men's Health Study (n=61 480).

Participants: Lifetime never-smokers who had no cancer at baseline. Cases were subjects who were diagnosed with incident lung cancer (n=114) and were matched 1:1 with controls on sex, age (≤2 years), date (≤30 days) and time (morning/afternoon) of sample collection, antibiotic use during the week before sample collection (yes/no) and menopausal status (for women).

Main outcomes and measures: Metagenomic shotgun sequencing was used to measure the community structure and abundance of the oral microbiome in pre-diagnostic oral rinse samples of each case and control. Multivariable logistic regression models were used to estimate the association of lung cancer risk with alpha diversity metrics and relative abundance of taxa. The Microbiome Regression-Based Kernel Association Test (MiRKAT) evaluated the association between risk and the microbiome beta diversity.

Results: Subjects with lower microbiota alpha diversity had an increased risk of lung cancer compared with those with higher microbial alpha diversity (Shannon: p_trend=0.05; Simpson: p_trend=0.04; Observed Species: p_trend=0.64). No case-control differences were apparent for beta diversity (p_MiRKAT=0.30). After accounting for multiple comparisons, a greater abundance of Spirochaetia (OR_low 1.00 (reference), OR_medium 0.61 (95% CI 0.32 to 1.18), OR_high 0.42 (95% CI 0.21 to 0.85)) and Bacteroidetes (OR_low 1.00 (reference), OR_medium 0.66 (95% CI 0.35 to 1.25), OR_high 0.31 (95% CI 0.15 to 0.64)) was associated with a decreased risk of lung cancer, while a greater abundance of the Bacilli class (OR_low 1.00 (reference), OR_medium 1.49 (95% CI 0.73 to 3.08), OR_high 2.40 (95% CI 1.18 to 4.87)) and Lactobacillales order (OR_low 1.00 (reference), OR_medium 2.15 (95% CI 1.03 to 4.47), OR_high 3.26 (95% CI 1.58 to 6.70)) was associated with an increased risk of lung cancer.

Conclusions: Our prospective study of never-smokers suggests that lower alpha diversity was associated with a greater risk of lung cancer and the abundance of certain specific taxa was associated with altered risk, providing further insight into the aetiology of lung cancer in the absence of active tobacco smoking.

Keywords: lung cancer; non-small cell lung cancer.

Figure 1

Alpha diversity associated with risk of lung cancer in two prospective cohorts of never-smokers. LOWESS fit of local proportion of cases. For each dot, the X axis is the value of alpha diversity and the Y axis is the proportion of cases among the patients within the local range (±0.1*total range) of the corresponding value in the X axis. The red dashed line is LOWESS fit of those dots. LOWESS, locally weighted least squares.

Figure 2

Oral microbiome composition in never-smoking lung cancer cases and controls in the Shanghai Men’s Health Study (SMHS) and Shanghai Women’s Health Study (SWHS). (A) Distribution and description of the microbiome community in all never-smokers (lung cancer cases: n=113; controls: n=114). Size of circles is representative of relative abundance of taxa in the phylogenetic tree. Colours from red to green represent taxa within the five phyla with the greatest relative abundance (Proteobacteria: 30.3% controls, 30.3% cases; Firmicutes: 26.6% controls, 28.7% cases; Bacteroidetes: 21.7% controls, 19.3% cases; Fusobacteria: 9.3% controls, 9.3% cases; Actinobacteria: 8.7% controls, 9.1% cases). Uncoloured taxa are within rare phyla. The size of the wedge reflects the number of unique phylogenetic attributes in each phylum, not the relative abundance. (B) Summary of the results of the case–control analyses. The blue and purple colours represent the six taxa significanctly associated with risk of lung cancer (FDR <0.10) when adjusted for sex, age, sample collection time, menopause status (for women), education and antibiotic use. FDR, false discovery rate.