Microbiota Biomarkers for Lung Cancer

Abstract

Non-small cell lung cancer (NSCLC) is the number one cancer killer and its early detection can reduce mortality. Accumulating evidences suggest an etiopathogenic role of microorganisms in lung tumorigenesis. Certain bacteria are found to be associated with NSCLC. Herein we evaluated the potential use of microbiome as biomarkers for the early detection of NSCLC. We used droplet digital PCR to analyze 25 NSCLC-associated bacterial genera in 31 lung tumor and the paired noncancerous lung tissues and sputum of 17 NSCLC patients and ten cancer-free smokers. Of the bacterial genera, four had altered abundances in lung tumor tissues, while five were aberrantly abundant in sputum of NSCLC patients compared with their normal counterparts (all p < 0.05). Acidovorax and Veillonella were further developed as a panel of sputum biomarkers that could diagnose lung squamous cell carcinoma (SCC) with 80% sensitivity and 89% specificity. The use of Capnocytophaga as a sputum biomarker identified lung adenocarcinoma (AC) with 72% sensitivity and 85% specificity. The use of Acidovorax as a sputum biomarker had 63% sensitivity and 96% specificity for distinguishing between SCC and AC, the two major types of NSCLC. The sputum biomarkers were further validated for the diagnostic values in a different cohort of 69 NSCLC cases and 79 cancer-free controls. Sputum microbiome might provide noninvasive biomarkers for the early detection and classification of NSCLC.

Keywords: bacteria; biomarkers; lung cancer; microbiome; sputum.

Figure 1

Four bacterial genera show different abundances between lung AC and SSC tissues and the matched normal lung tissues. Solid red line indicates median, while black line indicates quartiles of abundance (copies of bacterial DNA/µL) of each genera in the different types of specimens. * shows that the p-value is under 0.05 by a Mann–Whitney U test.

Figure 2

Five bacterial genera show different abundances in sputum of lung AS or SCC patients and cancer-free individuals. The solid red line indicates median, while the black line indicates quartiles of abundance (copies of bacterial DNA/µL) of each genera in the specimens. *, p < 0.05 determined by a Mann–Whitney U test).

Figure 3

Comparison of abundances of bacteria in tumor tissues of lung cancer patients and sputum of lung cancer patients and controls. Relative abundances of bacterial genera in tumor tissues (A) and sputum of lung cancer patients (B) as compared with their normal counterparts. High abundances of bacterial genera in tumor tissue or sputum specimens are shown above ratio of 1 (red line), whereas low abundances in tumor tissue or sputum specimens are shown below ratio of 11 (red line). *, p < 0.05 determined by a Mann–Whitney U test).

Figure 4

Receiver-operator characteristic (ROC) curve analysis of abundances of bacterial genera in sputum of cohort 1 comprising NSCLC patients and cancer-free controls. The area under the ROC curve (AUC) for bacterial genera conveys its accuracy for diagnosis and classification of NSCLC. (A) The combined use of Acidovorax and Veillonella produced 0.91 AUC. (B) The use of Capnocytophaga as a sputum biomarker could detect lung AC with 0.85 AUC. (C) The use of Acidovorax as a sputum biomarker had 0.85 AUC for differentiating between SCC and SC of the lungs.

Figure 5

ROC curve analysis of abundances of bacterial genera in sputum of cohort 2. (A) The combined use of Acidovorax and Veillonella produced 0.89 AUC. (B) The use of Capnocytophaga as a sputum biomarker could detect lung AC with 0.83 AUC. (C) The use of Acidovorax as a sputum biomarker had 0.83 AUC for differentiating between SCC and SC of the lungs.