Potential Utility of Microbial Metabolites in Cancer Diagnostics

Objectives: Recent evidence indicates that oral microbiome profiling could be a potentially useful diagnostic marker for oral cancer, pancreatic cancer and leukemia. In addition, microbial volatile organic compounds (MVOCs), a major end product of their metabolism, have been used in the diagnosis of infectious and non-infectious diseases particularly through head-space sampling of cultures derived from clinical samples. We present here preliminary data on the possible utility MVOCs in the diagnosis of cancers.
Methods: We subjected Escherichia coli cultures (n=2), oral microbial cultures (n=3) feacal mcorobial cultures (n=5) and uninoculated control cultures (n=2) to MVOCs analysis. Solid-phase microextraction was used for MVOCs extraction which were then analyzed using Gas Chromatography/Mass Spectrometry. Meta-analysis, two-group and multi-group comparisons were done using XCMS software to find significant ion-peaks (fold change≥1.5, p≤0.01) in the headspace of culture media. Welch-Aspin test (fold change≥1.5, p≤0.01), ANOVA (p≤0.01) and principal component analysis (PCA) were used in addition.
Results: Two-group comparisons (Welch-Aspin test) showed production of 210 significant up-regulated ion-peaks in the headspace of oral microbial cultures in comparison with those of feacal cultures. There were 145 significant up-regulated ion-peaks in the headspace of cultured oral microbiota in comparison to the E. coli media. Multi-group comparisons (ANOVA) revealed approximately 1000 significant ion-peaks, which were able to separable into four principal component groups. Meta-analysis of three two-group comparisons identified 94 shared ion-peaks (p-value≤0.05) across three data groups (E. coli-culture vs. non-inoculated culture, oral-culture and feacal-culture vs. non-inoculated culture).
Conclusions: The utility of MVOCs as signature profiles to differentiate the gut and the oral microbiome and that of single organism in turn was confirmed in this pilot study. Our results validate the potential utility of MVOCs in detecting various human microbial niches.