Trillions of microbes colonize the adult body. Changes in this community have already been tied to the risk and presence of arthritis, multiple sclerosis, irritable bowel syndrome and cancer. With more information on how these microbes are connected with cancer and cancer risk factors, such as genetic predispositions, smoking and other environmental factors, researchers hope to create individualized screening and treatment plans for cancer patients and for those at an increased cancer risk.

For this study, Guerrero-Preston and his colleagues extracted bacterial DNA from the saliva of 42 patients. Seventeen samples were drawn from people with head and neck squamous cell carcinoma, seven of which were positive for HPV and 10 of which were HPV-negative. Twenty-five noncancerous samples were used as a control.

The bacterial DNA found in the saliva was sequenced and sorted into groups of highly related populations. Through further DNA analysis, researchers were then able to determine the category, or genus, of bacteria to which each group belonged.

The researchers found differences in the bacterial populations present in cancerous versus noncancerous samples. Samples from patients with tumors, for example, showed increased populations of Streptococcus, Dialister and Veillonella genera, as well as decreased populations of Neisseria, Aggregatibacter, Haemophilus and Leptotrichia genera with respect to controls. Tumor samples also showed an increased prevalence of the Lactobacillus genus, which was present in 9.1 percent of tumor samples and in only 0.1 percent of the healthy controls. In addition, the researchers found correlations between the types of bacteria present and the patients’ HPV statuses. HPV-positive samples had increased abundances of Gemellaceae, Leuconostoc and Veillonella genera when compared to HPV-negative samples. Veillonella, for example, was present in 15 percent of HPV-positive tumor samples but was only present in 9.4 percent of HPV-negative tumor samples.

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More information: Rafael Guerrero-Preston et al, 16S rRNA amplicon sequencing identifies microbiota associated with oral cancer, Human Papilloma Virus infection and surgical treatment, Oncotarget (2014). DOI: 10.18632/oncotarget.9710