Breast cancer cohort study identifies an effective, non-invasive, breath-based diagnostic linked to cellular environment-dependent, novel methylation metabolisms

Volatile organic compounds (VOCs) demonstrate promise as non-invasive diagnostic tools. However, lack of mechanistically linked VOCs with biomarker discovery platforms limit delivery to the clinic. In this cohort-based study, we observed significant alterations of chloride-containing volatile fluxes, inclusive of methyl chloride (MeCl), in the breath of cancer patients that are consistent with our newly described metabolic model, derived through in vitro cellular assays and in vivo mice models. The diagnostic accuracy of this cohort study (60 patients) is equivalent to mammogram approaches. This newly identified and novel metabolism along with associated diagnostic biomarkers were initially identified through headspace studies of breast cancer cell lines which were deprived of serum, glucose or oxygen, similar to cellular conditions in tumors. In these cellular assays MeCl was consistently informative of cellular stress. Under resource limited conditions cellular production of MeCl was significantly reduced, and in several cases, cellular metabolism shifted to consumption. We present a new “push-pull” model in which cellular production of MeCl is linked to cellular methylation potential and methyl-transferase activity while consumption of MeCl is associated with methionine generation. Neither consumption nor production metabolisms have been described or quantified in humans or human tissues previously. The cellular headspace-derived model was tested using xenograft tumour bearing mice, which demonstrated reduced MeCl production, consistent with this model This work therefore presents a potentially powerful breath biomarker for cancer that translates from cellular and mice models through to human subjects.