Rapid-dissolution dynamic nuclear polarisation (RD-DNP) is an emerging technique in liquid-state NMR and MRI, which yields up to 10,000-fold signal enhancements1. Using RD-DNP methodology, we aim to develop novel molecular probes of cancer-related metabolic processes in cell suspensions and in vivo.
Methylglyoxal is a highly-reactive keto-aldehyde, which is generated as a side product in the glycolytic pathway in cells, but quickly converted to D-lactate by two glyoxalase enzymes2. It is considered to be a ‘faulty metabolite’, with its role in biology still remaining enigmatic. Due to its high reactivity, it is capable of damaging cell proteins by non-specific chemical binding and cross-linking, thus causing pathological changes. In 1967, Szent-Györgyi et al. postulated that methylglyoxal might be a regulator of cell division and development of cancer3, however, despite this claim, only limited research has been done on this metabolite.
We developed a RD-DNP method for hyperpolarisation of [2-13C]methylglyoxal that we had chemically synthesised. The glyoxalase reactions are known to be very rapid and they have not been previously amenable to be studied by NMR in whole cells4. The RD-DNP approach enabled us to capture time courses of these reactions with high resolution and signal-to-noise ratio, as hyperpolarised methylglyoxal was quickly metabolised to D-lactate in a suspension of red blood cells.
Our kinetic data formed the basis of a quantitative description of solute flux via the glyoxalase pathway, thus probing the activity of the enzymes in situ. In addition, we demonstrated that RD-DNP is applicable to detecting glyoxalase activity in cancer cells, including in vivo in tumour-bearing mice, on the sub-minute time scale. The developed approach will provide new ways of detecting abnormal cells in the body, including those with inborn errors of metabolism and their response to therapy, with expected translation into the clinic.