Administration of the simple sugar mannose, either alone or alongside chemotherapy, slows tumour growth in mice, reports a paper published online this week in Nature. Although promising, further research is needed to confirm these findings.

Many tumours undergo metabolic changes and display increased glucose uptake, raising the question of whether the administration of different types of sugar could affect their growth.

Kevin Ryan and colleagues investigated the effects of the monosaccharide (simple sugar) mannose on tumour cell growth. They report that mannose reduces tumour cell growth and suggest that it may interfere with glucose metabolism. Additionally, mannose significantly enhanced cell death when administered alongside the chemotherapeutic drugs cisplatin or doxorubicin. Mice with tumours were administered mannose both through a feeding tube three times a week and continuously via their drinking water. Mannose treatment was well-tolerated and appeared to reduce tumour growth both alone and in combination with doxorubicin.

Cell sensitivity to mannose correlated with lower levels of the enzyme phosphomannose isomerase (PMI). The authors tested for PMI levels in various human tumour cells (from ovarian, renal, breast, prostate, and colorectal cancers) and report differing cellular PMI levels both among and within tumour types. In particular, colorectal tumours had low levels of PMI, suggesting that they may be more sensitive to mannose. Furthermore, mice with colorectal cancer developed significantly fewer tumours when administered mannose.

The authors conclude that mannose treatment could potentially represent a simple, safe way to target tumour growth in many cancers.