Leptin and gastro-intestinal malignancies.

Obesity is a well-established risk factor for the development and mortality from several cancers, including adenocarcinoma of the oesophagus, oesophago-gastric junction and colorectum. Despite a large body of epidemiological evidence describing this relationship, the mechanisms relating obesity and cancer are only starting to be uncovered. The altered secretion of metabolically active, pro-inflammatory adipocytokines from adipose tissue is believed to play a key role, and leptin is believed to be a key player in obesity-related carcinogenesis, as well as being the most extensively studied of the adipokines. In this literature review, we aim to examine the association between leptin and cancers of the gastro-intestinal tract. For each individual cancer, we examine and present the published data examining the role of leptin in both cell and animal models, the association between circulating leptin levels and cancer risk, and finally the expression of the leptin system in human gastro-intestinal tract tumours, in relation to tumour biology, stage and patient outcome.