Novel multiplex method to assess insulin, leptin and adiponectin regulation of inflammatory cytokines associated with colon cancer

The role of altered levels of insulin, leptin and adiponectin in contributing to the observed increased risk of colon cancer associated with obesity remains to be determined. Elevated insulin and leptin associated with obesity are linked to inflammatory responses. Conversely, adiponectin levels are reduced in obese individuals and this hormone is generally associated with anti-inflammatory responses. Inflammatory cytokines are key components of processes linked with carcinogenesis. Insulin, leptin and adiponectin receptor expression profiles were assessed in human normal, adenomatous polyp and tumour tissue. Insulin, leptin and adiponectin regulation of inflammatory cytokines previously identified as being associated with early events in colon carcinogenesis were further investigated here using a surrogate colon epithelial cell line and a custom designed GeXP assay of the inflammatory cytokines (CCL20, CXCL1, CXCL2, CXCL3, CXCL11, IL1RN, CXCL4, IL8, CCL19, CCL21, CCL23, CCL5, IL10RB and TNFRSF1A). Mean insulin, leptin and adiponectin receptor expression levels were lower in adenomatous polyp samples in comparison with normal and tumour tissue. In contrast to leptin, insulin significantly reduced CCL20 and CXCL11 and increased CXCL3 expression. Full length adiponectin, but not globular adiponectin, induced CCL5, CXCL1, CXCL3 and CCL20 gene expression. GeXP assay permitted measurement of changes in gene expression of cytokines in response to insulin and adiponectin, indicating the potential for insulin and adiponectin regulation of mediators of inflammation associated with early events in colon carcinogenesis.