High fat diet induced obesity modulates melanoma tumour microenvironment in low density lipoprotein receptor deficient LDLR-/- mouse model.

Inflammation and altered immune response are the main features of obesity and contribute greatly to the promotion of obesityrelated metabolic complications, especially cancer development and progression. Adipose tissue expansion is associated with increased tumour infiltration by regulatory T cells (T-regs) which are critical regulators of the adaptive immune response. Adipocytes and infiltrating immune cells secrete pro-inflammatory adipokines and cytokines providing a microenvironment favourable for tumour growth. LDLR-/- mice fed on high fat diet and control diet were subcutaneously injected with 5??105 syngeneic melanoma cells (B16F10). After two weeks, tumours and spleens were dissected. Tumours and bodies were weighed at endpoint and then the percentage of CD4+CD25+FOXP3+T-regs population among splenocytes was determined by flow cytometry (FACS). High Fat Diet (HFD) feeding increases solid tumour growth combined with increases in adipose tissues of LDLR-/- tumour bearing mice. The percentage of T-regs among spleen lymphocytes was significantly higher in tumour bearing mice fed on high fat diet compared with those fed on control diet. Obesity may promote tumour progression by favouring an immune suppressive tumour microenvironment.