01.03 Adiponectin Induces Carcinogenic Macrophage Cytokine Expression – A Link to Early-Onset Colon Cancer

M. A. Parks1, 2, K. Scheurlen1, D. Snook1, C. Seraphine1, S. Galandiuk1  1Price Institute of Surgical Research, Division Of Colorectal Surgery, Louisville, KENTUCKY, USA 2University of Louisville, School Of Medicine, Louisville, KENTUCKY, USA

Introduction: Early onset colorectal cancer (EOCRC)(<50 years) is a growing cause of cancer-related deaths in the United States. Similarly, obesity rates continue to trend up. CRC progression is affected by inflammation mediated through tumor-associated macrophages (TAMs) of a largely anti-inflammatory M2-like phenotype, that is associated with worse CRC prognosis.

The impact of the adipokine adiponectin on M2-like macrophages and progression in CRC is poorly understood. Anti-inflammatory cytokine expression, downregulation of the transcription factor Peroxisome Proliferator Activated Receptor g (PPARγ) and upregulation of Nuclear factor-κB (NF-κB) are associated with advanced tumor stage and worse outcome in patients with CRC. The aim was to investigate the effects of adiponectin on tumor-promoting cytokines, transcription factors, and cell surface markers following adiponectin treatment in M2-like macrophages.

Methods: THP-1 cells were seeded onto culture plates and polarized into a distinct M2-like macrophage phenotype within 14 days. Cells were then treated with adiponectin for either 3, 6, 18, or 24 hours. mRNA was extracted and qRT-PCR was performed. Cytokine gene expression was measured relative to untreated control cells. For statistical analysis, paired t-tests were used.

Results: Following adiponectin treatment, M2-like macrophages showed a peak upregulation of the anti-inflammatory tumor-promoting cytokines C-C Motif Chemokine Ligand 22 (CCL22) after 24 hours (42-fold, p=0.002) and interleukin-8 (IL-8) after 18 hours (683-fold, p=<0.001), while IL-10 expression was maximally downregulated after 24 hours (- 9-fold, p=<0.001) (Fig. 1B). Peak upregulation of the tumor-promoting proinflammatory cytokines IL-6 (1130-fold, p=0.001) and IL-1b (485-fold, p=<0.001) was reached after 6 hours of adiponectin treatment, respectively (Fig. 1A). Expression of the M1-like macrophage surface marker CD80 was maximally increased after 6 hours (52-fold, p=0.003), while expression of the M2-like marker CD206 showed the lowest decrease at 24 hours (- 30-fold, p=<0.001) (Fig. 1C). NF-κB expression was increased at all time points with a peak at 6 hours (20-fold, p=<0.001) (Fig. 1D). We observed no significant change in expression of PPARγ or anti-inflammatory CCL18.

Conclusion: Adiponectin promotes expression of cancer-related cytokines and NF-κB in M2-like macrophages, thereby triggering cancer progression in CRC. Upregulation of the M1-like cell surface marker CD80 following adiponectin treatment shows that a phenotypic change of macrophages towards an M1-like proinflammatory phenotype is induced. Adiponectin may be an important a link between obesity, inflammation and EOCRC.