Background: Human adiponectin (ApN), a 30 kDa glycoprotein of 244-amino acids which is predominantlyproduced by adipocytes, exerts its effects via two receptors, namely adiponectin receptor-1 (adipo-R1) andadiponectin receptor-2 (adipo-R2) with differential binding affinity to globular adiponectin. Adiponectin receptorexpression has been studied in several cancer tissues. However, there are no studies of colorectal adenomas whichare considered to be precursors for colorectal carcinoma (CRC).
Objectives: In the present study, the expression ofadipo-R1 and adipo-R2 was investigated immunohistochemically in colorectal adenomas and colorectal carcinomatissues in an attempt to determine associations with these tumors. Materials and
Methods: The study enrolled 50CRC patients with tumor resection and 82 patients who were diagnosed with adenomatous polyps, classified asnegative for neoplasia, low-grade dysplasia (L-GD) or high- grade dysplasia (H-GD).
Results: Expression of bothadipo-R1 and adipo-R2 was found to be significantly lower in the CRCs than in colorectal adenomas (tubular andtubulovillous, p=0.009 and p<0.001, respectively). Adipo-R1 and adipo-R2 expression was also significantly lowerin the CRC group when compared with the groups of patients with low grade dysplasia, high-grade dysplasiaor no neoplasia (p=0.012 and p<0.001, respectively). In addition, it was observed that adipo-R2 expression wasgenerally positive in the non-neoplastic group irrespective of the adipo-R2 expression. In the L-GD, H-GD andCRC groups, the adipo-R2 result was positive whenever adipo-R1 result was positive but some patients withnegative adipo-R1 had positive adipo-R2 (p<0.001, p=0.004, p<0.001, respectively).
Conclusions: This studyindicated that ApN may play a role in the progression of colorectal adenomatous polyps to carcinoma throughactions on adipo-R1 and adipo-R2 receptors.