Distribution of several activating receptors on Natural Killer (NK) cells from tumors and peripheral blood in colorectal cancer (CRC) patients

YAMILA ROCCA; JUAN M. ARRIAGA; ALICIA I. BRAVO; MORA AMAT; MICHELE BIANCHINI; JOSÉ MORDOH; ESTRELLA LEVY

Buenos Aires

Congreso; Congreso Franco-Argentino de Inmunología; 2010

Despite NK cells being originally identified and named because of their ability to kill tumor cells in vitro, only limited information is available in humans, on NK infiltrating malignant tumors and from peripheral blood. NK cell recognition of target cells is guided by the balance of the activating and inhibitory signals given by different groups of surface receptors. The purpose of the present study was to analyze NK tumor infiltrating cells (CRC-NKi), as well as NK from peripheral blood (CRC-NK-PB) in CRC patients and to identify a potential profile of NK receptors expression. Samples were obtained from 11 healthy volunteers (HV) and 16 patients. Tissues were obtained immediately after surgical resection of their primary tumors, mechanically processed, and mononuclear cells (MNC) were isolated using ficoll-hypaque density gradient. The same procedure was utilized to isolate peripheral blood (PB) MNC (PBMC) from CRC patients and healthy volunteers. Cells were directly analyzed by flow cytometry. We observed that the percentage of CRC-NKi identified as CD3-CD56+CD45+ was consistently lower (mean value, 4,4 ± 2,8) than its CRC-NK-PB counterpart (mean value 18,76 ± 2,1) (p<0.05). CCR-NKi displayed a peculiar surface pattern in activating receptors, calculated as percentage of positive cells in the CD56+CD3- population. CD16, NKG2D, NKp46, CD94, CD161 and DNAM1 were expressed in a fewer number of cells compared with CRC-NK-PB (p<0.01). In a clustering analysis (TMeV software) global comparisons including expression of all receptors between all samples showed that NKG2D is the most significant discriminant receptor (p<0.05) between NK-PB-CCR (mean value 88,5 ± 3,5) and NK-PB-HV (97.2 ± 3.2). The present study of a small group of CRC patients suggest that lower NKG2D expression could be a hallmark in NK-PB-CCR. CRC-NKi cells display particular phenotypic features that could affect their functional abilities, and should be further analyzed in a larger number of patients.