Serum activity of DPPIV and its expression on lymphocytes in patients with melanoma and in people with vitiligo

Abstract

Background: Dipeptidyl peptidase IV, a multifunctional serine protease, is implicated in regulation of malignant transformation, promotion and further progression of cancer, exerting tumor-suppressing or even completely opposite - tumor-promoting activities. The aim of present research was to determine the serum DPPIV activity, as well as the percentages of CD26+ lymphocytes, CD26+ overall white blood cells and the mean fluorescence intensity of CD26 expression on lymphocytes in patients with melanoma, people with vitiligo and in healthy controls.

Methods: The activity of DPPIV in serum was determined by colorimetric test. Expression of DPPIV (as CD26) on immunocompetent peripheral white blood cells was done using flow cytometry analysis.

Results: Data from our study show for the first time statistically significant decrease: in the serum DPPIV activity, in the percentage of CD26+ overall white blood cells and in the percentage of lymphocytes in patients with melanoma in comparison to healthy control people. In addition, significantly lower serum DPPIV activity was found in the group of patients with melanoma in relation to people with vitiligo too.

Conclusion: This study indicates the need for exploring the cause and the importance of the disturbances in the serum DPPIV activity and in the CD26 expression on immunocompetent cells in complex molecular mechanisms underlying the development and progression of melanoma.

Figure 1

Serum DPPIV activity in healthy controls (C), in people with vitiligo (V), in patients with melanoma (M), and in patients with other malignant skin tumors (MST) or benign skin changes (BS). Xav+/−SD are cut off values obtained from healthy controls. Green circles with borders represent melanoma patients without metastases, while green circles without borders represent melanoma patients with metastatic disease. There is a statistically significant decrease in the DPPIV serum activity in patients with melanoma in comparison to healthy controls (Wilcoxon rank sum test with continuity correction: W = 723; p < 0.0004) and as well as in relation to people with vitiligo (Wilcoxon rank sum test with continuity correction: W = 206; p < 0.0004).

Figure 2

(A) percentage of CD26+ overall white blood cells, (B) percentage of CD26+ lymphocytes, (C) mean fluorescence intensity (MFI) of CD26 expression on lymphocytes and (D) percentage of lymphocytes, in healthy controls (C), in people with vitiligo (V), in patients with melanoma (M), and in patients with other malignant skin tumors (MST) or benign skin changes (BS). Xav+/−SD are cut off values obtained from healthy controls. Green circles with borders represent melanoma patients without metastases, while green circles without borders represent melanoma patients with metastatic disease. There is a statistically significant decrease in the percentage of CD26+ overall white blood cells, (Wilcoxon rank sum test with continuity correction: W = 679.5; p < 0.00006), as well as in the percentage of lymphocytes (Wilcoxon rank sum test with continuity correction: W = 644.5; p < 0.00003) in patients with melanoma compared to healthy controls.