In order to evaluate the significance of adhesion molecules expressed on melanocytic tumours for progression and prognosis in vivo, we studied
integrin expression (VLA-1 to
VLA-6, CD18, CD51, CD61) on 10 naevi, 40 primary
malignant melanomas, and 11
metastases by immunohistology using the APAAP technique. Evaluation was done by grouping the percentage of positive tumour cells in six categories. Statistical analysis (Wilcoxon rank test, Scheffe test) revealed significant differences in the expression of
VLA-1 (P < 0.0001),
VLA-2 (P = 0.0001),
VLA-5 (P = 0.0093),
VLA-6 (P = 0.0232), and CD61 (P = 0.0002) between naevi and primary
melanomas. Comparing primary
melanomas with
metastases, a statistically significant decrease in the expression of
VLA-1,
VLA-2, and
VLA-6 was detectable, as well as a significant increase in
VLA-4 and
VLA-5. There was no correlation between
integrin expression and tumour type (superficial spreading
melanoma, nodular
melanoma,
lentigo maligna melanoma), regression and ulceration. Changes of
VLA-1,
VLA-4, and
VLA-6 expression correlated with the tumour thickness of the primary
melanoma, but only
VLA-4 and
VLA-6 expression on primary
melanomas correlated significantly with the development of
metastases (P = 0.024 and P = 0.001). These changes of
integrin expression during tumour progression particularly, the data showing an increase of
VLA-4, and a decrease of
VLA-6 expression support the concept that
integrins are a new additional set of prognostic markers which indicate predisposition to the development of
metastases.