To the Editors:
Matrix metalloproteinase-2 (MMP-2) expression is associated with the high Breslow index and with the progression of melanoma.1,2 However, no studies relating MMP-2 to other histopathologic prognostic factors have been published to the best of our knowledge. The presence of the tissue inhibitor of metalloproteinase-2 (TIMP-2) in association with other prognostic factors has also not been studied.
We performed a cross-sectional study to evaluate the immunohistochemical expression of MMP-2 and of TIMP-2 in cutaneous melanoma, particularly as it relates to histopathologic prognostic factors and to melanoma metastases.
The research was approved by the Committee of Research in Ethics at the Federal University of Health Sciences of Porto Alegre, Brazil.
The variables evaluated in the study were age, sex, histological subtype of the melanoma, histopathologic prognostic factors, skin metastases, and the immunohistochemical expression of MMP-2 and TIMP-2 in the primary cutaneous melanomas and cutaneous metastases of melanoma.
The slides were stained with hematoxylin-eosin. Immunoperoxidase stains were carried out using the avidin-biotin immunoperoxidase technique. Diaminobenzidine and 3-amino-9-ethylcarbazole (AEC) counterstained with Giemsa were the chromogen solutions applied to visualize the antigen-antibody complex.
To analyze the expressions of MMP-2 and of TIMP-2, the semiquantitative method was used. In primary melanomas, the expressions of MMP-2 and TIMP-2 were evaluated in the stroma, in the vessels, in the epidermal tumor cells, in the dermal tumor cells, and in the keratinocytes. The tumor cells and stroma in the metastases were evaluated.
Statistical analyses were performed with the Spearman correlation coefficient, the Student t test, Mann-Whitney U, the Kruskal-Wallis H test, and the chi-square test. A level of 5% (P < 0.05) was used to consider statistical relevance. The data were analyzed using the SPSS 15.0 statistical program.
A total of 86 cases were evaluated; 73 primary cutaneous melanomas and 13 metastases. All the slides of primary cutaneous melanoma and of cutaneous metastases of melanoma expressed MMP-2 and TIMP-2.
The following statistical significances were found in MMP-2 expression: Age: the expression of MMP-2 in epidermal tumor cells was correlated inversely with the age of the individuals. Older patients presented less expression of the enzyme (rs = −0.27; P = 0.02). Histological subtype of melanoma: significance of the MMP-2 expression in the epidermal tumor cells in melanomas of the superficial spreading subtype (P < 0.01). Breslow index: significance of the correlation between the expression of MMP-2 in the dermal tumor cells and the Breslow thickness of the lesions. The deeper the median Breslow index of the lesions, the higher the expression of the enzyme (rs = 0.33; P = 0.01). Clark level: significance in the correlation with the expression of MMP-2 in the dermal tumor cells. The higher the Clark level of the lesions, the higher the expression of the enzyme (rs = 0.26; P = 0.04).
The following statistical significances were found in TIMP-2 expression: Age: the expression of TIMP-2 in the epidermal tumor cells was inversely correlated with the patients' age (rs = −0.35; P < 0.01). Sex: significance was found in the presence of the inhibitor in the stroma and in the female sex (P < 0.01). Breslow index: significance in the correlation between the expression of TIMP-2 in dermal tumor cells and Breslow thickness. The higher the median Breslow index of the lesions, the greater the expression of the inhibitor (rs = 0.32; P = 0.01). Clark level: significance in the correlation between the expression of the TIMP-2 in the epidermal cells and the Clark level. The higher the Clark level of the lesions, the lower the expression of the inhibitor (rs = −0.30; P < 0.01). Mitotic index: significance in the expression of TIMP-2 in the dermal tumor cells. The higher the mitotic index considered, the higher the expression of the inhibitor (rs = 0.32; P = 0.02) (Table 1).
The variables of lymphatic and blood vessel invasion, perineural invasion, and microscopic satellitosis could not be analyzed due to the very low frequency of events observed.
Photographs showing expression of MMP-2 and of TIMP-2 in primary melanoma and cutaneous metastases are shown in Figures 1 and 2.
In this study, MMP-2 had higher expression in young patients, in superficial spreading melanomas, in deeper melanomas, and in all cutaneous melanoma metastases.
We conclude that MMP-2 is an enzyme that can participate in initial (high expression in epidermal tumor cells) and invasive (association with high Breslow and Clark index) phases of primary cutaneous melanoma development and it is more common in young patients and being present in the cutaneous metastases of melanoma. The immunohistochemical expression of TIMP-2 is similar to MMP-2 in primary melanoma and cutaneous metastases, and it is also correlates with mitotic index.
The contribution of the present study is to demonstrate that MMP-2 is more common in young patients with melanoma. Thus, young patients are a group with higher risk for disease progression.
This article was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Capes, Brazil. The authors thank Mrs. Rosalva Tereza Meurer, Prof. Dr. Maria Isabel Albano Edelweiss, Prof. Dr. Mário Bernardes Wagner and Kauê Marcolin Duro, MD, for their invaluable help.
Maria Carolina W. Rey, MD, MSc
Renan R. Bonamigo, MD, PhD
André Cartell, MD
Roque Furian, MD
Raquel Bonfá, MD
Rafael Bonfá, MD
Universidade Federal de Ciências da Saúde de Porto Alegre, (UFCSPA) Brazil
1. Redondo P, Lloret P, Idoate M, et al. Expression and serum levels of MMP-2 and MMP-9 during human melanoma progression. Clin Exp Dermatol
2. Väisänen AH, Kallioinen M, Turpeenniemi-Hujanen T. Comparison of the prognostic value of matrix metalloproteinases 2 and 9 in cutaneous melanoma. Hum Pathol