Expression of MMP-10, MMP-21, MMP-26, and MMP-28 in Merkel cell carcinoma

Abstract

Merkel cell carcinoma (MCC) is an aggressive cutaneous tumor with poor outcome and increasing incidence. We examined by immunohistochemistry the expression of three novel matrix metalloproteinases (MMPs)-MMP-21, MMP-26, and MMP-28-in 44 primary MCC tumors and six lymph node metastases while MMP-10 served as a positive control. Their mRNA expression was also studied in the UISO MCC cell line basally and after various stimulations using quantitative real-time PCR. MMP-28 was observed in tumor cells of 15/44 samples especially in tumors <2 cm in diameter (p = 0.015) while 21/44 specimens showed MMP-28 in the tumor stroma. Expression of MMP-21 was demonstrated in tumor cells of 13/43 samples. MMP-26, instead, was positive in stromal cells (17/44) and its expression associated with tumors >or=2 cm in diameter (p = 0.006). Stromal expression of MMP-10 was the most frequent finding of the studied samples (31/44), but MMP-10 was detected also in tumor cells (17/44). Most of the metastatic lymph nodes expressed MMP-10 and MMP-26. MMP-10, MMP-21, and MMP-28 mRNAs were basally expressed by the UISO cells, and the corresponding proteins were detectable by immunostaining of cultured cells. IFN-alpha and TNF-alpha downregulated MMP-21 and MMP-28 expression. Our results suggest that novel MMPs may have a role in MCC pathogenesis: especially that MMP-26 expression in stroma is associated with larger tumors with poor prognosis. Expression of MMP-21 and MMP-28 seems to associate with the tumors of lesser malignant potential. We also confirm the previous finding on the role of MMP-10 in MCC pathogenesis.