Increased chondroitin sulphate proteoglycan expression (B5 immunoreactivity) in metastases of uveal melanoma

Background: Metastatic uveal melanoma has a poor prognosis and limited therapeutic options. Proteoglycans are involved in tumor cell invasion and metastatic behavior. The mAbB5 stains a chondroitin sulphate proteoglycan (CSPG) on cutaneous melanoma cells. Here, we compare the B5-staining of CSPG in primaries and metastases of uveal melanoma. Material and methods: Immunohistopathological staining was performed in 15 cutaneous and 39 uveal melanoma samples. A score for intracellular and surface staining was established. B5 staining was compared in primaries and metastases of uveal melanoma using Student's t-test. Results: Eight of 11 (73%) uveal melanoma metastases were positive for B5-staining whereas only 5 of 28 (18%) primary uveal melanoma samples were B5-positive (P < 0.001). Nine of 15 cutaneous melanoma samples (60%) were B5-positive without significant difference between primary and metastatic lesions. Surface staining was found both on uveal melanoma metastases and cutaneous melanomas. Conclusions: CSPG was expressed significantly more often in metastases than in primaries of uveal melanoma. It potentially may be one factor associated with metastatic spread. Further studies are needed to determine its use as prognostic factor. The mAbB5 may also be a promising tool for immunotherapy due to its strong staining of CSPG on the surface of cutaneous and metastatic uveal melanoma cells.