Expression of cancer-testis antigens (MAGE-A1, MAGE-A3/6, MAGE-A4, MAGE-C1 and NY-ESO-1) in primary human uveal and conjunctival melanoma

AIM

Metastatic disease in ocular melanoma remains untreatable, is associated with late detection and is resistant to conventional systemic therapies. Many tumours including cutaneous melanoma express specific cancer-testis (CT) antigens and vaccines targeting these antigens can induce T-cell-mediated and humoural immune responses. The authors examined primary uveal and conjunctival melanomas for expression of CT antigens to assess their potential as targets for ocular melanoma immunotherapy.

METHODS

Paraffin-embedded uveal (n=32) and conjunctival (n=15) melanomas were assessed by immunohistochemistry for melanocyte differentiation antigens (gp100, Melan-A/MART-1 and tyrosinase), and CT antigens (MAGE-A1, MAGE-A3/6, MAGE-A4, MAGE-C1 and NY-ESO-1).

RESULTS

Melanoma differentiation antigens, gp100, Melan-A/MART1 and tyrosinase, were expressed in >75% of tumour cells in all uveal and conjunctival melanomas tested. Expression of all five CT antigens tested was low in uveal melanomas, and when present, stained <25% of the tumour cells. MAGE-A1, MAGE-A4 and NY-ESO-1 were expressed in <10% of tumour cells in conjunctival melanomas, while MAGE-C1 and MAGE-A3/6 were expressed in ∼20% and ∼35% of tumour cells in this malignancy, respectively, with variable expression levels.

CONCLUSIONS

Uveal and conjunctival melanomas consistently expressed high levels of the differentiation antigens (gp100, Melan-A/MART1 and tyrosinase). However, compared with other tumours, including cutaneous melanoma, only low levels of CT antigens were found in ocular melanomas. These observations suggest that immunotherapy directly targeting the CT antigens studied may not be effective for ocular melanoma.