Expression of the Anti-Apoptotic Protein BAG3 in Human Melanomas.

The identification of molecules that are involved in maintaining melanoma cell survival is required for a better understanding of melanoma biology (Smalley, 2010) and identification of potential markers for prediction of tumor recurrence and response to therapy (Gould Rothberg and Rimm, 2010). Recent evidence assigns to BAG3 protein, a member of the family of heat-shock protein (HSP) 70 co-chaperones that share BAG domain, a prosurvival role in some tumor types (Rosati et al., 2007). In an in vivo model of human melanoma xenograft in nude mice, we recently showed that BAG3 interferes with the HSP70-mediated delivery of the kappa B kinase (IKK)-γ subunit of IKK complex to proteasome, thereby sustaining NF-κB activation and inhibiting cell apoptosis; bag3 silencing resulted in a significant reduction in tumor growth and prolonged animal survival (Ammirante et al., 2010). Those results prompted us to investigate BAG3 expression in primary melanomas, in order to verify whether this protein contributes to melanoma biology and might constitute a possible prognostic marker and/or a potential target for therapy. We examined BAG3 levels in human melanomas from skin or eye, compared with the corresponding normal tissues, by immunohistochemistry. We analyzed 16 samples of normal skin and 11 samples of normal eye tissues. In parallel, we analyzed 62 samples of skin melanomas and 13 samples of eye melanomas (10 from ciliary body and 3 from choroid lesions). To evaluate BAG3 positivity in cancer tissue samples, we first chose for each sample at least five hotspots by observation with a × 100 magnification. At least 10 nonoverlapping fields were analyzed at × 400 magnification for each hotspot and results were expressed as percentage of positive cancer cells. The median percentage of BAG3 positivity calculated as described was 10%, and this value was used as cutoff. BAG3 low positivity was assigned to samples with 10% of BAG3-positive cells, whereas samples with >10% of BAG3-positive cells were grouped as BAG3 high positiv