Bim expression is reduced in human cutaneous melanomas

Bim is a BH3-only protein belonging to the Bcl-2 family of apoptotic regulators. Upon activation, Bim can antagonize all the prosurvival Bcl-2 proteins, leading to apoptosis. To investigate whether Bim plays a role in melanoma progression, we used tissue microarray and immunohistochemistry to measure Bim expression in 52 cases of dysplastic nevi, 159 cases of primary melanomas and 52 cases of melanoma metastases, and evaluated the prognostic value of Bim expression. Our results showed that Bim expression is reduced as melanoma progresses. Significant differences for Bim staining pattern were observed between dysplastic nevi and metastatic melanomas (P < 0.001, chi(2) test), and between primary melanomas and metastatic melanomas (P < 0.001, chi(2) test). Moreover, reduced Bim expression is significantly correlated with poor 5-year survival of melanoma patients but failed to be an independent prognostic factor by Cox regression analysis. Our data suggest that Bim loss may play an important role in melanoma progression.