Expression of Bcl-2 family members in malignant pleural mesothelioma

Little is known about the Bcl-2 family members in mesothelioma. These proteins are involved in the control of apoptosis, carrying out both pro- and anti-apoptotic functions. Immunohistochemistry was used to examine the expression of p53 and Bcl-2 family members in 54 archival mesothelioma samples ( 39 epithelial, 15 sarcomatoid tumours). Overexpression of p53 was observed in 81% ( 44/54). For anti-apoptotic proteins, overexpression was recorded as follows: Bcl-2 40% ( 22/54), Bcl-X-L 24% ( 13/54), Mcl-1 92% ( 50/54). For pro- apoptotic proteins, loss of expression was recorded as follows: Bad 25% ( 14/54), Bak 24% ( 13/54), Bax 42% ( 23/54), Bid 37% ( 20/54), Bim 18% ( 10/54). Statistically significant differences between epithelial and sarcomatoid tumours were observed for Bid ( p < 0.001), Bad ( p = 0.012) and Bcl-X-L ( p = 0.03). Significant differences in abnormal expression of apoptosis proteins were found between epithelial and sarcomatoid subtypes but histological subtype was the only factor with significant association to patient prognosis.