Hsp27 (HSPB1) differential expression in normal salivary glands and pleomorphic adenomas and association with an increased Bcl2/Bax ratio.

Pleomorphic adenoma (PA) is the most common salivary gland neoplasm. The Hsp27 (HSPB1) is an antiapoptotic protein whose synthesis follows cytotoxic stresses and result in a transient increase in tolerance to subsequent cell injury. Although Hsp27 is expressed in a range of normal tissues and neoplasms, a wide variation in its expression exists among different cells and tissues types. In certain tumours of glandular origin (such as oesophageal adenocarcinomas), the level of Hsp27 is decreased. In the present study, Hsp27 protein levels were evaluated by enzyme-linked immunosorbent assay (ELISA) in a set of 18 fresh PA and 12 normal salivary gland samples. In addition, we tested if Hsp27 protein levels correlated with p53 expression and cell proliferation index, as well as with the transcriptional levels of Bcl-2-associated X protein (BAX), B cell lymphoma 2 (BCL2) and Caspase 3 in PA. We further tested the association between Hsp27 expression and PA tumour size. While all normal salivary gland samples expressed Hsp27 protein, only half of the PA samples expressed it, resulting in a reduced expression of Hsp27 in PA when compared with normal salivary glands (P = 0.003). The expression levels of this protein correlated positively with a higher messenger ribonucleic acid (mRNA) ratio of Bcl2/Bax (R = 0.631; P = 0.01). In conclusion, a decreased Hsp27 protein expression level in PA was found. In addition, Hsp27 levels correlated positively with the Bcl2/Bax mRNA ratio, suggesting an antiapoptotic effect.