STRESS-RESPONSE PROTEINS IN HUMAN PITUITARY-ADENOMAS - EXPRESSION OF HEAT-SHOCK PROTEIN-72 (HSP-72)

The presence of heat-shock protein 72 (HSP-72) was investigated by imm unohistochemistry (IHC) in a series of 28 surgically removed pituitary adenomas including six somatotroph, two mammosomatotroph, five lactot roph, six corticotroph, four null cell adenomas, and three oncocytomas . Overall, 25 tumors (90%) were positive for HSP-72. One somatotroph, one lactotroph, and one null cell adenomas each contained only sparse, small HSP-72 immunoreactive granules and were regarded as negative. T he expression of HSP-72 was commonly uneven differing in degree from c ell to cell and among various tumors. In most adenomas, the immunoreac tivity was seen as fine granules of moderate density, distributed thro ughout the cytoplasm. In some cells, the immunoreactivity was strong a nd diffuse. In one somatotroph, two corticotroph, one null cell, and o ne oncocytic adenomas, nearly all tumor cells were strongly positive. Adenoma cells, located adjacent to capillaries and small vessels, comm only showed a selective and strong immunoreactivity for HSP-72. The fr agments of nontumorous adenohypophysial parenchyma also contained fine immunoreactive cytoplasmic granules accumulating in scattered hormone -producing cells and in stellate cells. These results show that HSP-72 is expressed in most pituitary adenomas with a mostly focal and less frequently diffuse pattern of overexpression.