Immunohistochemical expression of Cathepsin H protein in Glioblastoma Multiforme: Diverse subcellular localization patterns suggest a complex role in the biology of these tumors

Patients diagnosed with Glioblastoma Multiforme (GBM) usually survive less than a year, even with the latest treatment protocols, thus there is an urgent requirement for identifying molecular markers that could be utilized for targeted therapy. The lysosomal proteases are believed to contribute to the invasive process of tumors by breakdown of extracellular matrix. Cathepsin H is a lysosomal protease whose expression has not been fully characterized in GBM. We examined the pattern of CH protein expression immunohistochemically in 24 GBM, 18 other brain tumors and 3 non-tumor cases. CH was expressed in all cases of GBM, although there was considerable heterogeneity within each tumor. Several patterns of CH expression were observed including granular and diffuse cytoplasmic staining. The diversity in CH expression patterns in GBM indicates a complex role for CH in the biology of these tumors, and warrants further investigation for developing a novel molecular target for therapy.