Cathepsin K: The association between Cathepsin K expression and sphenoid sinus invasion of pituitary adenomas

Pituitary adenomas with sphenoid sinus or clivus invasion are not uncommon, but the pathogenesis responsible for this phenomenon remains unclear. Cathepsin K, expressed predominantly in osteoclasts, can degrade type I collagen and plays an essential role in bone resorption. Recent studies reported the expression of Cathepsin K in various malignant tumors, such as bone, breast, lung and prostate cancers, and its expression is further increased in bone metastasis or invasive subpopulations. In addition, cathepsin K inhibitors (CatKi) were demonstrated to effectively prevent or reduce osteolytic lesions in breast cancers with bone metastasis. In comparable to bone metastasis of breast carcinomas, pituitary adenomas with sphenoid sinus or clivus invasion lead to osteolytic lesions. However, the role of Cathepsin K in sphenoid sinus or clivus invasion of pituitary adenomas has not been identified. Therefore, we presume that Cathepsin K may have a great importance in sphenoid sinus or clivus invasion and CatKi are promising potential therapy for the suppression or prevention of sphenoid sinus or clivus invasion of pituitary adenomas.