Role of tyrosine kinase inhibitors in the treatment of pituitary tumours: from bench to bedside.

Abstract

Treatment of aggressive pituitary tumours often yields suboptimal control of the tumour and confers significant morbidity. Lactotroph and corticotroph-derived tumours express ErbB receptors and ligands, and mutations in ubiquitin-specific protease 8 (USP8), which alters epidermal growth factor receptor (EGFR) degradation, have been implicated in Cushing disease pathogenesis. EGFR tyrosine kinase inhibitor (TKI) therapy has emerged as a potential new therapeutic approach for patients with aggressive prolactinomas and Cushing disease. Using EGFR or human epidermal growth factor receptor 2-driven prolactin (PRL) promoters, transgenic mice develop large tumours that respond to TKI inhibition. In human corticotroph primary cultures, treatment with the pan-ErbB TKI canertinib as well as the EGFR TKI gefitinib suppresses proopiomelanocortin mRNA. USP8 mutations, detected in up to two-thirds of Cushing disease, may underlie the increase in EGFR signalling in these tumours. Human prolactinomas have differential ErbB receptor expression associated with aggressive behaviour and data from an ongoing clinical trial suggest that resistant prolactinomas may respond to the EGFR TKI lapatinib. Preclinical and clinical models substantiate the role of the EGFR pathway in corticotroph and lactotroph adenomas. Although further study is needed, results to date suggest that targeting the ErbB pathway may be an effective therapeutic approach for patients with aggressive pituitary tumours.