Apart from the constitutively activating mutation of the G-protein alpha subunit (Gsα) (gsp mutation), factors involved in tumorigenesis or those in tumour behaviour remain elusive in sporadic GH-secreting pituitary adenomas. Recently, the N-terminally truncated form of fibroblast growth factor receptor-4 (ptd-FGFR4) was identified in pituitary adenomas. This aberrant receptor has transforming activity, and causes pituitary adenomas in transgenic mice. The clinical relevance of this receptor warrants investigation. Our objective was twofold: first, to examine how the expression of ptd-FGFR4 relates to gsp mutations; and second, to see whether patients with this receptor have unique clinical characteristics.Materials and methods
mRNA was extracted from excised adenomas of 45 Japanese acromegalic patients. ptd-FGFR4 expression and gsp mutations were determined by reverse transcription polymerase chain reaction (RT-PCR) and direct sequencing. Preoperative clinical data were collected by reviewing medical charts and pituitary magnetic resonance imaging (MRI) scans.Results
ptd-FGFR4 mRNA expression was detected in 19 out of 45 tumours (42·2%) while gsp mutations were detected in 25 out of 45 tumours (55·6%). The prevalence of ptd-FGFR4 expression did not differ between gsp-positive (44·0%) and gsp-negative (40·0%) tumours (P = 1·00). ptd-FGFR4-positive tumours invaded the cavernous sinus more frequently (P = 0·0098) than did the ptd-FGFR4-negative tumours. Tumour size was not statistically different between ptd-FGFR4-positive and -negative tumours (P = 0·198). The presence of ptd-FGFR4 did not correlate with age at operation, sex, preoperative serum GH or IGF-1 levels.Conclusions
We found that ptd-FGFR4 expression and gsp mutations occur independently of each other, and that ptd-FGFR4 expression is associated with more invasive tumours in patients with GH-secreting pituitary adenomas.