The association is either a chance occurrence or due to the induction of lymphoma cell proliferation by the binding of FSH produced by the adenoma to the FSH receptors on the lymphoma cells.
LHb and FSHb genes showed the highest expression, respectively, in LH-producing and FSH-producing pituitary adenomas; however, our analysis did not show statistically significant differences between LH-producing and FSH-producing adenomas.
The methylation status of the p18(INK4C) gene promoter and somatic mutations of the p18(INK4C) gene were also investigated. p18(INK4C) protein expression was lost or significantly reduced in 64% of pituitary adenomas compared with levels in normal pituitary glands. p18(INK4C) mRNA levels were low in all ACTH adenomas and non-functioning (NF)-FSH and in 42%, 70% and 66% of GH, PRL, and subtype 3 adenomas, respectively. p18(INK4C) mRNA levels were significantly associated with p18(INK4C) protein levels.
The signals for hormone production were detected in both adenoma types in a range from 42% for GH in oncocytomas to 78% for beta-FSH in null cell adenomas.
In vitro leptin stimulation of pituitary tumours caused stimulation of FSH and alpha-subunit secretion from a non-functioning adenoma and TSH secretion from a somatotroph adenoma.
ISH detected signals for all pituitary hormones at a range of 30% for prolactin (PRL) to 85% for proopiomelanocortin (POMC). mRNA for beta-FSH was detected in 70% and beta-LH mRNA in 43% of adenomas.
In all cases, immunocytochemical studies of the removed adenoma confirmed their gonadotroph nature by revealing positivity for FSH, LH and/or alpha-subunit.
Gonadotroph (LH/FSH) and null cell adenomas had significantly higher levels of particulate, soluble, and total PKC activity compared with growth hormone (GH) adenomas (P < 0.05).
We studied the effects of GnRH, CRF, dexamethasone, and phorbol 12-myristate 13-acetate on FSH and LH secretion and on FSH beta and chromogranin-A and -B mRNA expression in 10 chromogranin-A-positive adenomas in vitro to analyze the regulation of FSH and chromogranin-A and -B expression in these neoplasms.