Analysis of TGF-beta type I receptor for mutations and polymorphisms in head and neck cancers.

Transforming growth factor-beta receptor (TbetaR)-dependent signals are critical for cell growth and differentiation and are often disrupted during tumorigenesis. The entire coding region of TbetaR-I and flanking intron sequences from 30 head and neck carcinomas were examined for alterations using "Cold" SSCP and direct sequencing. No somatic point mutations were found in the TbetaR-I gene. In contrast, 14 polymorphic sequence changes were detected in TbetaR-I in 13 (43%) of the samples, including eight (27%) nucleotide alterations identified as polymorphisms in an exon-1 (GCG)(9) microsatellite repeat, a previously reported tumor susceptibility allele. A nine base pair deletion was found in 23% of the samples including five heterozygous and two homozygous deletions as well as single homozygous 12bp deletion. Additionally, six heterozygous polymorphisms in intronic sequences were determined, including one heterozygous C/A genotype at the +82 nucleotide position of the intron-5 intervening sequence (IVS), and five heterozygous G/A genotypes within intron-7 at the +24 nucleotide position. Exon-1 polymorphisms in the (GCG)(9) microsatellite region of the TbetaR-I gene and their association with head/neck cancers, suggest that development of these cancers may be a direct consequence of loss of responsiveness to TGF-beta mediated growth inhibition.

Mutational analysis of the transforming growth factor beta receptor type II gene in human ovarian carcinoma.

In the present study, we evaluated a series of sporadic ovarian carcinomas for mutations within the entire coding region of TbetaR-II. Using reverse transcription-PCR and "Cold" single-strand conformational polymorphism analysis, 6 of 24 samples (25%) were found to contain code-altering mutations in TbetaR-II: (a) four mutations resulting in amino acid substitutions in the highly conserved serine/threonine kinase domain; (b) one mutation resulting in a conservative amino acid change in the transmembrane domain; and (c) a 1-bp insertion in the polyadenylic acid microsatellite region resulting in a reading frameshift. In addition, six cases (25%) exhibited a common bp substitution (C-->T at nucleotide 1322) in both tumor and patient-matched normal tissues. This is the first report of such TbetaR-II mutations in primary human ovarian carcinomas. Immunohistochemical analysis demonstrated a loss of expression of TbetaR-II in 5 of 22 available tumors (23%; 4 of which also had mutations in the coding region) and decreased expression of TbetaR-II in 10 of 22 available tumors (44%; 1 of which had a mutation in the coding region). Thus, the loss or decreased expression of TbetaR-II seems to be a common event in sporadic ovarian carcinomas, and mutational inactivation, due to either frameshift mutations in the polyadenylic acid microsatellite region or point mutations in conserved functional domains, is one mechanism by which this occurs.

Angiotensin II promotes prolactin release from normal human anterior pituitary cell cultures in a calcium-dependent manner.

Renin and angiotensin II (AII) have been demonstrated in the mammalian central nervous system, and AII has been found to promote PRL release in the rat and monkey. We added AII to monolayer cultures of human anterior pituitary cells and found significant PRL release by 30 min with concentrations of AII as low as 10(-10) M. This AII-induced PRL release was inhibited by the specific AII antagonist saralasin. AII-induced PRL release was a calcium-dependent process, since the calcium channel blockers verapamil and nifedipine as well as the calcium-calmodulin antagonist R2471 significantly inhibited AII-induced PRL release. Prostaglandins E2, A2, and F2 alpha also inhibited AII-induced PRL release. The significance of this latter observation is not clear, however, as indomethacin, an inhibitor of the cyclo-oxygenase prostaglandin metabolic pathway, had no effect on AII-induced PRL release. In light of recent immunohistochemical evidence of the presence of renin, angiotensinogen, and converting enzyme in human lactotrophs, our data support the concept that AII may be an important autocrine regulator of PRL secretion.