(1) Total poly(A)-containing RNA isolated from human thyroid medullary carcinoma tissue was shown to direct the synthesis in the wheat germ cell-free system of a major (Mr 21000) and several minor forms of human calcitonin precursor polyproteins.
C cell hyperplasia and occult medullary carcinoma of the thyroid in asymptomatic individuals at genetic risk can be detected by measurement of serum calcitonin concentrations before and after stimulation with a secretagogue.
These findings indicate the need for early diagnosis of MEN 2b and the importance of thyroidectomy at the earliest possible age when MTC is suspected by calcitonin screening tests.
The syndrome of multiple endocrine neoplasia (MEN or MEA) type 2b is characterized by the association of medullary carcinoma of the thyroid, phaeochromocytoma, ganglioneuromatosis and Marfan-like features.
It is suggested that this change is related to the different diagnostic approach predominant in each period of time and that MTCs discovered at a preclinical stage by calcitonin screening are equally distributed between the sexes, while females predominate when tumours have progressed until they are clinically evident.
Thorough family studies that used the radioimmunoassay procedure for calcitonin (CT) during the past 12 years have provided data on 70 patients from 12 kindreds with hereditary medullary thyroid cancer (hereditary group) and 28 patients with sporadic or nonhereditary medullary thyroid cancer (sporadic group).
mRNA isolated from medullary carcinoma of the thyroid (MTC) in six patients with the inherited multiple endocrine neoplasia syndrome type 2 and cervical metastases in two patients with sporadic MTC was screened for the presence of calcitonin and proopiomelanocortin (POMC) related sequences by blot hybridization analysis.
In conclusion, 1) hybridization and nucleotide sequence analyses demonstrate that the POMC gene is expressed in MTC metastases; 2) the observed length difference between MTC and pituitary mRNAs suggests differences in expression or processing; 3) no expression of the POMC gene was found in six primary tumors.
This latter observation suggested that neither the stress of the infusion nor the multiple endocrine neoplasia type 2 nor the pentagastrin was responsible for the observed increase in plasma PRL levels in the active MTC patients.
Studies using antisera raised against CGRP and calcitonin, demonstrate elevated circulating levels of plasma CGRP in medullary thyroid carcinoma which do not parallel calcitonin levels, and the presence of CGRP in secretions from lung tumour cell-lines.
In 5 siblings of medullary thyroid carcinoma patients, PDN-21 and calcitonin were increased in response to iv pentagastrin, and we suspect C-cell hyperplasia or medullary thyroid carcinoma.
Dexamethasone differentially affects the levels of calcitonin and calcitonin gene-related peptide mRNAs expressed in a human medullary thyroid carcinoma cell line.
In this report we characterize SRIF production by the TT cells, a line of transformed calcitonin-producing cells derived from a human medullary thyroid carcinoma.
Hybridization histochemistry is likely to be of use in diagnosis of medullary thyroid cancer and in studying the calcitonin-CGRP mRNA processing mechanism in whole cells.
Expression of the calcitonin (CT)/calcitonin gene related peptide (CGRP) gene and the proopiomelanocortin (POMC) gene has been demonstrated by Northern blot hybridization analysis of RNA extracted from human medullary thyroid carcinoma (MTC), pheochromocytoma and lung carcinoma.
Cloning and nucleotide sequence analysis of the human calcitonin mRNA from the BEN lung carcinoma cell line, a cell line known to secrete high-Mr forms of calcitonin, showed no difference in the coding region at the nucleotide level compared with calcitonin mRNA isolated from medullary thyroid carcinoma which secretes calcitonin monomer.
The alternative RNA processing pathways in human calcitonin gene (CALC-I gene) expression were investigated using steady state RNA isolated from human medullary thyroid carcinoma (MTC) and from a culture line derived from this tumor.