Ectopic synthesis of high‐M_r calcitonin by the BEN lung carcinoma cell line reflects aberrant proteolytic processing

Abstract

Cloning and nucleeotide sequence analysis of the human cakitanin mRNA From the BEN hmg carcinoma cell line, a ceB fine known to secrete high-Mr forms of cakitonin, showed no difference in the coding region at the nucleotide level compared with calcitonin mRNA isolated from medullary thyroid carcinoma which secretes calcitonin monomer. Therefore, the secretion of high-M, forms of calcitonin reflects the absence or limited activity of proteolytic processing enzymes within the secretory pathway of this cell line. in ail other respects, as judged by RNA blatting and S, mapping, calcitonln/a-CGRP expression was identical to that found in medullary thyroid carcinoma, including the differential use of an alternative splice donor site within intron 1. The BEN cell line also produces low levels of a-CGRP mRNA and secretes CGRP antigenic determinants. Analysis of plasma CGRP levels in 12 patients with anaplastic lung carcinoma showed elevated levels in 11 of these, suggesting that CGRP may be an important diagnostic marker for this disease. Lusg carcinoma ~edu~~~ry thy&d c~c~noma ~roteo~ytic pr~e~~~g RNA ~p~ic~~gCalcitonin gem-related peptic &topic synt~~~~

Elevated Serum Levels of Calcitonin Gene‐related Peptide (Cgrp) but No Evidence for CGRP Gene Expression in Non‐small Cell Lung Carcinomas

“…The results are consistent with a previous report showing increased circulating CGRP levels in lung carcinomas (Riley et al, 1986). However, it is surprising that extensive examination of tumour tissue from the same patients has failed to reveal evidence for the expression of CGRP at the peptide or mRNA level as judged by immunocytochemistry and in-situ hybridization.…”

“…Some of the CGRP-positive nerve fibres are found adjacent to small and medium-sized arteries of the respiratory tract (Polak & Bloom, 1985;Ghatei et al, 1987;Lauweryns & Ranst, 1987) and may be involved in the regulation of regional blood flow (Uddman et al, 1985(Uddman et al, , 1986Keith & Ekman, 1988). CGRP has been found in secretions from lung cancer cell lines (Nelkin et al, 1984;Craig er al., 1985;Riley et al, 1986) and has been shown to be present in elevated amounts in plasma from patients with anaplastic lung carcinomas (Riley et al, 1986). Therefore, in order to determine whether CGRP might prove to be a useful marker for non-small cell lung carcinomas we have compared the pre and post-operative serum concentrations of CGRP in 22 patients operated for various pulmonary tumours.…”

Structural characterization of a high-molecular-mass form of calcitonin [procalcitonin-(60–116)-peptide] and its corresponding N-terminal flanking peptide [procalcitonin-(1–57)-peptide] in a human medullary thyroid carcinoma

“…The complete amino acid sequences of procalcitonin-(1-36)-peptide, procalcitonin-(37-57)-peptide and procalcitonin-(60-116)-peptide were obtained with the exception that no amino acid phenylthiohydantoin derivative corresponding to homoserine lactone was observed at cycle 36 of the Edman degradation of procalcitonin-(1-36)-peptide. The primary structures of the peptides are identical with the structures predicted from the nucleotide sequences of cloned cDNAs from human tumours of the thyroid (Le Moullec et al, 1984) and lung (Riley et al, 1986 …”

“…The primary structure of the biosynthetic precursor of human calcitonin (preprocalcitonin) may be deduced from the nucleotide sequence of cDNA clones isolated from medullary thyroid carcinoma tissue (Craig et al, 1982;Le Moullec et al, 1984) and from a bronchial carcinoma cell line (Riley et al, 1986). Human preprocalcitonin is a protein comprising 141 amino acid residues in which the calcitonin sequence is flanked at its C-terminus by a 21-residue peptide termed katacalcin or PDN-21.…”

Loss of transcriptional repression contributes to the ectopic expression of the calcitonin/α‐CGRP gene in a human lung carcinoma cell line

“…BEN cells were cultured in g-MEM ~upplementgd with 10% FCS as previously described [10]. HeLa cells vcere grown in DMEM supplemented with 10% FCS in the same way.…”