Calcitonin gene-related peptide in small cell lung carcinomas

Expression of the Calcitonin Receptor-like Receptor (CALCRL) in Normal and Neoplastic Tissues

Little information is available concerning protein expression of the calcitonin receptor-like receptor (CALCRL) at the protein level. Here, we developed a rabbit monoclonal antibody, 8H9L8, which is directed against human CALCRL but cross-reacts with the rat and mouse forms of the receptor. We confirmed antibody specificity via Western blot analyses and immunocytochemistry using the CALCRL-expressing neuroendocrine tumour cell line BON-1 and a CALCRL-specific small interfering RNA (siRNA). We then used the antibody for immunohistochemical analyses of various formalin-fixed, paraffin-embedded specimens of normal and neoplastic tissues. In nearly all tissue specimens examined, CALCRL expression was detected in the capillary endothelium, smooth muscles of the arterioles and arteries, and immune cells. Analyses of normal human, rat, and mouse tissues revealed that CALCRL was primarily present in distinct cell populations in the cerebral cortex; pituitary; dorsal root ganglia; epithelia, muscles, and glands of the larger bronchi; intestinal mucosa (particularly in enteroendocrine cells); intestinal ganglia; exocrine and endocrine pancreas; arteries, capillaries, and glomerular capillary loops in the kidneys; the adrenals; Leydig cells in the testicles; and syncytiotrophoblasts in the placenta. In the neoplastic tissues, CALCRL was predominantly expressed in thyroid carcinomas, parathyroid adenomas, small-cell lung cancers, large-cell neuroendocrine carcinomas of the lung, pancreatic neuroendocrine neoplasms, renal clear-cell carcinomas, pheochromocytomas, lymphomas, and melanomas. In these tumours with strong expression of CALCRL, the receptor may represent a useful target structure for future therapies.

Circulating markers for endocrine tumours of the gastroenteropancreatic tract

The diffuse endocrine system (DES) includes a wide range of secretory cells that may be the source of tumours. Gastroenteropancreatic endocrine (GEP) tumours arising within the DES secrete a variety of peptides and amines that are found in the circulation and are responsible for the syndromes associated with these tumours. In this review, the most common tumours of the GEP tract are outlined and the circulating products of these tumours identified. Where differential diagnosis is difficult these points are addressed. The peptides most commonly secreted by GEP neuroendocrine tumours are identified and described and their biological activities are discussed. Current methods available for measurement of these peptides are described. Attention is drawn towards molecular specificity where appropriate, as many pancreatic and gut peptides fall within families which show considerable homology, such as the tachykinin family or the glucagon family. Other peptides such as gastrin circulate in multiple molecular forms. This homology and diversity may cause difficulty in the interpretation of peptide measurements in the clinical situation if assays are not specific.

Establishment and characterization of murine small cell lung carcinoma cell lines derived from HPV-16 E6/E7 transgenic mice

We have established two murine cell lines derived from Small Cell Lung Carcinomas (SCLCs) developed by HPV-E6/E7 transgenic mice. These cells named PPAP-9 and PPAP-10 were isolated from mice bearing tumors, 9 and 10 months old, respectively. The cells, 5 microm in diameter, express HPV oncoproteins and sustain tumor formation after subcutaneous injection in syngenic mice. A detailed analysis indicated the epithelial origin and the neuroendocrine differentiation of these cells. We showed by confocal immunofluorescence the expression of the epithelial marker cytokeratin 5, whose gene promoter was used to direct the expression of HPV E6/E. Cells express several neuroendocrine markers such as CGRP, MAP-2, Ash1, CgrA, Scg2. The neuroendocrine differentiation of these cells was further confirmed by electron microscopy demonstrating neuropeptides secreting granules in their cytoplasm. Furthermore, in agreement with the altered expression observed in the majority of human SCLC we showed in these cells the absence of both p53 and pRB and a dramatic reduction in the expression of Caveolin-1.

Small cell lung carcinoma cell lines express mRNA for calcitonin and alpha- and beta-calcitonin gene related peptides

Calcitonin (CT) and calcitonin gene related peptide (CGRP) are derived from preprohormones encoded by three mRNAs (CT, alpha-CGRP and beta-CGRP) from two genes (CALC1 and CALC2) on chromosome 11. Among 16 small cell lung cancer cell lines examined by RNase protection assay, 9 (56%) had detectable CT mRNA, 8 (50%) had alpha-CGRP mRNA, and 13 (81%) had beta-CGRP mRNA. At least one CALC1 transcript (CT or alpha-CGRP) was found in 11 (69%) cell lines with three having only CT mRNA, two having only alpha-CGRP mRNA, and six having both. beta-CGRP mRNA was detected in all of these 11 cell lines expressing a CALC1 transcript. Immunoreactive CT was detected by radioimmunoassay in eight of nine SCLC cell lines expressing CT mRNA, and immunoreactive CGRP was detected in 12 of 13 cell lines expressing a CGRP mRNA. The variety of expression of these three peptides in different cell lines of the same cell type should provide a useful system for further study of the control of expression of these peptides.

Calcitonin gene-related peptide in medullary thyroid carcinomas: characterization of molecular forms including the amidated C-terminus

CGRP was extracted from three familial and four sporadic medullary thyroid carcinomas (MTC) and was measured by an assay specific for the amidated C-terminus. The antibody showed equal affinity for alpha- and beta-CGRP. All tumors contained high concentrations of CGRP (range: 63-7889 pmol/g) compared to spinal cord (86 pmol/g), thyroid gland (4 pmol/g), and two small-cell lung carcinomas (4 and 1 pmol/g, respectively). The concentration of calcitonin (CT) was determined with an assay specific for an epitope involving the midportion and C-terminal end of the molecule. In six of the seven tumors investigated, concentrations of CT were found to be higher than for CGRP. Gel chromatography showed heterogeneity with respect to CGRP immunoreactivity. Thus, in all seven extracts, three peaks were seen with Kd values 0.37, 0.63, and 0.80, respectively. This profile of immunoreactive CGRP was similar to that obtained from human medulla spinalis, thereby indicating normal posttranslational processing of pro-CGRP in MTC tumors. Further characterization of the three main peaks identified by gel chromatography was performed on pooled fractions from one of the tumors using HPLC, sequencing, and mass spectrometry. The immunoreactive peak with Kd 0.37 was identified as human beta-CGRP, the peak with Kd 0.63 as 19-37 beta-CGRP, and the peak with Kd 0.80 as 25-37 beta-CGRP. No alpha-CGRP was identified in this tumor. This indicates selective expression of beta-CGRP, at least in the tumor investigated.