Human lung small-cell carcinoma contains bombesin

Circulating progastrin-releasing peptide in the diagnosis of Small Cell Lung Cancer (SCLC) and in therapeutic monitoring

Introduction:

Progastrin-releasing peptide (proGRP), a precursor of GRP, has been recently reported as a putative circulating biomarker for differential diagnosis between non–small cell lung cancer (NSCLC) and SCLC. We evaluated the diagnostic effectiveness of proGRP to differentiate patients with NSCLC and SCLC and the usefulness of combined measurement of proGRP and neuron-specific enolase (NSE) for diagnosing SCLC.

Methods:

Serum proGRP, NSE, cytokeratin 19 fragment 21-1 (CYFRA 21.1), squamous cell carcinoma antigen (SCC Ag) and carcinoembryonic antigen (CEA) were prospectively collected and measured in patients with a new diagnosis of lung cancer. Serum proGRP was also measured in healthy subjects. The serum proGRP, NSE, CYFRA 21.1 and CEA concentrations were determined by an electrochemiluminescence immunoassay and the serum SCC Ag concentration was determined by an automated immunofluorescence assay. Differences between proGRP and NSE in patients with SCLC and NSCLC were evaluated and compared using Mann-Whitney test.

Results:

A total of 77 patients affected by SCLC (n = 17) and NSCLC (n = 60) were enrolled in the present study. Moreover, 50 cases of healthy subjects were analyzed for proGRP. SCLC patients showed a significantly higher proGRP (1,484 pg/mL; range 168-3,777) levels compared to NSCLC patients (45 pg/mL; range 31.7-60.6), p<0.0001. In healthy subjects the median proGRP level was 36.1 (28.8-43.5) pg/mL, significantly lower than SCLC patients. ProGRP showed a higher specificity when compared to NSE, with a difference in proportion of 47.5% (95% confidence interval 32.5% to 62.5%, p<0.001). Serial measurements of proGRP in SCLC patients showed a decrease in responsive chemotherapy patients.

Conclusions:

ProGRP is an accurate biomarker for diagnosis of SCLC and for discrimination of SCLC from NSCLC.

New and old biomarkers in the differential diagnosis of lung cancer: Pro-gastrin-releasing peptide in comparison with neuron-specific enolase, carcinoembryonic antigen, and CYFRA 21-1

BACKGROUND

Testing for circulating biomarkers in lung cancer is hampered by the insufficient specificity. We aimed to assess the relative diagnostic accuracy of pro-gastrin-releasing peptide (ProGRP) for the differential diagnosis of small cell lung cancer and compare it with more conventional biomarkers.

METHODS

We enrolled a cohort of 390 patients with a clinical suspicion of lung cancer and for whom a histologic assessment was available. Serum or plasma samples were assessed for ProGRP, carcinoembryonic antigen, CYFRA 21-2, and neuron-specific enolase. The performance of each biomarker in discriminating the small cell lung cancer and squamous cell carcinoma/adenocarcinoma from non-malignant lung disease, and small cell lung cancer from squamous cell carcinoma/adenocarcinoma, was assayed by receiver operating characteristic curve analysis.

RESULTS

At the cut-off levels suggested by the manufacturers, ProGRP and neuron-specific enolase showed an almost identical sensitivity of 55.2% and 55.6%, respectively, in discriminating small cell lung cancer with respect to non-malignant lung disease. In order to quantify the added value of ProGRP to other conventional markers, we ran a multivariable logistic regression analysis, but the results showed that no markers improve the performance of ProGRP.

CONCLUSIONS

ProGRP and neuron-specific enolase individually appear more accurate than other conventional biomarkers for small cell lung cancer, but the union of two markers does not increase the accuracy. The very small target group of patients with small cell lung cancer is a limitation of this study, which can explain why ProGRP alone does not show a sensitivity higher than neuron-specific enolase, as reported by other authors.

Diagnostic and therapeutic value of progastrin-releasing peptide on small-cell lung cancer: A Single-Center Experience in China

We aimed to compare the diagnostic efficiency of proGRP and NSE on SCLC and to investigate whether the change of proGRP level would predict therapeutic response. Patients who were firstly diagnosed pathologically in Nanjing Chest Hospital and measured proGRP level consecutively were enrolled in the study. ProGRP level was detected using Elecsys ProGRP Assay. Totally 75 SCLC, 234 NSCLC and 264 benign lung diseases (BLD) were enrolled. Both proGRP and NSE levels in SCLC were significantly higher than those in NSCLC and BLD, and proGRP in extensive stage SCLC was higher than which in limited stage (P ≤ .001). The diagnostic efficiency of proGRP on SCLC was higher than that of NSE, but when the two biomarkers were bind together, the diagnostic efficiency was the best. When SCLC was differentiated from NSCLC and BLD, the cut‐off values were 114.35 pg/mL and 162.55 pg/mL respectively. For treatment responsive patients, proGRP level decreased markedly after the first cycle of therapy and kept a continued momentum of decline during treatment. But for unresponsive patients, no obvious decline was observed. ProGRP had higher diagnostic efficiency on SCLC when compared to NSE, and it could better predict therapeutic response of pulmonary target lesions on chemotherapy.

Production and Characterization of Monoclonal Antibodies for Immunoassay of the Lung Cancer Marker proGRP

Progastrin-releasing peptide (proGRP) is a precursor of gastrin-releasing peptide, a hormone which is secreted from neuroendocrine cells. It has been shown to be a useful serum marker for small cell lung cancer. We raised monoclonal antibodies (MAbs) against proGRP with the primary aim of establishing a sensitive immunoassay. Immunization was performed with recombinant proGRP (amino acids 31-98) conjugated to thyroglobulin or with a DNP-modified peptide. Seven of the MAbs recognizing both recombinant and cell line-derived peptide were characterized and epitope-mapped. Based on cross-inhibition studies the antibodies could be categorized into three main groups. The molecular epitope assignment was studied by using phages displaying proGRP peptides, random peptide libraries displayed on phage and by pepscan analysis utilizing 10-mer biotinylated peptides. Two of the MAbs (E146, E172) bound to a defined region on the N-terminal part of proGRP(31-98), three recognized conformational-dependent epitopes in the middle of the peptide (E179, E180, E181) and two bound to the C-terminal part (E149, E168). Consensus sequences were obtained for MAbs E146, E149 and E168. The binding kinetics of the MAbs was determined by surface plasmon resonance, and a time-resolved immunofluorometric assay was established.

ProGRP: a new biomarker for small cell lung cancer

Progastrin-releasing peptide (ProGRP) is a recently identified biomarker of small cell lung cancer (SCLC), a disorder of neuroendocrine tissue differentiation. The upper normal limit of ProGRP in the circulation is 50 pg/ml. Impaired glomerular filtration tends to increase circulating levels and confound the tumor marker significance of modestly elevated values. Excluding patients with renal failure, circulating levels did not exceed 80 pg/ml in benign disease (3% of cases in excess of the upper normal limit) or 120 pg/ml in malignancy other than lung cancer and neuroendocrine tumors (5% of cases in excess of the upper limit). ProGRP serum levels are clearly related to the lung cancer histological type with significantly higher levels observed in SCLC than in nonsmall cell lung cancer (NSCLC). Circulating ProGRP in excess of 120 mg/ml was found in only 4% of cases of NSCLC with another 22% presenting with modestly elevated levels in excess of the upper normal limit. By contrast, abnormal ProGRP results are found in 60-70% and in 75-90% of SCLC patients with local and extensive disease, respectively. ProGRP is a more sensitive biomarker than is neuron-specific enolase (NSE) for SCLC, but thus far has not been found in multivariate analysis to have independent prognostic significance. Preliminary studies suggest ProGRP will have utility in conjunction with NSE in monitoring the therapy of established SCLC.

Small cell carcinoma of the esophagus; clinicopathological and immunohistochemical analysis of six cases

Small cell carcinoma arising in the esophagus is a relatively rare disease. In the more common small cell carcinoma of the lung, the diagnostic significance of several new markers has been recently reported. This study used immunohistochemical techniques in addition to clinicopathological analysis, in order to clarify the utility of newer markers as biological parameters or as diagnostic tools. Six patients with small cell carcinoma of the esophagus were clinicopathologically analyzed. Immunohistochemical staining was performed using primary antibodies for bombesin, CD56 and CD57 in addition to conventional endocrine markers chromogranin A, neuron specific enolase and synaptophysin. All patients died within 2 years of surgery due to cancer recurrence, whether or not they had received adjuvant therapy. Pathological stages ranged from IIa to IVb and lymph node metastasis was observed in five cases. Of the six cases, four showed a positive reaction for bombesin and five were positive for CD57. In contrast, no cases revealed a positive reaction for CD56. The one case to survive 24 months after surgery was not shown to express bombesin, CD56 or CD57. Small cell carcinoma of the esophagus demonstrated an unfavorable prognosis. The study suggested that in this disease, bombesin and CD57 (but not CD56) were useful as biological markers, predicting clinical outcome rather than having diagnostic significance.

Serum pro-gastrin-releasing peptide (31-98) in benign prostatic hyperplasia and prostatic carcinoma

OBJECTIVES

To clarify whether serum levels of pro-gastrin-releasing peptide (ProGRP) (31-98) could be a useful marker in patients with prostatic carcinoma. GRP is produced and secreted by prostatic neuroendocrine cells.

METHODS

Serum levels of ProGRP(31-98) were measured by enzyme-linked immunosorbent assay in 20 patients with benign prostatic hyperplasia and 107 patients with prostatic carcinoma.

RESULTS

The mean serum levels of ProGRP(31-98) in patients with distant metastasis and hormone-resistant prostate cancer were significantly elevated compared with those in patients with organ-confined disease. Significantly elevated levels of ProGRP(31-98) were detected in 9 patients with prostatic carcinoma before any treatment. During hormone-resistant prostate cancer progression, ProGRP(31-98) levels were elevated in 9 patients (23%). Of the 9 patients with Stage D3 and elevated serum ProGRP, 4 had a normal serum prostate-specific antigen level.

CONCLUSIONS

ProGRP may be a potential tumor marker for prostate cancer. Additional studies in large groups of patients are needed to define the clinical value of ProGRP.

Significance of serum pro-gastrin-releasing peptide as a predictor of relapse of small cell lung cancer: comparative evaluation with neuron-specific enolase and carcinoembryonic antigen

Neuron-specific enolase (NSE) and carcinoembryonic antigen (CEA) have been reported to be useful markers for staging, monitoring treatment, and predicting relapse in patients with small cell lung cancer (SCLC). Recently, pro-gastrin-releasing peptide (Pro-GRP) became available as a sensitive, specific, and reliable tumor marker for patients with SCLC. The aim of this study is to determine the most useful tumor marker to detect the relapse of SCLC. Furthermore, we analyzed the relationship between tumor markers at relapse and survival from relapse or response to salvage chemotherapy. Medical records were reviewed to obtain serum levels of Pro-GRP, NSE, and CEA before and after the initial chemotherapy, and at relapse. Consecutive 66 patients with SCLC, with an objective response and confirmed relapse treated at the National Cancer Center Hospital East, were analyzed in this study. The percentages of patients whose tumor marker level were elevated before treatment, decreased after the treatment, and increased again at relapse were 67% (95% CI, 55-78) for Pro-GRP, 20% (10-29) for NSE, and 38% (26-50) for CEA. Multivariate analysis indicated that poor performance status before initial treatment and elevated serum levels of lactate dehydrogenase at relapse were poor prognostic factors for patients with recurrent SCLC (P<0.005). None of the serum levels of Pro-GRP, NSE, and CEA at relapse was a significant prognostic factor and associated with an objective response to salvage chemotherapy. The present study demonstrated that serum levels of Pro-GRP reflect the disease course of patients with SCLC most accurately.

Correlation of expression of bombesin-like peptides and receptors with growth inhibition by an anti-bombesin antibody in small-cell lung cancer cell lines

The murine anti-bombesin monoclonal antibody, 2A11, has been demonstrated to inhibit growth of some small-cell lung cancer (SCLC) cells in nude mice xenografts and in a clinical trial. To determine if the expression of bombesin-like peptides (BLP) and their receptors (GRP-R and NMB-R) correlate with an in vitro response to 2A11, we measured these parameters in seven SCLC cell lines. Gastrin releasing peptide (GRP) mRNA was detected in three of seven cell lines (NCI-H69, NCI-H345, NCI-H510) and neuromedin B (NMB) mRNA was detected in all seven lines using an RNase protection assay (RPA). Immunoreactive BLP was detected in the cell pellets of all lines (range 0.11-59.90 pmol/mg protein) by a solid phase GRP radioimmunoassay (RIA) using 125I-labeled 2A11. RPA detected GRP-receptor mRNA in two cell lines (NCI-H69 and NCI-H345) and NMB-receptor in three lines (NCI-H345, NCI-H510, and NCI-H660). Reverse transcriptase-PCR confirmed the presence of receptor mRNA in these lines and detected NMB-receptor in an additional three lines (NCI-H69, NCI-H82, and NCI-H187). Calcium mobilization in response to BLP stimulation was detected in the six cell lines expressing either GRP-R or NMB-R mRNA but not in NCI-N417, which had no detectable BLP-receptor. 2A11 (5 microg/ml) inhibited colony formation by 26-61% after 2 weeks in all cell lines except NCI-N417. Thus, growth inhibition by 2A11 requires the presence of at least one BLP-receptor. These findings may be useful in selecting patients with SCLC for treatment with 2A11.

Clinicopathologic characteristics of patients with nonsmall cell lung carcinoma with elevated serum progastrin-releasing peptide levels

BACKGROUND

Progastrin-releasing peptide (proGRP) is a specific tumor marker in patients with small cell lung carcinoma (SCLC). It has been reported that serum proGRP levels rarely are elevated in patients with nonsmall cell lung carcinoma (NSCLC); the reported frequency is <3%. The purpose of this study was to examine the clinicopathologic features of NSCLC patients with high serum proGRP levels.

METHODS

The authors measured serum proGRP levels with a TND-4 kit, a newly developed enzyme-linked immunoadsorbent assay, in 544 NSCLC and 206 SCLC patients. Pathologic features were examined using conventional hematoxylin and eosin staining and histochemical and immunohistochemical staining using polyclonal antibodies to proGRP, chromogranin A, calcitonin, and monoclonal antibody to the neural cell adhesion molecule (NCC-Lu-243).

RESULTS

The serum proGRP levels were elevated in 140 SCLC patients (68.0%) and in 23 NSCLC patients (4.2%). Seven of these 23 NSCLC patients had serum proGRP levels > or = 100 pg/mL. They included two patients with renal dysfunction, one patient diagnosed cytologically with adenocarcinoma without undergoing precise pathologic examination, two patients diagnosed histologically with squamous cell carcinoma with foci of small cell elements, and two patients diagnosed with large cell neuroendocrine carcinoma and poorly differentiated adenocarcinoma, respectively, which showed neuroendocrine differentiation on immunohistologic analysis. The remaining 16 NSCLC patients had serum proGRP levels < 70 pg/mL.

CONCLUSIONS

Nearly all NSCLC patients had serum proGRP levels < 100 pg/mL. However, if an NSCLC patient presents with a proGRP level > or = 100 pg/mL, the clinicopathologic features must be examined with regard to the small cell component, neuroendocrine differentiation, and renal dysfunction.

Functional expression of bombesin receptor in most adult and pediatric human glioblastoma cell lines; role in mitogenesis and in stimulating the mitogen-activated protein kinase pathway

Functional bombesin receptors were identified in most human glioblastoma cell lines examined (approximately 85% of lines). Bombesin stimulated the release of intracellular Ca2+ in human adult (U-373MG, D-247MG, U-118MG, U-251MG, D-245MG, U-105MG, D-54MG, A-172MG, and D-270MG lines) and pediatric (SJ-S6 and SJ-G2 lines) glioblastoma cell lines. Stimulation of the glioblastoma cell line U-373MG with bombesin or gastrin-releasing peptide (GRP) induced mitogenesis, measured by [3H]thymidine incorporation into DNA, and stimulated the tyrosine phosphorylation of the mitogen-activated protein (MAP) kinases (Erk1 and Erk2). The stimulation of the MAP kinase phosphorylation in U-373MG cells was time- and peptide concentration-dependent. Both bombesin and GRP showed similar potencies in stimulation of intracellular Ca2+ release and activation of the MAP kinase pathway in U-373MG cells, whereas neuromedin B (NMB) peptide was less potent. Bombesin and GRP induced the release of cytosolic Ca2+ in a concentration-dependent manner. Because bombesin and GRP were more potent than NMB peptide in increasing the cytosolic Ca2+ levels in U-373MG cells, we concluded that the BB2 subtype (also known as GRP-preferring receptor subtype) of the bombesin receptor is expressed in this cell line. The bombesin receptor antagonist ([Leu13-psi(CH2NH)Leu14]bombesin) blocked bombesin induced Ca2+ release and attenuated MAP kinase activation in U-373MG cells demonstrating that bombesin is acting through a receptor-dependent mechanism. This study indicates that functional bombesin receptors are widely expressed in human glioblastoma cell lines.

Pro-gastrin-releasing peptide (31-98) as a tumour marker of small-cell lung cancer: comparative evaluation with neuron-specific enolase

We attempted to clarify whether serum levels of a carboxy-terminal fragment of ProGRP, ProGRP(31-98), could serve as a more accurate tumour marker in patients with SCLC than neuron-specific enolase (NSE). ProGRP(31-98) and NSE were measured retrospectively in 101 newly diagnosed untreated patients with SCLC, 111 with non-small-cell lung cancer (NSCLC) and 114 patients with non-malignant lung diseases. ProGRP(31-98) and NSE levels were determined using a sandwich enzyme-linked immunosorbent assay. Sensitivity in SCLC patients was 72.3% for ProGRP(31-98) and 62.4% for NSE. Comparing the area under curve (AUC) of 'receiver operator characteristics' of ProGRP(31-98) with that of NSE, ProGRP(31-98) was the more powerful marker in the diagnosis of SCLC (P = 0.0001). Serum levels of ProGRP(31-98) were higher in the 40 patients with extensive disease than in the 61 patients with limited disease (P = 0.0082). ProGRP(31-98) was significantly higher in patients with pure small-cell carcinoma than in patients with mixed small-cell/large-cell carcinoma (P = 0.02). In serial measurement in 16 patients responding to treatment, a high degree of correlation was noted between the decrease in serum ProGRP(31-98) levels and clinical response during the second week after treatment (P = 0.0045). These results indicate that the determination of serum ProGRP(31-98) levels plays an important role in the diagnosis and treatment of SCLC patients.

Immunohistochemistry in diagnostic dermatopathology

Immunopathology continues to be important in diagnostic dermatopathology. Immunopathology is an invaluable tool for assessing the tissue of origin or direction of differentiation of cells. In some cases this can result in a more precise diagnosis. This article reviews the role of immunopathology in determining the biologic behavior of hematolymphoid infiltrates. It explores the methodology of immunoperoxidase, discusses the most commonly used antibody reagents, and presents a series of diagnostic dilemmas in which immunopathology can be useful. In each case a strategy is established that maximizes the likelihood of making a definitive diagnosis.

A rhesus monkey model to characterize the role of gastrin-releasing peptide (GRP) in lung development. Evidence for stimulation of airway growth

Gastrin-releasing peptide (GRP) is developmentally expressed in human fetal lung and is a growth factor for normal and neoplastic lung but its role in normal lung development has yet to be clearly defined. In this study we have characterized the expression of GRP and its receptor in fetal rhesus monkey lung and determined the effects of bombesin on fetal lung development in vitro. By RNA blot analysis, GRP mRNA was first detectable in fetal monkey lung at 63 days gestation, reached highest levels at 80 days gestation, and then declined to near adult levels by 120 days gestation; a pattern closely paralleling GRP expression in human fetal lung. As in human lung, in situ hybridization localized GRP mRNA to neuroendocrine cells though during the canalicular phase of development (between 63-80 days gestation) GRP mRNA was present not only in classic pulmonary neuroendocrine cells, but also in cells of budding airways. Immunohistochemistry showed that bombesin-like immunoreactivity was present in neuroendocrine cells, but not in budding airways, suggesting that in budding airways either the GRP mRNA is not translated, is rapidly secreted, or a related, but different RNA is present. RNase protection analysis using a probe to the monkey GRP receptor demonstrated that the time course of receptor RNA expression closely paralleled the time course of GRP RNA expression. In situ hybridization showed that GRP receptors were primarily expressed in epithelial cells of the developing airways. Thus GRP would appear to be secreted from neuroendocrine cells to act on target cells in developing airways. This hypothesis was confirmed by organ culture of fetal monkey lung in the presence of bombesin and bombesin antagonists. Bombesin treatment at 1 and 10 nM significantly increased DNA synthesis in airway epithelial cells and significantly increased the number and size of airways in cultured fetal lung. In fact, culturing 60 d fetal lung for 5 d with 10 nM bombesin increased airway size and number nearly to that observed in cultured 80 d fetal lung. The effects of bombesin could be blocked by specific GRP receptor antagonists. Thus this study demonstrates that GRP receptors are expressed on airway epithelial cells in developing fetal lung and that the interaction of GRP with the GRP receptor stimulates airway development.

Signal transduction pathways: new targets in oncology

For many years the main strategies in the development of anticancer drugs were focused on killing tumour cells by means of agents which are blockers of transcription or translocation. However, it is evident that the currently available anticancer drugs, mainly antimetabolites and alkylating agents, cannot cure the most common types of cancer in adults. Therefore, totally new approaches are necessary in cancer chemotherapy research; one of these is disturbing cell signalling pathways involved in growth and malignant transformation. Several studies have concentrated on mechanisms of cell growth and differentiation, control through growth factor receptors and their ligands, oncogenes, proto-oncogenes and other membrane-associated signaling mechanisms. This paper discusses the potential targets in these signaling pathways for novel anticancer drugs.

Molecular cloning and characterization of receptors for the mammalian bombesin-like peptides

The bombesin-like peptides comprise a large family of peptides common to both amphibians and mammals that function as growth factors, neurotransmitters, and paracrine hormones. GRP, the mammalian homolog of bombesin and its receptor, as well as NMB, the mammalian homolog of ranatensin, are expressed in human neoplasms and, in particular, in small cell lung carcinomas (SCLC). To better characterize the physiological roles of bombesin-like peptides, our laboratory has cloned the receptors for GRP in murines, rats, and humans. The 3T3 GRP receptor was isolated and characterized using the two-electrode-voltage-clamp analysis and acquorin-emission methods in xenopus oocytes expression system. The rat and human GRP and NMB receptors were cloned by hybridization at low stringency, using the mouse cDNA receptor probe. Sequence analysis of the receptors showed 384 and 390 amino acids for GRP and NMB receptors, respectively. The homology between the two receptors is 60% and between species in the same receptor, 90%. The receptors belong to the 7-membrane spanning domains superfamily. The specific GRP-R antagonist blocked the response to bombesin in oocytes injected with GRP-R, but failed to do so in oocytes injected with NMB-R. The two receptors differ in their distribution of tissue expression. RNA blot and RNase protection analysis showed the same size of mRNA without alteration in the receptors. RT + PCR analysis performed on genomic DNA revealed similarity between normal and cell DNAs, suggesting no major gene deletion or rearrangement. Southern blot analysis indicated the absence of gene amplification. Sequence analysis of the exonic segments of the receptor genes displayed identical amino acids to the respective cDNAs. None of the genes had classic TATAA box. Somatic cell hybrids localized the GRP-R on the X-chromosome and the NMB-R on chromosome 6. The same sequence of normal genes and cDNAs of GRP and NMB receptors, together with the gene characterization, demonstrated that SCLC cell lines do not require a structural change in receptor protein or genomic rearrangement.

Isolation and sequence of a cDNA encoding the precursor of a bombesinlike peptide from brain and early embryos of Xenopus laevis

A cDNA encoding the precursor of a bombesinlike peptide was isolated from brain of Xenopus laevis. The predicted end product resembles neuromedin B, which was originally isolated from mammalian spinal cord. The mRNA for this precursor was also present in gastrointestinal tract and in ovaries. Moreover, it could be detected in early embryos (stage 2 and stage 10) of X. laevis. These findings suggest novel roles for peptides of the bombesin family in oocyte maturation and early amphibian development.

The secretory granule peptides 7B2 and CCB are sensitive biochemical markers of neuro-endocrine bronchial tumours in man

OBJECTIVE

Bronchial tumours are the most frequent cause of the ectopic ACTH syndrome. Two types of tumours are classically responsible: the relatively benign carcinoids and the highly aggressive small cell carcinomas. Both have neuro-endocrine features and are thought to originate from the endocrine component of the bronchial tree. Our objective was to assess the sensitivity of 7B2 and secretogranin 1 as new biochemical markers of neuro-endocrine differentiation in these tumours in comparison with gastrin releasing peptide.

METHODS

Tissue concentration of 7B2, secretogranin 1 fragments (GAWK and CCB), gastrin releasing peptide and beta-endorphin were measured in normal human lung (n = 4), bronchial carcinoid tumours with (n = 5) and without (n = 15) the ectopic ACTH syndrome, small cell carcinomas (n = 2), squamous cell carcinomas (n = 11) and adenocarcinomas (n = 6). Molecular weight forms of immunoreactive--ACTH, -GAWK, -gastrin releasing peptide, and -7B2 were also examined using gel exclusion chromatography and Western blot analysis.

RESULTS

We detected 7B2 immunoreactivity in 19 of 22 neuro-endocrine lung tumours (with values ranging from less than 5 to 555 fmol/mg wet weight tissue), CCB immunoreactivity in 20 of 22 tumours with neuro-endocrine features (with values ranging from less than 5 to 19,875 fmol mg wet weight tissue) and gastrin releasing peptide immunoreactivity in 10 of 22 neuro-endocrine lung tumors (with values ranging from less than 5 to 11,132 fmol/mg wet weight tissue). Immunoreactive 7B2 and CCB were detected neither in tumours with non-endocrine features, nor in the four normal lung specimens. Differing molecular weight forms of immunoreactive 7B2 in two bronchial carcinoids associated with the ectopic ACTH syndrome showed a predominant signal corresponding to a molecular weight of 22 kDa; in addition, a second signal of 19 kDa was also present. The differing molecular weight forms of immunoreactive ACTH related peptides in the five tumours responsible for the ectopic ACTH syndrome showed, in addition to ACTH1-39, the constant presence in variable proportions of corticotrophin-like intermediary lobe peptide (or ACTH18-39). The differing molecular weight forms of immunoreactive GAWK showed heterogeneous results with materials eluting at Kav of 0, 0.3 and 0.4 respectively. In the three bronchial carcinoids studied, two immunoreactive gastrin releasing peptide molecular weight forms were always found at Kav of 0.5 and 0.85 corresponding to gastrin releasing peptide and its fragment 14-27 respectively.

CONCLUSION

Our results show that 7B2 and the two fragments of secretogranin 1 (GAWK and CCB) are the best biochemical markers of neuro-endocrine differentiation in human lung tumours.

Polysialic acid of the neural cell adhesion molecule distinguishes small cell lung carcinoma from carcinoids

The neural cell adhesion molecule (NCAM) exists in various types of neuroendocrine cells and their tumors. A typical feature of NCAM is polysialic acid, of which the chain length is developmentally regulated. The authors have performed a comparative immunohistochemical study on small cell lung carcinomas and bronchial as well as gastrointestinal carcinoids with the monoclonal antibody (MAb) 735 reactive with the long-chain form of polysialic acid. The small cell lung carcinomas, irrespective of their histological type, were positive for polysialic acid. Metastatic tumor cell complexes also exhibited immunostaining. The tumor cell-surface-associated immunostaining for polysialic acid was sensitive to endoneuraminidase. The mature and atypical bronchial and gastrointestinal carcinoids were not immunoreactive for polysialic acid. Cytoplasmic staining in groups of cells of carcinoids (2 of 28 cases) was due to nonspecific antibody binding, which could be prevented by increased ion strength. These data indicate that neuroendocrine tumors of the lung can be distinguished by their content of highly sialylated NCAM.

Autocrine growth factors and solid tumor malignancy

The ability of malignant cells to escape the constraint that normally regulate cell growth and differentiation has been a primary focus of attention for investigators of cancer cell biology. An outcome of this attention has been the discovery that the protein products of oncogenes play a role in the activation of growth signal pathways. A second outcome, possibly related to abnormal oncogene expression, has been the discovery that malignant cells frequently show an ability to regulate their own growth by the release of autocrine growth modulatory substances. Most important, the growth of certain malignant cell types has been shown to depend on autocrine growth circuits. A malignant tumor whose continued growth depends on the release of an autocrine growth factor may be vulnerable to treatment with specific receptor antagonists or immunoneutralizing antibodies designed to break the autocrine circuit. Information is rapidly emerging concerning autocrine growth factors in selected human solid tissue malignancy.

Somatostatin and analogues in the treatment of cancer. A review

Somatostatin is a naturally occurring cyclic tetradecapeptide that inhibits release of growth hormone and all gastrointestinal hormones. The beneficial effect of somatostatin in the treatment of certain hypersecretory disorders of hormone excess in well recognized; however its clinical usefulness has been limited in the past by its extremely short plasma half-life. The development of long-acting somatostatin analogues has provided clinically useful agents for treatment of hormone-producing tumors. In addition to well-known inhibiting effects on hormone release and actions, recent studies using experimental tumor models have demonstrated an antiproliferative effect of somatostatin and its analogues on growth of a variety of neoplasms. The exact role of somatostatin analogues in cancer therapy has yet to be established; however studies suggest that these agents could provide a useful and relatively nontoxic adjuvant therapy in the treatment of certain tumors. In this review, the oncologic application of somatostatin and possible mechanism of action are examined and current clinical and experimental studies are summarized.

Expression of the gastrin-releasing peptide gene in carcinomas of the breast

Expression of gastrin-releasing peptide (GRP), the mammalian homologue of the amphibian bombesin, has been investigated at gene and protein level in a series of 28 primary breast carcinomas, in 6 mammary cancer cell lines and in one transplantable rat mammary carcinoma. Moderate to strong expression of GRP mRNA was detected in 5 breast carcinomas by Northern blot analysis with a pre-pro-GRP probe; 4 other cases were weakly reactive. Two of these cases also gave a specific immunocytochemical reaction for GRP, controlled with absorption experiments. Correlation with NE differentiation [as shown by chromogranins (Cg) and/or NSE and/or Grimelius positivity] was low, since only one case of breast carcinoma co-expressed GRP and Cg mRNAs. Breast cancer cell lines and a rat carcinoma gave negative results. GRP production in breast cancer did not appear to bear prognostic implications, but longer follow-up periods are needed to confirm these data. As shown in small-cell lung cancer, GRP might be involved in autocrine growth control mechanisms of a group of breast carcinomas.

Growth factors in lung cancer: possible etiologic role and clinical target

Growth factors play an important role in the pathogenesis and progression of all histologic types of lung cancer. Ideas for the exploitation of growth factors in lung cancer management are growing. The inhibition of the interaction between growth factors and their receptors, utilization of negative growth factors, interruption of the signal transduction pathways, or effecting decreased growth factor and/or receptor expression, could result in cell death, and all seem logical possibilities for new and specific treatment approaches. There can be no question that observations of the abnormal expression of growth factors have made a startling impact in every aspect of cancer research. The elucidation of their role in cell proliferation, coupled with our growing knowledge of the functions of oncogenes, has given birth to a unifying concept for the etiology of malignant transformation, which hopefully will translate into new, less toxic, more effective, and desperately needed lung cancer treatment.

Gastrin-releasing peptide in normal and neoplastic human lung: measurement and biochemical characterization

Levels of gastrin-releasing peptide (GRP) were determined by radioimmunoassay in human normal main and lobar bronchus and parenchymal lung tissue extracts. It was found that the level of GRP differed significantly between all 3 areas. The concentration of GRP was statistically higher in main bronchus (median 6.74 ng/g) compared to both lobar bronchus (median 4.79 ng/g) and parenchymal lung (median 1.73 ng/g), and also statistically higher in lobar bronchus compared to parenchymal lung. Chromatographically, GRP-immunoreactivity in both main and lobar bronchial extracts corresponded to GRP1-27 and GRP18-27, while in lung tissue only one major species was identified which corresponded in retention time to GRP18-27. No significant difference was detected when the levels of GRP in normal lobar bronchus and normal lung tissue were compared to the levels in lobar bronchus and lung taken from patients with lung carcinoma, at a site adjacent to the carcinoma. However, a significant difference was observed between the GRP content of normal main bronchus compared to main bronchus from patients with carcinoma. GRP was measured in 26/56 lung carcinomas examined. The levels ranged from 42,000 ng/g in a carcinoid tumour to 0.18 ng/g in a squamous-cell carcinoma, though only in 6 tumours were the levels outside the range determined for normal pulmonary tissue. Chromatography of selected tumour extracts of different histopathologies showed that there were differences in the GRP products present.

Characterization, in some human breast cancer cell lines, of gastrin-releasing peptide-like receptors which are absent in normal breast epithelial cells

The binding of 125I-Tyr4 bombesin was investigated on plasma membranes of 8 human breast cancer cell lines and 2 long-term cultures of normal human breast epithelial cells. Scatchard plots were compatible with high-affinity, single-site class of receptors in 3 cell lines (KD of 0.75 x 10(-9) and 10(-9) M, Bmax of 0.75 x 10(-13) and 9.7 x 10(-13) M/mg protein in MDA-MB231 and in T47D cells, respectively) while no binding was observed in 5 other cell lines and normal epithelial cells. The neuropeptide and its structural analogues (natural or synthetic) inhibited the binding of 125I-Tyr4 bombesin in the following order of potency: gastrin-releasing peptide (GRP, EC50 = 1.7 x 10(-10) M) greater than BIM 26159 greater than bombesin, Tyr4 bombesin greater than BIM 26147 greater than litorin greater than neuromedin C. In contrast, 125I-Tyr4 bombesin binding was not displaced by neuromedin B, somatostatin, bradykinin and insulin. In agreement with our binding data, SDS-PAGE of the complex 125I-Tyr4 bombesin-receptor covalently linked by ethylene glycol-bis succinimidyl succinate (EGS) identified after autoradiography a single band with a molecular weight of 75,000, which disappeared in the presence of bombesin in excess. No transcription of either GRP or neuromedin B mRNA could be shown in tumor or normal cells. Exogenous gastrin-releasing peptide had no effect on growth of the cell lines when a serum-free medium was used, implicating that in breast cancer cell lines this receptor does not mediate growth but has a functional role.

Expression of gastrin-releasing peptide (human bombesin) gene in large cell undifferentiated carcinoma of the lung

Production of the growth factor gastrin-releasing peptide (GRP) or human bombesin has been shown to be a feature of neuroendocrine tumours of the lung, particularly small cell carcinoma, and is possibly responsible for the characteristically rapid growth of this tumour. Large cell undifferentiated carcinoma of the lung (LCC) is also characterized by rapid growth and there is increasing evidence that some LCCs exhibit neuroendocrine differentiation. We therefore investigated GRP/bombesin immunoreactivity and the expression of GRP gene in ten LCCs. Histologically, all were composed of large cells with abundant cytoplasm, open nuclei, and prominent nucleoli, and there was no evidence of squamous, glandular, or neuroendocrine differentiation. At the ultrastructural level, most showed squamous or glandular differentiation but none contained neuroendocrine granules. None of the tumours showed immunoreactivity for GRP/bombesin but seven of the ten showed a focal hybridization signal when treated with 32P-labelled GRP cRNA probes, indicating the presence of GRP mRNA. This was confirmed by northern blot analysis. This study shows for the first time that GRP gene is expressed in LCC. The production of GRP may contribute to the aggressive behaviour of LCC.

Neuropeptide stimulation of calcium flux in human lung cancer cells: delineation of alternative pathways

Calcium ion flux following the administration of a series of neuropeptides, N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate, and serum was monitored by flow cytometry in selected lung and breast cancer cell lines and Chinese hamster ovary cell line CHO-K1. Calcium ion flux was monitored in individual cells by flow cytometry using the indicator indo-1 AM. Five groups of neuropeptides produced calcium flux changes in lung cancer cell lines and CHO-K1 cells but not in breast cancer cells. The peak increase in free calcium was reached within 10 sec of peptide administration and declined to resting levels in 70-120 sec. When two or more members of the same group were administered simultaneously, calcium flux changes were identical to that produced by each single peptide. When two or more members of different groups were administered simultaneously, an increased calcium release occurred. When identical peptides or peptides from the same group were administered sequentially after the return of calcium concentrations to resting values, no calcium flux resulted from the second peptide. When peptides from different active groups were administered sequentially, a new calcium flux occurred after each peptide. These data are interpreted to mean that members of each active group of peptides trigger a different calcium flux pathway. Thus, many such pathways and different metabolic states exist within the cell. Elucidation of calcium flux pathways in normal and cancer cells may lead to greater understanding of the nature of the malignant defect.

Bombesin receptor in membranes from Swiss 3T3 cells. Binding characteristics, affinity labelling and modulation by guanine nucleotides

Bombesin-like neuropeptides, including mammalian gastrin-releasing peptide (GRP), are potent mitogens for Swiss 3T3 cells. In this study, we have characterized the bombesin receptor in membrane preparations from these cells. Addition of Mg2+ during cell homogenization was essential to preserve 125I-GRP binding activity in the resulting membrane preparation. The effect of Mg2+ was concentration dependent, with a maximum at 5 mM. Specific binding of 125I-GRP was saturable; Scatchard analysis indicated a single class of high-affinity sites of Kd = (2.1 +/- 0.3) x 10(-10) M at 15 degrees C and Kd = (1.9 +/- 0.4) x 10(-10) M at 37 degrees C, and a maximum binding capacity of 580 +/- 50 fmol/mg of protein (15 degrees C) or 604 +/- 40 fmol/mg of protein (37 degrees C). The kinetically derived dissociation constant was 1.5 x 10(-10) M. 125I-GRP binding was inhibited in a concentration-dependent manner by various peptides containing the highly conserved C-terminal heptapeptide of the bombesin family, including bombesin, GRP, neuromedin B and the 8-14 fragment of bombesin. In contrast, a variety of structurally unrelated mitogens and neuropeptides had no effect. The cross-linking agent ethyleneglycolbis(succinimidylsuccinate) covalently linked 125I-GRP to a single Mr 75 000-85 000 protein in membrane preparations of 3T3 cells. Affinity labelling of this molecule was specific and dependent on the presence of Mg2+ during membrane preparation. Finally, the non-hydrolysable GTP analogue guanosine-5'-[gamma-thio]triphosphate (GTP[S]) caused a concentration-dependent inhibition of 125I-GRP binding and cross-linking to 3T3 cell membranes [concentration giving half-maximal inhibition (IC50) approximately 0.2 microM]. The inhibitory effect was specific (GMP, ATP or ATP[S] had no effect at 10 microM) and was due to an increase in Kd from (1.7 +/- 0.2) x 10(-10) M to (4.3 +/- 0.6) x 10(-10) M in the presence of 10 microM-GTP[S]. This modulation of ligand affinity and cross-linking implies that the bombesin receptors that mediate mitogenesis in Swiss 3T3 cells are coupled to a guanine-nucleotide-binding-protein signal-transduction pathway.

Effects of bombesin on human small cell lung cancer cells: evidence for a subset of bombesin non-responsive cell lines

The effects of bombesin on three human small cell lung carcinoma cell (SCLC) lines (NCI-H69, NCI-H128, and NCI-H345) have been examined and compared to the effects of the peptide on the mouse fibroblast cell line Swiss 3T3, and the rat pituitary tumor cell line GH3W5. While all three SCLC lines expressed messenger RNA encoding pro-gastrin releasing peptide (GRP), only the NCI-H345 cells expressed detectable membrane receptors for GRP and responded to nanomolar concentrations of bombesin as shown by 125I-GRP binding, total inositol phosphate accumulation, and increased clonal growth in soft agarose. These data show that some SCLC lines are insensitive to bombesin and do not express detectable membrane receptors for GRP.

Detection of human probombesin mRNA in neuroendocrine (small cell) carcinoma of the lung. In situ hybridization with cRNA probe

The production of human bombesin (gastrin-releasing peptide), a peptide with mitogenic action, is a recognized feature of neuroendocrine (small cell) carcinoma of the lung. However, immunostaining of bombesin is not always possible in these tumors, probably because of poor storage mechanisms or rapid release of hormone. Molecular biological analysis of the gene encoding human bombesin has revealed the DNA sequence of human pro-bombesin. We have used in situ hybridization to study the expression of the human bombesin gene at the cellular level in small cell carcinoma of the lung. Probombesin cDNA was subcloned in pSP64 vector, linearized with Bam HI and transcribed in the presence of phosphorus 32(32P)-cytosine triphosphate (CTP) and SP6 polymerase. The cRNA probe was applied to tissue sections (from six cases of small cell carcinoma of the lung, freshly fixed in 4% paraformaldehyde), cell culture preparations (two different cell lines of small cell carcinoma), and cytologic specimens (smears of cells from three different cases of small cell carcinoma). Hybridization of probombesin mRNA was detected in tumor cells in all samples. Specificity of the signal was determined by control experiments, including the use of a probe which has a sequence identical to probombesin mRNA. Our results provide evidence for the expression of the bombesin gene in small cell carcinoma of the lung at a cellular level and show that probombesin mRNA is highly expressed in these tumors.

Effects of a novel bombesin antagonist analogue on bombesin-stimulated gastric acid secretion and growth hormone release in the pentobarbital-anesthetized rat

A new and specific bombesin receptor antagonist analogue, Leu13 psi [CH2NH]Leu14-bombesin, was studied for inhibition of bombesin-stimulated gastric acid secretion in pentobarbital-anesthetized rats. The analogue potently inhibited bombesin-stimulated gastric acid secretion in a dose-dependent fashion, exhibiting an ID50 of 0.66 mumol/250 g, which corresponds to a molar ratio of bombesin to antagonist of approximately 1:12. This agrees well with antagonist to agonist potency ratios previously reported for inhibition of bombesin-stimulated amylase release from guinea pig pancreatic acinar cells and the growth of murine Swiss 3T3 cells, suggesting functional similarities between the receptor sites involved. Conversely, the analogue failed to inhibit bombesin inhibition of growth hormone release in the sodium pentobarbital-anesthetized rat model and was, in fact, a weak agonist at higher dose levels. This indicates either that this system is not particularly bombesin-specific or that bombesin receptor recognition and signaling requirements are substantially different in the gut and hypothalamus.

Characterization of a bombesin receptor on Swiss mouse 3T3 cells by affinity cross-linking

We have previously identified by chemical cross-linking a cell surface protein in Swiss 3T3 cells of apparent Mr 75,000-85,000, which may represent a major component of the receptor for peptides of the bombesin family in these cells. Because bombesin-like peptides may interact with other cell surface molecules, it was important to establish the correlation between receptor binding and functions of this complex and further characterize the Mr 75,000-85,000 cross-linked protein. Detailed time courses carried out at different temperatures demonstrated that the Mr 75,000-85,000 affinity-labelled band was the earliest cross-linked complex detected in Swiss 3T3 cells incubated with 125I-labelled gastrin-releasing peptide (125I-GRP). Furthermore, the ability of various nonradioactive bombesin agonists and antagonists to block the formation of the Mr 75,000-85,000 cross-linked complex correlated extremely well (r = 0.994) with the relative capacity of these peptides to inhibit 125I-GRP specific binding. Pretreatment with unlabelled GRP for up to 6 h caused only a slight decrease in both specific 125I-GRP binding and the affinity labelling of the Mr 75,000-85,000 protein. We also show that the cross-linked complex is a glycoprotein. First, solubilized affinity labelled Mr 75,000-85,000 complex applied to wheat germ lectin-sepharose columns was eluted by addition of 0.3 M N-acetyl-D-glucosamine. Second, treatment with endo-beta-N-acetylglucosaminidase F reduced the apparent molecular weight of the affinity-labelled band from 75,000-85,000 to 43,000, indicating the presence of N-linked oligosaccharide groups.

A tyrosine protein kinase activated by bombesin in normal fibroblasts and small cell carcinomas

In Swiss 3T3 fibroblasts, antibodies which recognize a phosphotyrosine residue (P-Tyr antibodies) identify a 115-kDa cell surface protein (p115) that becomes phosphorylated on tyrosine as a response to bombesin stimulation of quiescent cells. The extent of phosphorylation is dose-dependent and correlates with the mitogenic effect induced by bombesin, measured by [3H]thymidine incorporation. Tyrosine phosphorylation of p115 is detectable minutes after addition of bombesin and precedes the activation of c-fos and c-myc gene transcription. Immunocomplexes of phosphorylated p115 with P-Tyr antibodies bind 125I-labeled [Tyr4]bombesin in a specific and saturable manner and display an associated tyrosine protein kinase activity enhanced by bombesin. P-Tyr antibodies also recognize a protein of 115 kDa, phosphorylated at tyrosine, in four human SCLC lines producing bombesin but not in a non-producer "variant" line. Phosphorylation of SCLC p115 does not require the addition of exogenous bombesin. As in the case of the p115 immunoprecipitated from mouse fibroblasts, the SCLC p115 is phosphorylated in an immunocomplex kinase assay. These observations are in agreement with the hypothesis of autocrine activation of bombesin receptors in human small cell lung carcinoma cells.

Localization of bombesin-like peptides in tumors

The localization of bombesin gene products in neuroendocrine tumors was achieved by a number of techniques used in combination. These included immunocytochemistry, radioimmunoassay, and chromatographic procedures using a variety of region-specific antibodies recognizing separate portions of probombesin. In situ hybridization using cRNA probes was employed to analyze bombesin gene expression at a cellular level. A novel procedure using a divalent form of bombesin and gold-labeled monoclonal antibodies for the localization of bombesin binding sites at the ultrastructural level was employed in this study. Antibodies to neuron-specific enolase and electron microscopy were employed for the determination of neuroendocrine differentiation. Surgical samples of pulmonary (n = 250) and nonpulmonary (n = 28) small cell carcinomas, 49 carcinoids, and 62 atypical lung carcinoids were investigated and compared with 169 control tumors, including lymphomas, adenocarcinomas, squamous cell carcinomas, and non-small-cell undifferentiated tumors. Cell lines cultured from pulmonary small cell carcinoma and smear preparations of pleural effusions from patients with small cell carcinoma of the lung were also investigated. Strong immunostaining for neuron-specific enolase was noted in all neuroendocrine tumors investigated, and no immunoreactivity was noted in control cases. Electron-dense neurosecretory granules were abundant in carcinoid tumors, scattered in small cell carcinoids, and absent in control cases. Immunostaining for bombesin was particularly strong in benign carcinoids, whereas the more malignant neuroendocrine tumors (e.g., small cell carcinomas) stained best with antibodies to the carboxyl-terminal flanking portion of human probombesin (proGRP). These findings were further validated by radioimmunoassay and chromatography of tissue extracts. Specific binding sites for bombesin were demonstrated on the surface of small cell carcinoma cells maintained in culture. In situ hybridization demonstrated mRNA for preprobombesin in all small cell carcinomas investigated, including surgical samples, cytological preparations, and cell lines. Hybridization reactions varied in intensity, with some cells in autoradiograms almost masked by silver grains and others showing much lighter deposits.

The release of bombesin-like peptides from small cell lung cancer cells

High levels of BN/GRP are present in classic SCLC and lung carcinoids, whereas BN immunoreactivity is absent in variant SCLC, adenocarcinoma, large cell carcinoma, squamous cell carcinoma, and mesothelioma cell lines. BN-like peptides are secreted from classic SCLC into the tissue culture medium. The secretion rate of BN-like peptides from cell line NCI-H345 was increased 3-fold by VIP (1 microM). Also, VIP increased the cAMP levels in cell line NCI-H345 by an order of magnitude. Therefore, SCLC cells have functional VIP receptors which regulate the secretion of BN-like peptides. Also, SRIF (100 nM) inhibits the VIP-stimulated increase in cAMP levels and secretion rate of BN-like peptides from SCLC cells. Because BN stimulates colony formation, VIP and/or SRIF may be able to alter the growth of SCLC cells. BN-like peptides are secreted from SCLC cells into the plasma. The levels of BN immunoreactivity in the plasma of SCLC patients with extensive disease is 2- to 40-fold greater than that of patients with limited disease. Secretin infusion into patients with extensive disease produces a transient increase (7-fold) in the plasma concentration of BN-like peptides. BN-like peptides are also present in the CSF of SCLC patients. When released from SCLC cells, BN-like peptides may interact with cell surface receptors. [Tyr4]BN binds with high affinity (Kd = 0.5 nM) to a single class of sites (1500/cell) on cell line NCI-H345. The carboxyl terminus of BN or GRP is essential for high-affinity binding activity. BN-like peptides elevate cytosolic Ca2+ levels as a result of increased phosphatidylinositol turnover. The putative BN receptor antagonist [D-Arg1, D-Pro2, D-Trp7,9, Leu11]substance P inhibits high-affinity [Tyr4]BN binding, the ability of BN to elevate cytosolic Ca2+ levels, and colony formation of SCLC cells. Therefore, BN receptor antagonists may serve as useful agents to inhibit the growth of SCLC.

Expression of nerve growth factor receptor in paraffin-embedded soft tissue tumors

Identification of growth factors and receptors in mesenchymal tumors may be crucial to understanding of growth regulation in sarcomas. During an immunohistochemical study of the expression of growth factors and receptors in human soft tissue tumors (STT), only 1 antisera capable of working in paraffin-embedded tissue was noted. A detailed study of 141 STT was undertaken to determine the frequency of expression of nerve growth factor receptor (NGF-R), its specificity and sensitivity for neural tumors, and the effect of fixation on detection. In normal mesenchymal tissue, only nerve sheath and perivascular staining was seen. No immunoreactivity was seen in many tumors including rhabdomyosarcoma, angiosarcoma, liposarcoma, Ewing's sarcoma, and alveolar soft part sarcoma. Less than 15% of tumors of smooth muscle, fibrous, or fibrohistiocytic origin showed immunoreactivity, usually focal. In contrast, a high frequency of immunoreactivity was noted in tumors of neural origin (74%). This included granular cell tumors (100%), Schwannoma/neurofibroma (91%), malignant Schwannoma (78%), neuroblastoma/neuroepithelioma (60%), and paraganglioma (57%). A high rate of reactivity was also seen in synovial sarcomas (80%), undifferentiated sarcomas (60%), and hemangiopericytomas (43%), suggesting a potential relationship to the neural phenotype. Among the neural tumors, Bouin's fixation was superior to formalin, suggesting that immunoreactivity for NGF-R is affected by fixation. This antibody may be a useful adjunct marker diagnostically.

Bombesin and bombesin antagonists: studies in Swiss 3T3 cells and human small cell lung cancer

Bombesins are potent growth factors for murine Swiss 3T3 cells. Using these cells in chemically defined conditions we have been able to characterise the bombesin receptor and the early signals preceding DNA synthesis. We describe two substance P analogues [DArg1, DPro2, DTrp7,9, Leu11] substance P and [DArg1, DPhe5, DTrp7,9, Leu11] substance P which competitively block the binding of bombesins to their receptor and all the events leading to mitogenesis. Bombesins are secreted by human small cell lung cancers (SCLC) and may act as autocrine growth factors for these tumours, so the development of peptide bombesin antagonists could have therapeutic implications. We demonstrate that the antagonists can reversibly inhibit the growth of SCLC in vitro, with relatively little effect on other lung tumours.

Characterization of the high-affinity receptors on Swiss 3T3 cells which mediate the binding, internalization and degradation of the mitogenic peptide bombesin

Bombesin and bombesin-related peptides such as gastrin-releasing peptide (GRP) stimulate DNA synthesis and proliferation of Swiss 3T3 cells in culture. We have used 125I-labelled [Tyr4]bombesin and 125I-labelled GRP to characterize and identify the receptors for these peptides on Swiss 3T3 cells. The binding of 125I-[Tyr4]bombesin, which retained full biological activity, was maximal between 20 and 30 min incubation at 37 degrees C, after which continued incubation led to a decline in cell-associated radioactivity. This decline was markedly slowed by the presence of lysosomal enzyme inhibitors. Specificity of the binding site was indicated by the competitive inhibition of binding by bombesin-related peptides, but not by unrelated peptides and growth factors. Scatchard analysis of binding data indicated a single class of high-affinity receptors. The calculated value for the dissociation constant (Kd) was 2.1 nM and each cell possesses approx. 240,000 receptors. Because [Tyr4]bombesin has no free amino group, 125I-GRP was used in chemical cross-linking studies. When disuccinimidyl suberate was used to covalently couple 125I-GRP to the cells, two major radiolabelled complexes were detected with molecular masses of approx. 80,000-85,000 and 140,000. The binding of 125I-[Tyr4]bombesin to the cells was pH-dependent with maximal binding at pH 6.5-7.5 and effectively no specific binding at pH values below 4.5. At 37 degrees C, cell-associated 125I-[Tyr4]bombesin quickly became resistant to removal by acidic buffers, suggesting its rapid transfer to an intracellular compartment. However, pre-incubation with unlabelled [Tyr4]bombesin did not induce down-regulation of bombesin receptors as measured by the subsequent binding of 125I-[Tyr4]bombesin. In contrast with the Swiss 3T3 cells, specific binding of 125I-[Tyr4]bombesin was not detectable in two cell lines which are biologically unresponsive to bombesin-related peptides.

Immunohistochemical evaluation of neuroendocrine cells and neoplasms of the lung

The dispersed neuroendocrine (NE) system is represented in the bronchopulmonary tract by submucosal nerves and ganglion cells and, in the mucosal lining by solitary NE cells and neuroepithalial bodies (NEB's). The latter two components variably express pan-NE markers including NSE, chromogranin (s) and, notably, synaptophysin. The expression of serotonin, bombesin, calcitonin and leu-enkephalin has been well established; additional eutopic materials include somatostatin and calcitonin gene-related peptide. Solitary NE cells and NEB's are epithelial structures as defined by their consistent cytokeratin expression. Hyperplasia and dysplasia of NE cells may be found in association with various forms of chronic injury; they have been noted in chronic bronchiectasis and in the vicinity of neoplasms of various types. Hyperplastic and dysplastic pulmonary NE cells frequently express ectopic materials particularly ACTH. NE neoplasms of the bronchopulmonary tract comprice a spectrum that includes a) carcinoids, b) well differentiated NE carcinomas, c) intermediate cell NE carcinomas and d) small cell NE carcinomas. The precise pathologic criteria defining these entities are discussed in detail as are their clinical implications. The entire spectrum of lung NE neoplasms express NE markers demonstrable by immunocytochemistry; these include pan-NE markers, serotonin and numerous neuropeptides. The expression of multiple hormonal materials is frequent. Within any given tumor, some variation in expression may be noted in different sites and in different periods of the "normal" or therapeutically modified lifespan of the tumor. The entire spectrum of lung NE neoplasms is epithelial for they express cytokeratin polypeptides and desmoplakin; subsets of the tumors coexpress cytokeratins and neurofilament proteins. Also, subsets of these NE neoplasms may be immunostained with monoclonal antibodies to antigens related to exocrine phenotype suggesting focal amphicrine features.

Activation of the protein-tyrosine kinase associated with the bombesin receptor complex in small cell lung carcinomas

It has been hypothesized that bombesin-like peptides produced by small cell lung carcinomas may sustain deregulated proliferation through an autocrine mechanism. We have shown that the neuropeptide bombesin leads to the activation of a protein-tyrosine kinase that phosphorylates a 115-kDa protein (p115) associated with the bombesin receptor complex in mouse Swiss 3T3 fibroblasts. We now report that phosphotyrosine antibodies recognize a 115-kDa protein, phosphorylated on tyrosine, in four human small cell lung carcinoma cell lines producing bombesin but not in a nonproducer "variant" line. p115 from detergent-treated small cell lung carcinoma cells binds to bombesin-Sepharose and can be phosphorylated on tyrosine in the presence of radiolabeled ATP and Mn2+. As for the p115 immunoprecipitated from mouse fibroblast, the small cell lung carcinoma p115 can be phosphorylated in an immunocomplex kinase assay. However, the latter does not require the presence of exogenous bombesin for activity. Binding data, obtained by using radiolabeled ligand, suggest receptor occupancy in the cell lines producing bombesin. These observations are consistent with the hypothesis that proliferation in some human small cell lung carcinoma lines is under autocrine control, regulated through activation of bombesin receptors.