Martin Rotsch

Peptides and growth factors in small cell lung cancer: production, binding sites, and growth effects

SummaryWe investigated the production, binding to cell membranes, and influence on cell proliferation of peptides and growth factors in 4 classic, 5 transitional and 5 variant SCLC cell lines. Glucagon, neurotensin, and TGF-α were present in all cell lines. Bombesin was predominantly found in classic cell lines and insulin in variant cell lines. Neurokinin A, calcitonin, CGRP, GHRF, somatostatin, and CNTF were detectable in some cell lines without prevalence for a particular cell type. We could not detect AVP, growth hormone, neuropeptide Y, substance P, VIP, and NGF. Insulin binding sites were present on 11/14 cell lines, and some cell lines specifically bound bombesin, calcitonin, and EGF. Growth effects were detectable for insulin, GRP-related peptides, tachykinins, and VIP. Using serum-free conditions, insulin and VIP had a growth stimulating effect in liquid culture at nanomolar concentrations. Bombesin and neuromedin B stimulated the clonal growth at a concentration of 3–30 nM. The tachykinins neurokinin A, neurokinin B, physalaemin, and eledoisin inhibited the clonal and mass culture growth with a peak effect in the range of 0.1 to 10 pM. Peptide-induced stimulating and inhibiting effects were within a magnitude of 2-fold. All other peptides and growth factors tested, including ACTH, AVP, calcitonin, glucagon, neurotensin, somatostatin, EGF, CNTF, and NGF did not affect the growth of SCLC. We conclude that the growth of SCLC is partly controlled by such peptides in an autocrine/paracrine fashion.

Production of immunoreactive insulin-like growth factor I and response to exogenous IGF-I in small cell lung cancer cell lines

Small cell lung cancer (SCLC) cell lines were examined for the presence of insulin-like growth factor I-related protein (IGF-I) in cell pellets and culture media. IGF-I immunoreactivity was detected in 11/14 pellets, ranging from 12 to 76 mIU/mg soluble protein. The IGF-I levels in the cell pellets showed a correlation to the corresponding culture media. IGF-I binding sites were found in all tested cell lines. The maximum binding (Bmax) ranged from 131 to 1230 fmol/mg protein and the dissociation constant (KD) from 0.89 to 5.21 nM. The incorporation of [3H]thymidine in the presence of recombinant human IGF-I resulted in a clearly increased DNA synthesis in two of seven cell lines. Thus, IGF-I may be an important growth factor in SCLC.

NCAM: a surface marker for human small cell lung cancer cells.

Immunocytochemical and immunochemical techniques were used to study the expression of the neural cell adhesion molecule (NCAM) by human lung cancer cell lines. Intense surface staining for NCAM was found at light and electron microscopic levels on small cell lung cancer cells. The NCAM polypeptide of M r 140000 (NCAM 140) was detected by immunoblotting in all of 7 small cell lung cancer cell lines examined and in one out of two of the closely related large cell cancer cell lines: it was not detected in cell lines obtained from one patient with a mesothelioma, in two cases of adenocarcinoma, nor in two cases of squamous cell cancer. In contrast, neuron‐specific enolase was found by immunoblotting in all the lung cancer cell lines tested and synaptophysin in all but the adenocarcinoma cell lines. These antigens were localized intracellularly. The specific expression of NCAM 140 by human small and large cell lung carcinomas suggests its potential as a diagnostic marker.

Characterization of insulin-like growth factor I receptors and growth effects in human lung cancer cell lines

SummarySmall-cell lung cancer (SCLC) and non-smallcell lung cancer (NSCLC) cell lines were studied for insulin-like growth factor I (IGF-I) receptor expression and with regard to the influence of IGF-I on cell proliferation. IGF-I receptors on the cells were characterized by competitive binding assays, chemical crosslinking and northern blot hybridization of IGF-I receptor mRNA. All SCLC and NSCLC cell lines showed specific IGF-I binding sites with an affinity (KD) of 0.69–5.21 nM. The amount of binding sites ranged from 59 fmol/mg to 1230 fmol/mg protein. The IGF-I binding was inhibited by the IGF-I receptor antibody (α-IR-3). Northern blot hybridization indicated that IGF-I receptor mRNA was being produced by all SCLC and NSCLC cell lines. We used the soft-agarose clonogenic assay to evaluate the influence of IGF-I on the in vitro proliferation of the cells. Our results have shown that IGF-I stimulates the growth of all tested cell lines ranging from a factor of 1.6 to 4.2 in SCLC and from 1.1 to 2.7 in NSCLC. The data indicate that the IGF-I receptor thus appears to be the common pathway for the mitogenic activity of IGF-I and IGF-II with regard to human lung cancer cells.

Substance P analogues function as bombesin receptor antagonists and inhibit small cell lung cancer clonal growth

Human small cell lung cancer (SCLC) produces and secretes BN/GRP (bombesin/gastrin releasing peptide). Because BN stimulates the growth of SCLC cells and these cells have receptors for BN-like peptides, it is important to define agents which disrupt this self-promoting autocrine growth cycle. Here, substance P analogues were evaluated as BN receptor antagonists using SCLC cell lines. (D-Arg1, D-Pro2, D-Trp7.9, Leu11) substance P [(APTTL)SP] was one of the more potent analogues tested in inhibiting BN-like peptide receptor binding with an IC50 value of 1 microM. Micromolar concentrations of (APTTL)SP antagonized BN receptor mediated elevation of cytosolic Ca2+ levels and decreased the colony formation in soft agarose. These data suggest that SP analogues function as SCLC BN receptor antagonists and may be useful in disrupting the autocrine growth function of BN-like peptides.

Production of insulin-like growth factor binding proteins by small-cell lung cancer cell lines

Conditioned serum-free media (CM) from small-cell lung cancer (SCLC) cell lines were examined for the presence of insulin-like growth-factor-binding proteins (IGF-BP). 6/9 SCLC cell lines secreted binding proteins with high affinity for IGFs. When [125I]IGF-I or [125I]IGF-II was incubated with the CMs, complexes of tracer with proteins could be demonstrated by gel filtration, by precipitation with polyethylenglycol, and after adsorption of unbound tracer with activated charcoal. Analysis of binding data according to the method of Scatchard resulted in linear plots for IGF-I and IGF-II. The dissociation constants were determined to be 0.106 nM for IGF-I and 0.209 nM for IGF-II binding. Cross-linking of [125I]IGF-I or [125I]IGF-II to the CMs followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions revealed the presence of IGF-BPs with molecular masses in the range 24-32 kDa. The binding was competitively inhibited by addition of cold IGF-I and IGF-II but not by insulin. Northern blot hybridization with an IGF-BP cDNA probe encoding a low-molecular-weight IGF-BP from a human placenta cDNA library and Western blot analysis with a corresponding polyclonal antibody showed no expression of this gene. These data demonstrate that SCLC cell lines release IGF-BPs in culture supernatants, which differ from IGF-BPs detected in liver and placenta. These IGF-BPs might be important mediators in the autocrine/paracrine growth regulation of IGFs in SCLC.

Differential expression of the intercellular adhesion molecule-1 (ICAM-1) in lung cancer cell lines of various histological types

Ten small cell lung carcinoma and 12 non-small cell lung carcinoma cell lines of various histological types were studied for constitutive expression of the intercellular adhesion molecule-1 (ICAM-1). ICAM-1 was present in all squamous and large cell carcinoma cell lines whereas two out of five adenocarcinoma and all small cell lung cancer (SCLC) cell lines showed no basal ICAM-1 expression. ICAM-1 expression was upregulated by tumour necrosis factor-alpha (TNF-alpha) in a time- and dose-dependent manner in cell lines with basal ICAM-1 expression. Western blot analysis revealed a molecular size of 85 kDa for ICAM-1 in all but one cell line. The TNF-alpha-induced upregulation of ICAM-1 occurs on the transcriptional level. Adhesion of peripheral blood mononuclear cells to lung tumour cell lines could be inhibited by monoclonal antibodies (MAb) (CD11a;CD18) against the receptor of ICAM-1, the leukocyte function-associated antigen-1 (LFA-1), but not by a MAb (CD54) against ICAM-1 itself.

Soluble intercellular adhesion molecule-1 in patients with lung cancer and benign lung diseases.

Abstract Intercellular adhesion molecule-1 (ICAM-1) expression correlates with tumour progression in patients with malignant melanoma or renal cell carcinoma. To assess the value of soluble ICAM-1 (sICAM-1) for lung cancer patients, sICAM-1 was determined by means of an enzyme-linked immunosorbent assay. Sera from 147 patients with lung cancer, from 75 patients with benign lung diseases and from 108 healthy adults were investigated for sICAM-1 expression. Significant differences in sICAM-1 levels were detected in lung cancer patients (387 ± 176 ng/ml) and patients with benign lung diseases (365 ± 110 ng/ml) compared to the group of healthy adults (310 ± 90 ng/ml). There was no difference in sICAM-1 level among the subtypes of lung cancer. Advanced tumour stages and patients with progressive disease tended to be associated with higher sICAM-1 levels, the site of metastasis being relevant for the level attained. Patients with liver metastasis had the highest sICAM-1 levels (547 ± 295 ng/ml) compared to patients with cerebral metastasis (317.8 ± 92.2 ng/ml). An increase of sICAM-1 expression during the progression of the disease coincided with a poorer survival prognosis for the patients compared to patients with stable or falling sICAM-1 levels.

Growth regulation by insulin-like growth factors in lung cancer

Lung cancer is a major health problem, with over 38,000 new cases expected every year in West Germany. A more complete understanding of the biology of lung cancer will hopefully lead to therapeutic modalities. The possible autocrine growth regulation in small-cell lung cancer and non-small-cell lung cancer has been demonstrated for bombesin/GRP, vasopressin, neurotensin, EGF/TGF alpha, transferrin-related peptides and insulin-like growth factors. This contribution concentrates on recent data concerning binding sites, growth promoting effects and secretion of IGFs in lung cancer cell lines. The production of IGF-binding proteins which were also produced by lung cancer cell lines modifies the autocrine/paracrine model for IGFs since then proteins can either enhance or inhibit the effect of IGFs on tumor growth.

Epidermal growth factor receptor expression, proliferation, and colony stimulating activity production in the urinary bladder carcinoma cell line 5637

SummaryAddition of epidermal growth factor (EGF) to cultures of the urinary bladder carcinoma cell line 5637 regulated proliferation and production of colony stimulating activity (CSA). The optimal concentration range of EGF for stimulation of cell proliferation was 5–20 ng/ml EGF and for production of CSA 2–20 ng/ml EGF. High EGF concentrations (100–200 ng/ml) showed inhibitory effects on proliferation and to a greater extent on CSA production. Also, EGF binding sites of high affinity (kD: 3.25 nM) were demonstrated on the cell surface. In the optimal concentration range for stimulation (5–20 ng/ml EGF) EGF binding sites were occupied half-maximally. The loss in EGF binding after long incubation at 37°C was prevented by the lysosomal inhibitory agent, chloroquine. Nonspecific binding of EGF was very low, the amount of maximally bound EGF was 1430 fmol/mg protein (130,000 bound EGF molecules/cell). A strong band of approximately 170,000 daltons could be detected by means of an anti-erbB serum which recognizes the EGF receptor protein. The protein became phosphorylated upon addition of γ-32P ATP. The data suggest that EGF initiates its action by binding to specific high affinity receptors and plays a role in growth regulation and differentiation of the urinary bladder carcinoma cell line 5637.