Insulin-like growth factor binding protein expression in human small cell lung cancer cell lines

Production of insulin-like growth factor binding proteins by human ovarian carcinoma cells

Cells of the human ovarian carcinoma lines EFO-21, EFO-27, MFO-35 and MFO-36 secrete binding proteins for insulin-like growth factors (IGFBPs) into their culture media. By sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) and ligand blotting, seven groups of IGFBPs with molecular masses of 25, 30 (doublet), 34, 37, 40, 45, and 50 kDa were observed, depending on the cell line under investigation. By Northern blot analyses using cDNAs or oligonucleotides specific for the six types of IGFBP (IGFBP-1 to IGFBP-6), mRNA for all IGFBPs tested except for IGFBP-1 could be detected in the ovarian carcinoma cell extracts. In detail, analysis of EFO-21 protein products by SDS-PAGE yielded IGFBPs of 25, 34, and 50 kDa; extracts of EFO-21 cells contained mRNAs for IGFBP-2, -3, -4, and -6. EFO-27 cells produced IGFBPs of 40 kDa and 45 kDa as determined by SDS-PAGE, and mRNAs for IGFBP-3, -4, and -6 were detected. In the conditioned medium of MFO-35 cells, IGFBPs of 25, 30 (doublet), 34, 37, 40, and 45 kDa were observed by SDS-PAGE, while mRNAs for the five proteins IGFBP-2 to IGFBP-6 were found. MFO-36 cells produced IGFBPs of 34 kDa and 50 kDa as determined by SDS-PAGE, and the cells expressed mRNAs for IGFBP-2, -3, -4, and -6. In relation to published molecular mass data of the known IGFBPs, the size of the secreted proteins could be correlated to the mRNA patterns expressed by the ovarian carcinoma cells. It is concluded that ovarian carcinoma cells frequently express IGFBP-3, -4, and -6 and, to a lesser extent, IGFBP-2; the expression of IGFBP-5 appears as a rather rare event, while IGFBP-1 was not found to be expressed in ovarian carcinoma cells.

Biology of lung cancer

While the overall survival of patients with lung cancer has remained relatively unchanged over the past decade, there have been major advances in our understanding of the biology of small cell and non-small cell lung cancer through the study of lung cancer cell lines. Surface molecules associated with lung cancer have been identified and their molecular structure and function are being elucidated. Growth factors which stimulate the lung cancer cells in an autocrine fashion have been identified. Genetic changes of lung cancer cells have been defined on a chromosomal and a molecular level. This review summarizes many biologic properties of lung cancer cells that have been described in the literature.

Expression of insulin-like growth factor receptors I and II in normal human lung and in lung cancer

Insulin-like growth factors are potent mitogenic factors in human lung cancer in vitro, acting via specific receptors. Using monoclonal antibodies we demonstrate the expression of insulin-like growth factor receptor I in bronchial epithelial cells of normal lung and in primary lung cancer (22/24 cases), being most prominent in squamous cell carcinoma. Electron microscopy on lung cancer cell lines reveals a distinct reaction pattern on the plasma membrane. Immunoreaction with a specific antibody directed against the insulin-like growth factor receptor II suggests a weak expression in primary lung cancer. Our findings underline the significance of the autocrine pathway of insulin-like growth factors in lung cancer.

Molecular cloning of IGFBP-5 from SCLC cell lines and expression of IGFBP-4, IGFBP-5 and IGFBP-6 in lung cancer cell lines and primary tumours

We showed recently that insulin-like growth factor binding protein (IGFBP)-1, -2 and -3 are differentially expressed in lung cancer and permanent lung cancer cell lines. Elevated levels of IGF binding capacity in serum of lung cancer patients were also reported. The function and tissue specificity of IGFBP are still obscure but they are probably local regulators of IGF action. Here we show the expression of IGFBP-4 transcripts in 11/11 small cell lung cancer (SCLC) cell lines, in nine out of 11 non-small cell lung cancer (NSCLC) cell lines, in 11/11 lung tumour specimens (10 derived from patients with NSCLC and one from SCLC origin) and in normal lung. In addition we isolated IGFBP-5 cDNA from lambda gt10 libraries of SCLC cell lines. With this IGFBP-5 cDNA we detected transcripts of different lengths in seven out of 11 SCLC cell lines, in 11/11 lung cancer specimens but only in one out of 11 NSCLC cell lines and in normal lung. IGFBP-6 was not detected in northern analysis of any tested SCLC cell line but it was expressed in nine out of 11 NSCLC cell lines and in nine out of 11 human lung cancer specimens and in normal lung.

Differential expression of insulin-like growth factor binding proteins in human non-small cell lung cancer cell lines

The possible expression and secretion of insulin-like growth factor binding proteins (IGFBPs) by non-small cell lung cancer (NSCLC) cell lines was investigated and compared with possible IGFBP expression by primary NSCLC tumours. Cells growing under serum-free conditions released binding proteins with apparent molecular masses of 26-43 kD when analysed by a ligand blotting method under non-reducing conditions. Additionally, northern blot analysis of total RNA from NSCLC cell lines and tumours was performed using cDNAs coding for each of IGFBP-1, IGFBP-2, and IGFBP-3. This analysis revealed expression of all three mRNAs to varying degrees by all cell lines. In contrast all primary tumours analysed expressed predominantly IGFBP-2 and IGFBP-3 and none showed any evident expression of IGFBP-1. Both NSCLC cell lines and tumours synthesise IGFBPs but the pattern of expression differs significantly between cell lines and primary tumours.

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.