Expression of multiple growth factors in a human lung cancer cell line

In Vivo and in Vitro Growth of SCLC Cells Derived from Biopsies

In order to increase the availability of SCLC cells derived from biopsies, in vivo and in vitro growth methods were investigated. The cells grown in both conditions were periodically monitored for reactivity with 2 monoclonal antibodies (MAbs): MLuC1 directed against SCLC cells and IM1 which recognizes the class II antigen on activated lymphocytes and macrophages. About 50 % of the 28 analyzed SCLC specimens were found to proliferate in one or both systems. The in vitro-grown cells exhibited the same heterogeneity found in the original cell suspensions and moreover, in some cases only normal cells were recovered after several in vitro passages. From the subcutaneous transplanted tumors a large number of MLuC1-positive tumor cells could easily be recovered, thus indicating the validity of the in vivo methodology. The MBr1 MAb, directed against an epithelial antigen, was found to react with about 50 % of the 26 tested tumors, mainly those which demonstrated in vivo and/or in vitro growth capacity. These data suggest that only some tumors, presumably with peculiar biological characteristics, can efficiently grow in these artificial systems.

The role of tumor stroma in cancer progression and prognosis: emphasis on carcinoma-associated fibroblasts and non-small cell lung cancer

Maintenance of both normal epithelial tissues and their malignant counterparts is supported by the host tissue stroma. The tumor stroma mainly consists of the basement membrane, fibroblasts, extracellular matrix, immune cells, and vasculature. Although most host cells in the stroma possess certain tumor-suppressing abilities, the stroma will change during malignancy and eventually promote growth, invasion, and metastasis. Stromal changes at the invasion front include the appearance of carcinoma-associated fibroblasts (CAFs). CAFs constitute a major portion of the reactive tumor stroma and play a crucial role in tumor progression. The main precursors of CAFs are normal fibroblasts, and the transdifferentiation of fibroblasts to CAFs is driven to a great extent by cancer-derived cytokines such as transforming growth factor-β. During recent years, the crosstalk between the cancer cells and the tumor stroma, highly responsible for the progression of tumors and their metastasis, has been increasingly unveiled. A better understanding of the host stroma contribution to cancer progression will increase our knowledge about the growth promoting signaling pathways and hopefully lead to novel therapeutic interventions targeting the tumor stroma. This review reports novel data on the essential crosstalk between cancer cells and cells of the tumor stroma, with an emphasis on the role played by CAFs. Furthermore, it presents recent literature on relevant tumor stroma- and CAF-related research in non-small cell lung cancer.

Annulate Lamellae in a Large Cell Lung Carcinoma Cell Line with High Expression of Tyrosine Kinase Receptor and Proto-Oncogenes

The morphology, karyotype, in vitro growth properties, and expression of tyrosine kinase receptors and proto-oncogenes are reported for a newly established large cell undifferentiated lung carcinoma cell line (RVH-6849). The results were analyzed concomitantly with those for two well-established cell lines from an adenocarcinoma of the lung (A549) and a squamous cell carcinoma (A431). All three cell lines demonstrated common ultrastructural features of epithelial cells, but only RVH-6849 had frequent aggregates of centrioles and annulate lamellae (AL) and was polyploid, having five to seven copies of chromosome 7 by karyotype analysis. All three cell lines expressed transforming growth factor alpha (TGF-alpha), epidermal growth factor receptor (EGFR), c-erb B-2, and c-met genes. RVH-6849 cells, however, expressed the most messenger RNA (mRNA) for TGF-alpha, c-erb B-2, and c-met. Only EGFR mRNA was expressed more in the other two cell lines, especially in A431 cells. AL represent an exaggerated form of the nuclear membrane-pore complex that is found in actively proliferating cells such as germ and some neoplastic cells. AL are suspected to be involved in the deposition or processing of mRNA: The enhanced coexpression of AL and mRNAs of three tyrosine kinase-containing receptors in RVH-6849 cells may represent such a relationship.

Systemic immune dysfunction in pancreatic cancer patients

BACKGROUND AND AIMS

We investigated the immune status in 32 pancreatic cancer patients (PC) in comparison with healthy controls (HC).

MATERIALS AND METHODS

Using flow cytometry, peripheral blood lymphocytes (PBL) were characterized by the expression of surface markers for T helper cells (CD4), T suppressor cells (CD8), B cells (CD19) and NK cells (CD56). The blastogenic response of PBL was analyzed after stimulation with concavalin A (ConA), phytohemagglutinin (PHA), pokeweed mitogen (PWM) and anti-CD3 antibodies. The serum levels of TNF-alpha, IL-1beta, IL-2, IL-10, IL-12, IL-18, IL-1RA, sIL-2R and TGF-beta were determined by ELISA.

RESULTS

No differences in the distribution of peripheral immunocytes in PC were found, whereas the blastogenic response of peripheral blood lymphocytes (PBL) after stimulation with PHA or anti-CD3 antibodies was significantly decreased in PC. In PC, we found reduced serum levels of IL-2 and significantly elevated levels of TNF-alpha, TGF-beta1, IL-10, IL-2R, IL-1beta and IL-1RA.

CONCLUSION

These data provide evidence for a systemic immune dysfunction in pancreatic cancer patients characterized by a shift towards a T helper cell type 2 cytokine profile, a significant elevation of substances related to T cell suppression and a reduced blastogenic response to PHA and anti-CD3 antibodies of PBL.

Tumour-stroma interaction: cancer-associated fibroblasts as novel targets in anti-cancer therapy?

Stroma cells, together with extracellular matrix components, provide the microenvironment that is pivotal for cancer cell growth, invasion and metastatic progression. Characteristic stroma alterations accompany or even precede the malignant conversion of epithelial cells. Crucial in this process are fibroblasts, also termed myofibroblasts or cancer-associated fibroblasts (CAFs) that are located in the vicinity of the neoplastic epithelial cells. They are able to modify the phenotype of the epithelial cells by direct cell-to-cell contacts, through soluble factors or by modification of extracellular matrix components. Seminal functional studies in various cancer types, including breast, colon, prostate and lung cancer, have confirmed the concept that fibroblasts can determine the fate of the epithelial cell, since they are able to promote malignant conversion as well as to revert tumour cells to a normal phenotype. This review focuses on characteristic changes of fibroblasts in cancer and provides the experimental background elucidating functional properties of CAFs in the carcinogenic process. A possible implication in lung carcinogenesis is emphasised. Finally, a laser-capture- and microarray-based approach is presented, which comprehensively characterises carcinoma-associated fibroblasts in their in vivo environment for the identification of potential targets for anti-cancer therapy.

Quantitative analysis of Th1, Th2 and TGF-beta1 cytokine expression in tumor, TIL and PBL of non-small cell lung cancer patients

For understanding the local immune response in human non-small cell lung cancer (NSCLC), we investigated both Th1 and Th2-type as well as TGF-beta1 cytokine mRNA expression in 10 fresh tumor biopsies, the corresponding tumor and short term TIL cell lines as well as patient PBMC. A methodology based on a highly sensitive quantitative RT-PCR was used. We found that IL-6 mRNA was highly expressed in all tumor biopsy samples analyzed (4 LLC, 3 ADC and 3 SCC). IL-10 mRNA was expressed in 7 of 10 biopsies whereas IL-4 mRNA expression was moderate. Analysis of type I cytokines revealed a low expression level of IL-2 mRNA, while IFNgamma and GM-CSF expression was high in the majority of the tumor lesions studied. Quantitatively, high amounts of Th2-type cytokine mRNA were detected at the tumor site with IL-6 as the predominant lymphokine. A high mRNA expression level of the immunosuppressive cytokine TGF-beta1 was observed in all NSCLC. To identify the cell types responsible for the production of TGF-beta1, IL-6, IL-10 and GM-CSF at the tumor site, tumor and TIL cell lines were derived from the corresponding biopsies. All the 3 tumor cell lines analysed were found to express high amount of TGF-beta1 but not IL-10 mRNA, 2 expressing IL-6 and GM-CSF. Five short term TIL cell lines established in the presence of IL-2 expressed high level of IL-10, IL-4 and IFNgamma but not IL-2 mRNA. Strikingly, high expression of IL-10 mRNA was also observed in all 6 patient PBMC analyzed as compared to controls. Together, our results indicate the existence of a local and peripheral Th-2-type cytokine pattern in patients bearing NSCLC.

Migration of human glioma cells in response to tumour cyst fluids

Glial tumours often show high degrees of local invasion that lead to local recurrence of the disease. Extracellular matrix components as well as soluble factors may play a critical role in this poorly understood process. Cyst fluid from human brain tumours may accumulate such autocrine produced factors and may represent a source were those factors may be easily obtained and studied. We have studied the effect of cyst fluids harvested from 17 glial tumours, 3 meningiomas, and three metastases on the motility of established human glioma cell lines. Both cyst fluids of high grade and low grade gliomas contained varying degrees of motility enhancing activity. No such activity was identified in cyst fluids obtained from meningiomas. The relation of mitogenic and motogenic activity in three selected cyst fluids was analysed using a quantitative monolayer migration assay. Quantitative analysis of cyst fluid effects on both proliferation and migration indicate that tumour cyst fluids contain factors that strongly stimulate cell migration and that maximum stimulation of migration did not occur at concentrations optimal for cell proliferation. Our findings indicate that glial tumours in fact produce and secrete soluble factors that may contribute to their dissemination in brain tissue.

Expression of PDGF, IGF-II, bFGF and TGF-beta 1 in pulmonary adenocarcinoma

Effects of the expression of the platelet-derived growth factor (PDGF), insulin-like growth factor-II (IGF-II), basic fibroblast growth factor (bFGF) and transforming growth factor (TGF)-beta 1 were studied individually and in combinations with the clinicopathologic features and prognosis of pulmonary adenocarcinoma using paraffin embedded tissue specimens. Tumor sections from 90 patients with pulmonary adenocarcinoma were stained immunohistochemically for PDGF, IGF-II, bFGF and TGF-beta 1 by the ABC method. The survival rate was worse in patients in whom each of the four growth factors was expressed than in those where growth factors were not expressed. The reduced expression of the four growth factors correlated with less tumor aggressiveness and better prognosis of pulmonary adenocarcinoma.

Signals controlling the expression of PDGF

PDGF is an important polypeptide growth factor that plays an essential role during early vertebrate development and is associated with tissue repair and wound healing in the adult vertebrate. Moreover, PDGF is thought to play a role in a variety of pathological phenomena, such as cancer, fibrosis and atherosclerosis. PDGF is expressed as a dimer of A and/or B chains, the precursors of which are encoded by two single copy genes. Although the PDGF genes are expressed coordinately in a number of cell types, they are independently expressed in a majority of cell types. The expression of either PDGF gene can be affected by very diverse extracellular stimuli and the type of response is dependent on the cell type that is exposed to the stimulus. Expression of the PDGF chains can be modulated at every imaginable level: by regulating accessibility of the transcription start site, by varying the transcription initiation rate, by using alternative transcription start sites, by alternative splicing, by using alternative polyadenylation signals, by varying mRNA decay rates, by regulating efficiency of translation, by protein modification, and by regulating secretion. Even upon secretion, the activity of PDGF can be modulated by non-specific or specific PDGF-binding proteins. This review provides an overview of the cell types in which the PDGF genes are expressed, of the factors that are known to affect the expression of PDGF, and of the various levels at which the expression of PDGF genes can be regulated.

Usefulness of platelet-derived growth factor as a prognostic factor in pulmonary adenocarcinoma

Platelet-derived growth factor (PDGF) in the resected pulmonary adenocarcinoma tissue of 88 patients was detected immunohistochemically by the avidin-biotin-peroxidase technique to determine whether or not it is a prognostic parameter. The 88 patients were divided into PDGF (-) and PDGF (+) groups according to the stainability of the factor. The PDGF (-) group included 39 patients and the PDGF (+) group 49. The 5-year survival rate was 53% for the PDGF (-) group and 17% for the PDGF (+) group (P < 0.01). These findings indicate that the stainability of PDGF can be a prognostic parameter for pulmonary adenocarcinoma.

Nitrite/nitrate and cytokine levels in bronchoalveolar lavage fluid of lung cancer patients

BACKGROUND

Cytokines are produced by tumor cells in vitro, but evidence for in vivo increased production of cytokines in cancer patients is controversial. Conversely, nitric oxide (NO) is implicated increasingly in the mediation of cytokine effects. Lung cancer patients may show an increased local production of cytokines and NO, and chronic paracrine exposure of epithelial lung cells to these medicators may influence the production of surfactant phosphatidylcholine.

METHODS

The presence of the cytokine tumor necrosis factor (TNF alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6), as well as NO, cyclic guanosine 3'5' monophosphate (cGMP) and phosphatidylcholine levels in bronchoalveolar lavage fluid (BLF) of lung cancer patients were investigated. Bronchoalveolar lavage fluid was obtained from 30 male smokers: 22 patients with squamous cell lung cancer and 8 subjects without cancer.

RESULTS

When compared with the control subjects, the cancer patients had elevated BLF levels of TNF alpha (1.58 +/- 0.47 vs. 0.04 +/- 0.02 pg/microgram protein, P < 0.001), IL-6 (1.39 +/- 0.29 vs. 0.04 +/- 0.02 pg/microgram protein, P < 0.001), and NO2-/NO3- (23.3 +/- 5.6 vs 1.1 +/- 0.6 nmol/mg protein, P < 0.001). However, phosphatidylcholine levels were lower in those with cancer than in the control subjects (3.0 +/- 1.2 vs. 24.8 +/- 6.4 micrograms protein, P < 0.001).

CONCLUSIONS

The results showed in vivo production of inflammatory cytokines in human lung cancer and increased tumor-associated NO production, as suggested by increased levels of nitrite/nitrate in the BLF. A decreased phosphatidylcholine content in the BLF also was found in patients with lung cancer.

Tumor necrosis factor-alpha-induced inhibition of phosphatidylcholine synthesis by human type II pneumocytes is partially mediated by prostaglandins

TNF alpha seems to play an important role in the pathogenesis of adult respiratory distress syndrome. We studied the effect of TNF alpha on phospholipid synthesis by isolated type II pneumocytes and attempted to characterize the role of arachidonate metabolites and the influence of pentoxifylline on such an effect. Lung tissue obtained from both multiple organ donors (n = 14) and lung cancer patients (n = 11) was used for cell isolation. Surfactant synthesis was measured by the incorporation of D-[U-14C]glucose into phosphatidylcholine (PC). The basal PC synthesis was higher in the donor group than in the malignant group (3.44 +/- 0.19 vs 2.15 +/- 0.15 pmol/microgram protein x 120 min, P < 0.01), and, in the presence of 100 ng/ml of TNF alpha, the incorporation of labeled glucose into PC was reduced significantly in both donor (1.13 +/- 0.11 vs 3.44 +/- 0.19 pmol/microgram protein x 120 min, P < 0.01) and cancer (0.99 +/- 0.11 vs 2.15 +/- 0.15 pmol/microgram protein x 120 min, P < 0.01) groups. Indomethacin was able to completely block the cytokine-induced decrease in PC synthesis by pneumocytes from the malignant group and to attenuate the inhibitory effect of TNF alpha in those from donors, nordihydroguaiaretic acid having a similar effect. The TNF alpha effect can be blocked by pentoxifylline (100 micrograms/ml), a substance which can even succeed in reverting the basal secretory inhibition of cancer patients' pneumocytes to levels similar to those of the donor group. TNF alpha may contribute to the pathophysiology of adult respiratory distress syndrome by inhibiting the synthesis of surfactant. TNF alpha might be produced in lung tumors, resulting in chronic paracrine or systemic exposure of pneumocytes to low concentrations of the cytokine. The TNF alpha effect was not prevented completely by the blockage of the arachidonic acid metabolism, hence other mediators should also be implicated.

Expression and function of the insulin-like growth factor I system in human non-small-cell lung cancer and normal lung cell lines

In order to analyze the presence and the function of the "insulin-like growth factor I (IGF-I) system" in human non-small-cell lung cancer (N-SCLC) we tested 5 cell lines of different histological sub-types: A549, Ca-Lu-6, SK-Lu-1 (adenocarcinoma); Ca-Lu-1, SK-Mes-1 (squamous carcinoma) and one normal fibroblast-like fetal lung cell line (IMR-90) for expression of the IGF-I peptide and its RNA transcribed from the IGF-I gene; IGF-binding proteins (IGF-BP); IGF-I receptor (IGF-I-R) and its mRNA. In addition, we examined the capacity of exogenous human recombinant IGF-I to enhance the in vitro cell proliferation. In medium conditioned from cell cultures, we detected immunoreactive IGF-I material by radioimmunoassay. Western ligand blot and affinity labelling demonstrated the presence of several molecular species of IGF-BPs (IGF-BP-4, -1, -2, -3) as well. Northern blot analysis of polyA+ RNA from all cell lines examined revealed the presence of IGF-I and IGF-I-R mRNA. Moreover, binding studies on cultured cell lines showed one class of high-affinity, operative type-I IGF cell-surface binding sites. Finally, by thymidine uptake and colorimetric metabolic MTT assays, we found that most neoplastic cell lines react mitogenically to IGF-I and that its physiological effect is abolished by an anti-IGF-I-receptor antibody. These data indicate the importance of the IGF-I system in N-SCLC growth. Furthermore, they suggest that this mitogenic complex should be appraised as a possible target for anti-neoplastic drugs, antibodies or growth-factor analogues offering potential new approaches to therapy.

Reciprocal expression of pleiotrophin and midkine in normal versus malignant lung tissues

Abundant evidence suggests that growth factors are important mediators of non-small cell lung cancer (NSCLC) growth. Although multiple growth factors have been found to be produced by NSCLC tissues, little is known about possible differences in growth factor expression between malignant and adjacent normal lung tissues. Variation in growth factor expression between normal and malignant lung tissues could be potentially useful diagnostically and therapeutically. In studies reported here, the expression of the angiogenic growth factor pleiotrophin (PTN) and homolog midkine (MK) was assessed in resected normal and malignant lung tissues. Primers specific for the two growth factors were used to amplify reverse transcriptase-produced DNA copies of RNA transcripts harvested from the tissues. This analysis revealed that all normal lung tissues examined (n = 17) expressed PTN but only two expressed MK. Conversely, all of the resected lung cancers (n = 20) expressed MK but only one expressed PTN. These results demonstrated a striking reciprocal expression pattern of MK and PTN in normal versus malignant lung tissue.

Production of multiple growth factors by a human non-small cell lung carcinoma cell line

The 1PT cell line, derived from an undifferentiated bronchial carcinoma, produced, in conditioned medium, immunoreactive basic fibroblast growth factor (bFGF), insulin-like growth factors I and II (IGF-I and IGF-II), epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha), and transforming growth factor beta-2 (TGF beta 2) in its latent form, but not platelet-derived growth factor (PDGF), tumour necrosis factor alpha (TNF alpha), or transforming growth factor beta-1 (TGF beta 1). Comparative studies of growth stimulation of human umbilical vein (HUV) endothelial cells indicated that the growth factors detected in 1PT-conditioned medium do not solely account for its proliferative effects on these cells. These results support previous characterization studies [1,2] that suggest the production of a potentially novel tumour-derived endothelial cell growth factor by the 1PT cell line.

Expression of functional PDGF beta receptors in a human large-cell lung-carcinoma cell line

In this study we have investigated a panel of lung-cancer cell lines, both of small-cell carcinoma and non-small-cell type, for the expression of receptors for platelet-derived growth factor. Although we found mRNA expression for the beta-type receptor on one small-cell and one non-small-cell line and alpha-type receptor mRNA expression on one small-cell-cancer cell line, only the beta receptors of the non-small-cell line (H-157) proved to be functional. Thus, the cell line H-157 displayed specific binding of 125I-PDGF-BB in addition to mRNA expression of the 6-kb transcript for the PDGF beta type receptor. Further evidence for the presence of functional PDGF beta receptors in H-157 cells was obtained from an in vitro kinase assay, which demonstrated a ligand-induced receptor autophosphorylation as well as the phosphorylation of a number of potential substrates associated with the activated receptor.

The etiology of lung cancer

The association between tobacco smoking and lung cancer has been noted for more than 50 years and continues to dominate the etiologic milieu of this malignant disease. Other agents, many discovered in the occupational setting, have also been substantiated as lung carcinogens. Inherent predisposition to the disease has long been suspected, and recent investigations suggest several potential mechanisms and a possible mode of inheritance. Considerable progress has been made in deciphiring the molecular defects present in lung cancer cells. These recent findings have been incorporated into two well-known models of lung carcinogenesis. As the details of the carcinogenic process are unraveled, one goal is to identify intermediate (preneoplastic) markers of exposure and inherent predisposition that will help assess the risk of lung cancer for individuals as well as for groups.

Presence of elevated levels of platelet-derived growth factor (PDGF) in lung adenocarcinoma pleural effusions

Significant tumor stroma development is a specific feature of adenocarcinoma of the lung in comparison to small-cell lung cancer (SCLC). The fibrotic component of tumor stroma is thought to result from the migration and local replication of mesenchymal cells in response to the presence of cytokines. One of them, platelet-derived growth factor (PDGF), is a chemotactic and growth factor for mesenchymal cells. Since several lung adenocarcinoma cell lines, but not SCLC cell lines, have been shown in vitro to express PDGF genes, we evaluated pleural effusions for the presence of PDGF in patients with adenocarcinoma of the lung, SCLC, or nonmalignant pleural effusions. In adenocarcinoma of the lung, PDGF levels in pleural effusions were higher than in SCLC and in nonmalignant pleural effusions and were associated with the presence of a growth-promoting activity for fibroblasts due, in part, to the presence of PDGF. This observation suggests the role of PDGF in tumor stroma formation in adenocarcinoma of the lung.

Prognostic implication of transforming growth factor alpha in adenocarcinoma of the lung--an immunohistochemical study

We examined for transforming growth factor alpha (TGF alpha) in adenocarcinomatous lesions of the lung tissues excised from 138 patients, with use of the avidin-biotin-peroxidase complex (ABC) method. TGF alpha was present in the cytoplasm of the adenocarcinoma. Our objective was to determine if TGF alpha could serve as a prognostic parameter. We divided 138 patients into two groups according to the concentration of TGF alpha. Ninety-two patients had a high concentration of TGF alpha, in over 75% of the tumour cells, while 46 had a low concentration, that is in less than 75% of the cells. The 5-year survival rates of patients with high TGF alpha and low TGF alpha were 39% and 64%, respectively (P less than 0.05). Our data suggest that evidence of a high immunoreactivity of TGF alpha can serve as a prognostic parameter in adenocarcinoma of the lung.

The beta-type transforming growth factor. Mediators of cell regulation in the lung

An increased interest in the role of growth factors in the regulation of processes concerning normal and pathologic lung physiology has spurred a flurry of research in this area. Peptide growth factors are known to control not only cell proliferation but other events such as differentiation, chemotaxis, and matrix deposition as well. The transforming growth factor beta (TGF beta) family of regulatory peptides serves as a prime example to illustrate the multiplicity of effects elicited by peptide growth factors in various lung-derived cell types. At present, the TGF beta family consists of at least 17 proteins and, based on sequence analysis, they can be divided into two groups: a cluster that shows very high sequence similarity to TGF beta 1, the closely related group, and a cluster that shows weaker sequence similarity to TGF beta 1, the distantly related group. The purpose of this brief review is to summarize the salient features of TGF beta structure and regulatory abilities of the closely related group. In addition, we will outline the evidence suggesting a role for TGF beta in normal lung development and physiology. Emphasis will be placed on studies with the closely related members TGF beta 1 and TGF beta 2 because, until recently, purified protein was available only for these two proteins.

Gene amplification in human lung cancer. The myc family genes and other proto-oncogenes and growth factor genes

The development of human lung cancer may require multiple genetic deletions affecting a number of chromosomes, e.g., 1, 3, 11, 13, and 17. These genetic aberrations may induce the activation of proto-oncogenes (c-jun, ras, c-raf1) and the loss of tumor suppressor genes (p53). Some of the activated proto-oncogenes and tumor suppressor genes are more selectively expressed or absent in small-cell lung cancer (L-myc, c-myb, c-scr, Rb gene) or non-small-cell lung cancer (c-erbB-2, c-sis, c-fes). These genes may thus be of importance for selection of differentiation pathway. The c-myc oncogene is frequently amplified in small-cell lung cancer cell lines in a much higher frequency than in vivo. This indicates that c-myc seems to be related to tumor progression and a relatively late event in the lung cancer development. The uncontrolled production of multiple growth factors has been identified in human lung cancer cell lines. These factors can promote and inhibit the proliferation via paracrine and autocrine loops via specific receptors. The products from some of the activated proto-oncogenes (c-sis, c-erbB-2) are sequences homologous to a certain growth factor (PDGF) and a receptor (EGF) identified in lung cancer. The production and action of these growth factors may be of major importance for further activation of proto-oncogenes via intracellular signal transduction and specific oncogenic activation leading to further tumor progression.

Platelet-derived growth factor and its role in health and disease

Platelet-derived growth factor (PDGF) was first discovered in platelets because they are the principal source of mitogenic activity in whole blood serum for mesenchymal cells in culture. PDGF is ubiquitous in that it can be formed by a large number of normal cells as well as many varieties of transformed cells. However, its expression and biological activity appear to be controlled at a number of different levels. The molecule consists of two peptide chains (termed 'A' and 'B') and is found as one of at least three possible isoforms, (AB, AA or BB). Each of these isoforms binds to a high-affinity cell-surface receptor that is composed of two different subunits, each of which has specificity for one or the other of the peptide chains of PDGF. The two receptor subunits are present in differing amounts on different cell types, and therefore the capacity of the different isoforms of PDGF to induce mitogenesis depends on the specific PDGF isoform and the relative numbers of receptor subunits present on the responding cell. In addition to inducing cell replication, PDGF elicits a number of intracellular signals related to mitogenesis, is chemotactic, is a vasoconstrictor, activates leukocytes, and modulates extracellular matrix turnover. This growth factor is probably involved in a number of biologically important events including wound repair, embryogenesis and development, and inflammation, leading to fibrosis, atherosclerosis and neoplasia.

Growth-regulatory factors for normal, premalignant, and malignant human cells in vitro

Normal human cells, cells from nonmalignant proliferative lesions, and primary and metastatic tumor cells can be maintained in vitro and analyzed for requirements for growth in chemically defined media. The human melanocytic cell system with normal melanocytes, precursor nevus cells, and primary and metastatic melanoma cells has been extensively studied for the phenotypic properties of the cells, including their requirements for exogenous growth factors and other mitogens. In high calcium-containing W489 medium, normal melanocytes require four supplements: IGF-I (or insulin); bFGF, TPA, and alpha-MSH. Nevus cells are largely independent of bFGF. Depletion of TPA from medium is not as detrimental to nevus cells as it is to melanocytes, but the phorbol ester is still essential for maintenance of the typical nevic phenotype. Primary melanoma cells require at least one growth factor, IGF-I (or insulin), for continuous proliferation. On the other hand, metastatic cells of melanoma as well as of carcinomas of colon and rectum, bladder, ovary, and cervix are able to proliferate after a short adaptation period in medium depleted of any growth factors and other proteins. Doubling times of metastatic tumor cells in protein-free medium are only 30-60% longer than in FCS-containing medium. The growth autonomy of human tumor cells is apparently due to the endogenous production of growth factors. Likely candidates for autocrine growth stimulation of human tumor cells are TGF-alpha, TGF-beta, and PDGF. Melanoma and colorectal carcinoma cells express functional EGF/TGF-alpha receptors, and produce TGF-alpha, indicating that this growth factor is produced for autocrine stimulation. In addition to the use of anti-growth factor antibodies, other strategies for the inhibition of autocrine growth stimulation include mAbs to growth factor receptors, soluble receptors, receptor-mimicking antiidiotype antibodies, and active immunization against growth factors. Whether any of these therapeutic approaches is clinically feasible will need to be determined in extensive preclinical investigations.

Autoregulation of MeWo metastatic melanoma cell growth: characterization of intracellular (FGF, MGSA) and secreted (PDGF) growth factors

MeWo melanoma cells (clone LC1) secrete a potent mitogenic activity susceptible to reinitiate DNA replication in quiescent rodent fibroblasts (CCL39, NRK-49F, NIH-3T3) but not in BHK-21 kidney cells. This activity appears to be closely related to platelet-derived growth factor (PDGF) based on 1) its cationic nature, heat and acid resistance, but sensitivity to reducing agents; 2) its apparent molecular weight (33 kDaltons) as estimated by Biogel filtration, once dissociated from binding proteins by mild acidic treatment; 3) its weak affinity for heparin; and 4) its ability to compete with 125I-PDGF for binding to human and rodent fibroblasts, and to be recognized by anti-PDGF antibodies. Although MeWo cells coexpress the PDGF-A and PDGF-B (c-sis) chain gene transcripts, the secreted product shows reactivity on CCL39 fibroblasts more compatible with the PDGF-BB than with the PDGF-AB isoform. MeWo cell lysates contain activities that bind moderately and strongly to heparin-Sepharose, being eluted with 1.0 and 2.0 M NaCl, respectively. The latter may correspond to basic fibroblast growth factor (basic FGF), consistent with the expression of basic FGF gene mRNAs. The former has not been fully characterized and is probably not the product of the acidic FGF gene. In addition, MeWo cells react positively with the FB2 AH7 antibody, thus indicating that they elaborate material similar to melanoma growth-stimulating activity (MGSA). MeWo cells proliferate in serum-free medium in a cell-density-dependent fashion, both in liquid and semisolid cultures. Their division is modestly enhanced by basic FGF and by human and porcine PDGF but not by the factors that they release. However, the absence of demonstrable 125I-PDGF binding sites on MeWo cells, in conjunction with their lack of sensitivity to suramin growth inhibition, suggests that the secreted PDGF does not act as an autocrine factor. Instead, the autonomous proliferation of MeWo melanoma cells may result from the concerted action of basic FGF and MGSA, which are mostly cell-associated.

Production of platelet-derived growth factorlike protein(s) by a human carcinoma cell line

Human adrenal carcinoma cells (SW-13) produce and secrete autocrine growth factors. We now report that these cells secrete a factor that is biologically related to platelet-derived growth factor (PDGF). Serum-free medium conditioned by SW-13 cells stimulated incorporation of tritiated thymidine into DNA by quiescent Balb/c 3T3 cells in the presence of platelet-poor plasma. The conditioned media also competed with 125I-labeled PDGF for binding to PDGF receptors on human fibroblasts. Hybridization studies identified mRNA transcripts for PDGF-2/sis chains in logarithmically growing SW-13 cells. These data suggest secretion of PDGF-like mitogens by SW-13 cells.

Structural and functional aspects of platelet-derived growth factor and its role in the pathogenesis of glioblastoma

The platelet-derived growth factor (PDGF) family consists of three different dimeric forms, AA, BB, and AB, of the two constituent polypeptide chains, A and B. These interact with two different cell surface receptors that, in part, mediate different cellular functions. The various forms of PDGF, as well as the receptors, are expressed at high frequency in glioblastoma multiforme, and it has been suggested that the growth of this tumor might be affected by autocrine loops involving PDGF and its receptors. The present paper focuses on recent discoveries regarding the family of PDGF ligands and receptors, as well as reviews results concerning PDGF-dependent autocrine growth in experimental and spontaneous glioblastoma.

Alteration of tumour cell arrangement related to connective tissue stroma in metastatic brain tumours. Histological and immunohistochemical studies of 68 autopsy cases

Tumour cell arrangements of a variety of 68 tumours metastatic to brain parenchyma and leptomeninges were compared histologically and immunohistochemically with those of the primary tumours in regard to their connective tissue stroma. In the brain parenchyma, more than 90% of 31 metastatic differentiated adenocarcinomas from various organs changed in cell arrangement from a tubular to a papillary pattern, in which tumour cells lined the increased perivascular connective tissue, rich in both type III collagen and fibronectin, the typical constituents of interstitial type extracellular matrices. Twelve (39%) and 3 of 31 cases were rearranged in a partially or completely tubular pattern respectively, within the metastatic nodules. Most of these neoplastic tubules were surrounded by diffusely proliferating connective tissue. Metastatic growth of carcinoma cells in the absence of supporting connective tissue in the nervous tissue was rare. A similar result was obtained for differentiated squamous cell carcinoma. In contrast, metastatic undifferentiated carcinoma and tumours with some neuro-ectodermal characteristics showed a sheet-like arrangement without pronounced connective tissue proliferation, similar to that of the primary tumours. In the leptomeninges, differentiated carcinoma cells were arranged in a tubular or a squamoid pattern and were frequently accompanied by marked stromal response. These results indicate that differentiated carcinomas require connective tissue stroma for metastatic growth, and that tumour cell arrangement in the brain varies depending upon the amount and distribution of proliferating connective tissue stroma. In undifferentiated carcinomas and tumours with neuro-ectodermal characteristics lacking stromal dependency, the tumor cell arrangement remains unchanged. The degree of stromal response to metastatic tumours in the brain parenchyma is related to the degree of epithelial differentiation.

Structural characterization of the human platelet-derived growth factor A-chain cDNA and gene: alternative exon usage predicts two different precursor proteins

The human platelet-derived growth factor (PDGF) A-chain locus was characterized by restriction endonuclease analysis, and the nucleotide sequence of its exons was determined. Seven exons were identified, spanning approximately 22 kilobase pairs of genomic DNA. Alternative exon usage, identified by cDNA cloning, occurs in a human glioblastoma cell line and may give rise to two types of A-chain precursors with different C termini. The exon-intron arrangement was similar to that of the PDGF B-chain/sis locus and seemed to divide the precursor proteins into functional domains. Southern blot analysis of genomic DNA showed that a single PDGF A-chain gene was present in the human genome.

Differential expression of platelet-derived growth factor and transforming growth factor genes in small- and non-small-cell human lung carcinoma lines

We have investigated a panel of human lung cancer cell lines representing the major groups of lung cancer, i.e., small-cell carcinoma (SCC) and the group of non-SCC, consisting of squamous-cell carcinoma (SQC), adenocarcinoma (ADC) and large-cell carcinoma (LCC), for their expression of certain growth factor genes. Messenger RNA from each cell line was hybridized with probes for platelet-derived growth factor (PDGF) A- and B-chains, insulin-like growth factor (IGF)-I and -II, transforming growth factor (TGF)-alpha and -beta, epidermal growth factor (EGF) as well as a probe for the EGF receptor. All non-SCC cell lines examined showed expression of the PDGF A-chain gene. The PDGF beta-chain and TGF-beta genes were expressed in all non-SCC cell lines but one, H-125 (ADC). TGF-alpha gene expression was demonstrated in the SQC cell line U-1752, in both ADC cell lines (H-23 and H-125) and in one of the 3 LCC cell lines, U-1810. IGF-II was only transcribed in the LCC cell line U-1810. The EGF-receptor was detected in all non-SCC cell lines but one, H-661 (LCC). Neither IGF-I nor EGF transcripts could be seen in any of the 10 cell lines examined. In contrast to the non-SCC cell lines, the 4 SCC lines were constantly negative for the probes employed in this study. The frequent and heterogeneous expression of growth factor transcripts in all non-SCC studied, but not SCC-cell lines, may contribute to the difference in biological behaviour observed in vivo and in vitro between the 2 major lung cancer entities.

Characterization of the state of differentiation of six newly established human non-small-cell lung cancer cell lines

Six new non-small-cell lung cancer (NSCLC) cell lines were established directly from human tissue or indirectly via nude mouse xenografts in serum-supplemented media with success rates of 8% and 13%, respectively. They comprised one adenocarcinoma (ADLC-5M2), two squamous cell carcinomas (EPLC-32M1, EPLC-65H), two large cell carcinomas (LCLC-97TM1, LCLC-103H), and one malignant biphasic mesothelioma (MSTO-211H). All cell lines grew adherent to culture vessels with population doubling times (PDT) of 16-40 h, formed colonies in soft agarose with efficiencies of 0.1%-5.1%, and all grew in athymic nude mice. Xenograft histologies appeared as follows: (a) undifferentiated carcinomas with feeble resemblance to the original tumors in the case of adenocarcinomas and squamous cell carcinomas; (b) large cell carcinoma with high resemblance to the original tumor; (c) an undifferentiated tumor with predominance of large epithelial cells and few fibrous cells in the case of mesothelioma. Human chorionic gonadotropin (HCG) was found by radioimmunoassay and high-affinity binding sites for epidermal growth factor (EGF) by radio-receptor assay in 4/4 cell lines. A very low activity of L-DOPA decarboxylase (DDC) was detectable only in the adenocarcinoma cell line. All cell lines overexpressed the c-myc protooncogene, and no gene rearrangement or amplification was observed. Chromosome analysis revealed modal chromosome numbers of 70-73 in ADLC-5M2, EPLC-32M1, EPLC-65H, and MSTO-211H. Cell lines derived from large cell carcinoma had modal values of 65 and 170 and a wider chromosome distribution than all other cell lines. A NSCLC specific chromosomal aberration has been undetectable until now. These cell lines may aid in elucidating the biology of NSCLC and its interrelationship to other lung tumors.

Vimentin and p53 expression on epidermal growth factor receptor-positive, oestrogen receptor-negative breast carcinomas

The coordinate expression of the nuclear p53 protein, cytoplasmic intermediate filament vimentin (VIM) and membrane epidermal growth factor receptor (EGF-R) was significantly associated with oestrogen receptor immunocytochemical nuclear stain (ER-ICA) negative breast carcinomas. Twenty-three (51.1%), 26 (57.8%) and 27 (60%) of 45 ER-ICA -ve cancers were respectively p53 +ve, VIM +ve and EGF-R +ve; whereas of 151 ER-ICA +ve tumours 8 (5.3%) were p53 +ve (P less than 0.0001), 23 (15.2%) VIM +ve (P less than 0.001) and 40 (26.5%) EGF-R +ve P less than 0.001). Thirty-six of 45 (80%) ER-ICA -ve carcinomas were positive for at least one of the markers versus 55/151 (36.4%) ER-ICA +ve cases (chi 2 = 28.92, P less than 0.001). A prevalence of high grade carcinomas was found among p53 +ve, VIM +ve cases; the latter subset of tumours also had a larger mean diameter. These results suggest that ER -ve breast carcinoma cells display a coordinate expression of cell cycle-related proteins and marked changes of both the cytoskeleton and the membrane receptor repertoire.

Structural characterization of the human platelet-derived growth factor A-chain cDNA and gene: alternative exon usage predicts two different precursor proteins

The human platelet-derived growth factor (PDGF) A-chain locus was characterized by restriction endonuclease analysis, and the nucleotide sequence of its exons was determined. Seven exons were identified, spanning approximately 22 kilobase pairs of genomic DNA. Alternative exon usage, identified by cDNA cloning, occurs in a human glioblastoma cell line and may give rise to two types of A-chain precursors with different C termini. The exon-intron arrangement was similar to that of the PDGF B-chain/sis locus and seemed to divide the precursor proteins into functional domains. Southern blot analysis of genomic DNA showed that a single PDGF A-chain gene was present in the human genome.