The use of nerve growth factor as a reverse transforming agent for the treatment of neurogenic tumors: in vivo results

Nerve growth factor: role in growth, differentiation and controlling cancer cell development

Recent progress in the Nerve Growth Factor (NGF) research has shown that this factor acts not only outside its classical domain of the peripheral and central nervous system, but also on non-neuronal and cancer cells. This latter observation has led to divergent hypothesis about the role of NGF, its specific distribution pattern within the tissues and its implication in induction as well as progression of carcinogenesis. Moreover, other recent studies have shown that NGF has direct clinical relevance in certain human brain neuron degeneration and a number of human ocular disorders. These studies, by suggesting that NGF is involved in a plethora of physiological function in health and disease, warrant further investigation regarding the true role of NGF in carcinogenesis. Based on our long-lasting experience in the physiopathology of NGF, we aimed to review previous and recent in vivo and in vitro NGF studies on tumor cell induction, progression and arrest. Overall, these studies indicate that the only presence of NGF is unable to generate cell carcinogenesis, both in normal neuronal and non-neuronal cells/tissues. However, it cannot be excluded the possibility that the co-expression of NGF and pro-carcinogenic molecules might open to different consequence. Whether NGF plays a direct or an indirect role in cell proliferation during carcinogenesis remains to demonstrate.

Mitogens as motogens

Numerous in vivo methodologies have documented the invasive behavior of glioma cells through normal brain parenchyma. Glioma cell locomotion has also been assessed with a number of in vitro assays including the Boyden chamber and other chemotaxis assays, colloidal gold cell tracking, analysis of migration of cells tumor cells from spheroids, confrontation cultures of glioma cells with aggregates of non-neoplastic tissue, time-lapse video microscopy, electron microscopic examination of the cytomorphologic correlates of cell motility, the radial dish assay, and quantitative enzyme immunoassay of proteins associated with invasion (e.g. laminin). Several of these techniques have been specifically modified to assess the effects of cytokines on glioma cell motility in vitro. Cytokines studied utilizing these methods include: epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), the bb dimer of platelet-derived growth factor (PDGFbb), nerve growth factor (NGF), interleukin 2 (IL-2), transforming growth factors alpha and beta 1 (TGF alpha and TGFstraat1), and tumor necrosis factor alpha (TNF alpha). This review summarizes the investigational methods used to evaluate random and directional glioma cell motility and invasion in vivo and in vitro. The roles of specific mitogens as motogens, as evaluated with these methods are then presented.

Mitogens as motogens

Numerous in vivo methodologies have documented the invasive behavior of glioma cells through normal brain parenchyma. Glioma cell locomotion has also been assessed with a number of in vitro assays including the Boyden chamber and other chemotaxis assays, colloidal gold cell tracking, analysis of migration of cells tumor cells from spheroids, confrontation cultures of glioma cells with aggregates of non-neoplastic tissue, time-lapse video microscopy, electron microscopic examination of the cytomorphologic correlates of cell motility, the radial dish assay, and quantitative enzyme immunoassay of proteins associated with invasion (e.g. laminin). Several of these techniques have been specifically modified to assess the effects of cytokines on glioma cell motility in vitro. Cytokines studied utilizing these methods include: epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), the bb dimer of platelet-derived growth factor (PDGFbb), nerve growth factor (NGF), interleukin 2 (IL-2), transforming growth factors alpha and beta 1 (TGF alpha and TGFstraat1), and tumor necrosis factor alpha (TNF alpha). This review summarizes the investigational methods used to evaluate random and directional glioma cell motility and invasion in vivo and in vitro. The roles of specific mitogens as motogens, as evaluated with these methods are then presented.

The influence of gastrin and/or cholecystokinin antagonists on the proliferation of three human astrocytic tumor cell lines

We have investigated the potential role of gastrin in the regulation of cell growth in human astrocytic tumors. To this end we have used synthetic analogs of gastrin and cholecystokinin (CCK) which behave as gastrin and/or CCK antagonists, e.g. compounds JMV-97, JMV-209 and JMV-179. Their effects on astrocytic tumor cell proliferation was investigated by the use of the colorimetric MTT assay. The in vitro biological models used in the present study included the SW1088, U87 and U373 astrocytic tumor cell lines. The results demonstrated marked influence of gastrin and CCK antagonists in the regulation of astrocytic tumor growth. This suggests that gastrin and/or CCK antagonists might be tested in experimental glioblastoma.

Gangliosides modulate the growth rate and cell phenotype of a murine primitive neuro-ectodermal tumour

Intratumoural administration of gangliosides (GSD) into a murine primitive neuro-ectodermal tumour, growing in the epicranial subcutaneous tissue of syngenic rats, results in a decrease in the tumour growth rate and causes a more differentiated phenotype of tumour cell, with immunohistochemical expression of neuronal markers. These findings suggest that the potential usefulness of intralesional administration of GSD for the control of tumours of primitive neuro-epithelial character could be considered.

Neurotensin-mediated effects on astrocytic tumor cell proliferation

Neurotensin (NT) and neurotensin receptors (NTRs) are widely found in the brain, NT may be considered as a mitogen factor in some tissues. However, no NT-mediated effects on glioma cell proliferation have been reported so far. In our present study we investigated the influence of NT on the proliferation of astrocytic tumor cell lines. To this end we used a synthetic NT agonist (JMV-449), a protease inhibitor which blocks the natural degradation of NT (JMV-531), and NT. The in vitro biological models used in the present study included the low grade SW1088, and the high grade U87, U373 and A172 astrocytic tumor cell lines. The peptide-induced influence on astrocytic tumor cell proliferation was investigated by means of the colorimetric MTT assay. Our results show that the NT and the NT agonist significantly stimulated the proliferation in 2/4 and 3/4 of the astrocytic cell lines respectively. Similarly, compound JMV-531 also induced an increase in the proliferation of 2/4 of the astrocytic cell lines. This marked influence of the NT and NT agonists, or the enzyme-endogenous prevention of its degradation on the regulation of astrocytic tumor growth therefore suggests that NT antagonists might be used to treat certain patients with high grade astrocytic tumors that do not respond to chemotherapy and/or radiotherapy.

Expression of trkA cDNA in neuroblastomas mediates differentiation in vitro and in vivo

The human trkA cDNA was transfected into a malignant human neuroblastoma (NB) cell line (HTLA230) to investigate its role in NB growth and differentiation. This cell line lacks expression of both endogenous trkA and gp75NGFR genes. Transfectants expressing the trkA mRNA and surface-bound receptors transcriptionally activate immediate-early genes (c-fos, c-jun, and jun-B) following nerve growth factor (NGF) stimulation. NGF treatment induces growth arrest as well as down-regulation of the amplified N-myc oncogene. Genes selectively expressed in mature neurons (SCG-10, ret proto-oncogene, GAP-43, etc.) are transcriptionally activated, and neurite outgrowth further demonstrates differentiation of transfectants following NGF stimulation. trkA-expressing NB cells remain tumorigenic in nude mice; however, subcutaneous treatment of tumor-bearing mice with NGF induces Schwannian and neuronal cell differentiation similar to the induction seen in human ganglioneuroblastomas. Thus, trkA expression in HTLA230 cells is sufficient to generate a functional NGF receptor complex that leads to growth-arrested and differentiated NB cells in vitro and in vivo in the presence of NGF. Hence, NGF may play a crucial role in NB cell differentiation and regression in vivo.

Characterization of the influence of anti-hormone and/or anti-growth factor neutralizing antibodies on cell clone architecture and the growth of human neoplastic astrocytic cell lines

The influence of five anti-hormone and/or anti-growth factor neutralizing antibodies on the in vitro proliferation of four human astrocytic tumor cell lines (U87, U138, U373, H4) is quantitatively described by means of a new tool which makes it possible to evaluate cell growth and cell clone architecture concomitantly. This tool relies upon the combined use of the digital cell image analyses of Feulgen-stained nuclei and the Delaunay and Voronoi mathematical triangulation and paving techniques. Of the five anti-hormone and/or anti-growth factors tested here, the anti-luteinizing hormone-releasing hormone (LHRH) antibody induced the most marked perturbation in the U138 and U373 cell lines, whereas this role was played by the anti-epidermal growth factor (EGF) antibody in the U87 and H4 cell lines. The anti-gastrin (G) antibody significantly modified the growth and/or cell clone architecture of the U138, U87 and H4 cell lines, as did the anti-transforming growth factor alpha (TGFalpha) antibody. The anti-transforming growth factor beta (TGFbeta) antibody modified the growth and/or cell clone architecture of the four cell lines under study. If the five antibodies are taken into consideration, the results strongly suggest that four (the anti-G, the anti-EGF, the anti-LHRH and the anti-TGFalpha) act as inhibitory agents on some glioma cell line proliferation, while the fifth one, i.e. the anti-TGFbeta, act as a stimulator of cell proliferation, perhaps by abrogating the inhibitory effects of TGFbeta on proliferation. A comparison of cell growth data with cell clone architecture characteristics provided further evidence of some specific influence exercised by a given hormone and/or growth factor on glioma cell proliferation. Indeed, the anti-LHRH antibody caused the most pronounced perturbations in the U138 and U373 cell clone architecture; this feature was observed in the H4 cell line and, to a lesser extent in the U87 one after the anti-EGF antibody had been used.

Expression of trkA cDNA in neuroblastomas mediates differentiation in vitro and in vivo

The human trkA cDNA was transfected into a malignant human neuroblastoma (NB) cell line (HTLA230) to investigate its role in NB growth and differentiation. This cell line lacks expression of both endogenous trkA and gp75NGFR genes. Transfectants expressing the trkA mRNA and surface-bound receptors transcriptionally activate immediate-early genes (c-fos, c-jun, and jun-B) following nerve growth factor (NGF) stimulation. NGF treatment induces growth arrest as well as down-regulation of the amplified N-myc oncogene. Genes selectively expressed in mature neurons (SCG-10, ret proto-oncogene, GAP-43, etc.) are transcriptionally activated, and neurite outgrowth further demonstrates differentiation of transfectants following NGF stimulation. trkA-expressing NB cells remain tumorigenic in nude mice; however, subcutaneous treatment of tumor-bearing mice with NGF induces Schwannian and neuronal cell differentiation similar to the induction seen in human ganglioneuroblastomas. Thus, trkA expression in HTLA230 cells is sufficient to generate a functional NGF receptor complex that leads to growth-arrested and differentiated NB cells in vitro and in vivo in the presence of NGF. Hence, NGF may play a crucial role in NB cell differentiation and regression in vivo.