High concentrations of cholecystokinin octapeptide suppress protein kinase C activity in guinea pig pancreatic acini

The in vitro influences of neurotensin on the motility characteristics of human U373 glioblastoma cells

Astrocytic tumours are associated with dismal prognoses due to their pronounced ability to diffusely invade the brain parenchyma. Various neuropeptides, including gastrin, are able to modulate tumour astrocyte migration. While neurotensin has been shown to influence the proliferation of glioma cells and the migratory ability of a large set of other cell types, its role in glioma cell migration has never been investigated. Neurotensin-induced modifications to the motility features of human U373 glioblastoma cells therefore constitute the topic of the present study. We evidenced that three subtypes of neurotensin receptors (NTR1, NTR2 and NTR3) are expressed in U373 glioblastoma cells, at least as far as their mRNAs are concerned. Treating U373 tumour cells with 10 nM neurotensin markedly modified the morphological patterns of these cells and also profoundly altered the organization of their actin cytoskeletons. Pull-down assays revealed that neurotensin induced the activation in U373 cells of both Rac1 and Cdc42 but not RhoA. Scratch wound assays evidenced that neurotensin (0.1 and 10 nM) very significantly inhibited wound colonization by U373 cells cultured in the absence of serum. In addition, quantitative phase-contrast videomicroscopy analyses showed that neurotensin decreases the motility levels of U373 glioblastoma cells when these cells are cultured on plastic. In sharp contrast, neurotensin stimulates the motility of U373 cells when they are cultured on laminin, which is a pro-adhesive extracellular matrix component ubiquitously secreted by glioma cells. Our data thus strongly suggest that, in addition to gastrin, neurotensin is a neuropeptide capable of modulating tumour astrocyte migration into the brain parenchyma.

Characterization of gastrin-induced cytostatic effect on cell proliferation in experimental malignant gliomas

OBJECTIVE

Growth patterns of astrocytic tumors can be modulated in vitro by gastrin. In this study, the influence of gastrin on the in vitro cell cycle kinetics and the in vivo growth features of three experimental malignant gliomas was investigated.

METHODS

Gastrin-induced influence on overall growth was assayed in vitro by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium colorimetric assay for human U373 and rat C6 gliomas and for rat 9L gliosarcoma. Although cell cycle analyses were performed by means of computer-assisted microscope analyses of Feulgen-stained nuclei, the gastrin-induced effects of the levels of expression of cyclins D3 and E, CDK2, CDK4, CDK5, CDK7, p15, p16, E2F1, and E2F2 were assayed by means of quantitative Western blot test. The presence of ribonucleic acids for the CCK(B) and CCK(C) gastrin receptors in the U373, C6, and 9L models was assayed by means of quantitative reverse transcriptase-polymerase chain reaction, and the presence or absence of ribonucleic acids for CCK(A) receptor was checked by means of conventional polymerase chain reaction. The influence of gastrin was also characterized in vivo in terms of the survival periods of conventional rats orthotopically grafted with the C6 and 9L models and nude rats with the U373 model.

RESULTS

Gastrin significantly decreased the overall growth rate in the rat C6 and the human U373 high-grade astrocytic tumor models with either CCK(B) or CCK(C) gastrin receptor but not in the 9L rat gliosarcoma, which had no CCK(B) gastrin receptor (but had CCK(A) receptor) and only weak amounts of CCK(C) receptor. This effect seems to occur via a cytostatic effect; that is, an accumulation of tumor astrocytes occurs in the G(1) cell cycle phase. The cytostatic effect could relate to a gastrin-induced decrease in the amounts of the cyclin D3-CDK4 complex in both C6 and U373 glioma cells. In vivo, gastrin significantly increased the survival periods of C6 and U373 glioma-bearing rats, but not of 9L gliosarcoma-bearing rats.

CONCLUSION

Gastrin is able to significantly modify the growth levels of a number of experimental gliomas.