Glial cell line-derived neurotrophic factor promotes invasive behaviour in testicular seminoma cells.
ABSTRACT The glial cell line-derived neurotrophic factor (GDNF) has multiple functions that promote cell survival, proliferation and migration in different cell types. The experimental over-expression of GDNF in mouse testis leads to infertility and promotes seminomatous germ cell tumours in older animals, which suggests that deregulation of the GDNF pathway may be implicated in germ cell carcinogenesis. GDNF activates downstream pathways upon binding to its specific co-receptor GDNF family receptor-a 1 (GFRA1). This complex then interacts with Ret and other co-receptors to activate several intracellular signalling cascades. To explore the involvement of the GDNF pathway in the onset and progression of testicular germ cell tumours, we analysed GFRA1 and Ret expression patterns in seminoma samples. We demonstrated, via immunohistochemistry, that GFRA1, but not Ret, is over-expressed in in situ carcinoma (CIS) and in intratubular and invasive seminoma cells compared with normal human germ cells. Functional analysis of the GDNF biological activity was performed on TCam-2 seminoma cell line. Reverse transcription-PCR (RT-PCR) and immunohistochemical analyses demonstrate that TCam-2 cells express both GFRA1 and Ret mRNA, but only GFRA1 was detected at the protein level. In TCam-2 cells, although GDNF is not mitogenic, it is able to induce migration, as demonstrated by a Boyden chamber assay, possibly through the Src and MEK pathways. Moreover, GDNF promotes invasive behaviour, an effect dependent on pericellular protease activity, possibly through the activity of matrix metalloproteinases. GFRA1 over-expression in CIS and seminoma cells, along with the functional analyses in TCam-2 cells, suggests an involvement of the GDNF pathway in the progression of testicular germ cell cancer.
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ABSTRACT: Invasive tumor dissemination in vitro and in vivo involves the proteolytic degradation of ECM barriers. This process, however, is only incompletely attenuated by protease inhibitor-based treatment, suggesting the existence of migratory compensation strategies. In three-dimensional collagen matrices, spindle-shaped proteolytically potent HT-1080 fibrosarcoma and MDA-MB-231 carcinoma cells exhibited a constitutive mesenchymal-type movement including the coclustering of beta 1 integrins and MT1-matrix metalloproteinase (MMP) at fiber bindings sites and the generation of tube-like proteolytic degradation tracks. Near-total inhibition of MMPs, serine proteases, cathepsins, and other proteases, however, induced a conversion toward spherical morphology at near undiminished migration rates. Sustained protease-independent migration resulted from a flexible amoeba-like shape change, i.e., propulsive squeezing through preexisting matrix gaps and formation of constriction rings in the absence of matrix degradation, concomitant loss of clustered beta 1 integrins and MT1-MMP from fiber binding sites, and a diffuse cortical distribution of the actin cytoskeleton. Acquisition of protease-independent amoeboid dissemination was confirmed for HT-1080 cells injected into the mouse dermis monitored by intravital multiphoton microscopy. In conclusion, the transition from proteolytic mesenchymal toward nonproteolytic amoeboid movement highlights a supramolecular plasticity mechanism in cell migration and further represents a putative escape mechanism in tumor cell dissemination after abrogation of pericellular proteolysis.The Journal of Cell Biology 02/2003; 160(2):267-77. · 10.82 Impact Factor
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ABSTRACT: The variety of diseases caused by mutations in RET receptor tyrosine kinase provides a classic example of phenotypic heterogeneity. Gain-of-function mutations of RET are associated with human cancer. Gene rearrangements juxtaposing the tyrosine kinase domain to heterologous gene partners have been found in sporadic papillary carcinomas of the thyroid (PTC). These rearrangements generate chimeric RET/PTC oncogenes. In the germline, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN 2A and 2B) and familial medullary thyroid carcinoma (FMTC). Both MEN 2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, activate the RET downstream targets. Loss-of-function mutations of RET cause Hirschsprung's disease (HSCR) or colonic aganglionosis. A deeper understanding of the molecular signaling of normal versus abnormal RET activity in cancer will enable the development of potential new treatments for patients with sporadic and inherited thyroid cancer or MEN 2 syndrome. We now review the role and mechanisms of RET signaling in development and carcinogenesis.Cytokine & Growth Factor Reviews 01/2005; 16(4-5):441-67. · 8.83 Impact Factor
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ABSTRACT: For at least 30 years, matrix metalloproteinases (MMPs) have been heralded as promising targets for cancer therapy on the basis of their massive up-regulation in malignant tissues and their unique ability to degrade all components of the extracellular matrix. Preclinical studies testing the efficacy of MMP suppression in tumor models were so compelling that synthetic metalloproteinase inhibitors (MPIs) were rapidly developed and routed into human clinical trials. The results of these trials have been disappointing. Here we review the studies that brought MPIs into clinical testing and discuss the design and outcome of the trials in light of new information about the cellular source, substrates, and mode of action of MMPs at different stages of tumor progression. The important lessons learned from the MPI experience may be of great value for future studies of MPIs and for cancer drug development in general.Science 04/2002; 295(5564):2387-92. · 31.20 Impact Factor