ADAM28 - Generation of a conditional ADAM28 knock-out mouse Implication of ADAM28 in metastasis dissemination

Introduction: ADAMs (a disintegrin and metalloproteinase) and ADAMTS proteinases (a disintegrin and metalloproteinase with thrombospondin motifs) are MMP (matrix metalloproteinase) -related enzymes, bearing a multi-domain structure. ADAM28 is a multipotent membrane-bound proteinase and its expression in tissues derived from the foregut in embryonic tissues suggests its involvement in the organogenesis of the respiratory tract. Moreover, ADAM28 is highly overexpressed in non-small-cell lung cancer samples. Notably through a global proteomic approach, we recently identified an upregulation of ADAM28 after induction of lung inflammation in a mouse model of asthma. In addition to data published in the literature and to our findings about ADAM28 expression in various pathological tissues, intrinsic characteristics of this proteinase argue for considering it as a potential regulator of cellular signalling pathways leading to an inflammatory pulmonary microenvironment and, eventually, to carcinogenesis. Indeed, ADAM28 bears an active catalytic domain and interacts in a non-proteolytic manner with some integrins (α4β1) and some P-selectin ligands involved in inflammatory cell migration. ADAM28 was also reported to display the capacity to cleave key mediators such as Von Willebrand factor, IGFBP3 (Insulin-like growth factor-binding protein 3) and CTGF (Connective Tissue Growth Factor). Very recently, ADAM28 was shown to shed pro-TNF-alpha suggesting an important role in tumour control. The present project aims at characterizing molecular mechanisms leading to tumour development in lungs. In the first part of this work, we intend to characterize the effects of ADAM28 depletion on physiological and pathological processes such as tumor development and metastatic dissemination in ADAM28 conditional knock-out mice. Methods: To understand the implication of ADAM28 in lung tumour development we instillated lungs of mice displaying a full knock-out genotype for ADAM28 with Lewis Lung Carcinoma cells and B16K1 melanoma cells. ADAM28 KO mice were also injected intravenously and a subcutaneously with these tumour cells. Results: There is no spontaneous phenotype for ADAM28 full knock-out animals. Preliminary results show an impaired lung tumors engrafment in ADAM28 wild type animals when compared to heterozygous or knock out littermates. Conclusion: This unique mouse strain provides a very precious tool to further investigate ADAM28 implication in various disease models including tumour growth and dissemination. The role of ADAM28 as a pro-tumor factor is widely described in the literature whereas our results suggest that ADAM28 has an anti-tumor function