Construction of an ecotropic retroviral vector expressing human insulin-like growth factor-I

There is increasing evidence that IGF-I plays an autocrine role in a wide range of human tumours, including, in particular, adenomas of the thyroid epithelium. To investigate this further, we set out to generate a retrovirus vector which would permit experimental manipulation of the expression of IGF-I in normal and neoplastic epithelial cells. We describe here the construction and validation of a high-titre ecotropic vector which transduces stable expression and secretion of human IGF-IA, as shown by analysis of mRNA and conditioned medium from rodent epithelial target cells. This vector should be a useful tool for assessing the contribution of abnormal IGF-I expression to the neoplastic phenotype.