Isolation and growth of smooth muscle-like cells derived from tuberous sclerosis complex-2 human renal angiomyolipoma : epidermal growth factor is the required growth factor

Tuberous sclerosis complex (TSC) is a tumour suppressor gene disorder characterized by mutations in the TSC1 or TSC2 genes that leads to the development of benign tumours involving smooth muscle cells, which are also responsible for life-threatening lymphangioleiomyomatosis (LAM). We isolated and characterized two types of cell bearing a mutation on TSC2 exon 18 from a renal angiomyolipoma of a TSC patient: one population of α-actin-positive smooth muscle-like cells with loss of heterozygosity (LOH) for the TSC2 gene (A+ cells), and another of non-LOH keratin 8-18-positive epithelial-like cells. Unlike control aorta smooth muscle cells, A+ cells required EGF to grow and substituting EGF with IGF-1 failed to increase the cell number; omission of EGF did not cause cell loss. The A+ cells constantly released IGF-1 into the culture medium and constitutively showed a high degree of S6K phosphorylation even when grown in serum-free medium. Exposure to antibodies against EGF and IGF-1 receptors caused a rapid loss of A+ cells: 50% in five days and 100% in twelve. Signal transduction mediated by EGF and IGF-I receptors is therefore involved in cell survival. The results of this study may offer a novel therapeutic perspective for the treatment of TSC complications and LAM.