Isolation and Growth of Smooth Muscle-Like Cells Derived from Tuberous Sclerosis Complex-2 Human Renal Angiomyolipoma

Tuberous sclerosis complex (TSC) is a tumor suppressor gene disorder characterized by mutations in the TSC1 or TSC2 genes. These mutations lead to the development of benign tumors involving smooth muscle cells, causing life-threatening lymphangioleiomyomatosis. We isolated and characterized two types of cells bearing a mutation in 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 for the TSC2 gene (A+ cells) and another of nonloss of heterozygosity keratin 8/18-positive epithelial-like cells (R+ cells). Unlike control aortic vascular smooth muscle cells, A+ cells required epidermal growth factor (EGF) to grow and substituting EGF with insulin-like growth factor (IGF)-1 failed to increase the cell number; however, 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% by 5 days and 100% by 12 days. Signal transduction mediated by EGF and IGF-I receptors is therefore involved in A+ cell survival. These results may offer a novel therapeutic perspective for the treatment of TSC complications and lymphangioleiomyomatosis.