Anti-EGFR antibody efficiently and specifically inhibits human TSC2-/- smooth muscle cell proliferation. Possible treatment options for TSC and LAM |
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Authors: | Lesma Elena Grande Vera Ancona Silvia Carelli Stephana Di Giulio Anna Maria Gorio Alfredo |
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Institution: | Laboratory of Pharmacology , Department of Medicine, Surgery and Dentistry- Polo H. San Paolo, Faculty of Medicine, University of Milan, Milan, Italy. elena.lesma@unimi.it |
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Abstract: | Background Tuberous sclerosis complex (TSC), a tumor syndrome caused by mutations in TSC1 or TSC2 genes, is characterized by the development of hamartomas. We previously isolated, from an angiomyolipoma of a TSC2 patient, a homogenous population of smooth muscle-like cells (TSC2?/? ASM cells) that have a mutation in the TSC2 gene as well as TSC2 loss of heterozygosity (LOH) and consequently, do not produce the TSC2 gene product, tuberin. TSC2?/? ASM cell proliferation is EGF-dependent.Methods and FindingsEffects of EGF on proliferation of TSC2?/? ASM cells and TSC2?/? ASM cells transfected with TSC2 gene were determined. In contrast to TSC2?/? ASM cells, growth of TSC2-transfected cells was not dependent on EGF. Moreover, phosphorylation of Akt, PTEN, Erk and S6 was significantly decreased. EGF is a proliferative factor of TSC2?/? ASM cells. Exposure of TSC2?/? ASM cells to anti-EGFR antibodies significantly inhibited their proliferation, reverted reactivity to HMB45 antibody, a marker of TSC2?/? cell phenotype, and inhibited constitutive phosphorylation of S6 and ERK. Exposure of TSC2?/? ASM cells to rapamycin reduced the proliferation rate, but only when added at plating time. Although rapamycin efficiently inhibited S6 phosphorylation, it was less efficient than anti-EGFR antibody in reverting HMB45 reactivity and blocking ERK phosphorylation. In TSC2?/? ASM cells specific PI3K inhibitors (e.g. {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002, wortmannin) and Akt1 siRNA had little effect on S6 and ERK phosphorylation. Following TSC2-gene transfection, Akt inhibitor sensitivity was observed.ConclusionOur results show that an EGF independent pathway is more important than that involving IGF-I for growth and survival of TSC?/? ASM cells, and such EGF-dependency is the result of the lack of tuberin. |
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