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 Findings. Effects 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. LY294002, wortmannin) and Akt1 siRNA had little effect on S6 and ERK phosphorylation. Following TSC2-gene transfection, Akt inhibitor sensitivity was observed. Conclusion. Our 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.

Anti-EGFR Antibody Efficiently and Specifically Inhibits Human TSC2-/- Smooth Muscle Cell Proliferation. Possible Treatment Options for TSC and LAM / E. Lesma, V. Grande, S. Ancona, S. Carelli, A.M. Di Giulio, A. Gorio. - In: PLOS ONE. - ISSN 1932-6203. - 3:10(2008), p. e3558.e3558. [10.1371/journal.pone.0003558]

Anti-EGFR Antibody Efficiently and Specifically Inhibits Human TSC2-/- Smooth Muscle Cell Proliferation. Possible Treatment Options for TSC and LAM

E. Lesma
Primo
;
V. Grande
Secondo
;
S. Ancona;S. Carelli;A.M. Di Giulio
Penultimo
;
A. Gorio
Ultimo
2008

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 Findings. Effects 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. LY294002, wortmannin) and Akt1 siRNA had little effect on S6 and ERK phosphorylation. Following TSC2-gene transfection, Akt inhibitor sensitivity was observed. Conclusion. Our 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.
TSC ; phosphorylation of S6 and Erk ; anti-EGFR antibody ; rapamycin
Settore BIO/14 - Farmacologia
2008
Article (author)
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/46734
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