We studied immortalized cells that lack TSC2 derived from an angiomyolipoma of a patient with LAM, a TSC2 addback derivative, and murine embryonic fibroblast cells that lack Tsc1 or -2 and respective controls.
However, rapamycin further increased uPA expression in TSC2-null tumor cells and immortalized TSC2-null angiomyolipoma cells, but not in cells with intact TSC.
Phase I/II clinical trials of the mTORC1 inhibitor rapamycin have demonstrated reduction in size of tuberous-sclerosis- and LAM-associated renal tumours (angiomyolipomas) and some evidence for reversible improvement in lung function in patients with LAM.
The frequent deletion of 16p in which TSC2 gene is located indicates the oncogenetic relationship of PEComas with angiomyolipoma as a TSC2-linked neoplasm.
The exosome-mediated mechanisms may also operate in the cells of angiomyolipoma (AML), which develops as a result of mutations in TSC1/TSC2 genes in TSC patients, because we observed the reactivation of mammalian target of rapamycin and Notch pathways, driven by the delivery of Rheb and Notch1 esRNA, in AML cells depleted of Rheb that were treated with the exosomes purified from AML cells with the constitutively high Rheb levels.
We recently show that the constitutive expression of OGG1 in heterozygous (TSC2+/-) Eker rat and in angiomyolipomas kidney tissue from human is 2-3fold less than in kidney from wild-type rats and control human subjects.
Previously we found that these patients had TSC2 mutations and TSC2 LOH in their angiomyolipomas and pulmonary LAM cells but not in normal lung or kidney cells.
Tuberin (TSC2) was weak or absent in angiomyolipomas, but present in healthy kidney, whereas, phosphorylated p70 S6 kinase and p56 were present only in angiomyolipomas.
Our data demonstrate that somatic mutations in the TSC2 gene occur in the angiomyolipomas and pulmonary LAM cells of women with sporadic LAM, strongly supporting a direct role of TSC2 in the pathogenesis of this disease.
Phase I/II clinical trials of the mTORC1 inhibitor rapamycin have demonstrated reduction in size of tuberous-sclerosis- and LAM-associated renal tumours (angiomyolipomas) and some evidence for reversible improvement in lung function in patients with LAM.
The mTOR inhibitor, Rapamycin, stabilizes lung function in LAM and decreases the volume of renal angiomyolipomas, but lung function declines and angiomyolipomas regrow when treatment is discontinued, suggesting that factors induced by mTORC1 inhibition may promote the survival of TSC2-deficient cells.
Increased activation of the mTOR pathway is observed in patients and animal models of renal transplant rejection, autosomal dominant polycystic kidney disease, renal cell carcinoma, diabetic nephropathy, lupus nephritis, and angiomyolipoma.
Three types of tumors occur in TSC kidneys: (1) angiomyolipomas, which are benign tumors composed of smooth muscle, fat, and vessels; (2) epithelial cysts; and (3) malignant tumors.
Our study showed that patients with TSC2 mutations had higher frequency of hypomelanotic macules and dental enamel pits and larger angiomyolipomas (AMLs) than patient populations with non-TSC2 mutations through analysis of the correlated mutation findings with clinical features.
The high-expressing12CA repeat variant of the IFNG gene was suggested to contribute lower risk for kidney angiomyolipomas in patients with TSC2 gene mutations.
Recent work has shown that mammalian target of rapamycin complex 1 (mTORC1) inhibition caused angiomyolipoma shrinkage but that this treatment may cause cytostatic not a cytotoxic effect.