Evidence That Lymphangiomyomatosis Is Caused by TSC2 Mutations: Chromosome 16p13 Loss of Heterozygosity in Angiomyolipomas and Lymph Nodes from Women with Lymphangiomyomatosis

Abstract

Lymphangiomyomatosis (LAM) is a rare disease, of unknown etiology, affecting women almost exclusively. Lung transplantation is the only consistently effective therapy for LAM. Microscopically, LAM consists of a diffuse proliferation of smooth muscle cells. LAM can occur without evidence of other disease (referred to as "sporadic LAM") or in association with tuberous sclerosis complex (TSC). TSC is an autosomal dominant tumor suppressor gene syndrome characterized by seizures, mental retardation, and tumors in the brain, heart, skin, and kidney. Renal angiomyolipomas occur in approximately 50% of sporadic LAM patients and in 70% of TSC patients. Loss of heterozygosity (LOH) in the chromosomal region for the TSC2 gene occurs in 60% of TSC-associated angiomyolipomas. Because of the similar pulmonary and renal manifestations of TSC and sporadic LAM, we hypothesized that LAM and TSC have a common genetic basis. We analyzed renal angiomyolipomas, from 13 women with sporadic LAM, for LOH in the regions of the TSC1 (chromosome 9q34) and TSC2 (chromosome 16p13) genes. TSC2 LOH was detected in seven (54%) of the angiomyolipomas. We also found TSC2 LOH in four lymph nodes from a woman with retroperitoneal LAM. No TSC1 LOH was found. Our findings indicate that the TSC2 gene may be involved in the pathogenesis of sporadic LAM. However, genetic transmission of LAM has not been reported. Women with LAM may have low-penetrance germ-line TSC2 mutations, or they may be mosaic, with TSC2 mutations in the lung and the kidney but not in other organs.

Mutation analysis of the TSC1 and TSC2 genes in Japanese patients with pulmonary lymphangioleiomyomatosis

“…Thus we might have failed to detect TSC germline mutations in the remaining four TSC-LAM patients. Pathogenesis and development of sporadic LAM has been established by a series of studies by Henske's group Carsillo et al 2000;Smolarek et al 1998). First, sporadic LAM is a TSC2 disease; TSC-LAM is caused much less frequently by TSC1 mutations than by TSC2 mutations (Strizheva et al 2001).…”

“…Microsatellite markers were selected according to Smolarek et al (1998): D9S149, D9S1198, and D9S1199 for chromosome 9q34, and D16S283, D16S291, D16S525, and Kg8 for chromosome 16p13.3. PCR was performed in 10 µl of reaction buffer (10 mM Tris-HCl at pH 8.3 at 25°C, 50 mM KCl, 0.1% Triton X-100) containing 1.0 µl of DNA solution, 1-2 mM MgCl2, 200 µM dNTP, 250 nM primers, 0.25 µl of [ 32 P]α-deoxycytidine triphosphate (97.5 MBq/mmol), and 0.5 units of Taq DNA polymerase (Toyobo, Osaka, Japan).…”

“…Complete inactivation of the TSC1 gene concordant with Knudson's tumor-suppressor model (Knudson 1971) was also observed in patient LNK8 who has a TSC1 germline mutation and whose LAM cells have TSC1 LOH at D9S149 and D9S1198 markers. When exon 6 of the TSC1 gene was examined in Paraffin-embedded tissue blocks were available in 12 patients (4 patients with TSC-LAM and 8 patients with sporadic LAM) for microdissection of LAM cells followed by LOH analysis (see Material and methods) AML, renal angiomyolipomas; LN, lymph nodes a According to Smolarek et al (1998), D9S149, D9S1198, and D9S1199 were selected as microsatellite markers at chromosome 9q34 (TSC1), and D16S283, D16S291, D16S525, and Kg8 were selected at chromosome 16p13.3 (TSC2). Microsatellite markers at which allelic loss was detected are shown in this table b No allelic loss was detected but two somatic mutations in the TSC2 gene were identified (see Table 2) microdissected LAM cells, only the mutated sequence ladder was evident in LAM cells of the left lung (panel 2 in Fig.…”

“…Recent studies have indicated that angiomyolipomas and lymph nodes from patients with sporadic LAM have a TSC2 loss of heterozygosity (LOH) but not a TSC1 LOH (Smolarek et al 1998). Patients with sporadic LAM were demonstrated not to carry the TSC2 germline mutation ; inactivating mutations of the retained TSC2 allele have been demonstrated in the affected tissues but not in unaffected tissues from patients with sporadic LAM .…”

Expression profile of tuberin and some potential tumorigenic factors in 60 patients with uterine leiomyomata

“…16,17 Inactivation of either tuberous sclerosis gene 2 or tuberous sclerosis gene 1 genes leads to the formation of mostly benign neoplasms in patients with tuberous sclerosis complex. [18][19][20] The association between alteration of tuberous sclerosis complex genes and incidence of human uterine leiomyomas is unknown. This may be partly due to a high incidence of the tumor in both the general population and tuberous sclerosis complex patients.…”