In situ analysis of mTORC1/2 and cellular metabolism–related proteins in human Lymphangioleiomyomatosis

Abstract

Lymphangioleiomyomatosis (LAM) is a rare progressive cystic lung disease with features of a low-grade neoplasm. It is primarily caused by mutations in TSC1 or TSC2 genes. Sirolimus, an inhibitor of mTOR complex 1 (mTORC1), slows down disease progression in some, but not all patients. Hitherto, other potential therapeutic targets such as mTOR complex 2 (mTORC2) and various metabolic pathways have not been investigated in human LAM tissues. The aim of this study was to assess activities of mTORC1, mTORC2 and various metabolic pathways in human LAM tissues through analysis of protein expression. Immunohistochemical analysis of p-S6 (mTORC1 downstream protein), Rictor (mTORC2 scaffold protein) as well as GLUT1, GAPDH, ATPB, GLS, MCT1, ACSS2 and CPT1A (metabolic pathway markers) were performed on lung tissue from 11 patients with sporadic LAM. Immunoreactivity was assessed in LAM cells with bronchial smooth muscle cells as controls. Expression of p-S6, Rictor, GAPDH, GLS, MCT1, ACSS2 and CPT1A was significantly higher in LAM cells than in bronchial smooth muscle cells (P<.01). No significant differences were found between LAM cells and normal bronchial smooth muscle cells in GLUT1 and ATPB expression. The results are uniquely derived from human tissue and indicate that, in addition to mTORC1, mTORC2 may also play an important role in the pathobiology of LAM. Furthermore, glutaminolysis, acetate utilization and fatty acid β-oxidation appear to be the preferred bioenergetic pathways in LAM cells. mTORC2 and these preferred bioenergetic pathways appear worthy of further study as they may represent possible therapeutic targets in the treatment of LAM.

Mutation spectrums of TSC1 and TSC2 in Chinese women with lymphangioleiomyomatosis (LAM)

“…Interestingly, 6 somatic mutations in the RICTOR gene were identified in 6 S-LAM patients separately in this study and somatic RICTOR mutations related to stomach and intestine cancers were documented in the COSMIC database. The RICTOR (rapamycin-insensitive companion of mTOR) gene encodes a core component of the mTOR complex-2 (mTORC2) and recent findings suggested that high mTORC2 activity may play a role in the pathogenesis of LAM [10,30]. Apparently, the functional significance of these RICTOR mutations need further investigation.…”

“…LAM is known to be caused by mutations in the tuberous sclerosis complex (TSC) genes, TSC1 located on chromosome 9q34 encoding hamartin or TSC2 located on chromosome 16p13 encoding tuberin [8–10]. Mutations in both hamartin and tuberin lead to inactivation of the tuberin-hamartin complex, resulting in increased activity of a kinase known as the mammalian target of rapamycin (mTOR) leading to abnormal proliferation of smooth muscle-like cells (LAM cells), the underlying causes of a variety of pathological findings.…”

In Situ Metabolic Characterisation of Breast Cancer and Its Potential Impact on Therapy

“…In case of disagreement over scoring, a third observer was also involved in the evaluation. An H-score (range: 0–300) was calculated by multiplying the staining intensity (0–3+) by the percentage of positive cells for each intensity [ 60 ]. We defined staining patterns as heterogeneous in those cases, where tumour cells were labelled with three different staining intensities simultaneously (+, ++ and +++); additionally, none of the intensity percentages reached 50% in the investigated specimens.…”

mTORC1 as a Regulator of Mitochondrial Functions and a Therapeutic Target in Cancer

“…The mTORC1 is often deregulated in numerous cancer types, such as breast, cervical cancer, esophageal squamous cell carcinoma, lung and hepatic cancers (35)(36)(37)(38)(39). mTORC1 is often activated by mutations in its upstream regulators.…”