Erythropoietin-driven proliferation of cells with mutations in the tumor suppressor gene TSC2

Radiotherapy Planning and Molecular Imaging in Lung Cancer

INTRODUCTION

In patients suitable for radical chemoradiotherapy for lung cancer, 18F-FDGPET/ CT is a proposed management to improve the accuracy of high dose radiotherapy. However, there is a high rate of locoregional failure in patients with locally advanced non-small cell lung cancer (NSCLC), probably due to the fact that standard dosing may not be effective in all patients. The aim of the present review was to address some criticisms associated with the radiotherapy image-guided in NSCLC.

MATERIALS AND METHODS

A systematic literature search was conducted. Only published articles that met the following criteria were included: articles, only original papers, radiopharmaceutical ([18F]FDG and any tracer other than [18F]FDG), target, only specific for lung cancer radiotherapy planning, and experimental design (eventually "in vitro" studies were excluded). Peer-reviewed indexed journals, regardless of publication status (published, ahead of print, in press, etc.) were included. Reviews, case reports, abstracts, editorials, poster presentations, and publications in languages other than English were excluded. The decision to include or exclude an article was made by consensus and any disagreement was resolved through discussion.

RESULTS

Hundred eligible full-text articles were assessed. Diverse information is now available in the literature about the role of FDG and new alternative radiopharmaceuticals for the planning of radiotherapy in NSCLC. In particular, the role of alternative technologies for the segmentation of FDG uptake is essential, although indeterminate for RT planning. The pros and cons of the available techniques have been extensively reported.

CONCLUSION

PET/CT has a central place in the planning of radiotherapy for lung cancer and, in particular, for NSCLC assuming a substantial role in the delineation of tumor volume. The development of new radiopharmaceuticals can help overcome the problems related to the disadvantage of FDG to accumulate also in activated inflammatory cells, thus improving tumor characterization and providing new prognostic biomarkers.

The Lymphangioleiomyomatosis Lung Cell and Its Human Cell Models

Lymphangioleiomyomatosis (LAM) is a multisystem disease of women, affecting lungs, kidneys, and lymphatics. It is caused by the proliferation of abnormal smooth muscle-like LAM cells, with mutations and loss of heterozygosity in the TSC1 or, more frequently, TSC2 genes. Isolated pulmonary LAM cells have been difficult to maintain in culture, and most studies of LAM lung cells involve mixtures of TSC2 wild-type and TSC2-null cells. A clonal population of LAM lung cells has not been established, making analysis of the cells challenging. Cell lines have been established from angiomyolipomas, a common manifestation of LAM, and from tumors from patients with TSC. Circulating LAM cells have also been isolated from blood and other body fluids. LAM cells may also be identified in clusters apparently derived from lymphatic vessels. Genetics, patterns of antigen expression, and signaling pathways have been studied in LAM lung tissue and in LAM cell models, although rarely all in the same study. We show here that LAM cells manifest differences in these characteristics, depending on the source investigated, suggesting further studies.

Lymphangioleiomyomatosis

Lymphangioleiomyomatosis is a rare multisystem disease predominantly affecting women that can occur sporadically or in association with tuberous sclerosis. Lung cysts progressively replace the lung parenchyma, which leads to dyspnea, recurrent pneumothorax, and in some cases respiratory failure. Patients may also have lymphatic disease in the thorax, abdomen, and pelvis, and renal angiomyolipomas. Treatment includes supportive care, bronchodilators, and for those with progressive disease, mammalian target of rapamycin (mTOR) inhibitors.

NK cell activating receptor ligand expression in lymphangioleiomyomatosis is associated with lung function decline

Lymphangioleiomyomatosis (LAM) is a rare lung disease of women that leads to progressive cyst formation and accelerated loss of pulmonary function. Neoplastic smooth muscle cells from an unknown source metastasize to the lung and drive destructive remodeling. Given the role of NK cells in immune surveillance, we postulated that NK cell activating receptors and their cognate ligands are involved in LAM pathogenesis. We found that ligands for the NKG2D activating receptor UL-16 binding protein 2 (ULBP2) and ULBP3 are localized in cystic LAM lesions and pulmonary nodules. We found elevated soluble serum ULBP2 (mean = 575 pg/ml ± 142) in 50 of 100 subjects and ULBP3 in 30 of 100 (mean = 8,300 pg/ml ± 1,515) subjects. LAM patients had fewer circulating NKG2D⁺ NK cells and decreased NKG2D surface expression. Lung function decline was associated with soluble NKG2D ligand (sNKG2DL) detection. The greatest rate of decline forced expiratory volume in 1 second (FEV₁, -124 ± 30 ml/year) in the 48 months after enrollment (NHLBI LAM Registry) occurred in patients expressing both ULBP2 and ULBP3, whereas patients with undetectable sNKG2DL levels had the lowest rate of FEV₁ decline (-32.7 ± 10 ml/year). These data suggest a role for NK cells, sNKG2DL, and the innate immune system in LAM pathogenesis.

Osteoprotegerin contributes to the metastatic potential of cells with a dysfunctional TSC2 tumor-suppressor gene

In addition to its effects on bone metabolism, osteoprotegerin (OPG), a soluble member of the tumor necrosis factor family of receptors, promotes smooth muscle cell proliferation and migration and may act as a survival factor for tumor cells. We hypothesized that these cellular mechanisms of OPG may be involved in the growth and proliferation of lymphangioleiomyomatosis (LAM) cells, abnormal smooth muscle-like cells with mutations in one of the tuberous sclerosis complex tumor-suppressor genes (TSC1/TSC2) that cause LAM, a multisystem disease characterized by cystic lung destruction, lymphatic infiltration, and abdominal tumors. Herein, we show that OPG stimulated proliferation of cells cultured from explanted LAM lungs, and selectively induced migration of LAM cells identified by the loss of heterozygosity for TSC2. Consistent with these observations, cells with TSC2 loss of heterozygosity expressed the OPG receptors, receptor activator of NF-κB ligand, syndecan-1, and syndecan-2. LAM lung nodules showed reactivities to antibodies to tumor necrosis factor-related apoptosis-inducing ligand, receptor activator of NF-κB ligand, syndecan-1, and syndecan-2. LAM lung nodules also produced OPG, as shown by expression of OPG mRNA and colocalization of reactivities to anti-OPG and anti-gp100 (HMB45) antibodies in LAM lung nodules. Serum OPG was significantly higher in LAM patients than in normal volunteers. Based on these data, it appears that OPG may have tumor-promoting roles in the pathogenesis of lymphangioleiomyomatosis, perhaps acting as both autocrine and paracrine factors.

PET imaging of tumor hypoxia using 18F-fluoroazomycin arabinoside in stage III-IV non-small cell lung cancer patients

Tumor hypoxia hampers the efficacy of radiotherapy because of its increased resistance to ionizing radiation. The aim of the present study was to estimate the potential added clinical value of the specific hypoxia tracer (18)F-fluoroazomycin arabinoside ((18)F-FAZA) over commonly used (18)F-FDG in the treatment of advanced-stage non-small cell lung cancer (NSCLC).

METHODS

Eleven patients with stage III or stage IV NSCLC underwent (18)F-FDG and (18)F-FAZA PET before chemoradiotherapy. The maximum standardized uptake value (SUVmax) was used to depict (18)F-FDG uptake, and the tumor-to-background (T/B) ratio and tumor fractional hypoxic volume (FHV) were used to quantify hypoxia. The spatial correlation between (18)F-FDG and (18)F-FAZA uptake values was investigated using voxel-based analysis. Partial-volume correction was applied.

RESULTS

All 11 patients showed clear uptake of (18)F-FAZA in the primary tumor. However, different patterns of (18)F-FDG and (18)F-FAZA uptake distributions were observed and varied widely among different tumors. No significant correlation was observed between (18)F-FDG SUVmax and (18)F-FAZA T/B ratio (P = 0.055). The median FHV of 1.4 was 48.4% (range, 5.0-91.5). A significant positive correlation was found between the (18)F-FAZA T/B ratio and FHV of 1.4 (P < 0.001). There was no correlation between the lesion size and FHV or between the (18)F-FDG SUVmax and FHV. The pattern of tumoral (18)F-FDG uptake was rather homogeneous, whereas (18)F-FAZA uptake was more heterogeneous, suggesting that (18)F-FAZA identifies hypoxic areas within metabolically active areas of tumor. A significant correlation between (18)F-FDG SUVmax and lesion size (P = 0.002) was observed.

CONCLUSION

(18)F-FAZA PET imaging is able to detect heterogeneous distributions of hypoxic subvolumes out of homogeneous (18)F-FDG background in a clinical setting. Therefore, (18)F-FAZA might be considered a tool for guiding dose escalation to the hypoxic fraction of the tumor.

Hypoxia imaging using Positron Emission Tomography in non-small cell lung cancer: implications for radiotherapy

Tumour hypoxia is an important contributor to radioresistance. Thus, increasing the radiation dose to hypoxic areas may result in improved locoregional tumour control. However, this strategy requires accurate detection of the hypoxic sub-volume using PET imaging. Secondly, hypoxia imaging may also provide prognostic information and may be of help to monitor treatment response. Therefore, a systematic review of the scientific literature was carried out on the use of Positron Emission Tomography (PET) to image Tumour hypoxia in non-small cell lung cancer (NSCLC). More specifically, the purpose of this review was (1) to summarize the different hypoxia tracers used, (2) to investigate whether Tumour hypoxia can be detected in NSCLC and finally (3) whether the presence of hypoxia can be used to predict outcome.

Current management of lymphangioleiomyomatosis

PURPOSE OF REVIEW

Lymphangioleiomyomatosis (LAM) is a rare but devastating disease, leading to chronic respiratory failure. Considerable progress for comprehension of the disease has been made when mutations of the tuberous sclerosis genes TSC1 and TSC2, were discovered in LAM cells. Therapeutic consequences of these studies are important, leading to clinical trials with sirolimus for LAM.

RECENT FINDINGS

In two studies, angiomyolipoma size decreased by 26-50% after 12 months of sirolimus treatment. In a recent 12 months controlled trial involving 89 patients with pulmonary LAM, sirolimus stopped lung function decline and improved quality of life and performance score. The protective effect of sirolimus was lost after treatment discontinuation, with a parallel lung function decline in both groups, similar to the increase in angiomyolipoma size. Sirolimus is associated with an excess of adverse events.

SUMMARY

Sirolimus represents an important drug for LAM that should be proposed to patients with a rapid alteration of lung function or with a significant clinical impairment, after individual evaluation of the risk/benefit ratio. Sirolimus seems to have a sharper effect on the reduction of abdominal masses than on lung cysts. Tolerance and safety concerns are serious limits to the long-term treatment of patients with sirolimus.