Suppressive effect of asbestos on cytotoxicity of human NK cells

Asbestos, a naturally occurring fibrous mineral, causes malignant mesothelioma (MM). However, it takes a very long time to develop MM, which suggests that effects other than tumorigenicity of asbestos might contribute to the development of MM, and one of the possible targets is anti-tumor immunity. Therefore, we examined the effect of asbestos exposure on human natural killer (NK) cells using the cell line of YT-A1, Peripheral blood mononuclear cells (PBMCs) cultures and specimens from patients with MM. In particular, we focused on expression of NK cell-activating receptors, including NKG2D, 2B4 and NKp46. Analysis of the YT-CB5 subline of YT-A1, cultured with CB for over 5 months, showed a decrease in cytotoxicity with low expressions of NKG2D and 2B4, although there were no decreases after about one month. YT-CB5 showed decreases in phosphorylation of extracellular signal-regulated kinase (ERK) and degranulation stimulated by antibodies to NKG2D. Peripheral blood (PB-) NK cells from MM patients also showed decreased cytotoxicity compared with healthy volunteers (HV), and was accompanied with low expression of NKp46 unlike YT-CB5. PBMCs cultured with CB resulted in decreased expression of NKp46 on NK cells, although this did not occur when using glass wool, an asbestos substitute. These results indicate that asbestos has the potential to suppress cytotoxicity of NK cells. In particular, it is noteworthy that both NK cells from MM patients and those from a culture of PBMCs derived from HVs with asbestos showed the same characteristic of decreased cytotoxicity with low expression of NKp46.

Impairment in cytotoxicity and expression of NK cell- activating receptors on human NK cells following exposure to asbestos fibers

Asbestos is well-known for its tumorigenic activity, but its effect on anti-tumor immunity remains unclear. Therefore, we prepared a sub-line of YT-A1 human NK cells exposed to chrysotile B (CB) asbestos (YT-CB5) as an in vitro model to analyze the effect of asbestos exposure on NK cells, and examined cytotoxicity and expressions of its related molecules. The cytotoxicity of YT-CB5 against K562 cells decreased compared with the original line of YT-A1 (YT-Org). YT-CB5 exhibited significant decreases in expressions of cell surface NKG2D, 2B4 and intracellular granzyme A. YT-CB5 also exhibited a decrease in the 2B4-dependent cytotoxicity. In addition, the degranulations stimulated via cell surface NKG2D and 2B4 also decreased in YT-CB5. Therefore, peripheral blood NK cells in patients with malignant mesothelioma (MM) were examined and compared with healthy volunteers. NK cells in patients with MM also showed decreases in cytotoxicity against K562. Although the expressions of NKG2D and 2B4 did not decrease in NK cells of MM patients, the expression of cell surface NKp46 decreased. To confirm the effect of asbestos exposure on peripheral blood NK cells, PBMCs were cultured under exposure to CB. NK cells in PBMCs exposed to CB in vitro showed a significant decrease in the expression of NKp46, whereas NK cells and alter the expression of NK cell-activating receptors including NKG2D, 2B4 and NKp46 and intracellular perforin/granzymes.cells in PBMCs exposed to glass wool did not show such a decrease. These results indicate that exposure to asbestos has the potential to impair the cytotoxicity of NK cells and alter the expression of NK cell-activating receptors including NKG2D, 2B4 and NKp46 and intracellular perforin/granzymes.

Circulating tumor cells (CTCs) and endothelial cells (CECs) in primary lung cancer

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Background: Circulating tumor cell (CTC), a surrogate of distant metastasis, and circulating endothelia cell (CEC), a surrogate of angiogenesis, are potentially useful in the diagnosis of malignant tumors, but clinical significance of CTC/CEC in primary lung cancer (LC) remains unclear. Methods: A total of 342 cases who presented at our institute from August 2007 through December 2008 were included in the study. CTC/CEC in the peripheral blood (7.5mL/4.0mL) were captured and quantitatively evaluated with the “CellSearch” system without knowledge of clinical characteristics of each case. Results: In 42 (30.7%) of 137 LC cases, CTC in the peripheral blood was positive (CTC-count, more than 1 cell/7.5mL), and the maximum CTC-count was 62 cells. In 11 (18.3%) of 145 cases with non-malignant (NM) diseases, CTC was also positive; however, in NM cases, CTC-count was 1 (cell/7.5mL) in most CTC-positive cases and the maximun CTC-count was 2. Among LC cases, the incidence of case with CTC-positive (CTC-count, 1 or more) was highest in small cell carcinoma cases (7/10, 70.0%), followed by squamous cell carcinoma (9/22, 40.9%) and adenocarcinoma (23/94, 24.5%) cases; the incidence of CTC-positive case was significantly higher in stage IV cases (68.6%; p<0.001), but it should be noted that CTC was positive in 17.4% of stage I cases and 15.4% of stage II cases. The mean CEC number (/4.0mL) was significantly higher in LC cases than in NM cases (97.5 versus 52.5, respectively; p=0.023), Among LC cases, the mean CEC significantly increased along with tumor progression (mean CEC for stage I, II, III, and IV cases: 58.7, 57.9, 83.4, and 178.4, respectively; p=0.002). Conclusions: CTC and CEC are useful clinical markers in LC, and its clinical value should be validated in future clinical trials. [Table: see text]

No significant financial relationships to disclose.

Circulating tumor cells (CTCs) and endothelial cells (CECs) in the diagnosis of malignant pleural mesothelioma (MPM): A single institutional prospective study

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Background: Circulating tumor cell (CTC), a surrogate of distant metastasis, and circulating endothelia cell (CEC), a surrogate of angiogenesis, are potentially useful in the diagnosis of malignant tumors. Following a promising result of our preliminary study showing the diagnostic value of CTC/CEC in malignant pleural mesothelioma (MPM)(Tanaka F, et al. ASCO 2008), we conducted a prospective study. Methods: Patients (pts), who presented at our institute with suspicion or diagnosis of MPM, were eligible in the study. CTCs and CECs in peripheral blood (7.5mL and 4.0mL, respectively) were captured and quantitatively evaluated with the “CellSearch” system without knowledge of clinical characteristics of patients. Results: A total of 92 pts were enrolled into the study, and the final diagnosis was MPM in 68, other malignant tumors in 7, and non-malignant diseases in 17 pts ( Table ). CTC was positive (CTC-count, 1 or more per 7.5mL of the peripheral blood) in 35%(24/68) of MPM pts (range of CTC-count, 0–27 cells/7.5 mL). Among non-malignant pts, 3 pts (18%) showed a positive-CTC, but no patient showed 2 or more CTCs in 7.5mL of the peripheral blood. The mean CEC-count (/4.0mL) was significantly higher in MPM pts than in non-malignant pts (105.1 versus 40.2; p=0.047). When the cut-off value of CEC-count for the diagnosis of MPM was defined as 50(cells/4.0mL), the sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of malignant diseases were 66%, 70%, 93%, and 26%, respectively. There was no correlation between CTC-positivity and clinical stage of MPM pts, but was a trend of increase in the mean CEC-count along with tumor progression (mean CEC-count for stage I, II, III, and IV pts: 63.0, 82.4, 95.6, and 116.7, respectively). Conclusions: CTC and CEC are useful clinical markers in the diagnosis of MPM.

[Table: see text]

No significant financial relationships to disclose.

All-trans-retinoic acid inhibits tumour growth of malignant pleural mesothelioma in mice

Malignant pleural mesothelioma (MPM) is an aggressive malignant tumour of mesothelial origin associated with asbestos exposure. Because MPM has limited response to conventional chemotherapy and radiotherapy, the prognosis is very poor. Several researchers have reported that cytokines such as interleukin (IL)-6 play an important role in the growth of MPM. Previously, it was reported that all-trans-retinoic acid (ATRA) inhibited the production and function of IL-6 and transforming growth factor (TGF)-beta1 in experiments using lung fibroblasts. We investigated whether ATRA had an inhibitory effect on the cell growth of MPM, the origin of which was mesenchymal cells similar to lung fibroblasts, using a subcutaneous xenograft mouse model. We estimated the tumour growth and performed quantitative measurements of IL-6, TGF-beta1 and platelet-derived growth factor (PDGF) receptor (PDGFR)-beta mRNA levels both of cultured MPM cells and cells grown in mice with or without the administration of ATRA. ATRA significantly inhibited MPM tumour growth. In vitro studies disclosed that the administration of ATRA reduced 1) mRNA levels of TGF-beta1, TGF-beta1 receptors and PDGFR-beta, and 2) TGF-beta1-dependent proliferation and PDGF-BB-dependent migration of MPM cells. These data may provide a rationale to explore the clinical use of ATRA for the treatment of MPM.

EGFR/K-ras mutations in lung adenocarcinoma and atypical adenomatous hyperplasia (AAH)

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Background: Mutations in the epidermal growth factor receptor (EGFR) gene and k-ras gene are found in 10–30% of non-small cell lung cancer, and are useful to predict the efficacy of EGFR-tyrosine kinase inhibitors. Such mutations are also onco- developmentally important especially in lung adenocarcinoma, but the exact incidences of such mutations in adenocarcinoma/AAH and surrounding normal lung. Methods: A total of 45 consecutive patients with lung adenocarcinoma and/or AAH (18 females; mean age, 65 years) who received thoracotomy from August 2005 through December 2006. In each case, EGFR/k-ras mutations were examined in specimens cut from adenocarcinoma/AAH and normal lung; in the present study, pure bronchioalveolar carcinoma (BAC) was reviewed separately from adenocarcinoma. Results: As 12 (27%) of all 45 patients had multiple adenocarcinoma/BAC/AAH lesions, mutations were examined in 59 lesions (41 adenocarcinomas, 7 BACs, 11 AAHs) and 45 normal lung tissues. EGFR and k-ras mutations were documented in 37% (15/41) and 2% (1/41) of adenocarcinomas, and no EGFR/k-ras mutation was documented in any BAC, AAH, or normal lung tissue. Next, clinical characteristics of patients were compared between patients with solitary adenocarcionma/BAC/AAH lesion and those with multiple lesions; non-smoker were more frequently documented in multiple-lesions group (42%) than in solitary-lesion group (15%), and there was no significant difference in other characteristics such as sex and age. Conclusions: EGFR mutation was not documented in non-invasive (BAC) or pre-neoplastic (AAH) lesion in this series, which may suggest that EGFR mutation play a critical role in the development of invasive adenocarcinoma.

No significant financial relationships to disclose.

Clinicopathological features in correlation with epidermal growth factor receptor gene mutations in non-small cell lung cancer (NSCLC)

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Background: Mutations in the epidermal growth factor receptor (EGFR) gene are found in 10–30% of non-small cell lung cancer, and are useful to predict the efficacy of EGFR-tyrosine kinase inhibitors (EGFR-TKIs) such as gefitinib and erlotinib. However, it is sometimes difficult to examine such mutations. Thus, prediction of presence or absence of EGFR mutations, correlated with clinical response to EGFR-TKIs, based on clinicopathological characteristics may be important in clinical practice. Methods: We retrospectively assessed EGFR-mutation status in correlation with clinical features including FDG-PET findings and pathological features including presence or absence of bronchioalveolar component (BAC) in adenocarcinoma (Ad) case. A total of 72 consecutive patients (24 females; mean age, 65 years; 40 Ad cases) who received thoracotomy from August 2005 through October 2006 were reviewed Results: Sixteen cases (22%) had EGFR-mutations (8 cases each in exon 19 and exon 21). The incidence of EGFR-mutation was significantly higher in female (42%) or never-smoker (60%) than in male (13%) or smoker (15%). EGFR-mutation was almost exclusively found in Ad; among Ad cases, there was no significant difference in the incidence of EGFR-mutation between BAC-positive (47%) and BAC-negative cases (29%; p=0.33). Among 61 cases who received FDG-PET scan prior to thoracotomy, only 15% of EGFR- mutated cases had higher FDG-uptake, whereas 47% of EGFR-wild cases had higher FDG-uptake (p=0.36); the sensitivity and specificity of lower FDG-uptake to predict the presence of EGFR-mutations were 71% and 53%, respectively. The positive predictive value (PPV) of lower- FDG-uptake for the presence of EGFR-mutations was only 29%, but the negative predictive value (NPV) was as high as 85%. The mean standardized uptake value (SUV) of FDG for EGFR-wild patients and EGFR-mutated patients were 5.7 and 3.3, respectively (p=0.11). The mean SUV for tumors mutated in exon 19 seemed to be lower than that for tumors mutated in exon 21 (1.8 versus4.6). Conclusions: Higher FDG-uptake combined with clinical features (male and smoker) may help to exclude patients with EGFR-wild tumors who may not respond to EGFR-TKIs treatment.

No significant financial relationships to disclose.

Expression of the T cell receptor Vbeta repertoire in a human T cell resistant to asbestos-induced apoptosis and peripheral blood T cells from patients with silica and asbestos-related diseases

To explore the effects of asbestos and silica on the human immune system, an experimental model of low-dose and long-term exposure was established using a human HTLV-1-immortalized polyclonal T cell line, MT-2 (MT-2Org). MT-2 cells were continuously exposed to asbestos at a concentration (10 microg/ml) which does not induce complete cell death during short-term exposure. After acquiring resistance to CB-induced apoptosis (designated MT-2Rst), an immunological comparison was made between the MT-2Org and MT-2Rst lines in terms of T cell receptor-Vbeta (TcR-Vbeta) expression. MT-2Rst cells showed excess expression of various TcR-Vbeta, although TcR-Vbeta-overpresenting cells were characterized as undergoing apoptosis due to first contact with CB. Patients with asbestos-related diseases (ARD), such as asbestosis and malignant mesothelioma, were compared with silicosis (SIL) patients as a disease control and with healthy donors (HD). SIL and ARD not only differed in their causative materials, silica and asbestos as mineral silicates, but also in terms of complications; autoimmune disorders in SIL and tumors in ARD. ARD patients showed a restricted overpresentation of TcR-Vbeta without clonal expansion, whereas SIL patients revealed significant overpresentation of TcR-Vbeta 7.2. These experimental and clinical analyses indicate the superantigenic and dysregulation of autoimmunity-inducing effects of asbestos and silica, respectively.

[Preoperative assessment and surgical indication for malignant pleural mesothelioma]

The standard surgical procedure for patients with malignant pleural mesothelioma (MPM) is extrapleural pneumonectomy (EPP). However, high morbidity and mortality rates have been reported in patients who received EPP, whereas survival rates after EPP remain unsatisfactory. Thus, a carefully and precise preoperative assessment to select appropriate candidates for EPP is essential in patients with MPM, and we conducted a surgical staging with laparoscopy, mediastinoscopy and contralateral thoracoscopy for potentially resectable MPM patients. Among 5 consective patients who received the preoperative surgical staging during past 10 months, 1 patient was judged not to be a surgical candidate due to the presence of contralateral pleural metastasis. In conclusion, this surgical staging is a useful preoperative evaluation to prevent an unnecessary operation.