Tamoxifen Suppresses the Growth of Malignant Pleural Mesothelioma Cells.

INTRODUCTION: Malignant pleural mesothelioma (MPM) is a rare but highly aggressive malignancy most often associated with exposure to asbestos. Recent evidence points to oestrogen receptor (ER)-ß having a tumour-suppressor role in MPM progression, and this raises the question of whether selective modulators of ERs could play a role in augmenting MPM therapy. MATERIALS AND METHODS: We investigated the action of tamoxifen in inhibiting the growth and modulating the cisplatin sensitivity of four MPM cell lines. RESULTS: Tamoxifen inhibited the growth of MPM cells and also modulated their sensitivity to cisplatin. The MPM cell lines expressed ERß, but the actions of tamoxifen were not blocked by antagonism of nuclear ERs. Tamoxifen treatment repressed the expression of cyclins by MPM cells, resulting in cell-cycle arrest and caspase-3-coupled apoptosis signaling. CONCLUSION: The ER-independent actions of tamoxifen on MPM cell proliferation and cell-cycle progression may have clinical benefits for a subset of patients with MPM.

Investigating palygorskite's role in the development of mesothelioma in southern Nevada: Insights into fiber-induced carcinogenicity.

Similar to asbestos fibers, nonregulated mineral fibers can cause malignant mesothelioma (MM). Recently, increased proportions of women and young individuals with MM were identified in southern Nevada, suggesting that environmental exposure to carcinogenic fibers was causing the development of MM. Palygorskite, a fibrous silicate mineral with a history of possible carcinogenicity, is abundant in southern Nevada. In this study, our aim was to determine whether palygorskite was contributing to the development of MM in southern Nevada. While palygorskite, in vitro, displayed some cytotoxicity toward primary human mesothelial (HM) cells and reduced their viability, the effects were roughly half of those observed when using similar amounts of crocidolite asbestos. No Balb/c (0/19) or MexTAg (0/18) mice injected with palygorskite developed MM, while 3/16 Balb/c and 13/14 MexTAg mice injected with crocidolite did. Lack of MM development was associated with a decreased acute inflammatory response, as injection of palygorskite resulted in lower percentages of macrophages (p = .006) and neutrophils (p = .02) in the peritoneal cavity 3 d after exposure compared to injection of crocidolite. Additionally, compared to mice injected with crocidolite, palygorskite-injected mice had lower percentages of M2 (tumor-promoting) macrophages (p = .008) in their peritoneal cavities when exposed to fiber for several weeks. Our study indicates that palygorskite found in the environment in southern Nevada does not cause MM in mice, seemingly because palygorskite, in vivo, fails to elicit inflammation that is associated with MM development. Therefore, palygorskite is not a likely contributor to the MM cases observed in southern Nevada.

Malignant pleural mesothelioma incidence and survival in the Republic of Ireland 1994-2009.

OBJECTIVE: Malignant pleural mesothelioma (MPM) is a rare malignancy associated with exposure to asbestos. The protracted latent period of MPM means that its incidence has continued to rise across Europe after the introduction of restrictions on asbestos use. In order to obtain a clearer indication of trends in the Republic of Ireland (ROI), incidence and survival were assessed based on all MPM cases reported since the establishment of the National Cancer Registry of Ireland (NCR). METHODS: NCR recorded 337 MPM diagnoses in the ROI during 1994-2009. Survival was assessed for all cases diagnosed with adequate follow-up (n=330). Crude and European age-standardized incidence rates were calculated for all cases and for 4-year periods. A Cox model of observed (all-cause) survival was used to generate hazard ratios for the effect of: gender; age at diagnosis; diagnosis cohort; region of residence; histological type; and tumour stage. Single P-values for the variables indicated were calculated using either a stratified log-rank test or stratified trend test. RESULTS: Over the study period the age-standardized MPM incidence in the ROI rose from 4.98cases per million (cpm) to 7.24cpm. The 1-year survival rate for all MPM cases was 29.6% (CI 24.7-34.6%). Excess mortality risk was associated with age at diagnosis (75-89 yrs vs. 55-64 yrs, HR 1.88, 95% CI 1.35-2.63, P<0.001) and tumour stage (III vs. I HR 1.57, 95% CI 1.00-2.48, P<0.05; IV vs. I HR 1.55, 95% CI 1.08-2.21, P<0.05). Age showed a significant survival trend (P<0.001) but tumour stage did not (P=0.150). There was significant heterogeneity between the survival of patients resident in different regions (P=0.027). CONCLUSION: MPM incidence and mortality continued to rise in the ROI after the restrictions on asbestos use and the predictors of survival detected in this study are broadly consistent with those identified for other countries.

Sustained expression of steroid receptor coactivator SRC-2/TIF-2 is associated with better prognosis in malignant pleural mesothelioma.

INTRODUCTION: Estrogen receptor beta (ERß) overexpression by malignant pleural mesothelioma (MPM) tumor cells correlates with enhanced patient survival. ER-regulated transcription is mediated by the p160 family of steroid receptor coactivators (SRCs), and SRC isoform overexpression is associated with worse prognosis in many steroid-related malignancies. The aim of this study was to establish whether SRC isoform expression varied between individual MPM tumors with positive or negative prognostic significance. METHODS: Immunohistochemical analysis of tumor biopsies from 89 subjects with confirmed histological diagnosis of MPM and biopsies from 3 normal control subjects was performed to detect the expression of SRC-1, SRC-2 (TIF-2), SRC-3 (AIB-1), and ERß. Allred scores for expression of ERß and each of the SRCs were determined, and Kaplan-Meier survival curves were calculated to correlate biomarker expression, gender, and histology type with postdiagnosis survival. RESULTS: ERß and all the SRCs were expressed at high levels in normal pleural mesothelium, and expression of each biomarker was reduced or lost in a subset of the MPM subjects; however, postdiagnosis survival only significantly correlated with TIF-2 expression. Low or intermediate expression of TIF-2 correlated with reduced median postdiagnosis survival (9 months) compared with those subjects whose tumors highly expressed TIF-2 (20 months) (p = 0.036, log-rank test). CONCLUSIONS: Maintained high expression of TIF-2 in tumor cells is a positive prognostic indicator for postdiagnosis survival in patients with confirmed MPM. This is the first clinical study to correlate high TIF-2 expression with improved patient prognosis in any malignancy.