Diffuse Malignant Mesothelioma Research Articles

Splicing modulation as novel therapeutic strategy against diffuse malignant peritoneal mesothelioma.

IntroductionTherapeutic options for diffuse malignant peritoneal mesothelioma (DMPM) are limited to surgery and locoregional chemotherapy. Despite improvements in survival rates, patients eventually succumb to disease progression. We investigated splicing deregulation both as molecular prognostic factor and potential novel target in DMPM, while we tested modulators of SF3b complex for antitumor activity.MethodsTissue-microarrays of 64 DMPM specimens were subjected to immunohistochemical assessment of SF3B1 expression and correlation to clinical outcome. Two primary cell cultures were used for gene expression profiling and in vitro screening of SF3b modulators. Drug-induced splicing alterations affecting downstream cellular pathways were detected through RNA sequencing. Ultimately, we established bioluminescent orthotopic mouse models to test the efficacy of splicing modulation in vivo.ResultsSpliceosomal genes are differentially upregulated in DMPM cells compared to normal tissues and high expression of SF3B1 correlated with poor clinical outcome in univariate and multivariate analysis. SF3b modulators (Pladienolide-B, E7107, Meayamycin-B) showed potent cytotoxic activity in vitro with IC50 values in the low nanomolar range. Differential splicing analysis of Pladienolide-B-treated cells revealed abundant alterations of transcripts involved in cell cycle, apoptosis and other oncogenic pathways. This was validated by RT-PCR and functional assays. E7107 demonstrated remarkable in vivo antitumor efficacy, with significant improvement of survival rates compared to vehicle-treated controls.ConclusionsSF3B1 emerged as a novel potential prognostic factor in DMPM. Splicing modulators markedly impair cancer cell viability, resulting also in potent antitumor activity in vivo. Our data designate splicing as a promising therapeutic target in DMPM.

Serum mesothelin as a circulating marker of diffuse malignant peritoneal mesothelioma: Preliminary study

Serum mesothelin as a circulating marker of diffuse malignant peritoneal mesothelioma: Preliminary study

Pseudomesotheliomatous Primary Squamous Cell Lung Carcinoma: The First Case Reported in Turkey and a Review of the Literature.

In rare cases, pseudomesotheliomatous tumors spread diffusely within the pleura to form an encasing mass, which may be confused with diffuse malignant mesothelioma (DMM). A 73-year-old male presented with chest pain, dyspnea and a significant loss of weight and appetite. His radiological and clinical features suggested DMM. However, immunohistochemical studies revealed a primary squamous cell cancer of the lung. To the best of our knowledge, this is the first case report of pseudomesotheliomatous primary squamous cell lung cancer in Turkey, and also the seventh case worldwide. The present report aims to present this case, along with a review of the medical literature.

The Diagnosis of Pleural Tumors Other Than Mesothelioma.

- Pleural pathology has been dominated by discussions relating to the diagnosis, prognosis, etiology, and management of malignant mesothelioma. However, there exists a diverse group of other neoplasms that involve the pleura; the most common by far is metastatic carcinoma, usually of pulmonary origin. Other metastatic tumors of varied histogenesis do occur but are less common. Primary pleural neoplasms other than diffuse malignant mesothelioma are either uncommon or rare and have received less attention. - To provide a review of those diverse tumors that can involve the pleura other than mesothelioma in order to facilitate their accurate diagnosis. - Review of relevant literature published via PubMed and other search engines. - A wide variety of tumors can involve the pleura. In most cases, the approach of considering the morphologic features with appropriate immunohistochemistry, in the correct clinical context, allows for a confident diagnosis. For a number of those soft tissue tumors that are well recognized in the pleura, such as solitary fibrous tumor, desmoid-type fibromatosis, synovial sarcoma, and epithelioid hemangioendothelioma, novel markers now exist based on an understanding of the individual tumors' molecular characteristics. Primary pleural lymphomas are rare with poor prognosis. They represent localized specific diffuse large B-cell lymphomas, with either post-germinal center B-cell or plasma cell lineage, arising in the context of either immunodeficiency or immune sequestration and with viral infection.

Dose-Dependent Effect of Red Blood Cells Transfusion on Perioperative and Long-Term Outcomes in Peritoneal Surface Malignancies Treated with Cytoreduction and HIPEC.

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are associated with increased red blood cell transfusion (RBT) demand. Although the deleterious effects of RBT are documented in various settings, its effect in this setting is obscure. In this study, we evaluated the effects of different-grade RBT on the short- and long-term outcomes of CRS and HIPEC. We analyzed 231 patients with diffuse malignant peritoneal mesothelioma (DMPM) and 273 patients with pseudomyxoma peritonei (PMP) operated in our unit. RBT was categorized according to the amount of packed red blood cell units (PRBCs) administered (0, 1-2, 3-5, > 6). The effects of RBT on long-term oncological outcomes [progression-free survival (PFS) and overall survival (OS)] were assessed by using multivariate analysis. Overall, 74% of the patients were transfused with a median of 2 PRBCs (range 0-37). Transfusion level correlated with operative time, surgical extent (as measured by the peritoneal carcinomatosis index), and age. Postoperatively, patients with major transfusion (> 6 PRBCs) had increased mortality rate (11.1%, p = 0.01) and length of hospital stay (31.2 ± 16.8days, p = 0.01) compared with other levels of RBT. RBT was dose-dependently associated with oncological outcomes in both DMPM and PMP for both PFS [hazard ratio (HR) = 1.40, 95% confidence interval (CI) 1.12-1.74, p = 0.003; HR = 1.44, 95% CI 1.15-1.81, p = 0.001, respectively] and OS (HR = 1.57, 95% CI 1.21-2.03, p = 0.001; HR = 1.43, 95% CI 1.15-1.90, p = 0.01, respectively). Our data show a dose-dependent relationship between RBT and oncological outcomes. Further research to develop transfusion sparing protocols is needed in this extensive surgical procedure.

Non-occupational exposure to asbestos is the main cause of malignant mesothelioma in women in North Jutland, Denmark.

Objectives Diffuse malignant mesothelioma (MM) is mainly caused by asbestos inhalation. The malignancy is rare among women and studies of the prevalence and causative role of non-occupational asbestos exposure among women with MM are scarce. This observational study aimed to elucidate the asbestos exposure patterns among women with MM. Methods All histological and cytological specimens from women diagnosed with MM between 1974-2015 at the Institute of Pathology, Aalborg University Hospital in Denmark, were re-evaluated. Occupational and habitation information were obtained from Danish registries and medical journals based on record linkage via the unique person ID. The number of MM cases in each parish in the region of North Jutland was determined and the incidence density in parishes was used to calculate the spatial relative risk (RR) of MM among women. Results Diagnosis of MM was confirmed in 91 women. Exposure types were classified as occupational (9%), domestic (10%), environmental (22%), combination of domestic and environmental (34%) and unknown (25%). Twenty continuous parishes formed a MM "hotspot" around the asbestos-consuming industries in the city of Aalborg. Of these, the maximum RR was found in a parish housing an asbestos factory [RR 10.5, 95% confidence interval (CI) 5.5-19.4, environmental exposure in particular RR 2.9, 95% CI 0.7-6.1]. Conclusion Non-occupational asbestos exposure is the main cause of MM and may account for up to 66% of MM cases among women in North Jutland, Denmark.

Malignant peritoneal mesothelioma in patients with endometriosis

AimsFlorid mesothelial hyperplasia is known to result from endometriosis. Well-differentiated papillary mesothelioma and multiloculated peritoneal inclusion cysts have also been described in women with endometriosis. To our knowledge, peritoneal diffuse...

Peritoneal Surface Oncology Group International (PSOGI) multicenter study on nomograms to predict overall survival in diffuse malignant peritoneal mesothelioma.

e15701Background: Diffuse malignant peritoneal mesothelioma (DMPM) is a rare disease whose therapy of choice is cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (...

Expression of plakophilin 3 in diffuse malignant pleural mesothelioma.

Diffuse malignant pleural mesothelioma (DMPM) is the most common primary malignant pleural neoplasm still posing major diagnostic, prognostic and therapeutic challenges. Plakophilins are structural proteins considered to be important for cell stability and adhesion in both tumor and normal tissues. Plakophilin 3 is a protein present in desmosomes of stratified and simple epithelia of normal tissues with presence in malignant cells of various tumors where it participates in the process of tumorigenesis. The aim of this study was to investigate the expression of plakophilin 3 protein in DMPM, but also to study its prognostic significance and relation to histologically accessible parameters of aggressive growth. Archival samples of tissue with established diagnosis of DMPM and samples of normal pleural tissue were used. Tumor samples were classified into three histological types of DMPM (epithelioid, sarcomatoid and biphasic). Additional subclassification of epithelioid mesotheliomas into nine patterns based on the prevalent histological component of the tumor was then performed. After immunohistochemical staining, cytoplasmic and membrane immunopositivity of tumor cells was assesed by scoring the intensity of the staining from 0 (no staining) to 4 (very strong staining). Prognostic value and expression of plakophilin 3 with consideration to histologically estimated aggression in tumor growth were then statistically analyzed using non- parametric tests. The results demonstrated higher level of plakophilin 3 expression in tumor samples with histologically more aggressive tumor growth, but no significant prognostic value. According to our study, plakophilin 3 appears to be involved in tumor invasion in malignant mesothelioma.

Malignant Pleural Mesothelioma with Pleural Plaques: A Case Report

Diffuse malignant mesothelioma (DMM) is an aggressive tumor of the mesothelium associated with a poor prognosis. Asbestos exposure is the major cause of the disease. Furthermore, pleural plaques are also caused by asbestos exposure. The authors present a case with malignant pleural mesothelioma and pleural plaques. Keywords: asbestos, asbestos-related diseases, mesothelioma, malignant pleural mesothelioma, pleural plaques

Mesothelin and osteopontin as circulating markers of diffuse malignant peritoneal mesothelioma: A preliminary study

BackgroundThe differential diagnosis between diffuse malignant peritoneal mesothelioma (DMPM) and other peritoneal surface malignancies (PSM) is still challenging. Serum mesothelin and osteopontin are increasingly used as markers of pleural mesothelioma, but their role in DMPM is unclear. We assessed the diagnostic and prognostic values of mesothelin, osteopontin, CEA, CA19.9, CA125, and CA15.3 in DMPM patients. MethodsMarkers were dosed before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) by enzyme-linked immunosorbent assay (ELISA) in 30 DMPM patients and 14 controls with other PSMs. Receiver-operating characteristics (ROC) curve were plotted. The performance of each marker was assessed by the area under the ROC curve (AUC-ROC). ResultsMean mesothelin levels were 7.84 ng/dl (SD = 5.14) in DMPM group and 3.00 ng/dl (SD = 1.25) in controls (P = 0.001). Mean CEA levels were 5.3 ng/dl (SD = 4.7), and 61.96 ng/dl (SD = 112.5) in the two groups (P = 0.008). No statistical difference was seen for osteopontin (P = 0.738), CA19.9 (P = 0.081), CA125 (P = 0.600), and CA15.3 (P = 0.365). AUC-ROC was 0.836 for CA19.9, 0.812 for mesothelin, 0.793 for CEA, and lower for CA125 (0.652), osteopontin (0.531), and CA15.3 (0.481). Using diagnostic cut-offs selected by ROC methodology, sensitivity, specificity, positive and negative predictive values were 70.0%, 100.0%, 100.0%, and 60.9% for mesothelin >5.21 ng/dl, and 90.0%, 85.7%, 93.1%, and 80.0% for CA19.9 < 8.8 U/dl. At multivariate analysis, osteopontin correlated with survival (hazard rate 6.46; 95%CI 1.81–23.05; P = 0.004). ConclusionWhen assessing PSMs of unknown origin, elevated mesothelin with low CA19.9 may increase the suspicion index for DMPM. Ospeopontin warrants further investigations as a prognostic marker for DMPM.

Outcomes of cytoreductive surgery with hyperthermic intraperitoneal chemotherapy for peritoneal mesothelioma and predictors of survival

Background: Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) benefits selected patients with peritoneal mesothelioma. We present the outcomes of this treatment strategy in a UK peritoneal malignancy national referral centre.Methods: Observational retrospective analysis of data prospectively collected in a dedicated peritoneal malignancy database between March 1998 and January 2016.Results: Of 1586 patients treated for peritoneal malignancy, 76 (4.8%) underwent surgery for peritoneal mesothelioma. Median age was 49 years (range 21–73 years). 34 patients (45%) were female. Of the 76 patients, 39 (51%) had low grade histological subtypes (mostly multicystic mesothelioma), and 37 (49%) had diffuse malignant peritoneal mesothelioma (DMPM; mostly epithelioid mesothelioma). Complete cytoreduction was achieved in 52 patients (68%) and maximal tumour debulking (MTD) was performed in 20 patients (26%); the remaining 4 patients (5%) underwent a laparotomy with biopsy only. HIPEC was administered in 67 patients (88%). Median overall (OS) and disease-free survival (DFS) after CRS was 97.8 (80.2–115.4) and 58.8 (47.4–70.3) months, respectively. After complete cytoreduction, 100% overall survival was observed amongst patients with low-grade disease. Ki-67 proliferation index was significantly associated with survival outcomes after complete cytoreduction for DMPM and was an independent predictor of decreased survival.Conclusion: With adequate patient selection (guided by histological classification and Ki-67 proliferation index) and complete cytoreduction with HIPEC, satisfactory outcomes can be achieved in selected patients with peritoneal mesothelioma.

Current Management and Future Opportunities for Peritoneal Metastases: Peritoneal Mesothelioma.

Diffuse malignant peritoneal mesothelioma (MPM) is a rare and ultimately fatal cancer that was first described just over a century ago. It is a diffuse malignancy arising from the mesothelial lining of the peritoneum; morbidity and mortality from MPM is due to its propensity to progress locoregionally within the abdominal cavity. The purpose of this article is to review the current state-of-the-science related to the diagnosis, staging, and treatment of MPM. The condition afflicts men and women equally and the peak incidence is between 55 and 60 years of age although it can arise in the young and elderly.Patients afflicted with MPM most commonly present with nonspecific abdominal symptoms that usually lead to diagnosis when the condition is relatively advanced. Historically, median overall survival for MPM patients without treatment is<1year. The couplet of systemic pemetrexed and cisplatin has an overall response rate of approximately 25% and a median overall survival of approximately 1year. The available data, almost all retrospective in nature, have shown that in selected patients, operative cytoreduction (CRS) and regional chemotherapy administered as hyperthermic intraoperative peritoneal chemotherapy (HIPEC) or early postoperative intraperitoneal chemotherapy (EPIC) is associated with long-term survival. Studies on the molecular biology of MPM have yielded new insights relating to the potentially important role of the phosphoinsitide-3-kinase/mammalian target of rapamycin (PI3K/mTOR) pathways and immune checkpoint inhibitors that may translate into new therapeutic options for patients with diffuse MPM.

Clinicopathologic and genetic characteristics of young patients with pleural diffuse malignant mesothelioma

Pleural diffuse malignant mesothelioma typically presents during the seventh decade of life and has poor prognosis. Recent epidemiologic studies have shown differences between young and older mesothelioma patients, but the biology of pleural mesothelioma in young patients is poorly understood. We studied the clinicopathologic and genetic characteristics in pleural mesothelioma patients aged 35 years and younger. Thirty-six consecutive pleural mesothelioma patients aged 35 years and younger were compared with 48 older patients. We examined demographic and clinical characteristics, histologic type, growth patterns, mitotic index, and nuclear grade on hematoxylin and eosin-stained slides, BAP1 protein expression by immunohistochemistry, and CDKN2A and NF2 deletions by fluorescence in situ hybridization. Clinicopathologic and cytogenetic results were compared between young and older groups, and correlated with overall survival. Young patients were more frequently women, reported less asbestos exposure, and had a greater frequency of prior therapeutic radiation and family history of breast cancer than older patients (P<0.05 each). There were no histologic differences between young and older patients (all P>0.05). CDKN2A deletion was less prevalent in young patients (P=0.01), loss of BAP1 protein expression less frequent in young patients (P=0.06), and NF2 deletion rates similar between groups (P>0.05 each). Median overall survival was 40 vs 26 months (P=0.10) in young and older patients, respectively, and 47 vs 31 months (P=0.04) when comparing patients with epithelioid histology only. High mitotic index and non-epithelioid histology were the only characteristics associated with a poor overall survival in young patients. Young patients with pleural mesothelioma have an equal sex distribution and are more likely to have a history of mantle radiation, family history of breast cancer, and lower rates of CDKN2A deletion than older patients. Our results suggest that pleural mesothelioma in young patients has distinctive clinical and genetic characteristics, despite some similarities to pleural mesothelioma in older patients.

Recurrence of Optimally Treated Malignant Peritoneal Mesothelioma with Cytoreduction and Heated Intraperitoneal Chemotherapy.

The prognosis for patients with diffuse malignant peritoneal mesothelioma has dramatically improved with cytoreductive surgery and intraperitoneal chemotherapy. Little is known about disease recurrence after treatment. We analyzed the time to and predictors of recurrence in a large cohort of optimally treated patients. We examined 113 patients completing a two-stage cytoreduction and intraperitoneal chemotherapy protocol. All patients achieved optimal surgical resection with completeness of cytoreduction (CC) score≤1 and were divided into two groups based on absence (Group A) or presence (Group B) of gross disease at the outset of the second operation. Predictors of disease recurrence and recurrence-free survival (RFS) were determined using Cox proportional hazard regression modeling, and estimates were obtained by using the Kaplan-Meier method. Forty-six percent of patients had no gross evidence of disease at the second operation; the remaining 54% were cytoreduced to CC≤1 (Group B). Forty-two percent of patients developed disease recurrence with a median recurrence-free survival of 38.5months for the cohort; 79% of these received a form of iterative treatment. There was no statistically significant difference in recurrence-free survival between Group A (median RFS: 44.6months) and B (median RFS: 35.5months) (log-rank test, p=0.06). Additionally, the only variable significantly associated with RFS was male gender (hazard ratio [HR] 1.98, 95% confidence interval [CI] 1.16-3.38). Absence of gross disease at the second operation was not statistically protective against recurrence compared with presence of quantifiable residual disease (Group B) that was effectively cytoreduced. Long-term disease surveillance is recommended, because recurrence continues years after treatment. Where a question of recurrence arises on surveillance, males may benefit from a higher degree of suspicion.

The “don't eat me” signal CD47 is a novel diagnostic biomarker and potential therapeutic target for diffuse malignant mesothelioma

ABSTRACTDiffuse malignant mesothelioma (DMM) is one of the prognostically most discouraging cancers with median survivals of only 12–22 months. Due to its insidious onset and delayed detection, DMM is often at an advanced stage at diagnosis and is considered incurable. Combined chemo- and radiotherapy followed by surgery only marginally affect outcome at the cost of significant morbidity. Because of the long time period between exposure to asbestos and disease onset, the incidence of DMM is still rising and predicted to peak around 2020. Novel markers for the reliable diagnosis of DMM in body cavity effusion specimens as well as more effective, targeted therapies are urgently needed. Here, we show that the “don't eat me” signalling molecule CD47, which inhibits phagocytosis by binding to signal regulatory protein α on macrophages, is overexpressed in DMM cells. A two-marker panel of high CD47 expression and BRCA1-associated protein 1 (BAP-1) deficiency had a sensitivity of 78% and specificity of 100% in discriminating DMM tumour cells from reactive mesothelial cells in effusions, which is superior to the currently used four-marker combination of BAP-1, glucose transporter type 1, epithelial membrane antigen and desmin. In addition, blocking CD47 inhibited growth and promoted phagocytosis of DMM cell lines by macrophages in vitro. Furthermore, DMM tumours in surgical specimens from patients as well as in a mouse DMM model expressed high levels of CD47 and were heavily infiltrated by macrophages. Our study demonstrates that CD47 is an accurate novel diagnostic DMM biomarker and that blocking CD47 may represent a promising therapeutic strategy for DMM.

Expression of ALCAM (CD166) and PD-L1 (CD274) independently predicts shorter survival in malignant pleural mesothelioma

Diffuse malignant mesothelioma of the pleura is a highly aggressive tumor typically associated with short survival. ALCAM (CD166), a type I transmembrane protein, is a member of the immunoglobulin superfamily. In normal cells, ALCAM regulates physiological processes such as angiogenesis and immune response. In cancer, it is associated with neoplastic progression, including invasion, migration, and metastasis. Furthermore, ALCAM is considered one of the cancer stem cell markers such as ALDH1 (ALDH1A1) and SALL4. The PD-L1 (CD274)/PD-1 (PDCD1, CD279) pathway is crucial for the modulation of immune responses in normal cells. Nevertheless, pathologic activation of the PD-L1/PD-1 pathway participates in immune evasion by tumor cells. Many PD-L1-expressing tumor cells have been identified in different types of cancer, including malignant mesothelioma. In this study, 175 well-characterized primary diffuse pleural mesotheliomas, including the epithelioid (n = 148), biphasic (n = 15), and sarcomatoid (n = 12) histotypes, were evaluated immunohistochemically for cancer stem cell markers (ALCAM, ALDH1, and SALL4) and PD-L1 expression. Twenty-five percent of the mesotheliomas (43/175) expressed ALCAM, whereas ALDH1 and SALL4 positivity was seen in 1% to 2% of cases. Thirty-three percent of the analyzed tumors (57/175) contained PD-L1-positive cells. Overall survival was significantly decreased in the cohort of patients with ALCAM- or PD-L1-positive tumors (both P < .01). Furthermore, the multivariate Cox hazards regression analysis identified ALCAM and PD-L1 (both P < 0.01) as potential independent risk factors. Thus, a combination of these 2 markers might be useful for prognostication and planning the treatment of patients with malignant pleural mesothelioma.

MiR-380-5p-mediated repression of TEP1 and TSPYL5 interferes with telomerase activity and favours the emergence of an \u201cALT-like\u201d phenotype in diffuse malignant peritoneal mesothelioma cells

BackgroundUnderstanding the molecular/cellular underpinnings of diffuse malignant peritoneal mesothelioma (DMPM), a fatal malignancy with limited therapeutic options, is of utmost importance for the fruitful management of the disease. In this context, we previously found that telomerase activity (TA), which accounts for the limitless proliferative potential of cancer cells, is prognostic for disease relapse and cancer-related death in DMPM patients. Consequently, the identification of factors involved in telomerase activation/regulation may pave the way towards the development of novel therapeutic interventions for the disease. Here, the capability of miR-380-5p, a microRNA negligibly expressed in telomerase-positive DMPM clinical specimens, to interfere with telomerase-mediated telomere maintenance and, hence, with cancer cell growth was assessed on preclinical models of DMPM.MethodsDMPM cells were transfected with a miR-380-5p synthetic precursor, and the effects of miRNA replacement were evaluated in terms of growing capability, induction of apoptosis and interference with TA. Reiterated weekly transfections were also performed in order to analyse the phenotype arising upon prolonged miR-380-5p reconstitution in DMPM cells.ResultsThe ectopic expression of miR-380-5p elicited a remarkable inhibition of TA and resulted in DMPM cell growth impairment and apoptosis induction. In particular, we demonstrated for the first time that these effects were the result of a molecular circuitry converging on telomerase associated protein 1 (TEP1), where the miRNA was able to target the gene both directly in unconventional targeting modality and indirectly via p53 accumulation consequent to miRNA-mediated downregulation of testis-specific protein, Y-encoded-like 5 gene. Moreover, miR-380-5p did not cause telomere attrition and cell growth arrest in long-term DMPM transfectants, which in turn showed slightly elongated telomeres and molecular features (e.g. c-circle DNA and reduced expression levels of chromatin remodeler ATRX) resembling an alternative lengthening of telomeres (ALT) phenotype.ConclusionsmiR-380-5p interferes with TA in DMPM cells by targeting TEP1. Notably, in the long-term setting, miR-380-5p-mediated impairment of TA did not result in telomere attrition. Instead, a phenotype reminiscent of ALT emerged in DMPM cells as possible compensatory pathway that safeguards DMPM cell growth, an event that may be regarded as a potential resistance mechanism to anticancer therapies based on telomerase inhibitors.

Association Between Clinicopathological Factors and Genomic Abnormalities Detected by FISH Analysis in Epithelioid Diffuse Malignant Pleural Mesothelioma.

Abnormality of genes including 9p21 is known in malignant mesothelioma and we have examined the frequency of gene deletion and amplification using the fluorescence in situ hybridization (FISH) method. We formerly reported that abnormality of the genes was more common in the sarcomatoid type than epithelioid type. In this study, we compared the clinicopathological factors including nuclear grade (NG) and genomic abnormality in epithelioid malignant pleural mesothelioma (MPM). Using paraffin-embedded tissues of 31 epithelioid MPMs, we investigated the presence of gene abnormalities in the genes 9p21, 1p36, 14q32, 22q12, 5p15, 6p, 8q24, and 7p12 by the FISH method, and compared the results with NG, clinical stage, and prognosis. In the higher NG group of epithelioid MPM, more gene amplifications [in particular 5p15 and 8q24(MYC)] were observed, and clinical stage was more advanced. Cases with the amplification of 7p12(EGFR) tended to exhibit a worse prognosis. The significant correlation between histological differentiation and clinical features such as prognosis was not confirmed. NG status in epithelioid MPM may be related to gene alteration and clinical features.

Abstract 5452: Antitumor activity of miR-34a in peritoneal mesothelioma relies on c-MET and AXL inhibition: Persistent activation of ERK and AKT signaling as a possible cytoprotective mechanism

Abstract The value of microRNAs (miRNAs) as novel targets for cancer therapy is now widely recognized. However, no information is currently available on the expression/functional role of miRNAs in diffuse malignant peritoneal mesothelioma (DMPM), a rapidly lethal disease, poorly responsive to conventional treatments, for which the development of new therapeutic strategies is urgently needed. Here, we evaluated the expression and biological effects of miR-34a -one of the most widely deregulated miRNAs in cancer and for which a lipid-formulated mimic is already clinically available- in a large cohort of DMPM clinical samples and a unique collection of in house-developed DMPM preclinical models, with the aim to assess the potential of a miR-34a-based approach for disease treatment. miR-34a was found to be significantly down-regulated in forty-five DMPM clinical specimens and five established cell lines compared to normal peritoneum. miR-34a reconstitution inhibited cell proliferation in a time-dependent manner, though to a different extent and with a different kinetics across individual cell lines. Such a variable antiproliferative effect was paralleled by a different kinetics of apoptosis induction. In addition, miR-34a ectopic expression significantly declined DMPM cell invasion ability and impaired the secretion of angiogenesis-related factors. Phenocopy experiments showed that miR-34a oncosuppressive activities mainly rely on c-MET and AXL down-regulation and the consequent interference with the activation of downstream signaling. Interestingly, a persistent activation of ERK1/2 and AKT in two miR-34a-reconstituted cell lines was found to counteract the antiproliferative and proapoptotic effects of miRNA, yet not affecting its anti-invasive activity. Most importantly, when three subcutaneous/orthotopic DMPM xenograft models were used to examine the impact of miR-34a on tumorigenicity, a significant reduction in tumor take and growth was consistently observed. Our preclinical data, showing impressive inhibitory effects induced by miR-34a on DMPM cell proliferation, invasion and growth in immunodeficient mice, strongly suggest the potential clinical utility of a miR-34a-replacement therapy for the treatment of such a still incurable disease. On the other hand, we provide the first evidence of a potential cytoprotective/resistance mechanism that may arise towards miRNA-based therapies through the persistent activation of receptor tyrosine kinase downstream signaling. Citation Format: Rihan El Bezawy, Michelandrea De Cesare, Marzia Pennati, Marcello Deraco, Paolo Gandellini, Valentina Zuco, Nadia Zaffaroni. Antitumor activity of miR-34a in peritoneal mesothelioma relies on c-MET and AXL inhibition: Persistent activation of ERK and AKT signaling as a possible cytoprotective mechanism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5452. doi:10.1158/1538-7445.AM2017-5452