Medical treatment of mesothelioma: anything new?

Drug Regimen for Patients after a Pneumonectomy

Pneumonectomy is an entire lung removal and is indicated for both malignant and benign diseases. Due to its invasiveness and postoperative complications, pneumonectomy is still associated with high mortality and morbidity. Appropriate postoperative management is crucial in pneumonectomy patients to improve quality of life and overall survival rates. Diverse drug regimens are under development to be used in adjuvant chemotherapy or to improve respiratory health after a pneumonectomy. The most common causes for a pneumonectomy are non-small cell lung cancer, malignant pleural mesothelioma, and tuberculosis; thus, an appropriate drug regimen is necessary. The uncommon incidence of pneumonectomy cases remains the major obstacle in studies of postoperative drug regimens. As the majority of current studies include post-lobectomy and post-segmentectomy patients, it is highly recommended that further research of postoperative drug regimens be focused on post-pneumonectomy patients.

Targeting ROR1 in combination with pemetrexed in malignant mesothelioma cells

OBJECTIVE

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is overexpressed in a subset of malignant cells. However, it remains unknown whether ROR1 is targetable in malignant mesothelioma (MM). Therefore, in this study, we investigated the effects of ROR1 inhibition in mesothelioma cells.

MATERIALS AND METHODS

Growth inhibition, colony formation, apoptosis, and mRNA/protein levels using siRNA-transfected MM cells were evaluated. Cluster analysis using Gene Expression Omnibus repository of transcriptomic information was also performed.

RESULTS

Our results indicated that in three (H2052, H2452, and MESO-1) among four MM cell lines, ROR1 inhibition had anti-proliferative and apoptotic effects and suppressed the activation of AKT and STAT3. Although growth inhibition by siROR1 was minimal in another mesothelioma cell line (H28), colony formation was significantly suppressed. Microarray, quantitative polymerase chain reaction, and Western blot analyses showed that there were differences in the suppression of mRNA and proteins between H2452 and H28 cells transfected with siROR1 compared with those transfected with control siRNA. Cluster analysis further showed that MM tumors had relatively high ROR1 expression, although the cluster in them was different from that in MM cell lines. Thymidylate synthase, a target of pemetrexed, was downregulated in H2452 cells transfected with siROR1. Accordingly, a combination of pemetrexed with siROR1 was found to be effective in the three MM cell lines we studied.

CONCLUSION

Our findings may provide novel therapeutic insight into the treatment of advanced MM.

Whole exome and targeted deep sequencing identify genome-wide allelic loss and frequent SETDB1 mutations in malignant pleural mesotheliomas

Malignant pleural mesothelioma (MPM), a rare malignancy with a poor prognosis, is mainly caused by exposure to asbestos or other organic fibers, but the underlying genetic mechanism is not fully understood. Genetic alterations and causes for multiple primary cancer development including MPM are unknown. We used whole exome sequencing to identify somatic mutations in a patient with MPM and two additional primary cancers who had no evidence of venous, arterial, lymphovascular, or perineural invasion indicating dissemination of a primary lung cancer to the pleura. We found that the MPM had R282W, a key TP53 mutation, and genome-wide allelic loss or loss of heterozygosity, a distinct genomic alteration not previously described in MPM. We identified frequent inactivating SETDB1 mutations in this patient and in 68 additional MPM patients (mutation frequency: 10%, 7/69) by targeted deep sequencing. Our observations suggest the possibility of a new genetic mechanism in the development of either MPM or multiple primary cancers. The frequent SETDB1 inactivating mutations suggest there could be new diagnostic or therapeutic options for MPM.

Reactive oxygen species a double-edged sword for mesothelioma

It is well known that oxidative stress can lead to chronic inflammation which, in turn, could mediate most chronic diseases including cancer. Oxidants have been implicated in the activity of crocidolite and amosite, the most powerful types of asbestos associated to the occurrence of mesothelioma. Currently rates of mesothelioma are rising and estimates indicate that the incidence of mesothelioma will peak within the next 10-15 years in the western world, while in Japan the peak is predicted not to occur until 40 years from now. Although the use of asbestos has been banned in many countries around the world, production of and the potentially hazardous exposure to asbestos is still present with locally high incidences of mesothelioma. Today a new man-made material, carbon nanotubes, has arisen as a concern; carbon nanotubes may display 'asbestos-like' pathogenicity with mesothelioma induction potential. Carbon nanotubes resulted in the greatest reactive oxygen species generation. How oxidative stress activates inflammatory pathways leading to the transformation of a normal cell to a tumor cell, to tumor cell survival, proliferation, invasion, angiogenesis, chemoresistance, and radioresistance, is the aim of this review.

Hesperidin Induces Apoptosis by Inhibiting Sp1 and Its Regulatory Protein in MSTO-211H Cells

Hesperidin, a flavanone present in citrus fruits, has been studied as potential therapeutic agents that have anti-tumor activity and apoptotic effects in several cancers, but there is no report about the apoptotic effect of hesperidin in human malignant pleural mesothelioma through the specificity protein 1 (Sp1) protein. We investigated whether hesperidin inhibited cell growth and regulated Sp1 target proteins by suppressing the levels of Sp1 protein in MSTO-211H cells. The IC50 value of hesperidin was determined to be 152.3 μM in MSTO-211H cells for 48 h. Our results suggested that hesperidin (0-160 μM) decreased cell viability, and induced apoptotic cell death. Hesperidin increased Sub-G1 population in MSTO-211H cells. Hesperidin significantly suppressed mRNA/protein level of Sp1 and modulated the expression level of the Sp1 regulatory protein such as p27, p21, cyclin D1, Mcl-1, and survivin in mesothelioma cells. Also, hesperidin induced apoptotic signaling including: cleavages of Bid, caspase-3, and PARP, upregulation of Bax, and down-regulation of Bcl-xl in mesothelioma cells. These results show that hesperidin suppressed mesothelioma cell growth through inhibition of Sp1. In this study, we demonstrated that Sp1 acts as a novel molecular target of hesperidin in human malignant pleural mesothelioma.

Targeting the intracellular WT1 oncogene product with a therapeutic human antibody

The Wilms tumor 1 (WT1) oncoprotein is an intracellular, oncogenic transcription factor that is overexpressed in a wide range of leukemias and solid cancers. RMFPNAPYL (RMF), a WT1-derived CD8+ T cell human leukocyte antigen (HLA)-A0201 epitope, is a validated target for T cell-based immunotherapy. Using phage display technology, we discovered a fully human "T cell receptor-like" monoclonal antibody (mAb), ESK1, specific for the WT1 RMF peptide/HLA-A0201 complex. ESK1 bound to several leukemia and solid tumor cell lines and primary leukemia cells, in a WT1- and HLA-A0201-restricted manner, with high avidity [dissociation constant (Kd)=0.1 nM]. ESK1 mediated antibody-dependent human effector cell cytotoxicity in vitro. Low doses of naked ESK1 antibody cleared established, disseminated, human acute lymphocytic leukemia and Philadelphia chromosome-positive leukemia in nonobese diabetic/severe combined immunodeficient γc-/- (NSG) mouse models. At therapeutic doses, no toxicity was seen in HLA-A0201 transgenic mice. ESK1 is a potential therapeutic agent for a wide range of cancers overexpressing the WT1 oncoprotein. This finding also provides preclinical validation for the strategy of developing therapeutic mAbs targeting intracellular oncogenic proteins.

Role of new radiation techniques in the treatment of pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm arising from the surface serosal cells of the pleural cavity. Surgery remains the main therapeutic standard in the treatment of MPM with the goal of complete gross cytoreduction of the tumor. Because MPM is a diffuse disease affecting the entire mesothelial lining of the hemithorax, surgery alone can rarely achieve adequate tumor-free resection margins. The surgical choices are pleurectomy/decortication (P/D) or extrapleural pneumonectomy (EPP). Radiotherapy (RT) is usually applied postoperatively with the aim to improve local control. However, the efficacy of RT is limited by the large volume of the target to be irradiated (tumor and pleural cavity) and the radiosensitivity of the nearby organs (heart, liver, lung, spinal cord, and esophagus). These factors have historically limited the effective radiation doses that can be given to the patient. There is no role for radical RT alone, but the role of RT as part of multimodality therapy is discussed. After EPP adjuvant RT to the entire hemithorax can reduce the recurrence rate and is well tolerated if strict limits to the dose to contralateral lung are applied: the V20 and V5 (the percent volume of the lung receiving more than 20Gy and 5Gy of radiation) correlate with increased lung toxicity. The use of modern sophisticated techniques allows good target coverage, more conformal high dose delivery, and clinically relevant normal tissue sparing.