Expression and regulation of B7-H3 immunoregulatory receptor, in human mesothelial and mesothelioma cells: immunotherapeutic implications.
ABSTRACT No treatment prolongs the survival of malignant mesothelioma (MM) patients. Since MM elicits anti-tumor host's immune responses, immunotherapy represents a promising strategy for its control. Immunomodulatory antibodies against components of the B7 family of immunomodulatory molecules that regulate T cell activation are being investigated in human malignancies including MM. The expression of B7-H3, a new component of the B7 family was investigated in primary cultures of human mesothelial cells (HMC) and in MM cell lines by flow cytometry and molecular analyses, and in MM tissues by immunohistochemistry. The role of DNA hypomethylating agents in modulating levels of B7-H3 expression in MM cells was also studied. Reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that B7-H3 mRNA was consistently detectable in mesothelial and MM cells investigated; however, real-time quantitative RT-PCR analyses showed highly heterogeneous levels of B7-H3 mRNA among investigated MM cells. The analysis of B7-H3 protein expression indicated that comparable levels of B7-H3 were expressed on both cell types. Treatment with the DNA hypomethylating agent 5-aza-2'-deoxycytidine did not significantly affect the expression of B7-H3 mRNA in MM cells. In vivo, while B7-H3 was expressed in all 13 tumor biopsies of the epithelial variant, with high levels in 54% of cases, it was rarely detectable in spindle type MM in which 1/5 biopsies weakly expressed B7-H3. These findings suggest that B7-H3 is a promising target for new immunotherapeutic strategies in MM, with particular emphasis in the epithelial variant.
- SourceAvailable from: Nazli Khodayari[show abstract] [hide abstract]
ABSTRACT: Malignant pleural mesothelioma (MPM) is an aggressive neoplasm with a poor prognosis. MPM grows from the mesothelial cells lining the surface of the lung and chest wall called Pleura. Exposure to asbestos is mainly linked to the development of MPM. Approximately 80% of the tumors are pleural in origin, and up to 3000 people are diagnosed with MPM in the United States annually. The incidence of MPM is expected to rise in the coming decades particularly in the developing countries. Although there is an increase in the awareness of danger associated with the use of asbestos, its use is still prevalent in Australia and Asia because of its durability and low cost. This further warns and adds to the mortality and morbidity of patients with MPM globally. The traditional treatment strategies have shown only modest improvement towards the disease. MPM is difficult to treat because of the fact that the time between the exposure to asbestos and the appearance of symptoms is extremely delayed, and also due to tumor involvement with the pleural surface and the adjoining tissues such as the chest wall, pericardium and sub-diaphragmatic organs. Despite advances in the diagnostic and treatment approaches the median survival rate for MPM is between 9 to 17 months. The standard care with double agent has shown modest improvement however, multimodality approach using novel targets may have potential to achieve the improvement in the survival rate. In this review we give an update on the conventional treatment modalities and discuss about various molecular targets including receptor EphA2, a novel target gene which may be considered as a biomarker for the diagnosis and treatment of MPM.American journal of cancer research. 01/2011; 2(2):222-34.