It is clinically believed that malignant pleural mesothelioma mainly originates from the visceral/parietal layer or the longitudinal/diaphragmatic four-part pleural area of the body, and it is highly aggressive[5] and fatal. At present, the pathogenesis of MPM is still unclear, but most scholars tend to believe that it is mainly caused by environmental and biological factors, as well as genetic factors, such as asbestos exposure and simian vacuolated virus 40, and genetic predisposition. In the past, for the treatment of malignant pleural mesothelioma, surgical treatment, radiotherapy/chemotherapy, targeted therapy and comprehensive treatment measures are usually selected. Although they have certain effects, the prognosis of patients is generally poor, and the 5-year survival rate is extremely low. Mesothelin is a surface antigen of tumor cells, which can be expressed in the surface mesothelial cells of the body cavity. It has been reported that it can be overexpressed in malignant pleural mesothelioma, and can enhance the proliferation and adhesion ability of various cancer cells. Therefore, it is expected to[6] become not only a diagnostic marker of this disease, but also an important target for clinical treatment. Therefore, meta-analysis of the clinicopathological role and prognostic significance of mesothelin expression in malignant pleural mesothelioma is helpful to better assist clinical diagnosis and treatment.
A total of 7 articles[7–13] were included in this meta-analysis, including 605 patients with malignant pleural mesothelioma. The results showed that high expression of mesothelin was significantly correlated with TNM stage, tumor invasion extent, and overall survival time, but not with age and gender of the patients. With the high expression of mesothelin, the tumor invasion range of patients is larger, the TNM stage is later, and the overall survival time is shortened. Therefore, it can be judged that the high expression of mesothelin may mainly affect the clinical prognosis[14–16] of patients by increasing the scope of tumor invasion and other factors. In order to avoid the interference of original literature on publication bias on the results of Meta-analysis, this paper uses Egger test to further clarify whether the original literature used in this analysis may cause corresponding bias. Funnel plot shows that the relevant P values are more than 0.05, indicating that such literature has low bias and little impact on the results of this study. The conclusions obtained are also relatively accurate and objective[17–18]. However, it should also be pointed out that the original literatures involved in this study were all written in English or Chinese, and there may be a lack of reference evidence in other languages. In addition, the concentration of some detection reagents and manufacturers may also have a slight impact on the study results.
In this study, there are obvious typical pathological features and overall prognosis of patients with high expression of mesothelin, such as deeper tumor invasion, high TNM stage, and poor prognosis, which indirectly indicates that the overall survival rate of malignant pleural mesothelioma patients with high expression of mesothelin may be relatively low. In fact, molecular studies of mesothelin show that it belongs to a related polypeptide precursor protein encoded by a 71kDa cDNA. This precursor protein can be enzymically cleaved into two parts, with a 40-kda fragment anchored by a substance called glycosyl phosphatidylinositol on the cell surface, called mesothelin, which can also be further modified by enzymes. Finally, the isoforms are produced and shed on the surface of related cells to form soluble mesothelin-related proteins or peptides. In recent years, some scholars have found that such proteins and peptides can show a significantly increased state in the serum of patients, so it may be more helpful to use the characteristics of mesothelin to make clinical diagnosis[19–20] of malignant pleural mesothelioma. In other words, targeted therapy for mesothelin may be an important benefit to the clinical treatment of malignant pleural mesothelioma. For example, clinical trials of chemotherapy with drugs related to mesothelin inhibitors can be tried. Although the prognosis results are still unclear, its clinical significance may be further clarified by observation of patients' pathological status and prognostic indicators. Therefore, it is also worthy of further research.
In conclusion, the high expression of intermedin in malignant pleural mesothelioma has high clinicopathological judgment and prognostic significance, which is worthy of clinical attention.