The Expression of BAG3 Gene in Chronic Lymphocytic Leukemia and Its Clinical Significance

BAG3 (BCL2-associated athanogene 3) is a member of BAG family. Previously, many reports indicated that BAG3 was over-expressed in different human cancer tissues, such as thyroid carcinoma, pancreatic cancer, prostate cancer, and leukemic cells. However, there is no or low expression of BAG3 in normal tissues. These imply that BAG3 maybe have some important roles in the human cancers. This study was aimed to investigate the expression level of BAG3 mRNA in chronic lymphocytic leukemia (CLL) and its significance in evaluation of CLL prognosis.

100 CLL human patients and 20 healthy controls were enrolled in this study. The BAG3 mRNA expressions were measured by real-time PCR with fluorescent dye SYBR Green I, the β-actin was used as internal control. The relative quantitative value of BAG3 expression was calculated by means of 2 ^(–ΔCt). We analyzed the results with established CLL prognostic factors, overall survival (OS) and treatment-free survival (TFS).

The expression of BAG3 mRNA in 100 CLL patients was significantly higher than 20 normal control (p = 0.038). Furthermore, The BAG3 expression was obviously increased in CD38 positive patients CD38 (n = 31) than CD38 negetive patients it (n = 61, p = 0.0238). We also found that the expression of BAG3 in the patients with unmutated immunoglobulin heavy-chain (n = 29) was markedly higher than those with mutated immunoglobulin heavy-chain (IgHV) (n = 62, p = 0.0326). It is also found that the patients with enlarged lymph nodes (n = 24) have higher BAG3 expression, compared with those without enlarged lymph nodes (n = 76, p = 0.0004). The increased BAG3 level can also be found in the patients with splenomegaly (n = 32),compared with those without splenomegaly (n=68, p = 0.0393). No association was found between BAG3 expression and patient clinical baseline information (gender and age), as well as other established prognostic factors (lymphocyte count, cytogenetics analysis and p53 mutation status). 25 of these patients were treated with fludarabine-based therapy, interestingly, BAG3 expression level was significantly increased in patients who were relapse and/or refractory to fludarabine-based treatment (n = 10, p = 0.019). However, there are no differences in OS and TFS between patients with low BAG3 expressions and high expression, which indicated BAG3 didn’t affect the patients’ OS and TFS.

These results showed that the BAG3 expression in CLL patients is markedly higher than normal controls. CD38, mutation of IgHV, lymph nodes and splenomegaly are related to the expression of BAG3 in CLL. Furthermore, the patients, who were relapse and/or refractory to fludarabine, have a higher expression of BAG3. These imply that BAG3 may be involved in the pathogenesis of CLL and the roles of BAG3 in CLL need further investigation.

No relevant conflicts of interest to declare.