In the current study, first of all, we investigated the prognostic significance of CCR2 expression in DLBCL patients. We found that CCR2 was high-expressed in 74% of the DLBCL patients and the frequency of CCR2 expression gradually increased with increasing IPI scores. In addition, through multivariate analysis, we found for the first time that CCR2 receptor was an independent prognostic marker that affecting DLBCL patients. Our findings are paralleled by previous studies in which CCR2 expression was described as a prognostic factor associated with poor prognosis in liver cancer, lung cancer, prostate cancer, colorectal cancer and renal cancer[13, 24–28]. Furthermore, Kaplan-Meier analysis showed that patients with positive CCR2 expression had markedly inferior PFS and OS, which is consistent with the observations of B. Ou, et al.
Since CCR2 expression is upregulated in the majority of DLBCL patients, we investigated the expression of CCR2 in DLBCL cell lines to explore the role of this receptor on DLBCL cells. The results in vitro studies showed that CCR2 expression was detected by protein level analysis in DLBCL cell lines, including SUDHL-2, SUDHL-4, OCI-Ly10, SUDHL-6 and OCI-LY8 cells. Several published studies have identified the expression of CCR2 in cancer cells, including prostate cancer, multiple myeloma, kidney cancer and lung cancer cells. To examine the immediate effects of CCR2 expression on DLBCL cell lines, in vitro experiment, we treated SUDHL-2 and OCI-Ly8 cells with pharmacological concentrations of CCR2 antagonist sc-202525. The result indicates high level of CCR2 stimulates the proliferation, migration and anti-apoptotic ability of DLBCL cells. The present results are consistent with previous studies, in which the CCR2 expression facilitates neoplastic progression of colorectal and ovarian cancer[27, 30].
Meanwhile, in vivo experiments, the results showed that the tumor was significantly reduced in volume after treatment with CCR2 antagonist, and bioluminescence imaging indicated that CCR2 antagonists significantly inhibit DLBCL cells dissemination, these results are consistent with our in vitro observations. Due to such an important role of CCR2 in tumor growth, invasion, migration and survival, optimal use of CCR2 inhibition may be part of a potential targeted therapy. The results of the current study indicate that CCR2 antagonists reduce cell viability, block metastasis, improve chemotherapeutic efficacy and overcome macrophage-induced depression [17, 31, 32]. A potent, selective and orally administered antagonist of CCR2, designated INCB3344, in both human and murine, the contents of these details have been published previously. In fact, a phase II clinical trial was performed using the anti-CCR2 monoclonal antibody MLN1202 in patients with bone metastasis from cancer . Furthermore, The first clinical trials of CCR2 antagonist called PF-04136309 (Pfizer) for its therapeutic potential in pancreatic adenocarcinoma are currently proceeding. In addition, Chemocentryx has recently commenced a Phase Ib trial of a CCR2 antagonist (CCX872) for the treatment of patients with irresectable pancreatic cancer. These clinical researches will provide the most desired information on the security and potential therapeutic effects of CCR2 signalling blockade in people suffering from cancers.
The PI3K/Akt signalling pathway and p38 MARK signaling pathway are critical for many physiological and pathological conditions, such as regulating cell survival, growth, proliferation, angiogenesis, transcription, translation and metabolism [20, 37–39]. To further investigate the molecular mechanisms by which CCR2 expression promotes the survival of DLBCL cells, Western blot analysis for the PI3K/Akt signalling pathway and the P38 MARK signalling pathway showed that CCR2 antagonists significantly inhibited the activation of the PI3K/Akt signalling pathway, yet activated the P38 MARK signalling pathway in vitro. Similarly, the data according to Roca et al, the CCL2-CCR2 axis regulates autophagy and increases survivin expression via the PI3K/Akt pathway, providing a strong survival advantage in prostate cancer PC-3 cells. In ovarian cancer, Chao et al. found that binding of large omental adipocytes to their cognate receptor CCR2 promotes tumor cell migration and omental metastasis through activation of the PI3K/Akt pathway. In addition, Erwin F et al. found that apoptotic stimuli sometimes trigger the activation of p38 via secondary pathways, such as the production of reactive oxygen species (ROS). These results highly emphasized the carcinogenic role of CCR2 in DLBCL and that targeting CCR2 may be identified as a very promising therapeutic strategy for DLBCL.
In conclusion, we demonstrated that the CCR2 receptor is an independent prognostic marker that affects patients with DLBCL and is associated with poorer OS and PFS. Furthermore, we found that CCR2 antagonists inhibited DLBCL cell proliferation, migration and promotes apoptosis in vitro as well as in vivo by activating the PI3K/Akt signaling pathway and the p38 MARK signaling pathway. These discoveries suggest that targeting CCR2 may be a promising treatment option for DLBCL.