PDK4-Mediated Metabolic Reprogramming Promotes Rituximab Resistance in Diffuse Large B-Cell Lymphoma Via Negative Regulation of MS4A1/CD20

Abstract Background: Diffuse large B cell lymphoma (DLBCL) heterogeneity promotes the recurrence and anti-CD20-based therapeutic resistance. In previous studies, it has been demonstrated that the downregulation of MS4A1/CD20 expression after chemoimmunotherapy with rituximab can lead to rituximab resistance. However, the the mechanisms of CD20-loss remains unknown. Methods: The expression levels of PDK4 were investigated in DLBCL patients and cell lines by RNA-seq, qRT-PCR, western blotting and immunofluorescence analysis. Lentiviral infection was used to regulate the level of PDK4 in DLBCL cells. The effects of PDK4 on apoptosis, drug sensitivity and proliferation of DLBCL cells were evaluated by flow cytometry and cell-counting kit-8 (CCK-8) assay, as well as being assessed in a murine model. Cell metabolism was conducted by measurement of glucose consumption, lactate production, ATP levels, ECAR and OCR with corresponding assay kit. Results: Our data showed that PDK4 expression levels elevated significantly in DLBCL cells derived from both the patients and cell lines with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone regimen) resistant. We further found that the overexpression of PDK4 in DLBCL cells can lead to cell proliferation and rituximab resistance both in vitro and in vivo. Furthermore, the loss of PDK4 expression or treatment with the PDK4 inhibitor dichloroacetate is effective in increasing the rituximab-induced cell apoptosis in DLBCL cells. According to the mechanism studies, PDK4 mediated a metabolic shift that the main energy source was changed from OXPHOS to glycolysis. More importantly, with the knockdown or overexpression of PDK4 in DLBCL cells leads to a reverse MS4A1/CD20 expression. Conclusion: Our data identify a metabolic reprogramming role of PDK4 in rituximab resistance of DLBCL and highlight the unique function of PDK4 as an attractive therapeutic target.