Targeting PIN-1 Attenuates GCB DLBCL Cell Proliferation Through Inhibition of PI3K/AKT Signaling

INTRODUCTION: Diffuse large B cell lymphoma (DLBCL) is a highly heterogeneous type of non-Hodgkin lymphoma with many molecular subtypes that can be distinguished by gene expression profiling (GEP). However, the pathogenesis of DLBCL is still unclear. MATERIALS AND METHODS: The expression levels of the prolyl isomerase PIN-1 and other related proteins were determined in 73 primary DLBCL patient samples and cell lines by Western blotting (WB) and immunohistochemical (IHC) staining. Cell cycle and apoptosis were evaluated by flow cytometry. Lymphoma cell viability was detected by CCK-8 proliferation assay. RESULTS: High levels of PIN-1 expression were detected in 55% of germinal center B cell (GCB) DLBCL patient samples, whereas such abnormal expression levels were found in only 11% of non-GCB DLBCL patient samples. PIN-1 expression was positively associated with activation of the oncogenic phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway in both GCB DLBCL cell lines and primary patient samples. Depletion of PIN-1 was cytotoxic to GCB DLBCL model cell lines because it led to inhibition of the PI3K/AKT signaling pathway, revealing a GCB DLBCL subgroup that is dependent on this pathway. A PI3K inhibitor was selectively toxic to GCB DLBCL lines expressing high levels of PIN-1. CONCLUSION: Our study used PIN-1 to identify a new subgroup of GCB DLBCL associated with the PI3K/AKT signaling pathway, and our findings reveal that inhibition of PI3K is a promising therapeutic approach for GCB DLBCL.