Selective Protein Kinase C β Inhibition Induces Apoptosis and Arrests Cell Cycle in AIDS-Related Non-Hodgkin Lymphoma Cell Lines.

Abstract 4807

AIDS-related Non-Hodgkin Lymphoma (AIDS-NHL) constitutes an aggressive variety of lymphomas characterized by increased extranodal involvement, relapse rate and resistance to chemotherapy. In the present era of target-specific therapy, PKCβ targeting showed promising results in preclinical studies, as well as phase II clinical trials involving a wide variety of cancers. Studies describing the role of PKCβ in AIDS-NHL are primitive if not lacking, and HIV infection has been considered an exclusion criterion in clinical studies involving PKCβ inhibition in NHL patients. In the present study, we measured the sensitivity of a variety of AIDS-NHL cell lines to PKCβ inhibition. Three cell lines were studied: 2F7 (AIDS-Burkitt's Lymphoma), BCBL-1 (AIDS-Primary Effusion Lymphoma) and UMCL01-101 (AIDS-Diffuse Large B Cell Lymphoma). Cells were tested for PKCβ1 and PKCβ2 expression by immunoblot. Cell viability was measured in the presence of a PKCβ-specific inhibitor at concentrations of 5, 10, 20 and 30 μM for 48 hours in the presence of 10% fetal bovine serum (FBS). The IC50 at 48 hours was determined for each cell line, and cells were cultured in the presence of the correspondent IC50 for 24 and 72 hours. MTS assay was performed to quantify cell viability, and TUNEL assay with propidium iodide staining was used to detect apoptotic induction and effect on cell cycle. Results showed that 2F7 and UMCL01-101 cell lines express PKCβ1 and PKCβ2, while BCBL-1 expresses only PKCβ1 and lacks PKCβ2 expression. 2F7 and BCBL-1 were sensitive to PKCβ inhibitor with IC50 of 14 and 15 μM of inhibitor, respectively. UMCL01-101 showed relative resistance to PKCβ inhibition with an IC50 of 28 μM. Incubation in the presence of the correspondent IC50 induced significant apoptosis in all cell lines starting after 2 hours of treatment; UMCL01-101 cell line was not significantly affected when incubated in the presence of 14 μM. Our results also showed cell cycle inhibition in 2F7 and BCBL-1 starting respectively after 2 and 8 hours of incubation with the correspondent IC50; UMCL01-101 showed no features of cell cycle inhibition when cultured in the presence of high concentration (IC50) or low concentration (14 μM) of the inhibitor. BCBL-1 cell line findings were unexpected in the absence of PKCβ2 expression and implicate PKCβ1 as a regulator in these cells. These results indicate that PKCβ plays an important role in AIDS-related NHL survival, and suggest that PKCβ targeting should be considered in a broader spectrum of NHL. Ongoing studies will detail the mechanism of PKCβ inhibition and uncover the underlying mechanism of resistance in PKCβ expressing UMCL01-101 cells. This mechanism may be considered for exclusion from treatment.