Proteasome Inhibitor Does Not Affect the Function of Human Immune Systems: Effects on Dendritic Cells, T Lymphocytes and NK Cells.

Bortezomib is the first proteasome inhibitor approved for the therapy of multiple myeloma (MM) based on its in vitro and in vivo activity in myeloma. However, the toxicity and effects of this drug on the human immune function have not been entirely studied. In the present study, we evaluated the effects of Bortezomib on normal human immune cells including dendritic cells (DC), T lymphocytes and NK cells for cell survival, antigen expression, production of cytokines, and other key parameters of immune cell function. In our evaluation of effect of Bortezomib on DC, we did not observe significant change in the expression of cell surface antigens including CD40, CD80, CD83, CD86, HLA-ABC and HLA-DPQR molecules in terms of percentage of cells positive as well as mean fluorescence intensity (MFI). Bortezomib treated immature DC maintained the ability for antigen uptake as measured by uptake of Dextran-FITC (untrt vs. trt = 798 MFI vs. 802 MFI), maintained the expression levels of antigen uptake receptors including mannose (untrt vs. trt = 85% vs. 79%) and DEC-205 (untrt vs. trt = 49% vs. 42%), and the capacity to produce IL-12 (untrt vs. trt = 135 vs. 125 pg/ml). In addition, Bortezomib treated mature DC was able to induce comparable levels of allogenic T cell proliferation to the untreated mature DC as measured by ³[H]-Thymidine incorporation (untrt vs. trt = 212556 cpm vs. 220571 cpm). Furthermore, cell surface antigen expression including CD3, CD4, CD8, CD28, CD154 (CD40L) and TCRab on T lymphocytes were not changed by Bortezomib treatment. The treated T cells also maintained the ability to secrete IFN-g secretion in response to allogenic DC (untrt vs. trt = 85 vs. 88 pg/ml) or Staphylococcal enterotoxin B (untrt vs. trt = 131 vs. 154 pg/ml). The cytolytic activity of the NK cell population was comparable between proteasome inhibitor treated and untreated control cells against the McCAR (untrt vs. trt = 44% vs. 52%) and MM1S (49% vs. 42%) target MM cell lines. This observation was correlated with similar expression levels of CD2, CD11a, CD94, NKp30, NKp44, NKp46, and KARp50.3 activation antigens in treated versus untreated NK cells. These, in vitro results confirm lack of adverse effects of Bortezomib on immune function, and allow us to incorporate of Bortezomib in multimodality therapy that includes immunotherapy.