EGCG neutralizes the cytotoxic effects of BZM in multiple myeloma cells. (A) Chemical structures of Bortezomib (BZM) and (-)-epigallocatechin gallate (EGCG). (B) Percentage cell viability of RPMI/8226 cells was determined via MTT assay after 48 hours of treatment with 10 nM BZM in the presence or absence of 10 μM EGCG. (C) Percentage apoptotic cells was determined via TUNEL staining of slides prepared from RPMI/8226 cells treated for 48 hours with 10 nM BZM in the presence or absence of 10 μM EGCG. (D) Cell-cycle distribution of cells treated with 20 nM BZM and/or 20 μM EGCG for 24 hours was determined by flow cytometry analysis.³¹  Distribution of cells left of the dotted line (M1) indicates apoptotic or sub-G1/G0 cells. Cells in G1 display 2n DNA content (x-axis) and those in G2/M display 4n. Y-axis is relative number of cells. (E) Microphotographic images were taken of RPMI/8226 cells after 24 hours of treatment with 10 nM BZM in the presence or absence of 10 μM EGCG. (F-J) Percentage cell viability of RPMI/8226, U266, and MM1 cells treated for 48 or 72 hours with increasing concentrations of BZM in the presence of increasing concentrations of EGCG or TEAVIGO-EGCG as determined via MTT assay. The percentage survival of nontreated cell cultures was set to 100%; shown is mean ± SE (n ≥ 4). Low concentrations of EGCG may increase the viability of a cell culture to more than 100%; this may be due to a slight reduction of the high basal level of apoptosis, which is present even in nontreated cell cultures (C,D). (K) Patient MM cells were purified from bone marrow aspirates as described³²  and analyzed by MTT assay as detailed in panel B. Shown is the average of 4 measurements from 2 independent tissue samples (mean ± SE).