In MM, it has been demonstrated that proteasome inhibition can trigger the accumulation of Mcl-1, which has been shown to confer MM cell resistance to bortezomib-induced lethality.
TG02 induced robust activation of both the intrinsic and extrinsic pathways of apoptosis, and depletion of XIAP and the key multiple myeloma survival protein Mcl-1.
Levels of MYC and myeloid cell leukemia 1, two known eIF4F-responsive transcripts and key survival factors in MM, were reduced upon eIF4F inhibition, and their independent suppression also synergized with DEX.
Thus, we investigated the anti-tumour effects of a pan-BCL2 inhibitor, AT-101, which has high binding specificity for BCL2 and MCL1 in preclinical models of plasma cell cancers (Multiple myeloma and Waldenström macroglobulinaemia).
Our own and other previous studies have demonstrated caspase-dependent generation of a 28kDa Mcl-1 fragment, Mcl-1(128-350), which inhibits MM cell proliferation and survival.
Our results for plasmacytomas highlight the significance of antiapoptotic changes in multiple myeloma, which include elevated expression of Mcl-1 and, less frequently, Bcl-2, and suggest that closer attention to defects in Bim expression is warranted.
In conclusion, our data demonstrate that soluble factors from MM cells are able to generate MDSC through Mcl-1 upregulation and this cell population can be considered as a possible target in MM disease.
Ritonavir and metformin effectively suppressed AKT and mTORC1 phosphorylation and prosurvival BCL-2 family member MCL-1 expression in multiple myeloma cell lines in vitro and in vivo.
Furthermore, previous studies demonstrated that proteasome inhibitors induce Mcl-1 accumulation that, in turn, slows down their pro-apoptotic effects, and the cell survival in multiple myeloma is highly dependent on Mcl-1.
We found that down-regulation of Mcl-1, an essential MM survival factor, was associated with curcumin-induced cell death and its knockdown sensitized myeloma cells to curcumin, highlighting Mcl-1 as an important target for curcumin-induced apoptosis.
IHC of multiple myeloma patient bone marrow biopsies and aspirates (n = 95) revealed high levels of BCL-2 and BCL-XL in 62% and 43% of evaluable samples, respectively, while 34% were characterized as BCL-2(High)/BCL-XL (Low) In addition to MCL-1, our data suggest that BCL-XL may also be a potential resistance factor to venetoclax monotherapy and in combination with bortezomib.
We used the Bcl-2/Bcl-x<sub>L</sub> inhibitor ABT-737 to study the factors regulating whether myeloma is Mcl-1 dependent, and thus resistant to ABT-737-induced apoptosis, or Bcl-2/Bcl-x<sub>L</sub> codependent, and thus sensitive to ABT-737.
Mcl-1 was up-regulated in all MM lines tested, including bortezomib-resistant lines, human MM xenograft mouse models, and primary CD138<sup>+</sup> MM cells.
Venetoclax is a selective, orally bioavailable BCL-2 inhibitor that induces cell death in multiple myeloma (MM) cells, particularly in those harboring t(11;14), which express high levels of BCL-2 relative to BCL-X<sub>L</sub> and MCL-1.
We show that our lead compound (compound 20) decreases glucose uptake and cell proliferation as well as inhibits the expression of pro-survival MCL-1 in MM similar to the effect observed via knockdown of GLUT4 expression.
In myeloma, in vitro sensitivity to venetoclax is mainly observed in plasma cells harboring the t(11;14) translocation, a molecular subgroup associated with high Bcl-2 and low Mcl-1/Bcl-XL expression.