Inhibition of EGFR pathway promotes the cytotoxicity of ABT-263 in human leukemia K562 cells by blocking MCL1 upregulation

BCL2L1 inhibitor A-1331852 inhibits MCL1 transcription and triggers apoptosis in acute myeloid leukemia cells

BH3 mimetics exert anticancer activity by inhibiting anti-apoptotic BCL2 proteins. However, accumulating evidence indicates that the off-target effects of these drugs tightly modulates their anticancer activities. In this study, we investigated whether the BCL2L1 inhibitor A-1331852 induced the death of U937 acute myeloid leukemia (AML) cells through a non-BCL2L1-targeted effect. A-1331852-induced apoptosis in U937 cells was characterized by increased ROS production, downregulation of MCL1, and loss of mitochondrial membrane potential. Ectopic expression of MCL1 alleviated A-1331852-induced mitochondrial depolarization and cytotoxicity in U937 cells. A-1331852-induced ROS production increased p38 MAPK phosphorylation and inhibited MCL1 transcription. Inhibition of p38 MAPK activation restored MCL1 expression in A-1331852-treated cells. A-1331852 triggered p38 MAPK-mediated Cullin 3 downregulation, which in turn increased PP2Acα expression, thereby reducing CREB phosphorylation. A-1331852 reduced the binding of CREB to the MCL1 promoter, leading to the inhibition of CREB-mediated MCL1 transcription. Furthermore, A-1331852 acted synergistically with the BCL2 inhibitor ABT-199 to induce U937 and ABT-199-resistant U937 cell death by inhibiting MCL1 expression. A similar phenomenon caused A-1331852-induced MCL1 downregulation and cytotoxicity in AML HL-60 cells. Collectively, our data suggest that A-1331852 shows an off-target effect of inhibiting MCL1 transcription, ultimately leading to U937 and HL-60 cell death.

Upregulated SPAG6 promotes acute myeloid leukemia progression through MYO1D that regulates the EGFR family expression

Chromosomal aberrations and gene mutations have been considered to be the major reasons for high recurrence rates and poor survival among acute myeloid leukemia (AML) patients. However, the underlying molecular mechanism of AML gene mutation remains largely unclear. Here, we show that SPAG6 (sperm-associated antigen 6), one of the most markedly increased SPAG genes in AML, significantly contributed to the proliferation and migration of leukemic cells. SPAG6 was highly expressed in AML, and its upregulation was negatively correlated with the prognosis of the disease. In vitro, SPAG6 promoted the proliferation and migration of leukemia cells and promoted cell cycle progression from the G1 phase to the S phase. In vivo, low expression of SPAG6 reduced the proliferation and infiltration of leukemia cells and prolonged the survival of xenograft tumor mice. Furthermore, immunoprecipitation and mass spectrometry analysis showed that SPAG6 interacts with MYO1D (myosin 1D). Specifically, overexpression of SPAG6 promoted the translocation of MYO1D into the cell membrane, thus upgrading the expression level of the EGFR family and thereby promoting the progression of AML. Overall, our study found that SPAG6 combined with MYO1D and translocated MYO1D from the cytosol to the cytomembrane, which induced the PI3K (phosphoinositide 3-kinase)/AKT (protein kinase B) signaling and ERK (extracellular signal-regulated kinase) signaling pathway to regulate the growth and prognosis of AML. SPAG6 may become a new target gene for the treatment of AML.

BH3-mimetics: recent developments in cancer therapy

The hopeful outcomes from 30 years of research in BH3-mimetics have indeed served a number of solid paradigms for targeting intermediates from the apoptosis pathway in a variety of diseased states. Not only have such rational approaches in drug design yielded several key therapeutics, such outputs have also offered insights into the integrated mechanistic aspects of basic and clinical research at the genetics level for the future. In no other area of medical research have the effects of such work been felt, than in cancer research, through targeting the BAX-Bcl-2 protein-protein interactions. With these promising outputs in mind, several mimetics, and their potential therapeutic applications, have also been developed for several other pathological conditions, such as cardiovascular disease and tissue fibrosis, thus highlighting the universal importance of the intrinsic arm of the apoptosis pathway and its input to general tissue homeostasis. Considering such recent developments, and in a field that has generated so much scientific interest, we take stock of how the broadening area of BH3-mimetics has developed and diversified, with a focus on their uses in single and combined cancer treatment regimens and recently explored therapeutic delivery methods that may aid the development of future therapeutics of this nature.