By reducing global mRNA translation in several ways, 2-deoxyglucose lowers MCL-1 protein and sensitizes hemopoietic tumor cells to BH3 mimetic ABT737

Abstract

Drugs targeting various pro-survival BCL-2 family members (‘‘BH3 mimetics’’) have efficacy in hemopoietic malignancies, but the non-targeted pro-survival family members can promote resistance. Pertinently, the sensitivity of some tumor cell lines to BH3 mimetic ABT737, which targets BCL-2, BCL-XL, and BCL-W but not MCL-1, is enhanced by 2-deoxyglucose (2DG). We found that 2DG augmented apoptosis induced by ABT737 in 3 of 8 human hemopoietic tumor cell lines, most strongly in pre-B acute lymphocytic leukemia cell line NALM-6, the focus of our mechanistic studies. Although 2DG can lower MCL-1 translation, how it does so is incompletely understood, in part because 2DG inhibits both glycolysis and protein glycosylation in the endoplasmic reticulum (ER). Its glycolysis inhibition lowered ATP and, through the AMPK/mTORC1 pathway, markedly reduced global protein synthesis, as did an ER integrated stress response. A dual reporter assay revealed that 2DG impeded not only cap-dependent translation but also elongation or cap-independent translation. MCL-1 protein fell markedly, whereas 12 other BCL-2 family members were unaffected. We ascribe the MCL-1 drop to the global fall in translation, exacerbated for mRNAs with a structured 5′ untranslated region (5′UTR) containing potential regulatory motifs like those in MCL-1 mRNA and the short half-life of MCL-1 protein. Pertinently, 2DG downregulated two other short-lived oncoproteins, MYC and MDM2. Thus, our results support MCL-1 as a critical 2DG target, but also reveal multiple effects on global translation that may well also affect its promotion of apoptosis.

Saga of Mcl-1: regulation from transcription to degradation

“…Socalled "strong mRNAs" (e.g., β-actin) are minimally affected by alterations in eIF4F complex formation, whereas "weak mRNAs" strongly depend on eIF4F availability [47]. There are strong evidence that Mcl-1 mRNA exemplifies "weak mRNA" [48][49][50]. The 5′UTR of Mcl-1 mRNA presumably possesses a substantial secondary structure, which is one of the possible reasons for the "weakness" of Mcl-1 mRNA [50].…”

“…There are strong evidence that Mcl-1 mRNA exemplifies "weak mRNA" [48][49][50]. The 5′UTR of Mcl-1 mRNA presumably possesses a substantial secondary structure, which is one of the possible reasons for the "weakness" of Mcl-1 mRNA [50]. Of note, in numerous studies, mTORC1 was reported to positively regulate Mcl-1 synthesis through regulation of CDT [48], while AMP-activated protein kinase (AMPK) led to the opposite effect [49,51].…”

Intracellular BAPTA directly inhibits PFKFB3, thereby impeding mTORC1-driven Mcl-1 translation and killing Mcl-1-addicted cancer cells

“…Our findings are in line with other studies demonstrating a link between glycolysis, mTORC1 activity and mRNA translation. Indeed, the team of Adams and coworkers revealed that 2-deoxyglucose (2-DG), which inhibits the first step in the glycolytic pathway, caused a decrease in p70S6K phosphorylation and an increase in 4E-BP1 activity, indicating that inhibition of glycolysis using 2-DG provoked a decrease in general translation activity (38). In the same study, 2-DG rapidly affected steady-state Mcl-1 levels, sensitizing human hematopoietic tumor cell lines to ABT-737, a nonselective Bcl-2/Bcl-XL-antagonizing BH3 mimetic.…”

MCL-1 is a clinically targetable vulnerability in breast cancer

“…MCL-1 is a particularly short-lived protein (estimated half life ~1–3 hours) and MCL1 mRNA is considered “weak” due to its GC-rich and highly structured 5’ untranslated region (UTR) [ 64 , 65 ]. Taken together, this conspires to preferentially sensitize MCL-1 to alterations in the rate of global protein synthesis and offers the opportunity to indirectly target MCL-1 levels [ 66 ]. As well as driving MEK/ERK-mediated phosphorylation of ELK-1 to activate MCL1 transcription, epidermal growth factor (EGF) induces PI3K pathway activation to stimulate mammalian target of rapamycin (mTOR) regulated cap-dependent translation, and inhibition of mTOR complex 1 (mTORC1) sensitizes multiple cancer cell lines and mouse models to apoptosis through decreased MCL-1 protein levels [ 50 , 65 , 67–69 ].…”