Lymphoma cells lacking pro-apoptotic BAX are highly resistant to BH3-mimetics targeting pro-survival MCL-1 but retain sensitivity to conventional DNA-damaging drugs

Abstract

BH3-mimetic drugs are an anti-cancer therapy that can induce apoptosis in malignant cells by directly binding and inhibiting pro-survival proteins of the BCL-2 family. The BH3-mimetic drug venetoclax, which targets BCL-2, has been approved for the treatment of chronic lymphocytic leukaemia and acute myeloid leukaemia by regulatory authorities worldwide. However, while most patients initially respond well, resistance and relapse while on this drug is an emerging and critical issue in the clinic. Though some studies have begun uncovering the factors involved in resistance to BCL-2-targeting BH3-mimetic drugs, little focus has been applied to pre-emptively tackle resistance for the next generation of BH3-mimetic drugs targeting MCL-1, which are now in clinical trials for diverse blood cancers. Therefore, using pre-clinical mouse and human models of aggressive lymphoma, we sought to predict factors likely to contribute to the development of resistance in patients receiving MCL-1-targeting BH3-mimetic drugs. First, we performed multiple whole genome CRISPR/Cas9 KO screens and identified that loss of the pro-apoptotic effector protein BAX, but not its close relative BAK, could confer resistance to MCL-1-targeting BH3-mimetic drugs in both short-term and long-term treatment regimens, even in lymphoma cells lacking the tumour suppressor TRP53. Furthermore, we found that mouse Eµ-Myc lymphoma cells selected for loss of BAX, as well as upregulation of the untargeted pro-survival BCL-2 family proteins BCL-XL and A1, when made naturally resistant to MCL-1 inhibitors by culturing them in increasing doses of drug over time, a situation mimicking the clinical application of these drugs. Finally, we identified therapeutic approaches which could overcome these two methods of resistance: the use of chemotherapeutic drugs or combined BH3-mimetic treatment, respectively. Collectively, these results uncover some key factors likely to cause resistance to MCL-1 inhibition in the clinic and suggest rational therapeutic strategies to overcome resistance that should be investigated further.

Fructose aggravating colon barrier dysfunction by decreasing gut bacteria metabolites indole-3-carboxaldehyde and inhibiting activation of aryl hydrocarbon receptor in vivo and in vitro

“…The level of MDA (Figure 3E) showed fructose induce systemic oxidative stress which are similar with other previous study. Bcl-2 is an anti-apoptotic protein while Bax is a kind of pro-apoptotic protein 40 , Bax expression increased, and Bcl-2 decreased stated that the original balance of cell growth and death was broken in excessive fructose intake.…”

Venetoclax resistance in acute lymphoblastic leukemia is characterized by increased mitochondrial activity and can be overcome by co-targeting oxidative phosphorylation

“…While proliferation rates and sensitivity to chemotherapeutic drugs and other cell death inducing agents were unchanged, VEN-insensitivity of cells (in five biological replicates) was stable, irrespective of exposure to VEN. Previous studies have shown that adaptation of tumor cells to VEN is characterized by different mechanisms resulting in functional loss of pro-apoptotic regulators like BAD, BAX, NOXA and PUMA or by a shift in dependency from BCL-2 to other anti-apoptotic proteins like MCL-1 [ 26 , 41 – 50 ].…”

“…Loss of BAX has been described in VEN-resistant CLL cell lines and patient samples without concurrent BAX mutations [ 48 ], as we have observed upon modeled VEN-resistance in ALL. Interestingly, BAX knockout in B-cell lymphoma cells did not result in decreased VEN-sensitivity [ 50 ], further indicating that BAX-deficiency (due to gene alteration or other mechanisms) on its own impairs VEN-sensitivity in some contexts but does not seem to be a general mechanism of VEN-resistance.…”

BCL-W makes only minor contributions to MYC-driven lymphoma development

“…Primary and HRP-conjugated secondary antibodies are listed in Supplementary Tables 2 and 3 , respectively. Western blotting performed as described previously [ 41 ].…”