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Updated: May 13, 2026
Using RNA-sequencing to Detect Novel Splice Variants Related to Drug Resistance in In Vitro Cancer Models
Published on: December 9, 2016
RNAi screening uncovers Dhx9 as a modifier of ABT-737 resistance in an Eμ-myc/Bcl-2 mouse model
John R Mills1, Abba Malina, Teresa Lee
1Department of Biochemistry McGill University, Montreal, Quebec, Canada.
Abstract:
ABT-737 is a promising chemotherapeutic agent that promotes apoptosis by acting as a selective BH3 mimetic to neutralize Bcl-2-like family members. One shortcoming with its use is that Mcl-1, a member of the Bcl-2 family, is poorly inhibited by ABT-737 and thus is a major cause of resistance. We performed a short hairpin RNA (shRNA)-based drop-out screen to identify novel genes and pathways that could reverse resistance to ABT-737 treatment in Eµ-myc/Bcl-2 lymphoma cells engineered to rely on endogenous Mcl-1 for survival. Several drug-sensitive shRNAs were identified that were selectively depleted in the presence of ABT-737. Of these, 2 independent shRNAs targeting the RNA/DNA helicase Dhx9 were found to sensitize lymphomas to ABT-737 to an extent comparable to control Mcl-1 shRNAs. Although Dhx9 suppression sensitized both mouse and human cells to ABT-737 treatment, it did so without altering MCL-1 levels. Rather, loss of Dhx9 appeared to activate a p53-dependent apoptotic program, through aggravation of replicative stress, which was found to be both necessary and sufficient for the ABT-737-shDhx9 synthetic lethal relationship.
Insights
Researchers identified Dhx9 as a target to overcome resistance to the chemotherapy drug ABT-737. Suppressing Dhx9 reactivates cancer cell death pathways, offering a new strategy for treating lymphomas resistant to ABT-737.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- ABT-737 is a BH3 mimetic promoting apoptosis by targeting Bcl-2 family proteins.
- Mcl-1, a Bcl-2 family member, confers resistance to ABT-737 due to poor inhibition.
- Identifying pathways to overcome Mcl-1-mediated resistance is crucial for ABT-737 efficacy.
Purpose of the Study:
- To identify novel genes and pathways that reverse ABT-737 resistance in Mcl-1-dependent lymphomas.
- To investigate the role of Dhx9 in modulating sensitivity to ABT-737 treatment.
Main Methods:
- Utilized a short hairpin RNA (shRNA)-based drop-out screen in Eµ-myc/Bcl-2 lymphoma cells.
- Identified shRNAs selectively depleted upon ABT-737 treatment.
- Assessed the effect of Dhx9 suppression on ABT-737 sensitivity and Mcl-1 levels.
Main Results:
- Dhx9 was identified as a key gene sensitizing lymphomas to ABT-737, comparable to Mcl-1 suppression.
- Dhx9 suppression sensitized both mouse and human cells to ABT-737 without altering Mcl-1 levels.
- Loss of Dhx9 activated a p53-dependent apoptotic program via increased replicative stress.
Conclusions:
- Dhx9 suppression represents a novel strategy to overcome Mcl-1-mediated resistance to ABT-737.
- The synthetic lethal interaction between ABT-737 and Dhx9 is dependent on p53 activation and replicative stress.
- Targeting Dhx9 may enhance the therapeutic efficacy of ABT-737 in resistant lymphomas.
