4EBP1-mediated SLC7A11 protein synthesis restrains ferroptosis triggered by MEK inhibitors in advanced ovarian cancer.

Loss of ferroptosis contributes to the development of human cancer, and restoration of ferroptosis has been demonstrated as a potential therapeutic strategy in cancer treatment. However, the mechanisms of how ferroptosis escape contributes to ovarian cancer (OV) development are not well elucidated. Here we show that ferroptosis negative regulation (FNR) signatures correlated with the tumorigenesis of OV and were associated with poor prognosis, suggesting that restoration of ferroptosis represents a potential therapeutic strategy in OV. High throughput drug screening with a kinase inhibitor library identified MEK inhibitors as ferroptosis inducers in OV cells. We further demonstrated that MEK inhibitor resistant OV cells were less vulnerable to trametinib-induced ferroptosis. Mechanistically, mTOR/4EBP1 signaling promoted SLC7A11 protein synthesis, leading to ferroptosis inhibition in MEK inhibitor resistant cells. Dual inhibition of MEK and mTOR/4EBP1 signaling restrained the protein synthesis of SLC7A11 via suppression of the mTOR-4EBP1 activity to reactivate ferroptosis in resistant cells. Together, these findings provide a promising therapeutic option for OV treatment through ferroptosis restoration by the combined inhibition of MEK and mTOR/4EBP1 pathways.

Targeting AURKA to induce synthetic lethality in CREBBP-deficient B-cell malignancies via attenuation of MYC expression.

Loss-of-function mutations in CREBBP, which encodes for a histone acetyltransferase, occur frequently in B-cell malignancies, highlighting CREBBP deficiency as an attractive therapeutic target. Using established isogenic cell models, we demonstrated that CREBBP-deficient cells are selectively vulnerable to AURKA inhibition. Mechanistically, we found that co-targeting CREBBP and AURKA suppressed MYC transcriptionally and post-translationally to induce replication stress and apoptosis. Inhibition of AURKA dramatically decreased MYC protein level in CREBBP-deficient cells, implying a dependency on AURKA to sustain MYC stability. Furthermore, in vivo studies showed that pharmacological inhibition of AURKA was efficacious in delaying tumor progression in CREBBP-deficient cells and was synergistic with CREBBP inhibitors in CREBBP-proficient cells. Our study sheds light on a novel synthetic lethal interaction between CREBBP and AURKA, indicating that targeting AURKA represents a potential therapeutic strategy for high-risk B-cell malignancies harboring CREBBP inactivating mutations.

Aberrant JAK-STAT signaling-mediated chromatin remodeling impairs the sensitivity of NK/T-cell lymphoma to chidamide.

BACKGROUND: Natural killer/T-cell lymphoma (NKTL) is a rare type of aggressive and heterogeneous non-Hodgkin's lymphoma (NHL) with a poor prognosis and limited therapeutic options. Therefore, there is an urgent need to exploit potential novel therapeutic targets for the treatment of NKTL. Histone deacetylase (HDAC) inhibitor chidamide was recently approved for treating relapsed/refractory peripheral T-cell lymphoma (PTCL) patients. However, its therapeutic efficacy in NKTL remains unclear. METHODS: We performed a phase II clinical trial to evaluate the efficacy of chidamide in 28 relapsed/refractory NKTL patients. Integrative transcriptomic, chromatin profiling analysis and functional studies were performed to identify potential predictive biomarkers and unravel the mechanisms of resistance to chidamide. Immunohistochemistry (IHC) was used to validate the predictive biomarkers in tumors from the clinical trial. RESULTS: We demonstrated that chidamide is effective in treating relapsed/refractory NKTL patients, achieving an overall response and complete response rate of 39 and 18%, respectively. In vitro studies showed that hyperactivity of JAK-STAT signaling in NKTL cell lines was associated with the resistance to chidamide. Mechanistically, our results revealed that aberrant JAK-STAT signaling remodels the chromatin and confers resistance to chidamide. Subsequently, inhibition of JAK-STAT activity could overcome resistance to chidamide by reprogramming the chromatin from a resistant to sensitive state, leading to synergistic anti-tumor effect in vitro and in vivo. More importantly, our clinical data demonstrated that combinatorial therapy with chidamide and JAK inhibitor ruxolitinib is effective against chidamide-resistant NKTL. In addition, we identified TNFRSF8 (CD30), a downstream target of the JAK-STAT pathway, as a potential biomarker that could predict NKTL sensitivity to chidamide. CONCLUSIONS: Our study suggests that chidamide, in combination with JAK-STAT inhibitors, can be a novel targeted therapy in the standard of care for NKTL. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02878278. Registered 25 August 2016, https://clinicaltrials.gov/ct2/show/NCT02878278.

CREBBP cooperates with the cell cycle machinery to attenuate chidamide sensitivity in relapsed/refractory diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) exhibits frequent inactivating mutations of the histone acetyltransferase CREBBP, highlighting the attractiveness of targeting CREBBP deficiency as a therapeutic strategy. In this study, we demonstrate that chidamide, a novel histone deacetylase (HDAC) inhibitor, is effective in treating a subgroup of relapsed/refractory DLBCL patients, achieving an overall response rate (ORR) of 25.0% and a complete response (CR) rate of 15.0%. However, the clinical response to chidamide remains poor, as most patients exhibit resistance, hampering the clinical utility of the drug. Functional in vitro and in vivo studies have shown that CREBBP loss of function is correlated with chidamide sensitivity, which is associated with modulation of the cell cycle machinery. A combinatorial drug screening of 130 kinase inhibitors targeting cell cycle regulators identified AURKA inhibitors, which inhibit the G2/M transition during the cell cycle, as top candidates that synergistically enhanced the antitumor effects of chidamide in CREBBP-proficient DLBCL cells. Our study demonstrates that CREBBP inactivation can serve as a potential biomarker to predict chidamide sensitivity, while combination of an AURKA inhibitor and chidamide is a novel therapeutic strategy for the treatment of relapsed/refractory DLBCL.