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Inhibition of DDX3 modulates immune signaling in aggressive breast cancers
Farhad Vesuna1, Paul T Winnard1, Marise Heerma van Voss1
1Division of Cancer Imaging Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
Abstract:
Triple-negative breast cancers (TNBCs) and inflammatory breast cancer (IBC) are by far the most deadly among all breast cancer subtypes mainly due to being resistant to current treatments. Existing therapies for TNBC and IBC are inadequate due to a limited number of targetable biomarkers and the heterogeneous nature of this disease. In our ongoing search to identify targetable biomarkers for TNBC and IBC, we have found that a member of the RNA helicase protein family, DDX3, is overexpressed in IBC and can be targeted by a small molecule inhibitor which we rationally synthesized, referred to as RK-33. Preliminary data indicate that RK-33 can efficiently and specifically kill TNBC and IBC cell lines without affecting normal breast cells. In the present study, we demonstrate the effectiveness of targeting DDX3 with RK-33 to induce cell death, decrease mammosphere formation, and alter the self-renewal capacity of IBC cells. Additionally, RK-33 was able to disrupt inflammatory cytokine expression in IBC cells. Furthermore, we show that RK-33 sequesters β-catenin in the cytoplasm and decreases Survivin levels in TNBC cells. Moreover, targeting DDX3 with RK-33 promotes multipolar division, leading to cellular death. Importantly, the use of RK-33 also converts high glycolytic tumors to a low glycolytic state, resulting in decreased lactate levels, inhibiting tumor growth, and activating the immune system in an immunocompetent preclinical model of TNBC. Collectively, our data supports the use of RK-33 as a novel therapeutic option for treating TNBC and IBCs.
Insights
A novel small molecule inhibitor, RK-33, targets DDX3 to effectively kill triple-negative breast cancer (TNBC) and inflammatory breast cancer (IBC) cells. This targeted therapy shows promise by reducing tumor growth and activating the immune system.
Area of Science:
- Oncology
- Molecular Biology
- Drug Discovery
Background:
- Triple-negative breast cancer (TNBC) and inflammatory breast cancer (IBC) are aggressive subtypes with limited treatment options.
- Therapeutic resistance in TNBC and IBC stems from a lack of specific biomarkers and disease heterogeneity.
- DDX3, an RNA helicase, is overexpressed in IBC and presents a potential therapeutic target.
Purpose of the Study:
- To investigate the efficacy of a novel small molecule inhibitor, RK-33, targeting DDX3 in TNBC and IBC.
- To evaluate RK-33's impact on cancer cell viability, self-renewal, and tumor microenvironment.
- To assess RK-33's therapeutic potential in preclinical models of TNBC.
Main Methods:
- Synthesis and application of RK-33, a small molecule inhibitor of DDX3.
- In vitro studies using TNBC and IBC cell lines to assess cell death, mammosphere formation, and self-renewal.
- Analysis of cytokine expression, beta-catenin localization, Survivin levels, and cell division patterns.
- In vivo studies in immunocompetent preclinical models of TNBC to evaluate tumor glycolysis, growth, and immune response.
Main Results:
- RK-33 selectively kills TNBC and IBC cells while sparing normal breast cells.
- Targeting DDX3 with RK-33 induces cell death, reduces mammosphere formation, and impairs self-renewal in IBC cells.
- RK-33 alters inflammatory cytokine expression, sequesters beta-catenin, decreases Survivin, and promotes multipolar division.
- RK-33 treatment shifts tumors from a high glycolytic to a low glycolytic state, reducing lactate, inhibiting growth, and activating the immune system in vivo.
Conclusions:
- RK-33 demonstrates significant efficacy in targeting DDX3 for the treatment of TNBC and IBC.
- RK-33 exhibits a multi-faceted mechanism of action, including direct cytotoxicity and modulation of the tumor microenvironment.
- RK-33 represents a promising novel therapeutic candidate for aggressive breast cancer subtypes.
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