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Targeting intrinsic apoptosis and other forms of cell death by BH3-mimetics in glioblastoma.

ABSTRACT: INTRODUCTION:Novel approaches to treat malignant brain tumors are necessary since these neoplasms still display an unfavorable prognosis. Areas covered: In this review, the authors summarize and analyze recent preclinical data that suggest that targeting intrinsic apoptosis may be a suitable strategy for the treatment of malignant gliomas. They focus on the anti-apoptotic Bcl-2 family members of proteins and the recent drug developments in that field with a special focus on BH3-mimetics. With the discovery of BH3-mimetics that interfere with anti-apoptotic Bcl-2 family members in the low nanomolar range significant excitement has been generated towards these class of inhibitors, such as ABT-737, ABT-263 and the most recent successor, ABT-199 which is most advanced with respect to clinical application. The authors discuss the more recent selective inhibitors of Bcl-xL and Mcl-1. Concerning Mcl-1, these novel classes of inhibitors have the potential to impact malignant gliomas since these tumors reveal increased levels of Mcl-1. Expert opinion: The recent development of certain small molecules raises significant hope that intrinsic apoptosis might soon be efficiently targetable for malignancies of the central nervous system. That being said, additional studies are necessary to determine which of the BH3-mimetics might be most suitable.

SUBMITTER: Karpel-Massler G

PROVIDER: S-EPMC6143391 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Targeting intrinsic apoptosis and other forms of cell death by BH3-mimetics in glioblastoma.

Karpel-Massler Georg G Ishida Chiaki Tsuge CT Zhang Yiru Y Halatsch Marc-Eric ME Westhoff M-Andrew MA Siegelin Markus D MD

Expert opinion on drug discovery 20170720 10

<h4>Introduction</h4>Novel approaches to treat malignant brain tumors are necessary since these neoplasms still display an unfavorable prognosis. Areas covered: In this review, the authors summarize and analyze recent preclinical data that suggest that targeting intrinsic apoptosis may be a suitable strategy for the treatment of malignant gliomas. They focus on the anti-apoptotic Bcl-2 family members of proteins and the recent drug developments in that field with a special focus on BH3-mimetics. ...[more]

PMID: 28712306

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Project description:Despite the recent advancement in treating melanoma, options are still limited for patients without BRAF mutations or in relapse from current treatments. BH3 mimetics against members of the BCL-2 family have gained excitement with the recent success in hematological malignancies. However, single drug BH3 mimetic therapy in melanoma has limited effectiveness due to escape by the anti-apoptotic protein MCL-1 and/or survival of melanoma-initiating cells (MICs). We tested the efficacy of the BH3 mimetic combination of A-1210477 (an MCL-1 inhibitor) and ABT-263 (a BCL-2/BCL-XL/BCL-W inhibitor) in killing melanoma, especially MICs. We also sought to better define Dynamin-Related Protein 1 (DRP-1)'s role in melanoma; DRP-1 is known to interact with members of the BCL-2 family and is a possible therapeutic target for melanoma treatment. We used multiple assays (cell viability, apoptosis, bright field, immunoblot, and sphere formation), as well as the CRISPR/Cas9 genome-editing techniques. For clinical relevance, we employed patient samples of different mutation status, including some relapsed from current treatments such as anti-PD-1 immunotherapy. We found the BH3 mimetic combination kill both the MICs and non-MICs (bulk of melanoma) in all cell lines and patient samples irrespective of the mutation status or relapsed state (p?<?0.05). Unexpectedly, the major pro-apoptotic proteins, NOXA and BIM, are not necessary for the combination-induced cell death. Furthermore, the combination impedes the activation of DRP-1, and inhibition of DRP-1 further enhances apoptosis (p?<?0.05). DRP-1 effects in melanoma differ from those seen in other cancer cells. These results provide new insights into BCL-2 family's regulation of the apoptotic pathway in melanoma, and suggest that inhibiting the major anti-apoptotic proteins is sufficient to induce cell death even without involvement from major pro-apoptotic proteins. Importantly, our study also indicates that DRP-1 inhibition is a promising adjuvant for BH3 mimetics in melanoma treatment.

Project description:Basophil granulocytes and mast cells are recognized for their roles in immunity and are central effectors of diverse immunological disorders. Despite their similarities, there is emerging evidence for non-redundant roles of the circulating yet scarce basophils and tissue-resident mast cells, respectively. Because of their importance in allergic pathogenesis, specific induction of apoptosis in basophils and mast cells may represent an interesting novel treatment strategy. The pro-inflammatory cytokine interleukin-3 serves as a key factor for basophil and mouse mast cell survival. Interleukin-3 increases the expression of anti-apoptotic BCL-2 family members, such as BCL-2, BCL-XL or MCL-1; however, little is known how strongly these individual proteins contribute to basophil survival. Here, we were applying small molecule inhibitors called BH3 mimetics, some of which show remarkable success in cancer treatments, to neutralize the function of anti-apoptotic BCL-2 family members. We observed that expression levels of anti-apoptotic BCL-2 proteins do not necessarily correlate with their respective importance for basophil survival. Whereas naive in vitro-differentiated mouse basophils efficiently died upon BCL-2 or BCL-XL inhibition, interleukin-3 priming rendered the cells highly resistant toward apoptosis, and this could only be overcome upon combined targeting of BCL-2 and BCL-XL. Of note, human basophils differed from mouse basophils as they depended on BCL-2 and MCL-1, but not on BCL-XL, for their survival at steady state. On the other hand, and in contrast to mouse basophils, MCL-1 proved critical in mediating survival of interleukin-3 stimulated mouse mast cells, whereas BCL-XL seemed dispensable. Taken together, our results indicate that by choosing the right combination of BH3 mimetic compounds, basophils and mast cells can be efficiently killed, even after stimulation with potent pro-survival cytokines such as interleukin-3. Because of the tolerable side effects of BH3 mimetics, targeting basophils or mast cells for apoptosis opens interesting possibilities for novel treatment approaches.

Project description:Hematologic malignancies (HM) comprise diverse cancers of lymphoid and myeloid origin, including lymphomas (approx. 40%), chronic lymphocytic leukemia (CLL, approx. 15%), multiple myeloma (MM, approx. 15%), acute myeloid leukemia (AML, approx. 10%), and many other diseases. Despite considerable improvement in treatment options and survival parameters in the new millennium, many patients with HM still develop chemotherapy‑refractory diseases and require re-treatment. Because frontline therapies for the majority of HM (except for CLL) are still largely based on classical cytostatics, the relapses are often associated with defects in DNA damage response (DDR) pathways and anti-apoptotic blocks exemplified, respectively, by mutations or deletion of the TP53 tumor suppressor, and overexpression of anti-apoptotic proteins of the B-cell lymphoma 2 (BCL2) family. BCL2 homology 3 (BH3) mimetics represent a novel class of pro-apoptotic anti-cancer agents with a unique mode of action-direct targeting of mitochondria independently of TP53 gene aberrations. Consequently, BH3 mimetics can effectively eliminate even non-dividing malignant cells with adverse molecular cytogenetic alterations. Venetoclax, the nanomolar inhibitor of BCL2 anti-apoptotic protein has been approved for the therapy of CLL and AML. Numerous venetoclax-based combinatorial treatment regimens, next-generation BCL2 inhibitors, and myeloid cell leukemia 1 (MCL1) protein inhibitors, which are another class of BH3 mimetics with promising preclinical results, are currently being tested in several clinical trials in patients with diverse HM. These pivotal trials will soon answer critical questions and concerns about these innovative agents regarding not only their anti-tumor efficacy but also potential side effects, recommended dosages, and the optimal length of therapy as well as identification of reliable biomarkers of sensitivity or resistance. Effective harnessing of the full therapeutic potential of BH3 mimetics is a critical mission as it may directly translate into better management of the aggressive forms of HM and could lead to significantly improved survival parameters and quality of life in patients with urgent medical needs.

Dataset Information

Targeting intrinsic apoptosis and other forms of cell death by BH3-mimetics in glioblastoma.

Publications

Targeting intrinsic apoptosis and other forms of cell death by BH3-mimetics in glioblastoma.

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