ABSTRACT
Acute myeloid leukemia (AML) driven by the activation of EVI1 due to chromosome 3q26/MECOM rearrangements is incurable. Because transcription factors such as EVI1 are notoriously hard to target, insight into the mechanism by which EVI1 drives myeloid transformation could provide alternative avenues for therapy. Applying protein folding predictions combined with proteomics technologies, we demonstrate that interaction of EVI1 with CTBP1 and CTBP2 via a single PLDLS motif is indispensable for leukemic transformation. A 4× PLDLS repeat construct outcompetes binding of EVI1 to CTBP1 and CTBP2 and inhibits proliferation of 3q26/MECOM rearranged AML in vitro and in xenotransplant models. This proof-of-concept study opens the possibility to target one of the most incurable forms of AML with specific EVI1-CTBP inhibitors. This has important implications for other tumor types with aberrant expression of EVI1 and for cancers transformed by different CTBP-dependent oncogenic transcription factors.
Subject(s)
Alcohol Oxidoreductases , DNA-Binding Proteins , Leukemia, Myeloid, Acute , MDS1 and EVI1 Complex Locus Protein , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/metabolism , Leukemia, Myeloid, Acute/pathology , MDS1 and EVI1 Complex Locus Protein/metabolism , MDS1 and EVI1 Complex Locus Protein/genetics , Alcohol Oxidoreductases/metabolism , Alcohol Oxidoreductases/genetics , Humans , Animals , DNA-Binding Proteins/metabolism , DNA-Binding Proteins/genetics , Mice , Co-Repressor Proteins/metabolism , Co-Repressor Proteins/genetics , Protein Binding , Cell Line, Tumor , Cell Proliferation , Cell Transformation, Neoplastic/genetics , Cell Transformation, Neoplastic/metabolism , Transcription Factors/metabolism , Transcription Factors/geneticsABSTRACT
Smac mimetics target inhibitor of apoptosis (IAP) proteins, thereby suppressing their function to facilitate tumor cell death. Here we have evaluated the efficacy of the preclinical Smac-mimetic compound A and the clinical lead birinapant on breast cancer cells. Both exhibited potent in vitro activity in triple-negative breast cancer (TNBC) cells, including those from patient-derived xenograft (PDX) models. Birinapant was further studied using in vivo PDX models of TNBC and estrogen receptor-positive (ER+) breast cancer. Birinapant exhibited single agent activity in all TNBC PDX models and augmented response to docetaxel, the latter through induction of TNF. Transcriptomic analysis of TCGA datasets revealed that genes encoding mediators of Smac-mimetic-induced cell death were expressed at higher levels in TNBC compared with ER+ breast cancer, resulting in a molecular signature associated with responsiveness to Smac mimetics. In addition, the cell death complex was preferentially formed in TNBCs versus ER+ cells in response to Smac mimetics. Taken together, our findings provide a rationale for prospectively selecting patients whose breast tumors contain a competent death receptor signaling pathway for the further evaluation of birinapant in the clinic.
Subject(s)
Antineoplastic Agents/pharmacology , Dipeptides/pharmacology , Gene Expression Regulation, Neoplastic/drug effects , Indoles/pharmacology , Transcriptome/drug effects , Triple Negative Breast Neoplasms/drug therapy , Animals , Cell Line, Tumor , Female , Humans , Mice , Mice, Inbred NOD , Mice, Knockout , Mice, SCIDABSTRACT
JAK2V617F is the most common mutation in patients with BCR-ABL negative myeloproliferative neoplasms (MPNs). The eradication of JAK2V617F hematopoietic stem cells (HSCs) is critical for achieving molecular remissions and cure. We investigate the distinct effects of two therapies, ruxolitinib (JAK1/2 inhibitor) and interferon-alpha (IFN-α), on the disease-initiating HSC population. Whereas ruxolitinib inhibits Stat5 activation in erythroid progenitor populations, it fails to inhibit this same pathway in HSCs. In contrast, IFN-α has direct effects on HSCs. Furthermore, STAT1 phosphorylation and pathway activation is greater after IFN-α stimulation in Jak2V617F murine HSCs with increased induction of reactive oxygen species, DNA damage and reduction in quiescence after chronic IFN-α treatment. Interestingly, ruxolitinib does not block IFN-α induced reactive oxygen species and DNA damage in Jak2V617F murine HSCs in vivo. This work provides a mechanistic rationale informing how pegylated IFN-α reduces JAK2V617F allelic burden in the clinical setting and may inform future clinical efforts to combine ruxolitinib with pegylated IFN-α in patients with MPN.
Subject(s)
Hematopoietic Stem Cells/drug effects , Interferon-alpha/pharmacology , Janus Kinase 2/genetics , Mutation , Myeloproliferative Disorders/drug therapy , Pyrazoles/pharmacology , STAT1 Transcription Factor/metabolism , Animals , Antiviral Agents/pharmacology , Cell Proliferation , Cells, Cultured , Drug Therapy, Combination , Female , Hematopoietic Stem Cells/metabolism , Hematopoietic Stem Cells/pathology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Myeloproliferative Disorders/genetics , Myeloproliferative Disorders/pathology , Nitriles , Pyrimidines , STAT1 Transcription Factor/geneticsABSTRACT
The development of BH3 mimetics, which antagonize prosurvival proteins of the BCL-2 family, represents a potential breakthrough in cancer therapy. Targeting the prosurvival member MCL-1 has been an area of intense interest because it is frequently deregulated in cancer. In breast cancer, MCL-1 is often amplified, and high expression predicts poor patient outcome. We tested the MCL-1 inhibitor S63845 in breast cancer cell lines and patient-derived xenografts with high expression of MCL-1. S63845 displayed synergistic activity with docetaxel in triple-negative breast cancer and with trastuzumab or lapatinib in HER2-amplified breast cancer. Using S63845-resistant cells combined with CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 (CRISPR-associated 9) technology, we identified deletion of BAK and up-regulation of prosurvival proteins as potential mechanisms that confer resistance to S63845 in breast cancer. Collectively, our findings provide a strong rationale for the clinical evaluation of MCL-1 inhibitors in breast cancer.
