Runt (Runt domain)‐related transcription factor 1 (RUNX1) is a transcription factor belonging to the core‐binding factor (CBF) family. It is considered to be a master regulator of hematopoiesis and ...has been regarded as a tumor suppressor because it is essential for definitive hematopoiesis in vertebrates. It is one of the most frequent target genes of chromosomal translocation in leukemia, and germ line mutation of RUNX1 causes familial platelet disorder with associated myeloid malignancies. Somatic cell mutations and chromosomal abnormalities, including those of RUNX1, are observed in myelodysplastic syndrome, acute myeloid leukemia, acute lymphoblastic leukemia, and chronic myelomonocytic leukemia at a high frequency. In addition, recent studies reported by us and other groups suggested that WT RUNX1 is needed for survival and proliferation of certain types of leukemia. In this review, we describe the significance and paradoxical requirement of RUNX1 tumor suppressor in hematological malignancies based on recent findings such as “Genetic compensation of RUNX family transcription factors in leukemia,” “RUNX1 inhibition‐induced inhibitory effects on leukemia cells through p53 activation” and our novel promising theory “Cluster regulation of RUNX (CROX)” through the RUNX gene switch method using pyrrole‐imidazole polyamides as a new technique that could contribute to the next generation of leukemia treatment strategies.
Genetic compensation of RUNX family transcription factors in leukemia.
RUNX1 is a member of the core-binding factor family of transcription factors and is indispensable for the establishment of definitive hematopoiesis in vertebrates. RUNX1 is one of the most frequently ...mutated genes in a variety of hematological malignancies. Germ line mutations in RUNX1 cause familial platelet disorder with associated myeloid malignancies. Somatic mutations and chromosomal rearrangements involving RUNX1 are frequently observed in myelodysplastic syndrome and leukemias of myeloid and lymphoid lineages, that is, acute myeloid leukemia, acute lymphoblastic leukemia, and chronic myelomonocytic leukemia. More recent studies suggest that the wild-type RUNX1 is required for growth and survival of certain types of leukemia cells. The purpose of this review is to discuss the current status of our understanding about the role of RUNX1 in hematological malignancies.
Comprehensive inhibition of RUNX1, RUNX2, and RUNX3 led to marked cell suppression compared with inhibition of RUNX1 alone, clarifying that the RUNX family members are important for proliferation and ...maintenance of diverse cancers, and "cluster regulation of RUNX (CROX)" is a very effective strategy to suppress cancer cells. Recent studies reported by us and other groups suggested that wild-type RUNX1 is needed for survival and proliferation of certain types of leukemia, lung cancer, gastric cancer, etc. and for their one of metastatic target sites such as born marrow endothelial niche, suggesting that RUNX1 often functions oncogenic manners in cancer cells. In this review, we describe the significance and paradoxical requirement of RUNX1 tumor suppressor in leukemia and even solid cancers based on recent our findings such as "genetic compensation of RUNX family transcription factors (the compensation mechanism for the total level of RUNX family protein expression)", "RUNX1 inhibition-induced inhibitory effects on leukemia cells and on solid cancers through p53 activation", and "autonomous feedback loop of RUNX1-p53-CBFB in acute myeloid leukemia cells". Taken together, these findings identify a crucial role for the RUNX cluster in the maintenance and progression of cancers and suggest that modulation of the RUNX cluster using the pyrrole-imidazole polyamide gene-switch technology is a potential novel therapeutic approach to control cancers.
In spite of distinct clinical importance, the molecular mechanisms how Additional sex combs-like 1 (ASXL1) mutation contributes to the pathogenesis of premalignant conditions are largely unknown. ...Here, with newly generated knock-in mice, we investigated the biological effects of the mutant. Asxl1
heterozygous (Asxl1
) mice developed phenotypes recapitulating human low-risk myelodysplastic syndromes (MDS), and some of them developed MDS/myeloproliferative neoplasm-like disease after long latency. H2AK119ub1 level around the promoter region of p16Ink4a was significantly decreased in Asxl1
hematopoietic stem cells (HSC), suggesting perturbation of Bmi1-driven H2AK119ub1 histone modification by mutated Asxl1. The mutant form of ASXL1 had no ability to interact with BMI1 as opposed to wild-type ASXL1 protein. Restoration of HSC pool and amelioration of increased apoptosis in hematopoietic stem and progenitor cells were obtained from Asxl1
mice heterozygous for p16Ink4a. These results indicated that loss of protein interaction between Asxl1 mutant and Bmi1 affected the activity of PRC1, and subsequent derepression of p16Ink4a by aberrant histone ubiquitination could induce cellular senescence, resulting in low-risk MDS-like phenotypes in Asxl1
mice. This model provides a useful platform to unveil the molecular basis for hematological disorders induced by ASXL1 mutation and to develop therapeutic strategies for these patients.
Although the biological importance of Krüppel-like factor 4 (KLF4) transcription factor in the terminal differentiation of hematopoietic cells to the monocytes has been well established, the ...underlying mechanisms remain elusive. To clarify the molecular basis of KLF4-mediated monocytic differentiation, we performed detailed genetic studies in acute myeloid leukemia (AML) cells. Here, we report that dihydropyrimidinase like 2 (DPYSL2), also known as CRMP2, is a novel key differentiation mediator downstream of KLF4 in AML cells. Interestingly, we discovered that KLF4-mediated monocytic differentiation is selectively dependent on one specific isoform, DPYSL2A, but not on other DPYSL family genes. Terminal differentiation to the monocytes and proliferation arrest in AML cells induced by genetic or pharmacological upregulation of KLF4 were significantly reversed by short hairpin RNA (shRNA)-mediated selective depletion of DPYSL2A. Chromatin immunoprecipitation assay revealed that KLF4 associates with the proximal gene promoter of DPYSL2A and directly transactivates its expression. Together with the unique expression patterns of KLF4 and DPYSL2 limited to the differentiated monocytes in the hematopoietic system both in human and mouse, the identified KLF4-DPYSL2 axis in leukemia cells may serve as a potential therapeutic target for the development of novel differentiation therapies for patients with AML.
Renal cell carcinoma with Xp11.2 translocation involving the TFE3 gene (TFE3‐RCC) is a recently identified subset of RCC with unique morphology and clinical presentation. The chimeric PRCC‐TFE3 ...protein produced by Xp11.2 translocation has been shown to transcriptionally activate its downstream target genes that play important roles in carcinogenesis and tumor development of TFE3‐RCC. However, the underlying molecular mechanisms remain poorly understood. Here we show that in TFE3‐RCC cells, PRCC‐TFE3 controls heme oxygenase 1 (HMOX1) expression to confer chemoresistance. Inhibition of HMOX1 sensitized the PRCC‐TFE3 expressing cells to genotoxic reagents. We screened for a novel chlorambucil–polyamide conjugate (Chb) to target PRCC‐TFE3‐dependent transcription, and identified Chb16 as a PRCC‐TFE3‐dependent transcriptional inhibitor of HMOX1 expression. Treatment of the patient‐derived cancer cells with Chb16 exhibited senescence and growth arrest, and increased sensitivity of the TFE3‐RCC cells to the genotoxic reagent etoposide. Thus, our data showed that the TFE3‐RCC cells acquired chemoresistance through HMOX1 expression and that inhibition of HMOX1 by Chb16 may be an effective therapeutic strategy for TFE3‐RCC.
PRCC‐TFE3 regulates the expression of heme oxygenase 1 (HMOX1) and confers resistance to chemotherapy in Xp11.2 translocated renal cell carcinoma. A novel chlorambucil–polyamide conjugate, Chb 16, targets PRCC‐TFE3‐dependent transcription, induces senescence and growth arrest, and increases the sensitivity of TFE3‐RCC cells to genotoxic drugs.
The t(8;21) translocation is the most common cytogenetic abnormality in acute myeloid leukemia (AML). Although t(8;21) AML patients have a relatively favorable prognosis, relapse is a frequent ...occurrence, underscoring the need to develop novel therapeutic approaches. Here, we showed that t(8;21) AML is characterized by frequent mutation and overexpression of
CCND2
. Analysis of 19 AML cell lines showed that t(8;21) AML cells had lower IC50 values for the selective CDK4/6 inhibitors palbociclib and abemaciclib than non-t(8;21) AML cells. CDK4/6 inhibitors caused cell cycle arrest at G1 phase and impaired cell proliferation in t(8;21) AML cells. CDK4/6 inhibition decreased MAP-ERK and PI3K-AKT-mTOR signaling pathway activity, induced LC3B-I to LC3B-II conversion, and enhanced autophagosome formation, suggesting autophagy induction. Treatment of t(8;21) AML cells with the autophagy inhibitors chloroquine (CQ) or LY294002 in combination with the CDK4/6 inhibitor abemaciclib significantly increased the percentage of apoptotic (Annexin V positive) cells, whereas CQ or LY294002 single treatment had no significant effects. The effectiveness of co-inhibiting CDK4/6 and autophagy was confirmed in primary t(8;21) AML cells. The results suggest that the combination of CDK4/6 and autophagy inhibitors had a synergistic effect on inducing apoptosis, suggesting a novel therapeutic approach for the treatment of t(8;21) AML.
Runt-related transcription factor 1 (RUNX1) is generally considered to function as a tumor suppressor in the development of leukemia, but a growing body of evidence suggests that it has pro-oncogenic ...properties in acute myeloid leukemia (AML). Here we have demonstrated that the antileukemic effect mediated by RUNX1 depletion is highly dependent on a functional p53-mediated cell death pathway. Increased expression of other RUNX family members, including RUNX2 and RUNX3, compensated for the antitumor effect elicited by RUNX1 silencing, and simultaneous attenuation of all RUNX family members as a cluster led to a much stronger antitumor effect relative to suppression of individual RUNX members. Switching off the RUNX cluster using alkylating agent-conjugated pyrrole-imidazole (PI) polyamides, which were designed to specifically bind to consensus RUNX-binding sequences, was highly effective against AML cells and against several poor-prognosis solid tumors in a xenograft mouse model of AML without notable adverse events. Taken together, these results identify a crucial role for the RUNX cluster in the maintenance and progression of cancer cells and suggest that modulation of the RUNX cluster using the PI polyamide gene-switch technology is a potential strategy to control malignancies.
Neuroblastoma, the most common extracranial solid tumor of childhood, is thought to arise from neural crest‐derived immature cells. The prognosis of patients with high‐risk or recurrent/refractory ...neuroblastoma remains quite poor despite intensive multimodality therapy; therefore, novel therapeutic interventions are required. We examined the expression of a cell adhesion molecule CD146 (melanoma cell adhesion molecule MCAM) by neuroblastoma cell lines and in clinical samples and investigated the anti‐tumor effects of CD146‐targeting treatment for neuroblastoma cells both in vitro and in vivo. CD146 is expressed by 4 cell lines and by most of primary tumors at any stage. Short hairpin RNA‐mediated knockdown of CD146, or treatment with an anti‐CD146 polyclonal antibody, effectively inhibited growth of neuroblastoma cells both in vitro and in vivo, principally due to increased apoptosis via the focal adhesion kinase and/or nuclear factor‐kappa B signaling pathway. Furthermore, the anti‐CD146 polyclonal antibody markedly inhibited tumor growth in immunodeficient mice inoculated with primary neuroblastoma cells. In conclusion, CD146 represents a promising therapeutic target for neuroblastoma.
Targeting CD146 inhibits in vitro proliferation of neuroblastoma (NB) cells and in vivo growth of NB tumors. Exposure of NB cells to the anti‐CD146 antibody led to a significant reduction in survival and anchorage‐independent growth. Intraperitoneal injection of the anti‐CD146 antibody into immunodeficient mice for ~50 d led to a significant inhibition of tumor growth.
Shwachman-Diamond syndrome (SDS), an autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, is caused by mutations in the ...Shwachman-Bodian-Diamond syndrome (SBDS) gene, which plays a role in ribosome biogenesis. Although the causative genes of congenital disorders frequently involve regulation of embryogenesis, the role of the SBDS gene in early hematopoiesis remains unclear, primarily due to the lack of a suitable experimental model for this syndrome. In this study, we established induced pluripotent stem cells (iPSCs) from patients with SDS (SDS-iPSCs) and analyzed their in vitro hematopoietic and endothelial differentiation potentials. SDS-iPSCs generated hematopoietic and endothelial cells less efficiently than iPSCs derived from healthy donors, principally due to the apoptotic predisposition of KDR
CD34
common hemoangiogenic progenitors. By contrast, forced expression of SBDS gene in SDS-iPSCs or treatment with a caspase inhibitor reversed the deficiency in hematopoietic and endothelial development, and decreased apoptosis of their progenitors, mainly via p53-independent mechanisms. Patient-derived iPSCs exhibited the hematological abnormalities associated with SDS even at the earliest hematopoietic stages. These findings will enable us to dissect the pathogenesis of multiple disorders associated with ribosomal dysfunction.
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