An MDM2 degrader shows potent cytotoxicity to MDM2-overexpressing acute lymphoblastic leukemia cells with minimal toxicity to normal cells/tissues.

The MDM2 oncogene is amplified and/or overexpressed in various human cancers and elevated expression of MDM2 protein acts as a survival factor promoting cancer progression through both p53-dependent and -independent pathways. Here, we report a novel small-molecule chemical compound (MX69-102) that we identified to induce MDM2 protein degradation, resulting in reactivation of p53, inhibition of XIAP, and potent cell growth inhibition and apoptosis in MDM2-overexpressing acute lymphoblastic leukemia (ALL) in vitro and in vivo. We have previously identified a compound (MX69) that binds to the MDM2 C-terminal RING domain and induces MDM2 protein degradation.

Synthesis and biological evaluation of dual MDM2/XIAP inhibitors based on the tetrahydroquinoline scaffold.

Overexpression of both human murine double minute 2 (MDM2) and X-linked inhibitor of apoptosis protein (XIAP) is detected in tumor cells from several cancer types, including childhood acute leukemia lymphoma (ALL), neuroblastoma (NB), and prostate cancer, and is associated with disease progression and treatment resistance. In this report, we described the design and syntheses of a series of dual MDM2/XIAP inhibitors based on the tetrahydroquinoline scaffold from our previously reported lead compound JW-2-107 and tested their cytotoxicity in a panel of human cancer cell lines. The best compound identified in this study is compound 3e.

MYCN mRNA degradation and cancer suppression by a selective small-molecule inhibitor in MYCN-amplified neuroblastoma.

Amplification of the gene leads to its overexpression at both the mRNA and protein levels. Overexpression of mRNA may also have an important role in promoting neuroblastoma (NB) beyond the translation of MYCN protein. In the present study, we report a small molecule compound (MX25-1) that was able to bind to the 3'UTR of mRNA and induce mRNA degradation; this resulted in potent cell-growth inhibition and cell death specifically in -amplified or 3'UTR overexpressing NB cells.

Discovery of -(3,4-Dimethylphenyl)-4-(4-isobutyrylphenyl)-2,3,3a,4,5,9b-hexahydrofuro[3,2-]quinoline-8-sulfonamide as a Potent Dual MDM2/XIAP Inhibitor.

Murine double minute 2 (MDM2) and X-linked inhibitor of apoptosis protein (XIAP) are important cell survival proteins in tumor cells. As a dual MDM2/XIAP inhibitor reported previously, compound MX69 has low potency with an IC value of 7.5 μM against an acute lymphoblastic leukemia cell line EU-1.

Upregulation of p53 through induction of MDM2 degradation: Anthraquinone analogs.

In a previous study, a novel anthraquinone analog BW-AQ-101 was identified as a potent inducer of MDM2 degradation, leading to upregulation of p53 and apoptosis in cell culture studies. In animal models of acute lymphocytic leukemia, treatment with BW-AQ-101 led to complete disease remission. In this study, we systematically investigated the effect of substitution patterns of the core anthraquinone scaffold.

Mutual regulation of MDM4 and TOP2A in cancer cell proliferation.

MDM4 and topoisomerase IIα (TOP2A) are overexpressed in various human cancers. MDM4 acts as an oncoprotein which promotes cancer progression by inhibiting tumor suppressor p53. As a DNA replication- and cell division-regulating enzyme, TOP2A is the main target of many anticancer therapy regimens; however, the exact role of TOP2A in cancer remains elusive.

Inhibition of MDM2 by a Rhein-Derived Compound AQ-101 Suppresses Cancer Development in SCID Mice.

A novel small-molecule anthraquinone (AQ) analogue, AQ-101, which was synthesized through chemical modification of the core structures of rhein, exhibited potent anticancer activity. In the present study, we evaluated the cancer-inhibiting mechanism of AQ-101 and tested the therapeutic potential of this compound for treating cancer in mice. We found that AQ-101 was able to induce MDM2 protein degradation through a self-ubiquitination and proteasome-mediated mechanism.

Discovery of Dual Inhibitors of MDM2 and XIAP for Cancer Treatment.

MDM2 and XIAP are mutually regulated. Binding of MDM2 RING protein to the IRES region on XIAP mRNA results in MDM2 protein stabilization and enhanced XIAP translation. In this study, we developed a protein-RNA fluorescence polarization (FP) assay for high-throughput screening (HTS) of chemical libraries.

Inhibition of MDM2 homodimerization by XIAP IRES stabilizes MDM2, influencing cancer cell survival.

Background: It is known that the MDM2 protein is stabilized when it forms a heterodimer with its partner MDM4, but MDM2 protein stability in its homodimer form is not known. The MDM2 protein contains a C-terminal RING domain that not only functions as an E3 ligase to regulate ubiquitination of p53 and MDM2 itself, but also is characterized to be able to bind several specific cellular mRNAs to regulate gene expression. In this study, we evaluate whether the MDM2 protein stability is regulated by the binding of a specific small RNA (XIAP IRES mRNA).

Targeting MYCN IRES in MYCN-amplified neuroblastoma with miR-375 inhibits tumor growth and sensitizes tumor cells to radiation.

The MYCN oncogene is amplified in 20% of neuroblastomas, leading to its overexpression at both the mRNA and protein levels. MYCN overexpression is strongly associated with advanced disease stage, rapid tumor progression and a worse prognosis. In the present study, we identified microRNA-375 (miR-375) as a negative regulator of MYCN: enforced expression of miR-375 inhibited MYCN-amplified neuroblastoma in vitro and in vivo.

Inhibition of MDM2 by nilotinib contributes to cytotoxicity in both Philadelphia-positive and negative acute lymphoblastic leukemia.

Nilotinib is a selective BCR-ABL tyrosine kinase inhibitor related to imatinib that is more potent than imatinib. Nilotinib is widely used to treat chronic myelogenous leukemia (CML) and Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). The present study identifies Mouse double minute 2 homolog (MDM2) as a target of nilotinib.

Berberine represses DAXX gene transcription and induces cancer cell apoptosis.

Death-domain-associated protein (DAXX) is a multifunctional protein that regulates a wide range of cellular signaling pathways for both cell survival and apoptosis. Regulation of DAXX gene expression remains largely obscure. We recently reported that berberine (BBR), a natural product derived from a plant used in Chinese herbal medicine, downregulates DAXX expression at the transcriptional level.

Triptolide inhibits MDM2 and induces apoptosis in acute lymphoblastic leukemia cells through a p53-independent pathway.

Triptolide, a natural product derived from the Chinese plant Tripterygium wilfordii, is reported to exhibit antitumor effects in a broad range of cancers. The antitumor activity of triptolide is associated with its biologic activities, as it inhibits various proproliferative or antiapoptotic factors that are dominantly expressed in given types of cancer cells. Herein, we show that triptolide induced apoptosis in a subgroup of acute lymphoblastic leukemia (ALL) cells overexpressing the MDM2 oncoprotein by inhibiting MDM2 expression.

Methylation of RASSF1A gene promoter is regulated by p53 and DAXX.

Inactivation of the tumor suppressor Ras-association domain family 1 isoform A (RASSF1A) due to epigenetic silencing occurs in a variety of human cancers, and still largely unknown are the regulators and mechanisms underlying RASSF1A gene promoter methylation. Herein, we report that this methylation is regulated by p53 and death-associated protein 6 (DAXX) in acute lymphoblastic leukemia (ALL). We found that p53 bound to the RASSF1A promoter, recruiting DAXX as well as DNA methyltransferase 1 (DNMT1) for DNA methylation, which subsequently resulted in inactivation of RASSF1A in wild-type p53 ALL cells.

MDM2 regulates vascular endothelial growth factor mRNA stabilization in hypoxia.

Expression of vascular endothelial growth factor (VEGF) increases in cancer cells during hypoxia. Herein, we report that the MDM2 oncoprotein plays a role in hypoxia-mediated VEGF upregulation. In studying the characteristics of MDM2 and VEGF expression in neuroblastoma cells, we found that hypoxia induced significantly higher upregulation of both VEGF mRNA and protein in MDM2-positive cells than in the MDM2-negative cells, even in cells without wild-type (wt) p53.

Crosstalk between MYCN and MDM2-p53 signal pathways regulates tumor cell growth and apoptosis in neuroblastoma.

Previous studies show that the MYCN and MDM2-p53 signal pathways are mutually regulated: MYCN stimulates MDM2 and p53 transcription, whereas MDM2 stabilizes MYCN mRNA and induces its translation. Herein, we report that the interaction between MDM2 and MYCN plays a critical role in MYCN-amplified neuroblastoma tumor cell growth and survival. Distinct from the known role that MDM2 has in regulating tumor promotion in non-MYCN-amplified neuroblastoma, in which MDM2 inhibits p53, we found that MDM2 stimulated tumor growth in MYCN-amplified neuroblastoma in a p53-independent manner.

Degradation of MDM2 by the interaction between berberine and DAXX leads to potent apoptosis in MDM2-overexpressing cancer cells.

Berberine, a natural product derived from a plant used in Chinese herbal medicine, is reported to exhibit anticancer effects; however, its mechanism of action is not clearly defined. Herein, we demonstrate that berberine induces apoptosis in acute lymphoblastic leukemia (ALL) cells by downregulating the MDM2 oncoprotein. The proapoptotic effects of berberine were closely associated with both the MDM2 expression levels and p53 status of a set of ALL cell lines.

Translation of TRAF1 is regulated by IRES-dependent mechanism and stimulated by vincristine.

TRAF1 is a member of the TRAF family, which plays important roles in signal transduction that mediate cell life and death in the immune response, inflammatory and malignant diseases. It is known that TRAF1 transcription is inducible by various cytokines, but little is known about the regulation of its mRNA translation. In the present study, we demonstrated that the human TRAF1 mRNA has an unusually long 5'-UTR that contains internal ribosome entry segment (IRES) regulating its translation.

Regulation of XIAP translation and induction by MDM2 following irradiation.

Increases in protein levels of XIAP in cancer cells have been associated with resistance to apoptosis induced by cellular stress. Herein we demonstrate that the upregulation of XIAP protein levels is regulated by MDM2 at the translational level. MDM2 was found to physically interact with the IRES of the XIAP 5'-UTR, and to positively regulate XIAP IRES activity.

Inhibition of the Akt/survivin pathway synergizes the antileukemia effect of nutlin-3 in acute lymphoblastic leukemia cells.

The phosphatidylinositol 3-kinase (PI3K)/Akt and p53 pathways play antiapoptotic and proapoptotic roles in cell death, respectively. Cancer cell growth and progression are associated with high levels of PI3K/Akt activation by loss of PTEN expression and the inactivation of p53 by MDM2 overexpression. We report that inhibition of PI3K/Akt, either by the PI3K inhibitor Ly294002 or by expression of PTEN, synergized the ability of the MDM2 antagonist nutlin-3 to induce apoptosis in acute lymphoblastic leukemia (ALL).

Tissue factor/FVIIa activates Bcl-2 and prevents doxorubicin-induced apoptosis in neuroblastoma cells.

Background: Tissue factor (TF) is a transmembrane protein that acts as a receptor for activated coagulation factor VII (FVIIa), initiating the coagulation cascade. Recent studies demonstrate that expression of tumor-derived TF also mediates intracellular signaling relevant to tumor growth and apoptosis. Our present study investigates the possible mechanism by which the interaction between TF and FVIIa regulates chemotherapy resistance in neuroblastoma cell lines.

Contribution of STAT3 to the activation of survivin by GM-CSF in CD34+ cell lines.

Objective: Granulocyte macrophage colony-stimulating factor (GM-CSF) has been shown to specifically stimulate proliferation of CD34(+) hematopoietic progenitor cells. Although signal transducers and activators of transcription 3 (STAT3) is believed essential for transduction of GM-CSF-induced cell proliferation, the signaling mediated by STAT3 is not completely understood. Because survivin regulates cell proliferation and survival via its antiapoptotic function, we studied the link between STAT3 signaling and survivin expression in CD34(+) cells.

KLF5 Interacts with p53 in regulating survivin expression in acute lymphoblastic leukemia.

The Kruppel-like factor 5 (KLF5) is a transcription factor that regulates cellular signaling involved in cell proliferation and oncogenesis. Here, we report that KLF5 interacts with tumor suppressor p53 in regulating the expression of the inhibitor-of-apoptosis protein survivin, which may play a role in pathological process of cancer. The core promoter region of survivin contains multiple GT-boxes that have been characterized as KLF5 response elements.

Expression of inhibitor-of-apoptosis protein (IAP) livin by neuroblastoma cells: correlation with prognostic factors and outcome.

Livin is a recently identified member of the Inhibitor-of-Apoptosis protein (IAP) family of antiapoptosis proteins, and expression has been reported in melanoma and some types of carcinoma. We evaluated livin expression in paraffin-embedded tumor tissue from 68 patients with neuroblastoma (NB) and 7 NB cell lines by immunoperoxidase using an anti-livin monoclonal antibody. Eighteen (26.

Transcriptional repression of the eukaryotic initiation factor 4E gene by wild type p53.

The eukaryotic initiation factor 4E (eIF4E) plays important roles in transformation and cancer progression. It is frequently overexpressed in malignant cells, one mechanism of which is through transcriptional activation by c-myc. Here, we report that high level of eIF4E expression and its tumorigenicity could be alternatively associated with defects of p53, since we found that induction of wt-p53 repressed eIF4E expression.