naphthoquinones and Leukemia--Lymphocytic--Chronic--B-Cell

Expression of the transmembrane pseudokinase ROR1 is required for survival of t(1;19)-pre-B-cell acute lymphoblastic leukemia (t(1;19) pre-B-ALL), chronic lymphocytic leukemia, and many solid tumors. However, targeting ROR1 with small-molecules has been challenging due to the absence of ROR1 kinase activity. To identify genes that regulate ROR1 expression and may, therefore, serve as surrogate drug targets, we employed an siRNA screening approach and determined that the epigenetic regulator and E3 ubiquitin ligase, UHRF1, is required for t(1;19) pre-B-ALL cell viability in a ROR1-dependent manner. Upon UHRF1 silencing, ROR1 protein is reduced without altering ROR1 mRNA, and ectopically expressed UHRF1 is sufficient to increase ROR1 levels. Additionally, proteasome inhibition rescues loss of ROR1 protein after UHRF1 silencing, suggesting a role for the proteasome in the UHRF1-ROR1 axis. Finally, we show that ROR1-positive cells are twice as sensitive to the UHRF1-targeting drug, naphthazarin, and undergo increased apoptosis compared to ROR1-negative cells. Naphthazarin elicits reduced expression of UHRF1 and ROR1, and combination of naphthazarin with inhibitors of pre-B cell receptor signaling results in further reduction of cell survival compared with either inhibitor alone. Therefore, our work reveals a mechanism by which UHRF1 stabilizes ROR1, suggesting a potential targeting strategy to inhibit ROR1 in t(1;19) pre-B-ALL and other malignancies.

Topics: CCAAT-Enhancer-Binding Proteins; Cell Line, Tumor; Cell Survival; Down-Regulation; Gene Expression Regulation, Neoplastic; Gene Silencing; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Molecular Targeted Therapy; Naphthoquinones; Receptor Tyrosine Kinase-like Orphan Receptors; Ubiquitin-Protein Ligases

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries, and mainly originates from an accumulation of abnormal B cells caused by the dysregulation of cell proliferation and apoptosis rates. The aberration of apoptosis-related genes in CLL cells results in defective apoptosis of CLL cells in response to traditional therapeutic medicine. Plumbagin (5-hydroxy-2-methyl-1, 4-naphthoquinone), a natural compound from Plumbago zeylinica, has been shown to exhibit pro-apoptotic activities in tumor cells. In the present study, we report that plumbagin effectively inhibited CLL cell viability with a lower dose compared to fludarabine, and inhibited cell proliferation in a dose-dependent manner. In addition, plumbagin promoted accumulation of MEC-1 cells in the S phase, and blocked cell cycle transition of HG3 cells from G0/G1 to S phase. Molecularly, plumbagin markedly induced CLL cell apoptosis through reduction of Bcl-2, but through an increase in the Bax protein level. These results suggest that plumbagin may be considered as a potential anticancer agent for CLL therapy.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Cell Proliferation; Cell Survival; Down-Regulation; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Naphthoquinones; Proto-Oncogene Proteins c-bcl-2; Real-Time Polymerase Chain Reaction; Up-Regulation

Chronic lymphocytic leukemia (CLL) cells located in proliferation centers are constantly stimulated by accessory cells, which provide them with survival and proliferative signals and mediate chemotherapy resistance. Herein, we designed an experimental strategy with the aim of mimicking the microenvironment found in the proliferative centers to specifically target actively proliferating CLL cells. For this, we co-cultured CLL cells and bone marrow stromal cells with concomitant CD40 and Toll-like receptor 9 stimulation. This co-culture system induced proliferation, cell-cycle entry and marked resistance to treatment with fludarabine and bendamustine. Proliferating CLL cells clustered together showed a typical morphology of activated B cells and expressed survivin protein, a member of the inhibitor of apoptosis family that is mainly expressed by CLL cells in the proliferation centers. With the aim of specifically targeting actively proliferating and chemoresistant CLL cells, we investigated the effects of treatment with YM155, a small-molecule survivin inhibitor. YM155 treatment suppressed the co-culture-induced survivin expression and that was sufficient to inhibit proliferation and effectively induce apoptosis particularly in the proliferative subset of CLL cells. Interestingly, sensitivity to YM155 was independent from common prognostic markers, including 17p13.1 deletion. Altogether, these findings provide a rationale for clinical development of YM155 in CLL.

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Agents; Apoptosis; B-Lymphocytes; Bendamustine Hydrochloride; Bone Marrow Cells; CD40 Antigens; Cell Cycle; Cell Proliferation; Coculture Techniques; Drug Resistance, Neoplasm; Female; Gene Deletion; Humans; Imidazoles; Inhibitor of Apoptosis Proteins; Leukemia, Lymphocytic, Chronic, B-Cell; Leukocytes, Mononuclear; Male; Middle Aged; Naphthoquinones; Nitrogen Mustard Compounds; Stromal Cells; Survivin; Toll-Like Receptor 9; Vidarabine

Many tumor cells exhibit a disturbed intracellular redox state resulting in higher levels of reactive oxygen species (ROS). As these contribute to tumor initiation and sustenance, catalytic redox agents combining significant activity with substrate specificity promise high activity and selectivity against oxidatively stressed malignant cells. We describe here the design and synthesis of novel organochalcogen based redox sensor/effector catalysts. Their selective anticancer activity at submicromolar and low micromolar concentrations was established here in a range of tumor entities in various biological systems including cell lines, primary tumor cell cultures, and animal models. In the B-cell derived chronic lymphocytic leukemia (CLL), for instance, such compounds preferentially induce apoptosis in the cancer cells while peripheral blood mononuclear cells (PBMC) from healthy donors and the subset of normal B-cells remain largely unaffected. In support of the concept of sensor/effector based ROS amplification, we are able to demonstrate that underlying this selective activity against CLL cells are pre-existing elevated ROS levels in the leukemic cells compared to their nonmalignant counterparts. Furthermore, the catalysts act in concert with certain chemotherapeutic drugs in several carcinoma cell lines to decrease cell proliferation while showing no such interactions in normal cells. Overall, the high efficacy and selectivity of (redox) catalytic sensor/effector compounds warrant further, extensive testing toward transfer into the clinical arena.

Topics: Animals; Antineoplastic Agents; Apoptosis; Catalysis; Cell Line; Cell Line, Tumor; Drug Screening Assays, Antitumor; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Leukocytes, Mononuclear; Mice; Naphthoquinones; Organoselenium Compounds; Oxidation-Reduction; Quinones; Reactive Oxygen Species; Structure-Activity Relationship; Sulfides; Tellurium

Overexpression of antiapoptotic Bcl-2 family proteins is commonly related with tumor maintenance, progression, and chemoresistance. Inhibition of these antiapoptotic proteins is an attractive approach for cancer therapy. Guided by nuclear magnetic resonance (NMR) binding assays, a series of 5,5' substituted compound 6a (Apogossypolone) derivatives was synthesized and identified pan-active antagonists of antiapoptotic Bcl-2 family proteins, with binding potency in the low micromolar to nanomolar range. Compound 6f inhibits the binding of BH3 peptides to Bcl-X(L), Bcl-2, and Mcl-1 with IC(50) values of 3.10, 3.12, and 2.05 μM, respectively. In a cellular assay, 6f potently inhibits cell growth in several human cancer cell lines in a dose-dependent manner. Compound 6f further displays in vivo efficacy in transgenic mice and demonstrated superior single-agent antitumor efficacy in a PPC-1 mouse xenograft model. Together with its negligible toxicity, compound 6f represents a promising drug lead for the development of novel apoptosis-based therapies for cancer.

Topics: Animals; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Cell Membrane Permeability; Cell Proliferation; Cell Survival; Drug Screening Assays, Antitumor; Drug Stability; Female; Gossypol; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Mice; Mice, Nude; Mice, Transgenic; Microsomes; Models, Molecular; Naphthoquinones; Neoplasm Transplantation; Peptide Fragments; Protein Binding; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Rats; Structure-Activity Relationship; Transplantation, Heterologous

Topics: Aged; Anti-Infective Agents, Urinary; Atovaquone; Biopsy; Diagnosis, Differential; Drug Therapy, Combination; Granuloma; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Lung; Male; Middle Aged; Naphthoquinones; Pneumonia, Pneumocystis; Pseudolymphoma