Dual-Targeted Therapy Circumvents Non-Genetic Drug Resistance to Targeted Therapy

The introduction of various targeted agents into the armamentarium of cancer treatment has revolutionized the standard care of patients with cancer. However, like conventional chemotherapy, drug resistance, either preexisting (primary or intrinsic resistance) or developed following treatment (secondary or acquired resistance), remains the Achilles heel of all targeted agents with no exception, via either genetic or non-genetic mechanisms. In the latter, emerging evidence supports the notion that intracellular signaling pathways for tumor cell survival act as a mutually interdependent network via extensive cross-talks and feedback loops. Thus, dysregulations of multiple signaling pathways usually join forces to drive oncogenesis, tumor progression, invasion, metastasis, and drug resistance, thereby providing a basis for so-called “bypass” mechanisms underlying non-genetic resistance in response to targeted agents. In this context, simultaneous interruption of two or more related targets or pathways (an approach called dual-targeted therapy, DTT), via either linear or parallel inhibition, is required to deal with such a form of drug resistance to targeted agents that specifically inhibit a single oncoprotein or oncogenic pathway. Together, while most types of tumor cells are often addicted to two or more targets or pathways or can switch their dependency between them, DTT targeting either intrinsically activated or drug-induced compensatory targets/pathways would efficiently overcome drug resistance caused by non-genetic events, with a great opportunity that those resistant cells might be particularly more vulnerable. In this review article, we discuss, with our experience, diverse mechanisms for non-genetic resistance to targeted agents and the rationales to circumvent them in the treatment of cancer, emphasizing hematologic malignancies.

Diverse Epigenetic Regulations of Macrophages in Atherosclerosis

Emerging research on epigenetics has resulted in many novel discoveries in atherosclerosis (AS), an inflammaging-associated disease characterized by chronic inflammation primarily driven by macrophages. The bulk of evidence has demonstrated the central role of epigenetic machinery in macrophage polarization to pro- (M1-like) or anti-inflammatory (M2-like) phenotype. An increasing number of epigenetic alterations and their modifiers involved in reprogramming macrophages by regulating DNA methylation or histone modifications (e.g., methylation, acetylation, and recently lactylation) have been identified. They may act to determine or skew the direction of macrophage polarization in AS lesions, thereby representing a promising target. Here we describe the current understanding of the epigenetic machinery involving macrophage polarization, to shed light on chronic inflammation-driving onset and progression of inflammaging-associated diseases, using AS as a prototypic example, and discuss the challenge for developing effective therapies targeting the epigenetic modifiers against these diseases, particularly highlighting a potential strategy based on epigenetically-governed repolarization from M1-like to M2-like phenotype.

Detection of Host Cell Gene/HPV DNA Methylation Markers: A Promising Triage Approach for Cervical Cancer

Cervical cancer is the most prevalent gynecologic malignancy, especially in women of low- and middle-income countries (LMICs). With a better understanding of the etiology and pathogenesis of cervical cancer, it has been well accepted that this type of cancer can be prevented and treated via early screening. Due to its higher sensitivity than cytology to identify precursor lesions of cervical cancer, detection of high-risk human papillomavirus (HR-HPV) DNA has been implemented as the primary screening approach. However, a high referral rate for colposcopy after HR-HPV DNA detection due to its low specificity in HR-HPV screening often leads to overtreatment and thus increases the healthcare burden. Emerging evidence has demonstrated that detection of host cell gene and/or HPV DNA methylation represents a promising approach for the early triage of cervical cancer in HR-HPV-positive women owing to its convenience and comparable performance to cytology, particularly in LMICs with limited healthcare resources. While numerous potential markers involving DNA methylation of host cell genes and the HPV genome have been identified thus far, it is crucial to define which genes or panels involving host and/or HPV are feasible and appropriate for large-scale screening and triage. An ideal approach for screening and triage of CIN/ICC requires high sensitivity and adequate specificity and is suitable for self-sampling and inexpensive to allow population-based screening, particularly in LMICs. In this review, we summarize the markers of host cell gene/HR-HPV DNA methylation and discuss their triage performance and feasibility for high-grade precancerous cervical intraepithelial neoplasia or worse (CIN2+ and CIN3+) in HR-HPV-positive women.

A cyclodextrin-based nanoformulation achieves co-delivery of ginsenoside Rg3 and quercetin for chemo-immunotherapy in colorectal cancer

The immune checkpoint blockade therapy has profoundly revolutionized the field of cancer immunotherapy. However, despite great promise for a variety of cancers, the efficacy of immune checkpoint inhibitors is still low in colorectal cancer (CRC). This is mainly due to the immunosuppressive feature of the tumor microenvironment (TME). Emerging evidence reveals that certain chemotherapeutic drugs induce immunogenic cell death (ICD), demonstrating great potential for remodeling the immunosuppressive TME. In this study, the potential of ginsenoside Rg3 (Rg3) as an ICD inducer against CRC cells was confirmed using in vitro and in vivo experimental approaches. The ICD efficacy of Rg3 could be significantly enhanced by quercetin (QTN) that elicited reactive oxygen species (ROS). To ameliorate in vivo delivery barriers associated with chemotherapeutic drugs, a folate (FA)-targeted polyethylene glycol (PEG)-modified amphiphilic cyclodextrin nanoparticle (NP) was developed for co-encapsulation of Rg3 and QTN. The resultant nanoformulation (CD-PEG-FA.Rg3.QTN) significantly prolonged blood circulation and enhanced tumor targeting in an orthotopic CRC mouse model, resulting in the conversion of immunosuppressive TME. Furthermore, the CD-PEG-FA.Rg3.QTN achieved significantly longer survival of animals in combination with Anti-PD-L1. The study provides a promising strategy for the treatment of CRC.

The mechanisms and therapeutic targets of ferroptosis in cancer

INTRODUCTION

Ferroptosis, a form of programmed cell death, is mediated primarily by lipid peroxidation via a unique iron-dependent process. The mechanisms of ferroptosis involve the metabolisms of amino acids, irons, and lipids, and the regulation of antioxidant systems. Evidence supports the roles of ferroptosis in cancer, while metabolic reprogramming (a hallmark of cancer) renders tumor cells highly vulnerable to ferroptosis and thus provides a rationale for ferroptosis-targeted therapy for cancer.

AREA COVERED

This article examines the current understanding of the mechanisms and related signaling pathways involving ferroptosis; it focuses on novel targets in cancer and its treatment and drug resistance. The development of ferroptosis-targeted therapy, especially in combination with conventional or non-conventional therapies, are considered with dilemmas and key questions in this research area.

EXPERT OPINION

An increasing number of potential targets and ferroptosis inducers (FINs) have been identified to treat cancer. However, no specific FIN has entered clinical trials thus far, likely due to poor efficacy and high toxicity in vivo. Thus, new FINs with high selectivity and bioavailability are required to target tumor cells more specifically and potently. Particularly, the combination of FINs with chemotherapy, radiotherapy, targeted therapy, and immunotherapy warrants clinical investigation in the future.

Modulation of macrophages by a paeoniflorin-loaded hyaluronic acid-based hydrogel promotes diabetic wound healing

The impaired wound healing in diabetes is a central concern of healthcare worldwide. However, current treatments often fail due to the complexity of diabetic wounds, and thus, emerging therapeutic approaches are needed. Macrophages, a prominent immune cell in the wound, play key roles in tissue repair and regeneration. Recent evidence has demonstrated that macrophages in diabetic wounds maintain a persistent proinflammatory phenotype that causes the failure of healing. Therefore, modulation of macrophages provides great promise for wound healing in diabetic patients. In this study, the potential of paeoniflorin (PF, a chemical compound derived from the herb Paeonia lactiflora) for the transition of macrophages from M1 (proinflammatory phenotype) to M2 (anti-inflammatory/prohealing phenotype) was confirmed using ex vivo and in vivo experimental approaches. A hydrogel based on high molecular weight hyaluronic acid (HA) was developed for local administration of PF in experimental diabetic mice with a full-thickness wound. The resultant formulation (HA-PF) was able to significantly promote cutaneous healing as compared to INTRASITE Gel (a commercial hydrogel wound dressing). This outcome was accompanied by the amelioration of inflammation, the improvement of angiogenesis, and re-epithelialization, and the deposition of collagen. Our study indicates the significant potential of HA-PF for clinical translation in diabetic wound healing.

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PF modulates the phenotype and function of macrophages from M1 to M2.

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The PF-loaded HA-based hydrogel significantly promotes diabetic wound healing.

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The healing efficacy results from the capacity of fulfilling the inflammation, proliferation, and maturation stages.

IAP and HDAC inhibitors interact synergistically in myeloma cells through noncanonical NF-κB- and caspase-8-dependent mechanisms

Interactions between the inhibitor of apoptosis protein antagonist LCL161 and the histone deacetylase inhibitor panobinostat (LBH589) were examined in human multiple myeloma (MM) cells. LCL161 and panobinostat interacted synergistically to induce apoptosis in diverse MM cell lines, including those resistant to bortezomib (PS-R). Similar interactions were observed with other histone deacetylase inhibitors (MS-275) or inhibitors of apoptosis protein antagonists (birinapant). These events were associated with downregulation of the noncanonical (but not the canonical) NF-κB pathway and activation of the extrinsic, caspase-8-related apoptotic cascade. Coexposure of MM cells to LCL161/LBH589 induced TRAF3 upregulation and led to TRAF2 and NIK downregulation, diminished expression of BCL-XL, and induction of γH2A.X. Ectopic expression of TRAF2, NIK, or BCL-XL, or short hairpin RNA TRAF3 knock-down, significantly reduced LCL161/LBH589 lethality, as did ectopic expression of dominant-negative FADD. Stromal/microenvironmental factors failed to diminish LCL161/LBH589-induced cell death. The LCL161/LBH589 regimen significantly increased cell killing in primary CD138+ cells (N = 31) and was particularly effective in diminishing the primitive progenitor cell-enriched CD138-/19+/20+/27+ population (N = 23) but was nontoxic to normal CD34+ cells. Finally, combined LCL161/LBH589 treatment significantly increased survival compared with single-agent treatment in an immunocompetent 5TGM1 murine MM model. Together, these findings argue that LCL161 interacts synergistically with LBH589 in MM cells through a process involving inactivation of the noncanonical NF-κB pathway and activation of the extrinsic apoptotic pathway, upregulation of TRAF3, and downregulation of TRAF2/BCL-XL. Notably, this regimen overcomes various forms of resistance, is active against primary MM cells, and displays significant in vivo activity. This strategy warrants further consideration in MM.

Decoding DNA methylation in epigenetics of multiple myeloma

Dysregulation of DNA methylation in B cells has been observed during their neoplastic transformation and therefore closely associated with various B-cell malignancies including multiple myeloma (MM), a malignancy of terminally differentiated plasma cells. Emerging evidence has unveiled pronounced alterations in DNA methylation in MM, including both global and gene-specific changes that can affect genome stability and gene transcription. Moreover, dysregulated expression of DNA methylation-modifying enzymes has been related with myelomagenesis, disease progression, and poor prognosis. However, the functional roles of the epigenetic abnormalities involving DNA methylation in MM remain elusive. In this article, we review current understanding of the alterations in DNA methylome and DNA methylation modifiers in MM, particularly focusing on DNA methyltransferases (DNMTs) and tet methylcytosine dioxygenases (TETs). We also discuss how these DNA methylation modifiers may be regulated and function in MM cells, therefore providing a rationale for developing novel epigenetic therapies targeting DNA methylation in MM.

Preclinical evaluation of a regimen combining chidamide and ABT-199 in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous myeloid neoplasm with poor clinical outcome, despite the great progress in treatment in recent years. The selective Bcl-2 inhibitor venetoclax (ABT-199) in combination therapy has been approved for the treatment of newly diagnosed AML patients who are ineligible for intensive chemotherapy, but resistance can be acquired through the upregulation of alternative antiapoptotic proteins. Here, we reported that a newly emerged histone deacetylase inhibitor, chidamide (CS055), at low-cytotoxicity dose enhanced the anti-AML activity of ABT-199, while sparing normal hematopoietic progenitor cells. Moreover, we also found that chidamide showed a superior resensitization effect than romidepsin in potentiation of ABT-199 lethality. Inhibition of multiple HDACs rather than some single component might be required. The combination therapy was also effective in primary AML blasts and stem/progenitor cells regardless of disease status and genetic aberrance, as well as in a patient-derived xenograft model carrying FLT3-ITD mutation. Mechanistically, CS055 promoted leukemia suppression through DNA double-strand break and altered unbalance of anti- and pro-apoptotic proteins (e.g., Mcl-1 and Bcl-xL downregulation, and Bim upregulation). Taken together, these results show the high therapeutic potential of ABT-199/CS055 combination in AML treatment, representing a potent and alternative salvage therapy for the treatment of relapsed and refractory patients with AML.

Pegfilgrastim improves the outcomes of mobilization and engraftment in autologous hematopoietic stem cell transplantation for the treatment of multiple myeloma

Autologous stem cell transplantation (ASCT) is the only curable therapy for multiple myeloma (MM), while its success primarily relies on mobilization to obtain sufficient hematopoietic stem/progenitor cells (HPC). Although the role of Pegfilgrastim (PEG), a novel PEGylated form of the recombinant G-CSF filgrastim (FIL), in mobilization has been demonstrated, it remains unclear whether this approach is cost-effective in MM treatment. Here, we performed a real-world analysis to evaluate the efficacy and cost of PEG for mobilization in a cohort of MM patients, of which 53% carried high-risk cytogenetic abnormalities. A total of 91 patients who received either a single dose of PEG (6 or 12 mg, n = 42) or multiple dosing of 10 μg/kg/day FIL (n = 49) after chemotherapy for HPC mobilization were included. The yield of MNCs and CD34⁺ cells per milliliter of blood collected via apheresis was significantly greater in the PEG group than that in the FIL group (P = 0.014 and P = 0.038). Mobilization with PEG yielded significantly higher median number of collected CD34⁺ cells than FIL (5.56 vs. 4.82 × 10⁶/kg; P = 0.038). Moreover, the average time-to-recovery of leukocytes and platelets after transplantation was markedly shorter in the PEG group than that in the FIL group (leukocyte, 11.59 ± 1.98 vs 12.93 ± 2.83 days, P = 0.019; platelet, 12.86 ± 2.62 vs 14.80 ± 5.47, P = 0.085). However, the total cost of mobilization and apheresis using PEG or FIL was comparable (P = 0.486). Of note, mobilization with 12 mg PEG further shortened time-to-recovery of leukocytes (10.64 ± 0.51 vs. 12.04 ± 2.26 days, P = 0.05) and platelets (10.60 ± 2.89 vs. 13.33 ± 2.35 days, P = 0.031) compared with 6 mg PEG. Our results support a notion that PEG (especially 12 mg) combined with chemotherapy is a cost-effective and convenient regimen of mobilization, which might improve the outcome of ASCT in MM.

NO up-regulates migraine-related CGRP via activation of an Akt/GSK-3β/NF-κB signaling cascade in trigeminal ganglion neurons

The release of the neuropeptide CGRP from the trigeminal ganglion neurons (TGNs) plays a central role in migraine. Whereas CGRP can activate NO release from ganglionic glial cells, NO in turn enhances CGRP release. However, it remains unclear how NO promotes CGRP release. Here, we report that the NO donor SNAP triggered CGRP release from cultured primary TGNs. This event was associated with GSK-3β activation and Akt inactivation. Immunofluorescent staining revealed that GSK-3β primarily located in neurons. Furthermore, GSK-3β inhibition resulted in a marked reduction in expression of CGRP as well as other migraine-related factors, including substance P, cholecystokinin, and prostaglandin E2. Last, exposure to SNAP also activated NF-κB, while NF-κB inhibition prevented the induction of CGRP by SNAP. Interestingly, this event was blocked by GSK-3β inhibition, in association with inhibition of NF-κB/p65 expression and nuclear translocation. Together, these findings argue that NO could stimulate TGNs to release of CGRP as well as other migraine-related factors, likely by activating GSK-3β, providing a novel mechanism underlying a potential feed-forward loop between NO and CGRP in migraine. They also raise a possibility that GSK-3β might act to trigger migraine through activation of NF-κB, suggesting a link between neuroinflammation and migraine.

Impairment of hypoxia-induced angiogenesis by LDL involves a HIF-centered signaling network linking inflammatory TNFα and angiogenic VEGF

Hypoxia inducible factors (HIFs) mediate angiogenesis via up-regulation of various pro-angiogenic factors (particularly VEGF) in response to hypoxia. Here, we report that hypoxia unexpectedly induced robust production of the pro-inflammatory factor TNFα by endothelial cells (ECs), suggesting an autocrine loop that in turn activated HIFs via an NF-κB-dependent process, resulting in production of VEGF and thereby promotion of angiogenesis. In contrast, low-density lipoprotein (LDL) prevented expression of HIFs in ECs exposed to either hypoxia or TNFα, while knockdown of either HIF-1α or HIF-2α strikingly attenuated hypoxia-induced production of VEGF by ECs as well as EC colony formation and tube formation. Significantly, LDL attenuated hypoxia-induced angiogenesis by disrupting the TNFα/NF-κB/HIF/VEGF signaling cascade via down-regulation of the TNF receptor TNF-R1, rather than TNFα itself, and multiple key components of both canonical and non-canonical NF-κB pathways. By doing so, LDL was able to either inhibit or down-regulate a wide spectrum of HIF-dependent pro-angiogenic downstream targets and signals. Together, these findings argue existence of a self-regulatory TNFα/NF-κB/HIF/VEGF signaling network in ECs, which mediates and fine-tones angiogenesis, at least in response to hypoxia. They also suggest that LDL impairs angiogenesis by disrupting this network, which might represent a novel mechanism underlying anti-angiogenic property of LDL.

Co-inhibition of HDAC and MLL-menin interaction targets MLL-rearranged acute myeloid leukemia cells via disruption of DNA damage checkpoint and DNA repair

While the aberrant translocation of the mixed-lineage leukemia (MLL) gene drives pathogenesis of acute myeloid leukemia (AML), it represents an independent predictor for poor prognosis of adult AML patients. Thus, small molecule inhibitors targeting menin-MLL fusion protein interaction have been emerging for the treatment of MLL-rearranged AML. As both inhibitors of histone deacetylase (HDAC) and menin-MLL interaction target the transcription-regulatory machinery involving epigenetic regulation of chromatin remodeling that governs the expression of genes involved in tumorigenesis, we hypothesized that these two classes of agents might interact to kill MLL-rearranged (MLL-r) AML cells. Here, we report that the combination treatment with subtoxic doses of the HDAC inhibitor chidamide and the menin-MLL interaction inhibitor MI-3 displayed a highly synergistic anti-tumor activity against human MLL-r AML cells in vitro and in vivo, but not those without this genetic aberration. Mechanistically, co-exposure to chidamide and MI-3 led to robust apoptosis in MLL-r AML cells, in association with loss of mitochondrial membrane potential and a sharp increase in ROS generation. Combined treatment also disrupted DNA damage checkpoint at the level of CHK1 and CHK2 kinases, rather than their upstream kinases (ATR and ATM), as well as DNA repair likely via homologous recombination (HR), but not non-homologous end joining (NHEJ). Genome-wide RNAseq revealed gene expression alterations involving several potential signaling pathways (e.g., cell cycle, DNA repair, MAPK, NF-κB) that might account for or contribute to the mechanisms of action underlying anti-leukemia activity of chidamide and MI-3 as a single agent and particularly in combination in MLL-r AML. Collectively, these findings provide a preclinical basis for further clinical investigation of this novel targeted strategy combining HDAC and Menin-MLL interaction inhibitors to improve therapeutic outcomes in a subset of patients with poor-prognostic MLL-r leukemia.

Cell cycle regulation and hematologic malignancies

A complex network precisely regulates the cell cycle through the G₁, S, G₂, and M phases and is the basis for cell division under physiological and pathological conditions. On the one hand, the transition from one phase to another as well as the progression within each phase is driven by the specific cyclin-dependent kinases (CDKs; e.g., CDK1, CDK2, CDK4, CDK6, and CDK7), together with their exclusive partner cyclins (e.g., cyclin A1, B1, D1–3, and E1). On the other hand, these phases are negatively regulated by endogenous CDK inhibitors such as p16^ink4a, p18^ink4c, p19^ink4d, p21^cip1, and p27^kip1. In addition, several checkpoints control the commitment of cells to replicate DNA and undergo mitosis, thereby avoiding the passage of genomic errors to daughter cells. CDKs are often constitutively activated in cancer, which is characterized by the uncontrolled proliferation of transformed cells, due to genetic and epigenetic abnormalities in the genes involved in the cell cycle. Moreover, several oncogenes and defective tumor suppressors promote malignant changes by stimulating cell cycle entry and progression or disrupting DNA damage responses, including the cell cycle checkpoints, DNA repair mechanisms, and apoptosis. Thus, genes or proteins related to cell cycle regulation remain the main targets of interest in the treatment of various cancer types, including hematologic malignancies. In this context, advances in the understanding of the cell cycle regulatory machinery provide a basis for the development of novel therapeutic approaches. The present article summarizes the pathways as well as their genetic and epigenetic alterations that regulate the cell cycle; moreover, it discusses the various approved or potential therapeutic targets associated with the cell cycle, focusing on hematologic malignancies.

The IAP antagonist birinapant potentiates bortezomib anti-myeloma activity in vitro and in vivo

Background

Mechanisms by which Smac mimetics (SMs) interact with proteasome inhibitors (e.g., bortezomib) are largely unknown, particularly in multiple myeloma (MM), a disease in which bortezomib represents a mainstay of therapy.

Methods

Interactions between the clinically relevant IAP (inhibitor of apoptosis protein) antagonist birinapant (TL32711) and the proteasome inhibitor bortezomib were investigated in multiple myeloma (MM) cell lines and primary cells, as well as in vivo models. Induction of apoptosis and changes in gene and protein expression were monitored using MM cell lines and confirmed in primary MM cell populations. Genetically modified cells (e.g., exhibiting shRNA knockdown or ectopic expression) were employed to evaluate the functional significance of birinapant/bortezomib-induced changes in protein levels. A MM xenograft model was used to evaluate the in vivo activity of the birinapant/bortezomib regimen.

Results

Birinapant and bortezomib synergistically induced apoptosis in diverse cell lines, including bortezomib-resistant cells (PS-R). The regimen robustly downregulated cIAP1/2 but not the canonical NF-κB pathway, reflected by p65 phosphorylation and nuclear accumulation. In contrast, the bortezomib/birinapant regimen upregulated TRAF3, downregulated TRAF2, and diminished p52 processing and BCL-X_L expression, consistent with disruption of the non-canonical NF-κB pathway. TRAF3 knockdown, ectopic TRAF2, or BCL-X_L expression significantly diminished birinapant/bortezomib toxicity. The regimen sharply increased extrinsic apoptotic pathway activation, and cells expressing dominant-negative FADD or caspase-8 displayed markedly reduced birinapant/bortezomib sensitivity. Primary CD138⁺ (n = 43) and primitive MM populations (CD138⁻/19⁺/20⁺/27⁺; n = 31) but not normal CD34⁺ cells exhibited significantly enhanced toxicity with combined treatment (P < 0.0001). The regimen was also fully active in the presence of HS-5 stromal cells or growth factors (e.g., IL-6 and VEGF). Finally, the regimen was well tolerated and significantly increased survival (P < 0.05 and P < 0.001) compared to single agents in a MM xenograft model. Combined treatment also downregulated cIAP1/2 and p52 while increasing PARP cleavage in MM cells in vivo.

Conclusions

Our data suggest that birinapant and bortezomib interact synergistically in MM cells, including those resistant to bortezomib, through inactivation of the non-canonical NF-κB and activation of the extrinsic apoptotic pathway both in vitro and in vivo. They also argue that a strategy combining cIAP antagonists and proteasome inhibitors warrants attention in MM.

Electronic supplementary material

The online version of this article (10.1186/s13045-019-0713-x) contains supplementary material, which is available to authorized users.

High COX-2 expression contributes to a poor prognosis through the inhibition of chemotherapy-induced senescence in nasopharyngeal carcinoma

Resistance to radiotherapy and chemotherapy currently represents one of the major reasons for therapeutic failure in nasopharyngeal carcinoma (NPC). However, the mechanisms underlying resistance to chemotherapy in NPC remain unclear. In this study, cell counting assay, cell cycle assay and senescence associated β-galactosidase activity were performed to evaluate cell growth, proliferation and senescence, respectively. We found that the aberrant expression of cyclooxygenase-2 (COX-2) was associated with a poor outcome and recurrance in patients with NPC. In NPC cells, COX-2 overexpression increased cell proliferation, inhibited cellular senescence and resulted in chemoresistance, while the knockdown of COX-2 reduced cell proliferation, promoted cellular senescence and overcame chemoresistance. Furthermore, fibroblasts from COX-2 knockout mice exhibited cellular senescence, particularly when treated with chemotherapeutic agents. Mechanistically, COX-2 interacted with p53 protein and inhibited cellular senescence, which resulted in chemotherapeutic resistance. On the whole, these findings indicate that COX-2 may play a critical role in chemotherapeutic resistance in NPC via the inhibition of chemotherapy-induced senescence via the inactivation of p53. This study provides experimental evidence for the preclinical value of increasing chemotherapy-induced senescence by targeting COX-2 as an effective antitumor treatment in patients with recurrent NPC.

ARNT/HIF-1β links high-risk 1q21 gain and microenvironmental hypoxia to drug resistance and poor prognosis in multiple myeloma

1q21 gain is a common cytogenetic abnormality featuring high‐risk multiple myeloma (HRMM). However, the molecular mechanism underlying the adverse prognostic effect of 1q21 gain remains largely unclear. Here, we report that ARNT/HIF‐1β, a 1q21 gene, is highly expressed in HRMM and induced by microenvironmental hypoxia, which confers drug resistance and correlates with inferior outcome. Analysis of the gene expression profile database revealed that ARNT expression was upregulated in MM and increased with disease progression or in HRMM subtypes (particularly 1q21 gain), while correlated to shorter overall survival. In a cohort of 40 MM patients, qPCR further validated that ARNT expression was higher in MM patients than normal donors. MM cells carrying 1q21 gain or acquired drug resistance displayed a robust increase in HIF‐1β protein level. Hypoxia induced HIF‐1β expression via a NF‐κB‐dependent process. Notably, HIF‐1β overexpression impaired bortezomib sensitivity, whereas shRNA knockdown of ARNT reversed hypoxia‐mediated drug resistance. Together, these findings suggest that ARNT/HIF‐1β might represent a novel biomarker for risk stratification and prognosis of HRMM patients, as well as a potential therapeutic target for overcoming 1q21 gain‐ or microenvironment‐mediated and acquired drug resistance in MM.

A novel epigenetic AML1-ETO/THAP10/miR-383 mini-circuitry contributes to t(8;21) leukaemogenesis

DNA methylation patterns are frequently deregulated in t(8;21) acute myeloid leukaemia (AML), but little is known of the mechanisms by which specific gene sets become aberrantly methylated. Here, we found that the promoter DNA methylation signature of t(8;21)⁺ AML blasts differs from that of t(8;21)^- AMLs. This study demonstrated that a novel hypermethylated zinc finger-containing protein, THAP10, is a target gene and can be epigenetically suppressed by AML1-ETO at the transcriptional level in t(8;21) AML. Our findings also show that THAP10 is a bona fide target of miR-383 that can be epigenetically activated by the AML1-ETO recruiting co-activator p300. In this study, we demonstrated that epigenetic suppression of THAP10 is the mechanistic link between AML1-ETO fusion proteins and tyrosine kinase cascades. In addition, we showed that THAP10 is a nuclear protein that inhibits myeloid proliferation and promotes differentiation both in vitro and in vivo Altogether, our results revealed an unexpected and important epigenetic mini-circuit of AML1-ETO/THAP10/miR-383 in t(8;21) AML, in which epigenetic suppression of THAP10 predicts a poor clinical outcome and represents a novel therapeutic target.

Characterization of IFNγ-producing natural killer cells induced by cytomegalovirus reactivation after haploidentical hematopoietic stem cell transplantation

During human cytomegalovirus (CMV) infection after umbilical cord blood or HLA-matched hematopoietic stem cell transplantation (HSCT), a population of NKG2C-expressing natural killer (NK) cells expand and persist. The expanded NK cells express high levels of inhibitory killer immunoglobulin-like receptors (KIR) specific for self-HLA and potently produce IFNγ. However, it remains unknown whether similar events would occur after haploidentical HSCT (haplo-HSCT). Here, we demonstrated that IFNγ-producing NK cells were expanded in haplo-HSCT patients with CMV reactivation. We then identified these expanded cells as a subset of CD56^dim NK cells that expressed higher levels of both NKG2C and KIR, but lower level of NKG2A. Functionally, the subset of NK cells expressing NKG2C and self-KIR in patients with CMV reactivation accounted for IFNγ production in response to K562 cells. However, these phenomena were not observed in patients without CMV reactivation. We therefore characterized a subset of NK cells with the CD56^dim, NKG2C⁺, and self-KIR⁺ phenotype that expanded and were responsible for IFNγ production during CMV infection after haplo-HSCT. Together, these findings support a notion that CMV reactivation induces expansion of more mature NK cells with memory-like features, which contributes to long-term control of both CMV infection and leukemia relapse after haplo-HSCT.

XPO1 inhibitor combination therapy with bortezomib or carfilzomib induces nuclear localization of IκBα and overcomes acquired proteasome inhibitor resistance in human multiple myeloma

Acquired proteasome-inhibitor (PI) resistance is a major obstacle in the treatment of multiple myeloma (MM). We investigated whether the clinical XPO1-inhibitor selinexor, when combined with bortezomib or carfilzomib, could overcome acquired resistance in MM. PI-resistant myeloma cell lines both in vitro and in vivo and refractory myeloma patient biopsies were treated with selinexor/bortezomib or carfilzomib and assayed for apoptosis. Mechanistic studies included NFκB pathway protein expression assays, immunofluorescence microscopy, ImageStream flow-cytometry, and proximity-ligation assays. IκBα knockdown and NFκB activity were measured in selinexor/bortezomib-treated MM cells. We found that selinexor restored sensitivity of PI-resistant MM to bortezomib and carfilzomib. Selinexor/bortezomib treatment inhibited PI-resistant MM tumor growth and increased survival in mice. Myeloma cells from PI-refractory MM patients were sensitized by selinexor to bortezomib and carfilzomib without affecting non-myeloma cells. Immunofluorescence microscopy, Western blot, and ImageStream analyses of MM cells showed increases in total and nuclear IκBα by selinexor/bortezomib. Proximity ligation found increased IκBα-NFκB complexes in treated MM cells. IκBα knockdown abrogated selinexor/bortezomib-induced cytotoxicity in MM cells. Selinexor/bortezomib treatment decreased NFκB transcriptional activity. Selinexor, when used with bortezomib or carfilzomib, has the potential to overcome PI drug resistance in MM. Sensitization may be due to inactivation of the NFκB pathway by IκBα.

High-density lipoprotein (HDL) promotes angiogenesis via S1P3-dependent VEGFR2 activation

High-density lipoprotein (HDL) has previously been shown to promote angiogenesis. However, the mechanisms by which HDL enhances the formation of blood vessels remain to be defined. To address this, the effects of HDL on the proliferation, transwell migration and tube formation of human umbilical vein endothelial cells were investigated. By examining the abundance and phosphorylation (i.e., activation) of the vascular endothelial growth factor receptor VEGFR2 and modulating the activity of the sphingosine-1 phosphate receptors S1P1-3 and VEGFR2, we characterized mechanisms controlling angiogenic responses in response to HDL exposure. Here, we report that HDL dose-dependently increased endothelial proliferation, migration and tube formation. These events were in association with increased VEGFR2 abundance and rapid VEGFR2 phosphorylation at Tyr1054/Tyr1059 and Tyr1175 residues in response to HDL. Blockade of VEGFR2 activation by the VEGFR2 inhibitor SU1498 markedly abrogated the pro-angiogenic capacity of HDL. Moreover, the S1P3 inhibitor suramin prevented VEGFR2 expression and abolished endothelial migration and tube formation, while the S1P1 agonist CYM-5442 and the S1P2 inhibitor JTE-013 had no effect. Last, the role of S1P3 was further confirmed in regulation of S1P-induced endothelial proliferation, migration and tube formation via up-regulation and activation of VEGFR2. Together, these findings argue that HDL promotes angiogenesis via S1P3-dependent up-regulation and activation of VEGFR2 and also suggest that the S1P-S1P3-VEGFR2 signaling cascades as a novel target for HDL-modulating therapy implicated in vascular remodeling and functional recovery in atherosclerotic diseases such as myocardial infarction and ischemic stroke.

Flavopiridol enhances ABT-199 sensitivity in unfavourable-risk multiple myeloma cells in vitro and in vivo

Background:

The BCL-2-specific BH3-mimetic ABT-199 (venetoclax) has been reported to be principally active against favourable-risk multiple myeloma (MM) cells, prompting efforts to extend its activity to include more resistant, higher-risk MM subsets.

Methods:

Effects of the CDK9 inhibitor flavopiridol (FP; alvocidib) on responses to ABT-199 were examined in MM cells. Cell death and protein expression were evaluated by western blot and immunofluorescence. Xenograft models were used to study combination effects in vivo.

Results:

FP synergistically increased ABT-199 lethality in both ABT-199-sensitive and insensitive MM cells. FP blocked CDK9 activation/positive transcription elongation factor B phosphorylation, downregulated MCL-1, increased BCL-2/MCL-1 ratios, and upregulated BIM. MCL-1 ectopic expression or knockdown in MM cells significantly diminished or increased ABT-199 sensitivity, respectively. CDK9 knockdown triggered MCL-1 downregulation and increased ABT-199 activity, whereas BIM knockdown significantly reduced FP/ABT-199 lethality. FP also enhanced ABT-199 lethality in unfavourable prognosis primary MM cells. HS-5 cell co-culture failed to protect MM cells from the FP/ABT-199 regimen, suggesting circumvention of microenvironmental signals. Finally, FP/ABT-199 significantly increased survival in systemic xenograft and immune-competent MM models while exhibiting minimal toxicity.

Conclusions:

These findings argue that CDK9 inhibitors, for example, FP may increase the antimyeloma activity of ABT-199, including in unfavourable-risk MM minimally responsive to ABT-199 alone.

Positive transcription elongation factor b (P-TEFb) is a therapeutic target in human multiple myeloma

The role of the positive RNA Pol II regulator, P-TEFb (positive transcription elongation factor b), in maintenance of the anti-apoptotic protein Mcl-1 and bortezomib (btz) resistance was investigated in human multiple myeloma (MM) cells. Mcl-1 was up-regulated in all MM lines tested, including bortezomib-resistant lines, human MM xenograft mouse models, and primary CD138⁺ MM cells. Mcl-1 over-expression significantly reduced bortezomib lethality, indicating a functional role for Mcl-1 in bortezomib resistance. MM cell lines, primary MM specimens, and murine xenografts exhibited constitutive P-TEFb activation, manifested by high CTD (carboxy-terminal domain) S2 phosphorylation, associated with a) P-TEFb subunit up-regulation i.e., CDK9 (42 and 55 kDa isoforms) and cyclin T1; and b) marked CDK9 (42 kDa) T186 phosphorylation. In marked contrast, normal hematopoietic cells failed to exhibit up-regulation of p-CTD, CDK9, cyclin T1, or Mcl-1. CDK9 or cyclin T1 shRNA knock-down dramatically inhibited CTD S2 phosphorylation and down-regulated Mcl-1. Moreover, CRISPR-Cas CDK9 knock-out triggered apoptosis in MM cells and dramatically diminished cell growth. Pan-CDK e.g., dinaciclib or alvocidib and selective CDK9 inhibitors (CDK9i) recapitulated the effects of genetic P-TEFb disruption. CDK9 shRNA or CDK9 inhibitors significantly potentiated the susceptibility of MM cells, including bortezomib-resistant cells, to proteasome inhibitors. Analogously, CDK9 or cyclin T1 knock-down or CDK9 inhibitors markedly increased BH3-mimetic lethality in bortezomib-resistant cells. Finally, pan-CDK inhibition reduced human drug-naïve or bortezomib-resistant CD138⁺ cells and restored bone marrow architecture in vivo. Collectively, these findings implicate constitutive P-TEFb activation in high Mcl-1 maintenance in MM, and validate targeting the P-TEFb complex to circumvent bortezomib-resistance.

Identification of the histone lysine demethylase KDM4A/JMJD2A as a novel epigenetic target in M1 macrophage polarization induced by oxidized LDL. Oncotarget. 2017;8:114442-114456. [PMID: 29383092 DOI: 10.18632/oncotarget.17748] [Cited by in Crossref: 18] Oxidized low density lipoprotein (oxLDL) induces macrophage activation, an event essential for atherosclerosis. Emerging evidence supports that epigenetic regulation plays important roles in macrophage activation and function. However, it remains unclear which epigenetic modulator is responsible for oxLDL-induced macrophage activation. Here, we identify for the first time KDM4A (JMJD2A) as an epigenetic modifying enzyme that controls oxLDL-induced pro-inflammatory M1 polarization of macrophages. OxLDL triggered M1 polarization of murine and human macrophages, characterized by expression of iNOS and robust production of inflammatory cytokines (e.g., TNF-α, MCP-1, IL-1β). In contrast, protein level of the M2 marker Arg1 was clearly decreased after treated with oxLDL. Notably, exposure to oxLDL resulted in markedly increased expression of KDM4A in macrophages. Functionally, shRNA knockdown of KDM4A significantly impaired M1 polarization and expression of inflammatory cytokines induced by oxLDL, accompanied by increased expression of Arg1 and VEGF. However, inhibition of KDM4A by shRNA or the pan-selective KDM inhibitor JIB-04 did not affect oxLDL-mediated activation of the NF-κB and hypoxia inducible factor (HIF) pathways, and vice versa. In addition, JIB-04 induced apoptosis of macrophages in a dose-dependent manner, an event attenuated by oxLDL. Together, these findings argue that KDM4A might represent a novel epigenetic modulator that acts to direct oxLDL-induced M1 polarization of macrophages, while its up-regulation is independent of NF-κB and HIF activation, two signals critical for pro-inflammatory activation of macrophages. They also suggest that KDM4A might serve as a potential target for epigenetic therapy in prevention and treatment of inflammatory diseases such as atherosclerosis

Oxidized low density lipoprotein (oxLDL) induces macrophage activation, an event essential for atherosclerosis. Emerging evidence supports that epigenetic regulation plays important roles in macrophage activation and function. However, it remains unclear which epigenetic modulator is responsible for oxLDL-induced macrophage activation. Here, we identify for the first time KDM4A (JMJD2A) as an epigenetic modifying enzyme that controls oxLDL-induced pro-inflammatory M1 polarization of macrophages. OxLDL triggered M1 polarization of murine and human macrophages, characterized by expression of iNOS and robust production of inflammatory cytokines (e.g., TNF-α, MCP-1, IL-1β). In contrast, protein level of the M2 marker Arg1 was clearly decreased after treated with oxLDL. Notably, exposure to oxLDL resulted in markedly increased expression of KDM4A in macrophages. Functionally, shRNA knockdown of KDM4A significantly impaired M1 polarization and expression of inflammatory cytokines induced by oxLDL, accompanied by increased expression of Arg1 and VEGF. However, inhibition of KDM4A by shRNA or the pan-selective KDM inhibitor JIB-04 did not affect oxLDL-mediated activation of the NF-κB and hypoxia inducible factor (HIF) pathways, and vice versa. In addition, JIB-04 induced apoptosis of macrophages in a dose-dependent manner, an event attenuated by oxLDL. Together, these findings argue that KDM4A might represent a novel epigenetic modulator that acts to direct oxLDL-induced M1 polarization of macrophages, while its up-regulation is independent of NF-κB and HIF activation, two signals critical for pro-inflammatory activation of macrophages. They also suggest that KDM4A might serve as a potential target for epigenetic therapy in prevention and treatment of inflammatory diseases such as atherosclerosis.

Treatment of acquired drug resistance in multiple myeloma by combination therapy with XPO1 and topoisomerase II inhibitors

BACKGROUND

Acquired drug resistance is the greatest obstacle to the successful treatment of multiple myeloma (MM). Despite recent advanced treatment options such as liposomal formulations, proteasome inhibitors, immunomodulatory drugs, myeloma-targeted antibodies, and histone deacetylase inhibitors, MM is still considered an incurable disease.

METHODS

We investigated whether the clinical exportin 1 (XPO1) inhibitor selinexor (KPT-330), when combined with pegylated liposomal doxorubicin (PLD) or doxorubicin hydrochloride, could overcome acquired drug resistance in multidrug-resistant human MM xenograft tumors, four different multidrug-resistant MM cell lines, or ex vivo MM biopsies from relapsed/refractory patients. Mechanistic studies were performed to assess co-localization of topoisomerase II alpha (TOP2A), DNA damage, and siRNA knockdown of drug targets.

RESULTS

Selinexor was found to restore sensitivity of multidrug-resistant 8226B25, 8226Dox6, 8226Dox40, and U266PSR human MM cells to doxorubicin to levels found in parental myeloma cell lines. NOD/SCID-γ mice challenged with drug-resistant or parental U266 human MM and treated with selinexor/PLD had significantly decreased tumor growth and increased survival with minimal toxicity. Selinexor/doxorubicin treatment selectively induced apoptosis in CD138/light-chain-positive MM cells without affecting non-myeloma cells in ex vivo-treated bone marrow aspirates from newly diagnosed or relapsed/refractory MM patients. Selinexor inhibited XPO1-TOP2A protein complexes (proximity ligation assay), preventing nuclear export of TOP2A in both parental and multidrug-resistant MM cell lines. Selinexor/doxorubicin treatment significantly increased DNA damage (comet assay/γ-H2AX) in both parental and drug-resistant MM cells. TOP2A knockdown reversed both the anti-tumor effect and significantly reduced DNA damage induced by selinexor/doxorubicin treatment.

CONCLUSIONS

The combination of an XPO1 inhibitor and liposomal doxorubicin was highly effective against acquired drug resistance in in vitro MM models, in in vivo xenograft studies, and in ex vivo samples obtained from patients with relapsed/refractory myeloma. This drug combination synergistically induced TOP2A-mediated DNA damage and subsequent apoptosis. In addition, based on our preclinical data, we have initiated a phase I/II study with the XPO1 inhibitor selinexor and PLD (ClinicalTrials.gov NCT02186834). Initial results from both preclinical and clinical trials have shown significant promise for this drug combination for the treatment of MM.

LDL suppresses angiogenesis through disruption of the HIF pathway via NF-κB inhibition which is reversed by the proteasome inhibitor BSc2118

Since disturbance of angiogenesis predisposes to ischemic injuries, attempts to promote angiogenesis have been made to improve clinical outcomes of patients with many ischemic disorders. While hypoxia inducible factors (HIFs) stimulate vascular remodeling and angiogenesis, hyperlipidemia impairs angiogenesis in response to various pro-angiogenic factors. However, it remains uncertain how HIFs regulate angiogenesis under hyperlipidemia. Here, we report that exposure to low-density lipoprotein (LDL) suppressed in vitro angiogenesis of human brain microvascular endothelial cells. Whereas LDL exposure diminished expression of HIF-1α and HIF-2α induced by hypoxia, it inhibited DMOG- and TNFα-induced HIF-1α and HIF-2α expression in normoxia. Notably, in both hypoxia and normoxia, LDL markedly reduced expression of HIF-1β, a constitutively stable HIF subunit, an event associated with NF-κB inactivation. Moreover, knockdown of HIF-1β down-regulated HIF-1α and HIF-2α expression, in association with increased HIF-1α hydroxylation and 20S proteasome activity after LDL exposure. Significantly, the proteasome inhibitor BSc2118 prevented angiogenesis attenuation by LDL through restoring expression of HIFs. Together, these findings argue that HIF-1β might act as a novel cross-link between the HIF and NF-κB pathways in suppression of angiogenesis by LDL, while proteasome inhibitors might promote angiogenesis by reactivating this signaling cascade under hyperlipidemia.

Nonlinear response surface in the study of interaction analysis of three combination drugs

Few articles have been written on analyzing three-way interactions between drugs. It may seem to be quite straightforward to extend a statistical method from two-drugs to three-drugs. However, there may exist more complex nonlinear response surface of the interaction index (II) with more complex local synergy and/or local antagonism interspersed in different regions of drug combinations in a three-drug study, compared in a two-drug study. In addition, it is not possible to obtain a four-dimensional (4D) response surface plot for a three-drug study. We propose an analysis procedure to construct the dose combination regions of interest (say, the synergistic areas with II≤0.9). First, use the model robust regression method (MRR), a semiparametric method, to fit the entire response surface of the II, which allows to fit a complex response surface with local synergy/antagonism. Second, we run a modified genetic algorithm (MGA), a stochastic optimization method, many times with different random seeds, to allow to collect as many feasible points as possible that satisfy the estimated values of II≤0.9. Last, all these feasible points are used to construct the approximate dose regions of interest in a 3D. A case study with three anti-cancer drugs in an in vitro experiment is employed to illustrate how to find the dose regions of interest.

The NAE inhibitor pevonedistat interacts with the HDAC inhibitor belinostat to target AML cells by disrupting the DDR

Two classes of novel agents, NEDD8-activating enzyme (NAE) and histone deacetylase (HDAC) inhibitors, have shown single-agent activity in acute myelogenous leukemia (AML)/myelodysplastic syndrome (MDS). Here we examined mechanisms underlying interactions between the NAE inhibitor pevonedistat (MLN4924) and the approved HDAC inhibitor belinostat in AML/MDS cells. MLN4924/belinostat coadministration synergistically induced AML cell apoptosis with or without p53 deficiency or FLT3-internal tandem duplication (ITD), whereas p53 short hairpin RNA (shRNA) knockdown or enforced FLT3-ITD expression significantly sensitized cells to the regimen. MLN4924 blocked belinostat-induced antiapoptotic gene expression through nuclear factor-κB inactivation. Each agent upregulated Bim, and Bim knockdown significantly attenuated apoptosis. Microarrays revealed distinct DNA damage response (DDR) genetic profiles between individual vs combined MLN4924/belinostat exposure. Whereas belinostat abrogated the MLN4924-activated intra-S checkpoint through Chk1 and Wee1 inhibition/downregulation, cotreatment downregulated multiple homologous recombination and nonhomologous end-joining repair proteins, triggering robust double-stranded breaks, chromatin pulverization, and apoptosis. Consistently, Chk1 or Wee1 shRNA knockdown significantly sensitized AML cells to MLN4924. MLN4924/belinostat displayed activity against primary AML or MDS cells, including those carrying next-generation sequencing-defined poor-prognostic cancer hotspot mutations, and CD34(+)/CD38(-)/CD123(+) populations, but not normal CD34(+) progenitors. Finally, combined treatment markedly reduced tumor burden and significantly prolonged animal survival (P < .0001) in AML xenograft models with negligible toxicity, accompanied by pharmacodynamic effects observed in vitro. Collectively, these findings argue that MLN4924 and belinostat interact synergistically by reciprocally disabling the DDR in AML/MDS cells. This strategy warrants further consideration in AML/MDS, particularly in disease with unfavorable genetic aberrations.

BCL2L11/Bim as a dual-agent regulating autophagy and apoptosis in drug resistance

A variety of anticancer agents employed in standard chemotherapy or novel targeted therapy induce autophagy. A cytoprotective autophagic response often counteracts apoptosis triggered by such agents, potentially contributing to acquired drug-resistance. It is recognized that autophagy and apoptosis share molecular regulatory mechanisms primarily governed by multidomain anti-apoptotic members (e.g., BCL2/Bcl(-)2 and BCL2L1/Bcl(-)xL) of the BCL2 family. However, the role of pro-apoptotic BH3-only proteins (e.g.,, BCL2L11/Bim), another class of BCL2 family proteins that critically determine therapeutic responses, in autophagy regulation remains largely unexplored, particularly with respect to mechanisms of acquired drug resistance.

Combination Therapy of Selinexor with Bortezomib or Carfilzomib Overcomes Drug Resistance to Proteasome Inhibitors (PI) in Human Multiple Myeloma

Purpose: Drug resistance is the greatest obstacle to the successful treatment of multiple myeloma (MM). We investigated whether the clinical XPO1 inhibitor selinexor (KPT-330), when combined with bortezomib or carfilzomib, could overcome proteasome inhibitor (PI) resistance in myeloma.

Experimental Design: PI-resistant human MM cell lines 8226-B25 and U266-PSR were treated with the XPO1 inhibitors selinexor or KOS-2464 in combination with bortezomib or carfilzomib and assayed for apoptosis and viability. Mice challenged with PI-resistant human MM cells (U266-PSR) were treated with selinexor +/- bortezomib. CD138+/light-chain+ MM cells from PI-refractory MM patients were treated with selinexor +/- bortezomib or selinexor +/- carfilzomib and assayed for apoptosis. All experiments were compared to the standard of care, bortezomib therapy. IkBα-protein was assayed by Western blot and immunofluorescence microscopy and IkBα-NFkB-complex formation by proximity ligation assay. IkBα protein knockdown in human MM cells by siRNA was performed to determine the mechanism of selinexor inhibitor action. Further analysis of selinexor/bortezomib treatment on intra-cellular protein levels and intra-cellular localization was performed by lysine and N-terminal labeling with six-plex tandem mass tags (heavy isotope) and assayed by LC-MS/MS discovery proteomics.

Results: Selinexor in combination with bortezomib or carfilzomib decreased viability and induced apoptosis in PI-resistant MM cells. Resistant MM cell lines were up to 10-fold resistant to single agent bortezomib or carfilzomib when compared to parental cells. The combination of the XPO1 inhibitors selinexor or KOS-2464 sensitized drug resistant cells to bortezomib (P < 0.02) and carfilzomib (P < 0.005) when compared to single agents. Selinexor and bortezomib inhibited PI-resistant MM tumor growth and increased survival with minimal toxicity in NOD/SCID-g mice. Bone marrow mononuclear cells isolated and treated with selinexor or KOS-2464 and bortezomib or carfilzomib from newly diagnosed (n=8), relapsed (n=5), and bortezomib (n=8) and carfilzomib (n=6) refractory MM patient samples were all sensitized by selinexor and KOS-2464 to bortezomib (P < 0.043) and carfilzomib (P < 0.044) as shown by increased apoptosis. Normal, non-myeloma CD138/light-chain double-negative patient cells were not sensitized to apoptosis by XPO1 inhibitors. Immunofluorescence microscopy of IkBα in 8226-B25 PI-resistant cells showed an increase in IkBα after treatment with selinexor/bortezomib as compared with vehicle control or single agent bortezomib or selinexor. Nuclear IκBα was also increased by selinexor treatment. IkBα protein expression was increased by bortezomib (70%) and selinexor (50%) versus control. The selinexor/bortezomib combination increased IkBα protein (212%) as compared to vehicle control or single agent bortezomib or selinexor. Similar results were found in drug-naïve 8226 and U226 cells, as well as PI-resistant 8226-B25 and U225-PSR cells. The increase in nuclear IkBα after selinexor treatment was confirmed by ImageStream flow cytometry.

Selinexor/bortezomib therapy significantly increased IkBα-NFkB-complexes in PI-resistant MM cells. Selinexor in combination with bortezomib increased proximity co-localization of NFkB and IkBα without affecting XPO1 protein expression after 4 hours of drug treatment. Analysis of the number of NFkB-IkBα foci/binding showed that selinexor/bortezomib increased the number of foci in the nucleus versus untreated control or single agent selinexor or bortezomib (P ≤ 0.00077). IkBα knockdown reduced selinexor-induced cytotoxicity in both IM-9 (9.5-fold) and 8226 (12.3 to 25.4-fold) human MM cells. Intracellular protein analysis by heavy isotope labeling and LC-MS/MS showed changes in several signaling pathways including p53, MAPK, VEGF and angiopoietin, IL-1, HMGB1/TLR and APRIL and BAFF as well as those related to NFkB signaling.

Conclusion: Selinexor, when used in combination with bortezomib or carfilzomib has the potential to overcome PI drug resistance in MM.

Disclosures

Kashyap: Pharma: Employment. Landesman:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm: Employment, Equity Ownership. Shacham:Karyopharm: Employment, Equity Ownership.

Next Generation XPO1 Inhibitor KPT-8602 for the Treatment of Drug-Resistant Multiple Myeloma

Purpose

Human multiple myeloma (MM) remains an incurable disease despite relatively effective treatments, including proteasome inhibitors, immunomodulator-based therapies, and high-dose chemotherapy with autologous stem cell rescue. New agents are needed to further improve treatment outcomes. In previous studies, we have shown that inhibitors of the nuclear export receptor XPO1, in combination with bortezomib, carfilzomib, doxorubicin, or melphalan, synergistically induced apoptosis in MM cells in vitro, in vivo and ex vivo without affecting non-myeloma cells. In early clinical trials, the oral, brain penetrating XPO1 inhibitor selinexor showed clear anti-myeloma activity however adverse events have been recorded, including nausea and anorexia. Our purpose was to investigate the use of oral KPT-8602, a novel small-molecule inhibitor of XPO1 with minimal brain penetration, which has been shown to have reduced toxicities in rodents and primates while maintaining potent anti-tumor effects.

Experimental Procedures

To test the efficacy of KPT-8602, we treated human MM cell lines (both parental and drug-resistant) with KPT-8602 ± currently used MM drugs, including bortezomib, carfilzomib, dexamethasone, doxorubicin, lenalidomide, melphalan, topotecan, and VP-16. Human MM cell lines assayed included RPMI-8226 (8226), NCI-H929 (H929), U266, and MM1.S, PI-resistant 8226-B25 and U266-PSR, doxorubicin-resistant 8226-Dox6 and 8226-Dox40, and melphalan-resistant 8226-LR5 and U266-LR6 cell lines. MM cells (2-4x106 cells/mL) were treated for 24 hours with KPT-8602 (300 nM), followed by treatment with one of the listed anti-MM agents for an additional 24 hours. MM cells were then assayed for cell viability (CellTiter-Blue, Promega). In addition, cells were treated with KPT-8602 ± anti-MM agents concurrently for 20 hours and assayed for apoptosis by flow cytometry. In vivo testing was done in NOD/SCID-g mice by intradermal injection of U266 MM cells. Treatment started 2 weeks after tumor challenge with KPT-8602 (10 mg/kg) ± melphalan (1 or 3 mg/kg) 2X/week (Tuesday, Friday) or with KPT-8602 alone 5X weekly (10 mg/kg) (Monday-Friday). A parallel experiment was run using the clinical XPO1 inhibitor KPT-330 (selinexor). Ex vivo testing was performed on MM cells from newly diagnosed/relapsed patient bone marrow aspirates with KPT-8602 ± bortezomib, carfilzomib, dexamethasone, doxorubicin, lenalidomide, melphalan, topotecan, or VP16. CD138+/light-chain+ cells were assayed for apoptosis by flow cytometry.

Results

Viability assay showed that KPT-8602 had low IC50values (~140 nM) as a single agent and functioned synergistically with bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16. (CI values < 1.0). This synergistic effect was less pronounced in myeloma cells when KPT-8602 was used in combination with dexamethasone or lenalidomide. KPT-8602 ± bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16 combination therapy also induced apoptosis in all MM cell lines tested, including drug-resistant cell lines, as shown by caspase 3 cleavage and flow cytometric analyses. NOD/SCID-gamma mouse tumor growth was reduced and survival increased in KPT-8602/melphalan-treated mice when compared to single-agent controls. In addition, mice treated with KPT-8602 5X weekly had significantly reduced tumor growth and increased survival when compared to 2X weekly drug administration. No toxicity was observed in KPT-8602-treated mice as determined by weight loss in both the 2X and 5X groups. In patient bone marrow biopsies, the combination of KPT-8602 ± bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16 was more effective than single agents at inducing apoptosis in CD138+/LC+ MM cells in both newly diagnosed and relapsed/refractory patient samples.

Conclusions

We found that the novel XPO1 inhibitor KPT-8602 sensitizes MM cells to bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16 as shown by apoptosis in parental and drug-resistant cell lines and by cell viability assays. Sensitization was found to be synergistic. In addition, KPT-8602 was effective in treatment of human MM tumors in mice as a single agent or in combination with melphalan and was effective when combined with several MM drugs in MM cell lines and MM patient bone marrow aspirates. KPT-8602 may be a potential candidate for future clinical trials.

Disclosures

Shacham: Karyopharm: Employment, Equity Ownership. Senapedis:Karyopharm Therapeutics, Inc.: Employment, Patents & Royalties.

Anti-tumor activity of the proteasome inhibitor BSc2118 against human multiple myeloma

Introduction of bortezomib, the first generation of proteasome inhibitor, has significantly improved the median overall survival of patients with multiple myeloma (MM). However, the dose-limiting adverse events and acquired drug resistance limit its long-term usage. Here, we report in vitro and in vivo anti-MM activity of the irreversible proteasome inhibitor BSc2118. BSc2118 inhibited the chymotrypsin-like (CT-L) proteasome activity, accompanied by accumulation of ubiquitinated proteins. BSc2118 suppressed tumor cell growth through induction of G2/M phase arrest and induced apoptosis via activation of the apoptotic signaling cascade, in association with up-regulation of p53 and p21. Importantly, BSc2118 was active in vitro against MM cells' acquired bortezomib resistance. Of note, BSc2118 also displayed a novel anti-angiogenesis activity both in vitro and in vivo. Lastly, BSc2118 exhibited a broader safety dose range and higher anti-tumor efficacy in vivo in a human MM xenograft mouse model, compared to bortezomib. Together, these findings indicate the in vitro and in vivo anti-MM activities of BSc2118 through induction of cell cycle arrest and apoptosis, as well as inhibition of tumor angiogenesis. They also suggest that BSc2118 might, at least in vitro, partially overcome acquired bortezomib resistance, likely associated with inhibition of autophagy.

Neurotensin promotes the progression of malignant glioma through NTSR1 and impacts the prognosis of glioma patients

Background

The poor prognosis and minimally successful treatments of malignant glioma indicate a challenge to identify new therapeutic targets which impact glioma progression. Neurotensin (NTS) and its high affinity receptor (NTSR1) overexpression induces neoplastic growth and predicts the poor prognosis in various malignancies. Whether NTS can promote the glioma progression and its prognostic significance for glioma patients remains unclear.

Methods

NTS precursor (ProNTS), NTS and NTSR1 expression levels in glioma were detected by immunobloting Elisa and immunohistochemistry assay. The prognostic analysis was conducted from internet by R2 microarray platform. Glioma cell proliferation was evaluated by CCK8 and BrdU incorporation assay. Wound healing model and Matrigel transwell assay were utilized to test cellular migration and invasion. The orthotopic glioma implantations were established to analyze the role of NTS and NTSR1 in glioma progression in vivo.

Results

Positive correlations were shown between the expression levels of NTS and NTSR1 with the pathological grade of gliomas. The high expression levels of NTS and NTSR1 indicate a worse prognosis in glioma patients. The proliferation and invasiveness of glioma cells could be enhanced by NTS stimulation and impaired by the inhibition of NTSR1. NTS stimulated Erk1/2 phosphorylation in glioma cells, which could be reversed by SR48692 or NTSR1-siRNA. In vivo experiments showed that SR48692 significantly prolonged the survival length of glioma-bearing mice and inhibited glioma cell invasiveness.

Conclusion

NTS promotes the proliferation and invasion of glioma via the activation of NTSR1. High expression levels of NTS and NTSR1 predict a poor prognosis in glioma patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0290-8) contains supplementary material, which is available to authorized users.

Melphalan and XPO1 Inhibitor Combination Therapy for the Treatment of Multiple Myeloma

Introduction

High-dose melphalan chemotherapy with autologous stem cell transplant remains the standard of care for the treatment of multiple myeloma. However, patients eventually develop drug resistance and die from progressive disease despite the introduction of therapies using proteosome inhibitors (PIs) and immunomodulatory drugs (IMIDs). The incurable nature of multiple myeloma clearly demonstrates the need for novel agents and treatments. Here, our aim was to investigate whether the use of XPO1 (exportin 1, CRM1) inhibitors (XPO1i) could sensitize de novo and acquired drug-resistant multiple myeloma cells both in vitro and ex vivo to the alkylating agent melphalan.

Materials and Methods

Human multiple myeloma cell lines NCI-H929, RPMI-8226, U266 and PBMC controls were treated in vitro with the XPO1i KOS-2464 and the orally available Selective Inhibitor of Nuclear Export (SINE) selinexor (KPT-330) or) +/- melphalan. Multiple myeloma cells were grown at high-density conditions (>3-5x106 cells/mL). High-density multiple myeloma cells have been shown to possess de novo drug resistance. Sensitivity of the XPO1i/melphalan-treated NCI-H929 cells was measured by cell viability assay (CellTiter-Blue). Apoptosis in XPO1i/melphalan-treated NCI-H929, RPMI-8226, and U266 cells was assayed using flow cytometry (activated caspase 3). Proximity ligation assays were performed to assess XPO1-p53 binding in the presence of an XPO1i. Western blots of XPO1i-treated myeloma cells were performed for nuclear and total p53. Drug-resistant U266 (PSR) and 8226 (8226/B25) myeloma cell lines were developed by incremental exposure to bortezomib. PSR cells are able to grow in 15 nM bortezomib and the 8226/B25 in 25 nM. These resistant myeloma cells were treated in vitro with XPO1i +/- melphalan. Sensitivity to therapy was measured by apoptosis and cell viability assay. Multiple myeloma cells isolated from patients with newly diagnosed, relapsed, or refractory disease were treated with XPO1i +/- melphalan and CD138+/light chain+ myeloma cells and assayed for apoptosis.

Results

Multiple myeloma cell (NCI-H929) viability was decreased synergistically by XPO1i when used in combination with melphalan, as shown by the calculated combinatorial index (CI) values. We examined sequencing of the drugs and found that concurrent treatment with melphalan (10 µM) and selinexor (300 nM) for 48 hours produced the best results (CI value 0.370, n=6). Sequential treatment (selinexor for 24 hours followed by melphalan for an additional 24 hours) or the reverse sequence had slightly less synergy, with CI values of 0.491 (n=9) and 0.565 (n=3), respectively. Normal PBMC control cells were unaffected by XPO1i/melphalan treatment as shown by viability and apoptotic assays. Proximity ligation assay demonstrated that XPO1i blocks XPO1/p53 binding. Western blot showed that the XPO1i treatment of myeloma cells increased nuclear and total p53. Drug-resistant 8226/B25 myeloma cells but not PSR cells were found to be resistant to melphalan when compared to parental cell lines. Both resistant myeloma cell lines were sensitized by XPO1i to melphalan as shown by apoptosis assay (3- to 10-fold). CD138+/light chain+ myeloma cells derived from newly diagnosed, relapsed, and refractory myeloma patients were also sensitized by XPO1 inhibitors to melphalan as demonstrated by apoptotic assays (e.g. activated caspase 3).

Conclusions

XPO1i synergistically improved the response of de novo and acquired drug-resistant myeloma cells to melphalan in vitro and ex vivo. It is possible that this synergy may be due to an increase of nuclear p53 by XPO1i and the reported activation of p53 by melphalan. Future studies include in vitro experiments using drug-resistant human U266 myeloma cells in NOD-SCID-gamma mice and clinical trials using melphalan in combination with the SINE selinexor. Combination therapies using selinexor and melphalan may significantly improve the treatment of myeloma.

Disclosures

Kauffman: Karyopharm Therapeutics: Employment. Shacham:Karyopharm Therapeutics: Employment.

HDAC Inhibitors Reciprocally Interacts the Wee1 Inhibitor AZD1775 to Abrogate Both the G1/S and G2/M Checkpoints Via Chk1-Related cdc2/Cdk1 Threonine 14 Dephosphorylation in AML Cells

Cell cycle checkpoints play essential roles in the DNA damage response (DDR) which halts cell cycle progression to allow cells to complete DNA replication and repair DNA damage in response to genotoxic insults (e.g., by chemotherapy and ionizing radiation). Wee1 is a dual-specificity protein kinase principally involved in regulation of the G2/M checkpoint that delays mitotic onset by phosphorylating Y15 and deactivating cdc2/Cdk1. AZD1775 is a highly selective small molecule ATP-competitive Wee1 inhibitor currently undergoing clinical evaluation combined with genotoxic agents in solid tumor malignancies (particularly in p53-deficient tumors), based on the concept of mitotic lethality. Recently, Wee1 has been identified as a target in AML, in which AZD1775 potentiates ara-C or mTOR inhibitor lethality. Notably, gene aberrations related to the cell cycle (e.g., 66%) or the DDR (e.g., 41%) are frequent in AML and correlate with poor prognosis (NEJM, 2013). These findings provide a rationale for a novel Wee1-targeting strategy in AML combining AZD1775 with HDAC inhibitors (HDACIs) which also interrupt the DDR and have been granted AML Orphan Drug designation. Here we report that AZD1775 synergistically interacts with HDACIs (e.g., Vorinostat; both Merck via NCI/NIH) in both p53 wild type or mutant AML cell lines, including those carrying poor-prognostic mutations (e.g., FLT3-ITD), NGS-defined patient-derived primary AML specimens, and the CD34+/CD123+/CD38- population enriched for leukemia-initiating progenitors, but spares normal CD34+ hematopoietic cells. Significantly, in marked contrast to Y15 dephosphorylation, AZD1775 triggered pronounced phosphorylation of T14, another critical cdc2/Cdk1 inhibitory site, which might compromise checkpoint-abrogation and thus limit anti-leukemic activity of AZD1775. We determined that T14 phosphorylation most likely stems from compensatory Chk1 activation (e.g., marked phosphorylation of all three critical serine sites, including S296, S317, S345), rather than Myt1 activation, a kinase that phosphorylates T14. Significantly, co-administration of HDACIs substantially diminished Chk1 activation as well as T14 phosphorylation in cells exposed to AZD1775. Consequently, combined AZD1775/HDACI exposure led to dephosphorylation of cdc2/Cdk1 on both Y15 and T14 residues, resulting in full (and “inappropriate”) activation. As a consequence, AZD1775/HDACI co-treatment sharply increased S10 phosphorylation of histone H3 (p-H3), a premature mitotic entry indicator. Flow cytometry analysis revealed that whereas both AZD1775 and HDACIs alone modestly increased the p-H3 mitotic index (MI) at 8 h , co-exposure strikingly increased the p-H3 MI (e.g., 3.4- and 3.7- fold increases for AZD1775/Vorinostat or /SBHA, respectively), consistent with premature mitotic entry at this early interval. Interestingly, AZD1775/HDACI co-treatment for 16 h sharply arrested cells in early S-phase and increased newly replicated DNA incorporating EdU, accompanied by persistent increases in premature mitotic entry (e.g., increased p-H3 MI). Fluorescence microscopy demonstrated robust increases in both p-H3- and EdU-positive cells after 16-h co-exposure to AZD1775 and HDACIs. Furthermore, confocal microscopy of AZD1775/HDACI-treated cells (16 h) revealed markedly aberrant mitosis characterized by multiple mitotic abnormalities e.g., anaphase bridging, mono- or multi-polar spindles, centrosome clustering, etc. in p-H3-positive cells. These events were associated with a pronounced increase in DNA damage, manifested by expression of the double-strand break (DSB) indicator γH2A.X, as well as marked caspase activation and PARP cleavage in both p53-wt and -deficient cells. Similar results (e.g., cdc2/Cdk1 dephosphorylation of both Y15 and T14, γH2A.X expression, and PARP cleavage) were observed in a murine AML xenograft model in association with a significant reduction in tumor burden and prolongation of animal survival. In conclusion, these findings suggest that a novel strategy combining AZD1775 with HDACIs may markedly improve the anti-AML effectiveness of Wee1-targeting therapy, due to abrogation of both the G1/S and G2/M checkpoints through disruption of compensatory Chk1-mediated cdc2/Cdk1 T14 phosphorylation, and that this interaction occurs independently of p53 status.

Disclosures

No relevant conflicts of interest to declare.

Dual targeting of the thioredoxin and glutathione antioxidant systems in malignant B cells: a novel synergistic therapeutic approach

B-cell malignancies are a common type of cancer. One approach to cancer therapy is to either increase oxidative stress or inhibit the stress response systems on which cancer cells rely. In this study, we combined nontoxic concentrations of Auranofin (AUR), an inhibitor of the thioredoxin system, with nontoxic concentrations of buthionine-sulfoximine (BSO), a compound that reduces intracellular glutathione levels, and investigated the effect of this drug combination on multiple pathways critical for malignant B-cell survival. Auranofin interacted synergistically with BSO at low concentrations to trigger death in multiple malignant B-cell lines and primary mantle-cell lymphoma cells. Additionally, there was less toxicity toward normal B cells. Low AUR concentrations inhibited thioredoxin reductase (TrxR) activity, an effect significantly increased by BSO cotreatment. Overexpression of TrxR partially reversed AUR+BSO toxicity. Interestingly, the combination of AUR+BSO inhibited nuclear factor κB (NF-κB) signaling. Moreover, synergistic cell death induced by this regimen was attenuated in cells overexpressing NF-κB proteins, arguing for a functional role for NF-κB inhibition in AUR+BSO-mediated cell death. Together, these findings suggest that AUR+BSO synergistically induces malignant B-cell death, a process mediated by dual inhibition of TrxR and NF-κB, and such an approach warrants further investigation in B-cell malignancies.

A regimen combining the Wee1 inhibitor AZD1775 with HDAC inhibitors targets human acute myeloid leukemia cells harboring various genetic mutations. Leukemia. 2015;29:807-818. [PMID: 25283841 DOI: 10.1038/leu.2014.296] [Cited by in Crossref: 51] AZD1775 targets the cell cycle checkpoint kinase Wee1 and potentiates genotoxic agent cytotoxicity through p53-dependent or -independent mechanisms. Here, we report that AZD1775 interacted synergistically with histone deacetylase inhibitors (HDACIs e.g., Vorinostat), which interrupt the DNA damage response (DDR), to kill p53-wild type or -deficient as well as FLT3-ITD leukemia cells in association with pronounced Wee1 inhibition and diminished cdc2/Cdk1 Y15 phosphorylation. Similarly, Wee1 shRNA knock-down significantly sensitized cells to HDACIs. While AZD1775 induced Chk1 activation, reflected by markedly increased Chk1 S296/S317/S345 phosphorylation leading to inhibitory T14 phosphorylation of cdc2/Cdk1, these compensatory responses were sharply abrogated by HDACIs. This was accompanied by premature mitotic entry, multiple mitotic abnormalities, and accumulation of early S-phase cells displaying increased newly replicated DNA, culminating in robust DNA damage and apoptosis. The regimen was active against patient-derived AML cells harboring either wild type or mutant p53, and various NGS-defined mutations. Primitive CD34+/CD123+/CD38− populations enriched for leukemia-initiating progenitors, but not normal CD34+ hematopoietic cells, were highly susceptible to this regimen. Finally, combining AZD1775 with Vorinostat in AML murine xenografts significantly reduced tumor burden and prolonged animal survival. A strategy combining Wee1 with HDACI inhibition warrants further investigation in AML with poor prognostic genetic aberrations

AZD1775 targets the cell cycle checkpoint kinase Wee1 and potentiates genotoxic agent cytotoxicity through p53-dependent or -independent mechanisms. Here, we report that AZD1775 interacted synergistically with histone deacetylase inhibitors (HDACIs e.g., Vorinostat), which interrupt the DNA damage response (DDR), to kill p53-wild type or -deficient as well as FLT3-ITD leukemia cells in association with pronounced Wee1 inhibition and diminished cdc2/Cdk1 Y15 phosphorylation. Similarly, Wee1 shRNA knock-down significantly sensitized cells to HDACIs. While AZD1775 induced Chk1 activation, reflected by markedly increased Chk1 S296/S317/S345 phosphorylation leading to inhibitory T14 phosphorylation of cdc2/Cdk1, these compensatory responses were sharply abrogated by HDACIs. This was accompanied by premature mitotic entry, multiple mitotic abnormalities, and accumulation of early S-phase cells displaying increased newly replicated DNA, culminating in robust DNA damage and apoptosis. The regimen was active against patient-derived AML cells harboring either wild type or mutant p53, and various NGS-defined mutations. Primitive CD34⁺/CD123⁺/CD38⁻ populations enriched for leukemia-initiating progenitors, but not normal CD34⁺ hematopoietic cells, were highly susceptible to this regimen. Finally, combining AZD1775 with Vorinostat in AML murine xenografts significantly reduced tumor burden and prolonged animal survival. A strategy combining Wee1 with HDACI inhibition warrants further investigation in AML with poor prognostic genetic aberrations.

A Bim-targeting strategy overcomes adaptive bortezomib resistance in myeloma through a novel link between autophagy and apoptosis

Bim contributes to resistance to various standard and novel agents. Here we demonstrate that Bim plays a functional role in bortezomib resistance in multiple myeloma (MM) cells and that targeting Bim by combining histone deacetylase inhibitors (HDACIs) with BH3 mimetics (eg, ABT-737) overcomes bortezomib resistance. BH3-only protein profiling revealed high Bim levels (Bim(hi)) in most MM cell lines and primary CD138(+) MM samples. Whereas short hairpin RNA Bim knockdown conferred bortezomib resistance in Bim(hi) cells, adaptive bortezomib-resistant cells displayed marked Bim downregulation. HDACI upregulated Bim and, when combined with ABT-737, which released Bim from Bcl-2/Bcl-xL, potently killed bortezomib-resistant cells. These events were correlated with Bim-associated autophagy attenuation, whereas Bim knockdown sharply increased autophagy in Bim(hi) cells. In Bim(low) cells, autophagy disruption by chloroquine (CQ) was required for HDACI/ABT-737 to induce Bim expression and lethality. CQ also further enhanced HDACI/ABT-737 lethality in bortezomib-resistant cells. Finally, HDACI failed to diminish autophagy or potentiate ABT-737-induced apoptosis in bim(-/-) mouse embryonic fibroblasts. Thus, Bim deficiency represents a novel mechanism of adaptive bortezomib resistance in MM cells, and Bim-targeting strategies combining HDACIs (which upregulate Bim) and BH3 mimetics (which unleash Bim from antiapoptotic proteins) overcomes such resistance, in part by disabling cytoprotective autophagy.

Inhibition of the MDM2 E3 Ligase induces apoptosis and autophagy in wild-type and mutant p53 models of multiple myeloma, and acts synergistically with ABT-737

Intracellular proteolytic pathways have been validated as rational targets in multiple myeloma with the approval of two proteasome inhibitors in this disease, and with the finding that immunomodulatory agents work through an E3 ubiquitin ligase containing Cereblon. Another E3 ligase that could be a rational target is the murine double minute (MDM) 2 protein, which plays a role in p53 turnover. A novel inhibitor of this complex, MI-63, was found to induce apoptosis in p53 wild-type myeloma models in association with activation of a p53-mediated cell death program. MI-63 overcame adhesion-mediated drug resistance, showed anti-tumor activity in vivo, enhanced the activity of bortezomib and lenalidomide, and also overcame lenalidomide resistance. In mutant p53 models, inhibition of MDM2 with MI-63 also activated apoptosis, albeit at higher concentrations, and this was associated with activation of autophagy. When MI-63 was combined with the BH3 mimetic ABT-737, enhanced activity was seen in both wild-type and mutant p53 models. Finally, this regimen showed efficacy against primary plasma cells from patients with newly diagnosed and relapsed/refractory myeloma. These findings support the translation of novel MDM2 inhibitors both alone, and in combination with other novel agents, to the clinic for patients with multiple myeloma.

Targeting SQSTM1/p62 induces cargo loading failure and converts autophagy to apoptosis via NBK/Bik

In selective autophagy, the adaptor protein SQSTM1/p62 plays a critical role in recognizing/loading cargo (e.g., malfolded proteins) into autophagosomes for lysosomal degradation. Here we report that whereas SQSTM1/p62 levels fluctuated in a time-dependent manner during autophagy, inhibition or knockdown of Cdk9/cyclin T1 transcriptionally downregulated SQSTM1/p62 but did not affect autophagic flux. These interventions, or short hairpin RNA (shRNA) directly targeting SQSTM1/p62, resulted in cargo loading failure and inefficient autophagy, phenomena recently described for Huntington's disease neurons. These events led to the accumulation of the BH3-only protein NBK/Bik on endoplasmic reticulum (ER) membranes, most likely by blocking loading and autophagic degradation of NBK/Bik, culminating in apoptosis. Whereas NBK/Bik upregulation was further enhanced by disruption of distal autophagic events (e.g., autophagosome maturation) by chloroquine (CQ) or Lamp2 shRNA, it was substantially diminished by inhibition of autophagy initiation (e.g., genetically by shRNA targeting Ulk1, beclin-1, or Atg5 or pharmacologically by 3-methyladenine [3-MA] or spautin-1), arguing that NBK/Bik accumulation stems from inefficient autophagy. Finally, NBK/Bik knockdown markedly attenuated apoptosis in vitro and in vivo. Together, these findings identify novel cross talk between autophagy and apoptosis, wherein targeting SQSTM1/p62 converts cytoprotective autophagy to an inefficient form due to cargo loading failure, leading to NBK/Bik accumulation, which triggers apoptosis.

Synergism of ursolic acid derivative US597 with 2-deoxy-D-glucose to preferentially induce tumor cell death by dual-targeting of apoptosis and glycolysis

Ursolic acid (UA) is a naturally bioactive product that exhibits potential anticancer effects. The relatively safe and effective molecule intrigued us to explore a way to further improve its anti-cancer activity and tumor-targeting specificity. In the present study, a series of structural modifications of UA was achieved, which resulted in significant increase in growth inhibition on various cancer cell lines with minimal effects on normal cells. The leading molecule US597 (UA-4) caused depolarization of mitochondrial membrane potential, cell arrest in G0/G1 phase and apoptosis/necrosis in a dose-dependent manner. Structural docking suggested that the carbon chains of the modified UA derivatives compete strongly with glucose for binding to glucokinase, the key glycolysis enzyme presumably active in cancer cells. The combination of 2-deoxy-D-glucose (2-DG) and UA-4 induced cell cycle arrest in G2/M phase, promoted caspase-dependent cell death, reduced hexokinase activity, aggravated depletion of intracellular ATP, decreased lactate production and synergistically inhibited cancer cell growth in vitro (HepG2) and in vivo (H22). Collectively, our findings suggest that the structural modification enhances efficacy and selectivity of UA, and the combination of UA-4 with 2-DG produces synergistic inhibition on hepatoma cell proliferation by dual targeting of apoptosis and glycolysis.

Histone deacetylase inhibitor (HDACI) mechanisms of action: emerging insights. Pharmacol Ther. 2014;143:323-336. [PMID: 24769080 DOI: 10.1016/j.pharmthera.2014.04.004] [Cited by in Crossref: 178] Initially regarded as "epigenetic modifiers" acting predominantly through chromatin remodeling via histone acetylation, HDACIs, alternatively referred to as lysine deacetylase or simply deacetylase inhibitors, have since been recognized to exert multiple cytotoxic actions in cancer cells, often through acetylation of non-histone proteins. Some well-recognized mechanisms of HDACI lethality include, in addition to relaxation of DNA and de-repression of gene transcription, interference with chaperone protein function, free radical generation, induction of DNA damage, up-regulation of endogenous inhibitors of cell cycle progression, e.g., p21, and promotion of apoptosis. Intriguingly, this class of agents is relatively selective for transformed cells, at least in pre-clinical studies. In recent years, additional mechanisms of action of these agents have been uncovered. For example, HDACIs interfere with multiple DNA repair processes, as well as disrupt cell cycle checkpoints, critical to the maintenance of genomic integrity in the face of diverse genotoxic insults. Despite their pre-clinical potential, the clinical use of HDACIs remains restricted to certain subsets of T-cell lymphoma. Currently, it appears likely that the ultimate role of these agents will lie in rational combinations, only a few of which have been pursued in the clinic to date. This review focuses on relatively recently identified mechanisms of action of HDACIs, with particular emphasis on those that relate to the DNA damage response (DDR), and discusses synergistic strategies combining HDACIs with several novel targeted agents that disrupt the DDR or antagonize anti-apoptotic proteins that could have implications for the future use of HDACIs in patients with cancer

Initially regarded as "epigenetic modifiers" acting predominantly through chromatin remodeling via histone acetylation, HDACIs, alternatively referred to as lysine deacetylase or simply deacetylase inhibitors, have since been recognized to exert multiple cytotoxic actions in cancer cells, often through acetylation of non-histone proteins. Some well-recognized mechanisms of HDACI lethality include, in addition to relaxation of DNA and de-repression of gene transcription, interference with chaperone protein function, free radical generation, induction of DNA damage, up-regulation of endogenous inhibitors of cell cycle progression, e.g., p21, and promotion of apoptosis. Intriguingly, this class of agents is relatively selective for transformed cells, at least in pre-clinical studies. In recent years, additional mechanisms of action of these agents have been uncovered. For example, HDACIs interfere with multiple DNA repair processes, as well as disrupt cell cycle checkpoints, critical to the maintenance of genomic integrity in the face of diverse genotoxic insults. Despite their pre-clinical potential, the clinical use of HDACIs remains restricted to certain subsets of T-cell lymphoma. Currently, it appears likely that the ultimate role of these agents will lie in rational combinations, only a few of which have been pursued in the clinic to date. This review focuses on relatively recently identified mechanisms of action of HDACIs, with particular emphasis on those that relate to the DNA damage response (DDR), and discusses synergistic strategies combining HDACIs with several novel targeted agents that disrupt the DDR or antagonize anti-apoptotic proteins that could have implications for the future use of HDACIs in patients with cancer.

PARP and CHK inhibitors interact to cause DNA damage and cell death in mammary carcinoma cells

The present studies examined viability and DNA damage levels in mammary carcinoma cells following PARP1 and CHK1 inhibitor drug combination exposure. PARP1 inhibitors [AZD2281 ; ABT888 ; NU1025 ; AG014699] interacted with CHK1 inhibitors [UCN-01 ; AZD7762 ; LY2603618] to kill mammary carcinoma cells. PARP1 and CHK1 inhibitors interacted to increase both single strand and double strand DNA breaks that correlated with increased γH2AX phosphorylation. Treatment of cells with CHK1 inhibitors increased the phosphorylation of CHK1 and ERK1/2. Knock down of ATM suppressed the drug-induced increases in CHK1 and ERK1/2 phosphorylation and enhanced tumor cell killing by PARP1 and CHK1 inhibitors. Expression of dominant negative MEK1 enhanced drug-induced DNA damage whereas expression of activated MEK1 suppressed both the DNA damage response and tumor cell killing. Collectively our data demonstrate that PARP1 and CHK1 inhibitors interact to kill mammary carcinoma cells and that increased DNA damage is a surrogate marker for the response of cells to this drug combination.

Circumvention of Mcl-1-dependent drug resistance by simultaneous Chk1 and MEK1/2 inhibition in human multiple myeloma cells

The anti-apoptotic protein Mcl-1 plays a major role in multiple myeloma (MM) cell survival as well as bortezomib- and microenvironmental forms of drug resistance in this disease. Consequently, there is a critical need for strategies capable of targeting Mcl-1-dependent drug resistance in MM. The present results indicate that a regimen combining Chk1 with MEK1/2 inhibitors effectively kills cells displaying multiple forms of drug resistance stemming from Mcl-1 up-regulation in association with direct transcriptional Mcl-1 down-regulation and indirect disabling of Mcl-1 anti-apoptotic function through Bim up-regulation and increased Bim/Mcl-1 binding. These actions release Bak from Mcl-1, accompanied by Bak/Bax activation. Analogous events were observed in both drug-naïve and acquired bortezomib-resistant MM cells displaying increased Mcl-1 but diminished Bim expression, or cells ectopically expressing Mcl-1. Moreover, concomitant Chk1 and MEK1/2 inhibition blocked Mcl-1 up-regulation induced by IL-6/IGF-1 or co-culture with stromal cells, effectively overcoming microenvironment-related drug resistance. Finally, this regimen down-regulated Mcl-1 and robustly killed primary CD138+ MM cells, but not normal hematopoietic cells. Together, these findings provide novel evidence that this targeted combination strategy could be effective in the setting of multiple forms of Mcl-1-related drug resistance in MM.

Translational research in oncology research & development and its impact on early development in China: report of the 5th Annual Meeting of the US Chinese Anti-Cancer Association (USCACA) at 2013 AACR Annual Meeting

In April 2013, the US Chinese Anti-Cancer Association (USCACA) held its 5th annual meeting in conjunction with the American Association for Cancer Research (AACR) 2013 Annual Meeting in Washington DC. The USCACA executive committee reported activities and programs and highlighted the partnership and collaboration between USCACA and other major organizations. The key initiatives and programs of USCACA included 1) USCACA-TIGM Esophageal Cancer Program that funds translational research of esophageal cancer prevention and treatment at the Xinxiang Medical University in Henan province, China; 2) the USCACA-NFCR-AFCR Scholarship Program, which has supported 10 young outstanding Chinese cancer researchers and will award 4 fellowships at the Guangzhou International Symposium on Oncology in November this year; 3) USCACA-Hengrui Training Program for Early Phase Clinical Research, which has supported the training of a Chinese scholar at two major cancer centers in the US; and 4) USCACA has continued its partnership with the Chinese Journal of Cancer, which has reached significant international impact.

A focus on the preclinical development and clinical status of the histone deacetylase inhibitor, romidepsin (depsipeptide, Istodax(®))

Romidepsin (Istodax(®), depsipeptide, FR901228, FK228, NSC 630176) is a cyclic peptide, broad-spectrum, potent histone deacetylase inhibitor, with activity mainly against class I histone deacetylase enzymes. In this article, we give an overview of the putative modes of action, such as effects on gene expression, cell cycle regulation, apoptosis induction, DNA repair, protein acetylation and induction of autophagy. Romidepsin has mainly been developed as a therapy for hematologic malignancies and is approved by the US FDA for the treatment of cutaneous T-cell lymphomas. This report outlines the laboratory and clinical development of the compound as a single agent that has more recently been evaluated in combination with other anticancer therapeutics, such as proteasome inhibitors.