Synergy between proteasome inhibitors and imatinib mesylate in chronic myeloid leukemia

Targeted disruption of the BCR-ABL fusion gene by Cas9/dual-sgRNA inhibits proliferation and induces apoptosis in chronic myeloid leukemia cells

The BCR-ABL fusion gene, formed by the fusion of the breakpoint cluster region protein ( BCR) and the Abl Oncogene 1, Receptor Tyrosine Kinase ( ABL) genes, encodes the BCR-ABL oncoprotein, which plays a crucial role in leukemogenesis. Current therapies have limited efficacy in patients with chronic myeloid leukemia (CML) because of drug resistance or disease relapse. Identification of novel strategies to treat CML is essential. This study aims to explore the efficiency of novel CRISPR-associated protein 9 (Cas9)/dual-single guide RNA (sgRNA)-mediated disruption of the BCR-ABL fusion gene by targeting BCR and cABL introns. A co-expression vector for Cas9 green fluorescent protein (GFP)/dual-BA-sgRNA targeting BCR and cABL introns is constructed to produce lentivirus to affect BCR-ABL expression in CML cells. The effects of dual-sgRNA virus-mediated disruption of BCR-ABL are analyzed via the use of a genomic sequence and at the protein expression level. Cell proliferation, cell clonogenic ability, and cell apoptosis are assessed after dual sgRNA virus infection, and phosphorylated BCR-ABL and its downstream signaling molecules are detected. These effects are further confirmed in a CML mouse model via tail vein injection of Cas9-GFP/dual-BA-sgRNA virus-infected cells and in primary cells isolated from patients with CML. Cas9-GFP/dual-BA-sgRNA efficiently disrupts BCR-ABL at the genomic sequence and gene expression levels in leukemia cells, leading to blockade of the BCR-ABL tyrosine kinase signaling pathway and disruption of its downstream molecules, followed by cell proliferation inhibition and cell apoptosis induction. This method prolongs the lifespan of CML model mice. Furthermore, the effect is confirmed in primary cells derived from patients with CML.

Interplay between proteasome inhibitors and NF-κB pathway in leukemia and lymphoma: a comprehensive review on challenges ahead of proteasome inhibitors

The current scientific literature has extensively explored the potential role of proteasome inhibitors (PIs) in the NF-κB pathway of leukemia and lymphoma. The ubiquitin-proteasome system (UPS) is a critical component in regulating protein degradation in eukaryotic cells. PIs, such as BTZ, are used to target the 26S proteasome in hematologic malignancies, resulting in the prevention of the degradation of tumor suppressor proteins, the activation of intrinsic mitochondrial-dependent cell death, and the inhibition of the NF-κB signaling pathway. NF-κB is a transcription factor that plays a critical role in the regulation of apoptosis, cell proliferation, differentiation, inflammation, angiogenesis, and tumor migration. Despite the successful use of PIs in various hematologic malignancies, there are limitations such as resistant to these inhibitors. Some reports suggest that PIs can induce NF-κB activation, which increases the survival of malignant cells. This article discusses the various aspects of PIs' effects on the NF-κB pathway and their limitations. Video Abstract.

C-Myc inhibition intensified the anti-leukemic properties of Imatinib in chronic myeloid leukemia cells

BACKGROUND

Due to its remarkable efficacy in producing hematologic, cytogenetic, and molecular remissions, the FDA approved Imatinib as the first-line treatment for newly diagnosed Chronic Myeloid Leukemia (CML) patients. However, in some patients, failure to completely eradicate leukemic cells and the escape of these cells from death will lead to the development of resistance to Imatinib, and many are concerned about the prospects of this Tyrosine Kinase Inhibitor (TKI). It has been documented that the compensatory overexpression of c-Myc is among the most critical mechanisms that promote drug efflux and resistance in CML stem cells.

METHODS

In order to examine the potential of c-Myc inhibition through the use of 10058-F4 to enhance the anti-leukemic properties of Imatinib, we conducted trypan blue and MTT assays. Additionally, we employed flow cytometric analysis and qRT-PCR to assess the effects of this combination on cell cycle progression and apoptosis.

RESULTS

The findings of our study indicate that the combination of 10058-F4 and Imatinib exhibited significantly stronger anti-survival and anti-proliferative effects on CML-derived-K562 cells in comparison to either agent administered alone. It is noteworthy that these results were also validated in the CML-derived NALM-1 cell line. Molecular analysis of this synergistic effect revealed that the inhibition of c-Myc augmented the efficacy of Imatinib by modulating the expression of genes related to cell cycle, apoptosis, autophagy, and proteasome.

CONCLUSIONS

Taken together, the findings of this investigation have demonstrated that the suppression of the c-Myc oncoprotein through the use of 10058-F4 has augmented the effectiveness of Imatinib, suggesting that this amalgamation could offer a fresh perspective on an adjunctive treatment for individuals with CML. Nevertheless, additional scrutiny, encompassing in-vivo examinations and clinical trials, is requisite.

Euchromatic Histone Lysine Methyltransferase 2 Inhibition Enhances Carfilzomib Sensitivity and Overcomes Drug Resistance in Multiple Myeloma Cell Lines

Proteasome inhibitors (PIs) are extensively used for the therapy of multiple myeloma. However, patients continuously relapse or are intrinsically resistant to this class of drugs. In addition, adverse toxic effects such as peripheral neuropathy and cardiotoxicity could arise. Here, to identify compounds that can increase the efficacy of PIs, we performed a functional screening using a library of small-molecule inhibitors covering key signaling pathways. Among the best synthetic lethal interactions, the euchromatic histone-lysine N-methyltransferase 2 (EHMT2) inhibitor UNC0642 displayed a cooperative effect with carfilzomib (CFZ) in numerous multiple myeloma (MM) cell lines, including drug-resistant models. In MM patients, EHMT2 expression correlated to worse overall and progression-free survival. Moreover, EHMT2 levels were significantly increased in bortezomib-resistant patients. We demonstrated that CFZ/UNC0642 combination exhibited a favorable cytotoxicity profile toward peripheral blood mononuclear cells and bone-marrow-derived stromal cells. To exclude off-target effects, we proved that UNC0642 treatment reduces EHMT2-related molecular markers and that an alternative EHMT2 inhibitor recapitulated the synergistic activity with CFZ. Finally, we showed that the combinatorial treatment significantly perturbs autophagy and the DNA damage repair pathways, suggesting a multi-layered mechanism of action. Overall, the present study demonstrates that EHMT2 inhibition could provide a valuable strategy to enhance PI sensitivity and overcome drug resistance in MM patients.

Design, Synthesis, Molecular Docking, and Tumor Resistance Reversal Activity Evaluation of Matrine Derivative with Thiophene Structure

Nasopharyngeal carcinoma (NPC) frequently occurs in Southern China. The main treatments of NPC are chemotherapy and radiotherapy. However, chemo-resistance arises as a big obstacle in treating NPC. Therefore, there is a great need to develop new compounds that could reverse tumor drug resistance. In this study, eight matrine derivatives containing thiophene group were designed and synthesized. Structures of these 8 compounds were characterized by 1H-NMR, 13C-NMR, and high-resolution mass spectrometer (HRMS). The cytotoxicity and preliminary synergistic effects of these 8 compounds were detected against nasopharyngeal carcinoma (NPC) cells and cisplatin-resistant NPC cells (CNE2/CDDP), respectively. Furthermore, the in vivo and in vitro tumor resistance reversal effects of compound 3f were evaluated. Moreover, docking studies were performed in Bclw (2Y6W). The results displayed that compound 3f showed synergistic inhibitory effects with cisplatin against CNE2/CDDP cells proliferation via apoptosis induction. Docking results revealed that compound 3f may exert its effects via inhibiting anti-apoptosis protein Bcl-w.

Suppression of Musashi‑2 by the small compound largazole exerts inhibitory effects on malignant cells

RNA‑binding protein Musashi‑2 (MSI2) serves as a regulator of numerous pivotal biological processes associated with cancer initiation, development and resistance to treatment, and may represent a promising drug target. However, whether MSI2 inhibition is of value in antitumor treatment remains to be determined. The present study demonstrated that MSI2 was upregulated in non‑small cell lung cancer (NSCLC) and was inversely associated with the clinical outcome of the patients. Molecular docking analysis demonstrated that the small compound largazole binds to and may be a potential inhibitor of MSI2. Largazole markedly decreased the protein and mRNA levels of MSI2 and suppressed its downstream mammalian target of rapamycin signaling pathway. Largazole also inhibited the proliferation and induced apoptosis of NSCLC and chronic myeloid leukemia (CML) cells (including bone marrow mononuclear cells harvested from CML patients). These results indicate that MSI2 is an emerging therapeutic target for NSCLC and CML, and the MSI2 inhibitor largazole may hold promise as a treatment for these malignancies.

Combined inhibition of MDM2 and BCR-ABL1 tyrosine kinase targets chronic myeloid leukemia stem/progenitor cells in a murine model

Although highly effective, BCR-ABL1 tyrosine kinase inhibitors do not target chronic myeloid leukemia (CML) stem cells. Most patients relapse upon tyrosine kinase inhibitor therapy cessation. We reported previously that combined BCR-ABL1 and BCL-2 inhibition synergistically targets CML stem/progenitor cells. p53 induces apoptosis mainly by modulating BCL-2 family proteins. Although infrequently mutated in CML, p53 is antagonized by MDM2, which is regulated by BCR-ABL1 signaling. We hypothesized that MDM2 inhibition could sensitize CML cells to tyrosine kinase inhibitors. Using an inducible transgenic Scl-tTa-BCR-ABL1 murine CML model, we found, by RT-PCR and CyTOF proteomics increased p53 signaling in CML bone marrow (BM) cells compared with controls in CD45⁺ and linage-SCA-1⁺C-KIT⁺ populations. CML BM cells were more sensitive to exogenous BH3 peptides than controls. Combined inhibition of BCR-ABL1 with imatinib and MDM2 with DS-5272 increased NOXA level, markedly reduced leukemic linage-SCA-1⁺C-KIT⁺ cells and hematopoiesis, decreased leukemia burden, significantly prolonged the survival of mice engrafted with BM cells from Scl-tTa-BCR-ABL1 mice, and significantly decreased CML stem cell frequency in secondary transplantations. Our results suggest that CML stem/progenitor cells have increased p53 signaling and a propensity for apoptosis. Combined MDM2 and BCR-ABL1 inhibition targets CML stem/progenitor cells and has the potential to improve cure rates for CML.

Ligase IV inhibitor SCR7 enhances gene editing directed by CRISPR-Cas9 and ssODN in human cancer cells

Background

Precise genome editing is essential for both basic and translational research. The recently developed CRISPR/Cas9 system can specifically cleave a designated site of target gene to create a DNA double-strand break, which triggers cellular DNA repair mechanism of either inaccurate non-homologous end joining, or site-specific homologous recombination. Unfortunately, homology-directed repair (HDR) is challenging due to its very low efficiency. Herein, we focused on improving the efficiency of HDR using a combination of CRISPR/Cas9, eGFP, DNA ligase IV inhibitor SCR7, and single-stranded oligodeoxynucleotides (ssODN) in human cancer cells.

Results

When Cas9, gRNA and eGFP were assembled into a co-expression vector, the disruption rate more than doubled following GFP-positive cell sorting in transfected cells compared to those unsorted cells. Using ssODNs as templates, SCR7 treatment increased targeted insertion efficiency threefold in transfected cells compared to those without SCR7 treatment. Moreover, this combinatorial approach greatly improved the efficiency of HDR and targeted gene mutation correction at both the GFP-silent mutation and the β-catenin Ser45 deletion mutation cells.

Conclusion

The data of this study suggests that a combination of co-expression vector, ssODN, and ligase IV inhibitor can markedly improve the CRISPR/Cas9-directed gene editing, which should have significant application in targeted gene editing and genetic disease therapy.

Chibby 1: a new component of β-catenin-signaling in chronic myeloid leukemia

Chibby 1 (CBY1) is a small and evolutionarily conserved protein, which act as β-catenin antagonist. CBY1 is encoded by C22orf2 (22q13.1) Its antagonistic function on β-catenin involves the direct interaction with:

The C-terminal activation domain of β-catenin, which hinders β-catenin binding with Tcf/Lef transcription factors hence repressing β-catenin transcriptional activation.

14-3-3 scaffolding proteins (σ or ξ), which drive CBY1 nuclear export into a stable tripartite complex with β-catenin.

The relative proximity of C22orf2 gene encoding for CBY1 to the BCR breakpoint on chromosome 22q11, whose translocation and rearrangement with the c-ABL is the causative event of chronic myeloid leukemia (CML), suggested that gene haploinsufficiency may play a role in the disease pathogenesis and progression. We found CBY1 down-modulation associated with the BCR-ABL1, promoted by transcriptional mechanisms (promoter hyper-methylation) and post-transcriptional events, addressing the protein towards proteasome-dependent degradation through SUMOylation. CBY1 reduced expression in clonal progenitors and, more importantly, in leukemic stem cells (LSC), is contingent upon the tyrosine kinase (TK) activity of BCR-ABL1 fusion protein. Accordingly, its induction by Imatinib (IM) and second generation TK inhibitors contributes to β-catenin inactivation through multiple events encompassing the activation of endoplasmic reticulum (ER) stress-associated unfolded protein response (UPR) and autophagy, eventually leading to apoptotic death. These findings support the advantage of combined regimens including drugs targeting DNA epigenetics and/or proteasome to eradicate the BCR-ABL1+ hematopoiesis.

Combination of bortezomib and daunorubicin in the induction of apoptosis in T-cell acute lymphoblastic leukemia

Despite advances in the treatment of T‑cell acute lymphoblastic leukemia (T‑ALL), the outcome of T‑ALL treatment remains unsatisfactory, therefore, more effective treatment is urgently required. The present study examined the cytotoxicities of bortezomib in combination with daunorubicin against human Jurkat and Molt‑4 T‑ALL cells and primary T‑ALL cells. Compared with treatment alone, co‑exposure of cells to bortezomib and daunorubicin resulted in a significant increase in cell death in the Jurkat cells, as evidenced by the increased percentage of Annexin V‑positive cells, the formation of apoptotic bodies. In addition, the administration sequence of bortezomib and daunorubicin had an effect on cell viability. Treatment with bortezomib followed by daunorubicin treatment was more effective, compared with treatment with daunorubicin followed by bortezomib. Co-treatment with bortezomib and daunorubicin markedly enhanced the activation of caspase‑3, ‑8 and ‑9, which was reversed by the pan‑caspase inhibitor, Z‑VAD‑FMK. In addition, cotreatment with bortezomib and daunorubicin enhanced the collapse of mitochondrial transmembrane potential and upregulated the proapoptotic protein, B‑cell lymphoma 2 (Bcl‑2)‑interacting mediator of cell death (Bim), but not Bcl‑2 or Bcl‑extra large. Consistent with this, it was demonstrated that cotreatment of bortezomib and daunorubicin efficiently induced apoptosis in primary T‑ALL cells, and cell death was associated with the collapse of mitochondrial transmembrane potential and the upregulation of Bim. Taken together, these findings indicated that the combination of bortezomib and daunorubicin significantly enhanced their apoptosis‑inducing effect in T‑ALL cells, which may warrant further investigation in preclinical and clinical investigations.

Regulation rewiring analysis reveals mutual regulation between STAT1 and miR-155-5p in tumor immunosurveillance in seven major cancers

Transcription factors (TFs) and microRNAs (miRNAs) form a gene regulatory network (GRN) at the transcriptional and post-transcriptional level in living cells. However, this network has not been well characterized, especially in regards to the mutual regulations between TFs and miRNAs in cancers. In this study, we collected those regulations inferred by ChIP-Seq or CLIP-Seq to construct the GRN formed by TFs, miRNAs, and target genes. To increase the reliability of the proposed network and examine the regulation activity of TFs and miRNAs, we further incorporated the mRNA and miRNA expression profiles in seven cancer types using The Cancer Genome Atlas data. We observed that regulation rewiring was prevalent during tumorigenesis and found that the rewired regulatory feedback loops formed by TFs and miRNAs were highly associated with cancer. Interestingly, we identified one regulatory feedback loop between STAT1 and miR-155-5p that is consistently activated in all seven cancer types with its function to regulate tumor-related biological processes. Our results provide insights on the losing equilibrium of the regulatory feedback loop between STAT1 and miR-155-5p influencing tumorigenesis.

Cytoprotection "gone astray": Nrf2 and its role in cancer

Nrf2 has gained great attention with respect to its pivotal role in cell and tissue protection. Primarily defending cells against metabolic, xenobiotic and oxidative stress, Nrf2 is essential for maintaining tissue integrity. Owing to these functions, Nrf2 is regarded as a promising drug target in the chemoprevention of diseases, including cancer. However, much evidence has accumulated that the beneficial role of Nrf2 in cancer prevention essentially depends on the tight control of its activity. In fact, the deregulation of Nrf2 is a critical determinant in oncogenesis and found in many types of cancer. Therefore, amplified Nrf2 activity has profound effects on the phenotype of tumor cells, including radio/chemoresistance, apoptosis protection, invasiveness, antisenescence, autophagy deficiency, and angiogenicity. The deregulation of Nrf2 can result from various epigenetic and genetic alterations directly affecting Nrf2 control or from the complex interplay of Nrf2 with numerous oncogenic signaling pathways. Additionally, alterations of the cellular environment, eg, during inflammation, contribute to Nrf2 deregulation and its persistent activation. Therefore, the status of Nrf2 as anti- or protumorigenic is defined by many different modalities. A better understanding of these modalities is essential for the safe use of Nrf2 as an activation target for chemoprevention on the one hand and as an inhibition target in cancer therapy on the other. The present review mainly addresses the conditions that promote the oncogenic function of Nrf2 and the resulting consequences providing the rationale for using Nrf2 as a target structure in cancer therapy.

Growth arrest specific 2 is up-regulated in chronic myeloid leukemia cells and required for their growth

Although the generation of BCR-ABL is the molecular hallmark of chronic myeloid leukemia (CML), the comprehensive molecular mechanisms of the disease remain unclear yet. Growth arrest specific 2 (GAS2) regulates multiple cellular functions including cell cycle, apoptosis and calpain activities. In the present study, we found GAS2 was up-regulated in CML cells including CD34⁺ progenitor cells compared to their normal counterparts. We utilized RNAi and the expression of dominant negative form of GAS2 (GAS2DN) to target GAS2, which resulted in calpain activity enhancement and growth inhibition of both K562 and MEG-01 cells. Targeting GAS2 also sensitized K562 cells to Imatinib mesylate (IM). GAS2DN suppressed the tumorigenic ability of MEG-01 cells and impaired the tumour growth as well. Moreover, the CD34⁺ cells from CML patients and healthy donors were transduced with control and GAS2DN lentiviral vectors, and the CD34⁺ transduced (YFP⁺) progeny cells (CD34⁺YFP⁺) were plated for colony-forming cell (CFC) assay. The results showed that GAS2DN inhibited the CFC production of CML cells by 57±3% (n = 3), while affected those of normal hematopoietic cells by 31±1% (n = 2). Next, we found the inhibition of CML cells by GAS2DN was dependent on calpain activity but not the degradation of beta-catenin. Lastly, we generated microarray data to identify the differentially expressed genes upon GAS2DN and validated that the expression of HNRPDL, PTK7 and UCHL5 was suppressed by GAS2DN. These 3 genes were up-regulated in CML cells compared to normal control cells and the growth of K562 cells was inhibited upon HNRPDL silence. Taken together, we have demonstrated that GAS2 is up-regulated in CML cells and the inhibition of GAS2 impairs the growth of CML cells, which indicates GAS2 is a novel regulator of CML cells and a potential therapeutic target of this disease.

Cancerous inhibitor of PP2A is targeted by natural compound celastrol for degradation in non-small-cell lung cancer

Celastrol binds CIP2A and enhances CIP2A-CHIP interaction, leading to ubiquitination/degradation of CIP2A and inhibition of lung cancer cells in vitro and in vivo. Celastrol potentiates cisplatin's efficacy by suppressing the CIP2A-Akt pathway, and therefore CIP2A inhibitors may represent novel therapeutics for cancer.

Protein phosphatase 2A: a target for anticancer therapy

Protein phosphatase 2A (PP2A), one of the main serine-threonine phosphatases in mammalian cells, maintains cell homoeostasis by counteracting most of the kinase-driven intracellular signalling pathways. Unrestrained activation of oncogenic kinases together with inhibition of tumour suppressors is often required for development of cancer. PP2A has been shown to be genetically altered or functionally inactivated in many solid cancers and leukaemias, and is therefore a tumour suppressor. For example, the phosphatase activity of PP2A is suppressed in chronic myeloid leukaemia and other malignancies characterised by aberrant activity of oncogenic kinases. Preclinical studies show that pharmacological restoration of PP2A tumour-suppressor activity by PP2A-activating drugs (eg, FTY720) effectively antagonises cancer development and progression. Here, we discuss PP2A as a druggable tumour suppressor in view of the possible introduction of PP2A-activating drugs into anticancer therapeutic protocols.

Bruton's tyrosine kinase: potential target in human multiple myeloma

Bruton's tyrosine kinase (BTK), a Tec family non-receptor tyrosine kinase that is required for B cell development, is critical for the initiation and maintenance of human B-cell malignancies. However, the expression of BTK and the role that BTK plays in the pathogenesis of multiple myeloma (MM) remain seldom reported. In this study we examined the expression and screened for gene mutations of BTK in MM cells. We showed that BTK was elevated and activated in a dexamethasone-resistant cell line and in two out of nine (22.2%) patients' cells. Interestingly, patients with higher BTK expression had a poorer prognosis. In addition, a single nucleotide polymorphism (SNP) at cDNA position 2062 (T2062C) in the BTK gene was recorded in six out of eight (75%) patients and in U266 cells. This SNP in MM cells was not detected in other malignant hematopoietic cells of different lineages. These results suggest that the function of BTK warrants further investigation, and BTK expression might be used as a prognostic indicator for patients with MM.

Gefitinib analogue V1801 induces apoptosis of T790M EGFR-harboring lung cancer cells by up-regulation of the BH-3 only protein Noxa

Treatment of non-small cell lung cancer (NSCLC) with drugs targeting the epidermal growth factor receptor (EGFR), e.g., gefitinib and erlotinib, will eventually fail because of the development of secondary mutations such as T790M in EGFR. Strategies to overcome this resistance are therefore an urgent need. In this study, we synthesized a dozen of novel gefitinib analogues and evaluated their effects on L858R/T790M-EGFR harboring NSCLC cells, and reported that one of these gefitinib mimetics, N-(2-bromo-5-(trifluoromethyl) phenyl)-6-methoxy-7-(3-(piperidin-1-yl)propoxy)quinazolin-4-amine (hereafter, V1801), triggered apoptosis of the NSCLC cells and overcame gefitinib-resistance in mice inoculated with NCI-H1975 cells. Though V1801 only moderately inhibited EGFR kinase activity, it markedly induced the expression of the BH3-only protein Noxa, and Noxa silencing significantly reduced V1801-induced apoptosis of NCI-H1975 cells. It is showed that V1801 interfered with the expression of the transcription factor c-Myc and the extracellular signal regulated kinase (Erk) pathway. V1801 in combination with proteasome inhibitor bortezomib exerted enhanced cytotoxicity in NCI-H1975 cells possibly due to potentiated induction of Noxa expression. These data indicate that gefinitib analogues with weak EGFR inhibitory activity may overcome drug-resistance via activation of BH-3 only pro-apoptotic proteins, and V1801 may have therapeutic potentials for NSCLC.

Identification of an annonaceous acetogenin mimetic, AA005, as an AMPK activator and autophagy inducer in colon cancer cells

Annonaceous acetogenins, a large family of naturally occurring polyketides isolated from various species of the plant genus Annonaceae, have been found to exhibit significant cytotoxicity against a variety of cancer cells. Previous studies showed that these compounds could act on the mitochondria complex-I and block the corresponding electron transport chain and terminate ATP production. However, more details of the mechanisms of action remain ambiguous. In this study we tested the effects of a set of mimetics of annonaceous acetogenin on some cancer cell lines, and report that among them AA005 exhibits the most potent antitumor activity. AA005 depletes ATP, activates AMP-activated protein kinase (AMPK) and inhibits mTOR complex 1 (mTORC1) signal pathway, leading to growth inhibition and autophagy of colon cancer cells. AMPK inhibitors compound C and inosine repress, while AMPK activator AICAR enhances, AA005-caused proliferation suppression and subsequent autophagy of colon cancer cells. AA005 enhances the ATP depletion and AMPK activation caused by 2-deoxyglucose, an inhibitor of mitochondrial respiration and glycolysis. AA005 also inhibits chemotherapeutic agent cisplatin-triggered up-regulation of mTOR and synergizes with this drug in suppression of proliferation and induction of apoptosis of colon cancer cells. These data indicate that AA005 is a new metabolic inhibitor which exhibits therapeutic potentials in colon cancer.

α-bisabolol is an effective proapoptotic agent against BCR-ABL(+) cells in synergism with Imatinib and Nilotinib

We showed that α-bisabolol is active against primary acute leukemia cells, including BCR-ABL⁺ acute lymphoblastic leukemias (ALL). Here we studied the activity of α-bisabolol against BCR-ABL⁺ cells using 3 cell lines (K562, LAMA-84, CML-T1) and 10 primary BCR-ABL⁺ ALL samples. We found that: (a) α-bisabolol was effective in reducing BCR-ABL⁺ cell viabilty at concentrations ranging from 53 to 73 µM; (b) α-bisabolol concentrations in BCR-ABL⁺ cellular compartments were 4- to 12-fold higher than in normal cells, thus indicating a preferential intake in neoplastic cells; (c) α-bisabolol displayed a slight to strong synergism with the Tyrosine Kinase Inhibitors (TKI) imatinib and nilotinib: the combination of α-bisabolol+imatinib allowed a dose reduction of each compound up to 7.2 and 9.4-fold respectively, while the combination of α-bisabolol+nilotinib up to 6.7 and 5-fold respectively; (d) α-bisabolol-induced apoptosis was associated with loss of plasma membrane integrity, irreversible opening of mitochondrial transition pore, disruption of mitochondrial potential, inhibition of oxygen consumption and increase of intracellular reactive oxygen species. These data indicate α-bisabolol as a candidate for treatment of BCR-ABL⁺ leukemias to overcome resistance to TKI alone and to target leukemic cells through BCR-ABL-independent pathways.

Blockade of NFκB activity by Sunitinib increases cell death in Bortezomib-treated endometrial carcinoma cells

Endometrial carcinoma is one of the most common malignancies in the female genital tract, usually treated by surgery and radiotherapy. Chemotherapy is used when endometrial carcinoma is associated with widespread metastasis or when the tumor recurs after radiation therapy. In the present study, we demonstrate that the tyrosine kinase receptor inhibitor Sunitinib reduces cell viability, proliferation, clonogenicity and induces apoptotic cell death in endometrial carcinoma cell lines, which is not due to its action through the most known targets like VEGFR, nor through EGFR as demonstrated in this work. Interestingly, Sunitinib reduces NFκB transcriptional activity either at basal level or activation by EGF or TNF-α. We observed that Sunitinib was able to inhibit the Bortezomib-induced NFκB transcriptional activity which correlates with a decrease of the phosphorylated levels of IKKα and β, p65 and IκBα. We evaluated the nature of the interaction between Sunitinib and Bortezomib by the dose effect method and identified a synergistic effect (combination index < 1). Analogously, silencing of p65 expression by lentiviral-mediated short-hairpin RNA delivery in Bortezomib treated cells leads to a strongly increased sensitivity to Bortezomib apoptotic cell death. Altogether our results suggest that the combination of Sunitinib and Bortezomib could be considered a promising treatment for endometrial carcinoma after failure of surgery and radiation.

The Interface between BCR-ABL-Dependent and -Independent Resistance Signaling Pathways in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a clonal hematopoietic disorder characterized by the presence of the Philadelphia chromosome which resulted from the reciprocal translocation between chromosomes 9 and 22. The pathogenesis of CML involves the constitutive activation of the BCR-ABL tyrosine kinase, which governs malignant disease by activating multiple signal transduction pathways. The BCR-ABL kinase inhibitor, imatinib, is the front-line treatment for CML, but the emergence of imatinib resistance and other tyrosine kinase inhibitors (TKIs) has called attention for additional resistance mechanisms and has led to the search for alternative drug treatments. In this paper, we discuss our current understanding of mechanisms, related or unrelated to BCR-ABL, which have been shown to account for chemoresistance and treatment failure. We focus on the potential role of the influx and efflux transporters, the inhibitor of apoptosis proteins, and transcription factor-mediated signals as feasible molecular targets to overcome the development of TKIs resistance in CML.

Bortezomib has little ex vivo activity in chronic myeloid leukemia: individual tumor response testing comparative study in acute and chronic myeloid leukemia

Aim of the study

Resistance to imatinib is one of the most important issues in treatment of chronic myeloid leukemia (CML) patients. The objective of the study was to analyze the ex vivo drug resistance profile to bortezomib and 22 other antileukemic drugs, including three tyrosine kinase inhibitors (TKIs), in CML in comparison to acute myeloid leukemia (AML).

Material and methods

A total of 82 patients entered the study, including 36 CML and 46 AML adults. Among CML patients, 19 had advanced disease, 16 were resistant to imatinib, and 6 had ABL-kinase domain mutations. The ex vivo drug resistance profile was studied by the MTT assay.

Results

CML cells were more resistant than AML blasts to the following drugs: prednisolone, vincristine, doxorubicin, etoposide, melphalan, cytarabine, fludarabine, thiotepa, 4-HOO-cyclophosphamide, thioguanine, bortezomib, topotecan, and clofarabine. CML cells were 2-fold more sensitive to busulfan than AML cells. CML patients with clinical imatinib resistance had higher ex vivo resistance to vincristine, daunorubicin, etoposide, and busulfan. No significant differences to all tested drugs, including TKIs, were observed between CML patients with non-advanced and advanced disease. CML patients with mutation had higher ex vivo resistance to vincristine, idarubicin, thiotepa, and busulfan.

Conclusions

CML cells are ex vivo more resistant to most drugs than acute myeloid leukemia blasts. Busulfan is more active in CML than AML cells. In comparison to AML cells, bortezomib has little ex vivo activity in CML cells. No differences between CML subgroups in sensitivity to 3 tested TKIs were detected.

Analysis of altered proteins related to blast crisis in chronic myeloid leukemia by proteomic study

INTRODUCTION

Chromic myeloid leukemia (CML) blast crisis (BC) and imatinib (IM) resistance is a significant barrier to the effective treatment of the disease.

METHODS

Expression profiles of differential proteins were identified, and new biomarkers or pathways related to BC in CML were screened through proteomic analysis. Total proteins from primary bone marrow cells of CML patients in chronic phase (CP) and BC were separated via two-dimensional (2D) polyacrylamide gel electrophoresis and then analyzed by imagemaster 5.0 software to detect differential protein spots which were already identified by mass spectrometry. Based on the variation of the whole expression profile, some key proteins were picked out for Western blot to confirm the accuracy of proteomics data. Moreover, related signal pathways involving those proteins were investigated.

RESULTS

The result indicated that thirteen protein points between CML-CP and CML-BC were successfully determined. Results from Western blot of RhoA, hnRNPK, ANXA1, PSMB4, and LTA4H were similar to those from 2D polyacrylamide gel electrophoresis. Most of those proteins were involved in the proteosome pathway and the small G-protein pathway.

CONCLUSION

A group of proteins associated with BC can be obtained and the result of this study might provide clues for further research.

From an old remedy to a magic bullet: molecular mechanisms underlying the therapeutic effects of arsenic in fighting leukemia

Arsenic had been used in treating malignancies from the 18th to mid-20th century. In the past 3 decades, arsenic was revived and shown to be able to induce complete remission and to achieve, when combined with all-trans retinoic acid and chemotherapy, a 5-year overall survival of 90% in patients with acute promyelocytic leukemia driven by the t(15;17) translocation-generated promyelocytic leukemia-retinoic acid receptor α (PML-RARα) fusion. Molecularly, arsenic binds thiol residues and induces the formation of reactive oxygen species, thus affecting numerous signaling pathways. Interestingly, arsenic directly binds the C3HC4 zinc finger motif in the RBCC domain of PML and PML-RARα, induces their homodimerization and multimerization, and enhances their interaction with the SUMO E2 conjugase Ubc9, facilitating subsequent sumoylation/ubiquitination and proteasomal degradation. Arsenic-caused intermolecular disulfide formation in PML also contributes to PML-multimerization. All-trans retinoic acid, which targets PML-RARα for degradation through its RARα moiety, synergizes with arsenic in eliminating leukemia-initiating cells. Arsenic perturbs a number of proteins involved in other hematologic malignancies, including chronic myeloid leukemia and adult T-cell leukemia/lymphoma, whereby it may bring new therapeutic benefits. The successful revival of arsenic in acute promyelocytic leukemia, together with modern mechanistic studies, has thus allowed a new paradigm to emerge in translational medicine.

Overexpression and small molecule-triggered downregulation of CIP2A in lung cancer

Background

Lung cancer is the leading cause of cancer deaths worldwide, with a five-year overall survival rate of only 15%. Cancerous inhibitor of PP2A (CIP2A) is a human oncoprotein inhibiting PP2A in many human malignancies. However, whether CIP2A can be a new drug target for lung cancer is largely unclear.

Methodology/Principal Findings

Normal and malignant lung tissues were derived from 60 lung cancer patients from southern China. RT-PCR, Western blotting and immunohistochemistry were used to evaluate the expression of CIP2A. We found that among the 60 patients, CIP2A was undetectable or very low in paratumor normal tissues, but was dramatically elevated in tumor samples in 38 (63.3%) patients. CIP2A overexpression was associated with cigarette smoking. Silencing CIP2A by siRNA inhibited the proliferation and clonogenic activity of lung cancer cells. Intriguingly, we found a natural compound, rabdocoetsin B which is extracted from a Traditional Chinese Medicinal herb Rabdosia coetsa, could induce down-regulation of CIP2A and inactivation of Akt pathway, and inhibit proliferation and induce apoptosis in a variety of lung cancer cells.

Conclusions/Significance

Our findings strongly indicate that CIP2A could be an effective target for lung cancer drug development, and the therapeutic potentials of CIP2A-targeting agents warrant further investigation.

Resveratrol protects leukemic cells against cytotoxicity induced by proteasome inhibitors via induction of FOXO1 and p27Kip1

BACKGROUND

It was reported recently that resveratrol could sensitize a number of cancer cells to the antitumoral effects of some conventional chemotherapy drugs. The current study was designed to investigate whether resveratrol could sensitize leukemic cells to proteasome inhibitors.

METHODS

Leukemic cells were treated with MG132 alone or in combination with resveratrol. Cell viability was investigated using MTT assay, and induction of apoptosis and cell cycle distribution was measured using flow cytometry. Western blot and real-time RT-PCR were used to investigate the expression of FOXO1 and p27Kip1. CHIP was performed to investigate the binding of FOXO1 to the p27 Kip1 promoter.

RESULTS

Resveratrol strongly reduced cytotoxic activities of proteasome inhibitors against leukemic cells. MG132 in combination with resveratrol caused cell cycle blockade at G1/S transition via p27Kip1 accumulation. Knockdown of p27Kip1 using siRNA dramatically attenuated the protective effects of resveratrol on cytotoxic actions of proteasome inhibitors against leukemic cells. Resveratrol induced FOXO1 expression at the transcriptional level, while MG132 increased nuclear distribution of FOXO1. MG132 in combination with resveratrol caused synergistic induction of p27Kip1 through increased recruitment of FOXO1 on the p27Kip1 promoter.

CONCLUSIONS

Resveratrol may have the potential to negate the cytotoxic effects of proteasome inhibitors via regulation of FOXO1 transcriptional activity and accumulation of p27Kip1.

The Ph-positive and Ph-negative myeloproliferative neoplasms: some topical pre-clinical and clinical issues

This review focuses on topical issues in the biology and treatment of the myeloproliferative neoplasms (MPNs). Studies in transgenic mice suggest that BCR-ABL1 reduces the fraction of self-renewing 'leukemic' stem cells in the bone marrow but that some of these cells survive treatment with imatinib. This also seems to operate in humans. Data from models also strongly support the notion that JAK2(V617F) can initiate and sustain MPNs in mice; relevance to disease in humans is less clear. These data also support the hypothesis that level of JAK2(V617F) expression influences the MPN phenotype: higher levels favor erythrocytosis whereas lower levels favor thrombocytosis. Although TET2-mutations were thought to precede JAK2(V617F) in some persons with MPNs, it now appears that TET2 mutations may occur after JAK2(V617F). Further understanding of signal-transduction pathways activated in chronic myeloid leukemia suggests various possible targets for new therapies including the WNT/beta catenin, notch and hedgehog pathways. Finally, the clinical role of the new JAK2- and BCR-ABL1-inhibitors is considered. Much further progress is likely in several of these areas soon.

An investigation of reversal of imatinib resistance in the Bcr-Abl positive imatinib-resistant cell line K562r by dasatinib, nilotinib, rapamycin and bortezomib

INTRODUCTION

We investigated the second-generation tyrosine kinase inhibitors, dasatinib and nilotinib, for their potential to overcome resistance in the imatinib-resistant K562 cell line, and evaluated whether rapamycin, an mammalian target of rapamycin (mTOR) inhibitor, and bortezomib, a proteasome inhibitor, could increase imatinib sensitivity in resistant cell lines.

METHODS

Cell lines, including K562 (chronic myeloid leukaemia in blast crisis) and K562r (imatinib-resistant K562), were exposed to dasatinib, nilotinib, rapamycin, bortezomib, and rapamycin plus imatinib. Cell proliferation was measured by 3-[4, 5-dimethylthia-zol-2-yl]-2, 5-diphenyl tetrazolium bromide (MTT) assay and mTOR signaling pathways were assessed by Western blotting.

RESULTS

Dasatinib, nilotinib, and bortezomib inhibited proliferation of K562 and K562r cell lines at nm concentrations. Resistance of K562r due to duplication of autophosphorylation of wild-type Bcr-Abl was not overcome by dasatinib and nilotinib, but was sensitive to bortezomib. Rapamycin partially inhibited proliferation of K562 and K562r cell lines. Rapamycin plus imatinib did not have a more inhibitory effect on the proliferation of K562 and K562r cell lines.

CONCLUSION

K562r due to duplication of autophosphorylation of wild-type Bcr-Abl induced by imatinib was still partially resistant to dasatinib and nilotinib, but this was overcome by incremental dosing. Rapamycin did not enhance imatinib sensitivity. The blockade of the ubiquitin-proteasome pathway could be effective in overcoming resistance in the K562r imatinib-resistant cell line.

Targeting chronic myeloid leukemia stem cells

Chronic myeloid leukemia (CML) arises as a consequence of a chromosomal translocation giving rise to the Philadelphia chromosome and Bcr-Abl oncogene. CML is a clonal disease of stem cell origin and an excellent example of a malignancy in which tumor-initiating cells may hold the key to disease eradication. The known molecular basis of CML has enabled the development of Abl-specific tyrosine kinase inhibitors, such as imatinib mesylate. However, the success of tyrosine kinase inhibitors, as rationally designed first-line therapies, has been tempered by problems of disease persistence and resistance. Residual disease has been shown to be enriched within the stem cell compartment and to persist at stable levels for up to 5 years of complete cytogenetic response. This finding has led to further searches for novel strategies aimed at eliminating these cells; such strategies may be essential in achieving cure. The most significant recent findings are discussed in this review.

Why doesn't imatinib cure chronic myeloid leukemia?

Imatinib mesylate has transformed the treatment for chronic myeloid leukemia (CML). The vast majority of patients obtain hematologic remission, with a low probability of progression of disease. Yet imatinib rarely cures CML, and current recommendations dictate lifelong treatment with imatinib. In this review we analyze the biology behind the failure of imatinib to fully eradicate CML. We review evidence that indicates that the leukemic stem cell for CML is inherently resistant to imatinib, and that imatinib treatment itself may enhance this resistance.