CaMKII γ, a critical regulator of CML stem/progenitor cells, is a target of the natural product berbamine

Homoharringtonine targets Smad3 and TGF-β pathway to inhibit the proliferation of acute myeloid leukemia cells

Homoharringtonine (HHT) has long and widely been used in China for the treatment of acute myeloid leukemia (AML), the clinical therapeutic effect is significant but the working mechanism is poorly understood. The purpose of this study is to screen the possible target for HHT with virtual screening and verify the findings by cell experiments. Software including Autodock, Python, and MGL tools were used, with HHT being the ligand and proteins from PI3K-Akt pathway, Jak-stat pathway, TGF-β pathway and NK-κB pathway as the receptors. Human AML cell lines including U937, KG-1, THP-1 were cultured and used as the experiment cell lines. MTT assay was used for proliferation detection, flowcytometry was used to detect apoptosis and cell cycle arrest upon HHT functioning, western blotting was used to detect the protein level changes, viral shRNA transfection was used to suppress the expression level of the target protein candidate, and viral mRNA transfection was used for over-expression. Virtual screening revealed that smad3 from TGF-β pathway might be the candidate for HHT binding. In AML cell line U937 and KG-1, HHT can induce the Ser423/425 phosphorylation of smad3, and this phosphorylation can subsequently activate the TGF-β pathway, causing cell cycle arrest at G1 phase in U937 cells and apoptosis in KG-1 cells, knockdown of smad3 can impair the sensitivity of U937 cell to HHT, and over-expression of smad3 can re-establish the sensitivity in both cell lines. We conclude that smad3 is the probable target protein of HHT and plays an important role in the functioning mechanism of HHT.

Competitive Kinase Enrichment Proteomics Reveals that Abemaciclib Inhibits GSK3β and Activates WNT Signaling

The cellular and organismal phenotypic response to a small-molecule kinase inhibitor is defined collectively by the inhibitor's targets and their functions. The selectivity of small-molecule kinase inhibitors is commonly determined in vitro, using purified kinases and substrates. Recently, competitive chemical proteomics has emerged as a complementary, unbiased, cell-based methodology to define the target landscape of kinase inhibitors. Here, we evaluated and optimized a competitive multiplexed inhibitor bead mass spectrometry (MIB/MS) platform using cell lysates, live cells, and treated mice. Several clinically active kinase inhibitors were profiled, including trametinib, BMS-777607, dasatinib, abemaciclib, and palbociclib. MIB/MS competition analyses of the cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors abemaciclib and palbociclib revealed overlapping and unique kinase targets. Competitive MIB/MS analysis of abemaciclib revealed 83 target kinases, and dose-response MIB/MS profiling revealed glycogen synthase kinase 3 alpha and beta (GSK3α and β) and Ca2+/calmodulin-dependent protein kinase II delta and gamma (CAMKIIδ and γ) as the most potently inhibited. Cell-based and in vitro kinase assays show that in contrast to palbociclib, abemaciclib directly inhibits GSK3α/β and CAMKIIγ/δ kinase activity at low nanomolar concentrations. GSK3β phosphorylates β-catenin to suppress WNT signaling, while abemaciclib (but not palbociclib or ribociclib) potently activates β-catenin-dependent WNT signaling. These data illustrate the power of competitive chemical proteomics to define kinase target specificities for kinase inhibitors, thus informing clinical efficacy, dose-limiting toxicities, and drug-repurposing efforts.Implications: This study uses a rapid and quantitative proteomics approach to define inhibitor-target data for commonly administered therapeutics and provides a cell-based alternative to in vitro kinome profiling. Mol Cancer Res; 16(2); 333-44. ©2017 AACR.

Berbamine induces SMMC-7721 cell apoptosis via upregulating p53, downregulating survivin expression and activating mitochondria signaling pathway

Hepatocellular carcinoma (HCC) is a primary malignancy in the liver, which is a global health problem. The present study aimed to observe the apoptotic effects of berbamine on SMMC-7721 cell lines and to investigate the effects of berbamine on induction of the intrinsic apoptotic pathway. The human HCC SMMC-7721 cells were cultured and cell morphology observed using a phase contrast microscope. SMMC-7721 cell apoptosis was examined by employing a flow cytometry assay. The nuclei of SMMC-7721 cells were stained with DAPI and observed by utilizing a laser fluorescence microscope. Cytochrome c (Cyto c) levels were evaluated by using immunofluorescence staining. The reverse transcription-semi-quantitative polymerase chain reaction (RT-sqPCR) and western blot analysis were used to examine the mRNA and protein levels of B-cell lymphoma 2, (Bcl-2), Bax, Bcl-2-associated X, apoptosis regulator, p53 and survivin, respectively. Berbamine inhibited SMMC-7721 cell growth at 20 and 0 µmol/l, compared with control group (0 µmol/l berbamine). DAPI results demonstrated that berbamine affected the nucleus morphology of SMMC-7721 cells. Berbamine at a concentration of 20 µmol/l (P<0.05) and 40 µmol/l (P<0.01) significantly enhanced apoptosis rate compared with control group. Berbamine triggered Cyto c release from SMMC-7721 cell nuclei to the cytoplasm. Berbamine (10, 20, 40 µmol/l) significantly enhanced Bax and p53 levels and decreased Bcl-2 and survivin levels compared with control group, according to RT-sqPCR and western blot assay findings. In conclusion, berbamine induced SMMC-7721 cell apoptosis, through upregulating p53 expression and downregulating survivin expression, which further triggered mitochondria signaling pathway-mediated apoptosis.

Activation of CaMKIIγ potentiates T-cell acute lymphoblastic leukemia leukemogenesis via phosphorylating FOXO3a

Ca²⁺/calmodulin–dependent protein kinase II γ (CaMKIIγ) can regulate the proliferation and differentiation of myeloid leukemia cells and accelerate chronic myeloid leukemia blast crisis, but the role of CaMKIIγ in T-cell acute lymphoblastic leukemia (T-ALL) leukemogenesis remains poorly understood. We observed that activated (autophosphorylated) CaMKIIγ was invariably present in T-ALL cell lines and in the majority of primary T-ALL samples. Overexpression of CaMKIIγ enhanced the proliferation, colony formation, in vivo tumorigenesis and increased DNA damage of T-ALL leukemia cells. Furthermore, inhibition of CaMKIIγ activity with a pharmacologic inhibitor, gene knock-out, dominant-negative constructs or enhancement of CaMKIIγ activity by overexpression constructs revealed that the activated CaMKIIγ could phosphorylate FOXO3a. In Jurkat cells, the activated CaMKIIγ phosphorylated FOXO3a via directly or indirectly phosphorylating AKT, excluded FOXO3a from the nucleus and inhibited its transcriptional activity. These results indicate that the activated CaMKIIγ may play a key role in T-ALL leukemogenesis, and targeting CaMKIIγ might be a value approach in the treatment of T-ALL.

Demystifying traditional herbal medicine with modern approach

Plants have long been recognized for their therapeutic properties. For centuries, indigenous cultures around the world have used traditional herbal medicine to treat a myriad of maladies. By contrast, the rise of the modern pharmaceutical industry in the past century has been based on exploiting individual active compounds with precise modes of action. This surge has yielded highly effective drugs that are widely used in the clinic, including many plant natural products and analogues derived from these products, but has fallen short of delivering effective cures for complex human diseases with complicated causes, such as cancer, diabetes, autoimmune disorders and degenerative diseases. While the plant kingdom continues to serve as an important source for chemical entities supporting drug discovery, the rich traditions of herbal medicine developed by trial and error on human subjects over thousands of years contain invaluable biomedical information just waiting to be uncovered using modern scientific approaches. Here we provide an evolutionary and historical perspective on why plants are of particular significance as medicines for humans. We highlight several plant natural products that are either in the clinic or currently under active research and clinical development, with particular emphasis on their mechanisms of action. Recent efforts in developing modern multi-herb prescriptions through rigorous molecular-level investigations and standardized clinical trials are also discussed. Emerging technologies, such as genomics and synthetic biology, are enabling new ways for discovering and utilizing the medicinal properties of plants. We are entering an exciting era where the ancient wisdom distilled into the world's traditional herbal medicines can be reinterpreted and exploited through the lens of modern science.

Stabilization of the c-Myc Protein by CAMKIIγ Promotes T Cell Lymphoma

Although high c-Myc protein expression is observed alongside MYC amplification in some cancers, in most cases protein overexpression occurs in the absence of gene amplification, e.g., T cell lymphoma (TCL). Here, Ca2+/calmodulin-dependent protein kinase II γ (CAMKIIγ) was shown to stabilize the c-Myc protein by directly phosphorylating it at serine 62 (S62). Furthermore, CAMKIIγ was shown to be essential for tumor maintenance. Inhibition of CAMKIIγ with a specific inhibitor destabilized c-Myc and reduced tumor burden. Importantly, high CAMKIIγ levels in patient TCL specimens correlate with increased c-Myc and pS62-c-Myc levels. Together, the CAMKIIγ:c-Myc axis critically influences the development and maintenance of TCL and represents a potential therapeutic target for TCL.

Structure-Based Target-Specific Screening Leads to Small-Molecule CaMKII Inhibitors

Target-specific scoring methods are more commonly used to identify small-molecule inhibitors among compounds docked to a target of interest. Top candidates that emerge from these methods have rarely been tested for activity and specificity across a family of proteins. In this study we docked a chemical library into CaMKIIδ, a member of the Ca2+ /calmodulin (CaM)-dependent protein kinase (CaMK) family, and re-scored the resulting protein-compound structures using Support Vector Machine SPecific (SVMSP), a target-specific method that we developed previously. Among the 35 selected candidates, three hits were identified, such as quinazoline compound 1 (KIN-1; N4-[7-chloro-2-[(E)-styryl]quinazolin-4-yl]-N1,N1-diethylpentane-1,4-diamine), which was found to inhibit CaMKIIδ kinase activity at single-digit micromolar IC50 . Activity across the kinome was assessed by profiling analogues of 1, namely 6 (KIN-236; N4-[7-chloro-2-[(E)-2-(2-chloro-4,5-dimethoxyphenyl)vinyl]quinazolin-4-yl]-N1,N1-diethylpentane-1,4-diamine), and an analogue of hit compound 2 (KIN-15; 2-[4-[(E)-[(5-bromobenzofuran-2-carbonyl)hydrazono]methyl]-2-chloro-6-methoxyphenoxy]acetic acid), namely 14 (KIN-332; N-[(E)-[4-(2-anilino-2-oxoethoxy)-3-chlorophenyl]methyleneamino]benzofuran-2-carboxamide), against 337 kinases. Interestingly, for compound 6, CaMKIIδ and homologue CaMKIIγ were among the top ten targets. Among the top 25 targets of 6, IC50 values ranged from 5 to 22 μm. Compound 14 was found to be not specific toward CaMKII kinases, but it does inhibit two kinases with sub-micromolar IC50 values among the top 25. Derivatives of 1 were tested against several kinases including several members of the CaMK family. These data afforded a limited structure-activity relationship study. Molecular dynamics simulations with explicit solvent followed by end-point MM-GBSA free-energy calculations revealed strong engagement of specific residues within the ATP binding pocket, and also changes in the dynamics as a result of binding. This work suggests that target-specific scoring approaches such as SVMSP may hold promise for the identification of small-molecule kinase inhibitors that exhibit some level of specificity toward the target of interest across a large number of proteins.

CAMK2γ in intestinal epithelial cells modulates colitis-associated colorectal carcinogenesis via enhancing STAT3 activation

Inflammation is one of the major risk factors for cancer. Here, we show that calcium/calmodulin-dependent protein kinase II gamma (CAMK2γ) in intestinal epithelial cells (IECs) modulates inflammatory signals and promotes colitis-associated cancer (CAC) in mice. We have identified CAMK2γ as a downstream target of colitis-induced WNT5a signaling. Furthermore, we have shown that CAMK2γ protects against intestine tissue injury by increasing IEC survival and proliferation. CAMK2γ knockout mice displayed reduced CAC. Furthermore, we used bone marrow transplantation to reveal that CAMK2γ in IECs, but not immune cells, was crucial for its effect on CAC. Consistently, transgenic over-expression of CAMK2γ in IECs accelerated CAC development. Mechanistically, CAMK2γ in IECs enhanced epithelial STAT3 activation to promote survival and proliferation of colonic epithelial cells during CAC development. These results thus identify a new molecular mechanism mediated by CAMK2γ in IECs during CAC development, thereby providing a potential new therapeutic target for CAC.

In vitro and in vivo metabolic activation of berbamine to quinone methide intermediate

Berbamine (BBM) is a bisbenzylisoquinoline alkaloid isolated from herbal medicine Berberis amurensis. BBM has been widely used for the treatment of leukemia. Recent studies demonstrated that exposure to BBM can give rise to cytotoxicity. The major objective of this study was to explore the metabolic activation of BBM in vitro and in vivo. Two oxidative metabolites (M1 and M2) and an N-acetylcysteine (NAC) conjugate (M3) were detected in human liver microsomal incubations of BBM supplemented with NAC, and the formation of all metabolites was NADPH dependent. Microsomal inhibition and recombinant P450 enzyme incubation studies demonstrated that P450 3A4 was the major enzyme responsible for the metabolic activation of BBM. In addition, a BBM-cysteine conjugate (M4) was detected in the urine of rats given BBM. The metabolism study will facilitate the understanding of the biochemical mechanisms of BBM-induced cytotoxicity.

CAMK2γ antagonizes mTORC1 activation during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is one of the most deadly cancers that still lacks effective treatments. Dysregulation of kinase signaling has frequently been reported to contribute to HCC. In this study, we used bioinformatic approaches to identify kinases that regulate gene expression changes in human HCCs and two murine HCC models. We identified a role for calcium/calmodulin-dependent protein kinases II gamma isoform (CAMK2γ) in hepatocarcinogenesis. CAMK2γ^-/- mice displayed severely enhanced chemical-induced hepatocarcinogenesis compared with wild-type controls. Mechanistically, CAMK2γ deletion potentiates hepatic activation of mechanistic target of rapamycin complex 1 (mTORC1), which results in hyperproliferation of hepatocytes. Inhibition of mTORC1 by rapamycin effectively attenuates the compensatory proliferation of hepatocytes in CAMK2γ^-/- livers. We further demonstrated that CAMK2γ suppressed growth factor- or insulin-induced mTORC1 activation by inhibiting IRS1/AKT signaling. Taken together, our results reveal a novel mechanism by which CAMK2γ antagonizes mTORC1 activation during hepatocarcinogenesis.

Phosphorylation of calcium/calmodulin-stimulated protein kinase II at T286 enhances invasion and migration of human breast cancer cells

Calcium/calmodulin-stimulated protein kinase II (CaMKII) is a multi-functional kinase that controls a range of cellular functions, including proliferation, differentiation and apoptosis. The biological properties of CaMKII are regulated by multi-site phosphorylation. However, the role that CaMKII phosphorylation plays in cancer cell metastasis has not been examined. We demonstrate herein that CaMKII expression and phosphorylation at T286 is increased in breast cancer when compared to normal breast tissue, and that increased CAMK2 mRNA is associated with poor breast cancer patient prognosis (worse overall and distant metastasis free survival). Additionally, we show that overexpression of WT, T286D and T286V forms of CaMKII in MDA-MB-231 and MCF-7 breast cancer cells increases invasion, migration and anchorage independent growth, and that overexpression of the T286D phosphomimic leads to a further increase in the invasive, migratory and anchorage independent growth capacity of these cells. Pharmacological inhibition of CaMKII decreases MDA-MB-231 migration and invasion. Furthermore, we demonstrate that overexpression of T286D, but not WT or T286V-CaMKII, leads to phosphorylation of FAK, STAT5a, and Akt. These results demonstrate a novel function for phosphorylation of CaMKII at T286 in the control of breast cancer metastasis, offering a promising target for the development of therapeutics to prevent breast cancer metastasis.

Ca2+/calmodulin-dependent protein kinase IIγ enhances stem-like traits and tumorigenicity of lung cancer cells

Highly tumorigenic stem-like cells, considered tumor-initiating cells (TICs), are the main cause of lung cancer initiation, relapse, and drug resistance. In this study, we identified that Ca2+/calmodulin-dependent protein kinase IIγ (CaMKIIγ) was aberrantly expressed in highly tumorigenic stem-like lung cancer cells, and was also correlated with poor prognosis in human lung cancer. Functionally, CaMKIIγ enhanced stem-like traits and the tumorigenicity of lung cancer cells in an Akt- and β-catenin-dependent manner. In addition, we found that CaMKIIγ upregulated Oct4 expression via Akt-mediated histone acetylation. Taken together, our findings reveal a critical role of CaMKIIγ in regulating the stemness and tumorigenicity of lung cancer cells and offer a promising therapeutic target for TICs.

The emerging role of CaMKII in cancer

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a multifunctional serine/threonine kinases best known for its critical role in learning and memory. Recent studies suggested that high levels of CaMKII also expressed in variety of malignant diseases. In this review, we focus on the structure and biology properties of CaMKII, including the role of CaMKII in the regulation of cancer progression and therapy response. We also describe the role of CaMKII in the diagnosis of different kinds of cancer and recent progress in the development of CaMKII inhibitors. These data establishes CaMKII as a novel target whose modulation presents new opportunities for cancer diagnosis and treatment.

Aberrant activation of CaMKIIγ accelerates chronic myeloid leukemia blast crisis

Blast crisis (BC) is the final deadly phase of chronic myeloid leukemia (CML), but its molecular basis remains poorly understood. Here, we show that CML BC is regulated by calcium-calmodulin-dependent kinase IIγ (CaMKIIγ). Genetic deletion of CaMKIIγ greatly inhibits disease progression via selectively impairing the self-renewal of leukemia stem cells (LSCs) in mouse models, whereas overexpression of CaMKIIγ has the opposite effects. In human CML, phosphorylated CaMKIIγ abundance is significantly associated with BC. Moreover, CaMKIIγ phosphorylates and reduces the nuclear cyclin-dependent kinase inhibitor p27Kip1, a critical brake that maintains LSC quiescence. These findings suggest that CaMKIIγ might be an important switch for the transition of CML BC and identify a unique mechanism by which CaMKIIγ promotes the self-renewal of LSCs by deceasing nuclear p27Kip1 to wake up dormant LSCs. Therefore, CaMKIIγ may provide a new therapeutic target to treat CML BC.

SKF-96365 activates cytoprotective autophagy to delay apoptosis in colorectal cancer cells through inhibition of the calcium/CaMKIIγ/AKT-mediated pathway

Store-operated Ca(2+) entry (SOCE) inhibitors are emerging as an attractive new generation of anti-cancer drugs. Here, we report that SKF-96365, an SOCE inhibitor, exhibits potent anti-neoplastic activity by inducing cell-cycle arrest and apoptosis in colorectal cancer cells. In the meantime, SKF-96365 also induces cytoprotective autophagy to delay apoptosis by preventing the release of cytochrome c (cyt c) from the mitochondria into the cytoplasm. Mechanistically, SKF-96365 treatment inhibited the calcium/calmodulin-dependent protein kinase IIγ (CaMKIIγ)/AKT signaling cascade in vitro and in vivo. Overexpression of CaMKIIγ or AKT abolished the effects of SKF-96365 on cancer cells, suggesting a critical role of the CaMKIIγ/AKT signaling pathway in SFK-96365-induced biological effects. Moreover, Hydroxychloroquine (HCQ), an FDA-approved drug used to inhibit autophagy, could significantly augment the anti-cancer effect of SFK-96365 in a mouse xenograft model. To our best knowledge, this is the first report to demonstrate that calcium/CaMKIIγ/AKT signaling can regulate apoptosis and autophagy simultaneously in cancer cells, and the combination of the SOCE inhibitor SKF-96365 with autophagy inhibitors represents a promising strategy for treating patients with colorectal cancer.

On the preparation of transferrin modified artesunate nanoliposomes and their glioma-targeting treatment in-vitro and in-vivo

OBJECTIVE

To prepare transferrin modified artesunate nanoliposomes (Tf-ART-LPs) and study their glioma U87 cells-targeting treatment in-vitro and in-vivo.

METHODS

Ammonium sulfate transmembrane gradient method was used to prepare Tf-ART-LPs, whose size and stability was detected by a Nanosizer. Besides, the encapsulation efficiency and release rate of artesunate (ART) were tested by a ultraviolet spectrophotometer. Further, isothiocyanate (FITC) was used to label nanoliposomes and the cell-targeting property of Tf-ART-LP in-vitro was observed under a fluorescence microscope. In addition, CCK-8 method was used to detect the effect of single nanoliposomes and Tf-ART-LPs on the viability of glioma U87 cells. At last, a subcutaneously implanted tumor model in nude mouse was established for studying the in-vivo anti-tumor effect of Tf-ART-LPs by caudal vein injection. The tumor volume and mice weight were monitored and pathological sections of their major organs were analyzed.

RESULTS

Tf-ART-LPs were spherical with an average diameter of 94.2 nm. They showed no aggregation after being stored in a refrigerator for 14 days at 4°C. The encapsulation efficiency and highest releasing rate (48 hours after being placed in normal saline under 37°C) of ART was 85.9% and 58.7±2.9%, respectively. The uptake rate of U87 cells was 59.8±3.8% for Tf-ART-LPs and only 18.7±4.5% for ART-LPs. While single liposomes almost showed no toxicity, Tf-ART-LP had a concentration-dependent killing effect on U87 cells. Within 32 days of treatment, the growth of U87 cells was well inhibited by Tf-ART-LPs without significant toxicity.

CONCLUSION

In this study, transferrin modified artesunate liposomes we prepared have a good targeting property to glioma U87 cells and good effect on glioma both in-vitro and in-vivo.

CaMKII plays a part in the chondrogenesis of bone marrow-derived mesenchymal stem cells

AIMS

The purpose of the study is to observe the functions of calcium/calmodulin dependent protein kinase II (CaMKII) in the induced chondrogenic differentiation of bone marrow derived mesenchymal stem cells (BMSCs).

METHODS

BMSCs was in vitro isolated and cultured for induced chondrogenesis. Western blot was used to ascertain the expression of CaMKII and phosphorylated CaMKII (PCaMKII, activatory CaMKII) in chondrogenic induced BMSCs. MTT method was utilized to observe the impact of CaMKII on the proliferation of BMSCs. The generation of cartilage matrix in BMSCs cells was detected by toluidine blue staining. The levels of cartilage marker genes COL2A1, Aggrecan and SOX9 in BMSCs were gained by real-time fluorescence quantitative polymerase chain reaction (RT-QPCR). Finally, BMSCs proliferation, cartilage matrix generation and the changes of COL2A1, Aggrecan and SOX9 were surveyed after CaMKII being blocked by CaMKII inhibitor KN93.

RESULTS

Expression of CaMKII and PCaMKII could be found in chondrogenic induced BMSCs. CaMKII had no significant influence on BMSCs proliferation, but the toluidine blue staining was obviously lighter, indicating a significant decline in the expression of COL2A1, Aggrecan and SOX9.

CONCLUSION

As one of the factors influencing the chondrogenic capacity of BMSCs, CaMKII does not impact on BMSCs proliferation, but it can inhibit the chondrogenic ability of BMSCs by influencing its differentiation.

Saponins from Rubus parvifolius L. induce apoptosis in human chronic myeloid leukemia cells through AMPK activation and STAT3 inhibition

BACKGROUND

Saponins are a major active component for the traditional Chinese medicine, Rubus parvifolius L., which has shown clear antitumor activities. However, the specific effects and mechanisms of saponins of Rubus parvifolius L. (SRP) remain unclear with regard to human chronic myeloid leukemia cells. The aim of this study was to investigate inhibition of proliferation and apoptosis induction effects of SRP in K562 cells and further elucidate its regulatory mechanisms.

MATERIALS AND METHODS

K562 cells were treated with different concentrations of SRP and MTT assays were performed to determine cell viability. Apoptosis induction by SRP was determined with FACS and DAPI staining analysis. Western blotting was used to detect expression of apoptosis and survival related genes. Specific inhibitors were added to confirm roles of STAT3 and AMPK pathways in SRP induction of apoptosis.

RESULTS

Our results indicated that SRP exhibited obvious inhibitory effects on the growth of K562 cells, and significantly induced apoptosis. Cleavage of pro-apoptotic proteins was dramatically increased after SRP exposure. SRP treatment also increased the activities of AMPK and JNK pathways, and inhibited the phosphorylation expression level of STAT3 in K562 cells. Inhibition of the AMPK pathway blocked the activation of JNK by SRP, indicating that SRP regulated the expression of JNK dependent on the AMPK pathway. Furthermore, inhibition of the latter significantly conferred resistance to SRP pro- apoptotic activity, suggesting involvement of the AMPK pathway in induction of apoptosis. Pretreatment with a STAT3 inhibitor also augmented SRP induced growth inhibition and cell apoptosis, further confirming roles of the STAT3 pathway after SRP treatment.

CONCLUSIONS

Our results demonstrated that SRP induce cell apoptosis through AMPK activation and STAT3 inhibition in K562 cells. This suggests the possibility of further developing SRP as an alternative treatment option, or perhaps using it as adjuvant chemotherapeutic agent for chronic myeloid leukemia therapy.

Leukemia stem cells: the root of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder characterized by a chromosome translocation that generates the Bcr-Abl oncogene encoding a constitutive kinase activity. Despite remarkable success in controlling CML at chronic phase by Bcr-Abl tyrosine kinase inhibitors (TKIs), a significant proportion of CML patients treated with TKIs develop drug resistance due to the inability of TKIs to kill leukemia stem cells (LSCs) that are responsible for initiation, drug resistance, and relapse of CML. Therefore, there is an urgent need for more potent and safer therapies against leukemia stem cells for curing CML. A number of LSC-associated targets and corresponding signaling pathways, including CaMKII-γ, a critical molecular switch for co-activating multiple LSC-associated signaling pathways, have been identified over the past decades and various small inhibitors targeting LSC are also under development. Increasing evidence shows that leukemia stem cells are the root of CML and targeting LSC may offer a curable treatment option for CML patients. This review summarizes the molecular biology of LSC and its-associated targets, and the potential clinical application in chronic myeloid leukemia.

Leukemia stem cells: the root of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder characterized by a chromosome translocation that generates the Bcr-Abl oncogene encoding a constitutive kinase activity. Despite remarkable success in controlling CML at chronic phase by Bcr-Abl tyrosine kinase inhibitors (TKIs), a significant proportion of CML patients treated with TKIs develop drug resistance due to the inability of TKIs to kill leukemia stem cells (LSCs) that are responsible for initiation, drug resistance, and relapse of CML. Therefore, there is an urgent need for more potent and safer therapies against leukemia stem cells for curing CML. A number of LSC-associated targets and corresponding signaling pathways, including CaMKII-γ, a critical molecular switch for co-activating multiple LSC-associated signaling pathways, have been identified over the past decades and various small inhibitors targeting LSC are also under development. Increasing evidence shows that leukemia stem cells are the root of CML and targeting LSC may offer a curable treatment option for CML patients. This review summarizes the molecular biology of LSC and its-associated targets, and the potential clinical application in chronic myeloid leukemia.

Wogonin suppresses human alveolar adenocarcinoma cell A549 migration in inflammatory microenvironment by modulating the IL-6/STAT3 signaling pathway

Increasing evidence from various clinical and experimental studies has demonstrated that the inflammatory microenvironment facilitates tumor metastasis. Clinically, it will be a promising choice to suppress tumor metastasis by targeting inflammatory microenvironment. Our previous studies have demonstrated that wogonin (a bioflavonoid isolated from the traditional Chinese medicine of Huang-Qin) possesses the anti-metastatic and anti-inflammatory activity, but we have little idea about its efficacy on inflammatory-induced tumor metastasis and the mechanism underlying it. In this study, we focused on epithelial mesenchymal transition (EMT), the first step of tumor metastasis, to evaluate the effects of wogonin on tumor metastasis in inflammatory microenvironment. We found that wogonin inhibited THP-1 conditioned-medium- (CM-) and IL-6-induced EMT by inactivating STAT3 signal. And in wogonin-treated A549 cells which pretreated with THP-1 CM or IL-6, the expression level of E-cadherin, an EMT negative biomarker, increased while that of N-cadherin, Vimentin, and EMT-related transcription factors including Snail and Twist decreased. Moreover, wogonin inhibited IL-6-induced phosphorylation of STAT3, prevented p-STAT3 dimer translocation into the nucleus, and suppressed the DNA-binding activity of p-STAT3. Interestingly, similar results were obtained in the tumor xenografts mice, including downregulation of p-STAT3, N-cadherin, and Vimentin while up-regulation of E-cadherin. Wogonin also inhibit the metastasis of A549 cells in vivo. Taken all data together, we concluded that wogonin suppresses tumor cells migration in inflammatory microenvironment by inactivating STAT3 signal.

Cryptotanshinone acts synergistically with imatinib to induce apoptosis of human chronic myeloid leukemia cells

Imatinib resistance has emerged as a significant clinical problem in chronic myeloid leukemia (CML) treatment. In this study, we investigated the effect and mechanism of combination treatment with imatinib and cryptotanshinone (CPT) in CML cells. Cotreatment with imatinib and CPT showed a significant synergistic killing effect in both imatinib sensitive and resistant CML cell lines, as well as primary CML cells. Furthermore, combination treatment induced apoptosis significantly, as indicated by increases in apoptotic cell fraction and activities of proapoptotic proteins. Subsequent studies revealed that CPT significantly inhibited Bcr/Abl protein expression, as well as phosphorylation expression levels of signal transducer and activator of transcription 3 (STAT3), mammalian target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E (eIF4E), which are critical mediators of Bcr/Abl transformation. Furthermore, CPT in combination with imatinib dramatically decreased the activity of the Bcr/Abl pathway in both K562 and K562-R cells. Our results demonstrated that CPT increased imatinib-induced apoptosis in a Bcr/Abl dependent manner, suggesting a novel strategy for the treatment of CML.

The many faces of calmodulin in cell proliferation, programmed cell death, autophagy, and cancer

Calmodulin (CaM) is a ubiquitous Ca(2+) receptor protein mediating a large number of signaling processes in all eukaryotic cells. CaM plays a central role in regulating a myriad of cellular functions via interaction with multiple target proteins. This review focuses on the action of CaM and CaM-dependent signaling systems in the control of vertebrate cell proliferation, programmed cell death and autophagy. The significance of CaM and interconnected CaM-regulated systems for the physiology of cancer cells including tumor stem cells, and processes required for tumor progression such as growth, tumor-associated angiogenesis and metastasis are highlighted. Furthermore, the potential targeting of CaM-dependent signaling processes for therapeutic use is discussed.

RETRACTED: Ca(2+)/calmodulin-dependent protein kinase IIγ, a critical mediator of the NF-κB network, is a novel therapeutic target in non-small cell lung cancer

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been regretfully retracted at the request of the authors due to mistakes which occurred during the figure preparation. Although the authors published a corrigendum about these mistakes (Cancer Lett. 2016 Aug 1. pii: S0304-3835(16)30443-8), they now feel that it is more appropriate to retract the paper to keep their research at a high standard. All authors have agreed to this decision and apologize for any inconvenience caused by retraction of this article.

Berbamine inhibits the growth of liver cancer cells and cancer-initiating cells by targeting Ca²⁺/calmodulin-dependent protein kinase II

Liver cancer is the third leading cause of cancer deaths worldwide but no effective treatment toward liver cancer is available so far. Therefore, there is an unmet medical need to identify novel therapies to efficiently treat liver cancer and improve the prognosis of this disease. Here, we report that berbamine and one of its derivatives, bbd24, potently suppressed liver cancer cell proliferation and induced cancer cell death by targeting Ca(2+)/calmodulin-dependent protein kinase II (CAMKII). Furthermore, berbamine inhibited the in vivo tumorigenicity of liver cancer cells in NOD/SCID mice and downregulated the self-renewal abilities of liver cancer-initiating cells. Chemical inhibition or short hairpin RNA-mediated knockdown of CAMKII recapitulated the effects of berbamine, whereas overexpression of CAMKII promoted cancer cell proliferation and increased the resistance of liver cancer cells to berbamine treatments. Western blot analyses of human liver cancer specimens showed that CAMKII was hyperphosphorylated in liver tumors compared with the paired peritumor tissues, which supports a role of CAMKII in promoting human liver cancer progression and the potential clinical use of berbamine for liver cancer therapies. Our data suggest that berbamine and its derivatives are promising agents to suppress liver cancer growth by targeting CAMKII. Mol Cancer Ther; 12(10); 2067-77. ©2013 AACR.

Multifaceted roles of GSK-3 and Wnt/β-catenin in hematopoiesis and leukemogenesis: opportunities for therapeutic intervention

Glycogen synthase kinase-3 (GSK-3) is well documented to participate in a complex array of critical cellular processes. It was initially identified in rat skeletal muscle as a serine/threonine kinase that phosphorylated and inactivated glycogen synthase. This versatile protein is involved in numerous signaling pathways that influence metabolism, embryogenesis, differentiation, migration, cell cycle progression and survival. Recently, GSK-3 has been implicated in leukemia stem cell pathophysiology and may be an appropriate target for its eradication. In this review, we will discuss the roles that GSK-3 plays in hematopoiesis and leukemogenesis as how this pivotal kinase can interact with multiple signaling pathways such as: Wnt/β-catenin, phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt/mammalian target of rapamycin (mTOR), Ras/Raf/MEK/extracellular signal-regulated kinase (ERK), Notch and others. Moreover, we will discuss how targeting GSK-3 and these other pathways can improve leukemia therapy and may overcome therapeutic resistance. In summary, GSK-3 is a crucial regulatory kinase interacting with multiple pathways to control various physiological processes, as well as leukemia stem cells, leukemia progression and therapeutic resistance. GSK-3 and Wnt are clearly intriguing therapeutic targets.