KU-0060648 inhibits hepatocellular carcinoma cells through DNA-PKcs-dependent and DNA-PKcs-independent mechanisms

Identification of G protein subunit alpha i2 as a promising therapeutic target of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a global health problem. Its incidence and mortality are increasing. Exploring novel therapeutic targets against HCC is important and urgent. We here explored the expression and potential function of Gαi2 (G protein subunit alpha i2) in HCC. The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) database shows that the number of Gαi2 transcripts in HCC tissues is significantly higher than that in the normal liver tissues. Moreover, Gαi2 overexpression in HCC correlates with poor prognosis of the patients. Gαi2 mRNA and protein expression are also elevated in local HCC tissues and different human HCC cells. In patient-derived primary HCC cells and immortalized HepG2 cells, Gαi2 silencing (by targeted shRNA) or knockout (KO, by the dCas9-sgRNA method) largely suppressed cell proliferation and motility, while inducing cell cycle arrest and caspase-apoptosis activation. Moreover, Gαi2 silencing or KO-induced reactive oxygen species (ROS) production and oxidative injury in primary and HepG2 HCC cells. Whereas different antioxidants ameliorated Gαi2-shRNA-induced anti-HCC cell activity. Using a lentiviral construct, Gαi2 overexpression further augmented proliferation and motility of primary and immortalized HCC cells. Further studies revealed that the binding between the transcription factor early growth response zinc finger transcription factor 1 (EGR1) and Gαi2 DNA promoter was significantly increased in HCC tissues and cells. In vivo, intratumoral injection of Gαi2 shRNA adeno-associated virus significantly hindered HCC xenograft growth in nude mice. Moreover, the growth of Gαi2-KO HCC xenografts in the nude mice was remarkably slow. Gαi2 depletion, oxidative injury, and apoptosis induction were detected in Gαi2-silenced or Gαi2-KO HCC xenografts. Together, overexpressed Gαi2 is required for HCC cell growth in vitro and in vivo, representing as a novel and promising diagnosis marker and therapeutic target of HCC.

Development and Evolution of DNA-Dependent Protein Kinase Inhibitors toward Cancer Therapy

DNA double-strand break (DSB) is considered the most deleterious type of DNA damage, which is generated by ionizing radiation (IR) and a subset of anticancer drugs. DNA-dependent protein kinase (DNA-PK), which is composed of a DNA-PK catalytic subunit (DNA-PKcs) and Ku80-Ku70 heterodimer, acts as the molecular sensor for DSB and plays a pivotal role in DSB repair through non-homologous end joining (NHEJ). Cells deficient for DNA-PKcs show hypersensitivity to IR and several DNA-damaging agents. Cellular sensitivity to IR and DNA-damaging agents can be augmented by the inhibition of DNA-PK. A number of small molecules that inhibit DNA-PK have been developed. Here, the development and evolution of inhibitors targeting DNA-PK for cancer therapy is reviewed. Significant parts of the inhibitors were developed based on the structural similarity of DNA-PK to phosphatidylinositol 3-kinases (PI3Ks) and PI3K-related kinases (PIKKs), including Ataxia-telangiectasia mutated (ATM). Some of DNA-PK inhibitors, e.g., NU7026 and NU7441, have been used extensively in the studies for cellular function of DNA-PK. Recently developed inhibitors, e.g., M3814 and AZD7648, are in clinical trials and on the way to be utilized in cancer therapy in combination with radiotherapy and chemotherapy.

Interactions between miRNAs and Double-Strand Breaks DNA Repair Genes, Pursuing a Fine-Tuning of Repair

The repair of DNA damage is a crucial process for the correct maintenance of genetic information, thus, allowing the proper functioning of cells. Among the different types of lesions occurring in DNA, double-strand breaks (DSBs) are considered the most harmful type of lesion, which can result in significant loss of genetic information, leading to diseases, such as cancer. DSB repair occurs through two main mechanisms, called non-homologous end joining (NHEJ) and homologous recombination repair (HRR). There is evidence showing that miRNAs play an important role in the regulation of genes acting in NHEJ and HRR mechanisms, either through direct complementary binding to mRNA targets, thus, repressing translation, or by targeting other genes involved in the transcription and activity of DSB repair genes. Therefore, alteration of miRNA expression has an impact on the ability of cells to repair DSBs, which, in turn, affects cancer therapy sensitivity. This latter gives account of the importance of miRNAs as regulators of NHEJ and HRR and places them as a promising target to improve cancer therapy. Here, we review recent reports demonstrating an association between miRNAs and genes involved in NHEJ and HRR. We employed the Web of Science search query TS (“gene official symbol/gene aliases*” AND “miRNA/microRNA/miR-”) and focused on articles published in the last decade, between 2010 and 2021. We also performed a data analysis to represent miRNA–mRNA validated interactions from TarBase v.8, in order to offer an updated overview about the role of miRNAs as regulators of DSB repair.

Elevated expression of nuclear receptor-binding SET domain 3 promotes pancreatic cancer cell growth

The nuclear receptor-binding SET domain 3 (NSD3) catalyzes methylation of histone H3 at lysine 36 (H3K36), and promotes malignant transformation and progression of human cancer. Its expression, potential functions and underlying mechanisms in pancreatic cancer are studied. Bioinformatics studies and results from local human tissues show that NSD3 is upregulated in human pancreatic cancer tissues, which is correlated with poor overall survival. In primary and established pancreatic cancer cells, NSD3 silencing (by shRNAs) or CRISPR/Cas9-induced NSD3 knockout potently inhibited cell proliferation, migration and invasion, while provoking cell cycle arrest and apoptosis. Conversely, ectopic expression of NSD3-T1232A mutation significantly accelerated proliferation, migration, and invasion of pancreatic cancer cells. H3K36 dimethylation, expression of NSD3-dependent genes (Prkaa2, Myc, Irgm1, Adam12, and Notch3), and mTOR activation (S6K1 phosphorylation) were largely inhibited by NSD3 silencing or knockout. In vivo, intratumoral injection of adeno-associated virus (AAV)-packed NSD3 shRNA potently inhibited pancreatic cancer xenograft growth in nude mice. These results suggest that elevated NSD3 could be an important driver for the malignant progression of pancreatic cancer.

HBO1 overexpression is important for hepatocellular carcinoma cell growth

Hepatocellular carcinoma (HCC) is a common primary liver malignancy lacking effective molecularly-targeted therapies. HBO1 (lysine acetyltransferase 7/KAT7) is a member of MYST histone acetyltransferase family. Its expression and potential function in HCC are studied. We show that HBO1 mRNA and protein expression is elevated in human HCC tissues and HCC cells. HBO1 expression is however low in cancer-surrounding normal liver tissues and hepatocytes. In HepG2 and primary human HCC cells, shRNA-induced HBO1 silencing or CRISPR/Cas9-induced HBO1 knockout potently inhibited cell viability, proliferation, migration, and invasion, while provoking mitochondrial depolarization and apoptosis induction. Conversely, ectopic overexpression of HBO1 by a lentiviral construct augmented HCC cell proliferation, migration and invasion. In vivo, xenografts-bearing HBO1-KO HCC cells grew significantly slower than xenografts with control HCC cells in severe combined immunodeficient mice. These results suggest HBO1 overexpression is important for HCC cell progression.

Centrosomal Localization of RXRα Promotes PLK1 Activation and Mitotic Progression and Constitutes a Tumor Vulnerability

Retinoid X receptor alpha (RXRα), a nuclear receptor of transcription factor, controls various physiological and pathological pathways including cellular growth, proliferation, differentiation, and apoptosis. Here, we report that RXRα is phosphorylated at its N-terminal A/B domain by cyclin-dependent kinase 1 (Cdk1) at the onset of mitosis, triggering its translocation to the centrosome, where phosphorylated-RXRα (p-RXRα) interacts with polo-like kinase 1 (PLK1) through its N-terminal A/B domain by a unique mechanism. The interaction promotes PLK1 activation, centrosome maturation, and mitotic progression. Levels of p-RXRα are abnormally elevated in cancer cell lines, during carcinogenesis in animals, and in clinical tumor tissues. An RXRα ligand XS060, which specifically inhibits p-RXRα/PLK1 interaction but not RXRα heterodimerization, promotes mitotic arrest and catastrophe in a tumor-specific manner. These findings unravel a transcription-independent action of RXRα at the centrosome during mitosis and identify p-RXRα as a tumor-specific vulnerability for developing mitotic drugs with improved therapeutic index.

Dual inhibition of DNA-PKcs and mTOR by CC-115 potently inhibits human renal cell carcinoma cell growth

CC-115 is a dual inhibitor of DNA-PKcs and mTOR, both are valuable therapeutic targets for renal cell carcinoma (RCC). Our results showed that CC-115 inhibited survival and proliferation of established RCC cell lines (786-O and A489) and primary human RCC cells. The dual inhibitor induced selective apoptosis activation in RCC cells, as compared to no cytotoxicity nor apoptotic effects toward normal renal epithelial cells. CC-115 inhibited DNA-PKcs and mTORC1/2 activation in RCC cells. It was however ineffective in DNA-PKcs-mTOR double knockout (DKO) 786-O cells. CC-115 induced feedback autophagy activation in RCC cells. Autophagy inhibitors or Beclin-1/Light chain 3 (LC3) silencing potentiated CC-115-induced anti-RCC cell activity. Conversely, ectopic overexpression of Beclin-1 inhibited CC-115-induced cytotoxicity. At last CC-115 oral administration inhibited 786-O subcutaneous xenograft growth in nude mice. Taken together, dual inhibition of DNA-PKcs and mTOR by CC-115 potently inhibited RCC cell growth.

LIN28B-AS1-IGF2BP1 binding promotes hepatocellular carcinoma cell progression

IGF2BP1 overexpression promotes hepatocellular carcinoma (HCC) progression. Long non-coding RNA LIN28B-AS1 directly binds to IGF2BP1. In the present study, LIN28B-AS1 and IGF2BP1 expression and their potential functions in HCC cells were tested. Genetic strategies were applied to interfere their expression, and cell survival, proliferation and apoptosis were analyzed. We show that LIN28B-AS1 is expressed in established/primary human HCC cells and HCC tissues. RNA-immunoprecipitation (RIP) and RNA pull-down results confirmed that LIN28B-AS1 directly associated with IGF2BP1 protein in HCC cells. LIN28B-AS1 silencing (by targeted siRNAs) or knockout (KO, by CRISPR-Cas9 method) depleted IGF2BP1-dependent mRNAs (IGF2, Gli1, and Myc), inhibiting HCC cell growth, proliferation, migration, and invasion. Conversely, ectopic overexpression of LIN28B-AS1 upregulated IGF2BP1-dependent mRNAs and promoted HCC cell progression in vitro. Importantly, ectopic IGF2BP1 overexpression failed to rescue LIN28B-AS1-KO HepG2 cells. LIN28B-AS1 siRNA and overexpression were ineffective in IGF2BP1-KO HepG2 cells. In vivo, LIN28B-AS1 KO-HepG2 xenograft tumors grew significantly slower than the control tumors in the nude mice. Taken together, we conclude that LIN28B-AS1 associates with IGF2BP1 to promote human HCC cell progression in vitro and in vivo.

C6 ceramide motivates the anticancer sensibility induced by PKC412 in preclinical head and neck squamous cell carcinoma models

The purpose of this study was to evaluate the anti-head and neck squamous cell carcinoma (anti-HNSCC) cell activity by C6 ceramide and multikinase inhibitor PKC412. Experiments were performed on HNSCC cell lines (SQ20B and SCC-9) and primary human oral carcinoma cells. Results showed that PKC412 inhibited HNSCC cell proliferation without provoking apoptosis activation. Cotreatment of C6 ceramide significantly augmented PKC412-induced lethality in HNSCC cells. PKC412 decreased Akt-mammalian target of rapamycin (mTOR) activation in HNSCC cells, facilitated with cotreatment of C6 ceramide. In contrast, exogenous expression of a constitutively active Akt restored Akt-mTOR activation and attenuated lethality by the cotreatment. We propose that Mcl-1 is a primary resistance factor of PKC412. The cytotoxicity of PKC412 in HNSCC cells was potentiated with Mcl-1 short hairpin RNA knockdown, but was attenuated with Mcl-1 overexpression. Intriguingly, C6 ceramide downregulated Mcl-1 in HNSCC cells. In vivo, PKC412 oral administration inhibited SQ20B xenograft tumor growth in severe combined immunodeficient mice. The antitumor activity of PKC412 was further sensitized with coadministration of liposomal C6 ceramide. Together, we suggest that PKC412 could be further studied as a promising anti-HNSCC strategy, alone or in combination with C6 ceramide.

Integrated multi-omics data analysis identifying novel drug sensitivity-associated molecular targets of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and the third-leading cause of malignancy-associated mortality worldwide. HCC cells are highly resistant to chemotherapeutic agents. Therefore, there are currently only two US Food and Drug Administration-approved drugs available for the treatment of HCC. The objective of the present study was to analyze the results of previously published high-throughput drug screening, and in vitro genomic and transcriptomic data from HCC cell lines, and to integrate the obtained results to define the underlying molecular mechanisms of drug sensitivity and resistance in HCC cells. The results of treatment with 225 different small molecules on 14 different HCC cell lines were retrieved from the Genomics of Drug Sensitivity in Cancer database and analyzed. Cluster analysis using the treatment results determined that HCC cell lines consist of two groups, according to their drug response profiles. Continued analyses of these two groups with Gene Set Enrichment Analysis method revealed 6 treatment-sensitive molecular targets (epidermal growth factor receptor, mechanistic target of rapamycin, deoxyribonucleic acid-dependent protein kinase, the Aurora kinases, Bruton's tyrosine kinase and phosphoinositide 3-kinase; all P<0.05) and partially effective drugs. Genetic and genome-wide gene expression data analyses of the determined targets and their known biological partners revealed 2 somatically mutated and 13 differentially expressed genes, which differed between drug-resistant and drug-sensitive HCC cells. Integration of the obtained data into a short molecular pathway revealed a drug treatment-sensitive signaling axis in HCC cells. In conclusion, the results of the present study provide novel drug sensitivity-associated molecular targets for the development of novel personalized and targeted molecular therapies against HCC.

A reproducible model of intramedullary spinal cord tumor in rats bearing RG2 cells

Intramedullary spinal cord tumors (IMSCTs) are lethal diseases to many patients. The lack of adequate animal model has hampered the development of novel treatments. In the current study, a rodent intramedullary glioma model is established to study IMSCT progression. Fischer 344 rats received a intramedullary implantation of RG2 glioma cells. The neurological state of each rat was evaluated on daily basis using the Basso, Beattie and Bresnahan (BBB) scale. Rats implanted with RG2 cells developed significant hind limb paraplegia 20 days after implantation. Magnetic resonance imaging (MRI) scans after three weeks revealed significant intramedullary RG2 tumors in the rats. Forty days post implantation, rats were sacrificed for histopathological examination. Neuro-imaging and HE staining cross sections confirmed intramedullary RG2 glioma cells invading to the spinal cord. Thus, our model displayed many of the same invasive characteristics as human IMSCTs. This model should be a reliable and reproducible methodology to correlate well with the features of human IMSCT.

AMPKα phosphatase Ppm1E upregulation in human gastric cancer is required for cell proliferation

Activation of AMP-activated protein kinase (AMPK) is a valuable anti-cancer strategy. In the current study, we tested expression and potential function of Ca²⁺/calmodulin-dependent protein kinase phosphatase (Ppm1E), an AMPKα phosphatase, in human gastric cancers. Ppm1E expression was elevated in human gastric cancer tissues (vs. normal tissues), which was correlated with AMPK (p-AMPKα, Thr-172) dephosphorylation and mTOR complex 1 (mTORC1) activation. Ppm1E upregulation, AMPK inhibition and mTORC1 activation were also observed in human gastric cancer cell lines (AGS, HGC-27, and SNU601). Intriguingly, Ppm1E knockdown by shRNA induced AMPK activation, mTORC1 inactivation, and proliferation inhibition in AGS cells. On the other hand, forced over-expression of Ppm1E induced further AMPK inhibition and mTORC1 activation to enhance AGS cell proliferation. Remarkably, microRNA-135b-5p (“miR-135b-5p”), an anti-Ppm1E microRNA, was downregulated in both human gastric cancer tissues and cells. Reversely, miR-135b-5p exogenous expression caused Ppm1E depletion, AMPK activation, and AGC cell proliferation inhibition. Together, Ppm1E upregulation in human gastric cancer is important for cell proliferation, possible via regulating AMPK-mTOR signaling.

Ulk1 over-expression in human gastric cancer is correlated with patients' T classification and cancer relapse

Ulk1 is a key autophagy protein. Here, we tested expression and potential function of Ulk1 in human gastric cancer. Ulk1 mRNA and protein were significantly elevated in multiple fresh human gastric cancer tissues. Its level was relatively low in surrounding normal epithelial tissues. Ulk1 over-expression was also observed in several gastric cancer cell lines (AGS, HGC-27, and SNU601). Remarkably, Ulk1 knockdown by targeted-shRNA inhibited AGS gastric cancer cell survival and proliferation. On the other hand, exogenous Ulk1 over-expression could further promote AGS cell survival and proliferation. Immunohistochemistry (IHC) staining assay of 145 paraffin-embedded gastric cancer tissues showed that Ulk1 was over-expressed in majority (114 out of 145) of gastric cancer tissues. Importantly, high Ulk1 expression in gastric cancer was correlated with patients' T classification and cancer relapse. Together, we demonstrate that Ulk1 over-expression in human gastric cancer is pro-survival. Its over-expression is associated with patients' T classification and cancer relapse.

Identification of DNA-PKcs as a primary resistance factor of TIC10 in hepatocellular carcinoma cells

The current study tested the anti-hepatocellular carcinoma (HCC) cell activity of TIC10, a first-in-class small-molecule tumor necrosis (TNF)-related apoptosis-inducing ligand (TRAIL) inducer. TIC10 exerted potent anti-proliferative and pro-apoptotic actions in primary and established human HCC cells. TIC10 blocked Akt-Erk activation, leading to Foxo3a nuclear translocation, as well as TRAIL and death receptor-5 (DR5) transcription in HCC cells. We propose that DNA-PKcs is a major resistance factor of TIC10 possibly via inhibiting Foxo3a nuclear translocation. DNA-PKcs inhibition, knockdown or mutation facilitated TIC10-induced Foxo3a nuclear translocation, TRAIL/DR5 expression and cell apoptosis. Reversely, exogenous DNA-PKcs over-expression inhibited above actions by TIC10. In vivo, oral administration of TIC10 significantly inhibited HepG2 tumor growth in nude mice, which was further potentiated with Nu7026 co-administration. Thus, TIC10 shows promising anti-HCC activity, alone or together with DNA-PKcs inhibitors.

Identification of DNA-PKcs as a primary resistance factor of salinomycin in osteosarcoma cells

Malignant osteosarcoma (OS) is still a deadly disease for many affected patients. The search for the novel anti-OS agent is extremely urgent and important. Our previous study has proposed that salinomycin is a novel anti-OS agent. Here we characterized DNA-dependent protein kinase catalytic subunit (DNA-PKcs) as a primary salinomycin resistance factor in OS cells. DNA-PKcs inhibitors (NU7026, NU7441 and LY294002) or DNA-PKcs shRNA knockdown dramatically potentiated salinomycin-induced death and apoptosis of OS cells (U2OS and MG-63 lines). Further, forced-expression of microRNA-101 (“miR-101”) downregulated DNA-PKcs and augmented salinomycin's cytotoxicity against OS cells. Reversely, over-expression of DNA-PKcs in OS cells inhibited salinomycin's lethality. For the mechanism study, we show that DNA-PKcs is required for salinomycin-induced pro-survival autophagy activation. DNA-PKcs inhibition (by NU7441), shRNA knockdown or miR-101 expression inhibited salinomycin-induced Beclin-1 expression and autophagy induction. Meanwhile, knockdown of Beclin-1 by shRNA significantly sensitized salinomycin-induced OS cell lethality. In vivo, salinomycin administration suppressed U2OS xenograft tumor growth in severe combined immuno-deficient (SCID) mice, and its anti-tumor activity was dramatically potentiated with co-administration of the DNA-PKcs inhibitor NU7026. Together, these results suggest that DNA-PKcs could be a primary resistance factor of salinomycin in OS cells. DNA-PKcs inhibition or silence may thus significantly increase salinomycin's sensitivity in OS cells.

The long non-coding RNA MALAT1 activates Nrf2 signaling to protect human umbilical vein endothelial cells from hydrogen peroxide

The potential effect of the long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) against hydrogen peroxide (H₂O₂)-induced oxidative injury in endothelial cells was tested. We show that forced-expression of MALAT1 using a lentiviral vector ("LV-MALAT1") significantly attenuated H₂O₂-induced death and apoptosis of human umbilical vein endothelial cells (HUVECs). Conversely, knocking down of MALAT1 by targeted siRNA exacerbated H₂O₂-induced HUVEC injury. For the mechanism study, we show that LV-MALAT1 induced Keap1 downregulation, leading to nuclear-factor-E2-related factor 2 (Nrf2) stabilization and activation. Critically, Nrf2 shRNA almost completely abolished LV-MALAT1-mediated HUVEC protection against H₂O₂. Significantly, H₂O₂-induced oxidative stress, lipid peroxidation and DNA damages in HUVECs were attenuated by LV-MALAT1, but were intensified with MALAT1 siRNA. In summary, we identified a novel signaling axis involving MALAT1, Keap1 and Nrf2, which in turn protects HUVECs from oxidative injury.

AMPK activation by Tanshinone IIA protects neuronal cells from oxygen-glucose deprivation

The current study tested the potential neuroprotective function of Tanshinone IIA (ThIIA) in neuronal cells with oxygen-glucose deprivation (ODG) and re-oxygenation (OGDR). In SH-SY5Y neuronal cells and primary murine cortical neurons, ThIIA pre-treatment attenuated OGDR-induced viability reduction and apoptosis. Further, OGDR-induced mitochondrial depolarization, reactive oxygen species production, lipid peroxidation and DNA damages in neuronal cells were significantly attenuated by ThIIA. ThIIA activated AMP-activated protein kinase (AMPK) signaling, which was essential for neuroprotection against OGDR. AMPKα1 knockdown or complete knockout in SH-SY5Y cells abolished ThIIA-induced AMPK activation and neuroprotection against OGDR. Further studies found that ThIIA up-regulated microRNA-135b to downregulate the AMPK phosphatase Ppm1e. Notably, knockdown of Ppm1e by targeted shRNA or forced microRNA-135b expression also activated AMPK and protected SH-SY5Y cells from OGDR. Together, AMPK activation by ThIIA protects neuronal cells from OGDR. microRNA-135b-mediated silence of Ppm1e could be the key mechanism of AMPK activation by ThIIA.

Autophagy inhibition sensitizes LY3023414-induced anti-glioma cell activity in vitro and in vivo

PI3K-AKT-mTOR signaling is a valuable treatment target for human glioma. LY3023414 is a novel, highly-potent and pan PI3K-AKT-mTOR inhibitor. Here, we show that LY3023414 efficiently inhibited survival and proliferation of primary and established human glioma cells. Meanwhile, apoptosis activation was observed in LY3023414-treated glioma cells. LY3023414 blocked AKT-mTOR activation in human glioma cells. Further studies show that LY3023414 induced feedback activation of autophagy in U251MG cells. On the other hand, autophagy inhibition via adding pharmacological inhibitors or silencing Beclin-1/ATG-5 significantly potentiated LY3023414-induced glioma cell apoptosis. In vivo studies demonstrated that U251MG xenograft tumor growth in mice was suppressed by oral administration of LY3023414. Remarkably, LY3023414's anti-tumor activity was further augmented against the Beclin-1-silenced U251MG tumors. Together, our results suggest that targeting PI3K-AKT-mTOR cascade by LY3023414 inhibits human glioma cell growth in vitro and in vivo. Autophagy inhibition could further sensitize LY3023414 against human glioma cells.

The preclinical analysis of TW-37 as a potential anti-colorectal cancer cell agent

TW-37 is a novel, potent and non-peptide Bcl-2 small-molecule inhibitor. Its activity in colorectal cancer (CRC) cells is studied. In both HCT-116 cells and primary human colon cancer cells, treatment with TW-37 at only nM concentration efficiently inhibited cell survival and proliferation. TW-37 also induced caspase-3/9 and apoptosis activation in CRC cells. Feedback autophagy activation was observed in TW-37-treated CRC cells. Reversely pharmacological autophagy inhibition or Beclin-1 knockdown by targeted-shRNA potentiated TW-37-induced apoptosis and killing of CRC cells. In vivo, intravenous injection of TW-37 inhibited HCT-116 tumor growth in mice. TW-37’s anti-tumor activity was further potentiated against Beclin-1-silenced HCT-116 tumors. Together, targeting Bcl-2 family protein by TW-37 efficiently inhibits CRC cell growth in vitro and in vivo. Inhibition of feedback autophagy activation could further sensitize TW-37.

Identification of sphingosine kinase 1 (SphK1) as a primary target of icaritin in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a highly aggressive neoplasm. We aim to explore the anti-HCC activity by a natural prenylflavonoid icaritin. Icaritin was cytotoxic and pro-apoptotic when added to established (HepG2, KYN-2 and Huh-7 lines) and primary human HCC cells. At the signaling level, icaritin inhibited sphingosine kinase 1 (SphK1) activity in HCC cells, which led to pro-apoptotic ceramide production and JNK1 activation. SphK1 inhibition or silence (by shRNA/microRNA) mimicked icaritin-mediated cytotoxicity, and almost nullified icaritin's activity in HepG2 cells. Reversely, exogenous over-expression of SphK1 sensitized icaritin-induced HepG2 cell apoptosis. In vivo, oral administration of icaritin dramatically inhibited HepG2 xenograft growth in SCID mice. Further, SphK1 activity in icaritin-treated tumors was largely inhibited. In summary, icaritin exerts potent anti-HCC activity in vitro and in vivo. SphK1 inhibition could be the primary mechanism of its actions in HCC cells.

Kaempferol induces autophagic cell death of hepatocellular carcinoma cells via activating AMPK signaling

In the present study, we demonstrate that Kaempferol inhibited survival and proliferation of established human hepatocellular carcinoma (HCC) cell lines (HepG2, Huh-7, BEL7402, and SMMC) and primary human HCC cells. Kaempferol treatment in HCC cells induced profound AMP-activated protein kinase (AMPK) activation, which led to Ulk1 phosphorylation, mTOR complex 1 inhibition and cell autophagy. Autophagy induction was reflected by Beclin-1/autophagy gene 5 upregulation and p62 degradation as well as light chain 3B (LC3B)-I to LC3B-II conversion and LC3B puncta formation. Inhibition of AMPK, via AMPKα1 shRNA or dominant negative mutation, reversed above signaling changes. AMPK inhibition also largely inhibited Kaempferol-induced cytotoxicity in HCC cells. Autophagy inhibition, by 3-methyaldenine or Beclin-1 shRNA, also protected HCC cells from Kaempferol. Kaempferol downregulated melanoma antigen 6, the AMPK ubiquitin ligase, causing AMPKα1 stabilization and accumulation. We conclude that Kaempferol inhibits human HCC cells via activating AMPK signaling.

Tumor-specific hepatic stellate cells (tHSCs) induces DIgR2 expression in dendritic cells to inhibit T cells

Tumor-specific hepatic stellate cells (tHSCs) contributes to tumorigenesis and progression of hepatocellular carcinoma (HCC). The potential function of tHSCs on dendritic cells (DCs) was studied here. We discovered that tHSCs co-culture induced upregulation of DIgR2 (dendritic cell-derived immunoglobulin receptor 2) in bone marrow-derived DCs (mDCs). Activation of MEK-ERK is required for DIgR2 expression in mDCs. MEK-ERK inhibitors or shRNA-mediated silence of MEK1/2 in mDCs inhibited tHSCs-induced DIgR2 expression. Meanwhile, tHSCs stimulation decreased production of multiple cytokines (CD80, CD86 and IL-12) in mDCs. Such an effect was almost reversed by DIgR2 shRNA in mDCs. Further, tHSCs-stimulated mDCs induced T-cell hypo-responsiveness, leading to decreased cytotoxic T lymphocyte (CTL) activity and reduced IFN-γ production in splenic T cells. T cell proliferation inhibition and apoptosis were also noticed. These actions on T cells were again largely inhibited by DIgR2 shRNA in mDCs. Together, our results indicate that tHSCs directly induces DIgR2 expression in DCs to inhibit T cells.

Silencing protein kinase C ζ by microRNA-25-5p activates AMPK signaling and inhibits colorectal cancer cell proliferation

Developing novel strategies against human colorectal cancer (CRC) cells is needed. Activation of AMP-activated protein kinase (AMPK) could possibly inhibit CRC cells. Protein kinase C ζ (PKCζ) is an AMPK negative regulator. Here we found that PKCζ expression was significantly elevated in human colon cancer tissues and CRC cells. PKCζ upregulation was correlated with AMPK in-activation and mTOR complex 1 (mTORC1) over-activation. Reversely, PKCζ shRNA knockdown activated AMPK signaling and inhibited HT-29 cell proliferation. Significantly, downregulation of microRNA-25-5p (miR-25-5p), a PKCζ-targeting miRNA, could be the cause of PKCζ upregulation. Exogenous expression of miR-25-5p silenced PKCζ to activate AMPK signaling, which inhibited HT-29 cell proliferation. In vivo studies showed that HT-29 xenograft growth in mice was inhibited after expressing PKCζ shRNA or miR-25-5p. Collectively, PKCζ could be a novel oncogenic protein of human CRC. PKCζ silence, by targeted-shRNA or miR-25-5p expression, activates AMPK and inhibits HT-29 cell proliferation.

ERK inhibition sensitizes CZ415-induced anti-osteosarcoma activity in vitro and in vivo

mTOR is a valuable oncotarget for osteosarcoma. The anti-osteosarcoma activity by a novel mTOR kinase inhibitor, CZ415, was evaluated. We demonstrated that CZ415 potently inhibited survival and proliferation of known osteosarcoma cell lines (U2OS, MG-63 and SaOs2), and primary human osteosarcoma cells. Further, CZ415 provoked apoptosis and disrupted cell cycle progression in osteosarcoma cells. CZ415 treatment in osteosarcoma cells concurrently blocked mTORC1 and mTORC2 activation. Intriguingly, ERK-MAPK activation could be a major resistance factor of CZ415. ERK inhibition (by MEK162/U0126) or knockdown (by targeted ERK1/2 shRNAs) dramatically sensitized CZ415-induced osteosarcoma cell apoptosis. In vivo, CZ415 oral administration efficiently inhibited U2OS tumor growth in mice. Its activity was further potentiated with co-administration of MEK162. Collectively, we demonstrate that ERK inhibition sensitizes CZ415-induced anti-osteosarcoma activity in vitro and in vivo. CZ415 could be further tested as a promising anti-osteosarcoma agent, alone or in combination of ERK inhibition.

Preclinical study of CC223 as a potential anti-ovarian cancer agent

Aberrant activation of mTOR contributes to ovarian cancer progression. CC223 is a novel and potent mTOR kinase inhibitor. The current study tested its activity against human ovarian cancer cells. We showed that CC223, at nM concentrations, inhibited survival and proliferation of established/primary human ovarian cancer cells. Further, significant apoptosis activation was observed in CC223-treated ovarian cancer cells. CC223 disrupted assembly of mTOR complex 1 (mTORC1) and mTORC2 in SKOV3 cells. Meanwhile, activation of mTORC1 and mTORC2 was almost completely blocked by CC223. Intriguingly, restoring mTOR activation by introduction of a constitutively-active Akt1 only partially inhibited CC223-induced cytotoxicity in SKOV3 cells. Further studies showed that CC223 inhibited sphingosine kinase 1 (SphK1) activity and induced reactive oxygen species (ROS) production in SKOV3 cells. At last, oral administration of CC223 potently inhibited SKOV3 xenografted tumor growth in nude mice. The results of this study imply that CC223 could be further studied as a potential anti-ovarian cancer agent.

CC-223 blocks mTORC1/C2 activation and inhibits human hepatocellular carcinoma cells in vitro and in vivo

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related human mortalities. Over-activation of mammalian target of rapamycin (mTOR) is important for HCC tumorigenesis and progression. The current study assessed the potential anti-HCC activity by a novel mTOR kinase inhibitor, CC-223. We demonstrate that CC-223, at nM concentrations, induced profound cytotoxic and anti-proliferative activities against established HCC cell lines (HepG2, KYN-2 and Huh-7) and primary human HCC cells. Meanwhile, CC-223 activated caspase-3/-9 and apoptosis in the above HCC cells. CC-223 concurrently blocked mTORC1 and mTORC2 activation, and its cytotoxicity against HCC cells was much more potent than the traditional mTORC1 inhibitors (RAD001 and rapamycin). Further studies demonstrated that CC-223 disrupted mitochondrial function, and induced mitochondrial permeability transition pore (mPTP) opening and reactive oxygen species (ROS) production. On the other hand, ROS scavengers and mPTP blockers (cyclosporin A or sanglifehrin A) largely attenuated CC-223-induced HepG2 cell apoptosis. In vivo studies showed that oral administration of CC-223 dramatically inhibited growth of HepG2 xenografts in severe combined immuno-deficient (SCID) mice. mTORC1/2 activation was also blocked in xenografts with CC-223 administration. Together, CC-223 simultaneously blocks mTORC1/2 and efficiently inhibits human HCC cells.

Gab3 overexpression in human glioma mediates Akt activation and tumor cell proliferation

This current study tested expression and potential biological functions of Gab3 in human glioma. Gab3 mRNA and protein expression was significantly elevated in human glioma tissues and glioma cells. Its level was however low in normal brain tissues and primary human astrocytes. In both established (U251MG cell line) and primary human glioma cells, Gab3 knockdown by shRNA/siRNA significantly inhibited Akt activation and cell proliferation. Reversely, forced Gab3 overexpression in U251MG cells promoted Akt activation and cell proliferation. In vivo, the growth of U251MG tumors in nude mice was inhibited following expressing Gab3 shRNA. Akt activation in cancer tissues was also suppressed by Gab3 shRNA. Together, we conclude that Gab3 overexpression in human glioma mediates Akt activation and cancer cell proliferation.

micorRNA-101 silences DNA-PKcs and sensitizes pancreatic cancer cells to gemcitabine

Gemcitabine sensitization is important for the treatment of pancreatic cancer. We have previously shown that DNA-dependent protein kinase catalytic subunit (DNA-PKcs) over-expression causes Akt activation and gemcitabine resistance in pancreatic cancer cells. Here, we aim to downregulate DNA-PKcs via introduction of micorRNA-101 ("miR-101"). We showed that forced-expression of miR-101 downregulated DNA-PKcs and potentiated gemcitabine-induced PANC-1 pancreatic cancer cell death and apoptosis. Contrarily, miR-101 depletion through expressing antagomiR-101 in PANC-1 cells resulted in DNA-PKcs upregulation and gemcitabine resistance. DNA-PKcs downregulation is the primary reason of gemcitabine-sensitization by miR-101. DNA-PKcs inhibition (by NU7026) or silence (by targeted siRNAs) disabled miR-101-mediaetd gemcitabine sensitization. Significantly, Akt Ser-473 phosphorylation in PANC-1 cells was also inhibited by miR-101, but was augmented with antagomiR-101 expression. Importantly, we showed that miR-101 level was downregulated in gemcitabine-resistant human pancreatic cancer tissues, which was correlated with DNA-PKcs upregulation. Together, these results suggest that miR-101 sensitizes PANC-1 cells to gemcitabine possibly via downregulating DNA-PKcs.

Autophagy prevention sensitizes AKTi-1/2-induced anti-hepatocellular carcinoma cell activity in vitro and in vivo

Molecule-targeted therapy has become the research focus for hepatocellular carcinoma (HCC). Persistent PI3K-AKT activation is often detected in HCC, representing a valuable oncotarget for treatment. Here, we tested the anti-HCC activity by a potent AKT inhibitor: AKT inhibitor 1/2 (AKTi-1/2). In both established (HepG2 and Huh-7) and primary human HCC cells, treatment with AKTi-1/2 inhibited cell survival and proliferation, but induced cell apoptosis. AKTi-1/2 blocked AKT-mTOR activation, yet simultaneously provoked cytoprotective autophagy in HCC cells. The latter was evidenced by ATG-5 and Beclin-1 upregulation, p62 downregulation as well as LC3B-GFP puncta formation. Autophagy inhibition, via pharmacological inhibitors (3-methyladenine, ammonium chloride, and bafilomycin A1) or Beclin-1 siRNA knockdown, significantly potentiated AKTi-1/2-induced HepG2 cell death and apoptosis. In nude mice, AKTi-1/2 intraperitoneal injection inhibited HepG2 tumor growth. Significantly, its anti-tumor activity in vivo was further sensitized when combined with Beclin-1 shRNA knockdown in HepG2 tumors. Together, these results demonstrate that autophagy activation serves as a main resistance factor of AKTi-1/2 in HCC cells. Autophagy prevention therefore sensitizes AKTi-1/2-induced anti-HCC activity in vitro and in vivo.

Tissue- and Serum-Associated Biomarkers of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), one of the leading causes of cancer deaths in the world, is offering a challenge to human beings, with the current modes of treatment being a palliative approach. Lack of proper curative or preventive treatment methods encouraged extensive research around the world with an aim to detect a vaccine or therapeutic target biomolecule that could lead to development of a drug or vaccine against HCC. Biomarkers or biological disease markers have emerged as a potential tool as drug/vaccine targets, as they can accurately diagnose, predict, and even prevent the diseases. Biomarker expression in tissue, serum, plasma, or urine can detect tumor in very early stages of its development and monitor the cancer progression and also the effect of therapeutic interventions. Biomarker discoveries are driven by advanced techniques, such as proteomics, transcriptomics, whole genome sequencing, micro- and micro-RNA arrays, and translational clinics. In this review, an overview of the potential of tissue- and serum-associated HCC biomarkers as diagnostic, prognostic, and therapeutic targets for drug development is presented. In addition, we highlight recently developed micro-RNA, long noncoding RNA biomarkers, and single-nucleotide changes, which may be used independently or as complementary biomarkers. These active investigations going on around the world aimed at conquering HCC might show a bright light in the near future.

microRNA-153 Targets mTORC2 Component Rictor to Inhibit Glioma Cells

Rictor upregulation and mTORC complex 2 (mTORC2) over-activation participate in glioma cell progression, yet the underling mechanisms are not known. We here identified microRNA-153 (miR-153) as a potential anti-Rictor miRNA, which was downregulated in multiple human glioma tissues and glioma cell lines (U87MG, T98G, U373MG and U251MG). miR-153 downregulation was correlated with Rictor (mRNA and protein) upregulation and p-Akt Ser473 (the mTORC2 indicator) over-activation in the glioma tissues and cells. Our in vitro evidences suggested that Rictor could be one primary target of miR-153 in glioma cells. Exogenous overexpression of miR-153 downregulated Rictor (mRNA and protein) and decreased p-Akt Ser473 in U87MG cells, leading to significant growth inhibition and apoptosis activation. Notably, U87MG cells with Rictor shRNA knockdown showed similar phenotypes of cells with miR-153 overexpression. More importantly, in Rictor-silenced U87MG cells, miR-153 expression failed to further affect cell growth nor apoptosis. In vivo, we showed that miR-153 overexpression dramatically inhibited U87MG tumor growth in nude mice. Together, these results suggest that miR-153 downregulation could be one important reason of Rictor upregulation and mTORC2 over-activation in glioma cells. Further, miR-153-induced anti-glioma cell activity is possibly via downregulating Rictor.