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1.  Off-target Lapatinib Activity Sensitizes Colon Cancer Cells through TRAIL Death Receptor Up-regulation 
Science translational medicine  2011;3(86):86ra50.
Lapatinib, a HER2/EGFR inhibitor, is a recently approved targeted therapy for metastatic breast cancer. As lapatinib enhances the efficacy of the antimetabolite capecitabine in breast cancer patients, we lapatinib also enhance the activity of anti-cancer agents in colorectal cancer. We found that lapatinib the pro-apoptotic effects of Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL) and TRAIL receptor antibodies mapatumumab and lexatumumab. Tumors from mice treated with lapatinibTRAIL exhibited more immunostaining for cleaved caspase-8, the extrinsic cell death pathway, tumors from mice treated with lapatinib or TRAIL alone. Furthermore, combination therapy suppressed tumor growth more effectively than treatment. apatinib up-the proapoptotic TRAIL death receptors DR4 and DR5, leading to more efficient induction of apoptosis in the presence of TRAIL receptor agonistsThis activity was independent of EGFR and HER2 off-target induction of DR5 by lapatinib activation of the JNK/c-Jun signaling axis. This activity of lapatinib on TRAIL death receptor expression and signaling may confer therapeutic benefit when increased doses of lapatinib are used in combination with TRAIL-receptor-activating agents.
doi:10.1126/scitranslmed.3001384
PMCID: PMC3769950  PMID: 21653830
2.  Overcoming hypoxia-induced apoptotic resistance through combinatorial inhibition of GSK-3β and CDK1 
Cancer research  2011;71(15):5265-5275.
Tumor hypoxia is an inherent impediment to cancer treatment that is both clinically significant and problematic. In this study, we performed a cell-based screen to identify small molecules that could reverse the apoptotic resistance of hypoxic cancer cells. Among the compounds we identified were a structurally-related group that sensitized hypoxic cancer cells to apoptosis by inhibiting the kinases GSK-3β and CDK1. Combinatorial inhibition of these proteins in hypoxic cancer cells and tumors increased levels of c-Myc and decreased expression of c-IAP2 and the central hypoxia response regulator Hif-1α. In mice, these compounds augmented the hypoxic tumor cell death induced by cytotoxic chemotherapy, blocking angiogenesis and tumor growth. Taken together, our findings suggest that combinatorial inhibition of GSK-3β and CDK1 augment the apoptotic sensitivity of hypoxic tumors, and they offer preclinical validation of a novel and readily translatable strategy to improve cancer therapy.
doi:10.1158/0008-5472.CAN-11-1383
PMCID: PMC3667402  PMID: 21646472
GSK-3β; CDK1; c-Myc; Hif-1α; c-IAP2; hypoxia; apoptosis; drug screen; drug resistance
3.  ATF4 Regulates MYC-mediated Neuroblastoma Cell Death upon Glutamine Deprivation 
Cancer cell  2012;22(5):631-644.
SUMMARY
Oncogenic Myc alters mitochondrial metabolism, making it dependent on exogenous glutamine (Gln) for cell survival. Accordingly, Gln deprivation selectively induces apoptosis in MYC-overexpressing cells via unknown mechanisms. Using MYCN-amplified neuroblastoma as a model, we identify PUMA, NOXA and TRB3 as executors of Gln-starved cells. Gln depletion in MYC-transformed cells induces apoptosis through ATF4-dependent, but p53-independent, PUMA and NOXA induction. MYC-transformed cells depend on both glutamate-oxaloacetate transaminase and glutamate dehydrogenase to maintain Gln homeostasis and suppress apoptosis. Consequently, either ATF4 agonists or glutaminolysis inhibitors potently induce apoptosis in vitro and inhibit tumor growth in vivo. These results reveal mechanisms whereby Myc sensitizes cells to apoptosis and validate ATF4 agonists and inhibitors of Gln metabolism as potential Myc-selective cancer therapeutics.
doi:10.1016/j.ccr.2012.09.021
PMCID: PMC3510660  PMID: 23153536
4.  Integrative genomics identifies LMO1 as a neuroblastoma oncogene 
Nature  2010;469(7329):216-220.
Neuroblastoma is a childhood cancer of the sympathetic nervous system that accounts for approximately 10% of all paediatric oncology deaths1,2. To identify genetic risk factors for neuroblastoma, we performed a genome-wide association study (GWAS) on 2,251 patients and 6,097 control subjects of European ancestry from four case series. Here we report a significant association within LIM domain only 1 (LMO1) at 11p15.4 (rs110419, combined P = 5.2 × 10−16, odds ratio of risk allele = 1.34 (95% confidence interval 1.25–1.44)). The signal was enriched in the subset of patients with the most aggressive form of the disease. LMO1 encodes a cysteine-rich transcriptional regulator, and its paralogues (LMO2, LMO3 and LMO4) have each been previously implicated in cancer. In parallel, we analysed genome-wide DNA copy number alterations in 701 primary tumours. We found that the LMO1 locus was aberrant in 12.4% through a duplication event, and that this event was associated with more advanced disease (P < 0.0001) and survival (P = 0.041). The germline single nucleotide polymorphism (SNP) risk alleles and somatic copy number gains were associated with increased LMO1 expression in neuroblastoma cell lines and primary tumours, consistent with a gain-of-function role in tumorigenesis. Short hairpin RNA (shRNA)-mediated depletion of LMO1 inhibited growth of neuroblastoma cells with high LMO1 expression, whereas forced expression of LMO1 in neuroblastoma cells with low LMO1 expression enhanced proliferation. These data show that common polymorphisms at the LMO1 locus are strongly associated with susceptibility to developing neuroblastoma, but also may influence the likelihood of further somatic alterations at this locus, leading to malignant progression.
doi:10.1038/nature09609
PMCID: PMC3320515  PMID: 21124317
5.  Combinatorial regulation of neuroblastoma tumor progression by N-Myc and hypoxia inducible factor HIF-1α 
Cancer research  2010;70(24):10351-10361.
In human neuroblastoma, amplification of the MYCN gene predicts poor prognosis and resistance to therapy. Because hypoxia contributes to aggressive tumor phenotypes, predominantly via two structurally related hypoxia inducible factors, HIF-1α and HIF-2α, we examined hypoxia responses in MYCN amplified neuroblastoma cells. We demonstrate here that HIF-1α, but not HIF-2α, is preferentially expressed in both MYCN amplified neuroblastoma cells and primary tumors in comparison to samples without MYCN amplification. Our results showed that interplay between N-Myc and HIF-1α plays critical roles in neuroblastoma. For example, high levels of N-Myc override HIF-1α inhibition of cell cycle progression, enabling continued proliferation under hypoxia. Furthermore, both HIF-1α and N-Myc are essential for the Warburg effect (aerobic glycolysis) in neuroblastomas by activating the transcription of multiple glycolytic genes. Of note, expression of Phosphoglycerate Kinase 1 (PGK1), Hexokinase 2 (HK2) and Lactate Dehydrogenase A (LDHA), were each significantly higher in MYCN amplified neuroblastomas compared to tumors without MYCN amplification. Interestingly, MYCN amplified neuroblastoma cells are “addicted” to LDHA enzymatic activity, as its depletion completely inhibits tumorigenesis in vivo. Thus, our results provide mechanistic insights explaining how MYCN amplified neuroblastoma cells contend with hypoxic stress and paradoxically how hypoxia contributes to neuroblastoma aggressiveness through combinatorial effects of N-Myc and HIF-1α. These results also suggest LDHA represents a novel, pharmacologically tractable target for neuroblastoma therapeutics.
doi:10.1158/0008-5472.CAN-10-0740
PMCID: PMC3005134  PMID: 20961996
N-Myc; hypoxia inducible factor; neuroblastoma; tumorigenesis; Warburg effect
6.  Serial transcriptome analysis and cross species integration identifies CENPE as a novel neuroblastoma target 
Cancer research  2010;70(7):2749-2758.
Cancer genomic studies that rely on analysis of biopsies from primary tumors may not fully identify the molecular events associated with tumor progression. We hypothesized that characterizing the transcriptome during tumor progression in the TH-MYCN transgenic model would identify oncogenic drivers that would be targetable therapeutically. We quantified expression of 32,381 murine genes in 9 hyperplastic ganglia harvested at 3 time points, and 4 tumor cohorts of progressively larger size in mice homozygous for the TH-MYCN transgene. We found 93 genes that showed a linearly increasing or decreasing pattern of expression from the preneoplastic ganglia to end stage tumors. Cross-species integration identified 24 genes that were highly expressed in human MYCN amplified neuroblastomas. The genes prioritized were not exclusively driven by increasing Myc transactivation or proliferative rate. We prioritized 3 targets (Cenpe, Gpr49, Impdh2) with previously determined roles in cancer. Using siRNA knockdown in human neuroblastoma cell lines, we further prioritized CENPE due to inhibition of cellular proliferation. Targeting CENPE with the small molecular inhibitor GSK923295 showed inhibition of in vitro proliferation of 19 neuroblastoma cell lines (median IC50=41 nM; range 27–266 nM), and delayed tumor growth in 3 xenograft models (p-values ranged from p<0.0001 to p=0.018). We provide preclinical validation that serial transcriptome analysis of a transgenic mouse model followed by cross-species integration is a useful method to identify therapeutic targets, and identify CENPE as a novel therapeutic candidate in neuroblastoma.
doi:10.1158/0008-5472.CAN-09-3844
PMCID: PMC2848992  PMID: 20233875
7.  Toll-Like Receptor 2 Modulates the Proinflammatory Milieu in Staphylococcus aureus-Induced Brain Abscess  
Infection and Immunity  2005;73(11):7428-7435.
Toll-like receptor 2 (TLR2) is a pattern recognition receptor (PRR) that plays an important role in innate immune recognition of conserved structural motifs on a wide array of pathogens, including Staphylococcus aureus. To ascertain the functional significance of TLR2 in the context of central nervous system (CNS) parenchymal infection, we evaluated the pathogenesis of S. aureus-induced experimental brain abscess in TLR2 knockout (KO) and wild-type (WT) mice. The expression of several proinflammatory mediators, including inducible nitric oxide synthase, tumor necrosis factor alpha, and macrophage inflammatory protein-2, was significantly attenuated in brain abscesses of TLR2 KO mice compared to WT mice during the acute phase of infection. Conversely, interleukin-17 (IL-17), a cytokine produced by activated and memory T cells, was significantly elevated in lesions of TLR2 KO mice, suggesting an association between innate and adaptive immunity in brain abscess. Despite these differences, brain abscess severity in TLR2 KO and WT animals was similar, with comparable mortality rates, bacterial titers, and blood-brain barrier permeability, implying a role for alternative PRRs. Expression of the phagocytic PRRs macrophage scavenger receptor type AI/AII and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was increased in brain abscesses of both TLR2 KO and WT mice compared to uninfected animals. However, LOX-1 induction in brain abscesses of TLR2 KO mice was significantly attenuated compared to WT animals, revealing that the TLR2-dependent signal(s) influence LOX-1 expression. Collectively, these findings reveal the complex nature of gram-positive bacterial recognition in the CNS which occurs, in part, through engagement of TLR2 and highlight the importance of receptor redundancy for S. aureus detection in the CNS.
doi:10.1128/IAI.73.11.7428-7435.2005
PMCID: PMC1273898  PMID: 16239543

Results 1-7 (7)