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1.  KRAS Genotype Correlates with Proteasome Inhibitor Ixazomib Activity in Preclinical In Vivo Models of Colon and Non-Small Cell Lung Cancer: Potential Role of Tumor Metabolism 
PLoS ONE  2015;10(12):e0144825.
In non-clinical studies, the proteasome inhibitor ixazomib inhibits cell growth in a broad panel of solid tumor cell lines in vitro. In contrast, antitumor activity in xenograft tumors is model-dependent, with some solid tumors showing no response to ixazomib. In this study we examined factors responsible for ixazomib sensitivity or resistance using mouse xenograft models. A survey of 14 non-small cell lung cancer (NSCLC) and 6 colon xenografts showed a striking relationship between ixazomib activity and KRAS genotype; tumors with wild-type (WT) KRAS were more sensitive to ixazomib than tumors harboring KRAS activating mutations. To confirm the association between KRAS genotype and ixazomib sensitivity, we used SW48 isogenic colon cancer cell lines. Either KRAS-G13D or KRAS-G12V mutations were introduced into KRAS-WT SW48 cells to generate cells that stably express activated KRAS. SW48 KRAS WT tumors, but neither SW48-KRAS-G13D tumors nor SW48-KRAS-G12V tumors, were sensitive to ixazomib in vivo. Since activated KRAS is known to be associated with metabolic reprogramming, we compared metabolite profiling of SW48-WT and SW48-KRAS-G13D tumors treated with or without ixazomib. Prior to treatment there were significant metabolic differences between SW48 WT and SW48-KRAS-G13D tumors, reflecting higher oxidative stress and glucose utilization in the KRAS-G13D tumors. Ixazomib treatment resulted in significant metabolic regulation, and some of these changes were specific to KRAS WT tumors. Depletion of free amino acid pools and activation of GCN2-eIF2α-pathways were observed both in tumor types. However, changes in lipid beta oxidation were observed in only the KRAS WT tumors. The non-clinical data presented here show a correlation between KRAS genotype and ixazomib sensitivity in NSCLC and colon xenografts and provide new evidence of regulation of key metabolic pathways by proteasome inhibition.
PMCID: PMC4692403  PMID: 26709701
2.  Sequential activation of Snail1 and N-Myc modulates Sonic Hedgehog-induced transformation of neural cells 
Cancer research  2011;71(15):5336-5345.
Activation of the Sonic Hedgehog (Shh) pathway and increased expression of Gli1 play an important role in proliferation and transformation of granule cell progenitors (GCPs) in the developing cerebellum. Medulloblastomas arising from cerebellar GCPs are frequently driven by Shh pathway-activating mutations, however molecular mechanisms of Shh pathway dysregulation and transformation of neural progenitors remain poorly defined. We report that the transcription factor and oncogene Snail1 (Sna1) is directly induced by Shh pathway activity in GCPs, murine medulloblastomas, and human medulloblastoma cells. Enforced expression of Sna1 was sufficient to induce GCPs and medulloblastoma cell proliferation in the absence of Shh/Gli1 exposure. Additionally, enforced expression of Sna1 increased transformation of medulloblastoma cells in vitro and in vivo. Analysis of potential Sna1 targets in neural cells revealed a novel Sna1 target, N-Myc, a transcription factor known to play a role in Shh-mediated GCP proliferation and medulloblastoma formation. We found that Sna1 directly induced transcription of N-Myc in human medulloblastoma cells, and that depletion of N-Myc ablated the Sna1-induced proliferation and transformation. Taken together, these results provide further insight into the mechanism of Shh-induced transformation of neural progenitor cells and suggest that induction of Sna1 may serve to amplify the oncogenic potential of Shh pathway activation through N-Myc induction.
PMCID: PMC3412689  PMID: 21646478
Snail; Shh; Medulloblastoma; N-Myc; Granule Cell Progenitors
3.  Phase 1 study of MLN8054, a selective inhibitor of Aurora A kinase in patients with advanced solid tumors 
Aurora A kinase is critical in assembly and function of the mitotic spindle. It is overexpressed in various tumor types and implicated in oncogenesis and tumor progression. This trial evaluated the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of MLN8054, a selective small-molecule inhibitor of Aurora A kinase.
In this first-in-human, dose-escalation study, MLN8054 was given orally for 7, 14, or 21 days followed by a 14-day treatment-free period. Escalating cohorts of 3–6 patients with advanced solid tumors were treated until DLT was seen in ≥2 patients in a cohort. Serial blood samples were collected for pharmacokinetics and skin biopsies were collected for pharmacodynamics.
Sixty-one patients received 5, 10, 20, 30 or 40 mg once daily for 7 days; 25, 35, 45 or 55 mg/day in four divided doses (QID) for 7 days; or 55, 60, 70 or 80 mg/day plus methylphenidate or modafinil with daytime doses (QID/M) for 7–21 days. DLTs of reversible grade 3 benzodiazepine-like effects defined the estimated MTD of 60 mg QID/M for 14 days. MLN8054 was absorbed rapidly, exposure was dose-proportional, and terminal half-life was 30-40 hours. Three patients had stable disease for >6 cycles.
MLN8054 dosing for up to 14 days of a 28-day cycle was feasible. Reversible somnolence was dose limiting and prevented achievement of plasma concentrations predicted necessary for target modulation. A recommended dose for investigation in phase 2 trials was not established. A second-generation Aurora A kinase inhibitor is in development.
PMCID: PMC3026871  PMID: 20607239
MLN8054; Aurora A kinase; dose-limiting toxicity; pharmacokinetics; pharmacodynamics
4.  Neural Stem Cell– and Schwann Cell–Loaded Biodegradable Polymer Scaffolds Support Axonal Regeneration in the Transected Spinal Cord 
Tissue Engineering. Part A  2009;15(7):1797-1805.
Biodegradable polymer scaffolds provide an excellent approach to quantifying critical factors necessary for restoration of function after a transection spinal cord injury. Neural stem cells (NSCs) and Schwann cells (SCs) support axonal regeneration. This study examines the compatibility of NSCs and SCs with the poly-lactic-co-glycolic acid polymer scaffold and quantitatively assesses their potential to promote regeneration after a spinal cord transection injury in rats. NSCs were cultured as neurospheres and characterized by immunostaining for nestin (NSCs), glial fibrillary acidic protein (GFAP) (astrocytes), βIII-tubulin (immature neurons), oligodendrocyte-4 (immature oligodendrocytes), and myelin oligodendrocyte (mature oligodendrocytes), while SCs were characterized by immunostaining for S-100. Rats with transection injuries received scaffold implants containing NSCs (n = 17), SCs (n = 17), and no cells (control) (n = 8). The degree of axonal regeneration was determined by counting neurofilament-stained axons through the scaffold channels 1 month after transplantation. Serial sectioning through the scaffold channels in NSC- and SC-treated groups revealed the presence of nestin, neurofilament, S-100, and βIII tubulin–positive cells. GFAP-positive cells were only seen at the spinal cord–scaffold border. There were significantly more axons in the NSC- and SC- treated groups compared to the control group. In conclusion, biodegradable scaffolds with aligned columns seeded with NSCs or SCs facilitate regeneration across the transected spinal cord. Further, these multichannel biodegradable polymer scaffolds effectively serve as platforms for quantitative analysis of axonal regeneration.
PMCID: PMC2792101  PMID: 19191513
5.  The Human Factors YY1 and LSF Repress the Human Immunodeficiency Virus Type 1 Long Terminal Repeat via Recruitment of Histone Deacetylase 1 
Journal of Virology  2000;74(15):6790-6799.
Enigmatic mechanisms restore the resting state in activated lymphocytes following human immunodeficiency virus type 1 (HIV-1) infection, rarely allowing persistent nonproductive infection. We detail a mechanism whereby cellular factors could establish virological latency. The transcription factors YY1 and LSF cooperate in repression of transcription from the HIV-1 long terminal repeat (LTR). LSF recruits YY1 to the LTR via the zinc fingers of YY1. The first two zinc fingers were observed to be sufficient for this interaction in vitro. A mutant of LSF incapable of binding DNA blocked repression. Like other transcriptional repressors, YY1 can function via recruitment of histone deacetylase (HDAC). We find that HDAC1 copurifies with the LTR-binding YY1-LSF repressor complex, the domain of YY1 that interacts with HDAC1 is required to repress the HIV-1 promoter, expression of HDAC1 augments repression of the LTR by YY1, and the deacetylase inhibitor trichostatin A blocks repression mediated by YY1. This novel link between HDAC recruitment and inhibition of HIV-1 expression by YY1 and LSF, in the natural context of a viral promoter integrated into chromosomal DNA, is the first demonstration of a molecular mechanism of repression of HIV-1. YY1 and LSF may establish transcriptional and virological latency of HIV, a state that has recently been recognized in vivo and has significant implications for the long-term treatment of AIDS.
PMCID: PMC112196  PMID: 10888618

Results 1-5 (5)