Sphingosine kinase-2 inhibition improves mitochondrial function and survival after hepatic ischemia-reperfusion

BACKGROUND & AIMS

The mitochondrial permeability transition (MPT) and inflammation play important roles in liver injury caused by ischemia-reperfusion (IR). This study investigated the roles of sphingosine kinase-2 (SK2) in mitochondrial dysfunction and inflammation after hepatic IR.

METHODS

Mice were gavaged with vehicle or ABC294640 (50 mg/kg), a selective inhibitor of SK2, 1 h before surgery and subjected to 1 h-warm ischemia to ~70% of the liver followed by reperfusion.

RESULTS

Following IR, hepatic SK2 mRNA and sphingosine-1-phosphate (S1P) levels increased ~25- and 3-fold, respectively. SK2 inhibition blunted S1P production and liver injury by 54-91%, and increased mouse survival from 28% to 100%. At 2 h after reperfusion, mitochondrial depolarization was observed in 74% of viable hepatocytes, and mitochondrial voids excluding calcein disappeared, indicating MPT onset in vivo. SK2 inhibition decreased mitochondrial depolarization and prevented MPT onset. Inducible nitric oxide synthase, phosphorylated NFκB-p65, TNFα mRNA, and neutrophil infiltration, all increased markedly after hepatic IR, and these increases were blunted by SK2 inhibition. In cultured hepatocytes, anoxia/re-oxygenation resulted in increases of SK2 mRNA, S1P levels, and cell death. SK2 siRNA and ABC294640 each substantially decreased S1P production and cell death in cultured hepatocytes.

CONCLUSIONS

SK2 plays an important role in mitochondrial dysfunction, inflammation responses, hepatocyte death, and survival after hepatic IR and represents a new target for the treatment of IR injury.

Structural brain alterations before mild cognitive impairment in ADNI: validation of volume loss in a predefined antero-temporal region

Volume losses in the medial temporal lobe, posterior cingulated, and orbitofrontal region have been observed in Alzheimer's disease (AD). Smaller reductions in similar regions have also been reported in amnestic mild cognitive impairment (aMCI), a canonical precursor to AD. We previously demonstrated that volume loss in bilateral anteromedial temporal lobe is present at baseline in longitudinally followed normal subjects who later developed MCI or AD. In this study we compared grey matter volumes within this predefined anteromedial temporal region (AMTR) at baseline between: 1) normal subjects enrolled in the Alzheimer's Disease Neuroimaging Initiative (ADNI) who subsequently developed cognitive complaints as reflected in a CDR memory box score of 0.5; and 2) normal subjects who remained normal over a median of 48 months of follow-up (CDR sum of boxes 0). We found significantly decreased volume within AMTR in the ADNI memory complainers. To relate AMTR results to those from conventional anatomy, we demonstrate that volumes extracted with the ICBM amygdala region had the best correspondence with AMTR volumes. In contrast, regions that have demonstrated volume loss in frank MCI and AD in ADNI, e.g., the posterior cingulate, did not show volume loss. These findings provide independent confirmation that volume changes preceding MCI occur in AMTR, a region of overlap between amygdala and anterior hippocampus.

Prediction of preclinical Alzheimer's disease: longitudinal rates of change in cognition

Preclinical Alzheimer's disease (pAD) reflects neuropathological findings of AD in cognitively normal subjects. The present study represents an effort to determine if differences could be identified in the longitudinal patterns of cognitive performance in persons classified as pAD compared to those who did not meet criteria for AD at autopsy. We included 121 subjects who were cognitively normal from baseline through their last assessment before death and who underwent autopsy. Participants were classified into two groups: pathologically normal (PN; NIA-Reagan low or no-likelihood of AD, n = 89) and preclinical AD (pAD; NIA-Reagan criteria of intermediate or high-likelihood of AD in the absence of clinical dementia symptoms, n = 32) followed for a mean 7.5 years prior to death. Longitudinal rates and patterns of change in scores on a standard cognitive battery were compared between these two groups. While cognitive results at baseline and last evaluations revealed no clear cross sectional group differences after adjustment for age, ApoE status, education, and gender, statistically significant differences between the pAD and PN groups in slope of decline were seen on a composite score of cognitive function. Further analyses showed three components of this score reached significance: constructional praxis, delayed recall of a word list, and category verbal fluency. Despite being clinically viewed as normal at enrollment and at the final exam, there are significant differences in rates of cognitive decline in participants classified as pAD compared to those without this pathology. Longitudinal changes in slope of decline in specific cognitive test measures can serve as non-invasive methods for the detection of pAD.

"End-stage" neurofibrillary tangle pathology in preclinical Alzheimer's disease: fact or fiction?

Among individuals who were cognitively intact before death, autopsies may reveal some Alzheimer's disease-type pathology. The presence of end-stage pathology in cognitively intact persons would support the hypothesis that pathological markers are epiphenomena. We assessed advanced neurofibrillary (Braak stages V and VI) pathology focusing on nondemented individuals. Data from the National Alzheimer's Coordinating Center database (n = 4,690 included initially) and from the Nun Study (n = 526 included initially) were analyzed, with antemortem information about global cognition and careful postmortem studies available from each case. Global cognition (final Mini-Mental State Examination scores (MMSE) and clinical 'dementia' status) was correlated with neuropathology, including the severity of neurofibrillary pathology (Braak stages and neurofibrillary tangle counts in cerebral neocortex). Analyses support three major findings: 1. Braak stage V cases and Braak VI cases are significantly different from each other in terms of associated antemortem cognition; 2. There is an appreciable range of pathology within the category of Braak stage VI based on tangle counts such that brains with the most neurofibrillary tangles in neocortex always had profound antemortem cognitive impairment; and 3. There was no nondemented case with final MMSE score of 30 within a year of life and Braak stage VI pathology. It may be inappropriate to combine Braak stages V and VI cases, particularly in patients with early cognitive dysfunction, since the two pathological stages appear to differ dramatically in terms of both pathological severity and antemortem cognitive status. There is no documented example of truly end-stage neurofibrillary pathology coexisting with intact cognition.

Sphingosine kinase 2 mediates cerebral preconditioning and protects the mouse brain against ischemic injury

BACKGROUND AND PURPOSE

Cerebral preconditioning provides insights into endogenous mechanisms that protect the brain from ischemic injury. Hypoxia and the anesthetic isoflurane are powerful preconditioning agents. Recent data show that sphingosine 1-phosphate receptor stimulation improves outcome in rodent models of stroke. Endogenous sphingosine 1-phosphate levels are controlled by the expression and activity of sphingosine kinases (SPK). We hypothesize that SPK upregulation mediates preconditioning induced by isoflurane and hypoxia and reduces ischemic injury.

METHODS

Male wild-type C57BL/J, SPK1(-/-) and SPK2(-/-) mice were exposed to isoflurane or hypoxia preconditioning before transient middle cerebral artery occlusion. Infarct volume and neurological outcome were measured 24 hours later. SPK inhibitors (SKI-II and ABC294640) were used to test the involvement of SPK2. Expressions of SPK1, SPK2, and hypoxia-inducible factor 1α were determined. Primary cultures of mouse cortical neurons were exposed to isoflurane before glutamate- or hydrogen peroxide-induced cell death.

RESULTS

Isoflurane preconditioning and hypoxia preconditioning significantly reduced infarct volume and improved neurological outcome in wild-type and SPK1(-/-) mice but not in SPK2(-/-) mice. Pretreatment with SKI-II or ABC294640 abolished the isoflurane preconditioning-induced tolerance. Western blot showed a rapid and sustained increase in SPK2 level, whereas SPK1 level was similar between preconditioned mice and controls. Hypoxia-inducible factor 1α was upregulated in wild-type isoflurane-preconditioned mice but not in SPK2(-/-). Isoflurane preconditioning protected primary neurons against cell death, which was abolished in ABC294640-treated cells.

CONCLUSIONS

Applying genetic and pharmacological approaches, we demonstrate that neuronal SPK2 isoform plays an important role in cerebral preconditioning.

Ablation of sphingosine kinase-2 inhibits tumor cell proliferation and migration

Sphingosine kinases (SK) regulate the balance between proapoptotic ceramides and mitogenic sphingosine-1-phosphate (S1P); however, the functions of the two isoenzymes (SK1 and SK2) in tumor cells are not well defined. Therefore, RNA interference was used to assess the individual roles of SK1 and SK2 in tumor cell sphingolipid metabolism, proliferation, and migration/invasion. Treatment of A498, Caki-1, or MDA-MB-231 cells with siRNAs specific for SK1 or SK2 effectively suppressed the expression of the target mRNA and protein. Ablation of SK1 did not affect mRNA or protein levels of SK2 and reduced intracellular levels of S1P while elevating ceramide levels. In contrast, ablation of SK2 elevated mRNA, protein, and activity levels of SK1 and increased cellular S1P levels. Interestingly, cell proliferation and migration/invasion were suppressed more by SK2-selective ablation than by SK1-selective ablation, showing that the increased S1P does not rescue these phenotypes. Similarly, exogenous S1P did not rescue the cells from the antiproliferative or antimigratory effects of the siRNAs. Consistent with these results, differential effects of SK1- and SK2-selective siRNAs on signaling proteins, including p53, p21, ERK1, ERK2, FAK, and VCAM1, indicate that SK1 and SK2 have only partially overlapping functions in tumor cells. Overall, these data indicate that loss of SK2 has stronger anticancer effects than does suppression of SK1. Consequently, selective inhibitors of SK2 may provide optimal targeting of this pathway in cancer chemotherapy.

Discovery and evaluation of inhibitors of human ceramidase

The ceramide/sphingosine-1-phosphate (S1P) rheostat has been hypothesized to play a critical role in regulating tumor cell fate, with elevated levels of ceramide inducing death and elevated levels of S1P leading to survival and proliferation. Ceramidases are key enzymes that control this rheostat by hydrolyzing ceramide to produce sphingosine and may also confer resistance to drugs and radiation. Therefore, ceramidase inhibitors have excellent potential for development as new anticancer drugs. In this study, we identify a novel ceramidase inhibitor (Ceranib-1) by screening a small molecule library and describe the synthesis of a more potent analogue (Ceranib-2). In a cell-based assay, both compounds were found to inhibit cellular ceramidase activity toward an exogenous ceramide analogue, induce the accumulation of multiple ceramide species, decrease levels of sphingosine and S1P, inhibit the proliferation of cells alone and in combination with paclitaxel, and induce cell-cycle arrest and cell death. In vivo, Ceranib-2 was found to delay tumor growth in a syngeneic tumor model without hematologic suppression or overt signs of toxicity. These data support the selection of ceramidases as suitable targets for anticancer drug development and provide the first nonlipid inhibitors of human ceramidase activity.

Quinacrine synergizes with 5-fluorouracil and other therapies in colorectal cancer

Although treatments have improved patient prognosis in surgically resectable colorectal cancer, new effective drugs with improved safety profiles are needed to improve the currently poor outcomes of patients with recurrent or metastatic colorectal cancer. Quinacrine, a small molecule anti-malarial agent that has activity in giardiasis, lupus, prion disease, and used as a means of non-surgical sterilization, has shown cytotoxic activity across a broad range of cancers. Here, we evaluate the potential of adding quinacrine to anticancer chemotherapeutics and targeted agents as a potential novel combinatorial therapy for advanced colon cancer. We show that quinacrine synergizes with 5-fluorouracil and significantly enhances the cytotoxicity of sorafenib in a panel of 10 human colorectal cancer cell lines, including those with KRAS mutations protein gel blot analysis confirmed that quinacrine's anticancer activity partially arises from its ability to stabilize p53 and lower anti-apoptotic protein levels. In a series of in vivo studies, quinacrine monotherapy lowered the tumor load of nu/nu mice bearing human colorectal cancer xenografts. In combination, quinacrine and 5-Fluorouracil significantly delayed tumor growth of a variety of different xenografts, as compared to each agent administered alone. Our results suggest that the administration of quinacrine in combination with chemotherapeutic agents and targeted agents should be further explored in patients with recurrent, locally advanced, or metastatic colorectal cancer.

Quinacrine sensitizes hepatocellular carcinoma cells to TRAIL and chemotherapeutic agents

Quinacrine has been widely explored in treatment of malaria, giardiasis, and rheumatic diseases. We find that quinacrine stabilizes p53 and induces p53-dependent and independent cell death. Treatment by quinacrine alone at concentrations of 10-20 mM for 1-2 d cannot kill hepatocellular carcinoma cells, such as HepG2, Hep3B, Huh7, which are also resistant to TRAIL. However, quinacrine renders these cells sensitive to treatment by TRAIL. Co-treatment of these cells with quinacrine and TRAIL induces overwhelming cell death within 3-4 h. Levels of DR5, a pro-apoptotic death receptor of TRAIL, are increased upon treatment with quinacrine, while levels of Mcl-1, an anti-apoptotic member of the Bcl-2 family, are decreased. While the synergistic effect of quinacrine with TRAIL appears to be in part independent of p53, knockdown of p53 in HepG2 cells by siRNA results in more cell death after treatment by quinacrine and TRAIL. The mechanism by which quinacrine sensitizes hepatocellular carcinoma cells to TRAIL and chemotherapies, and the potential for clinical application currently are being further explored. Lastly, quinacrine synergizes with chemotherapeutics, such as adriamycin, 5-FU, etoposide, CPT11, sorafenib, and gemcitabine, in killing hepatocellular carcinoma cells in vitro and the drug enhances the activity of sorafenib to delay tumor growth in vivo.

White matter integrity and vulnerability to Alzheimer's disease: preliminary findings and future directions

Neuroimaging biomarkers that precede cognitive decline have the potential to aid early diagnosis of Alzheimer's disease (AD). A body of diffusion tensor imaging (DTI) work has demonstrated declines in white matter (WM) microstructure in AD and its typical prodromal state, amnestic mild cognitive impairment. The present review summarizes recent evidence suggesting that WM integrity declines are present in individuals at high AD-risk, prior to cognitive decline. The available data suggest that AD-risk is associated with WM integrity declines in a subset of tracts showing decline in symptomatic AD. Specifically, AD-risk has been associated with WM integrity declines in tracts that connect gray matter structures associated with memory function. These tracts include parahippocampal WM, the cingulum, the inferior fronto-occipital fasciculus, and the splenium of the corpus callosum. Preliminary evidence suggests that some AD-risk declines are characterized by increases of radial diffusivity, raising the possibility that a myelin-related pathology may contribute to AD onset. These findings justify future research aimed at a more complete understanding of the neurobiological bases of DTI-based declines in AD. With continued refinement of imaging methods, DTI holds promise as a method to aid identification of presymptomatic AD. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Hippocampal sclerosis in advanced age: clinical and pathological features

Hippocampal sclerosis is a relatively common neuropathological finding (∼10% of individuals over the age of 85 years) characterized by cell loss and gliosis in the hippocampus that is not explained by Alzheimer's disease. Hippocampal sclerosis pathology can be associated with different underlying causes, and we refer to hippocampal sclerosis in the aged brain as hippocampal sclerosis associated with ageing. Much remains unknown about hippocampal sclerosis associated with ageing. We combined three different large autopsy cohorts: University of Kentucky Alzheimer's Disease Centre, the Nun Study and the Georgia Centenarian Study to obtain a pool of 1110 patients, all of whom were evaluated neuropathologically at the University of Kentucky. We focused on the subset of cases with neuropathology-confirmed hippocampal sclerosis (n=106). For individuals aged≥95 years at death (n=179 in our sample), each year of life beyond the age of 95 years correlated with increased prevalence of hippocampal sclerosis pathology and decreased prevalence of 'definite' Alzheimer's disease pathology. Aberrant TAR DNA protein 43 immunohistochemistry was seen in 89.9% of hippocampal sclerosis positive patients compared with 9.7% of hippocampal sclerosis negative patients. TAR DNA protein 43 immunohistochemistry can be used to demonstrate that the disease is usually bilateral even when hippocampal sclerosis pathology is not obvious by haematoxylin and eosin stains. TAR DNA protein 43 immunohistochemistry was negative on brain sections from younger individuals (n=10) after hippocampectomy due to seizures, who had pathologically confirmed hippocampal sclerosis. There was no association between cases with hippocampal sclerosis associated with ageing and apolipoprotein E genotype. Age of death and clinical features of hippocampal sclerosis associated with ageing (with or without aberrant TAR DNA protein 43) were distinct from previously published cases of frontotemporal lobar degeneration TAR DNA protein 43. To help sharpen our ability to discriminate patients with hippocampal sclerosis associated with ageing clinically, the longitudinal cognitive profile of 43 patients with hippocampal sclerosis associated with ageing was compared with the profiles of 75 controls matched for age, gender, education level and apolipoprotein E genotype. These individuals were followed from intake assessment, with 8.2 (average) longitudinal cognitive assessments. A neuropsychological profile with relatively high-verbal fluency but low word list recall distinguished the hippocampal sclerosis associated with ageing group at intake (P<0.015) and also 5.5-6.5 years before death (P<0.005). This may provide a first step in clinical differentiation of hippocampal sclerosis associated with ageing versus pure Alzheimer's disease in their earliest stages. In summary, in the largest series of autopsy-verified patients with hippocampal sclerosis to date, we characterized the clinical and pathological features associated with hippocampal sclerosis associated with ageing.

2-Amino-4-methyl-5-phenylethyl substituted-7-N-benzyl-pyrrolo[2,3-d]pyrimidines as novel antitumor antimitotic agents that also reverse tumor resistance

Gangjee et al. recently reported a novel series of 2-amino-4-methyl-5-phenylethyl substituted-7-benzyl-pyrrolo[2,3-d]pyrimidines, some of which exhibited two digit nanomolar antitumor and antimitotic activity and were not subject to P-glycoprotein (Pgp) or multidrug resistance protein 1 (MRP1) mediated tumor resistance (unlike the Vinca alkaloids and taxanes). Some of these compounds, in addition to their antitumor activity, had the ability to reverse the Pgp-mediated resistance to clinically used antimitotic agents. This report consists of an attempt to optimize the various activities of the parent compounds by synthetic variations of the phenyl ring of the 5-phenylethyl side chain. The target compounds were synthesized via a nine-step synthesis involving a Sonogashira reaction. The substituted phenylacetylenes as coupling partners were in turn synthesized from unactivated aryl bromides or iodides. The target compounds exhibited moderate cytotoxicity against MCF-7 tumor cells. However, most of these compounds showed improved cytotoxicity against the resistant NCI/ADR and MCF-7/VP. This study afforded an analog which reversed both Pgp-mediated as well as MRP1-mediated resistance to clinically used antimitotic agents, along with its own antimitotic mediated antitumor activity. In addition, in the NCI-60 cell line panel one of the compounds inhibited the growth of MDA-MD-435 breast cancer cell line at submicromolar concentration.

Your idea and your university: issues in academic technology transfer

Research discoveries may lead to products for commercial development. A central consideration for the researcher is how involved she or he will be in the commercialization process. In some cases, a university out-licenses the intellectual property, whereas in other cases, the investigator may want to be involved in the development process and choose to start his or her own company to develop and possibly to manufacture and sell the product. Before undertaking such a challenge, however, the investigator-turned-entrepreneur must consider a variety of issues, including career goals, financial and time commitments, potential conflicts of interest and/or commitment, start-up funding, and his or her ability to run a company or step aside to allow business experts to make necessary decisions. This paper discusses some personal considerations in deciding to start a spinout company and provides information on some of the available government grants to assist you should you decide to undertake your product's commercial development. In particular, the Small Business Innovative Research and Small Business Technology Transfer programs of federal funding agencies often are the source of early funding for new biomedical companies.

Common variants at MS4A4/MS4A6E, CD2AP, CD33 and EPHA1 are associated with late-onset Alzheimer's disease

The Alzheimer Disease Genetics Consortium (ADGC) performed a genome-wide association study of late-onset Alzheimer disease using a three-stage design consisting of a discovery stage (stage 1) and two replication stages (stages 2 and 3). Both joint analysis and meta-analysis approaches were used. We obtained genome-wide significant results at MS4A4A (rs4938933; stages 1 and 2, meta-analysis P (P(M)) = 1.7 × 10(-9), joint analysis P (P(J)) = 1.7 × 10(-9); stages 1, 2 and 3, P(M) = 8.2 × 10(-12)), CD2AP (rs9349407; stages 1, 2 and 3, P(M) = 8.6 × 10(-9)), EPHA1 (rs11767557; stages 1, 2 and 3, P(M) = 6.0 × 10(-10)) and CD33 (rs3865444; stages 1, 2 and 3, P(M) = 1.6 × 10(-9)). We also replicated previous associations at CR1 (rs6701713; P(M) = 4.6 × 10(-10), P(J) = 5.2 × 10(-11)), CLU (rs1532278; P(M) = 8.3 × 10(-8), P(J) = 1.9 × 10(-8)), BIN1 (rs7561528; P(M) = 4.0 × 10(-14), P(J) = 5.2 × 10(-14)) and PICALM (rs561655; P(M) = 7.0 × 10(-11), P(J) = 1.0 × 10(-10)), but not at EXOC3L2, to late-onset Alzheimer's disease susceptibility.

Alzheimer's disease is not "brain aging": neuropathological, genetic, and epidemiological human studies

Human studies are reviewed concerning whether "aging"-related mechanisms contribute to Alzheimer's disease (AD) pathogenesis. AD is defined by specific neuropathology: neuritic amyloid plaques and neocortical neurofibrillary tangles. AD pathology is driven by genetic factors related not to aging per se, but instead to the amyloid precursor protein (APP). In contrast to genes involved in APP-related mechanisms, there is no firm connection between genes implicated in human "accelerated aging" diseases (progerias) and AD. The epidemiology of AD in advanced age is highly relevant but deceptively challenging to address given the low autopsy rates in most countries. In extreme old age, brain diseases other than AD approximate AD prevalence while the impact of AD pathology appears to peak by age 95 and decline thereafter. Many distinct brain diseases other than AD afflict older human brains and contribute to cognitive impairment. Additional prevalent pathologies include cerebrovascular disease and hippocampal sclerosis, both high-morbidity brain diseases that appear to peak in incidence later than AD chronologically. Because of these common brain diseases of extreme old age, the epidemiology differs between clinical "dementia" and the subset of dementia cases with AD pathology. Additional aging-associated mechanisms for cognitive decline such as diabetes and synapse loss have been linked to AD and these hypotheses are discussed. Criteria are proposed to define an "aging-linked" disease, and AD fails all of these criteria. In conclusion, it may be most fruitful to focus attention on specific pathways involved in AD rather than attributing it to an inevitable consequence of aging.

FLT-PET may not be a reliable indicator of therapeutic response in p53-null malignancy

FDG (18F-deoxy-glucose) is the current gold standard for PET imaging. FLT (3'-deoxy-3'-(18F-fluorothymidine), a PET imaging marker of proliferation, has been proposed as an alternative to FDG for the assessment of therapeutic response. We examined the therapeutic predictive value of FLT-PET and FDG-PET using CALU-6, a human, p53-null, non-small cell lung cancer cell line with comparison of combined targeted therapy, TRAIL and sorafenib, versus combined conventional chemotherapy, docetaxel and cisplatin. CALU-6 tumor-bearing nu/nu mice (n=46) were evaluated in 3 therapeutic trials measuring FLT and FDG prediction of tumor response at 72 h following initiation of daily combination therapy with targeted agents, TRAIL (200 µg i.v.) and sorafenib (30 mg/kg i.p.) and compared to conventional chemotherapeutics cisplatin (3 mg/kg i.p.) and docetaxel (7.5 mg/kg i.p.). PET imaging response was compared to morphological and histological indicators of therapeutic response, including decreased vascularity (in vivo AngioSense imaging and anti-CD31 staining), slowed tumor growth (caliper measurements), decreased cellular proliferation (Ki-67 staining) and increased apoptosis (TUNEL staining). Decreases in tumor accumulation of FLT (FLTMAX -30%, p=0.03) at 72 h post treatment were observed in response to TRAIL and sorafenib combination therapy resulting in smaller, less vascular, more apoptotic tumors. No similar reduction in tumor accumulation of FLT (FLTMAX -2%, p=0.67) was observed 72 h following initiation of cisplatin and docetaxel combination therapy, despite histological and morphological evidence of drug response. In contrast, tumor imaging with FDG did demonstrate a decrease in accumulation in both treatment groups, -21% (p=0.30) in response to cisplatin/docetaxel and -8% (p=0.59) in response to TRAIL/sorafenib, but did not reach statistical significance. FLT, but not FDG, is predictive of therapeutic response to the targeted regimen TRAIL/sorafenib. However, FLT-PET may not predict therapeutic response to DNA damaging agents in p53-null tumors, likely due to loss of cell cycle control of thymidine kinase 1 (TK1). Thus, tumor imaging response by FLT may be limited in human tumors without functional p53.

Preclinical AD Workgroup staging: pathological correlates and potential challenges

The National Institute on Aging Preclinical Alzheimer's disease Workgroup (PADW) has issued a preliminary report with recommendations for classifying preclinical Alzheimer's disease (pAD) according to 3 early disease stages. Here we examine the PADW recommendations in relation to neuropathological features in a large, consecutive series of cognitively intact elderly persons, autopsied within a year after cognitive testing (n = 126 cognitively intact patients with mean age 83.7 years at death). Subjects were grouped based on a hypothetical construct correlating pathological features with PADW stages. Many cognitively intact individuals were classifiable as pAD (53/126 or 43%), as expected based on epidemiological and biomarker studies. Of these, most (48%) were in "stage 3", which corresponds to amyloid pathology with early neurodegeneration. As with prior studies, our data indicate that the development of neocortical neurofibrillary tangles is the key pathological event that is not observed in pAD cases: Braak stages III or IV pathology are hence not truly a substrate for "intermediate likelihood" that cognitive impairment is due to Alzheimer's disease (AD). We also stress the importance of comorbid non-Alzheimer's disease brain pathologies (hippocampal sclerosis, neocortical alpha-synucleinopathy, cerebrovascular disease, and brains with hippocampal neurofibrillary tangles but no cortical amyloid plaques) that can contribute to the development of cognitive impairment, or which may serve as confounds in the application of the PADW recommendations. While the final recommendations from the PADW working group have not yet been released, this preliminary analysis provides a perspective on those recommendations from a neuropathological point of view.

Abstract 4097: Sorafenib sensitizes solid tumors to TRAIL or TRAIL receptor agonist antibodies

Solid carcinomas display considerable resistance to chemotherapeutic drugs and tumor cell apoptosis-inducing agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death. A phase III clinical trial with the multi-kinase inhibitor sorafenib (Nexavar) in Hepatoceullular carcinoma (HCC) was completed leading to the first FDA-approved drug therapy for liver cancer in 2007. Phase I/II trials have been completed with a fully-human anti-TRAIL death receptor 1 (DR4) agonist antibody (mapatumumab) in non small-cell lung carcinoma and non-Hodgkin's lymphoma and phase I trials with an anti-TRAIL-R2 (DR5) monoclonal antibody (lexatumumab) in advanced cancers. We hypothesized that sorafenib and TRAIL or sorafenib and TRAIL receptor agonist antibodies (mapatumumab or lexatumumab) may overcome resistance to apoptosis in a panel of TRAIL-resistant solid carcinoma cell lines. We observed that sorafenib induces apoptosis of HepG2 and Hep3B cells in a dose-dependent manner. In addition, sorafenib is a potent sensitizer of HCC cell lines to TRAIL. We have also found that single agent lexatumumab causes cell death in HepG2, Hep3B and SNU449 cells whereas mapatumumab does not. The combination of sorafenib with TRAIL or either TRAIL receptor agonist antibody enhances apoptosis in HCC cell lines. We found that in other solid tumor types including prostate, breast and colon cancer there is a synergistic interaction between sorafenib and TRAIL or TRAIL receptor agonist antibodies. Furthermore, these combinations prevent the growth of tumors in vivo. Sorafenib downregulates the expression of Mcl-1 protein, a member of the Bcl-2 family that has been previously found to be overexpressed in about 50% of HCC patient samples. Sorafenib was also found to inhibit Stat3 activation by Jak2 kinases. These findings suggest a molecular rationale for combining these agents in therapy of solid tumors in clinical trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4097. doi:10.1158/1538-7445.AM2011-4097

Targeting NFĸB mediated breast cancer chemoresistance through selective inhibition of sphingosine kinase-2

Resistance to chemotherapy remains a significant obstacle in the treatment of hormone- independent breast cancer. Recent evidence suggests that altered sphingolipid signaling through increased sphingosine kinase activity may be an important mediator of breast cancer drug resistance. Sphingosine kinase-1 (Sphk1) is a proposed key regulator of breast cancer tumorigenesis, proliferation and resistance. There is, however, conflicting data on the role of sphingosine kinase-2 (Sphk2) in cancer biology and resistance, with some suggesting that Sphk2 has an opposing role to that of Sphk1. Here, we studied the effects of the novel selective Sphk2 inhibitor, ABC294640 (3-(4-chlorophenyl)-adamantane-1-carboxylic acid (pyridin-4-ylmethyl) amide), on human breast cancer. ABC294640 blocked both viability and survival at low micromolar IC(50) concentrations in the endocrine therapy-resistant MDA-MB-231 and chemoresistant MCF-7TN-R cell systems. Treatment with the inhibitor significantly reduced proliferation, as seen in immunofluorescence staining of Ki-67 in vitro. Interestingly, pharmacological inhibition of Sphk2 induced apoptosis through the intrinsic programmed cell death pathway. Furthermore, ABC294640 also diminished NF-ĸB survival signaling, through decreased activation of the Ser536 phosphorylation site on the p65 subunit. Xenografts of MCF-7TN-R cells growing in immunocompromised mice were utilized to validate the therapeutic efficacy of the sphingosine kinase-2 inhibitor. Treatment with 50 mg of ABC294640/kg completely blocked tumor volume in this model. These results indicate that pharmacological inhibition of Sphk2 with the orally bioavailable selective inhibitor, ABC294640, has therapeutic potential in the treatment of chemo- and endocrine therapy- resistant breast cancer.

Antitumor activity of sphingosine kinase 2 inhibitor ABC294640 and sorafenib in hepatocellular carcinoma xenografts

The balance between the pro-apoptotic lipids ceramide and sphingosine and the pro-survival lipid sphingosine 1-phosphate (S1P) is termed the "sphingosine rheostat". Two isozymes, sphingosine kinase 1 and 2 (SK1 and SK2), are responsible for phosphorylation of pro-apoptotic sphingosine to form pro-survival S1P. We have previously reported the antitumor properties of an SK2 selective inhibitor, ABC294640, alone or in combination with the multikinase inhibitor sorafenib in mouse models of kidney carcinoma and pancreatic adenocarcinoma. Here we evaluated the combined antitumor effects of the aforementioned drug combination in two mouse models of hepatocellular carcinoma. Although combining the SK2 inhibitor, ABC294640, and sorafenib in vitro only afforded additive drug-drug effects, their combined antitumor properties in the mouse model bearing HepG2 cells mirrored effects previously observed in animals bearing kidney carcinoma and pancreatic adenocarcinoma cells. Combining ABC294640 and sorafenib led to a decrease in the levels of phosphorylated ERK in SK-HEP-1 cells, indicating that the antitumor effect of this drug combination is likely mediated through a suppression of the MAPK pathway in hepatocellular models. We also measured levels of S1P in the plasma of mice treated with two different doses of ABC294640 and sorafenib. We found decreases in the levels of S1P in plasma of mice treated daily with 100 mg/kg of ABC294640 for 5 weeks, and this decrease was not affected by co-administration of sorafenib. Taken together, these data support combining ABC294640 and sorafenib in clinical trials in HCC patients. Furthermore, monitoring levels of S1P may provide a pharmacodynamic marker of ABC294640 activity.

Experimental osteoarthritis in rats is attenuated by ABC294640, a selective inhibitor of sphingosine kinase-2

BACKGROUND/AIMS

Osteoarthritis (OA) is a progressive degenerative disease characterized by cartilage degradation and chondrocyte apoptosis, which may involve aberrant sphingolipid metabolism. ABC294640 is a compound that selectively inhibits sphingosine kinase-2, a key enzyme in the sphingolipid pathway. Our goal was to assess the pharmacological effects of ABC294640 in the monosodium iodoacetate (MIA) model of OA.

METHODS

MIA (3 mg) was injected into the right knee joint to induce osteoarthritis in rats. Subsequently, the rats were treated with vehicle, ABC294640 or tramadol over a 28-day period. To assess pain, incapacitance readings were obtained weekly. MIA-injected knee joints were evaluated for histological damage, cartilage degradation and chondrocyte apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling histochemistry).

RESULTS

The percent weight bearing in vehicle/MIA rats significantly (p < 0.01) decreased from 48.8 ±0.8 (day 0) to 41.9 ±2.9 (day 28). In contrast, these values in ABC294640-treated rats were virtually the same on days 0 and 28. Knee joint histology scores were less severe in ABC294640-treated rats. Cartilage proteoglycan staining was more prominent in ABC294640/MIA animals than in vehicle/MIA rats. The percentage of apoptotic chondrocytes was decreased from 39.5% (vehicle treatment) to 25.8% (ABC294640 treatment).

CONCLUSION

ABC294640 attenuated the knee joint histological damage and pain associated with MIA-induced OA in rats.

Another fractured neck of femur: do we need a lateral X-ray?

OBJECTIVE

This study aimed to define the role of the lateral X-ray in the assessment and treatment planning of proximal femoral fractures. Occult fractures were not included.

METHODS

Radiographs from 359 consecutive patients with proximal femoral fractures admitted to our emergency department over a 12 month period were divided into anteroposterior (AP) views and lateral views. Three blinded reviewers independently assessed the radiographs, first AP views alone then AP plus lateral views, noting the fracture classification for each radiograph. These assessments were then compared with the intra-operative diagnosis, which was used as the gold standard. A 2 × 2 contingency square table was created and Pearson's χ(2) test was used for statistical analysis.

RESULTS

The rate of correct classification by the reviewers was improved by the assessment of the lateral X-ray in addition to the AP view for intracapsular fractures (p<0.013) but not for extracapsular fractures (p=0.27). However, the only advantage obtained by assessing the lateral view in intracapsular fractures was the detection of displacement where the fracture appeared undisplaced on the initial AP view.

CONCLUSION

This study provides statistical evidence that one view is adequate and safe for the majority of hip fractures. The lateral radiograph should not be performed routinely in order to make considerable savings in money and time and to avoid unnecessary patient discomfort.

Functional response in ventral temporal cortex differentiates mild cognitive impairment from normal aging

This study sought to identify altered brain activation patterns in amnestic mild cognitive impairment (MCI) that could precede frank task impairment and neocortical atrophy. A high-accuracy lexical decision (LD) task was therefore employed. Both MCI and normal seniors (NS) groups completed the LD task while functional magnetic resonance imaging (fMRI) was performed. Accuracy on the LD task was high (> or =89% correct for both groups), and both groups activated a network of occipitotemporal regions and inferior frontal cortex. However, compared with the NS group, the MCI group showed reduced fMRI activation in these regions and increased activation in bilateral portions of anterior cingluate cortex. The results from a voxel-based morphometry analysis indicated that altered activations in the MCI group were not within regions of atrophy. Receiver operating characteristic curves demonstrated that reduced fMRI response in the left and right midfusiform gyri accurately discriminated MCI from NS. When activation magnitude in both fusiform gyri were included in a single logistic regression model, group classification accuracy was very high (area under the curve = 0.93). These results showed that a disrupted functional response in the ventral temporal lobe accurately distinguishes individuals with MCI from NS, a finding which may have implications for identifying seniors at risk for cognitive decline.

Antiestrogenic effects of the novel sphingosine kinase-2 inhibitor ABC294640

Alterations in sphingolipid metabolism have been shown to contribute to the development of endocrine resistance and breast cancer tumor survival. Sphingosine kinase (SK), in particular, is overexpressed in breast cancer and is a promising target for breast cancer drug development. In this study, we used the novel SK inhibitor ABC294640 as a tool to explore the relationship between SK and estrogen (E2) receptor (ER) signaling in breast cancer cells. Treatment with ABC294640 decreased E2-stimulated ERE-luciferase activity in both MCF-7 and ER-transfected HEK293 cells. Furthermore, the inhibitor reduced E2-mediated transcription of the ER-regulated genes progesterone receptor and SDF-1. Competitive receptor-binding assays revealed that ABC294640 binds in the antagonist ligand-binding domain of the ER, acting as a partial antagonist similar to tamoxifen. Finally, treatment with ABC294640 inhibited ER-positive breast cancer tumor formation in vivo. After 15 d of treatment with ABC294640, tumor volume was reduced by 68.4% (P < 0.05; n = 5) compared with control tumors, with no marked weight loss or illness. Taken together, these results provide strong evidence that this novel SK inhibitor, which had not previously been known to interact with E2 signaling pathways, has therapeutic potential in treating ER-positive breast cancer via inhibition of both SK and ER signaling.