Automated next-generation profiling of genomic alterations in human cancers.

The lack of validated, distributed comprehensive genomic profiling assays for patients with cancer inhibits access to precision oncology treatment. To address this, we describe elio tissue complete, which has been FDA-cleared for examination of 505 cancer-related genes. Independent analyses of clinically and biologically relevant sequence changes across 170 clinical tumor samples using MSK-IMPACT, FoundationOne, and PCR-based methods reveals a positive percent agreement of >97%. We observe high concordance with whole-exome sequencing for evaluation of tumor mutational burden for 307 solid tumors (Pearson r = 0.95) and comparison of the elio tissue complete microsatellite instability detection approach with an independent PCR assay for 223 samples displays a positive percent agreement of 99%. Finally, evaluation of amplifications and translocations against DNA- and RNA-based approaches exhibits >98% negative percent agreement and positive percent agreement of 86% and 82%, respectively. These methods provide an approach for pan-solid tumor comprehensive genomic profiling with high analytical performance.

Targeting sphingosine kinase 1 (SK1) enhances oncogene-induced senescence through ceramide synthase 2 (CerS2)-mediated generation of very-long-chain ceramides.

Senescence is an antiproliferative mechanism that can suppress tumor development and can be induced by oncogenes such as genes of the Ras family. Although studies have implicated bioactive sphingolipids (SL) in senescence, the specific mechanisms remain unclear. Here, using MCF10A mammary epithelial cells, we demonstrate that oncogenic K-Ras (Kirsten rat sarcoma viral oncogene homolog) is sufficient to induce cell transformation as well as cell senescence-as revealed by increases in the percentage of cells in the G1 phase of the cell cycle, p21WAF1/Cip1/CDKN1A (p21) expression, and senescence-associated ß-galactosidase activity (SA-ß-gal). Furthermore, oncogenic K-Ras altered SL metabolism, with an increase of long-chain (LC) C18, C20 ceramides (Cer), and very-long-chain (VLC) C22:1, C24 Cer, and an increase of sphingosine kinase 1 (SK1) expression. Since Cer and sphingosine-1-phosphate have been shown to exert opposite effects on cellular senescence, we hypothesized that targeting SK1 could enhance oncogenic K-Ras-induced senescence. Indeed, SK1 downregulation or inhibition enhanced p21 expression and SA-ß-gal in cells expressing oncogenic K-Ras and impeded cell growth. Moreover, SK1 knockdown further increased LC and VLC Cer species (C18, C20, C22:1, C24, C24:1, C26:1), especially the ones increased by oncogenic K-Ras. Fumonisin B1 (FB1), an inhibitor of ceramide synthases (CerS), reduced p21 expression induced by oncogenic K-Ras both with and without SK1 knockdown. Functionally, FB1 reversed the growth defect induced by oncogenic K-Ras, confirming the importance of Cer generation in the senescent phenotype. More specifically, downregulation of CerS2 by siRNA blocked the increase of VLC Cer (C24, C24:1, and C26:1) induced by SK1 knockdown and phenocopied the effects of FB1 on p21 expression. Taken together, these data show that targeting SK1 is a potential therapeutic strategy in cancer, enhancing oncogene-induced senescence through an increase of VLC Cer downstream of CerS2.

Amyloidosis Masquerading as Alcohol-Related Cirrhosis.

Amyloidosis can affect multiple organs, and involvement of the heart is the most common cause of death. Signs and symptoms vary depending upon the organ system affected by amyloid. Liver involvement is often seen, but symptoms are usually mild and nonspecific in isolated hepatic amyloidosis. None of the laboratory markers and imaging is characteristic of this condition; therefore, diagnosis is often delayed. Tissue biopsy is required for definitive diagnosis. Herein, we report a case where the patient's symptoms had been attributed to alcohol-related cirrhosis; however, further workup ultimately led to a diagnosis of systemic amyloidosis with multi-organ involvement.

Spatial clusters and temporal trends of malignant melanoma mortality in Ecuador.

OBJECTIVE: The aim of this study is two fold. First, it describes the temporal trends of malignant melanoma mortality from 2000 to 2016 in Ecuador. Second, it analyzes the spatial clusters of high mortality rates due to malignant melanoma in the country, from 2011 to 2016. METHODS: This is an ecological study; we included all death certificates of malignant melanoma from the National Institute of Statistics and Census database in Ecuador from 2000 to 2016. We calculated crude mortality rates and age-standardized mortality rates, all rates are expressed as deaths per 100,000 population. In order to assess the trend of malignant melanoma rates, we obtained average annual percent changes through Joinpoint regression analysis. Spatial scan statistics were used to identify high-risk clusters and the spatial autocorrelation was evaluated through a global Moran index. RESULTS: In Ecuador, between 2000 and 2016, malignant melanoma caused a total of 958 deaths. Crude mortality rates increased significantly (annual percent change = 4.8%; 95% confidence interval: 2.6-7.0), the age-standardized mortality rate also increased (annual percent change: 2.9%; 95% confidence interval: 0.5-5.4). The most likely cluster included 19 cantons and the second most likely cluster included 10 cantons, located in the Highlands region. The Global Moran I index for the study period shows a positive spatial autocorrelation (0.32; p = 0.001). CONCLUSION: Mortality due to malignant melanoma in Ecuador significantly increased over the 17-year study period; the spatial analysis and spatial autocorrelation indicates the presence of high-risk occurrence clusters in the Highlands region of the country.

Overview of "Systematic Reviews" of the Built Environment's Effects on Mental Health.

Good mental health is related to mental and psychological well-being, and there is growing interest in the potential role of the built environment on mental health, yet the evidence base underpinning the direct or indirect effects of the built environment is not fully clear. The aim of this overview is to assess the effect of the built environment on mental health-related outcomes. Methods. This study provides an overview of published systematic reviews (SRs) that assess the effect of the built environment on mental health. We reported the overview according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Databases searched until November 2019 included the Cochrane Database of Systematic Reviews, EMBASE, MEDLINE (OVID 1946 to present), LILACS, and PsycINFO. Two authors independently selected reviews, extracted data, and assessed the methodological quality of included reviews using the Assessing Methodological Quality of Systematic Reviews-2 (AMSTAR-2). Results. In total, 357 records were identified from a structured search of five databases combined with the references of the included studies, and eleven SRs were included in the narrative synthesis. Outcomes included mental health and well-being, depression and stress, and psychological distress. According to AMSTAR-2 scores, the quality assessment of the included SRs was categorized as "high" in two SRs and as "critically low" in nine SRs. According to the conclusions of the SRs reported by the authors, only one SR reported a "beneficial" effect on mental health and well-being outcomes. Conclusion. There was insufficient evidence to make firm conclusions on the effects of built environment interventions on mental health outcomes (well-being, depression and stress, and psychological distress). The evidence collected reported high heterogeneity (outcomes and measures) and a moderate- to low-quality assessment among the included SRs.

Spatial patterns of leptospirosis in Ecuador, 2013-2018.

BACKGROUND: Leptospirosis is a zoonotic disease that is considered an important public health problem in tropical regions and the world's poorest countries. METHODS: In this ecological study, we included cases of leptospirosis reported in Ecuador from 2013 to 2018. Spatial autocorrelation was evaluated through the global Moran I index and spatial-temporal scan statistics were used to identify high-risk clusters. RESULTS: In Ecuador, the leptospirosis incidence rates decreased from 3.3 cases per 100 000 population in 2013 to 0.8 cases per 100 000 population in 2018. The global Moran I index for the study period showed a positive spatial autocorrelation (0.68; p=0.001). We identified three significant spatial-temporal clusters for a high occurrence of leptospirosis incidence located in cantons of the Coast and Amazon regions. CONCLUSIONS: The clusters identified could be targeted by policymakers and stakeholders in order to direct surveillance and understand the dynamics of the distribution of leptospirosis in Ecuador.

McGregor inguinal flap for coverage of large soft tissue losses due to high-voltage electrical burns in the upper limb: a retrospective study.

High-voltage electrical burns are potentially devastating and they are associated with significant morbidity and mortality. Due to vascular damage and progressive tissue necrosis produced by electrical burns, there is a large controversy regarding the ideal reconstructive technique for cutaneous coverage of severe lesions in the upper limb. This study aims to analyze our experience using the McGregor inguinal flap technique, for the coverage of large soft tissue losses produced by high-voltage electric burns in the upper limb. We performed a retrospective descriptive study with patients diagnosed with high-voltage electric burns, in which the McGregor inguinal flap technique was used to cover severe lesions in the upper limb. This study was performed at the department of Reconstructive Plastic Surgery and Burns of the Specialist Hospital Eugenio Espejo, from January 2016 to December 2017. The flap technique was performed on twelve patients, out of which, nine were males with a mean age of 33 years old. Furthermore, nine out of the twelve cases occurred as a result of accidents at work. The mean time elapsed between the lifting of the flap, closure of the donor area, and fixation of the flap to the affected area was 56 minutes (44-72 minutes). In the immediate postoperative period, three patients presented signs of infection in the surgical area. No total dehiscence, total necrosis, and/or hematoma were reported in all patients. The success limb salvage rate was 100%. In our experience, the McGregor inguinal flap technique presented a favorable postoperative evolution with complete closure of the lesions and a low rate of complications. Due to the limitations of this study, more studies are needed to prospectively evaluate this flap.

Spatial analysis of dengue, cysticercosis and Chagas disease mortality in Ecuador, 2011-2016.

Background: Neglected tropical diseases (NTDs) continue to be an important cause of disability and mortality in the poorest tropical and subtropical areas. Methods: This is an ecological study. We included all death certificates with dengue, cysticercosis and Chagas disease in Ecuador from 2011 to 2016. The spatial autocorrelation was evaluated by GeoDa software through the Global Moran's I index and the formation of clusters by the local index of spatial association. Results: The Global Moran's I index for the study period shows a positive spatial autocorrelation for dengue, cysticercosis and Chagas disease (0.25, p=0.001; 0.07, p=0.04; 0.45, p=0.001, respectively). Conclusions: The clusters identified as higher risk in the country could be targeted by policymakers to adequately develop strategies to strengthen health promotion policies that break the cycle of these diseases.

99mTc-MIBI Uptake in a Benign Thymic Cyst.

A 34-year-old man with end-stage renal failure status post rejection of a deceased donor kidney transplant presented with bone pain in the setting of elevated serum parathyroid hormone and calcium levels. A Tc-MIBI SPECT/CT was performed before planned subtotal parathyroidectomy. SPECT/CT imaging revealed a 1.9-cm anterior mediastinal lesion with radiotracer uptake on both the immediate and delayed images. Surgical pathology of the lesion showed a benign thymic cyst with no parathyroid component.

Trends and Spatial Patterns of Oral Cancer Mortality in Ecuador, 2001-2016.

The aims of this study were to describe the temporal trend of OC from 2001 to 2016 and to analyze the space and space-time clusters of high mortality due to OC in Ecuador from 2011 to 2016. Methods. The present study is a mixed ecological study; the time trends were obtained using a Joinpoint regression model, space-time scan statistics was used to identify high-risk clusters, and Global Moran I index was calculated. Results. In Ecuador, between 2001 and 2016, OC caused a total of 1,025 deaths. Crude mortality rates significantly increased, with an APC (annual percentage change) of 2.7% (p=0.009). The age-standardized mortality rate did not significantly increase (APC: 1.73%; p=0.08). The most likely cluster was detected in 2015, included 20 cantons. The second cluster included 38 cantons, in the years 2014 to 2016. The Global Moran I index for the study period showed a negative spatial autocorrelation (-0.067; p=0.37). Conclusion. Mortality due to OC in Ecuador significantly increased over the 16-year study period, the young groups being the most affected. Ecuadorian provinces present high variability in types of OC and cancer rates.

Trends and Spatial Patterns of Suicide Among Adolescent in Ecuador, 1997-2016.

BACKGROUND: Suicide is a global public health problem, ranking among the top 20 leading causes of mortality. OBJECTIVE: The aim of the present study is two-fold. Firstly, it describes the temporal trends of suicide in adolescents from 1997 to 2016 in Ecuador, allowing us to identify critical periods. Secondly, it analyzes the spatiotemporal clusters of high mortality rates and the spatial distribution due to suicide in the country, from 2011 to 2016. METHODS: This is an ecological study; we included all death certificates of suicide among adolescents in the 10 - 19 age groups both sex, from the National Institute of Statistics and Census (INEC) database in Ecuador from 1997 to 2016. In order to assess the trend of suicide rates, we obtained Annual Percentage Changes (APCs) and average Annual Percent Changes (AAPCs) through Joinpoint regression analysis. Space-time scan statistics were used to identify high-risk clusters, and the spatial autocorrelation was evaluated through global Moran index. RESULTS: Suicides at a national level increased from 165 deaths in 1997 to 286 deaths in 2016; rates increased from 12.7 to 23.3 per 100,000 population along with a significant increase of the trend at the national level (AAPC=3.7%; 95% CI: 2.1 to 5.2). We identified two significant spatial clusters for a high occurrence of suicide: the primary most likely cluster included 83 cantons (Risk Relative=2.28) while the second most likely cluster included 20 cantons (Risk Relative=1.74). The Global Moran I index for the study period showed a positive spatial autocorrelation (0.27; p = 0.001). CONCLUSION: Suicide rates in adolescents significantly increased over the 20-year study period; the spatial analysis indicates the presence of high occurrence clusters in the Amazon and Southern Highlands regions of the country. This growing phenomenon may be a reflection of the lack of policies and strategies focused on the adolescent's mental health at a national level, added to factors such as family dysfunction, school failure, vulnerable ethnic groups, and immigration patterns.

Oncogenic K-Ras regulates bioactive sphingolipids in a sphingosine kinase 1-dependent manner.

Sphingosine kinase 1 (SK1) is an important enzyme involved in the production of the bioactive lipid sphingosine 1-phosphate (S1P). SK1 is overexpressed in many forms of cancer, however, the contribution of SK1 to cancer progression is still unclear. One of the best characterized mutations found in several forms of human cancer is an activating point mutation in the Ras oncogene, which disrupts its GTPase activity and leads to stimulation of the MEK/ERK pathway. Because SK1 activity and subcellular localization have been shown to be regulated by ERK, we wished to investigate the effect of oncogenic Ras, a potent activator of the Raf/MEK/ERK pathway, on the activity of SK1 and sphingolipid metabolism. Using HEK293T cells transiently transfected with the K-RasG12V oncogene and both wild type and Sphk1(-/-) mouse embryonic fibroblasts stably infected with retroviral K-RasG12V, we found that K-RasG12V increases the production of S1P and decreases the production of ceramide in a SK1-dependent manner. In addition, we found that expression of the K-RasG12V oncogene leads to plasma membrane localization of SK1 and a reduction in cytosolic levels of SK1. This effect is likely mediated by the Raf/MEK/ERK pathway as constitutively active B-Raf or MEK1 are able to activate SK1, but constitutively active Akt1 is not. We believe this research has important implications for how sphingolipids may be contributing to oncogenic transformation and provide some of the first evidence for oncogenes inducing specific changes in sphingolipid metabolism through SK1 regulation.

Still benched on its way to the bedside: sphingosine kinase 1 as an emerging target in cancer chemotherapy.

For several decades, lipid biologists have investigated how sphingolipids contribute to physiology, cell biology, and cell fate. Foremost among these discoveries is the finding that the bioactive sphingolipids ceramide, sphingosine, and sphingosine-1-phosphate (S1P) have diverse and often opposing effects on cell fate. Interestingly, these bioactive sphingolipids can be interconverted by just a few enzymatic reactions. Therefore, much attention has been paid to the enzymes which govern these reactions with a disproportionate amount of focus on the enzyme sphingosine kinase 1 (SK1). Several studies have found that tissue expression of SK1 correlates with cancer stage, chemotherapy response, and tumor aggressiveness. In addition, overexpression of SK1 in multiple cancer cell lines increases their resistance to chemotherapy, promotes proliferation, allows for anchorage independent growth, and increases local angiogenesis. Inhibition of SK1 using either pharmacological inhibitors or by crossing SK1 null mice has shown promise in many xenograft models of cancer, as well as several genetic and chemically induced mouse models of carcinogenesis. Here, we review the majority of the evidence that suggests SK1 is a promising target for the prevention and/or treatment of various cancers. Also, we strongly advocate for further research into basic mechanisms of bioactive sphingolipid signaling, and an increased focus on the efficacy of SK inhibitors in non-xenograft models of cancer progression.

Sphingosine kinase-1 and sphingosine 1-phosphate receptor 2 mediate Bcr-Abl1 stability and drug resistance by modulation of protein phosphatase 2A.

The mechanisms by which sphingosine kinase-1 (SK-1)/sphingosine 1-phosphate (S1P) activation contributes to imatinib resistance in chronic myeloid leukemia (CML) are unknown. We show herein that increased SK-1/S1P enhances Bcr-Abl1 protein stability, through inhibition of its proteasomal degradation in imatinib-resistant K562/IMA-3 and LAMA-4/IMA human CML cells. In fact, Bcr-Abl1 stability was enhanced by ectopic SK-1 expression. Conversely, siRNA-mediated SK-1 knockdown in K562/IMA-3 cells, or its genetic loss in SK-1(-/-) MEFs, significantly reduced Bcr-Abl1 stability. Regulation of Bcr-Abl1 by SK-1/S1P was dependent on S1P receptor 2 (S1P2) signaling, which prevented Bcr-Abl1 dephosphorylation, and degradation via inhibition of PP2A. Molecular or pharmacologic interference with SK-1/S1P2 restored PP2A-dependent Bcr-Abl1 dephosphorylation, and enhanced imatinib- or nilotinib-induced growth inhibition in primary CD34(+) mononuclear cells obtained from chronic phase and blast crisis CML patients, K562/IMA-3 or LAMA4/IMA cells, and 32Dcl3 murine progenitor cells, expressing the wild-type or mutant (Y253H or T315I) Bcr-Abl1 in situ. Accordingly, impaired SK-1/S1P2 signaling enhanced the growth-inhibitory effects of nilotinib against 32D/T315I-Bcr-Abl1-derived mouse allografts. Since SK-1/S1P/S1P2 signaling regulates Bcr-Abl1 stability via modulation of PP2A, inhibition of SK-1/S1P2 axis represents a novel approach to target wild-type- or mutant-Bcr-Abl1 thereby overcoming drug resistance.

Regulation of CC ligand 5/RANTES by acid sphingomyelinase and acid ceramidase.

Acid sphingomyelinase (aSMase) generates the bioactive lipid ceramide (Cer) from hydrolysis of sphingomyelin (SM). However, its precise roles in regulating specific sphingolipid-mediated biological processes remain ill defined. Interestingly, the aSMase gene gives rise to two distinct enzymes, lysosomal sphingomyelinase (L-SMase) and secretory sphingomyelinase (S-SMase) via alternative trafficking of a shared protein precursor. Previously, our laboratory identified Ser(508) as a crucial residue for the constitutive and regulated secretion of S-SMase in response to inflammatory cytokines, and demonstrated a role for S-SMase in formation of select cellular Cer species (Jenkins, R. W., Canals, D., Idkowiak-Baldys, J., Simbari, F., Roddy, P., Perry, D. M., Kitatani, K., Luberto, C., and Hannun, Y. A. (2010) J. Biol. Chem. 285, 35706-35718). In the present study using a chemokine/cytokine screen, we identified the chemokine CCL5 (formerly known as RANTES) as a candidate-specific downstream target for aSMase. Regulation of CCL5 by aSMase was subsequently validated using both loss-of-function and gain-of-function models indicating that aSMase is both necessary and sufficient for CCL5 production. Interestingly, cells deficient in acid ceramidase (aCDase) also exhibited defects in CCL5 induction, whereas cells deficient in sphingosine kinase-1 and -2 exhibited higher levels of CCL5, suggesting that sphingosine and not sphingosine 1-phosphate (S1P) is responsible for the positive signal to CCL5. Consistent with this, co-expression of aSMase and aCDase was sufficient to strongly induce CCL5. Taken together, these data identify a novel role for aSMase (particularly S-SMase) in chemokine elaboration by pro-inflammatory cytokines and highlight a novel and shared function for aSMase and aCDase.

An overview of sphingolipid metabolism: from synthesis to breakdown.

Sphingolipids constitute a class of lipids defined by their eighteen carbon amino-alcohol backbones which are synthesized in the ER from nonsphingolipid precursors. Modification of this basic structure is what gives rise to the vast family of sphingolipids that play significant roles in membrane biology and provide many bioactive metabolites that regulate cell function. Despite the diversity of structure and function of sphingolipids, their creation and destruction are governed by common synthetic and catabolic pathways. In this regard, sphingolipid metabolism can be imagined as an array of interconnected networks that diverge from a single common entry point and converge into a single common breakdown pathway. In their simplest forms, sphingosine, phytosphingosine and dihydrosphingosine serve as the backbones upon which further complexity is achieved. For example, phosphorylation of the C1 hydroxyl group yields the final breakdown products and/or the important signaling molecules sphingosine-1-phosphate, phytosphingosine-1-phosphate and dihydrosphingosine-1-phosphate, respectively. On the other hand, acylation of sphingosine, phytosphingosine, or dihydrosphingosine with one of several possible acyl CoA molecules through the action of distinct ceramide synthases produces the molecules defined as ceramide, phytoceramide, or dihydroceramide. Ceramide, due to the differing acyl CoAs that can be used to produce it, is technically a class of molecules rather than a single molecule and therefore may have different biological functions depending on the acyl chain it is composed of. At the apex of complexity is the group of lipids known as glycosphingolipids (GSL) which contain dozens of different sphingolipid species differing by both the order and type of sugar residues attached to their headgroups. Since these molecules are produced from ceramide precursors, they too may have differences in their acyl chain composition, revealing an additional layer of variation. The glycosphingolipids are divided broadly into two categories: glucosphingolipids and galactosphingolipids. The glucosphingolipids depend initially on the enzyme glucosylceramide synthase (GCS) which attaches glucose as the first residue to the C1 hydroxyl position. Galactosphingolipids, on the other hand, are generated from galactosylceramide synthase (GalCerS), an evolutionarily dissimilar enzyme from GCS. Glycosphingolipids are further divided based upon further modification by various glycosyltransferases which increases the potential variation in lipid species by several fold. Far more abundant are the sphingomyelin species which are produced in parallel with glycosphingolipids, however they are defined by a phosphocholine headgroup rather than the addition of sugar residues. Although sphingomyelin species all share a common headgroup, they too are produced from a variety of ceramide species and therefore can have differing acyl chains attached to their C-2 amino groups. Whether or not the differing acyl chain lengths in SMs dictate unique functions or important biophysical distinctions has not yet been established. Understanding the function of all the existing glycosphingolipids and sphingomyelin species will be a major undertaking in the future since the tools to study and measure these species are only beginning to be developed (see Fig 1 for an illustrated depiction of the various sphingolipid structures). The simple sphingolipids serve both as the precursors and the breakdown products of the more complex ones. Importantly, in recent decades, these simple sphingolipids have gained attention for having significant signaling and regulatory roles within cells. In addition, many tools have emerged to measure the levels of simple sphingolipids and therefore have become the focus of even more intense study in recent years. With this thought in mind, this chapter will pay tribute to the complex sphingolipids, but focus on the regulation of simple sphingolipid metabolism.

Role of sphingosine kinase-1 in paracrine/transcellular angiogenesis and lymphangiogenesis in vitro.

Sphingosine-1-phosphate (S1P) is an important bioactive sphingolipid involved in angiogenesis and lymphangiogenesis, 2 important processes that influence the growth, survival, and spread of tumors. S1P acts as an extracellular mediator through binding to 5 highly specific S1P receptors, S1P(1-5). Sphingosine kinase-1 (SK1), one of 2 known sphingosine kinase enzymes responsible for S1P production, appears to be overexpressed in many tumors. Although a role for S1P in angiogenesis and lymphangiogenesis has been established, it is unclear whether S1P secreted from cancer cells has a paracrine function in a tumor environment. Here we investigated whether modulation of cellular SK1 could initiate a paracrine angiogenic and lymphangiogenic switch. We found that SK1 overexpression in HEK cells or its down-regulation in glioma or breast cancer cells modulated extracellular S1P levels accordingly, which in turn increased or decreased both migration and tube formation in cocultured vascular or lymphatic endothelial cells. In contrast, down-regulation of sphingosine kinase 2 in both glioma and breast cancer cells had no appreciable effect on cellular or secreted S1P levels. In addition, vascular endothelial growth factors VEGF and VEGF-C down-regulation in cancer cells appeared insufficient to block the angiogenic and lymphangiogenic switch triggered by these cells. Moreover, S1P initiated endothelial cell sprouting in 3-dimensional collagen matrices, which is representative of a multistep angiogenic process. Our data collectively demonstrate for the first time that SK1 plays an essential role in regulating in vitro paracrine angiogenesis and lymphangiogenesis.

Acid ceramidase upregulation in prostate cancer cells confers resistance to radiation: AC inhibition, a potential radiosensitizer.

Radiation resistance in a subset of prostate tumors remains a challenge to prostate cancer radiotherapy. The current study on the effects of radiation on prostate cancer cells reveals that radiation programs an unpredicted resistance mechanism by upregulating acid ceramidase (AC). Irradiated cells demonstrated limited changes of ceramide levels while elevating levels of sphingosine and sphingosine-1-phosphate. By genetically downregulating AC with small interfering RNA (siRNA), we observed radiosensitization of cells using clonogenic and cytotoxicity assays. Conversely, AC overexpression further decreased sensitivity to radiation. We also observed that radiation-induced AC upregulation was sufficient to create cross-resistance to chemotherapy as demonstrated by decreased sensitivity to Taxol and C(6) ceramide compared to controls. Lower levels of caspase 3/7 activity were detected in cells pretreated with radiation, also indicating increased resistance. Finally, utilization of the small molecule AC inhibitor, LCL385, sensitized PPC-1 cells to radiation and significantly decreased tumor xenograft growth. These data suggest a new mechanism of cancer cell resistance to radiation, through upregulation of AC that is, in part, mediated by application of the therapy itself. An improved understanding of radiotherapy and the application of combination therapy achieved in this study offer new opportunities for the modulation of radiation effects in the treatment of cancer.