Breast cancer is a heterogeneous disease for which effective treatment depends on correct categorization of its molecular subtype. For the last several decades this determination has relied on hormone receptor status for estrogen, progesterone and HER2. More recently, gene expression data have been generated that further stratify both receptor-positive and receptor-negative cancers. The fatty acid-activating enzyme, ACSL4, has been demonstrated to play a role in the malignant phenotype of a variety of cancers, including breast. This lipid metabolic enzyme is differentially expressed as a function of subtype in breast tumors, with highest expression observed in the mesenchymal (claudin low) and basal-like subtypes. Here we review data that support the potential of utilizing ACSL4 status as both a biomarker of molecular subtype and a predictor of response to a variety of targeted and non-targeted treatment regimens. Based on these findings, we suggest 3 expanded roles for ACSL4: 1. as a biomarker for classification of breast cancer subtypes; 2. as a predictor of sensitivity to hormone-based and certain other therapies; and 3. as a target for the development of new treatment modalities.

Dysregulation of fatty acid metabolism is recognized as a component of malignant transformation in many different cancers, including breast; yet the potential for targeting this pathway for prevention and/or treatment of cancer remains unrealized. Evidence indicates that proteins involved in both synthesis and oxidation of fatty acids play a pivotal role in the proliferation, migration and invasion of breast cancer cells. The following essay summarizes data implicating specific fatty acid metabolic enzymes in the genesis and progression of breast cancer, and further categorizes the relevance of specific metabolic pathways to individual intrinsic molecular subtypes of breast cancer. Based on mRNA expression data, the less aggressive luminal subtypes appear to rely on a balance between de novo fatty acid synthesis and oxidation as sources for both biomass and energy requirements, while basal-like, receptor negative subtypes overexpress genes involved in the utilization of exogenous fatty acids. With these differences in mind, treatments may need to be tailored to individual subtypes.

Treatment protocols for breast cancer depend predominantly on receptor status with respect to estrogen (estrogen receptor alpha), progesterone (progesterone receptor) and human epidermal growth factor [human epidermal growth factor receptor 2 (HER2)]. The presence of one or more of these receptors suggests that a treatment targeting these pathways might be effective, while the absence of, or in the case of HER2, lack of overexpression of, all of these receptors, termed triple negative breast cancer (TNBC), indicates a need for the more toxic chemotherapy. In an effort to develop targeted therapies for TNBC, it will be necessary to differentiate among specific TNBC subtypes. The subset of TNBC that expresses androgen receptor (AR) has been determined to express genes consistent with a luminal subtype and therefore may be amenable to therapies targeting either AR, itself, or other pathways typical of a luminal subtype. Recent investigations of the AR signal pathway within breast cancer lead to AR as a significant target for breast cancer therapy with several clinical trials currently in progress. The subclass of TNBC that lacks AR, which we have termed quadruple negative breast cancer (QNBC) currently lacks a defined targetable pathway. Unlike AR-positive TNBC, QNBC predominantly exhibits a basal-like molecular subtype. Several subtypes and related pathway proteins are preferentially expressed in QNBC that may serve as effective targets for treatment, such as ACSL4, SKP2 and EGFR. ACSL4 expression has been demonstrated to be inversely correlated with expression of hormone/growth factor receptors and may thus serve as a biomarker for QNBC as well as a target for therapy. In the following review we summarize some of the current efforts to develop alternatives to chemotherapy for TNBC and QNBC.

Increases in fatty acid metabolism have been demonstrated to promote the growth and survival of a variety of cancers, including prostate cancer (PCa). Here, we examine the expression and function of the fatty acid activating enzyme, long-chain fatty acyl-CoA synthetase 4 (ACSL4), in PCa. Ectopic expression of ACSL4 in ACSL4-negative PCa cells increases proliferation, migration and invasion, while ablation of ACSL4 in PCa cells expressing endogenous ACSL4 reduces cell proliferation, migration and invasion. The cell proliferative effects were observed both in vitro, as well as in vivo. Immunohistochemical analysis of human PCa tissue samples indicated ACSL4 expression is increased in malignant cells compared with adjacent benign epithelial cells, and particularly increased in castration-resistant PCa (CRPC) when compared with hormone naive PCa. In cell lines co-expressing both ACSL4 and AR, proliferation was independent of exogenous androgens, suggesting that ACSL4 expression may lead to CRPC. In support for this hypothesis, ectopic ACSL4 expression induced resistance to treatment with Casodex, via decrease in apoptosis. Our studies further indicate that ACSL4 upregulates distinct pathway proteins including p-AKT, LSD1 and β-catenin. These results suggest ACSL4 could serve as a biomarker and potential therapeutic target for CRPC.

You have accessJournal of UrologyProstate Cancer: Basic Research II1 Apr 2014MP31-04 ACSL4 IN PROSTATE CANCER GROWTH, INVASION AND HORMONAL RESISTANCE Xinyu Wu, Yirong Li, Xinxin Du, Qinghu Ren, Max X. Kong, Jinhua wang, LingHang Wang, Yang Yang, Valerio Zhang, David Zhang, Fei Ye, Garrett Daniels, Fangming Deng, Jianjun Wei, Jonathan Melamed, Marie E. Monaco, and Peng Lee Xinyu WuXinyu Wu More articles by this author , Yirong LiYirong Li More articles by this author , Xinxin DuXinxin Du More articles by this author , Qinghu RenQinghu Ren More articles by this author , Max X. KongMax X. Kong More articles by this author , Jinhua wang Jinhua wang More articles by this author , LingHang WangLingHang Wang More articles by this author , Yang YangYang Yang More articles by this author , Valerio ZhangValerio Zhang More articles by this author , David ZhangDavid Zhang More articles by this author , Fei YeFei Ye More articles by this author , Garrett DanielsGarrett Daniels More articles by this author , Fangming DengFangming Deng More articles by this author , Jianjun WeiJianjun Wei More articles by this author , Jonathan MelamedJonathan Melamed More articles by this author , Marie E. MonacoMarie E. Monaco More articles by this author , and Peng LeePeng Lee More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.913AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Previous studies have shown that the fatty acid biosynthetic enzymes are important in a variety of cancers including prostate cancer (PCa). However, the precise role played by dysregulated expression of lipid metabolic enzymes and altered lipid homeostasis in carcinogenesis remains to be established.The present study is to examine the role of the understudied lipid metabolic enzyme, long-chain fatty acyl-CoA synthetase 4 (ACSL4), in PCa. METHODS LNCaP, LNCaP-AI, PC3 and C4-2B cells were utilized to assess the consequences of either increased or decreased levels of ACSL4 expression in cell proliferation, migration, invasion and apoptosis. Signal network proteins targeted by ACSL4 were analyzed by proteomic pathway array analysis. The effect of ACSL4 on tumor growth was examined in nude mice tumor xenograft models. RESULTS Forced expression of ACSL4 in LNCaP cells promotes cell proliferation and invasion, while ACSL4 knockdown by siRNA in PCa cells including LNCaP-AI, C4-2B and PC3, reduces cell proliferation. These effects were observed in both the absence and presence of androgens and/or estrogens, hormone-free media, although to varying degrees. The growth enhancing effect of ACSL4 is confirmed in vivo using nude mice xenografts to compare the growth of LNCaP vector control with LNCaP-ACSL4 cells. Consistently, ACSL4 expression is increased in human PCa compared to benign epithelial cells. Meanwhile, there is a reciprocal inverse relationship between ACSL4 and the androgen receptor (AR), with decreased AR expression in LNCaP-ACSL4 compared to LNCaP cells and increased AR levels in LNCaP-AI cells with ACSL4 knockdown using siRNA. Conversely, ACSL4 levels are decreased in PC3 cells with AR overexpression. Interestingly, there is an un-coupling of the inverse relationship between AR and ACSL4 in LNCaP-AI cells. Consistently, ACSL4 is also increased in human castrate resistant prostate cancer. Importantly, ACSL4 expression induces resistance to Casodex as evidenced by flow and apoptosis assays. The resistance to Casodex is mediated by BAX and Caspase 8. CONCLUSIONS Our study indicates that ACSL4 expression may serve as a biomarker with potential utility in the diagnosis and treatment of PCa. © 2014FiguresReferencesRelatedDetails Volume 191 Issue 4S April 2014 Page: e324 Advertisement Copyright & Permissions© 2014Metrics Author Information Xinyu Wu More articles by this author Yirong Li More articles by this author Xinxin Du More articles by this author Qinghu Ren More articles by this author Max X. Kong More articles by this author Jinhua wang More articles by this author LingHang Wang More articles by this author Yang Yang More articles by this author Valerio Zhang More articles by this author David Zhang More articles by this author Fei Ye More articles by this author Garrett Daniels More articles by this author Fangming Deng More articles by this author Jianjun Wei More articles by this author Jonathan Melamed More articles by this author Marie E. Monaco More articles by this author Peng Lee More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

The malignant transformation of cells requires adaptations across multiple metabolic processes to satisfy the energy required for their increased rate of proliferation. Dysregulation of lipid metabolism has been a hallmark of the malignant phenotype; increased lipid accumulation secondary to changes in the levels of a variety of lipid metabolic enzymes has been documented in a variety of tumors, including prostate. Alterations in prostate lipid metabolism include upregulation of several lipogenic enzymes as well as of enzymes that function to oxidize fatty acids as an energy source. Cholesterol metabolism and phospholipid metabolism are also affected. With respect to lipogenesis, most studies have concentrated on increased expression and activity ofthe de novo fatty acid synthesis enzyme, fatty acid synthase (FASN), with suggestions that FASN might function as an oncogene. A central role for fatty acid oxidation in supplying energy to the prostate cancer cell is supported by the observation that the peroxisomal enzyme, α-methylacyl-CoA racemase (AMACR), which facilitates the transformation of branched chain fatty acids to a form suitable for β-oxidation, is highly overexpressed in prostate cancer compared with normal prostate. Exploitation of the alterations in lipid metabolic pathways in prostate cancer could result in the development of new therapeutic modalities as well as provide candidates for new prognostic and predictive biomarkers. AMACR has already proven to be a valuable biomarker in distinguishing normal from malignant prostate tissue, and is used routinely in clinical practice.

The purpose of this study was to determine the role of long-chain fatty acyl-CoA synthetase 4 (ACSL4) in breast cancer. Public databases were utilized to analyze the relationship between ACSL4 mRNA expression and the presence of steroid hormone and human epidermal growth factor receptor 2 (HER2) in both breast cancer cell lines and tissue samples. In addition, cell lines were utilized to assess the consequences of either increased or decreased levels of ACSL4 expression. Proliferation, migration, anchorage-independent growth and apoptosis were used as biological end points. Effects on mRNA expression and signal transduction pathways were also monitored. A meta-analysis of public gene expression databases indicated that ACSL4 expression is positively correlated with a unique subtype of triple negative breast cancer (TNBC), characterized by the absence of androgen receptor (AR) and therefore referred to as quadruple negative breast cancer (QNBC). Results of experiments in breast cancer cell lines suggest that simultaneous expression of ACSL4 and a receptor is associated with hormone resistance. Forced expression of ACSL4 in ACSL4-negative, estrogen receptor α (ER)-positive MCF-7 cells resulted in increased growth, invasion and anchorage independent growth, as well as a loss of dependence on estrogen that was accompanied by a reduction in the levels of steroid hormone receptors. Sensitivity to tamoxifen, triacsin C and etoposide was also attenuated. Similarly, when HER2-positive, ACSL4-negative, SKBr3 breast cancer cells were induced to express ACSL4, the proliferation rate increased and the apoptotic effect of lapatinib was reduced. The growth stimulatory effect of ACSL4 expression was also observed in vivo in nude mice when MCF-7 control and ACSL4-expressing cells were utilized to induce tumors. Our data strongly suggest that ACSL4 can serve as both a biomarker for, and mediator of, an aggressive breast cancer phenotype.

Lymphoid enhancer-binding factor (LEF)1 is a major mediator and a target in canonical Wnt/β-catenin pathway. Interactions between the androgen receptor (AR) and canonical Wnt pathways have been implicated in the development of the genitourinary organs. Here, we investigated the localization and role of LEF1-positive cells during development of the prostate gland in human and in the murine model. We show that during human prostate development, LEF1 is restricted to the basal epithelial layer of the urogenital sinus. During mouse development, Lef1 is also present in the urogenital mesenchyme in addition to the basal epithelial layer of the urogenital sinus. In the course of elongation and branching of the prostatic ducts, Lef1 is localized to the proliferating epithelium at the distal tips of the buds. Notably, during branching morphogenesis, domains of Lef1 and AR are mutually exclusive. We further employed the TOPGAL reporter strain to examine the dynamics of Wnt signaling in the context of prostate regression upon a 7-d treatment with a competitive AR inhibitor, bicalutamide. We found that Wnt/Lef1-positive basal cells are not dependent upon androgen for survival. Furthermore, upon bicalutamide treatment, Wnt/Lef1-positive basal progenitors repopulated the luminal compartment. We conclude that Wnt/Lef1 activity identifies an androgen-independent population of prostate progenitors, which is important for embryonic development and organ maintenance and regeneration in the adult.

: The goal of this project is to investigate the role of long chain fatty acyl-CoAsynthetase 4 (ACSL4) as a biomarker for, and mediator of an aggressive breast cancer phenotype. Results indicate that expression of ACSL4 in breast cell lines and tumor samples is inversely correlated with expression of estrogen receptor, progesterone receptor, androgen receptor and human epidermal growth factor receptor 2 (HER2). Breast cancer lacking all 4receptors (quadruple negative breast cancer (QNBC)) can be identified by ACSL4 expression status with a sensitivity of 78 and a specificity of 86 . In addition, in vitro data from experiments in breast cancer cell lines demonstrates that simultaneous expression of a receptor and ACSL4 is characterized by resistance to treatment with a receptor-based targeted therapy, such as tamoxifen or lapatinib. Forced expression of ACSL4 results in increased proliferation, migration and invasion. The effects are specific for ACSL4 in that neither a mutant ACSL4 lacking enzyme activity nor ACSL3 are effective. Messenger RNA and protein expression data indicate possible effectors of the action of ACSL4.

To assess changes in peroxisome proliferator-activated receptor-γ (PPARγ) in peripheral blood mononuclear cells (PBMC) from critically ill children with sepsis. Additionally, to investigate the effects of sepsis on the endogenous activator of PPARγ, 15-deoxy-∆12,14-PGJ2 (15d-PGJ2), and the downstream targets of PPARγ activity, adiponectin and resistin.

Previous studies have shown that key enzymes involved in lipid metabolic pathways are differentially expressed in normal compared with tumor tissues. However, the precise role played by dysregulated expression of lipid metabolic enzymes and altered lipid homeostasis in carcinogenesis remains to be established. Fatty acid synthase is overexpressed in a variety of cancers, including breast and prostate. The purpose of the present study was to examine the expression patterns of additional lipid metabolic enzymes in human breast and prostate cancers. This was accomplished by analysis of published expression databases, with confirmation by immunoblot assays. Our results indicate that the fatty acid-activating enzyme, long-chain fatty acyl-CoA synthetase 4 (ACSL4), is differentially expressed in human breast cancer as a function of estrogen receptor alpha (ER) status. In 10 separate studies, ACSL4 messenger RNA (mRNA) was overexpressed in ER-negative breast tumors. Of 50 breast cancer cell lines examined, 17 (89%) of 19 ER-positive lines were negative for ACSL4 mRNA expression and 20 (65%) of 31 ER-negative lines expressed ACSL4 mRNA. The inverse relationship between ER expression and ACSL4 expression was also observed for androgen receptor status in both breast and prostate cancers. Furthermore, loss of steroid hormone sensitivity, such as that observed in Raf1-transfected MCF-7 cells and LNCaP-AI cells, was associated with induction of ACSL4 expression. Ablation of ACSL4 expression inMDA-MB-231 breast cancer cells had no effect on cell proliferation; however, sensitivity to the cytotoxic effects of triacsin C was increased three-fold in the cells lacking ACSL4.

OBJECTIVE:To directly assess whether genomewide expression profiles derived from leukocyte subsets are comparable to that of whole blood as measured by enrichment for genes corresponding to metabolic and signaling pathways. DESIGN:Prospective observational study involving microarray-based bioinformatics based on RNA individually derived from whole blood, neutrophils, monocytes, and lymphocytes, respectively. SETTING:Three pediatric intensive care units in the United States. PATIENTS:Children < or =10 yrs of age: five normal control subjects and 13 meeting criteria for septic shock on day 1 of presentation to the pediatric intensive care unit. INTERVENTIONS:None other than standard care. MEASUREMENTS AND MAIN RESULTS:Baseline analyses using whole blood-derived RNA demonstrated increased expression of genes corresponding to signaling pathways involving innate immunity, redox balance, and protein ubiquitination and decreased expression of genes corresponding to the adaptive immune system. Subsequent analyses using leukocyte-specific RNA were congruent with the gene expression profiles demonstrated using whole blood-derived RNA as measured by enrichment for genes corresponding to metabolic and signaling pathways. Gene network analysis, derived from a composite gene list involving the individual gene expression profiles of neutrophils, monocytes, and lymphocytes, respectively, revealed a gene network corresponding to antigen presentation, cell-mediated immunity, and humoral-mediated immunity. Finally, a subanalysis focused on network gene nodes localized to the nuclear compartment revealed functional annotations related to transcriptional repression and epigenetic regulation. CONCLUSIONS:These data demonstrate that genome-level repression of adaptive immunity gene programs early in the course of pediatric septic shock remained evident when analyses were conducted using leukocyte subset-specific RNA.

Objectives: To advance our biological understanding of pediatric septic shock, we measured the genome-level expression profiles of critically ill children representing the systemic inflammatory response syndrome (SIRS), sepsis, and septic shock spectrum. Design: Prospective observational study involving microarray-based bioinformatics. Setting: Multiple pediatric intensive care units in the United States. Patients: Children ≤10 years of age: 18 normal controls, 22 meeting criteria for SIRS, 32 meeting criteria for sepsis, and 67 meeting criteria for septic shock on day 1. The available day 3 samples included 20 patients still meeting sepsis criteria, 39 patients still meeting septic shock criteria, and 24 patients meeting the exclusive day 3 category, SIRS resolved. Interventions: None other than standard care. Measurements and Main Results: Longitudinal analyses were focused on gene expression relative to control samples and patients having paired day 1 and day 3 samples. The longitudinal analysis focused on up-regulated genes revealed common patterns of up-regulated gene expression, primarily corresponding to inflammation and innate immunity, across all patient groups on day 1. These patterns of up-regulated gene expression persisted on day 3 in patients with septic shock, but not to the same degree in the other patient classes. The longitudinal analysis focused on down-regulated genes demonstrated gene repression corresponding to adaptive immunity-specific signaling pathways and was most prominent in patients with septic shock on days 1 and 3. Gene network analyses based on direct comparisons across the SIRS, sepsis, and septic shock spectrum, and all available patients in the database, demonstrated unique repression of gene networks in patients with septic shock corresponding to major histocompatibility complex antigen presentation. Finally, analyses focused on repression of genes corresponding to zinc-related biology demonstrated that this pattern of gene repression is unique to patients with septic shock. Conclusions: Although some common patterns of gene expression exist across the pediatric SIRS, sepsis, and septic shock spectrum, septic shock is particularly characterized by repression of genes corresponding to adaptive immunity and zinc-related biology.

BACKGROUND:Septic shock is a heterogeneous syndrome within which probably exist several biological subclasses. Discovery and identification of septic shock subclasses could provide the foundation for the design of more specifically targeted therapies. Herein we tested the hypothesis that pediatric septic shock subclasses can be discovered through genome-wide expression profiling.METHODS:Genome-wide expression profiling was conducted using whole blood-derived RNA from 98 children with septic shock, followed by a series of bioinformatic approaches targeted at subclass discovery and characterization.RESULTS:Three putative subclasses (subclasses A, B, and C) were initially identified based on an empiric, discovery-oriented expression filter and unsupervised hierarchical clustering. Statistical comparison of the three putative subclasses (analysis of variance, Bonferonni correction, P < 0.05) identified 6,934 differentially regulated genes. K-means clustering of these 6,934 genes generated 10 coordinately regulated gene clusters corresponding to multiple signaling and metabolic pathways, all of which were differentially regulated across the three subclasses. Leave one out cross-validation procedures indentified 100 genes having the strongest predictive values for subclass identification. Forty-four of these 100 genes corresponded to signaling pathways relevant to the adaptive immune system and glucocorticoid receptor signaling, the majority of which were repressed in subclass A patients. Subclass A patients were also characterized by repression of genes corresponding to zinc-related biology. Phenotypic analyses revealed that subclass A patients were younger, had a higher illness severity, and a higher mortality rate than patients in subclasses B and C.CONCLUSION:Genome-wide expression profiling can identify pediatric septic shock subclasses having clinically relevant phenotypes.

We previously generated genome-wide expression data (microarray) from children with septic shock having the potential to lead the field into novel areas of investigation. Herein we seek to validate our data through a bioinformatic approach centered on a validation patient cohort. Forty-two children with a clinical diagnosis of septic shock and 15 normal controls served as the training data set, while 30 separate children with septic shock and 14 separate normal controls served as the test data set. Class prediction modeling using the training data set and the previously reported genome-wide expression signature of pediatric septic shock correctly identified 95-100% of controls and septic shock patients in the test data set, depending on the class prediction algorithm and the gene selection method. Subjecting the test data set to an identical filtering strategy as that used for the training data set, demonstrated 75% concordance between the two gene lists. Subjecting the test data set to a purely statistical filtering strategy, with highly stringent correction for multiple comparisons, demonstrated <50% concordance with the previous gene filtering strategy. However, functional analysis of this statistics-based gene list demonstrated similar functional annotations and signaling pathways as that seen in the training data set. In particular, we validated that pediatric septic shock is characterized by large-scale repression of genes related to zinc homeostasis and lymphocyte function. These data demonstrate that the previously reported genome-wide expression signature of pediatric septic shock is applicable to a validation cohort of patients.

RATIONALE Interventional clinical trials involving children with septic shock would benefit from an efficient preenrollment stratification strategy. OBJECTIVES To test the predictive value of interleukin (IL)-8 for 28-day mortality in pediatric septic shock. METHODS A training data set (n = 40) identified a serum IL-8 of greater than 220 pg/ml as having a 75% sensitivity and specificity for predicting 28-day mortality. This cutoff was then subjected to a series of validation steps. MEASUREMENTS AND MAIN RESULTS Subjects were drawn from two large, independent pediatric septic shock databases. Prospective application of the IL-8 cutoff to validation data set 1 (n = 139) demonstrated 78% sensitivity and 64% specificity for 28-day mortality. A serum IL-8 level of 220 pg/ml or less, however, had a negative predictive value for 28-day mortality of 95% in validation data set 1, which was subsequently applied to an independently generated data set of children with septic shock (validation set 2, n = 193). A serum IL-8 level of 220 pg/ml or less had a negative predictive value for 28-day mortality of 94% when applied to validation set 2. CONCLUSIONS A serum IL-8 level of 220 pg/ml or less, obtained within 24 hours of admission, predicts a high likelihood of survival in children with septic shock. We propose that IL-8 can be used to exclude such patients from interventional clinical trials and ultimately derive a study population with a more favorable risk to benefit ratio when subjected to a study agent.

Objective:To validate serum neutrophil gelatinase-associated lipocalin (NGAL) as an early biomarker for acute kidney injury in critically ill children with septic shock. Design:Observational cohort study. Setting:Fifteen North American pediatric intensive care units (PICUs). Patients:A total of 143 critically ill children with systemic inflammatory response syndrome (SIRS) or septic shock and 25 healthy controls. Interventions:None. Measurements and Main Results:Serum NGAL was measured during the first 24 hrs of admission to the PICU. Acute kidney injury was defined as a blood urea nitrogen concentration >100 mg/dL, serum creatinine >2 mg/dL in the absence of preexisting renal disease, or the need for dialysis. There was a significant difference in serum NGAL between healthy children (median 80 ng/mL, interquartile ratio [IQR] 55.5–85.5 ng/mL), critically ill children with SIRS (median 107.5 ng/mL, IQR 89–178.5 ng/mL), and critically ill children with septic shock (median 302 ng/mL, IQR 151–570 ng/mL; p < .001). Acute kidney injury developed in 22 of 143 (15.4%) critically ill children. Serum NGAL was significantly increased in critically ill children with acute kidney injury (median 355 ng/mL, IQR 166–1322 ng/mL) compared with those without acute kidney injury (median 186 ng/mL, IQR 98–365 ng/mL; p = .009). Conclusions:Serum NGAL is a highly sensitive but nonspecific predictor of acute kidney injury in critically ill children with septic shock. Further validation of serum NGAL as a biomarker of acute kidney injury in this population is warranted.