A new Matrix Assisted Laser Desorption Ionization Imaging Mass Spectrometry (MALDI-IMS) method to spatially profile the location and distribution of multiple N-linked glycan species in tissues is described. Application of an endoglycosidase, peptide N-glycosidase F (PNGaseF), directly on tissues followed by incubation releases N-linked glycan species amenable to detection by MALDI-IMS. The method has been designed to simultaneously profile the multiple glycan species released from intracellular organelle and cell surface glycoproteins, while maintaining histopathology compatible preparation workflows. A recombinant PNGaseF enzyme was sprayed uniformly across mouse brain tissue slides, incubated for two hours, then sprayed with 2,5-dihydroxybenzoic acid matrix for MALDI-IMS analysis. Using this basic approach, global snapshots of major cellular N-linked glycoforms were detected, including their tissue localization and distribution, structure and relative abundance. Off-tissue extraction and modification of glycans from similarly processed tissues and further mass spectrometry or HPLC analysis was done to assign structural designations. MALDI-IMS has primarily been utilized to spatially profile proteins, lipids, drug and small molecule metabolites in tissues, but it has not been previously applied to N-linked glycan analysis. The translatable MALDI-IMS glycan profiling workflow described herein can readily be applied to any tissue type of interest. From a clinical diagnostics perspective, the ability to differentially profile N glycans and correlate their molecular expression to histopathological changes can offer new approaches to identifying novel disease related targets for biomarker and therapeutic applications.

The DEK proto-oncogene has been associated with human carcinogenesis-either as a fusion with the CAN nucleoporin protein or when transcriptionally upregulated. Mechanisms of intracellular DEK functions, however, have remained relatively unexplored. We have recently demonstrated that DEK expression is induced by the high-risk human papillomavirus (HPV) E7 protein in a manner which is dependent upon retinoblastoma protein function and have implicated DEK in the inhibition of cellular senescence. Additionally, overexpression of DEK resulted in significant life span extension of primary human keratinocytes. In order to determine whether DEK expression is required for cellular proliferation and/or survival, we monitored cellular responses to the knockdown of DEK in cancer and primary cells. The results indicate that DEK expression protects both HPV-positive cancer and primary human cells from apoptotic cell death. Cell death in response to DEK depletion was accompanied by increased protein stability and transcriptional activity of the p53 tumor suppressor and consequent upregulation of known p53 target genes such as p21 CIP and Bax. Consistent with a possible role for p53 in DEK-mediated cell death inhibition, the p53-negative human osteosarcoma cell line SAOS-2 was resistant to the knockdown of DEK. Finally, expression of a dominant negative p53 miniprotein inhibited DEK RNA interference-induced p53 transcriptional induction, as well as cell death, thus directly implicating p53 activation in the observed apoptotic phenotype. These findings suggest a novel role for DEK in cellular survival, involving the destabilization of p53 in a manner which is likely to contribute to human carcinogenesis.The human DEK proto-oncogene was originally identified as a fusion with the CAN nucleoporin protein in a subset of acute myeloid leukemia patients carrying the t(6;9) translocation (50). Since its discovery, DEK has also been found to be transcriptionally upregulated in a number of aggressive human tumors such as bladder carcinoma, hepatocellular carcinoma, glioblastoma, melanoma, and acute myeloid leukemia types that do not exhibit the above translocation (21,29,31,32,44). DEK is a potential target of chromosome 6p22 gains in retinoblastoma, as well as in bladder cancer, suggesting that DEK gain of function may provide a selective advantage for tumor development (15,20,41). Consistent with potential oncogenic DEK properties is the developmental regulation of DEK mRNA with high expression in immature retinal mouse cells and with induced levels of DEK expression in simian virus 40 (SV40) large T antigen-induced retinoblastomas (41). The latter finding may further support our previous results obtained with primary human keratinocytes, where upregulated expression of DEK in response to the SV40 T antigen-related high-risk human papillomavirus (HPV) E7 protein was dependent upon retinoblastoma protein function (59). Furthermore, our data indicated that both the replicative senescence of primary human foreskin keratinocytes (HFKs) and...

The human DEK proto-oncogene is a nucleic acid binding protein with suspected roles in human carcinogenesis, autoimmune disease, and viral infection. Intracellular DEK functions, however, are poorly understood. In papillomavirus-positive cervical cancer cells, downregulation of viral E6/E7 oncogene expression results in cellular senescence. We report here the specific repression of DEK message and protein levels in senescing human papillomavirus type 16-(HPV16-) and HPV18-positive cancer cell lines as well as in primary cells undergoing replicative senescence. Cervical cancer cell senescence was partially overcome by DEK overexpression, and DEK overexpression was sufficient for extending the life span of primary keratinocytes, supporting critical roles for this molecule as a senescence regulator. In order to determine whether DEK is a bona fide HPV oncogene target in primary cells, DEK expression was monitored in human keratinocytes transduced with HPV E6 and/or E7. The results identify high-risk HPV E7 as a positive DEK regulator, an activity that is not shared by low-risk HPV E7 protein. Experiments in mouse embryo fibroblasts recapitulated the observed E7-mediated DEK induction and demonstrated that both basal and E7-induced regulation of DEK expression are controlled by the retinoblastoma protein family. Taken together, our results suggest that DEK upregulation may be a common event in human carcinogenesis and may reflect its senescence inhibitory function.Papillomaviruses are a group of small DNA tumor viruses that induce various benign and malignant epithelial lesions in the infected host (24). Classification of the human papillomaviruses (HPVs) into high-risk versus low-risk types is based upon the likelihood that the associated lesions will progress to malignancy or remain benign. High-risk HPV infections are strongly associated with cervical cancer, causing 15% of female cancer mortality worldwide (13). Over 97% of cervical cancers contain high-risk HPV DNA and express the viral oncogenes E6 and E7. A link between HPV infection and carcinogenesis is further supported by the documented in vitro and in vivo immortalizing and transforming activities of the viral oncoproteins (3,21,39,40,56). Many interactions have been reported between high-risk HPV oncoproteins and host cellular factors, including the targeted degradation of p53 and transcriptional upregulation of telomerase by E6 as well as the interaction with and degradation of retinoblastoma family members by E7 (24).HPV DNA is maintained episomally in benign, precancerous lesions but is generally found integrated into the cellular genome in malignant carcinomas and cell lines derived from them (12, 42). Sustained expression of the immortalizing viral oncogenes and oftentimes the loss of the viral E2 open reading frame are important attributes of such cell lines. The papillomavirus E2 protein is a regulatory factor with multiple roles in the transcription and replication of the viral DNA. Loss of E2 protein expression is likely important in the progre...

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Glycosylated proteins account for a majority of the post-translation modifications of cell surface, secreted and circulating proteins. Within the tumor microenvironment, the presence of immune cells, extracellular matrix proteins, cell surface receptors and interactions between stroma and tumor cells are all processes mediated by glycan binding and recognition reactions. Changes in glycosylation during tumorigenesis are well documented to occur, and affect all of these associated adhesion and regulatory functions. A MALDI imaging mass spectrometry (MALDI-IMS) workflow for profiling N-linked glycan distributions in fresh/frozen tissues and formalin-fixed paraffin-embedded (FFPE) tissues has recently been developed. The key to the approach is the application of a molecular coating of peptide-N-glycosidase to tissues, an enzyme that cleaves asparagine-linked glycans from their protein carrier. The released N-linked glycans can then be analyzed by MALDI-IMS directly on tissue. Generally 40 or more individual glycan structures are routinely detected, and when combined with histopathology localizations, tumor specific glycans are readily grouped relative to non-tumor regions and other structural features. This technique is a recent development and new approach in glycobiology and mass spectrometry imaging research methodology, thus potential uses such as tumor-specific glycan biomarker panels and other applications are discussed.

Expressed prostatic secretions (EPS) are proximal fluids of the prostate that are increasingly being utilized as a clinical source for diagnostic and prognostic assays for prostate cancer (PCa). These fluids contain an abundant amount of microvesicles reflecting the secretory function of the prostate gland, and their protein composition remains poorly defined in relation to PCa. Using expressed prostatic secretions in urine (EPS-urine), exosome preparations were characterized by a shotgun proteomics procedure. In pooled EPS-urine exosome samples, ~900 proteins were detected. Many of these have not been previously observed in the soluble proteome of EPS generated by our labs or other related exosome proteomes. We performed systematic comparisons of our data against previously published, prostate-related proteomes and global annotation analyses to highlight functional processes within the proteome of EPS-urine derived exosomes. The acquired proteomic data has been deposited to the Tranche repository and will lay the foundation for more extensive investigations of PCa derived exosomes in the context of biomarker discovery and cancer biology.

Escape of prostate cancer (PCa) cells from ionizing radiation-induced (IR-induced) killing leads to disease progression and cancer relapse. The influence of sphingolipids, such as ceramide and its metabolite sphingosine 1-phosphate, on signal transduction pathways under cell stress is important to survival adaptation responses. In this study, we demonstrate that ceramide-deacylating enzyme acid ceramidase (AC) was preferentially upregulated in irradiated PCa cells. Radiation-induced AC gene transactivation by activator protein 1 (AP-1) binding on the proximal promoter was sensitive to inhibition of de novo ceramide biosynthesis, as demonstrated by promoter reporter and ChIP-qPCR analyses. Our data indicate that a protective feedback mechanism mitigates the apoptotic effect of IR-induced ceramide generation. We found that deregulation of c-Jun induced marked radiosensitization in vivo and in vitro, which was rescued by ectopic AC overexpression. AC overexpression in PCa clonogens that survived a fractionated 80-Gy IR course was associated with increased radioresistance and proliferation, suggesting a role for AC in radiotherapy failure and relapse. Immunohistochemical analysis of human PCa tissues revealed higher levels of AC after radiotherapy failure than those in therapy-naive PCa, prostatic intraepithelial neoplasia, or benign tissues. Addition of an AC inhibitor to an animal model of xenograft irradiation produced radiosensitization and prevention of relapse. These data indicate that AC is a potentially tractable target for adjuvant radiotherapy.

Nearly one half of patients with lupus develop glomerulonephritis (GN), which often leads to renal failure. Although nephritis is diagnosed by the presence of proteinuria, the pathology of nephritis can fall into one of five classes defined by different forms of tissue injury, and the mechanisms involved in pathogenesis are not completely understood. Glycosphingolipids are abundant in the kidney, have roles in many cellular functions, and were shown to be involved in other renal diseases. Here, we show dysfunctional glycosphingolipid metabolism in patients with lupus nephritis and MRL/lpr lupus mice. Specifically, we found that glucosylceramide (GlcCer) and lactosylceramide (LacCer) levels are significantly higher in the kidneys of nephritic MRL/lpr lupus mice than the kidneys of non-nephritic lupus mice or healthy controls. This elevation may be, in part, caused by altered transcriptional regulation and/or activity of LacCer synthase (GalT5) and neuraminidase 1, enzymes that mediate glycosphingolipid metabolism. We show increased neuraminidase 1 activity early during the progression of nephritis (before significant elevation of GlcCer and LacCer in the kidney). Elevated levels of urinary LacCer were detected before proteinuria in lupus mice. Notably, LacCer levels were higher in the urine and kidneys of patients with lupus and nephritis than patients with lupus without nephritis or healthy controls. Together, these results show early and significant dysfunction of the glycosphingolipid metabolic pathway in the kidneys of lupus mice and patients with lupus nephritis and suggest that molecules in this pathway may serve as early markers in lupus nephritis.