Michael Khan

Suppression of Myc-Induced Apoptosis in β Cells Exposes Multiple Oncogenic Properties of Myc and Triggers Carcinogenic Progression

To explore the role of c-Myc in carcinogenesis, we have developed a reversible transgenic model of pancreatic beta cell oncogenesis using a switchable form of the c-Myc protein. Activation of c-Myc in adult, mature beta cells induces uniform beta cell proliferation but is accompanied by overwhelming apoptosis that rapidly erodes beta cell mass. Thus, the oncogenic potential of c-Myc in beta cells is masked by apoptosis. Upon suppression of c-Myc-induced beta cell apoptosis by coexpression of Bcl-x(L), c-Myc triggers rapid and uniform progression into angiogenic, invasive tumors. Subsequent c-Myc deactivation induces rapid regression associated with vascular degeneration and beta cell apoptosis. Our data indicate that highly complex neoplastic lesions can be both induced and maintained in vivo by a simple combination of two interlocking molecular lesions.

Reversible Activation of c-Myc in Skin: Induction of a Complex Neoplastic Phenotype by a Single Oncogenic Lesion

The protooncogene c-myc regulates cell growth, differentiation, and apoptosis, and its aberrant expression is frequently observed in human cancer. However, the consequences of activating c-Myc in an adult tissue, in which these cellular processes are part of normal homeostasis, remain unknown. In order to achieve this, we have targeted expression of a switchable form of the c-Myc protein to the skin epidermis, a well characterized homeostatic tissue. We show that activation of c-MycER in adult suprabasal epidermis rapidly triggers proliferation and disrupts differentiation of postmitotic keratinocytes. Sustained activation of c-Myc is sufficient to induce papillomatosis together with angiogenesis--changes that resemble hyperplastic actinic keratosis, a commonly observed human precancerous epithelial lesion. All these premalignant changes spontaneously regress upon deactivation of c-MycER.

First-in-Human Phase I Study of the Liposomal RNA Interference Therapeutic Atu027 in Patients With Advanced Solid Tumors

PURPOSE Atu027 is a novel liposomal RNA interference therapeutic that includes a short-interfering RNA (siRNA), which silences expression of protein kinase N3 in the vascular endothelium. Atu027 has previously been shown to inhibit local tumor invasion as well as lymph node and pulmonary metastasis in mouse cancer models. This first-in-human study aimed to assess the safety, tolerability, and pharmacokinetics of Atu027 while evaluating therapeutic effects on both primary tumors and metastatic lesions. PATIENTS AND METHODS Thirty-four patients with advanced solid tumors received 10 escalating doses of Atu027 without premedication, as one single followed by eight intravenous infusions twice per week during a 28-day cycle. Response was monitored by computed tomography/magnetic resonance imaging at baseline, at the end of treatment (EoT), and at final follow-up (EoS), and was assessed according to RECIST. RESULTS Atu027 was well tolerated up to dose levels of 0.336 mg/kg; most adverse events (AEs) were low-grade toxicities (grade 1 or 2). No maximum tolerated dose was reached. Plasma levels of siRNA strands and lipids were dose proportional, peaking during 4-hour infusion. Disease stabilization was achieved in 41% of patients at EoT (n = 14 of 34 treated patients); eight patients had stable disease at EoS, and some experienced complete or partial regression of metastases. sFLT1 (soluble variant of vascular endothelial growth factor receptor-1) decreased from pretreatment levels in most patients after dose levels 04 to 10. CONCLUSION Atu027 was safe in patients with advanced solid tumors, with 41% of patients having stable disease for at least 8 weeks. In view of these results, further clinical trials have been initiated, and sFLT1 will be investigated as a potential biomarker.

Brief inactivation of c-Myc is not sufficient for sustained regression of c-Myc-induced tumours of pancreatic islets and skin epidermis

BackgroundTumour regression observed in many conditional mouse models following oncogene inactivation provides the impetus to develop, and a platform to preclinically evaluate, novel therapeutics to inactivate specific oncogenes. Inactivating single oncogenes, such as c-Myc, can reverse even advanced tumours. Intriguingly, transient c-Myc inactivation proved sufficient for sustained osteosarcoma regression; the resulting osteocyte differentiation potentially explaining loss of c-Mycs oncogenic properties. But would this apply to other tumours?ResultsWe show that brief inactivation of c-Myc does not sustain tumour regression in two distinct tissue types; tumour cells in pancreatic islets and skin epidermis continue to avoid apoptosis after c-Myc reactivation, by virtue of Bcl-xL over-expression or a favourable microenvironment, respectively. Moreover, tumours progress despite reacquiring a differentiated phenotype and partial loss of vasculature during c-Myc inactivation. Interestingly, reactivating c-Myc in β-cell tumours appears to result not only in further growth of the tumour, but also re-expansion of the accompanying angiogenesis and more pronounced β-cell invasion (adenocarcinoma).ConclusionsGiven that transient c-Myc inactivation could under some circumstances produce sustained tumour regression, the possible application of this potentially less toxic strategy in treating other tumours has been suggested. We show that brief inactivation of c-Myc fails to sustain tumour regression in two distinct models of tumourigenesis: pancreatic islets and skin epidermis. These findings challenge the potential for cancer therapies aimed at transient oncogene inactivation, at least under those circumstances where tumour cell differentiation and alteration of epigenetic context fail to reinstate apoptosis. Together, these results suggest that treatment schedules will need to be informed by knowledge of the molecular basis and environmental context of any given cancer.

WHIDE--a web tool for visual data mining colocation patterns in multivariate bioimages.

Motivation: Bioimaging techniques rapidly develop toward higher resolution and dimension. The increase in dimension is achieved by different techniques such as multitag fluorescence imaging, Matrix Assisted Laser Desorption / Ionization (MALDI) imaging or Raman imaging, which record for each pixel an N-dimensional intensity array, representing local abundances of molecules, residues or interaction patterns. The analysis of such multivariate bioimages (MBIs) calls for new approaches to support users in the analysis of both feature domains: space (i.e. sample morphology) and molecular colocation or interaction. In this article, we present our approach WHIDE (Web-based Hyperbolic Image Data Explorer) that combines principles from computational learning, dimension reduction and visualization in a free web application. Results: We applied WHIDE to a set of MBI recorded using the multitag fluorescence imaging Toponome Imaging System. The MBI show field of view in tissue sections from a colon cancer study and we compare tissue from normal/healthy colon with tissue classified as tumor. Our results show, that WHIDE efficiently reduces the complexity of the data by mapping each of the pixels to a cluster, referred to as Molecular Co-Expression Phenotypes and provides a structural basis for a sophisticated multimodal visualization, which combines topology preserving pseudocoloring with information visualization. The wide range of WHIDEs applicability is demonstrated with examples from toponome imaging, high content screens and MALDI imaging (shown in the Supplementary Material). Availability and implementation: The WHIDE tool can be accessed via the BioIMAX website http://ani.cebitec.uni-bielefeld.de/BioIMAX/; Login: whidetestuser; Password: whidetest. Supplementary information: Supplementary data are available at Bioinformatics online. Contact: tim.nattkemper@uni-bielefeld.de

15-lipoxygenase-1 in colorectal cancer: a review.

Objective: Enzymes involved in the oxidative metabolism of n-6 polyunsaturated fatty acids, like lipoxygenase (LOX) and cyclooxygenase (COX), are significant in the pathogenesis of colorectal cancer. Of these enzymes, 15-LOX-1 is expressed in colon. Aim of this article is to describe the role and regulation of 15-LOX-1 in colorectal cancer and highlight its importance in cancer therapeutics. Methods: For our electronic literature research in PubMed and MEDLINE, key words related to 15-LOX-1 and colorectal cancer were used to find articles for this review. Results: From the evidences, we believe that 15-LOX-1 has anti-carcinogenic effects in colorectal cancer, dependent or independent of its metabolites, and is manifested through downstream pathways involving cGMP, PPAR, p53, p21 and NAG-1, increasing apoptosis and decreasing proliferation in cancer cells. Regulation of 15-LOX-1 expression is achieved at transcription level by global histone acetylation and may also be dependent on GATA-6, IL-4 and IL-13. Positive relationship exists between 15-LOX-1 and survival in colorectal cancer. Conclusion: Evidences strongly support that therapeutic modulation of 15-LOX-1 may be a key to the treatment of colorectal cancer. However, it is still undecided whether the up-regulation of 15-LOX-1 alone can be sufficient to treat colorectal cancer and further studies are awaited.

Local isotropic phase symmetry measure for detection of beta cells and lymphocytes

Diabetes can be associated with a reduction in functional β cell mass, which must be restored if the disease is to be cured or progress is to be arrested. To study the cell count, it is also necessary to determine the number of nuclei within the insulin stained area. It can take a single experimentalist several months to complete a single study of this kind, results of which may still be quite subjective. In this paper, we propose a framework based on a novel measure of local symmetry for detection of cells. The local isotropic phase symmetry measure (LIPSyM) is designed to give high values at or near the cell centers. We demonstrate the effectiveness of our algorithm for detection of two types of specific cells in histology images, cells in mouse pancreatic sections and lymphocytes in human breast tissue. Experimental results for these two problems show that our algorithm performs better than human experts for the former problem, and outperforms the best reported results for the latter.

Toponome imaging system in situ protein network mapping in normal and cancerous colon from the same patient reveals more than five-thousand cancer specific protein clusters and their subcellular annotation by using a three symbol code

In a proof of principle study, we have applied an automated fluorescence toponome imaging system (TIS) to examine whether TIS can find protein network structures, distinguishing cancerous from normal colon tissue present in a surgical sample from the same patient. By using a three symbol code and a power of combinatorial molecular discrimination (PCMD) of 2(21) per subcellular data point in one single tissue section, we demonstrate an in situ protein network structure, visualized as a mosaic of 6813 protein clusters (combinatorial molecular phenotype or CMPs), in the cancerous part of the colon. By contrast, in the histologically normal colon, TIS identifies nearly 5 times the number of protein clusters as compared to the cancerous part (32 009). By subcellular visualization procedures, we found that many cell surface membrane molecules were closely associated with the cell cytoskeleton as unique CMPs in the normal part of the colon, while the same molecules were disassembled in the cancerous part, suggesting the presence of dysfunctional cytoskeleton-membrane complexes. As expected, glandular and stromal cell signatures were found, but interestingly also found were potentially TIS signatures identifying a very restricted subset of cells expressing several putative stem cell markers, all restricted to the cancerous tissue. The detection of these signatures is based on the extreme searching depth, high degree of dimensionality, and subcellular resolution capacity of TIS. These findings provide the technological rationale for the feasibility of a complete colon cancer toponome to be established by massive parallel high throughput/high content TIS mapping.

Lipoprotein lipase gene variants relate to presence and degree of microalbuminuria in Type II diabetes.

AbstractAims/hypothesis. Lipids and lipoproteins, particularly triglyceride rich lipoproteins, could influence the development and progression of microalbuminuria in diabetes. Lipoprotein lipase gene variants have been found to correlate with lipid/lipoprotein concentrations, especially hypertriglyceridaemia. We assessed the influence of this gene on microalbuminuria in Type II (insulin-dependent) diabetes mellitus. Methods. Microalbuminuria was determined quantitatively in 386 sequential Type II diabetic patients by measurement of the albumin-to-creatinine ratio (ACR). DNA was analysed for two common intronic LPL single nucleotide polymorphisms (Pvu II, intron 6, and Hind III, intron 8), and three common exonic mutations (Asp9-Asn, exon 2, Asn291-Ser, exon 6, and Ser447-Ter, exon 9). Results. Individuals with P2P2 (Pvu II) and H2H2 (Hind III) genotypes had significantly greater ACRs (P2P2 vs P1P1+P1P2, 5.0±0.5 vs 3.4±0.3, p=0.0004 and H2H2 vs H1H1+H1H2, 4.3±0.4 vs 3.4±0.3, p=0.04). Logistic regression analysis demonstrated that only the P2P2 genotype (p=0.0004), systolic BP (p=0.008) and creatinine (p=0.031) were independently associated with the presence of microalbuminuria/proteinuria. P2 homozygotes were 170% more likely to have microalbuminuria or proteinuria, O.R. 2.7 (1.6–4.5, p=0.0001), 150% more likely to have microalbuminuria, O.R. 2.5 (1.5–4.3, p=0.001), and 330% more likely to have proteinuria, O.R. 4.3 (1.6–11.4, p=0.004). There were no associations of microalbuminuria with any of the exonic polymorphisms. Conclusion/interpretation. Genetic variants of lipoprotein lipase correlate with presence and severity of microalbuminuria in Type II diabetes, independent of effect on serum lipids. This association is only apparent in genetic variants demonstrating greatest heterozygosity.

Non-β-cell progenitors of β-cells in pregnant mice

Pregnancy is a normal physiological condition in which the maternal β-cell mass increases rapidly about two-fold to adapt to new metabolic challenges. We have used a lineage tracing of β-cells to analyse the origin of new β-cells during this rapid expansion in pregnancy. Double transgenic mice bearing a tamoxifen-dependent Cre-recombinase construct under the control of a rat insulin promoter, together with a reporter Z/AP gene, were generated. Then, in response to a pulse of tamoxifen before pregnancy, β-cells in these animals were marked irreversibly and heritably with the human placental alkaline phosphatase (HPAP). First, we conclude that the lineage tracing system was highly specific for β-cells. Secondly, we scored the proportion of the β-cells marked with HPAP during a subsequent chase period in pregnant and non-pregnant females. We observed a dilution in this labelling index in pregnant animal pancreata, compared to non-pregnant controls, during a single pregnancy in the chase period. To extend these observations we also analysed the labelling index in pancreata of animals during the second of two pregnancies in the chase period. The combined data revealed statistically-significant dilution during pregnancy, indicating a contribution to new beta cells from a non-β-cell source. Thus for the first time in a normal physiological condition, we have demonstrated not only β-cell duplication, but also the activation of a non-β-cell progenitor population. Further, there was no transdifferentiation of β-cells to other cell types in a two and half month period following labelling, including the period of pregnancy.