Baris Emre Dayanc

Colon cancer associated transcript‐1: A novel RNA expressed in malignant and pre‐malignant human tissues

Early detection of colorectal cancer (CRC) is currently based on fecal occult blood testing (FOBT) and colonoscopy, both which can significantly reduce CRC‐related mortality. However, FOBT has low‐sensitivity and specificity, whereas colonoscopy is labor‐ and cost‐intensive. Therefore, the discovery of novel biomarkers that can be used for improved CRC screening, diagnosis, staging and as targets for novel therapies is of utmost importance. To identify novel CRC biomarkers we utilized representational difference analysis (RDA) and characterized a colon cancer associated transcript (CCAT1), demonstrating consistently strong expression in adenocarcinoma of the colon, while being largely undetectable in normal human tissues (p < 000.1). CCAT1 levels in CRC are on average 235‐fold higher than those found in normal mucosa. Importantly, CCAT1 is strongly expressed in tissues representing the early phase of tumorigenesis: in adenomatous polyps and in tumor‐proximal colonic epithelium, as well as in later stages of the disease (liver metastasis, for example). In CRC‐associated lymph nodes, CCAT1 overexpression is detectable in all H&E positive, and 40.0% of H&E and immunohistochemistry negative lymph nodes, suggesting very high sensitivity. CCAT1 is also overexpressed in 40.0% of peripheral blood samples of patients with CRC but not in healthy controls. CCAT1 is therefore a highly specific and readily detectable marker for CRC and tumor‐associated tissues.

Enhancement of natural killer (NK) cell cytotoxicity by fever-range thermal stress is dependent on NKG2D function and is associated with plasma membrane NKG2D clustering and increased expression of MICA on target cells

Circulating NK cells normally experience temperature gradients as they move about the body, but the onset of inflammation can expose them and their targets to febrile temperatures for several hours. We found that exposure of human peripheral blood NK cells and target cells to fever‐range temperatures significantly enhances lysis of Colo205 target cells. A similar effect was not observed when NK cell lines or IL‐2‐activated peripheral blood NK cells were used as effectors, indicating that thermal sensitivity of effectors is maturation or activation state‐dependent. Use of blocking antibodies revealed that this effect is also dependent on the function of the activating receptor NKG2D and its ligand MHC class I‐related chain A (MICA). On NK cells, it was observed that thermal exposure does not affect the total level of NKG2D surface expression, but does result in its distinct clustering, identical to that which occurs following IL‐2‐induced activation. On tumor target cells, a similar, mild temperature elevation results in transcriptional up‐regulation of MICA in a manner that correlates with increased sensitivity to cytolysis. Overall, these data reveal that NK cells possess thermally responsive regulatory elements, which facilitate their ability to capitalize on reciprocal, stress‐induced changes simultaneously occurring on target cells during inflammation and fever.

Dissecting the role of hyperthermia in natural killer cell mediated anti-tumor responses

The effects of hyperthermia on natural killer (NK) cell cytotoxicity against tumor cell targets are not yet fully understood. A more complete understanding of these effects could be important for maximizing the clinical benefits obtained by using hyperthermia for cancer therapy. Here, we summarize results in the literature regarding the effects of elevated temperatures on NK cells and our own recent data on the effects of fever-range temperatures. At treatment temperatures above 40°C, (which is above the physiological body temperatures normally achieved during fever or exercise), both enhancing and inhibitory effects on cytotoxic activity of NK cells against tumor cells have been reported. Our own results have shown that fever-range thermal stress (using a temperature of 39.5°C) enhances human NK cell cytotoxicity against tumor target cells. This effect requires function of the NKG2D receptor of NK cells, and is maximal when both NK and tumor cell targets are heated. Reported heat sensitive cellular targets affected by hyperthermia on tumor cells include heat shock proteins, MICA and MHC Class I. In NK cells, plasma membrane reorganization may occur after mild heat stress. We conclude this review by listing several unresolved questions that should be addressed for a more complete understanding of the molecular mechanisms which underlie the effects of thermal stress on the function of NK cells. Altogether, the available data indicate a strong potential for heat-induced enhancement of NK cell activity in mediating, at least in part, the improved clinical responses seen when hyperthermia is used in combination with other therapies.

Enhanced sensitivity of colon tumour cells to natural killer cell cytotoxicity after mild thermal stress is regulated through HSF1-mediated expression of MICA

Abstract Purpose: Previously we showed that mild thermal stress increased natural killer (NK) cell-mediated tumour cytotoxicity and that this could be blocked by anti-NKG2D or anti-MICA (major histolocompatability complex (MHC) class I related chain A) antibodies. Here, we investigated the role of the transcription factor heat shock factor 1 (HSF1) in thermal regulation of MICA expression in tumour cells in vitro and in vivo. Materials and methods: Hyperthermia experiments were conducted in vitro and in mice using a target temperature of 39.5 °C. Apoptotic cells and NK cells in situ were visualised by use of the TUNEL assay or expression of NKp46 respectively. Using Colo205 cells, HSF1 message was blocked utilising siRNA while luciferase reporter assays were used to measure the activity of the MICA promoter in vitro. Cell surface MICA was measured by flow cytometry. Results: Following whole body hyperthermia (WBH), tumour tissues showed an increase in NK cells and apoptosis. Mild thermal stress resulted in a transient increase in surface MICA and enhanced NK cytotoxicity of the Colo205 colon cancer cell line. Silencing (mRNA) HSF1 expression in Colo205 cells prevented the thermal enhancement of MICA message and surface protein levels, with partial loss of thermally enhanced NK cytotoxicity. Mutations of the HSF1 binding site on the MICA promoter implicated HSF1 in the thermal enhancement of MICA. Some, but not all, patient-derived colon tumour derived xenografts also exhibited an enhanced MICA message expression after WBH. Conclusions: Up-regulation of MICA expression in Colo205 cells and enhanced sensitivity to NK cell killing following mild thermal stress is dependent upon HSF1.

A Combined ULBP2 and SEMA5A Expression Signature as a Prognostic and Predictive Biomarker for Colon Cancer

Background: Prognostic biomarkers for cancer have the power to change the course of disease if they add value beyond known prognostic factors, if they can help shape treatment protocols, and if they are reliable. The aim of this study was to identify such biomarkers for colon cancer and to understand the molecular mechanisms leading to prognostic stratifications based on these biomarkers. Methods and Findings: We used an in house R based script (SSAT) for the in silico discovery of stage-independent prognostic biomarkers using two cohorts, GSE17536 and GSE17537, that include 177 and 55 colon cancer patients, respectively. This identified 2 genes, ULBP2 and SEMA5A, which when used jointly, could distinguish patients with distinct prognosis. We validated our findings using a third cohort of 48 patients ex vivo. We find that in all cohorts, a combined ULBP2/SEMA5A classification (SU-GIB) can stratify distinct prognostic sub-groups with hazard ratios that range from 2.4 to 4.5 (p≤0.01) when overall- or cancer-specific survival is used as an end-measure, independent of confounding prognostic parameters. In addition, our preliminary analyses suggest SU-GIB is comparable to Oncotype DX colon(®) in predicting recurrence in two different cohorts (HR: 1.5-2; p≤0.02). SU-GIB has potential as a companion diagnostic for several drugs including the PI3K/mTOR inhibitor BEZ235, which are suitable for the treatment of patients within the bad prognosis group. We show that tumors from patients with worse prognosis have low EGFR autophosphorylation rates, but high caspase 7 activity, and show upregulation of pro-inflammatory cytokines that relate to a relatively mesenchymal phenotype. Conclusions: We describe two novel genes that can be used to prognosticate colon cancer and suggest approaches by which such tumors can be treated. We also describe molecular characteristics of tumors stratified by the SU-GIB signature.

Altered isotope charge distribution of acetylcholine neurotransmitter and Myasthenia Gravis

Acetylcholine (ACh) is a central neurotransmitter that is used for signal transmission among neurons. For signal transmission in neurons, a neurotransmitter must bind to its receptor in order to produce an action potential. It is known that in Myasthenia Gravis (MG) cases, autoantibodies could block this binding. In the future, the treatment of MG could be achieved via modulation of molecular interaction between ACh and acetylcholine receptor (AChR). This study suggests that if an atom on a ligand (i.e. a neurotransmitter) is replaced with its isotope, it may cause charge redistribution such as that the binding between ligand and its receptor may be improved. Hence suggesting that with replacement of atoms with their isotopes in any biologically important ligand could alter its affinity towards its corresponding receptor, which would have a wide array of applications in medicine.