Association Between Natural Killer Cell Activity and Colorectal Cancer in High-Risk Subjects Undergoing Colonoscopy

BACKGROUND & AIMS

Low activity of natural killer (NK) cells has been associated with increased risk of cancer and has been reported in patients with colorectal cancer (CRC). Activity of NK cells can be measured in a small volume of whole blood by a commercially available test. We investigated whether this test could be used to identify patients with CRC, using findings from colonoscopy as a reference standard.

METHODS

We performed an open-label, prospective, cross-sectional study of 872 high-risk subjects (more than 40 years old) screened for CRC by colonoscopy at a university hospital in Montreal, Canada from October 2014 through January 2016. Blood samples were collected on the day of colonoscopy, prior to the procedure. The test involves stimulation of whole blood with cytokine that induces NK cells to secrete interferon gamma (IFNG), which is quantified by an ELISA. Tissue samples were taken from lesions during the colonoscopy and analyzed histologically; subjects were classified as having no evidence of disease, adenomatous polyps of less than 10 mm, of 10 mm or more, or CRC. We used the non-parametric Mann-Whitney test to compare NK cell activity between subjects with no evidence of CRC and subjects found to have CRC. Receiver operating characteristic curve analysis was used to assess the ability of the test to identify individuals with CRC. The primary objective was to determine the difference in NK cell activity between subjects with vs without CRC. The secondary objective was the test performance, based on receiver operating characteristic analysis, and cut-off value that most accurately identified individuals with CRC.

RESULTS

We found a significant difference in NK cell activity between the 23 subjects with CRC (based on pathology analysis) and the 849 subjects without CRC: subjects found to have CRC by colonoscopy had a median level of 86.0 pg IFNG/mL (inter-quartile range, 43.3-151.0 pg IFNG/mL), whereas subjects without CRC had a median level of 298.1 pg IFNG/mL (inter-quartile range, 100.4-920.2 pg IFNG/mL) (P = .0002). The cut-off value that most accurately identified subjects with CRC was 181 pg/mL. The NK cell activity test identified subjects with CRC with 87.0% sensitivity, 60.8% specificity, a positive predictive value of 5.7%, and a negative predictive value of 99.4%. The odds ratio for detection of CRC in subjects with low NK cell activity vs subjects with higher NK cell activity was 10.3 (95% CI, 3.03-34.9).

CONCLUSIONS

Using colonoscopy as the reference standard, a test for NK cell activity in whole blood samples identified patients with CRC with 87.0% sensitivity and a negative predictive value of 99.4%. Subjects with low NK cell activity had a 10-fold higher risk of CRC compared with subjects with high NK cell activity. This test might be used in clinical practice to assess patients for risk of CRC. Clinicaltrials.gov number: NCT02291198.

Association between natural killer cell activity and prostate cancer: a pilot study

INTRODUCTION

Natural killer (NK) cells play a significant role in tumor cell immunosurveillance. The association between the activity of NK cells and prostate cancer has previously been demonstrated using conventional research-based tests.

MATERIALS AND METHODS

The aim of the present pilot study was to study the association between NK cell activity (NKA) and prostate cancer using a simple blood test. Subjects that had previously been selected for prostate biopsy underwent a blood test for NKA using an in vitro diagnostic device (IVDD) (NK Vue, ATGen Canada Inc., Laval, QC, Canada) prior to biopsy.

RESULTS

Of the 43 subjects sent for prostate biopsy, 22 were found to have prostate cancer. The test performance of the NKA IVDD, assessed using receiver operating characteristics, showed an area under the curve of 75%, a sensitivity of 57%, a specificity of 91%, a positive predictive value of 86% and a negative predictive value of 69%, with an odds ratio of 13.33. Using a cut off of 200 pg/mL for NKA, the absolute risk of having prostate cancer with NKA values below this level was found to be 86%.

CONCLUSIONS

This pilot study showed that subjects with low values of NKA were more likely to have a positive outcome at prostate biopsy.

Development of homogeneous nonradioactive methyltransferase and demethylase assays targeting histone H3 lysine 4

Histone posttranslational modifications are among the epigenetic mechanisms that modulate chromatin structure and gene transcription. Histone methylation and demethylation are dynamic processes controlled respectively by histone methyltransferases (HMTs) and demethylases (HDMs). Several HMTs and HDMs have been implicated in cancer, inflammation, and diabetes, making them attractive targets for drug therapy. Hence, the discovery of small-molecule modulators for these two enzyme classes has drawn significant attention from the pharmaceutical industry. Herein, the authors describe the development and optimization of homogeneous LANCE Ultra and AlphaLISA antibody-based assays for measuring the catalytic activity of two epigenetic enzymes acting on lysine 4 of histone H3: SET7/9 methyltransferase and LSD1 demethylase. Both the SET7/9 and LSD1 assays were designed as signal-increase assays using biotinylated peptides derived from the N-terminus of histone H3. In addition, the SET7/9 assay was demonstrated using full-length histone H3 protein as substrate in the AlphaLISA format. Optimized assays in 384-well plates are robust (Z' factors ≥0.7) and sensitive, requiring only nanomolar concentrations of enzyme and substrate. All assays allowed profiling of known SET7/9 and LSD1 inhibitors. The results demonstrate that the optimized LANCE Ultra and AlphaLISA assay formats provide a relevant biochemical screening approach toward the identification of small-molecule inhibitors of HMTs and HDMs that could lead to novel epigenetic therapies.

A screen for genes of heme uptake identifies the FLC family required for import of FAD into the endoplasmic reticulum

Although Candida albicans and Saccharomyces cerevisiae express very similar systems of iron uptake, these species differ in their capacity to use heme as a nutritional iron source. Whereas C. albicans efficiently takes up heme, S. cerevisiae grows poorly on media containing heme as the sole source of iron. We identified a gene from C. albicans that would enhance heme uptake when expressed in S. cerevisiae. Overexpression of CaFLC1 (for flavin carrier 1) stimulated the growth of S. cerevisiae on media containing heme iron. In C. albicans, deletion of both alleles of CaFLC1 resulted in a decrease in heme uptake activity, whereas overexpression of CaFLC1 resulted in an increase in heme uptake. The S. cerevisiae genome contains three genes with homology to CaFLC1, and two of these, termed FLC1 and FLC2, also stimulated growth on heme when overexpressed in S. cerevisiae. The S. cerevisiae Flc proteins were detected in the endoplasmic reticulum and the FLC genes encoded an essential function, as strains deleted for either FLC1 or FLC2 were viable, but deletion of both FLC1 and FLC2 was synthetically lethal. FLC gene deletion resulted in pleiotropic phenotypes related to defects in cell wall integrity. High copy suppressors of this synthetic lethality included three mannosyltransferases, VAN1, KTR4, and HOC1. FLC deletion strains exhibited loss of cell wall mannose phosphates, defects in cell wall assembly, and delayed maturation of carboxypeptidase Y. Permeabilized cells lacking FLC proteins exhibited dramatic loss of FAD import activity. We propose that the FLC genes are required for import of FAD into the lumen of the endoplasmic reticulum, where it is required for disulfide bond formation.

Interspecies cross-reactivity of a monoclonal antibody directed against wheat chloroplast fructose-1,6-bisphosphatase

The primary structure of several chloroplast fructose-1,6-bisphosphatase (CFBPase) was deduced from DNA sequences, but only spinach, pea and rapeseed enzymes have been characterized structurally. We analyzed whether CFBPases from different phylogenetic origin contain a common epitope. To this end a DNA fragment of 1200 base pairs encoding 338 amino acid residues of wheat CFBPase (38 kDa) was cloned in the expression plasmid pGEX-1 in frame with the gene coding for glutathione S-transferase (GT) of Schistosoma japonicun (26.5 kDa). Upon transformation of Escherichia coli and induction with isopropyl-beta-D-thiogalactopyranoside, centrifugation of the lysate partitioned 10% of the fusion protein in the supernatant fraction and the remaining 90% in the precipitate. The expected 65 kDa protein was purified from both the soluble and the particulate fraction by affinity chromatography on columns of glutathione-agarose. This fusion protein was successfully used to produce a monoclonal antibody that specifically recognized the CFBPase region of the fusion protein but not the GT moiety. Moreover, the monoclonal antibody immunoreacted not only with polypeptides (ca. 40 kDa) present in leaf crude extracts of other varieties of wheat (Triticum spelta, T. aestivum and T. durum), but also with homogeneous preparations of the spinach (Spinacia oleracea) and rapeseed (Brassica napus) enzymes. Thus, the cross reaction of this monoclonal antibody with counterparts from different plant species indicates the persistency of a common epitope through biological evolution.