Zoya B. Kurago

DNA Methylation Maintains Allele-specific KIR Gene Expression in Human Natural Killer Cells

Killer immunoglobulin-like receptors (KIR) bind self–major histocompatibility complex class I molecules, allowing natural killer (NK) cells to recognize aberrant cells that have down-regulated class I. NK cells express variable numbers and combinations of highly homologous clonally restricted KIR genes, but uniformly express KIR2DL4. We show that NK clones express both 2DL4 alleles and either one or both alleles of the clonally restricted KIR 3DL1 and 3DL2 genes. Despite allele-independent expression, 3DL1 alleles differed in the core promoter by only one or two nucleotides. Allele-specific 3DL1 gene expression correlated with promoter and 5′ gene DNA hypomethylation in NK cells in vitro and in vivo. The DNA methylase inhibitor, 5-aza-2′-deoxycytidine, induced KIR DNA hypomethylation and heterogeneous expression of multiple KIR genes. Thus, NK cells use DNA methylation to maintain clonally restricted expression of highly homologous KIR genes and alleles.

Elevated focal adhesion kinase expression facilitates oral tumor cell invasion

Understanding the molecular mechanisms of metastasis is critical with respect to oral tumorigenesis. The focal adhesion kinase (FAK) is an intracellular tyrosine kinase associated with the regulation of cell growth, migration, and survival. The purpose of the current study was to determine whether elevated FAK expression in oral malignancies was associated with increased invasiveness and oral carcinoma.

Chondromyxoid fibroma of the jaws: Case report and review of the literature

Chondromyxoid fibroma is a benign tumor of bone that is characterized by chondroid and myxoid differentiation and by ultrastructural and immunohistochemical evidence of chondral origin. It is rare in the jaws and skull bones, where only about 2% of all cases have been reported. A review of the 20 acceptable gnathic cases in the literature and of the current case revealed both a higher incidence in the mandible (76%) than in the maxilla (24%) and an equal sex distribution. The sites of occurrence in both jaws are compatible with origin from developmental cartilaginous remnants. The controversies regarding malignant transformation and therapeutic approach are addressed.

Squamous cell carcinoma cells differentially stimulate NK cell effector functions: the role of IL-18

Tumor cells stimulate natural killer (NK) cell effector functions, but the regulation of cytokine secretion and cytolysis is incompletely understood. We tested whether oral and pharyngeal squamous cell carcinoma cell lines differentially stimulated NK cell interferon-γ (IFN-γ) secretion and cytolysis using a clone of the NK-92-transformed human NK cell line, NK92.35. SCC-4 and SCC-25 cells, but not FaDu or Cal 27 cells, stimulated robust NK92.35 IFN-γ secretion. All four carcinoma cell lines were lysed by NK92.35 cells. These findings indicate that carcinoma cells differentially stimulate NK cell IFN-γ secretion and cytolysis. In Transwell experiments, a combination of SCC-4 or SCC-25 cell soluble factors and contact with FaDu cells synergistically stimulated NK92.35 cell IFN-γ secretion. Stimulatory SCC-4 cells constitutively secreted IL-18, a cytokine that potently augments IFN-γ secretion by T cells and NK cells. In contrast, poorly stimulatory FaDu cells produced little or no IL-18, but synergized with recombinant IL-18 to stimulate NK92.35 IFN-γ secretion. mAb to IL-18 or IL-18 receptor diminished SCC-4-stimulated IFN-γ secretion by NK92.35 cells and by nontransformed NK cells. Thus, IL-18 was necessary for optimal carcinoma stimulation of NK cell IFN-γ secretion. In vivo, oral and upper aerodigestive tract epithelia and carcinomas produced IL-18, but one squamous cell carcinoma had heterogeneous IL-18 expression. Thus IL-18 production can account for squamous cell carcinoma differential stimulation of NK cell effector functions in vitro and may be important for stimulation of NK cells in vivo.

Malignant Melanoma of the Oral Mucosa in a 17-Year-Old Adolescent Girl

Mucosal melanomas of the oral cavity are rarely seen in the United States. The hard palate is the most common intraoral site. This unusual case occurred in the oral cavity of a 17-year-old Asian girl, who presented to her dentist with complaints of pain and swelling in the upper jaw. The lesion was distal and palatal to the maxillary left second molar, which was vital. Interestingly, the clinical presentation was a hyperplastic, tender lesion that bled when probed. Histopathologically, the biopsy demonstrated a sheet of spindle-shaped cells arranged in nests and fascicles. The nuclei were vesicular, oval to spindle-shaped, and some contained nucleoli that were distinguishable but not prominent. No melanin pigment was observed in the lesion. Tumor cells strongly expressed S100 protein, gp100 (HMB-45), and microphthalmia transcription factor, and variably expressed MART1, but not cytokeratins, CD34, or muscle-specific actin. The histopathologic features and immunohistochemical findings are consistent with a diagnosis of malignant melanoma.

Conformational changes in MHC class I molecules. Antibody, T-cell receptor, and NK cell recognition in an HLA-B7 model system

In this article we review the role of MHC conformation, including peptide-induced MHC conformation, in forming antibody (Ab), T-cell receptor (TCR), and natural killer (NK) cell receptor epitopes. Abs recognize conformational major histocompatibility (MHC) epitopes that often are influenced by the identity of MHC-bound peptide. Diverse TCRs recognize a common docking site on peptide/MHC complexes and directly contact peptide. Human NK cell inhibitory receptors (KIR) appear to recognize limited regions of the HLA α1 helix. DX9+ KIR specifically focus on HLA-B residues 82 and 83. However, NK cells recognize much broader regions of HLA class I molecules and are sensitive to bound peptides. Thus, several classes of lymphocyte receptors are peptidespecific. Peptide specificity could be the result of direct contact with the receptor, or to conformational shifts in MHC residues that interact with both receptor and bound peptide.

GPR81, a cell-surface receptor for lactate, regulates intestinal homeostasis and protects mice from experimental colitis

At mucosal sites such as the intestine, the immune system launches robust immunity against invading pathogens while maintaining a state of tolerance to commensal flora and ingested food Ags. The molecular mechanisms underlying this phenomenon remain poorly understood. In this study, we report that signaling by GPR81, a receptor for lactate, in colonic dendritic cells and macrophages plays an important role in suppressing colonic inflammation and restoring colonic homeostasis. Genetic deletion of GPR81 in mice led to increased Th1/Th17 cell differentiation and reduced regulatory T cell differentiation, resulting in enhanced susceptibility to colonic inflammation. This was due to increased production of proinflammatory cytokines (IL-6, IL-1β, and TNF-α) and decreased expression of immune regulatory factors (IL-10, retinoic acid, and IDO) by intestinal APCs lacking GPR81. Consistent with these findings, pharmacological activation of GPR81 decreased inflammatory cytokine expression and ameliorated colonic inflammation. Taken together, these findings identify a new and important role for the GPR81 signaling pathway in regulating immune tolerance and colonic inflammation. Thus, manipulation of the GPR81 pathway could provide novel opportunities for enhancing regulatory responses and treating colonic inflammation.