Frequent mutation of p16 in squamous cell carcinoma of the head and neck.

RNA was isolated from 22 squamous cell carcinomas (SCCs) obtained from diverse sites within the head and neck and from matched normal tissue where available. Tissue samples were then screened for expression of RNA from tumor suppressor gene p16 by utilizing semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis. p16-Specific PCR amplification products generated from tumor samples were subject to further analysis by direct DNA sequencing to determine if any tumor sample harbored a p16 mutation. The results show the presence of mutations in 10 of 22 (45%) of the tumor samples. Mutations comprise two identical point mutations, two small deletions (1 bp and 2 bp), one single-nucleotide insertion, four larger deletions, and an insertion/deletion. No mutations in p16 have been identified by analysis of PCR products generated from normal matched tissue, suggesting that p16 alterations are generated by somatic mutation and are not germline in origin. All 22 samples were analyzed additionally by immunohistochemistry for nuclear expression of the retinoblastoma (RB) tumor suppressor gene product. Results show lack of RB nuclear expression in only one sample, suggesting that mutation of RB is an infrequent event in the development of SCC of the head and neck (SCCHN).

Human natural killer cells produce abundant macrophage inflammatory protein-1 alpha in response to monocyte-derived cytokines.

Once infected by obligate intracellular pathogens, monocytes/macrophages release cytokines that activate natural killer (NK) cells. NK cells in turn produce and secrete monocyte/macrophage activating factors such as interferongamma (IFN-gamma), which are important in the early control of these infections. Here we demonstrate that human NK cells are potent producers of another monocyte/macrophage-activating factor, macrophage inflammatory protein-1 alpha (MIP-1 alpha). Fresh NK cells produce negligible amounts of MIP-1 alpha after stimulation with the monocyte-derived cytokines IL-12, TNF-alpha, IL-1 beta, or IL-10, while stimulation with IL-15 alone results in modest MIP-1 alpha production. Abundant NK cell production MIP-1 alpha is seen after costimulation with IL-12 and IL-15, and is dose-dependent. Combinations of IL-12, with TNF-alpha, IL-1 beta, or IL-10 are substantially less effective inducers of MIP-1 alpha production by NK cells. NK cell MIP-1 alpha mRNA transcripts were detectable within 1 h after costimulation with IL-12 plus IL-15 and steadily increased over 24 h, with a concomitant increase in protein production detectable at 12 h. Resting NK cells constitutively express mRNA transcript for a MIP-1 alpha receptor, and costimulation with IL-12 and IL-15 upregulates its level of expression. Equilibrium binding studies with radioiodinated MIP-1 alpha were consistent with the induction of a single class of high affinity MIP-1 alpha receptors on NK cells costimulated with IL-12 and IL-15. Addition of exogenous MIP-1 alpha to resting NK cells did not enhance cytokine production, but did increase NK cytotoxic activity. The requirement for IL-15 as a critical cofactor for NK cell production MIP-1 alpha suggests a potentially unique role for this monocyte-derived cytokine in combination with IL-12. As MIP-1 alpha is known to potentiate the action of IFN-gamma on monocytes and to suppress human immunodeficiency virus replication, the NK cell's production of MIP-1 alpha may be important during the innate immune response to infection.

The active monomeric form of macrophage inflammatory protein-1 alpha interacts with high- and low-affinity classes of receptors on human hematopoietic cells.

Macrophage inflammatory protein-1 alpha (MIP-1 alpha) and its human homologue GOS19.1/LD78 are members of the C-C chemokine/intercrine family of secreted proteins. They have proinflammatory properties and also inhibit cell cycle progression of hematopoietic stem cells. Characterization of MIP-1 alpha receptor(s) has been confused because of its reported aggregation to inactive forms. Using a defined monomeric form of MIP-1 alpha that is biologically active for stem cell inhibition and induction of oxidative metabolism in polymorphonuclear cells, we report the detection of high- and low-affinity receptor classes on human leukemic CD34+ blast cells, promyelocytic cells, monocytes, peripheral blood neutrophils, and T cells. Both high- and low-affinity classes are expressed simultaneously in promyelocytes and neutrophils. The calculated kd for high-affinity receptors correlates with the concentrations of MIP-1 alpha required to induce a biologic effect on stem cells and neutrophils. Cross-linking studies show that MIP-1 alpha associates with two cell surface proteins with apparent molecular masses of 92 kD and 52 kD. Direct competition binding studies combined with studies on the inhibition of stem cells show that human and murine MIP-1 alpha have different receptor-binding and biologic properties.