Investigation of the association of esophageal carcinoma with human papillomaviruses.

The role of human papillomavirus (HPV) in esophageal cancers was evaluated in patients seen at Johns Hopkins University Hospital. Frozen esophageal tumor tissues from 22 cases with squamous cell carcinoma (SCC) and 24 cases with adenocarcinoma (AC), diagnosed between 1988 and 1998, were assayed for HPV sequences by reverse line blot polymerase chain reaction. HPV sequences (HPV-54) were detected in a single specimen; the other 45 specimens were negative. The HPV sequences in the positive specimen may represent infection of the epithelium. Our results suggest that genital HPVs may sometimes infect the esophagus, but there is no evidence to indicate that these infections contribute substantially to the development of esophageal cancer in North America.

Histamine alters cadherin-mediated sites of endothelial adhesion.

We tested the hypothesis that histamine alters the focal apposition of endothelial cells by acting on sites of cadherin-mediated cell-cell adhesion. Focal apposition was measured as the impedance of a cell-covered electrode, which was partitioned into a cell-matrix resistance, a cell-cell resistance, and membrane capacitance. Histamine causes an immediate, short-lived decrease in the impedance of an electrode covered with human umbilical vein endothelial (HUVE) cells. ECV304 cells are a line of spontaneously transformed HUVE cells that do not express the endothelial cadherin, cadherin-5. Histamine increased ECV304 cell calcium to 600 nM. Histamine did not increase myosin light chain phosphorylation of control or transfected ECV304 cells. ECV304 cells transfected with either E-cadherin or cadherin-5 on a dexamethasone-responsive plasmid (pLKneo) increased their cell-cell resistance when stimulated with dexamethasone, whereas ECV304 cells transfected with pLKneo-lacZ did not. Histamine did not affect the impedance of ECV304 cells transfected with pLKneo-lacZ. In contrast, histamine decreased the cell-cell resistance of ECV304 cells transfected with either pLKneo-E-cadherin or pLKneo-cadherin-5. From these data, we conclude that histamine acts on sites of cadherin-mediated cell-cell apposition.

Thrombin inhibits myosin light chain dephosphorylation in endothelial cells.

Histamine and thrombin increase myosin light-chain kinase-mediated phosphorylation of myosin light chain (MLC) in human umbilical vein endothelial cells (HUVEC). The increase in MLC phosphorylation caused by thrombin persists longer (330 min) than the increase caused by histamine (<5 min), although both increase cell calcium similarly. We hypothesized that some of the longer duration of the increase in MLC phosphorylation caused by thrombin was because of inhibition of myosin dephosphorylation by thrombin. Calyculin A, an inhibitor of type 1 and 2A protein phosphatases, caused a time-dependent increase in MLC phosphorylation in unstimulated HUVEC. As thrombin-stimulated phosphorylation approached its peak at 15 min, calyculin A caused progressively less of an increase in MLC phosphorylation in thrombin-stimulated HUVEC, and no increase at the peak of thrombin stimulation. In HUVEC in which cell calcium was maintained at 600 nM, thrombin increased MLC phosphorylation above the level caused by increased calcium alone at a time coinciding with the peak of thrombin stimulation. However, when phosphatase activity was already inhibited with calyculin A, thrombin did not further increase MLC phosphorylation in cells in which calcium was maintained at 600 nM calcium. Thrombin increases MLC phosphorylation in HUVEC not only by increasing cell calcium but also by inhibiting calyculin A-sensitive dephosphorylation of MLC.