Cellular membranes and tumor behavior: a new hypothesis

Glucocorticoid-induced alteration of the surface membrane of cultured hepatoma cells

Glucocorticoids induce an alteration of the surface of hepatoma tissue culture (HTC) cells as expressed by changes in cell electrophoretic, antigenic, and adhesive properties. The alteration is assayed by the increased adhesiveness of induced cells for a glass surface. The induction process has a lag period of about 3 hr and attains a plateau level after 24-30 hr when 50-80% of the steroid-treated cells are firmly adhered. Less than 10% of untreated cells adhere under the same conditions. Induction is inhibited by actinomycin D and cycloheximide, demonstrates both pH and temperature dependence, and responds to changes in steroid concentration and structure. By contrast, the attachment per se of preinduced cells is not affected by inhibitors of RNA and protein synthesis, fluctuations of temperature and pH, and the presence or absence of the hormone. When the induction process is reversed by removal of steroid or addition of actinomycin D, preinduced adhesiveness is lost with a half-life of 13-24 hr, but in the presence of cycloheximide the loss is accelerated (t(1/2) 3-5.5 hr). These results suggest that glucocorticoids induce the biosynthesis of a protein which either modifies the cell surface (an enzyme) or is incorporated into surface structures (structural protein).

Proteins specified by herpes simplex virus. 3. Viruses differing in their effects on the social behavior of infected cells specify different membrane glycoproteins

We examined the electrophoretic properties of the proteins and glycoproteins in the smooth membranes and virions purified from cells infected with herpes simplex virus strains differing with respect to their effects on the interaction of cells among themselves. The data show the following: (1) The glycoproteins in virions and binding to membranes share common features but vary quantitatively and qualitatively depending on the virus strain. (2) The binding to smooth membranes is ordered and not random. (3) Differences in the glycosylation of membrane proteins in African green monkey (VERO) and human (HEp-2) cells indicate that glycosylation is at least in part determined by the host.

Filamentous bacterial viruses

Images

Complex mitochondrial DNA in leukemic and normal human myeloid cells

Mitochondrial DNA's from the peripheral blood of 14 patients with granulocytic leukemia contained a circular dimer form. No such structure could be found in M DNA's from three patients with nonmalignant proliferations of granulocytes. The frequency of the circular dimer form is reduced upon treatment with antileukemic drugs. The above results suggest that a significant relation exists between the formation and presence of the circular dimer M DNA form and granulocytic leukemia in man.