Protein kinase in immunoprecipitate of DMBA-transformed epithelial cells with serum from tumour-bearing rabbits

Altered growth properties and cell surface changes in ras transformed mouse bladder epithelium

Transfection of the c-Ha-ras-1 oncogene, cloned from EJ/T24 cells, into different mouse bladder epithelial cell lines resulted in the acquisition of tumorigenic potential and, in all but one cell line (MB33I), anchorage-independent growth. Sera from syngeneic mice bearing tumours immunoprecipitated an 18 kDa protein from ras-transfected urothelial cells which was not detectable in their parental counterparts. Screening of a limited panel of mouse cell lines showed this protein to be urothelium-specific and associated with the expression of an activated ras gene. Polyoma middle T and v-myc-transfected bladder epithelial cells did not express this 18 kDa protein. Localization of this protein to the cell surface was demonstrated by immunofluorescence and absorption studies.

Characterization of a new monoclonal antibody to a cell surface antigen on colorectal cancer and fetal gut tissues

Murine hybridoma were raised against the human colon carcinoma cell line CL-187. One clone was found to secrete a monoclonal antibody (ND-1) that recognizes a large external antigen (LEA) on human colon carcinoma cells. With indirect immunofluorescence on formaldehyde-fixed cells, more than 90% of the human colorectal carcinoma cell lines tested expressed LEA. Almost all of the 46 human noncolorectal and nonhuman cell lines tested did not express LEA, including cancer cell lines from other endodermally derived tissues. Staining of frozen sections from human colorectal tumors, noncolorectal tumors, normal adult, and normal fetal tissues showed expression of the antigen on colorectal cancer tissue, fetal colon, and fetal biliary epithelium. LEA can also be detected in the serum and ascites of colorectal cancer patients. Double indirect immunofluorescence with rabbit anti-carcinoembryonic antigen (CEA) antibody and ND-1 monoclonal antibody on a human colorectal carcinoma cell line showed that LEA is distinct from CEA. Physicochemical analysis of LEA showed that it has a large molecular weight, is resistant to extraction from the cell surface, and that sialic acid is an important component of the antigenic site. Because of the specificity for colorectal cancer tissue along with certain biochemical properties, LEA appears to be unique when compared with other tumor-associated antigens. Further research is needed to define the clinical usefulness of LEA in either the diagnosis or treatment of colorectal carcinoma.

Aflatoxin B1 alters protein phosphorylation in rat livers

A study was conducted on the effect of aflatoxin B1 on protein phosphorylation in rat livers by incubation of soluble and insoluble cell fractions with [gamma 32P] ATP. SDS-polyacrylamide gel electrophoresis indicated that a total of eight rat liver phosphoproteins were affected during a feeding period of 36 weeks on a carcinogenic aflatoxin B1-containing diet compared to the phosphoprotein patterns obtained from the livers of rats on a normal noncarcinogenic diet. The appearance of only two of these phosphoproteins were cAMP dependent. DEAE-cellulose chromatography employed to separate the different histone kinase activities in soluble rat liver cell fractions, showed that the specific activity of histone kinase I activity was increased but its total activity decreased while the histone kinase II activity stayed unchanged for rats submitted to the aflatoxin B1-containing diet compared to those on the normal noncarcinogenic diet.

cAMP-independent protein kinase activity is correlated with growth of rat mammary tumors

An important portion of the protein kinase activity in the 7,12-dimethylbenz(a)anthracene (DMBA) induced rat mammary tumour is inhibited by the bioflavonoid quercetin (10(-4) M). By partial purification on a DEAE Cellulose column it was shown that the quercetin-inhibitable enzyme activity can be eluted in a separate peak which contains markedly reduced cAMP-dependent protein kinase activity. Since quercetin does not affect the cAMP-dependent protein kinase activity, this drug becomes a potent tool for the quantitation of this special activity in the tumor. By hormonal manipulation, namely ovariectomy and estrogen treatment, it was shown that changes in the growth rate of the tumour were closely correlated with the magnitude of these special protein kinase activities. These results suggest a possible cause-and-effect relationship between cyclic AMP-independent protein kinase activity and tumour malignancy in this chemically induced tumor. These data are similar to recent findings in viral-induced malignant transformation.

Cytochemical markers of bladder carcinogenesis

Enzyme cytochemical and immunocytochemical techniques at the light and electron microscope levels were used to study the distribution of potential markers of chemical transformation in rodent bladders. In rat tumours induced by in vivo treatment with methylnitrosourea, alkaline phosphatase localization was normal on the external surface of the plasma membranes of some cells but abnormal in others where reaction product was seen only on intracellular membranes. 5'-Nucleotidase localization was abnormal in all cells, being seen on endoplasmic reticulum and nuclear membranes only, while in normal bladders only ectoenzyme localization was seen. Heterogeneity of alkaline phosphatase amd 5'-nucleotidase localization was seen on the plasma membranes of these tumours after 15 days in organ culture. Some cells produced enzyme and others did not; in other cells only parts of the membrane reacted heavily, while other regions were negative. In transformed cell cultures and tumours of mouse bladder derived by in vitro treatment of explants with dimethylbenz (a) anthracene, a bimodal pattern of alkaline phosphatase localization was seen. Cells had either normal ectoenzyme reaction product or abnormal intracellular membrane reaction product. 5'-Nucleotidase and ADPase were lost after transformation while cAMP-phosphodiesterase was retained as an ectoenzyme. Mg.ATPase and a cAMP-independent, calcium-insensitive 'protein phosphatase' were induced in transformed cell cultures. An epithelial antigen was detected in the cytoplasm of both normal and transformed cells associated with reticular cytoplasmic ground substance, plasma membrane vesicles and cytoskeletal elements.