Imaging of primary and metastatic colorectal carcinoma with monoclonal antibody 791T/36 and the therapeutic potential of antibody-drug conjugates.

Monoclonal antibody 791T/36, prepared against a tumour-associated 72,000 dalton glycoprotein, reacted with cells from primary and metastatic colorectal carcinomas. I-131 or In-111-labelled antibody localized in xenografts of colorectal carcinomas established from in vitro clonogenic populations. Clinically, with I-131-labelled antibody, 8/11 colonic tumours imaged positively.

Genetic evidence for nucleotide excision repair of O6-alkylguanine in mammalian cells.

Human cells that lack O6-alkylguanine DNA alkyltransferase (AT) activity can remove O6-butylguanine (O6-nBuG) produced in cellular DNA by exposure to N-n-butyl-N-nitrosourea as determined by radioimmunoassay of enzyme digests of DNA. Fibroblasts from xeroderma pigmentosum (XP) complementation groups A and G that show less than 5% unscheduled DNA synthesis following exposure to UVC failed to remove O6-nBuG. Hence it appears that O6-alkylguanine is repaired in cells that lack AT by a process that is defective in XP cells, presumably nucleotide excision repair.

In vitro binding and in vivo localization in colorectal cancer of a high affinity monoclonal antibody to carcinoembryonic antigen.

A monoclonal antibody to carcinoembryonic antigen (CEA) (C46) was tested for its binding properties to colorectal cancer cells in vitro and for its localization in patients with primary colorectal cancer. Strong binding was found to disaggregated primary colorectal cancer cells, with a median of 66 per cent of the cells in the tumour gate binding the antibody. There was a median binding ratio of 8.

Association of antigen expression and DNA ploidy in human colorectal tumors.

Fifty colorectal tumors were screened by indirect immunofluorescence and flow cytometry for antigen expression using a panel of monoclonal antibodies that recognize determinants preferentially expressed on tumor cells (carcinoembryonic antigen, Y haptenic blood group, 791T/36 defined antigen 791T-P72). Fifty % of the tumors expressed all three antigens, 41%, two, and 9%, one. Over a third reacted strongly with at least one monoclonal antibody, although the majority of tumors stained with a moderate intensity.

Antigenicity of newly established colorectal carcinoma cell lines.

Cells from two adenocarcinomas, an adenoma and a metastatic node were isolated in soft agar. Expression of antigens, CEA, Y haptenic blood group and 791T-p72, defined by a range of candidate antibodies for tumour targeting was assessed. All of the cells expressed low levels of CEA but high levels of the Y haptenic blood group antigen although there was enormous inter and intraclonal variation.

Expression of HLA class I alpha chain determinants by human X mouse hybrid T cells is correlated with HLA-beta 2m but not with H-2.

The expression of HLA class I alpha chains by clones derived from a human X mouse T-cell line containing human chromosomes 6 and 15 was analysed by immunofluorescence. Evidence is presented showing that the expression of HLA class I alpha chains is associated with HLA-beta 2m. This is based on the phenotypic and quantitative fluorescence flow cytometric analysis of a series of cloned hybrids.

Characterization of a human X mouse T cell hybridoma and identification of a clone secreting and binding interleukin-2.

Human lymphocytes stimulated with phytohaemagglutinin (PHA) were fused with an HGPRT- murine lymphoma, BW5147, and a hybridoma BwFc93-1 was isolated and cloned in agarose. This human X mouse hybrid and nine clones derived from it were characterized by chromosome analysis, phenotypic and functional assays. Karyotyping and isoenzyme studies showed the presence of five human chromosomes in BwFc93-1 with preferential retention of three chromosomes--6, X and 15--in the clones.

Relative sensitivity of V79 and V79/79 cells to spontaneous and induced mutation to 6-thioguanine and ouabain resistance.

The relative responses of V79 and V79/79 cells to mutation to 6-thioguanine (6TGR) and ouabain resistance (OUAR) have been compared in unmutagenized cells and after exposure to ethyl methanesulphonate (EMS), N-methyl-N-nitrosourea (MNU) and ultraviolet light. In the V79/79 cell line, the spontaneous frequency of 6TGR colonies but not of OUAR colonies was enhanced compared to that in V79 cells. This appears to be the result of a reduced growth rate and plating efficiency of V79/79 cells and does not reflect a real difference in spontaneous mutability.

Potentiation of cell killing by inhibitors of poly(ADP-ribose) polymerase in four rodent cell lines exposed to N-methyl-N-nitrosourea or UV light.

The sensitivities (Do-values) of the cytotoxic effect of MNU on four rodent cell lines were: mouse L1210, 0.07 mM; rat Yoshida sarcoma, 0.52 mM; Chinese hamster V79A, 0.

Pretreatment of Chinese hamster v79 cells with MNU increases survival without affecting DNA repair or mutagenicity.

Exposure of Chinese hamster V79 cells to a non-toxic dose of N-methyl-N-nitrosourea, followed at intervals by exposure to toxic challenging doses of the same agent, resulted in increased survival of colony forming ability when these cells were compared with matched control cells that only received the challenging dose. The extent of the increase was dependent on the time interval between exposures, and rose to a maximum of about two-fold 5 days after the initial dose, declining slowly to control values on subsequent days. Whilst pretreatment enhanced survival, it altered neither the frequency of mutation to 6-thioguanine resistance, nor the formation or loss of 3-methyladenine, 7-methylguanine and O6-methylguanine.

Effects of 5-methylnicotinamide on mouse L1210 cells exposed to N-methyl-N-nitrosourea: mutation induction, formation and removal of methylation products in DNA, and unscheduled DNA synthesis.

The lethality of N-methyl-N-nitrosourea (MNU) to mouse L1210 cells, as determined by colon forming ability, was potentiated 2.8 fold by the addition of 1 mM 5'-methylnicotinamide (5MeN). When 5MeN was present throughout the expression and selection of 6-thioguanine resistant mutants, the MNU-induced mutation frequency was reduced in duplicate experiments from 15.