Cytokeratins expressed in experimental rat bronchial carcinomas.

Cytokeratin expression in rat lung tumors was studied using polypeptide-specific monoclonal antibodies (MAbs) to human cytokeratins 4, 5, 7, 8, 10, 13, 14, 18 and 19. Experiments were performed on tumor fragments derived from 5 experimental rat squamous-cell lung tumors and one adenocarcinoma, as well as on cell lines obtained from the same tumors. The aims of this study were to investigate the differentiation profile of the rat tumor tissue and established tumor cell lines based on light and electron microscopical features and on cytokeratin phenotype, to characterize the tumor type and degree of differentiation of the lung tumors maintained during passaging in experimental animals, and to compare the cytokeratin expression pattern in transplanted tumors with that of the cultures derived from these tumors. Our results indicate that, in general, the antibodies used cross-react with rat cytokeratins and that these MAbs can be used to phenotype rat lung carcinomas. Both the tumor fragments and the cultured cells revealed a similar pattern of cytokeratin expression. In addition, the degree of differentiation was maintained upon prolonged culturing in vitro. MAbs to cytokeratin sub-types can therefore be used to distinguish the main sub-types of rat lung tumors and can give an indication about the degree of differentiation.

Immunotargeting of human small cell lung cancer xenografts in athymic mice using a monoclonal antibody (RNL-1) against a neuroendocrine-related antigen.

A mouse monoclonal antibody (RNL-1) was raised against the variant small cell lung cancer (SCLC) cell line NCI-H82. Immunohistochemical studies on frozen sections showed that the antibody was reactive with most SCLC (15 out of 16) and lung carcinoids (six out of seven), while in general adenocarcinomas and squamous cell carcinomas of the lung were negative. Immunocytochemical studies on 29 different cell lines derived from human lung tumours confirmed the neuroendocrine-related expression of the RNL-1 defined antigenic determinant. Immunoelectron microscopy showed that RNL-1 recognises an extracellular membrane domain, concentrated at adhesion sites between adjacent cells. The tissue distribution of the RNL-1 defined antigen was mainly restricted to neural and neuroendocrine tissues. These immunohistochemical data suggest that RNL-1 is directed against a neuroendocrine-related cell adhesion molecule. Being reactive with an epitope expressed on the surface of most neuroendocrine malignant cells, RNL-1 (IgG1 isotype) is a potential vehicle for targeting SCLC in vivo. We evaluated the ability of radiolabelled RNL-1 to localise human SCLC xenografts in nude mice as a first step in determining the in vivo value for radioimmunodetection. RNL-1 was radioiodinated using the Bolton-Hunter labelling technique. Nude mice bearing NCI-H82 xenografts were injected intravenously with the radiolabelled RNL-1 preparations, and animals were dissected 4, 24, 48, 72 and 120 h post injection (p.i.) to determine the biodistribution of the radiolabel. The iodine-125 label accumulated in the tumour up to 48 h p.i. (6.5% injected dose per gram of tissue [ID g-1]), while the label content of the normal tissues decreased with time.(ABSTRACT TRUNCATED AT 250 WORDS)

Biodistribution of a monoclonal antibody (RNL-1) against the neural cell adhesion molecule (NCAM) in athymic mice bearing human small-cell lung-cancer xenografts.

The purpose of this investigation was to determine the targeting potential of the murine monoclonal antibody (MAb) RNL-1 for human small-cell lung cancer (SCLC) in a nude mouse model. RNL-1 is preferentially reactive with SCLC and lung carcinoids, and was classified as a cluster-1 MAb as defined by the International Workshop on Small-Cell Lung-Cancer Antigens. From the intercellular location of the target antigen and its reactivity with 3T3 cells transfected with nucleic acid sequences encoding for the neural cell adhesion molecule (NCAM), it was concluded that RNL-1 is directed against NCAM. RNL-1 was radiolabelled with either 125iodine or 111indium and injected into nude mice bearing NC1-H82 SCLC xenografts. The biodistribution of the radiolabels was determined up to 120 hr post injection. Maximum tumour accretion for 111In-RNL-1 was 11.8%ID/g and 6.5%ID/g for 125I-RNL-1. The accumulation of 111In-RNL-1 could be visualized clearly by gamma scintigraphy without background subtraction techniques. Autoradiographs of whole-body sections from animals injected with 125I-RNL-1 showed that activity in the SCLC xenografts was mainly peripheral, suggesting that tumour uptake is dependent on the vascularization of the tumour tissue.

Novel antigens characteristic of neuroendocrine malignancies.

The authors describe the immunochemical detection, biochemical characterization, and tissue distribution of neuroendocrine antigens recognized by three newly developed monoclonal antibodies (MoAb) obtained after immunization of mice with the variant small cell lung cancer (SCLC) cell line NCI-H82. RNL-1 was reactive with neuroendocrine tissues similar to the SCLC cluster-1 MoAb, known to recognize N-CAM. Antibodies RNL-2 and RNL-3 are directed against different epitopes on the same proteinaceous complex. Both MoAb recognize an intracellularly located, water-soluble antigen which has a subunit composition with a protein triplet ranging in molecular weight between 44 and 45 kilodaltons (kD) next to a component of approximately 30 kD. The antibodies RNL-2 and RNL-3 reacted with a subset of neuroendocrine tissues and neuroendocrine neoplasms. In lung cancer both antibodies reacted only with some SCLC and carcinoids and not with nonneuroendocrine lung carcinomas. The potential diagnostic applicability of antibodies RNL-1, RNL-2, and RNL-3 is discussed.

Cell lines of human oral squamous-cell carcinomas retaining their differentiated phenotype.

Two cell lines from head-and-neck squamous-cell carcinomas (SCC) have been established and characterized. Cell line R105 was derived from a xenografted SCC of the floor of the mouth and cell line T87/rc from a SCC of the epiglottis. Identification of individual cytokeratins 4, 5, 7, 8, 10, 13, 14, 18 and 19 led to the conclusion that both cell types had squamous characteristics and that keratinization occurred in xenografts. Ultrastructurally, junctional complexes were observed in both cell lines. Characteristic marker chromosomes were found and although both cell lines were derived from male patients, the Y chromosome was missing from all examined cells. The basic biological parameters of both cell lines were modal chromosome numbers of 59 (R105) and 60 (T87/rc), a doubling time of 60 (R105) and 45 hr (T87/rc) and a DNA index of 1.54 (R105) and 1.31 (T87/rc). The tumorigenicity of the 2 cell lines was proved by the ability to form colonies on a plastic substratum, as well as in a soft agar assay. Furthermore, the cells could produce multi-cellular tumour spheroids, and formed tumour nodules after subcutaneous inoculation into nude mice. The R105 tumour cells appeared to be better differentiated than the T87/rc as observed by histology and immuno(histo)chemistry. Both cell lines appear to retain SCC differentiation after being xenografted into nude mice, cultured for more than 40 passages in vitro and thereafter again xenografted into nude mice.