In vivo Invasion Assay and Enhancement of Differentiation of Low Passage Cultured Cells Derived from Human Non-Small Cell lung Carcinoma Using De-epithelialized Rat Tracheas Transplanted into Nude Mice.

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The investigation of human tumors using nude mouse xenograft is capable of taking into account the host reactions, whereas this is impossible in in vitro system. Nude mice offer an invasion environment similar to that of humans; however, s.c. injection procedures for conventional xenotransplantation into nude mice have encountered problems with regard to long latency periods low tumor take rates. In this project, human lung tumor-derived cell lines with low passage generation were transplanted into nude mice to determine their growth behavior and invasive potential. Six cell lines were inoculated into deepithelialized rat tracheas (5 x 10^5 cells/trachea). After cell inoculation, the tracheas were sealed and transplanted into the subcutis of nude mice. In a parallel experiment, these cell lines (1 x 10^6 cells) were injected s.c. In the subcutis, the tumor take rate was only 13% with a long latency period of 18 weeks, and 3 cell lines did not show any invasive growth to the surrounding … More tissue. In rat tracheas, all cell lines proliferated within 3 weeks, and 4 of them showed invasive growth to the tracheal wall within 1-2 weeks. Cells growing in the tracheal wall showed higher (^3H) thymidine labeling indexes and greater atypia, such as larger nuclei and prominent nucleoli, than those in the tracheal lumen. The s.c. tumor take rate correlated with the incidence of invasive growth to the tracheal wall. The survival of the patients originally bearing the six tumors also correlated closely with the invasive potential of this system. In tracheal transplants, all cell lines showed comparable or higher degree of differentiation than in the primary lesion. While most cell lines showed lower degree of differentiation in the mouse subcutis. The surfaces of tracheal transplants repopulated with the cells derived form squamous cell carcinomas were initially lined by a layer of flattened cells 2 to 3 cells thick. While those repopulated with the cells from 3 cases of adenocarcinoma were initially lined by simple epithelia consisted of cuboidal-, round-, and columnar-shaped cells, respectively. Thereafter, those cell lines revealed pseudostratified pattern, papillary growth pattern, and cribriform pattern, respectively. Ultrastructurally, they showed structures resembling ciliated bronchial epithelial cells, non-ciliated bronchiolar epithelial cells, and bronchial goblet cells, respectively.These results indicate that the system using low passage cell lines can evaluate the invasive potential shortly after the inoculation; of a relatively small number of cells and can be used as a clinically reliable biological invasion assay. And, histological examination of cultured cells using this system was considered to be advantageous for evaluation of differentiation because it provided unique proliferation patterns unobserved in primary tumors or tumors formed after subcutaneous direct cell injections. Less