Establishment and immunologic characterization of 3-methylcholanthrene-induced sarcoma cell lines metastasizing widely in mice and exhibiting distinct and selective propensities for the mode of metastasis.

Successive transplantations of metastatic secondary tumors of a 3-methylcholanthrene-induced sarcoma in (C57BL/Ka X C3H/He)F1 male and female syngeneic mice resulted in the establishment of two unique tumor cell lines with enhanced metastatic potential. Moreover, each line showed distinct and selective propensities for the mode of metastasis. The 1101Pn tumor line, obtained by successive transplantations of metastatic pulmonary nodules, metastasized to many visceral organs via the bloodstream. Another tumor line, 1101Ln, selected by repeated transplantations of lymph node metastases, metastasized to almost all lymph nodes and to the lungs. When the metastatic pulmonary tumor of mice bearing 1101Ln was subcutaneously implanted on the backs of syngeneic mice, the tumor grew locally and eventually metastasized via the lymphatics, with systemic involvement of the lymph nodes. This finding is an indication that the intrinsic properties of tumor cells that form pulmonary metastases in 1101Ln tumor-bearing mice are distinct from those in 1101Pn tumor-bearing mice in terms of metastatic mode. The 1101Pn and 1101Ln tumor lines were nonimmunogenic or less immunogenic than the 505 tumor (the parental, nonselected tumor line). The growth and metastatic action of 505 tumors were enhanced by 400 R whole-body X-radiation, but no such effect was seen with 1101Pn tumors. Pretreatment of mice with OK-432, an immunopotentiator, retarded the growth and metastasis of 505 tumors but exerted little or no effect on 1101Pn tumors. The experimental results suggest that a tumor is composed of a heterogeneous cell population with respect to metastatic potential, metastatic mode, and tumor immunogenicity and that some intrinsic properties of the tumor cell have a primary role in the determination of the mode of cancer metastasis.