Site-induced differences in spontaneous metastasis of MO4 mouse fibrosarcoma cells.

MO4 mouse fibrosarcoma cells metastasized to the lungs and to the regional lymph nodes from a subcutaneous tumour in the pinna when they were derived from a tumour in the tail or from lung metastases. In contrast, no metastases were found when MO4 cells were derived from a tumour in the pinna or from the parent cell line. Cells from tumours in the pinna produced metastatic tumours when they were implanted in the tail but not in the pinna.

Invasiveness and tumorigenicity of MO4 mouse fibrosarcoma cells pretreated with microtubule inhibitors.

MO4 cell aggregates with a diameter of 0.3 mm produced invasive fibrosarcomas after s.c.

Influence of implantation site on formation of metastases.

It has been suggested that local factors at the site of growth of a primary tumor might influence the outcome of the metastatic process. Compilation of the data from the literature revealed that growth of tumor cells in the selective medium of the intraperitoneal cavity, of the lymph node and/or of the spleen leads to progression towards a population of cells with a higher metastatic capacity. In search for an experimental model with transplantable rodent tumors that could be used to study the influence of the anatomic site of an implant on the formation of spontaneous metastases, we have considered heterogeneity of microenvironmental conditions in the subcutaneous milieu.

Influence of implantation site of MO4 cell aggregates on the formation of metastases.

Implantation of spheroidal aggregates of virally transformed MO4 fibroblastic cells into the pinna or into the tail of syngeneic C3H mice in matched experiments produced invasive fibrosarcomas in all animals. The growth rate of primary tumours was lower in the tail than in the pinna. Histology revealed no differences between tumours at both sites of implantation.

Invasion of malignant cells in vivo and in vitro: similarities and differences.

Progressive occupation of other tissues, accompanied by degeneration of these tissues indicates tumour invasiveness. Tumour cells presumed to be invading show alterations in shape, produce irregular cytoplasmic extensions, contain microfilament bundles and heterophagosomes. Confrontation of malignant cells with fragments of normal tissues in threedimensional culture produces pictures of invasion that would allow the pathologist to recognize that the tumour cells are malignant.