OBJECTIVETo test the hypothesis that malignant tumor metastasis is mediated also through a non-cellular, essentially molecular, mechanism in addition to the cellular pathway.

METHODSThe sex-determining region on the Y chromosome was detected as the marker of the primary tumors using PCR in Lewis lung carcinoma (LLC) in vitro and in female C57BL/6 mice bearing LLC with spontaneous metastasis. The macroscopic and microscopic metastases in the tumor-bearing mice were examined for SRY expression by PCR and in situ hybridization, using the tissues from male and female mice as the positive or negative controls.

RESULTS AND CONCLUSIONPositive SRY gene expression was detected in the metastatic foci in the LLC-bearing female mice, suggesting the origination of these tumor cells from the primary tumor foci. We have failed to verify the non-cellular metastasis hypothesis in this animal experiment, but given the limitations of this experiment, we consider further investigation still necessary for verification of this hypothesis using other methods.