Loss of basal cell phenotype with acquisition of lung-colonizing capability in mouse mammary tumors.

A transplantable pregnancy-dependent mouse mammary tumor, TPDMT-4, and its ovarian-dependent (T4-OR26) and autonomous (T4-OI96, T4-OI145, T4-OI165, T4-OI320 and T4-OI320CY) sublines were examined immunohistochemically for the expression of keratin 14 and type IV collagen. T4-OI96, T4-OI145, and T4-OI165, but not T4-OR26, T4-OI320, or T4-OI320CY, formed lung colonies (metastasis) after intravenous injection as a single-cell suspension. Despite the similar morphology of TPDMT-4 and its six sublines, only TPDMT-4 and the nonmetastatic sublines revealed a basal cell phenotype as defined by keratin 14 expression. Staining for type IV collagen was complete at the peripheries of the glandular structures in TPDMT-4 and nonmetastatic sublines but was patchy in the metastatic tumors.