Epithelial cell junctions in primary and metastatic mammary tumors of mice
Pitelka, D.R.; Hamamoto, S.T.; Taggart, B.N.
Cancer Research 40(5): 1588-1599
1980
ISSN/ISBN: 0008-5472 PMID: 6245797 Document Number: 155168
Spontaneous pulmonary metastases of mammary adenocarcinomas in mammary tumor virus-infected mice were compared with primary tumors, hyperplastic alveolar nodules and normal mammary gland with respect to histological pattern, cell-cell relations in primary culture and the ultrastructure and distribution of epithelial cell junctions. Metastases were detected at autopsy and histologically confirmed in 69 of 160 females examined from 7 strains. No characteristic differences were found between primary tumors in mice with and without metastases or between primary and metastatic tumors. Histologically, all 3 types ranged from alveolar to anaplastic; in culture, all formed contact-inhibited epithelial pavements. Freeze-fracture replicas of tumor tissue consistently revealed tight-junction belts, resembling those of nonlactating normal mammary cells, between cells lining alveolar or cystic lumina. A novel feature of the tumors was the presence of microlumina, not detectable histologically, in solid and anaplastic regions; cells forming microlumina were joined by short but complete tight junctions. Also different from normal was the common occurrence of macular tight junctions, close to and distant from tight-junction belts. The abundance of belt and spot desmosomes varied widely. Gap junctions were about as common as in the normal gland. The propensity of malignant cells to form tight and other junctions indicates retention, with relatively moderate distortion, of a fundamental epithelial property. Since all of the junctions are adhesive, their abundance and wide distribution constitute strong evidence that reduced adhesive capacity is not a necessary correlate of epithelial cancer.