Cell contacts and surface features of three murine tumors grown as multicellular spheroids

Ultrastructural observations using scanning and transmission electron microscopy were made on three murine tumors, line 1 lung carcinoma, fibrosarcoma (FSA) and mammary carcinoma MCa-11, grown in vitro as multicellular tumor spheroids (MTS). The cytology of these MTS revealed the presence of characteristic cellular organelles as well as varying amounts of intracisternal type-A viral particles. In line 1 and FSA, the occurrence of gap junctions in the outer shells of these MTS was correlated with the growth behavior of these spheroids. In FSA, extracellular collagen bundles were identified next to tumor cells and represent synthetic activity by these cells under these conditions. No specific cytological correlations were made with the slow growing MCa-11 spheroid.