Endothelial-cell proliferation in experimental tumours

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Abstract
The proliferation characteristics of vascular endothelium were studied in 131 individual experimental tumors, representing 18 transplanted tumor lines [The lines studied included murine adenocarcinoma cell lines CA AD, CA BAC, CA RH, CA RHF, CA TB, KHH, KHHH, KHI, and KHII. The KHLL and KHU carcinoma cell lines, CA SQD squamous carcinoma cells, the fibrosarcoma lines KHJ, KHTD, and SASF, KHKK rhabdomyosarcoma cells KHAA lymphoma cells, mouse hepatoma cells, and rat RIB5 anaplastic sarcoma cells.] The labeling index (LI) is high in most tumors, with a mean value of 9.0%, regardless of the growth rate of the tumors, or whether different tumor types are considered or individual tumors from within one line are studied in detail. A similar high LI value has been found by others for a human tumor. These high LI values may even underestimate the proliferation in new capillary buds. The high proliferative index of tumor endothelium is in marked contrast with the previously reported low 3HTdR uptake into normal tissue blood vessels. It seems likely that it is the type of new vessels formed that will influence tumor growth rates more than the simple rate of endothelial-cell proliferation. The large difference between the proliferation characteristics of tumor endothelium and normal tissue endothelium, recently identified as a possible approach for tumor therapy, has now been confirmed for a range of animal tumors and a human tumor.