In vitro angiogenic activity of RNA from leukemic lymphocytes

RNA was extracted from leukemic lymphocytes by a fluorocarbon method, and primary cultures of human amniotic cells were exposed to the lymphocyte RNA. Angioid tubular and cordon-like structures in branching out and criss-cross patterns with budding ends developed in these cultures within 7 to 12 days of the first exposure. Although there was no opportunity to study preparations from nonleukemic lymphocytes, extracts of normal peripheral blood cells and blood rich in granulocytes had no angiogenic effects. In view of the recent renewal of interest in tumor and tissue angiogenic factor as well as in angiogenic activity by transformed lymphocytes, in addition to the intriguing angioblastic component of Lukes-Rappaport immunoproliferative syndromes, this work may point to the ribonucleic acid nature of the vessel-forming principle. Various cell-differentiating properties of RNA preparations have been repeatedly described, and thus it is not altogether surprising that lymphocyte angiogenic factor may originate in RNA.