Fund Laboratories, Lincoln's Inn Fields, London WC2A 3PX,

SUMMARY-The transformation of an epithelial-like Sprague-Dawley rat line (RL) by the Harvey strain of murine sarcoma virus (MSV-H) was studied. The transformed cells were fibroblastic. Two types of transformed clones were isolated with respect to virus release: one releasing virus im-munologically similar to MSV-H, and the other releasing no virus detectable by infectivity or 3H-uridine labeling. The nonproducer transformed cells developed into sarcomas in newborn Sprague-Dawley rats.-J Natl Cancer Inst 49: 379-386, 1972. DESPITE THE fact that most human tumors arise from epithelial tissues, there have been few studies on viral transformation of epithelial-like cells in culture. Most transformation studies used either primary embryo cultures, which contain a mixture of cell types, or the fibroblastic cell lines 3T3 or BHK2l (1, 2). Transformed BHK2l cell