Human amnion and lung tissue culture systems for possible detection and study of human RNA tumor viruses

A human lung and an amnion cell line were identified as highly susceptible to transformation by the rhabdomyosarcoma-114 (RD-114) virus pseudotype of murine sarcoma virus (MSV). MSV transformation on these two cell lines demonstrated a) "one-hit" kinetics with an MSV stock which contained a 100-fold excess of MSV over its detectable associate RD-114 helper virus and b) only a slight increase (2X) in focus-forming titers by the addition of optimal concentrations of RD-114 helper virus. These findings indicated that the primary MSV interaction with those amnion and lung cells was that of non-productive transformation; and this was confirmed by the isolation of sarcoma-positive leukemia (helper) virus-negative (S+Lminus) cells from cloned terminal foci of MSV transformed human amnion and lung cells. These MSV-susceptible human cell lines are the first human cells identified as capable of demonstrating the defective nature of MSV. Human candidate oncornaviruses have not, however, been detected to date with the use of normal lung and amnion cells and their S+Lminus derivatives as indicator systems. These cell lines were useful for the isolation and identification of a new RD-114-like virus from a cat cell line.