8-METHOXYPSORALEN INDUCED ALTERATIONS OF MAMMALIAN-CELLS

In vitro and in vivo assays demonstrate that 8-methoxypsoralen, in the presence of ultraviolet light (8MOP-UV), induces phenotypic alterations in certain mammalian cells. Transformation for certain growth characteristics occurred in high percentages of 8MOP-UV treated primary mouse, rat, and hamster embryo cultures, and in continuous cell lines (BHK21/CL13, NIH/3T3, and Balb/c 3T3). Morphological alterations were observed at both macroscopic (focus formation) and microscopic (random growth patterns, multilayering, etc.) levels of examination. Treated cells which demonstrated altered phenotypes were tested for growth in soft agarose. Those cultures with altered morphology and whose cells grow in soft agarose, were, in addition, tested for murine leukemia virus (MuLV) production by the XC cytopathogenicity test. 8MOP-UV transformed mouse, rat, and hamster (except BHK21/Clone13) cells produced positive XC results. Fluorescent antibody tests of those cells which produced giant cell cytopathogenicity were positive. Cytoplasmic fluorescence was observed when these cells were tested with antisera to oncornavirus group specific (gs-3) antigen. Control nontreated cells were negative in all experiments. Hamster embryo fibroblasts transformed with 8MOP-UV, acquired apparent unlimited in vitro growth characteristics (> 150 population density levels); they exhibited mixoploidy; small numbers of these cells caused spindle cell sarcomas in hamster check pouches, and produced tumors in newborn hamsters; and their generation times x̄ = 22.5 hr) were characteristic of transformed cells. Expression of altered growth characteristics by BHK21/Cl13 cells may be related to selection for cytotoxic resistant cells rather than being caused by 8MOP-UV induced transformation.