CORRELATION BETWEEN THE RADIOSENSITIVITY IN-VITRO OF CLONES AND VARIANTS DERIVED FROM A HUMAN-MELANOMA CELL-LINE AND THEIR SPONTANEOUS METASTATIC POTENTIAL IN-VIVO

With an experimental model of spontaneous lung metastases of human mel anoma in immunosuppressed newborn rats, a large panel of clones and va riants with different metastatic potential were derived from a single human melanoma parental cell line (M4Be). Seven clones and variants fr om M4Be were selected, respectively, for their low (parental, clone 1) , intermediate (clones 2 and 3, subvariant 1-) and high (variant 1, su bvariant 1+, clone 4) metastatic potential. This paper investigates th e relationship between the in vivo metastatic potential of the eight c ell lines and their sensitivity to ionizing radiation in vitro (range 0.05-7 Gy). The radiosensitivity was estimated from the mean inactivat ion dose, a parameter equal to the area under the survival curve plott ed in linear coordinates. Examination of the eight survival curves, ob tained with cells cultured for no more than five passages after defros t, shows that clone 1, subvariant 1- and the M4be parental line are th e most radioresistant cells, clone 4 and subvariant 1+ are the most ra diosensitive cells, while clones 2 and 3 and variant 1 showed an inter mediate response to radiation. The metastatic potential in vivo of the parental line and the seven sublines is significantly correlated to t heir radiosensitivity in vitro: the higher the metastatic potential, t he higher the radiosensitivity.