LOSS OF TUMORIGENICITY WITH SIMULTANEOUS CHANGES IN RADIOSENSITIVITY AND PHOTOSENSITIVITY DURING INVITRO GROWTH OF L5178Y MURINE LYMPHOMA-CELLS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 43  (10) , 4736-4742
Abstract
Murine leukemic lymphoblasts L5178Y-R (LY-R) undergo conversion into their L5178Y-S (LY-S) variant as a result of prolonged (5 mo. to 4 yr) cultivation in vitro. LY-R cells are highly tumorigenic in DBA/2 mice; resistant to X-rays [D0 (mean lethal dose [reciprocal of the slope of the linear portion of dose-survival curve]) = 0.91 grays]; and sensitive to UV radiation (D0 = 0.7 J/m2), short (up to 60 min) heat (43.degree. C) treatment, and certain potential cancer drugs. LY-S cells are practically nontumorigenic in DBA/2 mice; sensitive to X-rays (D0 = 0.56 grays); and resistant to UV radiation (D0 = 5.5 J/m2), short heat treatment, and the drugs. the differences in sensitivity of these 2 cell strains to physical and chemical agents are paralleled by differences in DNA repair efficiency. Although both strains can be cloned in soft agar, LY-S cells invariably show higher plating efficiencies. In vitro mean doubling times are 12-15 h and .apprx. 10 h for LY-R and LY-S cells, respectively. The actual loss of tumorigenicity and changes in radio- and photosensitivity associated with conversion of LY-R cells into LY-S cells occur within a short time. These changes (and probably other phenotypic changes mentioned above) result from a single event or from several events occurring within a relatively short time elicited by in vitro culture conditions.