Enhancement of Radiation Injury in Human Colon Tumor Cells by the Maturational Agent Sodium Butyrate (NaB)

Two subpopulations of human colon tumor cells (clones A and D) which differ in their intrinsic sensitivity to X irradiation were grown for several passages in tissue culture medium containing the differentiation-inducing agent sodium butyrate (NaB, 2 mM). Values of the single-hit, multitarget survival curve parameters for non-NaB-treated clone A cells were n = 17.1, D0(Gy) = 0.81, and DQ(Gy) = 2.31; corresponding parameters for NaB-treated cells were 1.04, 1.16, and 0.05. For non-NaB-treated clone D cells, the survival parameters were n = 4.27, D0 = 1.05, and DQ = 1.52; corresponding parameters for NaB-treated cells were 1.19, 1.15, and 0.20. The large reduction in the DQ parameters of both clone A and D cells after NaB treatment indicates that sodium butyrate-induced cell maturation is accompanied by increase in radiation cell kill, particularly in the low-dose region of the survival curve.