Fig. 1.

Bacterial enterotoxin ST potentiates Ca²⁺_o-mediated cytostasis in colorectal cancer cells. (A) Dose responses of cytostasis by Ca²⁺_o in various human colon carcinoma cells. ^†P < 0.01 versus control for Caco-2 cells; ^#P < 0.05 and ^##P < 0.01 versus respective controls in each of the three cell lines. (B) Absence of cytotoxicity by Ca²⁺_o in human colon cancer cells. Cytotoxicity was assessed as the proportion of tumor cells identified by flow cytometry in the sub-G₁ fractions, which correspond to cells undergoing apoptosis or necrosis, of the cell cycle. Data are mean ± SEM from three independent experiments. (C1) Concentration dependence of T84 cell proliferation on Ca²⁺_o in the presence or absence of 1 μM ST. Results in (A) and (C1) are expressed as the percentage of respective control incubations treated with 1 mM Ca²⁺_o. *P < 0.05 and **P < 0.01, comparing respective conditions treated with Ca²⁺_o alone and Ca²⁺_o plus ST for 24 h. In (C2), data obtained in (C1) are expressed as {100 − [(condition treated with ST plus Ca²⁺_o)/(respective control condition treated with Ca²⁺_o alone) × 100]}.