1985 Volume 31 Issue 2 Pages 273-279
It was reported in the previous paper that Ca 9-22 SF, which was derived from human gingival carcinoma cells, was established in long-term culture in the serum-free defined medium. Ca 9-22 SF was considered to maintain the character of oral cancer cells, because it was successfully transplantable to the nude mice and the formed nodule was histologically determined as squamous cell carcinoma. It was therefore belived that Ca 9-22 SF might be the most suitable cell to study the substance which affected the growth and differentiation of the oral cancer. As a first step to search for the substance which affected the growth of the oral cancer, the growth factors were examined on the effect on the DNA synthesis of Ca 9-22 SF by the method of the double labeling of radioisotopes, 3H-uridine and 14C-thyrnidine. The following growth factors were used: Epidermal growth factor (EGF, 1 ng/ml-1μg/ml), fi broblast growth factor (FGF, 100 pg/ml-100 ng/ml), platelet derived growth factor (PDGF, 0.005-5 units/ml), insuline (100 ng/ml-100μg/ml) and hydrocortisone (100 ng/ml-100μg/ml). Fetal bovine serum (FBS, 0.01-10%) was used as a control. The growth stimulating efficiency of each growth factor was evaluated by comparing the rate of 14C-thymidine incorporation two days after addition of pre-labeled 3H-uridine. Contrary to expectations, the DNA synthesis of Ca 9-22 SF was significantly suppressed by EGF. This suppressive effect may not be cytotoxic but the mechanism of the growth suppression is unknown at present. FGF and PDGF had no effect on the DNA synthesis of Ca 9-22 SF in the serum-free condition but in the condition containing a small amount of serum (0.5%) they clearly stimulated the DNA synthesis of Ca 9-22 SF. Insuline and hydrocortisone did not have any effect on Ca 9-22 SF. The double labeling technique of radioisotopes was considered to be useful in investigating the substance which affected the growth of the oral cancer.
