Figure 4. Co-injection of arrested oral fibroblasts enhanced the tumorigenesis of SAS cells. (a) Co-injection of SAS cells with arrested oral fibroblasts induced larger tumors compared with control oral fibroblast co-injection and SAS alone injection. Injection of arrested oral fibroblasts alone did not induce tumors. (b) Co-injection of OECM-1 cells with arrested oral fibroblasts significantly induced tumorigenesis of the OECM-1 cells, but from days 15 to 23. Injection of OECM-1 alone or OECM-1 and control oral fibroblast co-injection did not induce tumorigenesis. SAS alone injection in this experiment was used as a control (3 mice). Except for SAS injection in (b), values are expressed as means ± SE from 6 mice in each group. The experiments were performed reproducibly. *p < 0.05; **p < 0.01; ***p < 0.001.