Acidic fgf and egf are involved in the autocrine growth stimulation of a human nasopharyngeal carcinoma cell line and sub‐line cells

The growth of a recently established human nasopharyngeal carcinoma cell line, CG‐1, and 5 randomly selected, single‐cell‐derived sub‐lines in serum‐free medium and in fetal‐bovine‐serum (FBS)‐containing medium was investigated. In basal medium supplemented with insulin, transferrin, fibronectin and high‐density lipoprotein, cell growth was moderately stimulated by aFGF and EGF in a dose‐dependent manner. In contrast, in medium containing as little as 0.5% FBS, most of the stimulatory effect of the aforementioned growth factors observed was masked. Western blotting analysis of the cell lysates and conditioned media showed that CG‐1 and sub‐line cells were all capable of synthesizing and releasing aFGF‐ and EGF‐immunoreactive proteins. The amounts of these 2 growth factors synthesized and released appeared to vary among the parental cell line and sub‐line cells. Moreover, the rate of basal proliferation of these cells appeared to be positively correlated with the amounts of aFGF‐ and EGF‐immunoreactive proteins produced. Addition of the neutralizing antibodies to aFGF and EGF exerted a dose‐dependent suppression on cell growth in medium containing 0.5% FBS. The results suggest a role of aFGF and EGF in autocrine growth stimulation of CG‐1 and sub‐line cells, and may explain the moderate response of these cells to exogenously added aFGF and EGF.