Effect of keratinocyte growth factor on the proliferation, clonogenic capacity and colony size of human epithelial tumour cells in vitro

Purpose: The effect of recombinant human keratinocyte growth factor (rHuKGF) on the proliferation, clonogenic capacity and colony size of low-passage human epithelial tumour cells was tested in vitro. Materials and methods: Five tumour cell cultures derived from head and neck squamous cell carcinomas, three cultures derived from pleural effusions of carcinomas of different origin and normal human nasal epithelial cells were analysed in passages 2-4. Expression of FGF7 and its receptor (FGFR2) were determined by the RNase protection assay. Cells were incubated with rHuKGF (10-200 ng ml(-1)) 3 days before or immediately after plating for clonal growth in serum-depleted media. To determine cellular radiosensitivity, single doses of 1-8 Gy X-rays were applied. Colony formation as well as colony size, reflecting the number of cell divisions, was determined after 10-15 days of growth in rHuKGF-treated and control cells. Results: Normal nasal epithelial cells showed a two- to threefold increase in the number of cell divisions due to rHuKGF-treatment. In tumour cell cultures, significant stimulation of proliferation occurred in only one of eight samples. Tumour cells expressed FGF7 mRNA and protein, and low levels of FGFR2 mRNA. The addition of rHuKGF to the medium of the tumour cell cultures influenced neither radiation-induced impairment of proliferation nor clonogenic cell survival. Conclusion: rHuKGF has been shown to ameliorate the radiation tolerance of normal epithelia. The minimum in vitro tumour cell response to rHuKGF compared with normal epithelial cells suggests a potential for selective protection of normal epithelia during radiotherapy. The low FGFR2 expression as well as the FGF7 expression in the tumour cells may contribute to their resistance to rHuKGF treatment.