Effects of keratinocyte growth factor on the proliferation and radiation survival of human squamous cell carcinoma cell lines in vitro and in vivo.
OBJECTIVE
Keratinocyte growth factor (KGF) has potent mitogenic activity on normal epithelial cells and has been found to enhance intestinal crypt cell survival in irradiated mice and to prevent radiation and chemotherapy-induced mucositis in animal models. The purpose of the study reported here is to investigate the effect of recombinant human KGF on the proliferation and survival of human squamous carcinoma cell lines following irradiation.


METHODS
The level of KGF receptor (KGFR) mRNA in normal Balb/Mk cell line and human head and neck squamous carcinoma cell lines was assessed using a RNase protection assay. The clonogenic assay and MTT assay were used to study the proliferative effects of KGF on human tumor cell lines and Balb/MK cell line in vitro. Effects of KGF on in vivo tumor growth and radiosensitivity were studied in three KGFR-positive human squamous cell carcinoma xenografts (FaDu, Detroit 562 and A431) in nude mice, and a murine KGFR-negative melanoma tumor (B16) in Balb/c mice.


RESULTS
Seven of 10 tumor cell lines studied expressed KGFR mRNA. None of these tumor cell lines showed enhanced proliferation when exposed to KGF for 2 days or less. Prolonged exposure to KGF for 7 days or longer resulted in low level stimulation of proliferation in both clonogenic and MTT assays in four of seven KGFR-positive cell lines. Two KGFR-negative cell lines also had a low proliferative response to KGF in a clonogenic assay, but not in the MTT assay. Normal keratinocyte Balb/MK cells, which expressed a moderate level of KGFR mRNA, had a strongly proliferative response to KGF. Its KGF enhancement ratio (KER) of plating efficiency was 24-70 times higher than that of the tumor cells studied (p < 0.001). The KGF-stimulated tumor cell growth was almost completely inhibited by heparin or epidermal growth factor (EGF). There were no significant differences (p > 0.05) in the survival of any of tumor cell lines in the presence or absence of KGF (100 ng/ml) irradiated with doses of 0-15 Gy, and no significant differences (p > 0.05) between the radiobiological parameters D0, Dq, and n number from the SHMT model, alpha, beta, and alpha/beta ratio from the LQ model and SF2 for radiation survival curves for cell lines irradiated in the presence or absence of KGF. Three KGFR-positive human squamous cell carcinoma xenografts in nude mice, and a murine KGFR-negative melanoma tumor in Balb/c mice treated with 1.0 mg/kg of KGF for 3 days grew at the same rate as in untreated mice.


CONCLUSIONS
The recombinant human KGF resulted in little or no stimulation of the proliferation of human head and neck squamous tumor cell lines and did not affect the radiosensitivity of these cell lines in vitro and in vivo. Therefore, KGF may be of clinical value in preventing radiation-induced mucositis and may have the potential to increase the therapeutic index of radiotherapy for treatment of cancers.
Ning
S
S
Department of Radiation Oncology, Stanford University Medical Center, CA 94305-5105, USA.
Shui
C
C
Khan
W B
WB
Benson
W
W
Lacey
D L
DL
Knox
S J
SJ
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects* / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D051526:Fibroblast Growth Factor 10; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D012333:RNA, Messenger / Q000378:metabolism; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor; D017978:Receptors, Growth Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects
C496453:FGF7 protein, human; C496454:Fgf7 protein, mouse; D051526:Fibroblast Growth Factor 10; D006133:Growth Substances; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D017978:Receptors, Growth Factor; D011994:Recombinant Proteins; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor