UNCORRECTED PROOF BIOLOGY CONTRIBUTION POST-TREATMENT WITH AN FGF CHIMERIC GROWTH FACTOR ENHANCES EPITHELIAL CELL PROLIFERATION TO IMPROVE RECOVERY FROM RADIATION-INDUCED INTESTINAL DAMAGE Q1 FUMIAKI NAKAYAMA, M.D., PH.D.,* AKIKO HAGIWARA, B.S.,* SACHIKO UMEDA, B.S.,* MASAHIRO ASADA,PH.D., y MEGUMI GOTO, M.S., y JUNKO OKI, M.S., y MASASHI SUZUKI,PH.D., y TORU IMAMURA,PH.D., y AND MAKOTO AKASHI, M.D., PH.D.* Q2 ) Department of Radiation Emergency Medicine, National Institute of Radiological Sciences, Chiba, Japan, and y Signaling Molecules Research Group, Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology Purpose: A fibroblast growth factor (FGF) 1–FGF2 chimera (FGFC) was created previously and showed greater structural stability than FGF1. This chimera was capable of stimulating epithelial cell proliferation much more strongly than FGF1 or FGF2 even without heparin. Therefore FGFC was expected to have greater biologic activity in vivo. This study evaluated and compared the protective activity of FGFC and FGF1 against radiation-induced intestinal injuries. Methods and Materials: We administered FGFC and FGF1 intraperitoneally to BALB/c mice 24 h before or after total-body irradiation (TBI). The numbers of surviving crypts were determined 3.5 days after TBI with gamma rays at doses ranging from 8 to 12 Gy. Results: The effect of FGFC was equal to or slightly superior to FGF1 with heparin. However, FGFC was signif- icantly more effective in promoting crypt survival than FGF1 (p < 0.01) when 10 mg of each FGF was administered without heparin before irradiation. In addition, FGFC was significantly more effective at promoting crypt survival (p < 0.05) than FGF1 even when administered without heparin at 24 h after TBI at 10, 11, or 12 Gy. We found that FGFC post-treatment significantly promoted 5-bromo-2 0 -deoxyuridine incorporation into crypts and increased crypt depth, resulting in more epithelial differentiation. However, the number of apoptotic cells in FGFC- treated mice decreased to almost the same level as that in FGF1-treated mice. Conclusions: These findings suggest that FGFC strongly enhanced radioprotection with the induction of epithelial proliferation without exogenous heparin after irradiation and is useful in clinical applications for both the preven- tion and post-treatment of radiation injuries. Ó 2010 Elsevier Inc. Chimeric protein, Fibroblast growth factor, Intestine, Proliferation, Radiation damage. INTRODUCTION Many possible medications have been reported for the treat- ment of gastrointestinal (GI) syndrome (Table E1) (1–32); however, treatment of GI syndrome is still very difficult Q4 . Recently, several fibroblast growth factors (FGFs) (FGF1, FGF2, FGF4, FGF7, and FGF10) have been found to be able to protect against radiation-induced intestinal damage. The fibroblast growth factor receptor (FGFR) family com- prises four receptor tyrosine kinases designated as FGFR1, FGFR2, FGFR3, and FGFR4 (33). Alternative splicing of FGFRs is critical for FGF–FGFR specificity. In particular, FGF receptor 2 IIIb (FGFR2b), the so-called keratinocyte growth factor receptor, may play an important role in intesti- nal tissue repair because it is expressed only in epithelial cells. Fibroblast growth factor 1 is able to not only activate all of the known tyrosine kinase FGFR subtypes but also bind to FGFR2b with high affinity. In addition, the profiles of FGFR expression in the intestine seem to favor FGF1 sig- naling (11). On the other hand, FGF2 shows a somewhat lim- ited receptor specificity and is not able to bind to FGFR2b, so FGF2 can exert few direct effects on epithelial cells (34). Therefore the wide spectrum of FGF1 activity makes it an ideal FGF for the treatment of radiation injuries (11). However, the structural instability of wild-type FGF1 and its dependence on exogenous heparin for optimal activity limit its potential for practical use (35). Fibroblast growth Reprint requests to: Fumiaki Nakayama, M.D., Ph.D., Depart- ment of Radiation Emergency Medicine, National Institute of Ra- diological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan. Tel: (+81) 43-251-2111; Fax: (+81) 43-206-4094; E-mail: f_naka@nirs.go.jp This work was carried out as part of the Research Project for High-Dose Radiation Injuries at the National Institute of Radiolog- ical Sciences and was also funded partly by the Budget for Nuclear Research of the Ministry of Education, Culture, Sports, Science and Technology of Japan. Supplementary material for this article can be found at www.red- journal.org. Conflict of interest: none. Q3 Received June 11, 2009. Accepted for publication April 29, 2010. 1 FLA 5.0 DTD  ROB19215_proof  7 June 2010  3:01 pm  ce OK Int. J. Radiation Oncology Biol. Phys., Vol. -, No. -, pp. 1–9, 2010 Copyright Ó 2010 Elsevier Inc. Printed in the USA. All rights reserved 0360-3016/$–see front matter doi:10.1016/j.ijrobp.2010.04.045 ARTICLE IN PRESS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71