Early Detection of Genotoxic Urinary Bladder Carcinogens by Immunohistochemistry for γ-H2AX.
DNA double-strand breaks (DSBs) induced by exposure to genotoxic agents are known to cause genome instability and cancer development. To evaluate the applicability of γ-H2AX, a sensitive marker of DSBs, in the early detection of genotoxicity and carcinogenicity of chemicals using animal models, we examined γ-H2AX expression in urinary bladders of rats. Six-week-old male F344 rats were orally treated for 4 weeks with a total of 12 chemicals divided into 4 categories based on genotoxicity and carcinogenicity in the urinary bladder. Animals were sacrificed at the end of administration or after 2 weeks of recovery, and immunohistochemistry for γ-H2AX was performed. At week 4, γ-H2AX expression in bladder epithelial cells was significantly increased by all 4 genotoxic bladder carcinogens as compared with the controls, whereas the 3 chemicals that were genotoxic but not carcinogenic in the bladders did not cause upregulation of γ-H2AX. After the recovery period, γ-H2AX expression was markedly reduced in all groups but remained significantly elevated in rats treated with 3 of the 4 genotoxic bladder carcinogens. Although slight increases in γ-H2AX expression were induced by a weak bladder carcinogen with equivocal genotoxicity (phenethyl isothiocyanate) and 2 nongenotoxic bladder carcinogens (melamine and uracil) at week 4, these differences were not significant and were thought to be associated with activated proliferation by urothelial hyperplasia, as demonstrated by increased Ki67-positive cells. These results suggested that γ-H2AX may be a potential biomarker for the early detection of genotoxic bladder carcinogens.
*Division of Pathology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501; t-toyoda@nihs.go.jp.
Takeshi
T
Toyoda
*Division of Pathology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501;
Young-Man
YM
Cho
*Division of Pathology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501;
Jun-Ichi
J
Akagi
*Division of Pathology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501;
Yasuko
Y
Mizuta
*Division of Pathology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501; Graduate School of Pharmaceutical Sciences, Showa University, Shinagawa-ku, Tokyo 142-8555; and.
Tadashi
T
Hirata
Biological Safety Research Center, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501, Japan.
Akiyoshi
A
Nishikawa
*Division of Pathology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501;
Kumiko
K
Ogawa
D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D055088:Early Detection of Cancer / Q000379:methods*; D006657:Histones / Q000378:metabolism*; D006965:Hyperplasia; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D009152:Mutagenicity Tests / Q000379:methods*; D010750:Phosphoproteins / Q000378:metabolism*; D011237:Predictive Value of Tests; D011916:Rats, Inbred F344; D013997:Time Factors; D015854:Up-Regulation; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced* / Q000378:metabolism* / Q000473:pathology
D014408:Biomarkers, Tumor; D006657:Histones; D019394:Ki-67 Antigen; D010750:Phosphoproteins; C577575:gamma-H2AX protein, rat
carcinogenicity; genotoxicity; rat; urinary bladder; γ-H2AX