Deregulation of the cyclin D1/Cdk4 retinoblastoma pathway in rat mammary gland carcinomas induced by the food-derived carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a suspected human breast carcinogen found in cooked meat that induces mammary gland cancer in rats. By real time PCR analysis, PhIP-induced rat mammary gland carcinomas showed statistically higher expression of the G(1)-S cyclin D1 (5-fold) and its kinase partner cyclin-dependent kinase (Cdk)-4 (37-fold) in comparison with normal mammary gland, whereas cyclin D2, cyclin D3, and Cdk6 were not statistically changed. Amplification of cyclin D1 was observed by real time PCR in 24% of carcinomas (15 of 63). Only 1 of 47 carcinomas showed Cdk4 amplification. By Western blotting, the level of phospho-Rb was >2-fold higher in carcinomas than in normal mammary gland. By immunohistochemical analysis, cyclin D1, Cdk4, and phospho-Rb nuclear protein expression was 5.7-, 3.9-, and 2.3-fold higher, respectively, in carcinomas than in normal mammary gland, whereas the expression of cyclin D2, cyclin D3, and Cdk6 was similar. Among carcinomas, Cdk4 and phospho-Rb levels were positively correlated with cell proliferation. Previous studies by this laboratory indicated that these carcinomas harbor a high frequency of H-ras mutations. The H-ras pathway is linked to the cell cycle via cyclin D1. The results from the current study implicate cyclin D1/Cdk4, phospho-Rb as a central pathway in PhIP-induced rat mammary gland carcinogenesis.
Qiu
Cunping
C
Chemical Carcinogenesis Section, Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Health of Institutes, Bethesda, Maryland 20892-4262, USA.
Shan
Liang
L
Yu
Minshu
M
Snyderwine
Elizabeth G
EG
D000818:Animals; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005784:Gene Amplification / Q000187:drug effects; D007093:Imidazoles / Q000633:toxicity*; D007150:Immunohistochemistry; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D016160:Retinoblastoma Protein / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D002273:Carcinogens; D007093:Imidazoles; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D019938:Cyclin D1; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; C495903:Cdk4 protein, rat; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases