Decreased Expression of Retinoid X Receptors During Human and Azoxymethane-induced Colorectal Carcinogenesis in the Rat.
OBJECTIVE
The family of retinoid X receptors (RXRs) including RXRα, β and γ, is involved in regulating cell proliferation, differentiation, apoptosis and development.


METHODS
In order to characterize the role of RXRs during colorectal carcinogenesis, the expression of RXRs in human and azoxymethane (AOM)-induced rat colorectal tumors was profiled by immunohistochemistry.


RESULTS
Both human and rat normal colorectal epithelia and hyperplasia exhibited strong nuclear, but weak cytoplasmic staining for all three proteins. Expression of RXRα, β and γ was significantly reduced in rat carcinomas compared to high-grade dysplasia whether in aberrant crypt foci or in adenomas. All three proteins displayed dramatically reduced nuclear expression in both human adenomas and carcinomas. Reduced expression of RXRα and RXRγ seems more significant than RXRβ in both human and rat carcinomas.


CONCLUSIONS
Reduced expression of RXRs is associated with colorectal carcinogenesis in both humans and AOM-treated rats.
Susan Lehman Cullman laboratory for Cancer Research, Department of Chemical Biology, Earnest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, U.S.A. xhao@mail.nih.gov.
Xingpei
X
Hao
Susan Lehman Cullman laboratory for Cancer Research, Department of Chemical Biology, Earnest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, U.S.A.
Hang
H
Xiao
Susan Lehman Cullman laboratory for Cancer Research, Department of Chemical Biology, Earnest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, U.S.A.
Jihyueng
J
Ju
Laboratory of Pathology, National Cancer Institute, Bethesda, MD, U.S.A.
Stephen M
SM
Hewitt
Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, Rockville, MD, U.S.A.
Herbert C
HC
Morse
D000818:Animals; D001397:Azoxymethane; D015179:Colorectal Neoplasms / Q000139:chemically induced / Q000737:chemistry* / Q000209:etiology; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry; D051381:Rats; D011916:Rats, Inbred F344; D047488:Retinoid X Receptors / Q000032:analysis*
D047488:Retinoid X Receptors; D001397:Azoxymethane
RXRs; carcinogenesis; colonic cancer; immunohistochemistry