title: Interaction between APC and Fen1 during breast carcinogenesis.
abstract: Aberrant DNA base excision repair (BER) contributes to malignant transformation. However, inter-individual variations in DNA repair capacity plays a key role in modifying breast cancer risk. We review here emerging evidence that two proteins involved in BER - adenomatous polyposis coli (APC) and flap endonuclease 1 (Fen1) - promote the development of breast cancer through novel mechanisms. APC and Fen1 expression and interaction is increased in breast tumors versus normal cells, APC interacts with and blocks Fen1 activity in Pol-β-directed LP-BER, and abrogation of LP-BER is linked with cigarette smoke condensate-induced transformation of normal breast epithelial cells. Carcinogens increase expression of APC and Fen1 in spontaneously immortalized human breast epithelial cells, human colon cancer cells, and mouse embryonic fibroblasts. Since APC and Fen1 are tumor suppressors, an increase in their levels could protect against carcinogenesis; however, this does not seem to be the case. Elevated Fen1 levels in breast and lung cancer cells may reflect the enhanced proliferation of cancer cells or increased DNA damage in cancer cells compared to normal cells. Inactivation of the tumor suppressor functions of APC and Fen1 is due to their interaction, which may act as a susceptibility factor for breast cancer. The increased interaction of APC and Fen1 may occur due to polypmorphic and/or mutational variation in these genes. Screening of APC and Fen1 polymorphic and/or mutational variations and APC/Fen1 interaction may permit assessment of individual DNA repair capability and the risk for breast cancer development. Such individuals might lower their breast cancer risk by reducing exposure to carcinogens. Stratifying individuals according to susceptibility would greatly assist epidemiologic studies of the impact of suspected environmental carcinogens. Additionally, a mechanistic understanding of the interaction of APC and Fen1 may provide the basis for developing new and effective targeted chemopreventive and chemotherapeutic agents.
authors.affiliation: Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, United States. Electronic address: snarayan@ufl.edu.
authors.forename: Satya
authors.initials: S
authors.lastname: Narayan
authors.affiliation: Department of Medicine, University of Florida, Gainesville, FL 32610, United States.
authors.forename: Aruna S
authors.initials: AS
authors.lastname: Jaiswal
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, University of Florida, Gainesville, FL 32610, United States.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Law
authors.affiliation: Department of Medicine, University of Florida, Gainesville, FL 32610, United States; Malcom Randall VA Medical Center, Gainesville, FL 32608, United States.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Kamal
authors.affiliation: Department of Pharmacology, Penn State Cancer Institute, Penn State College of Medicine, Hershey, PA 17033, United States.
authors.forename: Arun K
authors.initials: AK
authors.lastname: Sharma
authors.affiliation: Department of Medicine, University of Florida, Gainesville, FL 32610, United States.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Hromas
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000378:metabolism*; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D063646:Carcinogenesis; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D045585:Flap Endonucleases / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D004247:DNA; D045585:Flap Endonucleases
keywords: Adenomatous polyposis coli; Base excision repair; Breast cancer development; Environmental carcinogens; Flap endonuclease 1; Mortality