title: Let-7b binding site polymorphism in the B-cell lymphoma-extra large 3'UTR is associated with fluorouracil resistance of hepatocellular carcinoma.
abstract: B-cell lymphoma-extra large (Bcl-xl) is an anti-apoptotic member of the B-cell lymphoma 2 (Bcl-2) family that is often found to be overexpressed in human hepatocellular carcinoma (HCC), therefore conferring a survival advantage to tumor cells. microRNA (miRNA) let-7b is downregulated in HCC and its expression correlates with multidrug resistance. Using computational programs, it was predicted that the 3' untranslated region (UTR) of the Bcl-xl gene contains a potential miRNA binding site for let-7b, and that a single nucleotide polymorphism (SNP) site rs3208684 (A or C allele) resides within this binding site. Luciferase assays and western blot analysis demonstrated that let‑7b targeted Bcl-xl gene expression and negatively regulated the amount of Bcl-xl protein. SNP rs3208684 (A>C) variation enhanced the expression of Bcl-xl by disrupting the binding of let-7b to the 3'UTR of Bcl-xl. The effects of the two polymorphic variants on chemotherapeutic drug sensitivity were determined by cell counting kit 8 assays. Overexpression of the Bcl-xl mutated (C) allele in BEL-7402 HCC cells significantly decreased fluorouracil (5-FU) sensitivity, as compared with mock transfection and overexpression of the wild-type allele. From this, it was concluded that let-7b increased 5-FU sensitivity by repressing Bcl-xl expression in HCC cells. These results suggest that SNP (rs3208684) may be a potential marker for personalized treatment.
authors.affiliation: Institute of Pharmacy and Pharmacology, University of South China, Hengyang, Hunan 421001, P.R. China.
authors.forename: Jin
authors.initials: J
authors.lastname: Ma
authors.affiliation: Institute of Pharmacy and Pharmacology, University of South China, Hengyang, Hunan 421001, P.R. China.
authors.forename: Rui
authors.initials: R
authors.lastname: Guo
authors.affiliation: Institute of Pharmacy and Pharmacology, University of South China, Hengyang, Hunan 421001, P.R. China.
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.affiliation: Institute of Pharmacy and Pharmacology, University of South China, Hengyang, Hunan 421001, P.R. China.
authors.forename: Xia
authors.initials: X
authors.lastname: Pan
authors.affiliation: Institute of Pharmacy and Pharmacology, University of South China, Hengyang, Hunan 421001, P.R. China.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Lei
mesh_terms: D020413:3' Untranslated Regions; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005472:Fluorouracil / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics*; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics*; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D034622:RNA Interference; D051020:bcl-X Protein / Q000737:chemistry / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D000964:Antimetabolites, Antineoplastic; D035683:MicroRNAs; D051020:bcl-X Protein; C487931:mirnlet7 microRNA, human; D005472:Fluorouracil