Adenosine triphosphate-binding cassette transporter genes up-regulation in untreated hepatocellular carcinoma is mediated by cellular microRNAs

Abstract

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters are drug efflux pumps responsible for the multidrug resistance phenotype causing hepatocellular carcinoma (HCC) treatment failure. Here we studied the expression of 15 ABC transporters relevant for multidrug resistance in 19 paired HCC patient samples (16 untreated, 3 treated by chemotherapeutics). Twelve ABC transporters showed up-regulation in HCC compared with adjacent healthy liver. These include ABCA2, ABCB1, ABCB6, ABCC1, ABCC2, ABCC3, ABCC4, ABCC5, ABCC10, ABCC11, ABCC12, and ABCE1. The expression profile and function of some of these transporters have not been associated with HCC thus far. Because cellular microRNAs (miRNAs) are involved in posttranscriptional gene silencing, we hypothesized that regulation of ABC expression in HCC might be mediated by miRNAs. To study this, miRNAs were profiled and dysregulation of 90 miRNAs was shown in HCC compared with healthy liver, including up-regulation of 11 and down-regulation of 79. miRNA target sites in ABC genes were bioinformatically predicted and experimentally verified in vitro using luciferase reporter assays. In total, 13 cellular miRNAs were confirmed that target ABCA1, ABCC1, ABCC5, ABCC10, and ABCE1 genes and mediate changes in gene expression. Correlation analysis between ABC and miRNA expression in individual patients revealed an inverse relationship, providing an indication for miRNA regulation of ABC genes in HCC. Conclusion: Up-regulation of ABC transporters in HCC occurs prior to chemotherapeutic treatment and is associated with miRNA down-regulation. Up-regulation of five ABC genes appears to be mediated by 13 cellular miRNAs in HCC patient samples. miRNA-based gene therapy may be a novel and promising way to affect the ABC profile and overcome clinical multidrug resistance. (HEPATOLOGY 2012;55:821-832) H epatocellular carcinoma (HCC) is the fifth most common type of cancer worldwide. With a 5-year survival of less than 5%, 1 HCC remains one of the most fatal cancers, and few treatments have proven to be effective. Major pitfalls are late diagnosis, tumor recurrence, and resistance to chemotherapeutic treatment. This is caused by a phenomenon called multidrug resistance, mediated by high expression of adenosine triphosphate (ATP)-binding cassette (ABC) transporter family members that decrease the intracellular concentration of chemotherapeutic agents. [2][3][4][5][6] There is limited information in the literature on the expression profile of ABC genes in HCC. For example, ABCB1 (MDR1) 7,8 and ABCC3 (MRP3) 9 have been shown to be up-regulated in HCC of undetermined treatment status and a high expression of ABCC1 (MRP1) has been associated with an aggressive HCC phenotype in untreated

Relative quantitative expression of hypoxia-inducible factor-1α, −2α and −3α, and vascular endothelial growth factor A in laryngeal carcinoma

“…To determine the relative expression of each gene in the tumor, the 2-ΔΔCt method was applied (26 ΔΔCt , where ΔΔCt = ΔCt T -ΔCt N . An RQ of >2 was defined as overexpression, and an RQ of <0.5 was defined as underexpression of the gene, in agreement with previous studies (27,28).…”

The biological regulation of ABCE1

“…Surveyed of 23 drug-resistant tumor cell lines, the expression of 13 ABC transporter genes, including ABCE1 gene, differs from their drug-sensitive parental cell lines, suggesting such gene might be implicated in acquired chemoresistance (45). In an investigation of the expression of 15 ABC transporters relevant for multidrug resistance in 19 paired HCC patient samples, ABCE1 protein has been showed upregulation in tumor tissues compared with adjacent healthy liver, inferring that upregulation of ABCE1 gene in HCC occurs before chemotherapeutic treatment (46). It is currently unknown precisely how ABCE1 protein acts in drug resistance.…”

Polycyclic Aromatic Hydrocarbons (PAHs) Mediate Transcriptional Activation of the ATP Binding Cassette Transporter ABCB6 Gene via the Aryl Hydrocarbon Receptor (AhR)

“…These epoxides are highly reactive electrophiles and cause mutations and cytotoxicity in both prokaryotic and eukaryotic cells. In this context, it is interesting to note that ABCB6 expression promotes cell growth and proliferation in hepatoma cells, and ABCB6 expression is induced during the development of hepatocellular carcinoma (20,56,57). Thus, ABCB6 induction by PAHs could be a potential contributing factor in PAH carcinogenicity.…”