Expression and promoter methylation analysis of ATP-binding cassette genes in pancreatic cancer

Abstract

Abstract. We investigated the relationship of ABCB1/MDR1, ABCC1/MRP1 and ABCG2/BCRP expression and promoter methylation with pancreatic cancer tumorigenesis and drug resistance. Gemcitabine-resistant pancreatic cancer cells, SW1990/ GZ (33.3-fold increased resistance), were obtained by treating SW1990 cells with gemcitabine. The expression of ABCB1/ MDR1, ABCC1/MRP1 and ABCG2/BCRP was determined by quantitative real-time RT-PCR in the cell lines, 3 normal pancreatic tissues, 15 human pancreatic cancer samples and 15 adjacent tissues. Promoter methylation was determined in cell lines by bisulfite genomic sequencing. ABCB1/MDR1, ABCC1/ MRP1 and ABCG2/BCRP were upregulated in SW1990 and SW1990/GZ compared with normal pancreatic tissue, and expression in SW1990/GZ was significantly higher than in SW1990 cells. ABCB1/MDR1, ABCC1/MRP1 and ABCG2/ BCRP were upregulated in pancreatic cancer tissues, compared to adjacent tissues. The ABCB1/MDR1, ABCC1/MRP1 and ABCG2/BCRP promoter were hypomethylated in all the cell lines. ABCB1/MDR1, ABCC1/MRP1 and ABCG2/BCRP expression correlated with pancreatic cancer tumorigenesis and drug resistance in a mechanism that is independent of promoter methylation. IntroductionPancreatic cancer is among the 10 leading causes of cancerrelated deaths, with a 5-year survival <5% (1). Most patients have advanced stage disease at diagnosis. One fifth of pancreatic cancer patients present in the early stage and are eligible for surgical resection (2), which is a complex operation that is associated with high rates of operative morbidity. Pancreatic cancer also shows resistance to chemotherapy. Gemcitabine, the standard treatment in advanced disease, prolongs survival by 5-6 months. Chemotherapy is largely ineffective for patients with metastases as disease frequently redevelops even after surgery; therefore, there is an urgent need to understand the molecular mechanism of chemoresistance in pancreatic cancer.One well-known mechanism of chemoresistance is the overexpression of energy-dependent pumps, such as adenosine triphosphate-binding cassette (ABC) transporters, which lead to the extrusion of drugs and their metabolites (3). P-gp, a 170,000-Da phosphoglycoprotein that consists of two ATP binding cassettes and two transmembrane regions, which is associated with chemoresistance in cancers of the gastrointestinal tract, liver and kidneys (4). The breast cancer resistance protein (ABCG2/BCRP) is a 655-amino-acid polypeptide transporter with a wide range of substrates associated with breast cancer resistance (5). Additionally, ABCC1/MRP1 is correlated with differentiation grade and tumor size in primary hepatocellular carcinoma and breast cancer (6,7).DNA methylation of CpG dinucleotides is the predominant epigenetic gene expression modification. More than 40% of protein coding genes have 5' CpG rich segments, termed CpG islands (8). The aberrant methylation of gene promoters is frequently observed in human cancers and correlates with carcinogenesis, tumor progression and chemosensitivity (9,10). M...

ATP-Binding Cassette Genes Genotype and Expression: A Potential Association with Pancreatic Cancer Development and Chemoresistance?

“…This finding is consistent with other reports [9–12] for the potential involvement of ABC transporters in pancreatic cancer chemoresistance.…”

“…Of the 49 human ABC transporters, 15 are implicated in conferring resistance to chemotherapeutic agents in various cancers, and the most intensively characterized members are multidrug resistance 1 (MDR1 or P-glycoprotein, ABCB1), multidrug resistance protein 1 (MRP1, ABCC1), and breast cancer resistance protein (BCRP, ABCG2) [7]. Elevated expression of ABCB1, ABCG2, and ABCCs mRNA in pancreatic adenocarcinomas compared to normal pancreas has been reported [9–12], but correlation with clinical aggressiveness of the tumor remains controversial [11, 12]. …”

Altered methylation of glucosylceramide synthase promoter regulates its expression and associates with acquired multidrug resistance in invasive ductal breast cancer

“…The conclusions were similar to a previous investigation: Lincke et al demonstrated a rough correlation between hypomethylation and transcription of the 5′end of the MDR1 and MDR3 genes [28]. Hirofumi et al suggested that methylation status of BCRP was inversely correlated with its expression in lung cancer cells [29], multiple myeloma [30] and pancreatic cancer [31]. …”

Identification of miR-145 targets through an integrated omics analysis

“…63 Expression of ABCC1 is also increased in pancreatic cancer. 64 Serine palmitoyltransferase 1 (SPLTC1) participates in sphingolipid metabolism, and its activity is elevated in endometrial cancer tissue. 65 To validate these novel miR-145 candidate targets along with known targets, we employed luciferase-3′UTR assays to examine the effect of miR-145 overexpression on these targets, several of which showed significant repression (miR-145/control): FSCN1, DIAPH1, PRPSAP2, RPA1, RBM22, SET, SPTLC1 and SPTBN1 (Fig.…”