Riboregulator H19 induction of MDR1-associated drug resistance in human hepatocellular carcinoma cells

Abstract

Acquisition of drug resistance is one of the main obstacles encountered in cancer chemotherapy. Overexpression of multi-drug resistance 1 (MDR1) gene and its protein product P-glycoprotein, accompanied with a decrease in doxorubicin accumulation level, was observed in doxorubicin-resistant R-HepG2 cells, a subline derived by selection of human hepatocellular carcinoma HepG2 cells with doxorubicin. In addition, Northern-blot analysis revealed an eight fold upregulation of the imprinted H19 mRNA in R-HepG2 cells. H19 knockdown by transfection with antisense H19 oligonucleotides suppressed the MDR1/P-glycoprotein expression, increased the cellular doxorubicin accumulation level and sensitized doxorubicin toxicity in both HepG2 parent cells and R-HepG2 cells. Results from methylation-specific polymerase chain reaction analysis indicated that the MDR1 gene promoter was hypomethylated in R-HepG2 cells. Antisense H19 oligonucleotides transfection induced a marked increase in the percentage of MDR1 promoter methylation and decrease in MDR1 expression in R-HepG2 cells. Thus, the H19 gene is believed to induce P-glycoprotein expression and MDR1-associated drug resistance at least in liver cancer cells through regulation of MDR1 promoter methylation.

Promoter methylation of glutathione S‐transferase π1 and multidrug resistance gene 1 in bronchioloalveolar carcinoma and its correlation with DNA methyltransferase 1 expression

“…31,32 However, other reports have demonstrated that chemotherapeutic drugs may induce specific epigenetic modifications (hypomethylation) at the MDR1 locus and may up-regulate MDR1 by transcriptional activation. 33,34 In the current study, there was a significant correlation between MDR1 methylation and negative Pgp expression. Our results support the conclusion that methylation of the MDR1 promoter negatively regulates Pgp protein expression in BAC.…”

Wilms' Tumor 1 Gene Expression in Hepatocellular Carcinoma Promotes Cell Dedifferentiation and Resistance to Chemotherapy

“…4B). Drug resistance in tumor cells, including HCC cells, is also associated with the expression of the multidrug resistance 1 (MDR1) gene (18). Moreover, repetitive treatment with doxorubicin is known to enhance multidrug resistance of cancer cells (19).…”

“…The mechanisms involved in WT1 regulation of MDR1 expression in HCC cells are not fully understood at the moment. These may include a direct interaction of WT1 with MDR1 promoter as described in leukemia cells (43), or could involve indirect mechanisms such as the expression of H19, an inducer of MDR1 transcription in liver cancer cells (18) identified in our microarray experiments as a WT1-dependent gene.…”

“…However, although it was not detected in our microarray analysis, here, we show that WT1 was able to promote the expression of the MDR1 gene in HCC cells. MDR1 codes for the drug-transporting membrane-bound P-glycoprotein, a key gene in doxorubicin resistance (18,19). The mechanisms involved in WT1 regulation of MDR1 expression in HCC cells are not fully understood at the moment.…”

The H19-IGF2 Role in Bladder Cancer Biology and DNA-Based Therapy

“…Moreover, results show that the level of H19 RNA is elevated in the multidrug resistance variant of HCC cell lines. Here doxorubicin resistance phenotype is related to H19 over-expression (Tsang et al, 2007). H19 provides a novel and clinically useful diagnostic marker for prognosticating human bladder carcinoma.…”