Acquisition of docetaxel resistance in breast cancer cells reveals upregulation of ABCB1 expression as a key mediator of resistance accompanied by discrete upregulation of other specific genes and pathways

Abstract

The microtubule-targeting taxanes are important in breast cancer therapy, but no predictive biomarkers have yet been identified with sufficient scientific evidence to allow clinical routine use. The purposes of the present study were to develop a cell-culture-based discovery platform for docetaxel resistance and thereby identify key molecular mechanisms and predictive molecular characteristics to docetaxel resistance. Two docetaxel-resistant cell lines, MCF7RES and MDARES, were generated from their respective parental cell lines MCF-7 and MDA-MB-231 by stepwise selection in docetaxel dose increments over 15 months. The cell lines were characterized regarding sensitivity to docetaxel and other chemotherapeutics and subjected to transcriptome-wide mRNA microarray profiling. MCF7RES and MDARES exhibited a biphasic growth inhibition pattern at increasing docetaxel concentrations. Gene expression analysis singled out ABCB1, which encodes permeability glycoprotein (Pgp), as the top upregulated gene in both MCF7RES and MDARES. Functional validation revealed Pgp as a key resistance mediator at low docetaxel concentrations (first-phase response), whereas additional resistance mechanisms appeared to be prominent at higher docetaxel concentrations (second-phase response). Additional resistance mechanisms were indicated by gene expression profiling, including genes in the interferon-inducible protein family in MCF7RES and cancer testis antigen family in MDARES. Also, upregulated expression of various ABC transporters, ECM-associated proteins, and lysosomal proteins was identified in both resistant cell lines. Finally, MCF7RES and MDARES presented with cross-resistance to epirubicin, but only MDARES showed cross-resistance to oxaliplatin. In conclusion, Pgp was identified as a key mediator of resistance to low docetaxel concentrations with other resistance mechanisms prominent at higher docetaxel concentrations. Supporting Pgp upregulation as one major mechanism of taxane resistance and cell-line-specific alterations as another, both MCF7RES and MDARES were cross-resistant to epirubicin (Pgp substrate), but only MDARES was cross-resistant to oxaliplatin (non-Pgp substrate).

Antibody validation and scoring guidelines for ABCG2 immunohistochemical staining in formalin-fixed paraffin-embedded colon cancer tissue

“…In addition, docetaxel resistant MDA-MB-231 and MCF7 cells29 and their parental counterparts were used to evaluate potential cross-reactivity with the ABCB1 (P-glycoprotein (PGP), MDR1) protein. Resistant sublines were obtained by passaging cells in increasing concentrations of docetaxel and were maintained in docetaxel-supplemented medium.…”

Identifying clinically relevant drug resistance genes in drug-induced resistant cancer cell lines and post- chemotherapy tissues

“…Differentially expressed genes (DEGs) between parental and drug–induced resistant cells are frequently regarded as drug resistance genes [ 1 – 6 ] and used to identify predictive markers of therapeutic benefit [ 7 – 9 ]. However, findings of such studies can be hardly translated into clinical practice [ 10 – 14 ].…”

Prostate Tumor Overexpressed-1 (PTOV1) promotes docetaxel-resistance and survival of castration resistant prostate cancer cells

“…The IC 50 for docetaxel in resistant Du145 and PC3 cells transduced with control lentivirus are also shown for comparison. To elucidate the molecular mechanisms implicated in this PTOV1-mediated chemo resistance, a battery of genes previously implicated in docetaxel resistance were analyzed in PTOV1-overexpressing cells [ 22 , 23 , 31 , 34 ]. Figure 2C shows that PTOV1 significantly induces the expression of CCNG2, ABCB1, TUBB4A and TUBB2B genes, supporting its action in promoting the resistance to docetaxel.…”