Abstract
The aim of this study is to explore the resistance mechanisms to anti‐epidermal growth factor receptor (EGFR) and anti‐human epidermal growth factor receptor (HER2) targeted therapies in breast cancer (BC). Previous studies have implicated the microRNA (miR)‐200 family in maintenance of the epithelial phenotype and sensitivity to EGFR targeted therapies and miR‐221/222 have been associated with epithelial to mesenchymal transition (EMT), tumor progression and therapy resistance. To investigate mechanisms of EGFR/HER2 therapy resistance in breast cancer, therapy resistant variants of the therapy sensitive SKBR3 human breast cancer cell line were created by exposure to different concentrations of the EGFR/HER2 inhibitors lapatinib and gefitinib. Characterization of therapy sensitive and resistant variants of SKBR3 demonstrated that miR‐200a is downregulated while miR‐221 and miR‐222 are overexpressed in the therapy resistant cells. Therefore, the current objective is to validate the role of these miRNAs in therapy resistance. The hypothesis is that re‐expression of miR‐200a and downregulation of miR‐221/222 will help overcome therapy resistance to EGFR/HER2 targeted therapy. Therefore, we re‐expressed miR‐200a ectopically in the therapy resistant and sensitive cells using a lentiviral vector containing miR‐200a, or a control vector. MiR‐221/222 inhibition was achieved by expressing anti‐miR‐221/222 or control inhibitors. MTT assays were used to determine the IC50s for cell viability. Both SKBR3 parental and lapatinib resistant variants with ectopic expression of miR‐200a were more sensitive to lapatinib treatment as shown by a decrease in the IC50 when treated with lapatinib. Therapy sensitive and resistant cell lines also demonstrated a decrease in cell viability when miR‐221 or miR‐222 was downregulated using miRNA inhibitors. In conclusion, overexpression of miR‐200a or downregulation of miR‐ 221/222 family reduces the malignancy of SKBR3 parental cell lines and sensitizes EGFR/HER2 therapy resistant cells. These results suggest that manipulation of miR‐200a, miR‐221 and miR‐222 can be used as therapeutic strategies in combination with HER2/EGFR therapy to reduce cancer malignancy and therapy resistance.Support or Funding InformationThis work was supported by grants from NIH/NIGMS SC3GM094824 to SD, RCMI Programs G12RR03051 to UPR MSC, MBRS Program RISE (R25GM061838) to LDB and MM, and Bright Cure Program (U54) University of Puerto Rico/MD Anderson Cancer Center to PRV.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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