Trastuzumab Produces Therapeutic Actions by Upregulating miR-26a and miR-30b in Breast Cancer Cells

Abstract

ObjectiveTrastuzumab has been used for the treatment of HER2-positive breast cancer (BC). However, a subset of BC patients exhibited resistance to trastuzumab therapy. Thus, clarifying the molecular mechanism of trastuzumab treatment will be beneficial to improve the treatment of HER2-positive BC patients. In this study, we identified trastuzumab-responsive microRNAs that are involved in the therapeutic effects of trastuzumab.Methods and ResultsRNA samples were obtained from HER2-positive (SKBR3 and BT474) and HER2-negetive (MCF7 and MDA-MB-231) cells with and without trastuzumab treatment for 6 days. Next, we conducted a microRNA profiling analysis using these samples to screen those microRNAs that were up- or down-regulated only in HER2-positive cells. This analysis identified miR-26a and miR-30b as trastuzumab-inducible microRNAs. Transfecting miR-26a and miR-30b induced cell growth suppression in the BC cells by 40% and 32%, respectively. A cell cycle analysis showed that these microRNAs induced G1 arrest in HER2-positive BC cells as trastuzumab did. An Annexin-V assay revealed that miR-26a but not miR-30b induced apoptosis in HER2-positive BC cells. Using the prediction algorithms for microRNA targets, we identified cyclin E2 (CCNE2) as a target gene of miR-30b. A luciferase-based reporter assay demonstrated that miR-30b post-transcriptionally reduced 27% (p = 0.005) of the gene expression by interacting with two binding sites in the 3′-UTR of CCNE2.ConclusionIn BC cells, trastuzumab modulated the expression of a subset of microRNAs, including miR-26a and miR-30b. The upregulation of miR-30b by trastuzumab may play a biological role in trastuzumab-induced cell growth inhibition by targeting CCNE2.

The miR-30 Family Inhibits Pulmonary Vascular Hyperpermeability in the Premetastatic Phase by Direct Targeting of Skp2

“…Low serum level of miR-30d is associated with improved prognosis and overall survival in NSCLC (40). The upregulation of miR-30 plays biologic roles in cellular senescence (41) and trastuzumabinduced cell growth arrest (19). In together with our findings, these may suggest combined effects of miR-30s on both primary tumors and distant organs, resulting in the inhibition of tumor proliferation, intravasation, and extravasation.…”

Differential altered expression of let-7a and miR-205 tumor-suppressor miRNAs in different subtypes of breast cancer under treatment with Taxol

“…According to Ichikawa et al, the genome amplification of the HER-2 receptor is high, but the expression of this receptor is poor in SKBR-3 in comparison to . 27 This could justify our results that showed a decreased expression of let-7a and …”

“…12,25,26 It has been demonstrated that the pattern of miRNA expression can be changed in response to treatment with doxorubicin, 5-fluorouracil and trastuzumab, and this alteration can be useful for predicting the outcome of the therapy. [26][27][28] However, there is no clear knowledge of the molecular mechanism of paclitaxel with regards to its effect on miRNAs expression. For that reason, we aimed in this study to evaluate the expression level of 2 tumor-suppressor miRNAs, let-7a and miR-205, before and after treatment with paclitaxel.…”

Recent trends in microRNA research into breast cancer with particular focus on the associations between microRNAs and intrinsic subtypes

“…Ichikawa et al also found that miR-26a and miR-30b mediate the effects of trastuzumab. 79,80 Furthermore, Iorio et al 81 demonstrated that miR-205, which targets HER3 and impairs the downstream Akt-mediated survival pathway, not only has an oncosuppressive role in breast cancer, but also increases its responsiveness to lapatinib and gefitinib.…”