miR-449a Suppresses Tamoxifen Resistance in Human Breast Cancer Cells by Targeting ADAM22

Abstract

Background/Aims: Most of estrogen receptor positive breast cancer patients respond well initially to endocrine therapies, but often develop resistance during treatment with selective estrogen receptor modulators (SERMs) such as tamoxifen. Altered expression and functions of microRNAs (miRNAs) have been reportedly associated with tamoxifen resistance. Thus, it is necessary to further elucidate the function and mechanism of miRNAs in tamoxifen resistance. Methods: Tamoxifen sensitivity was validated by using Cell Counting Kit-8 in tamoxifen-sensitive breast cancer cells (MCF-7, T47D) and tamoxifen-resistant cells (MCF-7/TAM, T47D/ TAM). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the expression level of miR-449a in tamoxifen-sensitive/-resistant cells and patient serums. Dual-luciferase assay was used to identify the binding of miR-449a and predicted gene ADAM22. The expression level of ADAM22 was determined by qRT-PCR and western blotting in miR-449a +/- breast cancer cells. Subsequently, rescue experiments were carried out to identify the function of ADAM22 in miR-449a-reduced tamoxifen resistance. Finally, Gene ontology (GO) and Protein-protein interaction analyses were performed to evaluate the potential mechanisms of ADAM22 in regulating tamoxifen resistance. Results: MiR-449a levels were downregulated significantly in tamoxifen-resistant breast cancer cells when compared with their parental cells, as well as in clinical breast cancer serum samples. Overexpression of miR-449a re-sensitized the tamoxifen-resistant breast cancer cells, while inhibition of miR-449a conferred tamoxifen resistance in parental cells. Luciferase assay identified ADAM22 as a direct target gene of miR-449a. Additionally, silencing of ADAM22 could reverse tamoxifen resistance induced by miR-449a inhibition in ER-positive breast cancer cells. GO analysis results showed ADAM22 was mainly enriched in the biological processes of cell adhesion, cell differentiation, gliogenesis and so on. Protein-protein interaction analyses appeared that ADAM22 might regulate tamoxifen resistance through PPARG, LGI1, KRAS and LYN. Conclusion: Decreased miR-449a causes the upregulation of ADAM22, which induces tamoxifen resistance of breast cancer cells. These results suggest that miR-449a, functioning by targeting ADAM22, contributes to the mechanisms underlying breast cancer endocrine resistance, which may provide a potential therapeutic strategy in ER-positive breast cancers.

The function of SNHG7/miR‐449a/ACSL1 axis in thyroid cancer

“…23 miR-449a inhibits tamoxifen resistance of human breast cancer cells via targeting ADAM22. 24 miR-449a hinders tumor F I G U R E 4 SNHG7 upregulates ACSL1 through sequestering miR-449a in TC cells. A, After transfection, RT-qPCR was conducted.…”

Emerging roles of exosomal miRNAs in breast cancer drug resistance

“…TFPIa is an apoptosis inducer in BC cells . A decrease in exosomal miRNA‐449a of BC cells upregulates the expression of ADAM22 (a disintegrin and metalloprotease domain‐22) and, thereby, induces the tamoxifen resistance …”

Circular RNA circ‐Ttc3 protects HaCaT cells from hypoxic injury by downregulation of miR‐449a

“…Furthermore, miR‐449a served as diverse role in diversified diseases and cells. For example, miR‐449a was explored to play essential role in breast cancer endocrine resistance . Another research demonstrated that inhibition of miR‐449a prevented H9c2 cells from hypoxic injury via Notch‐1 pathway .…”

“…For example, miR-449a was explored to play essential role in breast cancer endocrine resistance. 22 Another research demonstrated that inhibition of miR-449a prevented H9c2 cells from hypoxic injury via Notch-1 pathway. 23 Currently, we proposed to investigate circ-Ttc3 and miR-449a influence and interaction mechanism in HaCaT cells.…”