Increased Expression of Exosomal AGAP2-AS1 (AGAP2 Antisense RNA 1) In Breast Cancer Cells Inhibits Trastuzumab-Induced Cell Cytotoxicity

Abstract

Background Trastuzumab therapy is important for patients with HER2-positive breast cancer, but more and more patients have experienced trastuzumab resistance during recent years. Accumulating evidence from recent studies showed that long non-coding RNAs (lncRNAs) play essential roles in chemoresistance of various cancer types, but the precise role of lncRNAs in trastuzumab resistance is unclear. In the present study, we aimed to identify the biofunction of lncRNA APAP2-AS1 in tranastuzumab resistance and to reveal the underlying regulatory mechanism. Material/Methods By culturing HER2-positive SKBR-3 and BT474 cells with transtuzumab-containing medium, we built trastuzumab-resistant cells. Quantitative real-time PCR was used to test the expression of AGAP2-AS1 in the built trastuzumab-resistant cells. Cell viability assay and TUNEL assay were used to test the cell viability and apoptosis in each group. Exosomes were purified from cells cultured in exosomes-depleted FBS and identified by transmission electron microscopy. Results qRT-PCR assay suggested that AGAP2-AS1 was upregulated in the built trastuzumab-resistant cells when compared with parental sensitive cells. Cell viability assay showed that silencing of AGAP2-AS1 enhanced the cytotoxicity induced by trastuzumab treatment. Mechanistically, we revealed that AGAP2-AS1 was secreted outside cells by incorporation into exosomes in an hnRNPA2B1-dependent manner. More importantly, co-culture AGAP2-AS1-containing exosomes with sensitive cells reduced the trastuzumab-induced cell death, and silencing of AGAP2-AS1 from exosomes reversed this effect. In summary, AGAP2-AS1 promotes trastuzumab resistance of breast cancer cells through packaging into exosomes. Conclusions Knockdown of AGAP2-AS1 may be helpful for improving the clinical outcome for HER2+ breast cancer patients and could serve as a therapeutic target.

Exosomes and breast cancer drug resistance

“…Also, the exosomal expression of lncRNA-SNHG14 in serum was highly upregulated in patients who exhibited resistance to trastuzumab compared with patients who responded to trastuzumab 66 . Similarly, the lncRNA AGAP2 antisense RNA 1 (AGAP2-AS1)-containing exosomes also enhanced trastuzumab resistance in BC cells 67 . The heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1), an RNA-binding protein, was found essential in loading lncRNA AGAP2-AS1 into exosomes 68 .…”

Isolation and characterization of exosomes for cancer research

“…Recent studies have reported that exosomes can also reduce the effects of chemotherapy via removal of chemotherapeutic drugs from tumor cells. For example, breast cancer cell-derived exosomes can reduce the effectiveness of trastuzumab, a first-line drug for advanced HER2-positive breast cancer patients; thus, removal of such exosomes from circulation could restore trastuzumab sensitivity in the breast cancer cells [ 199 ]. Therefore, exosomes are a major determinant for inducing or disseminating resistance phenotypes in anti-tumor therapy.…”

<p>Long Non-Coding RNAs in Drug Resistance of Breast Cancer</p>

“…97 AGAP2-AS1 decreases the cytotoxicity of TZB via being incorporated into exosomes, and promotes TZB resistance in BC. 98 AGAP2-AS1 inhibits cell apoptosis and promotes TZB resistance in BC cells by upregulating MyD88, which results from the enrichment of H3K27ac at the promoter region of MyD88, and activating the NF-κB signaling pathway. 99 LncRNA TINCR is upregulated in HER-2+ BC cells; it sponges miR-125b and targets Snail-1, thereby promoting TZB resistance and the associated EMT process in BC cells.…”

“…51 AGAP2-AS1 is incorporated into exosomes in an hnRNPA2B1-dependent manner, thereby decreasing TZB-induced cytotoxicity and promoting TZB resistance in BC cells. 98 SNHG14 promotes TZB resistance in sensitive BC cells via exosomes. 102 In addition to ceRNAs and exosomes, lncRNAs can regulate drug resistance in BC via cellular or molecular targets.…”