Abstract
BackgroundAlthough trastuzumab provides significant clinical benefit for HER2-positive breast cancers, responses are limited by the emergence of resistance. Recent evidence suggests that long noncoding RNAs (lncRNAs) play important roles in tumorigenesis and chemoresistance. However, the regulatory mechanism of lncRNAs in trastuzumab resistance is not well established to date. In this research, we identified the differentially expressed lncRNA and investigated its regulatory role in trastuzumab resistance of breast cancer.MethodsLncRNA microarray and qRT-PCR were performed to identify the dysregulated lncRNAs. Transmission electron microscopy, differential ultracentrifugation and qRT-PCR were used to verify the existence of exosomal AFAP1-AS1 (actin filament associated protein 1 antisense RNA 1). Bioinformatics prediction, RNA fluorescence in situ hybridization (RNA-FISH) and immunoprecipitation assays were performed to identify the direct interactions between AFAP1-AS1 and other associated targets, such as AU-binding factor 1 (AUF1) and ERBB2. Finally, a series gain- or loss-functional assays were done to prove the precise role of AFAP1-AS1 in trastuzumab resistance.ResultsAFAP1-AS1 was screened out due to its higher expression in trastuzumab-resistant cells compared to sensitive cells. Increased expression of AFAP1-AS1was associate with poorer response and shorter survival time of breast cancer patients. AFAP1-AS1 was upregulated by H3K27ac modification at promoter region, and knockdown of AFAP1-AS1 reversed trastuzumab resistance. Moreover, extracellular AFAP1-AS1 secreted from trastuzumab resistant cells was packaged into exosomes and then disseminated trastuzumab resistance of receipt cells. Mechanically, AFAP1-AS1 was associated with AUF1 protein, which further promoted the translation of ERBB2 without influencing the mRNA level.ConclusionExosomal AFAP1-AS1 could induce trastuzumab resistance through associating with AUF1 and promoting ERBB2 translation. Therefore, AFAP1-AS1 level may be useful for prediction of trastuzumab resistance and breast cancer treatment.
Highlights
Breast cancer has become a leading cause of cancer-related deaths in the world, and the most common cancer among women [1, 2]
LncRNA AFAP1-AS1 is upregulated in trastuzumabresistant cells and activated by H3K27 acetylation (H3K27ac) In our previous study, breast cancer cells that are resistant to trastuzumab treatment, SKBR-3-TR and BT474TR, were successfully established (Additional file 3: Figure S1a-b) [16]
We found that long noncoding RNAs (lncRNAs) AFAP1AS1 was significantly dysregulated between the two types of cells
Summary
Breast cancer has become a leading cause of cancer-related deaths in the world, and the most common cancer among women [1, 2]. Long noncoding RNAs (lncRNAs) constitute a large class of mRNA-like transcripts, greater than 200 nucleotides with no protein coding capability [6, 7] They are involved in a large variety of biological processes, with reports linking the dysregulation of lncRNAs with cancer cell invasion, proliferation and metastasis through mechanisms ranging from transcriptional levels to posttranscriptional levels [8, 9]. Various of studies have reported that lncRNAs are key regulators in trastuzumab resistance of breast cancer. Shi et al revealed the critical role of lncRNA ATB in trastuzumab resistance in breast cancer [12]. We identified the differentially expressed lncRNA and investigated its regulatory role in trastuzumab resistance of breast cancer
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