我们前期研究发现在乳腺癌细胞耐药时有55个lncRNA差异表达，其中lncRNA-TR表达上调能显著抑制紫杉醇诱导的细胞凋亡。我们研究显示：在胞浆内lncRNA-TR与POTEF蛋白结合互作。他人研究证实POTEF还能与actin结合并位于胞膜内面，actin继而与微管进行功能或结构互作，过表达POTEF/actin能增加微管稳定性，抑制有丝分裂，促进紫杉醇诱导的细胞凋亡。我们进一步研究发现紫杉醇化疗时lncRNA-TR和actin能彼此削弱对方对乳腺癌细胞凋亡的影响。据此提出科学假设：lncRNA-TR与actin竞争结合POTEF，增加微管不稳定性，抑制细胞凋亡，促使乳腺癌紫杉醇耐药。本项目拟采用RNA干扰、基因突变等技术通过细胞、动物和临床研究验证该假设，有望揭示lncRNA调控乳腺癌紫杉醇耐药的新机制，并为乳腺癌紫杉醇耐药提供新的生物标志物及潜在治疗靶点。

Taxanes are commonly used drugs for treatment of breast cancer. Taxane resistance is a major obstacle to the therapy and leaves few effective treatment options. It has been confirmed that long noncoding RNA (lncRNA) plays an important role in anthracyclines resistance. However, there are few studies that have focused specifically on the role of lncRNA in taxanes resistance. We employed Significance Analysis of Microarrays (SAM) of gene expression in a panel of NCI-60 breast cancer cell lines treated by taxanes, etc. and found that gene lncRNA-TR is a lincRNA, which is related with taxanes resistance. We confirmed that lncRNA-TR exists in cytoplasm by in situ hybridization, RNA immunoprecipitation and subcellular fractionation qPCR. Functional assays showed that up-regulation of lncRNA-TR could significantly (P < 0.01) inhibit the breast cancer cells apoptoses induced by paclitaxel. Knockdown lncRNA-TR could recover the sensitivity of the cells to paclitaxel (P < 0.01). We utilized software RMBase to predict that lncRNA-TR might function via binding POTE ankyrin domain family member F (POTEF). Furthermore, RNA pulldown coupling with massspectrum and RNA immunoprecipitation trials confirmed that lncRNA-TR directly binds to POTEF. It was reported that POTEF binds with actin and coloclize beneath the cell membrane. Actin interacts with microtubule via regulatory and structural. POTEF is closely associated with apoptosis possibly acting as a signal transducer. Overexpression of POTEF/actin promoted cell apoptoses. Knockdown actin expression could promote microtubule dynamic instability and mitotic progression, and attenuate taxane treatment efficacy. We observed that paclitaxel chemotherapy caused significant up-regulation of POTEF mRNA and protein expression levels either in breast cancer cells or clinical samples. Of note, lncRNA-TR did not affect POTEF mRNA and protein expression levels, although it directly binds POTEF. Overexpression of actin in breast cancer cells treated with paclitaxel could significantly increase the apoptotic rate of the cells; Knockdown actin expression could significantly reduce the cells apoptotic rate (P < 0.01; P < 0.01). In addition, up-regulation of lncRNA-TR in the presence of actin transfected with lentivirus in breast cancer cells also could significantly attenuate paclitaxel efficacy (P < 0.01). Furthermore, up-regulation of actin in the presence of lncRNA-TR transfected with lentivirus in breast cancer cells could significantly recover paclitaxel efficacy (P < 0.01). Taken together, we hypothesize that lncRNA-TR might competite with actin to bind POTEF, thereafter weaken actin biological function，promote microtubule dynamic instability and mitotic progression, inhibit breast cancer cells apoptoses, and finally cause taxane therapy resistance. We aim to conduct in vitro and in vivo experiments to verify our scientific hypotheses by taking advantages of modern research techniques involving in RNA interference, luciferase assay, gene mutation, laser confocal microscope, RNA immunoprecipitation and crystallography, etc. Our research may provide new insight into the role of lncRNA in breast cancer taxane resistance and reveal a novel signal pathway and potential therapeutic targets. Furthermore, our reaserch may disclose a potential new biomarker for breast cancer taxane resistance.