Intercellular transfer of small RNAs from astrocytes to lung tumor cells induces resistance to chemotherapy.

Brain metastases are highly resistance to chemotherapy and have a poor prognosis for cure. Tumor cells are surrounded by activated astrocytes and exploit their cyto-protective properties for protection from apoptosis induced by chemotherapy. The mechanism by which astrocytes protect tumor cells is poorly understood. An important non-mutational mechanism of chemotherapy resistance is regulation of gene translation mediated by small non-coding RNAs (sRNAs), in particular, microRNAs (miRNAs). Here we studied the role of astrocytic sRNAs in promoting resistance of the human lung tumor PC14 cells to apoptosis induced by chemotherapy. To this end we compared the sRNA profile of human lung tumor cells that were cultured with or without astrocytes by miRNA microarray. The results show that sRNAs are transferred from astrocytes to PC14 cells in a contact-dependent manner. This transfer is fast and reached plateau already after six hours of co-culturing. Carbenoxolone, a broad-spectrum gap junction antagonist, inhibited the sRNAs transfer indicating that the sRNAs are transferred via gap-junction, maybe via survival pathways. Enforced expression of these sRNA in PC14 cells increased their resistance to the chemotherapy agent Taxol. In light of these results, we offer novel findings that may be clinically relevant to treatment development for brain metastases. In the current study we focus on the potential transfer of smallRNAs from astrocytes to metastatic lung tumor cells and its outcome on the resistance of tumor cells to chemotherapy. Our experimental system comprised of co-culturing conditioned immortalized mice astrocytes (H-2K b-tsA58 mice, herein astrocytes) and human lung adenocarcinoma PC14 cell line.

脑转移瘤（Brain metastases）对化疗具有高度耐药性，且治愈预后极差。肿瘤细胞被活化的星形胶质细胞包裹，并利用其细胞保护特性抵御化疗诱导的细胞凋亡。目前学界对星形胶质细胞保护肿瘤细胞的具体机制仍知之甚少。化疗耐药的重要非突变机制之一，是由小型非编码RNA（small non-coding RNAs, sRNAs）——尤其是微小RNA（microRNAs, miRNAs）——介导的基因翻译调控。
本研究探讨了星形胶质细胞来源的小型非编码RNA在增强人肺肿瘤PC14细胞抵御化疗诱导凋亡中的作用。为此，我们通过miRNA微阵列（miRNA microarray）技术，对比了在有、无星形胶质细胞共培养条件下的人肺肿瘤细胞的小型非编码RNA表达谱。
实验结果显示，小型非编码RNA以接触依赖的方式从星形胶质细胞转移至PC14细胞。该转移过程速度极快，共培养6小时后即达到平台期。广谱间隙连接拮抗剂甘珀酸（Carbenoxolone）可抑制此类小型非编码RNA的转移，表明其通过间隙连接进行传递，或可通过存活通路发挥作用。在PC14细胞中强制过表达此类小型非编码RNA，可增强其对化疗药物紫杉醇（Taxol）的耐药性。
基于上述结果，本研究提出了与脑转移瘤临床治疗开发相关的全新发现。本研究聚焦于星形胶质细胞向转移性肺肿瘤细胞传递小型非编码RNA的潜在过程，及其对肿瘤细胞化疗耐药性的影响。本实验体系采用条件性永生化小鼠星形胶质细胞（源自H-2K^b-tsA58小鼠，下文简称星形胶质细胞）与人肺腺癌细胞系PC14的共培养模型。