Claudin-2 (CLDN2), a tight junctional protein, is involved in the chemoresistance in spheroid culture models of human lung adenocarcinoma A549 cells. However, there is no chemical which can improve the sensitivity to anticancer drugs. So far, we reported that DFYSP, a short peptide which mimics the second extracellular loop (ECL2) of CLDN2, decreases CLDN2 expression in A549 cells, but the concentration is relatively high. Here, we found that the effects of VPDSM and DSMKF are stronger than that of DFYSP. Both VPDSM and DSMKF decreased the protein levels of CLDN2 without affecting the mRNA levels of CLDN2. The peptide-induced decrease in CLDN2 expression was suppressed by monodansylcadaverine (MDC), a clathrin-dependent endocytosis (CDE) inhibitor, and chloroquine, a lysosome inhibitor. CLDN2 was colocalized with ZO-1, an adapter protein, in tight junctions (TJs) under control conditions, whereas it disappeared from the TJs in the peptide-treated cells. Quartz crystal microbalance assay showed that both peptides can bind to recombinant CLDN2 protein. Both peptides increased permeability to paracellular transport marker lucifer yellow. In three-dimensional spheroid culture models, both peptides enhanced the sensitivity to doxorubicin, a cytotoxic anticancer drug, which was inhibited by MDC. We suggest that VPDSM and DSMKF enhance the chemosensitivity to anticancer drugs in aggregated adenocarcinoma cells mediated by the CDE pathway and lysosomal degradation of CLDN2 in lung adenocarcinoma cells. VPDSM and DSMKF, which mimic the ECL2 of CLDN2, may become novel adjuvant therapeutic drugs for lung adenocarcinoma.

中文翻译：

---

Claudin-2结合肽VPDSM和DSMKF下调人肺腺癌A549细胞中claudin-2的表达和抗癌性。

紧密连接蛋白Claudin-2（CLDN2）参与人肺腺癌A549细胞球体培养模型的化学耐药性。但是，没有化学物质可以提高对抗癌药物的敏感性。到目前为止，我们报道了DFYSP，一种模仿CLDN2的第二个细胞外环（ECL2）的短肽，可降低A549细胞中CLDN2的表达，但浓度相对较高。在这里，我们发现VPDSM和DSMKF的效果比DFYSP的效果更强。VPDSM和DSMKF均可降低CLDN2的蛋白水平，而不会影响CLDN2的mRNA水平。肽诱导的CLDN2表达下降被网格蛋白依赖性内吞作用（CDE）抑制剂monodansylcadaverine（MDC）和溶酶体抑制剂chloroquine抑制。CLDN2与衔接蛋白ZO-1共定位，在对照条件下，它们在紧密连接（TJs）中处于关闭状态，而在经过肽处理的细胞中，它从TJ中消失了。石英晶体微量天平测定表明，两种肽均可结合重组CLDN2蛋白。两种肽均增加了对细胞旁转运标记荧光素黄的渗透性。在三维球体培养模型中，两种肽均增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2 ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。而它从肽处理细胞的TJ中消失了。石英晶体微量天平测定表明，两种肽均可结合重组CLDN2蛋白。两种肽均增加了对细胞旁转运标记荧光素黄的渗透性。在三维球体培养模型中，两种肽均增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2的ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。而它从肽处理细胞的TJ中消失了。石英晶体微量天平测定表明，两种肽均可结合重组CLDN2蛋白。两种肽均增加了对细胞旁转运标记荧光素黄的渗透性。在三维球体培养模型中，两种肽均增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2的ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。石英晶体微量天平测定表明，两种肽均可结合重组CLDN2蛋白。两种肽均增加了对细胞旁转运标记荧光素黄的渗透性。在三维球体培养模型中，两种肽均增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2的ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。石英晶体微量天平测定表明，两种肽均可结合重组CLDN2蛋白。两种肽均增加了对细胞旁转运标记荧光素黄的渗透性。在三维球体培养模型中，两种肽均增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2的ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。两种肽都增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2的ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。两种肽都增强了对阿霉素的敏感性，阿霉素是一种细胞毒性抗癌药物，被MDC抑制。我们建议VPDSM和DSMKF增强由CDE途径介导的聚集腺癌细胞中抗癌药的化学敏感性和肺腺癌细胞中CLDN2的溶酶体降解。模仿CLDN2的ECL2的VPDSM和DSMKF可能成为肺腺癌的新型辅助治疗药物。