酪氨酸磷酸酶PRL-3增加胃癌细胞BGC823的SP细胞比例并提高其对化疗药物的耐受性

蛋白酪氨酸磷酸酶PRL-3是近年发现的蛋白酪氨酸磷酸酶家族成员，能促进肿瘤细胞的侵袭、转移及上皮细胞间质转型，提示PRL-3可能在肿瘤发生发展及诱导肿瘤干细胞生成中发挥重要作用.由于侧群(SP)细胞具有许多干细胞的性质，SP细胞分选是目前筛选和分离获得干细胞或前体细胞常用的有效方法.为探讨PRL-3在诱导干细胞生成中的潜在作用，本文在建立过表达PRL-3的人胃癌细胞BGC823的基础上，通过SP分选和CCK-8的方法分析PRL-3对BGC823细胞中SP细胞的比例以及对化疗药物耐受性的影响.结果提示，高表达PRL-3提高BGC823中SP细胞的比例（2.5% vs 9.4%），同时增加BGC823对化疗药物紫杉醇和顺铂的耐受性（相对于对照细胞，其耐药指数分别为1.75和1.29）.由于SP细胞的产生和细胞耐药性的提高与ABC家族基因表达水平上调密切相关,通过定量 RT-PCR和Western印迹检测发现，PRL-3能上调ABCB1和ABCG2的表达.上述研究结果表明，PRL-3有可能通过上调ABCB1和ABCG2的表达，增加胃癌细胞BGC823的SP细胞比例并增加其对化疗药物的耐受性.

PRL-3 Increases Side Population in Human Gastric Cancer BGC823 Cells and Elevates Resistance to Chemotherapeutic Drugs

PRL-3 (phosphatase of regenerating liver-3), a metastasis-associated protein, belongs to the PRL family of protein tyrosine phosphatases. Recent studies showed that PRL-3 plays a stimulatory role in triggering the epithelial-mesenchymal transitions (EMT) during cancer metastasis, suggesting that PRL-3 may be essential for tumorigenesis and induction of tumor stem cells. As side population (SP) cells exhibit several stem cell-like properties, SP isolation is a valuable approach to obtain and identify cancer stem cells. To study the potential effect of PRL-3 on tumor stem cells, flow cytometry and CCK-8 assay were utilized to analyze the ratio of SP cells in cancer cells. The resistance to chemotherapeutic drugs in BGC823 cells stably expressing PRL-3 (823-P) was also examined. The results showed that PRL-3 increases the ratio of SP cells from 25% to 94%, and confers resistance to Taxol and Cisplatin (resistance index of 175 and 129, respectively). Since the generation of SP cells and resistance to chemotherapeutic drugs are closely related to ABC (ATP-binding cassette) family, quantitative RT-PCR and Western blotting were performed to check the expression of ABC transporters. We found that PRL-3 up-regulated ABCB1 and ABCG2 expression. Therefore, PRL-3 may promote SP cells in cancer cell lines and increase resistance to chemotherapeutic drugs through elevated ABCB1 and ABCG2 expression.