School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China.
Department of Thoracic Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, 100050, China.
BMC Cancer. 2021 Jun 29;21(1):750. doi: 10.1186/s12885-021-08495-z.
Tumor microenvironment (TME) critically contributed to the malignant progression of transformed cells and the chemical responses to chemotherapy reagents. Osteopontin (OPN) is a secretory onco-protein with several splicing isoforms, all of which were known to regulate tumor growth and able to alter cell-cell or cell-TME communication, however, the exact role and regulation of the OPN splicing isoforms was not well understood.
In this study, the effects of conditioned medium from the culture of OPN splicing isoforms overexpressing cells on cell functions were evaluated. The methods of nuclear calcium reporter assays and subcellular distribution of nuclear factor of activated T cells c2 (NFATc2) assays were used to investigate the molecular mechanism underlining the roles of OPN splicing isoforms.
We found that the survival of NSCLC cells treated with cisplatin was increased by secretory OPNc in the condition medium, where reduction of apoptosis by OPNc was associated with the activation of cellular calcium signals and subsequent nuclear translocation of NFATc2.
The results revealed a mechanism of OPN and downstream signal for tumor cells to survive in chemo-stressed TME, which emphasized the importance of secretory proteins in alternative splicing isoforms. Our study not only demonstrated the importance of OPN neutralization for anti-tumor effects, but also implied that modulation in calcium/NFATc2/ROS axis could be a novel approach for improving the long-term outcome of NSCLC treatment.
肿瘤微环境（TME）对转化细胞的恶性进展和化学治疗试剂的化学反应起着至关重要的作用。骨桥蛋白（OPN）是一种具有多种剪接异构体的分泌癌蛋白，所有这些异构体都被认为可以调节肿瘤生长，并能够改变细胞-细胞或细胞-TME 的通讯，但 OPN 剪接异构体的确切作用和调控机制尚不清楚。
在这项研究中，评估了过表达 OPN 剪接异构体细胞培养的条件培养基对细胞功能的影响。使用核钙报告基因检测和激活 T 细胞核因子 c2（NFATc2）亚细胞分布检测方法，研究了 OPN 剪接异构体作用的分子机制。
我们发现，顺铂处理的 NSCLC 细胞的存活率因条件培养基中的分泌型 OPNc 而增加，OPNc 通过减少细胞凋亡与细胞钙信号的激活和随后的 NFATc2 核转位有关。
这些结果揭示了 OPN 及其下游信号在肿瘤细胞在化疗应激的 TME 中存活的机制，强调了分泌蛋白在剪接异构体中的重要性。我们的研究不仅证明了中和 OPN 对抗肿瘤作用的重要性，还暗示钙/NFATc2/ROS 轴的调节可能是改善 NSCLC 治疗长期疗效的一种新方法。
