Laboratory of Biochemistry, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Polyclinic, Palermo, Italy.
Oncology Research Center of Mercogliano (CROM), Istituto Nazionale per lo Studio e la Cura dei Tumori "Fondazione Giovanni Pascale", IRCCS, Naples, Italy.
J Cell Physiol. 2016 Aug;231(8):1832-41. doi: 10.1002/jcp.25291. Epub 2016 Jan 28.
Osteosarcoma (OS), an aggressive highly invasive and metastatic bone-malignancy, shows therapy resistance and recurrence, two features that likely depend on cancer stem cells (CSCs), which hold both self-renewing and malignant potential. So, effective anticancer therapies against OS should specifically target and destroy CSCs. We previously found that the let-7d microRNA was downregulated in the 3AB-OS-CSCs, derived from the human OS-MG63 cells. Here, we aimed to assess whether let-7d modulation affected tumorigenic and stemness properties of these OS-CSCs. We found that let-7d-overexpression reduced cell proliferation by decreasing CCND2 and E2F2 cell-cycle-activators and increasing p21 and p27 CDK-inhibitors. Let-7d also decreased sarcosphere-and-colony forming ability, two features associated with self-renewing, and it reduced the expression of stemness genes, including Oct3/4, Sox2, Nanog, Lin28B, and HMGA2. Moreover, let-7d induced mesenchymal-to-epithelial-transition, as shown by both N-Cadherin-E-cadherin-switch and decrease in vimentin. Surprisingly, such switch was accompanied by enhanced migratory/invasive capacities, with a strong increase in MMP9, CXCR4 and VersicanV1. Let-7d- overexpression also reduced cell sensitivity to apoptosis induced by both serum-starvation and various chemotherapy drugs, concomitant with decrease in caspase-3 and increase in BCL2 expression. Our data suggest that let-7d in 3AB-OS-CSCs could induce plastic-transitions from CSCs-to-non-CSCs and vice-versa. To our knowledge this is the first study to comprehensively examine the expression and functions of let-7d in OS-CSCs. By showing that let-7d has both tumor suppressor and oncogenic functions in this context, our findings suggest that, before prospecting new therapeutic strategies based on let-7d modulation, it is urgent to better define its multiple functions. J. Cell. Physiol. 231: 1832-1841, 2016. © 2015 Wiley Periodicals, Inc.
成骨肉瘤（OS）是一种侵袭性和转移性强的骨恶性肿瘤，表现出治疗抵抗和复发的特征，这两个特征可能依赖于癌症干细胞（CSCs），CSCs 具有自我更新和恶性潜能。因此，针对 OS 的有效抗癌疗法应该特异性地针对和破坏 CSCs。我们之前发现，在源自人成骨肉瘤-MG63 细胞的 3AB-OS-CSCs 中，let-7d 微 RNA 下调。在这里，我们旨在评估 let-7d 调节是否影响这些 OS-CSCs 的致瘤和干性特性。我们发现，let-7d 过表达通过降低细胞周期激活物 CCND2 和 E2F2 并增加 p21 和 p27 CDK 抑制剂来减少细胞增殖。let-7d 还降低了球体和集落形成能力，这两个特征与自我更新有关，并且降低了干性基因的表达，包括 Oct3/4、Sox2、Nanog、Lin28B 和 HMGA2。此外，let-7d 诱导了间充质到上皮的转变，这表现为 N-钙粘蛋白-E-钙粘蛋白的转换和波形蛋白的减少。令人惊讶的是，这种转换伴随着迁移/侵袭能力的增强，MMP9、CXCR4 和 VersicanV1 的强烈增加。let-7d 过表达还降低了细胞对血清饥饿和各种化疗药物诱导的凋亡的敏感性，同时降低了 caspase-3 的表达，增加了 BCL2 的表达。我们的数据表明，3AB-OS-CSCs 中的 let-7d 可以诱导从 CSCs 到非 CSCs 的可塑性转变，反之亦然。据我们所知，这是首次全面研究 let-7d 在 OS-CSCs 中的表达和功能的研究。通过表明 let-7d 在这种情况下具有肿瘤抑制和致癌功能，我们的研究结果表明，在探索基于 let-7d 调节的新治疗策略之前，迫切需要更好地定义其多种功能。J. 细胞生理学。231:1832-1841，2016。©2015 年 Wiley 期刊出版公司
