Cancer Drug Resistance Group, IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal.
Curr Drug Targets. 2013 Sep;14(10):1135-43. doi: 10.2174/13894501113149990185.
Overexpression of oncomiR-21 has been observed in most cancer types, such as leukemia. This miR has been implicated in a number of cellular processes, including chemoresistance, possibly by directly modulating the expression of several apoptotic related proteins. It was recently shown to directly target Bcl-2 mRNA and upregulate Bcl-2 protein expression. Nevertheless, the possible effect of miR-21 in autophagy has never been addressed. This study investigates the effects of targeting miR-21 with antimiRs on chronic myeloid leukemia cellular autophagy and on associated drug sensitivity. We observed that miR-21 downregulation decreased cellular viability and proliferation, although no changes to the normal cell cycle profile were observed. miR-21 downregulation also caused increased programmed cell death and a decrease in the expression levels of Bcl-2 protein, although PARP cleavage was not affected, indicating that apoptosis was not the relevant mechanism underlying the observed results. Treatment with antimiR-21 caused an increase in the autophagy related proteins Beclin-1, Vps34 and LC3-II. Accordingly, autophagic vacuoles were visualized both by monodansylcadaverine (MDC) and acridine orange (AO) staining and also by transmission electron microscopy (TEM). Additionally, miR-21 downregulation increased K562 and KYO-1 cellular sensitivity to etoposide or doxorubicin. This chemosensitivity was reverted by pre-treating cells with 3-MA, an autophagy inhibitor. Finally, serum starvation (an autophagy inducer) also increased sensitivity to these drugs, confirming that autophagy sensitized these cells to the effect of these drugs. To the best of our knowledge, this is the first description of autophagy induction via miR-21 targeting and its involvement in drug sensitivity.
miR-21 的过表达已在大多数癌症类型中观察到，例如白血病。该 miR 已涉及许多细胞过程，包括化学抗性，可能通过直接调节几种凋亡相关蛋白的表达。最近已显示其可直接靶向 Bcl-2 mRNA 并上调 Bcl-2 蛋白表达。然而，miR-21 在自噬中的可能作用尚未得到解决。本研究探讨了用反义 miR 靶向 miR-21 对慢性髓性白血病细胞自噬和相关药物敏感性的影响。我们观察到，miR-21 的下调降低了细胞活力和增殖，尽管正常细胞周期谱没有变化。miR-21 的下调还导致程序性细胞死亡增加和 Bcl-2 蛋白表达水平降低，尽管 PARP 切割不受影响，表明凋亡不是观察到的结果的相关机制。用反义 miR-21 处理会导致自噬相关蛋白 Beclin-1、Vps34 和 LC3-II 的表达增加。因此，通过单丹磺酰尸胺 (MDC) 和吖啶橙 (AO) 染色以及透射电子显微镜 (TEM) 观察到自噬小泡。此外，miR-21 的下调增加了 K562 和 KYO-1 细胞对依托泊苷或阿霉素的敏感性。用自噬抑制剂 3-MA 预处理细胞可逆转这种化学敏感性。最后，血清饥饿（自噬诱导剂）也增加了对这些药物的敏感性，证实自噬使这些细胞对这些药物的作用敏感。据我们所知，这是首次描述通过靶向 miR-21 诱导自噬及其在药物敏感性中的参与。
