El Bezawy Rihan, De Cesare Michelandrea, Pennati Marzia, Deraco Marcello, Gandellini Paolo, Zuco Valentina, Zaffaroni Nadia
Molecular Pharmacology Unit, Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133, Milan, Italy.
Colon-Rectal Cancer Surgery Unit, Department of Surgery, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133, Milan, Italy.
J Hematol Oncol. 2017 Jan 18;10(1):19. doi: 10.1186/s13045-016-0387-6.
The value of microRNAs (miRNAs) as novel targets for cancer therapy is now widely recognized. However, no information is currently available on the expression/functional role of miRNAs in diffuse malignant peritoneal mesothelioma (DMPM), a rapidly lethal disease, poorly responsive to conventional treatments, for which the development of new therapeutic strategies is urgently needed. Here, we evaluated the expression and biological effects of miR-34a-one of the most widely deregulated miRNAs in cancer and for which a lipid-formulated mimic is already clinically available-in a large cohort of DMPM clinical samples and a unique collection of in house-developed preclinical models, with the aim to assess the potential of a miR-34a-based approach for disease treatment.
miR-34a expression was determined by qRT-PCR in 45 DMPM and 7 normal peritoneum specimens as well as in 5 DMPM cell lines. Following transfection with miR-34a mimic, the effects on DMPM cell phenotype, in terms of proliferative potential, apoptotic rate, invasion ability, and cell cycle distribution, were assessed. In addition, three subcutaneous and orthotopic DMPM xenograft models were used to examine the effect of miR-34a on tumorigenicity. The expression of miRNA targets and the activation status of relevant pathways were investigated by western blot.
miR-34a was found to be down-regulated in DMPM clinical specimens and cell lines compared to normal peritoneal samples. miR-34a reconstitution in DMPM cells significantly inhibited proliferation and tumorigenicity, induced an apoptotic response, and declined invasion ability, mainly through the down-regulation of c-MET and AXL and the interference with the activation of downstream signaling. Interestingly, a persistent activation of ERK1/2 and AKT in miR-34a-reconstituted cells was found to counteract the antiproliferative and proapoptotic effects of miRNA, yet not affecting its anti-invasive activity.
Our preclinical data showing impressive inhibitory effects induced by miR-34a on DMPM cell proliferation, invasion, and growth in immunodeficient mice strongly suggest the potential clinical utility of a miR-34a-replacement therapy for the treatment of such a still incurable disease. On the other hand, we provide the first evidence of a potential cytoprotective/resistance mechanism that may arise towards miRNA-based therapies through the persistent activation of RTK downstream signaling.
微小RNA（miRNA）作为癌症治疗的新靶点，其价值现已得到广泛认可。然而，目前尚无关于miRNA在弥漫性恶性腹膜间皮瘤（DMPM）中的表达/功能作用的信息，DMPM是一种快速致死性疾病，对传统治疗反应不佳，迫切需要开发新的治疗策略。在此，我们评估了miR-34a（癌症中最广泛失调的miRNA之一，其脂质制剂模拟物已在临床上可用）在大量DMPM临床样本和一组独特的自行开发的临床前模型中的表达及生物学效应，旨在评估基于miR-34a的疾病治疗方法的潜力。
通过qRT-PCR测定45例DMPM和7例正常腹膜标本以及5种DMPM细胞系中miR-34a的表达。用miR-34a模拟物转染后，评估其对DMPM细胞表型的影响，包括增殖潜能、凋亡率、侵袭能力和细胞周期分布。此外，使用三种皮下和原位DMPM异种移植模型来研究miR-34a对致瘤性的影响。通过蛋白质印迹法研究miRNA靶标的表达和相关信号通路的激活状态。
与正常腹膜样本相比，发现miR-34a在DMPM临床标本和细胞系中表达下调。在DMPM细胞中重建miR-34a可显著抑制增殖和致瘤性，诱导凋亡反应，并降低侵袭能力，主要是通过下调c-MET和AXL以及干扰下游信号的激活。有趣的是，在重建了miR-34a的细胞中发现ERK1/2和AKT的持续激活可抵消miRNA的抗增殖和促凋亡作用，但不影响其抗侵袭活性。
我们的临床前数据显示miR-34a对免疫缺陷小鼠中的DMPM细胞增殖、侵袭和生长具有显著的抑制作用，这强烈表明miR-34a替代疗法在治疗这种仍无法治愈的疾病方面具有潜在的临床应用价值。另一方面，我们首次提供了一种潜在的细胞保护/耐药机制的证据，该机制可能通过RTK下游信号的持续激活而在基于miRNA的治疗中出现。
