1] Department of Clinical and Molecular Medicine, Sapienza University of Rome, Italy [2] Laboratory of Research and Diagnostics, Department of Surgery 'P.Valdoni', Sapienza University of Rome.
Cell Death Dis. 2013 Dec 5;4(12):e947. doi: 10.1038/cddis.2013.444.
In recent years, studies of cancer development and recurrence have been influenced by the cancer stem cells (CSCs)/cancer-initiating cells (CICs) hypothesis. According to this, cancer is sustained by highly positioned, chemoresistant cells with extensive capacity of self renewal, which are responsible for disease relapse after chemotherapy. Growth of cancer cells as three-dimensional non-adherent spheroids is regarded as a useful methodology to enrich for cells endowed with CSC-like features. We have recently reported that cell cultures derived from malignant pleural effusions (MPEs) of patients affected by adenocarcinoma of the lung are able to efficiently form spheroids in non-adherent conditions supplemented with growth factors. By expression profiling, we were able to identify a set of genes whose expression is significantly upregulated in lung tumor spheroids versus adherent cultures. One of the most strongly upregulated gene was stearoyl-CoA desaturase (SCD1), the main enzyme responsible for the conversion of saturated into monounsaturated fatty acids. In the present study, we show both by RNA interference and through the use of a small molecule inhibitor that SCD1 is required for lung cancer spheroids propagation both in stable cell lines and in MPE-derived primary tumor cultures. Morphological examination and image analysis of the tumor spheroids formed in the presence of SCD1 inhibitors showed a different pattern of growth characterized by irregular cell aggregates. Electron microscopy revealed that the treated spheroids displayed several features of cellular damage and immunofluorescence analysis on optical serial sections showed apoptotic cells positive for the M30 marker, most of them positive also for the stemness marker ALDH1A1, thus suggesting that the SCD1 inhibitor is selectively killing cells with stem-like properties. Furthermore, SCD1-inhibited lung cancer cells were strongly impaired in their in vivo tumorigenicity and ALDH1A1 expression. These results suggest that SCD1 is a critical target in lung cancer tumor-initiating cells.
近年来，癌症的发生和复发的研究受到癌症干细胞（CSCs）/癌症起始细胞（CICs）假说的影响。根据这一假说，癌症是由具有高度定位、化疗耐药和广泛自我更新能力的细胞维持的，这些细胞是化疗后疾病复发的罪魁祸首。培养的癌细胞形成三维非贴壁球体被认为是一种富集具有类似干细胞特征的细胞的有用方法。我们最近报道称，从肺癌腺癌患者的恶性胸腔积液（MPE）中获得的细胞培养物在补充生长因子的非贴壁条件下能够有效地形成球体。通过表达谱分析，我们能够鉴定出一组在肺肿瘤球体与贴壁培养物中表达显著上调的基因。上调最明显的基因之一是硬脂酰辅酶 A 去饱和酶（SCD1），它是将饱和脂肪酸转化为单不饱和脂肪酸的主要酶。在本研究中，我们通过 RNA 干扰和使用小分子抑制剂表明，SCD1 是稳定细胞系和 MPE 衍生的原发性肿瘤培养物中肺癌球体增殖所必需的。在 SCD1 抑制剂存在下形成的肿瘤球体的形态学检查和图像分析显示出不同的生长模式，其特征是不规则的细胞聚集。电子显微镜显示，处理过的球体显示出多种细胞损伤特征，免疫荧光分析光学连续切片显示 M30 标志物阳性的凋亡细胞，其中大多数也对干细胞标志物 ALDH1A1 阳性，这表明 SCD1 抑制剂选择性地杀死具有干细胞样特性的细胞。此外，SCD1 抑制的肺癌细胞在体内致瘤性和 ALDH1A1 表达方面受到严重损害。这些结果表明 SCD1 是肺癌起始细胞的关键靶点。
