Breast Cancer Res. 2014 Mar 26;16(2):R29. doi: 10.1186/bcr3631.
Although breast phyllodes tumors are rare, there is no effective therapy other than surgery. Little is known about their tumor biology. A malignant phyllodes tumor contains heterologous stromal elements, and can transform into rhabdomyosarcoma, liposarcoma and osteosarcoma. These versatile properties prompted us to explore their possible relationship to mesenchymal stem cells (MSCs) and to search for the presence of cancer stem cells (CSCs) in phyllodes tumors.
Paraffin sections of malignant phyllodes tumors were examined for various markers by immunohistochemical staining. Xenografts of human primary phyllodes tumors were established by injecting freshly isolated tumor cells into the mammary fat pad of non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice. To search for CSCs, xenografted tumor cells were sorted into various subpopulations by flow cytometry and examined for their in vitro mammosphere forming capacity, in vivo tumorigenicity in NOD-SCID mice and their ability to undergo differentiation.
Immunohistochemical analysis revealed the expression of the following 10 markers: CD44, CD29, CD106, CD166, CD105, CD90, disialoganglioside (GD2), CD117, Aldehyde dehydrogenase 1 (ALDH), and Oct-4, and 7 clinically relevant markers (CD10, CD34, p53, p63, Ki-67, Bcl-2, vimentin, and Globo H) in all 51 malignant phyllodes tumors examined, albeit to different extents. Four xenografts were successfully established from human primary phyllodes tumors. In vitro, ALDH+ cells sorted from xenografts displayed approximately 10-fold greater mammosphere-forming capacity than ALDH- cells. GD2+ cells showed a 3.9-fold greater capacity than GD2- cells. ALDH+/GD2+cells displayed 12.8-fold greater mammosphere forming ability than ALDH-/GD2- cells. In vivo, the tumor-initiating frequency of ALDH+/GD2+ cells were up to 33-fold higher than that of ALDH+ cells, with as few as 50 ALDH+/GD2+ cells being sufficient for engraftment. Moreover, we provided the first evidence for the induction of ALDH+/GD2+ cells to differentiate into neural cells of various lineages, along with the observation of neural differentiation in clinical specimens and xenografts of malignant phyllodes tumors. ALDH+ or ALDH+/GD2+ cells could also be induced to differentiate into adipocytes, osteocytes or chondrocytes.
Our findings revealed that malignant phyllodes tumors possessed many characteristics of MSC, and their CSCs were enriched in ALDH+ and ALDH+/GD2+ subpopulations.
尽管乳腺叶状肿瘤较为罕见，但除手术外，尚无其他有效疗法。目前对其肿瘤生物学特性了解甚少。恶性叶状肿瘤含有异源基质成分，并可转化为横纹肌肉瘤、脂肪肉瘤和骨肉瘤。这些多功能特性促使我们探索其与间充质干细胞（MSCs）的可能关系，并寻找叶状肿瘤中是否存在癌症干细胞（CSCs）。
通过免疫组织化学染色法检测恶性叶状肿瘤石蜡切片中的各种标志物。通过将新鲜分离的肿瘤细胞注射到非肥胖型糖尿病-严重联合免疫缺陷（NOD-SCID）小鼠的乳腺脂肪垫中，建立人原发性叶状肿瘤的异种移植物。为了寻找 CSCs，通过流式细胞术将异种移植物肿瘤细胞分选成不同亚群，并检测其体外形成乳腺球体的能力、在 NOD-SCID 小鼠体内的致瘤性以及分化能力。
免疫组织化学分析显示，在 51 例恶性叶状肿瘤中均表达以下 10 种标志物：CD44、CD29、CD106、CD166、CD105、CD90、二唾液酸神经节苷脂（GD2）、CD117、醛脱氢酶 1（ALDH）和 Oct-4，以及 7 种临床相关标志物（CD10、CD34、p53、p63、Ki-67、Bcl-2、波形蛋白和Globoh），但表达程度不同。从人原发性叶状肿瘤成功建立了 4 个异种移植物。体外，来自异种移植物的 ALDH+细胞的乳腺球体形成能力比 ALDH-细胞高约 10 倍。GD2+细胞的形成能力比 GD2-细胞高 3.9 倍。ALDH+/GD2+细胞的乳腺球体形成能力比 ALDH-/GD2-细胞高 12.8 倍。体内，ALDH+/GD2+细胞的肿瘤起始频率比 ALDH+细胞高 33 倍，仅需 50 个 ALDH+/GD2+细胞即可进行移植。此外，我们首次提供了诱导 ALDH+/GD2+细胞分化为各种谱系神经细胞的证据，同时观察到恶性叶状肿瘤的临床标本和异种移植物中的神经分化。ALDH+或 ALDH+/GD2+细胞也可被诱导分化为脂肪细胞、成骨细胞或软骨细胞。
我们的研究结果表明，恶性叶状肿瘤具有许多 MSC 的特征，其 CSCs 富集于 ALDH+和 ALDH+/GD2+亚群中。
