Stem Cell Laboratory, Advanced Biotechnology Center, 16132 Genova, Italy.
Haematologica. 2011 Jul;96(7):1015-23. doi: 10.3324/haematol.2010.029736. Epub 2011 Apr 12.
Chronic lymphocytic leukemia cells are characterized by an apparent longevity in vivo which is lost when they are cultured in vitro. Cellular interactions and factors provided by the microenvironment appear essential to cell survival and may protect leukemic cells from the cytotoxicity of conventional therapies. Understanding the cross-talk between leukemic cells and stroma is of interest for identifying signals supporting disease progression and for developing novel therapeutic strategies.
Different cell types, sharing a common mesenchymal origin and representative of various bone marrow components, were used to challenge the viability of leukemic cells in co-cultures and in contact-free culture systems. Using a bioinformatic approach we searched for genes shared by lineages prolonging leukemic cell survival and further analyzed their biological role in signal transduction experiments.
Human bone marrow stromal cells, fibroblasts, trabecular bone-derived cells and an osteoblast-like cell line strongly enhanced survival of leukemic cells, while endothelial cells and chondrocytes did not. Gene expression profile analysis indicated two soluble factors, hepatocyte growth factor and CXCL12, as potentially involved. We demonstrated that hepatocyte growth factor and CXCL12 are produced only by mesenchymal lineages that sustain the survival of leukemic cells. Indeed chronic lymphocytic leukemic cells express a functional hepatocyte growth factor receptor (c-MET) and hepatocyte growth factor enhanced the viability of these cells through STAT3 phosphorylation, which was blocked by a c-MET tyrosine kinase inhibitor. The role of hepatocyte growth factor was confirmed by its short interfering RNA-mediated knock-down in mesenchymal cells.
The finding that hepatocyte growth factor prolongs the survival of chronic lymphocytic leukemic cells is novel and we suggest that the interaction between hepatocyte growth factor-producing mesenchymal and neoplastic cells contributes to maintenance of the leukemic clone.
慢性淋巴细胞白血病细胞在体内表现出明显的长寿性，但在体外培养时会丧失这种特性。细胞间相互作用和微环境提供的因子对于细胞存活至关重要，它们可以保护白血病细胞免受常规治疗的细胞毒性作用。了解白血病细胞与基质之间的相互作用对于确定支持疾病进展的信号以及开发新的治疗策略具有重要意义。
使用具有共同间充质起源并代表各种骨髓成分的不同细胞类型，在共培养和无接触培养系统中挑战白血病细胞的活力。我们使用生物信息学方法搜索延长白血病细胞存活的谱系共享基因，并进一步在信号转导实验中分析它们的生物学作用。
人骨髓基质细胞、成纤维细胞、小梁骨衍生细胞和成骨样细胞系强烈增强白血病细胞的存活，而内皮细胞和软骨细胞则没有。基因表达谱分析表明两种可溶性因子，肝细胞生长因子和 CXCL12，可能参与其中。我们证明只有维持白血病细胞存活的间充质谱系才会产生肝细胞生长因子和 CXCL12。事实上，慢性淋巴细胞白血病细胞表达功能性肝细胞生长因子受体（c-MET），肝细胞生长因子通过 STAT3 磷酸化增强这些细胞的活力，而 c-MET 酪氨酸激酶抑制剂可阻断该作用。肝细胞生长因子在间充质细胞中的短干扰 RNA 介导敲低证实了其作用。
肝细胞生长因子延长慢性淋巴细胞白血病细胞存活的发现是新颖的，我们认为肝细胞生长因子产生的间充质和肿瘤细胞之间的相互作用有助于白血病克隆的维持。
