骨髓基质细胞中β4GALT1介导高危MDS克隆细胞增殖和耐药的机制研究

Chemoresistance is very common in patients with advanced myelodysplastic syndromes (MDS). The interaction between the bone marrow microenvironment and malignant hematopoietic cells (clonal cells) can result in the protection of clonal cells from chemotherapy in MDS. Two human bone marrow stromal cell lines, HS5 and HS27a, co-cultured with myeloid cells, have frequently been used in studies of cross talk between cells in the bone marrow microenvironment and clonal cells. In previous studies, we suggest that HS27a, but not HS5, 'traveled' in direct contact with MDS precursors and enabled their propagation in murine model. Later, we found that HS27a cells had higher levels of β4GALT1 than HS5 cells, and overexpressing β4GALT1 in HS5 cells protected MDS cells from chemotherapeutic drugs. The preliminary data showed that overexpressing β4GALT1 in HS5 cells enhanced the level of CXCL1, which can facilitate cancer cell proliferation and drug resistance. Furthermore, overexpressing β4GALT1 in HS5 cells decreased p53 expression, which is one of the key factors in regulating CXCL1. Taken together, our hypothesis is that: β4GALT1 can enhance CXCL1 expression via decreasing p53 in stroma cells, and upon their contact in regulating cell proliferation and drug resistance of MDS cells. This proposal will evaluate the correlation of β4GALT1 expression and the development as well as chemoresistance in patients with MDS, will clarify the pathway from β4GALT1 to CXCL1 in stromal cells and its role in regulating cell proliferation and chemoresistance of MDS cells, and will validate our hypothesis by xenotransplantation murine model.Our proposal tries to lay the foundation for tackling MDS from a different angle and improve current theraputics.

高危MDS病人常对化疗药物的耐药而影响治疗效果。研究微环境影响MDS细胞化疗耐药有助于改进治疗策略。申请人在前期工作发现β4GALT1基因在基质细胞HS27a中表达高于HS5，而HS27a比HS5显著促进MDS细胞在小鼠体内的增殖。预实验发现过表达β4GALT1的HS5细胞与MDS细胞共培养时显著提高MDS细胞的耐药性；过表达β4GALT1促进基质细胞CXCL1的分泌，CXCL1则能促进肿瘤细胞的增殖并提高其耐药性；在HS5中过表达β4GALT1能抑制p53表达，而低水平的p53是促进CXCL1表达的关键因素。因此，本项目提出：β4GALT1下调p53促进CXCL1分泌，从而影响MDS细胞的增殖和耐药。项目将评估β4GALT1表达与MDS病情发展及耐药的相关性，阐明基质细胞通过β4GALT1-p53-CXCL1这条主线影响MDS细胞增殖和耐药性的机制，以期为MDS的临床诊疗开拓思路。

骨髓增生异常综合征（MDS）是一组起源于骨髓造血干细胞的髓系恶性克隆性疾病，存在明显的异质性。化疗是治疗高危MDS病人的常规手段，但在临床上部分MDS病人出现不同程度的耐药性。本研究发现MDS患者骨髓基质细胞中B4GALT1和LacNAc的表达显著高于健康志愿者，将髓系恶性克隆细胞株如KG1a、SKM1以及原代MDS CD34+细胞与HS5共培养后能显著增加HS5细胞中B4GALT1的表达。在HS5中过表达B4GALT1（HS5B4）并与髓系恶性克隆细胞共培养可以显著增强后者对化疗药物（阿糖胞苷和多柔比星）的耐药性。探究其分子机制发现：HS5B4细胞条件培养基中趋化因子CXCL1的含量显著增加。CXCL1可降低髓系恶性克隆细胞活性氧水平并以此提高其对化疗药物的耐受。本部分结果证实在基质细胞中过表达B4GALT1，导致p53蛋白上LacNAc糖链修饰增多，泛素化水平上调，从而激活NF-κB信号通路，上调CXCL1表达。在血液学的研究中，骨髓微环境中基质细胞和造血干/祖细胞之间的相互作用越来越受关注。在 MDS 的恶性造血环境中，基质细胞与恶性髓系克隆细胞存在着双向的影响，其中糖基化在细胞间的相互作用起着广泛的调节作用。对微环境中糖相关蛋白的研究将有助于深入了解微环境中各细胞组分间的相互作用，为血液疾病的治疗提高一些新的思路。

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