Development of dual targeting therapy for cancer stem cells and niche

在包括癌症干细胞在内的多种人类癌症中，已经描述了Hedgehog（Hh）信号的异常再激活。然而，骨髓（BM）微环境Hh信号系统在髓系肿瘤发生发展中的作用尚不清楚。在这项研究中，我们评估了Hh相关蛋白在正常人CD34+细胞、CD34+白血病/发育不良细胞和BM基质细胞中的表达。印度hedgehog基因（Ihh）及其信号换能器SMO在CD34+急性髓系白血病（AML）和骨髓增生异常综合征（MDS）衍生细胞中均有表达，提示Ihh可能以自分泌方式起作用。值得注意的是，内在Hh信号抑制剂，人刺猬相互作用蛋白（HHIP）在AML/ mds相关基质细胞中的表达明显低于健康供体来源的基质细胞。BM基质细胞中HHIP的表达水平与SMO+白血病细胞的支持活性高度相关。去甲基化剂5-aza-dC通过去甲基化HHIP基因来恢复HHIP的表达，并降低AML/ mds相关基质细胞的白血病支持活性。5-aza-dC的这种作用可以通过hip shRNA转移到基质细胞中来消除。有趣的是，hhip减少的基质细胞优先向释放ihh的白血病细胞迁移。这些结果表明，抑制间质hip表达可能参与了AML/MDS的进展。

Aberrant reactivation of Hedgehog(Hh) signaling has been described in a wide variety of human cancers including cancer stem cells. However, involvement of Hh signaling system in bone marrow(BM) microenvironment in the development of myeloid neoplasm has remained unclear. In this study, we assessed the expression of Hh related proteins in normal human CD34+cells, CD34+leukemic/dysplastic cells and BM stromal cells. Both Indian hedgehog(Ihh) and its signal transducer, SMO were expressed in CD34+acute myeloid leukemia(AML) and myelodysplastic syndrome(MDS) derived cells, suggesting that Ihh could effect in autocrine manner. Remarkably, the intrinsic Hh signaling inhibitor, human hedgehog-interacting protein(HHIP) expression in AML/MDS-associated stromal cells was drastically lower than that in healthy donor derived stromal cells. Moreover, the HHIP expression level in BM stromal cells highly correlated with supporting activity of SMO+leukemic cells. Demethylating agent 5-aza-dC rescued the HHIP expression via demethylation of HHIP gene and reduced the leukemia-supporting activity of AML/MDS-associated stromal cells. This effect of 5-aza-dC could be negated by HHIP shRNA transfer into stromal cells. Interestingly, HHIP-reduced stromal cells preferentially migrated toward Ihh-releasing leukemic cells. These results indicate that suppression of stromal HHIP expression could be involved in the progression of AML/MDS.