骨髓瘤细胞中生长因子独立性 1 的表达增强了它们的生长、存活和破骨细胞生成。
Growth factor independence 1 expression in myeloma cells enhances their growth, survival, and osteoclastogenesis.
机构信息
Department of Medicine, Division of Hematology-Oncology, Indiana University School of Medicine, 980 Walnut Street, Walther Hall, Room C346, Indianapolis, IN, 46202, USA.
Myeloma Unit, Department of Medicine and Surgery, University of Parma, Parma, Italy.
出版信息
J Hematol Oncol. 2018 Oct 4;11(1):123. doi: 10.1186/s13045-018-0666-5.
BACKGROUND
In spite of major advances in treatment, multiple myeloma (MM) is currently an incurable malignancy due to the emergence of drug-resistant clones. We previously showed that MM cells upregulate the transcriptional repressor, growth factor independence 1 (Gfi1), in bone marrow stromal cells (BMSCs) that induces prolonged inhibition of osteoblast differentiation. However, the role of Gfi1 in MM cells is unknown.
METHODS
Human primary CD138+ and BMSC were purified from normal donors and MM patients' bone marrow aspirates. Gfi1 knockdown and overexpressing cells were generated by lentiviral-mediated shRNA. Proliferation/apoptosis studies were done by flow cytometry, and protein levels were determined by Western blot and/or immunohistochemistry. An experimental MM mouse model was generated to investigate the effects of MM cells overexpressing Gfi1 on tumor burden and osteolysis in vivo.
RESULTS
We found that Gfi1 expression is increased in patient's MM cells and MM cell lines and was further increased by co-culture with BMSC, IL-6, and sphingosine-1-phosphate. Modulation of Gfi1 in MM cells had major effects on their survival and growth. Knockdown of Gfi1 induced apoptosis in p53-wt, p53-mutant, and p53-deficient MM cells, while Gfi1 overexpression enhanced MM cell growth and protected MM cells from bortezomib-induced cell death. Gfi1 enhanced cell survival of p53-wt MM cells by binding to p53, thereby blocking binding to the promoters of the pro-apoptotic BAX and NOXA genes. Further, Gfi1-p53 binding could be blocked by HDAC inhibitors. Importantly, inoculation of MM cells overexpressing Gfi1 in mice induced increased bone destruction, increased osteoclast number and size, and enhanced tumor growth.
CONCLUSIONS
These results support that Gfi1 plays a key role in MM tumor growth, survival, and bone destruction and contributes to bortezomib resistance, suggesting that Gfi1 may be a novel therapeutic target for MM.
背景
尽管在治疗方面取得了重大进展，但多发性骨髓瘤（MM）目前仍是一种无法治愈的恶性肿瘤，因为会出现耐药克隆。我们之前曾表明，MM 细胞在骨髓基质细胞（BMSCs）中上调转录抑制因子生长因子独立性 1（Gfi1），从而诱导成骨细胞分化的长期抑制。然而，Gfi1 在 MM 细胞中的作用尚不清楚。
方法
从正常供体和 MM 患者的骨髓抽吸物中纯化人原代 CD138+和 BMSC。通过慢病毒介导的 shRNA 生成 Gfi1 敲低和过表达细胞。通过流式细胞术进行增殖/凋亡研究，并通过 Western blot 和/或免疫组织化学测定蛋白水平。生成实验性 MM 小鼠模型以研究过表达 Gfi1 的 MM 细胞对体内肿瘤负担和溶骨性的影响。
结果
我们发现 Gfi1 在患者的 MM 细胞和 MM 细胞系中的表达增加，并通过与 BMSC、IL-6 和鞘氨醇 1-磷酸共培养而进一步增加。Gfi1 在 MM 细胞中的调节对其存活和生长有重大影响。Gfi1 敲低诱导 p53-wt、p53-突变和 p53 缺失的 MM 细胞凋亡，而过表达 Gfi1 则增强 MM 细胞的生长并保护 MM 细胞免受硼替佐米诱导的细胞死亡。Gfi1 通过与 p53 结合增强 p53-wt MM 细胞的细胞存活，从而阻止与促凋亡 BAX 和 NOXA 基因的启动子结合。此外，Gfi1-p53 结合可被 HDAC 抑制剂阻断。重要的是，在小鼠中接种过表达 Gfi1 的 MM 细胞可导致骨破坏增加、破骨细胞数量和大小增加以及肿瘤生长增强。
结论
这些结果支持 Gfi1 在 MM 肿瘤生长、存活和骨破坏中发挥关键作用，并有助于硼替佐米耐药，表明 Gfi1 可能是 MM 的一个新的治疗靶点。
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