Heparanase is known to enhance the progression of many cancer types and is associated with poor patient prognosis. We recently reported that after patients with multiple myeloma were treated with high dose chemotherapy, the tumor cells that emerged upon relapse expressed a much higher level of heparanase than was present prior to therapy. Because tumor cells having stemness properties are thought to seed tumor relapse, we investigated whether heparanase had a role in promoting myeloma stemness. When plated at low density and grown in serum-free conditions that support survival and expansion of stem-like cells, myeloma cells expressing a low level of heparanase formed tumor spheroids poorly. In contrast, cells expressing a high level of heparanase formed significantly more and larger spheroids than did the heparanase low cells. Importantly, heparanase-low expressing cells exhibited plasticity and were induced to exhibit stemness properties when exposed to recombinant heparanase or to exosomes that contained a high level of heparanase cargo. The spheroid-forming heparanase-high cells had elevated expression of GLI1, SOX2 and ALDH1A1, three genes known to be associated with myeloma stemness. Inhibitors that block the heparan sulfate degrading activity of heparanase significantly diminished spheroid formation and expression of stemness genes implying a direct role of the enzyme in regulating stemness. Blocking the NF-κB pathway inhibited spheroid formation and expression of stemness genes demonstrating a role for NF-κB in heparanase-mediated stemness. Myeloma cells made deficient in heparanase exhibited decreased stemness properties in vitro and when injected into mice they formed tumors poorly compared to the robust tumorigenic capacity of cells expressing higher levels of heparanase. These studies reveal for the first time a role for heparanase in promoting cancer stemness and provide new insight into its function in driving tumor progression and its association with poor prognosis in cancer patients.

中文翻译：

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乙酰肝素酶促进骨髓瘤干和体内肿瘤发生。

已知乙酰肝素酶可促进许多癌症类型的进展，并与患者预后不良有关。我们最近报道，对多发性骨髓瘤患者进行高剂量化疗后，复发后出现的肿瘤细胞表达的乙酰肝素酶水平高于治疗前。因为具有干性的肿瘤细胞被认为是导致肿瘤复发的种子，所以我们调查了乙酰肝素酶是否具有促进骨髓瘤干性的作用。当以低密度铺板并在无血清条件下生长以支持干细胞样细胞的存活和扩增时，表达低水平乙酰肝素酶的骨髓瘤细胞就很难形成肿瘤球体。相反，与低乙酰肝素酶细胞相比，表达高水平乙酰肝素酶的细胞形成了更多，更大的球体。重要的，低表达乙酰肝素酶的细胞在暴露于重组乙酰肝素酶或含有大量乙酰肝素酶的外泌体时，表现出可塑性，并被诱导表现出干性。形成类球体的乙酰肝素高细胞具有升高的GLI1，SOX2和ALDH1A1的表达，这三个基因与骨髓瘤干性相关。阻断硫酸乙酰肝素酶降解硫酸乙酰肝素酶活性的抑制剂可显着减少球状体的形成和茎基因的表达，这暗示着该酶在调节茎中的直接作用。阻断NF-κB通路可抑制球状体的形成和干性基因的表达，这表明NF-κB在乙酰肝素酶介导的干性中的作用。缺乏乙酰肝素酶的骨髓瘤细胞在体外表现出降低的干性，并且与表达更高水平乙酰肝素酶的细胞强大的致瘤能力相比，当注入小鼠体内时，它们形成的肿瘤较差。这些研究首次揭示了乙酰肝素酶在促进癌症干性中的作用，并为其在驱动肿瘤进展中的功能及其与癌症患者预后不良的关联提供了新的见解。