The pro-tumorigenic properties of heparanase are well documented, and heparanase inhibitors are being evaluated clinically as anti-cancer therapeutics. In contrast, the role of heparanase 2 (Hpa2), a close homolog of heparanase, in cancer is largely unknown. Previously, we have reported that in head and neck cancer, high levels of Hpa2 are associated with prolonged patient survival and decreased tumor cell dissemination to regional lymph nodes, suggesting that Hpa2 functions to restrain tumorigenesis. Also, patients with high levels of Hpa2 were diagnosed as low grade and exhibited increased expression of cytokeratins, an indication that Hpa2 promotes or maintains epithelial cell differentiation and identity. To reveal the molecular mechanism underlying the tumor suppressor properties of Hpa2, and its ability to induce the expression of cytokeratin, we employed overexpression as well as gene editing (Crispr) approaches, combined with gene array and RNAseq methodologies. At the top of the list of many genes found to be affected by Hpa2 was Sox2. Here we provide evidence that silencing of Sox2 resulted in bigger tumors endowed with reduced cytokeratin levels, whereas smaller tumors were developed by cells overexpressing Sox2, suggesting that in head and neck carcinoma, Sox2 functions to inhibit tumor growth. Notably, Hpa2-null cells engineered by Crispr/Cas 9, produced bigger tumors vs control cells, and rescue of Hpa2 attenuated tumor growth. These results strongly imply that Hpa2 functions as a tumor suppressor in head and neck cancer, involving Sox2 upregulation mediated, in part, by the high-affinity interaction of Hpa2 with heparan sulfate.

乙酰肝素酶的促肿瘤特性已得到充分证明，并且正在临床评估乙酰肝素酶抑制剂作为抗癌治疗剂。相比之下，乙酰肝素酶 2 (Hpa2) 是乙酰肝素酶的密切同源物，在癌症中的作用在很大程度上是未知的。以前，我们曾报道在头颈癌中，高水平的 Hpa2 与延长患者生存期和减少肿瘤细胞向区域淋巴结的传播有关，这表明 Hpa2 具有抑制肿瘤发生的作用。此外，具有高水平 Hpa2 的患者被诊断为低级别并表现出细胞角蛋白表达增加，这表明 Hpa2 促进或维持上皮​​细胞分化和特性。为了揭示 Hpa2 的抑癌特性的分子机制，及其诱导细胞角蛋白表达的能力，我们采用过表达和基因编辑 (Crispr) 方法，结合基因阵列和 RNAseq 方法。在发现受 Hpa2 影响的许多基因列表的顶部是 Sox2。在这里，我们提供的证据表明，Sox2 的沉默导致较大的肿瘤细胞角蛋白水平降低，而较小的肿瘤是由过表达 Sox2 的细胞形成的，这表明在头颈癌中，Sox2 起到抑制肿瘤生长的作用。值得注意的是，由 Crispr/Cas 9 改造的 Hpa2 缺失细胞与对照细胞相比产生了更大的肿瘤，并且 Hpa2 的拯救减弱了肿瘤的生长。这些结果强烈暗示 Hpa2 在头颈癌中起到肿瘤抑制因子的作用，涉及 Sox2 上调介导的部分，