We have previously demonstrated cancer stem cell (CSC) subpopulations in head and neck metastatic malignant melanoma (HNmMM), and the expression of components of the renin-angiotensin system (RAS) by these CSCs. Cathepsins B, D and G are involved in carcinogenesis and constitute bypass loops of the RAS. This study investigated the expression and localization of cathepsins B, D and G, in relation to these CSCs. Immunohistochemical staining demonstrated expression of cathepsins B, D and G in HNmMM sections from all 20 patients. Western blotting confirmed the presence of cathepsins B and D proteins in all six HNmMM tissue samples and four HNmMM-derived primary cell lines. RT-qPCR showed transcript expression of cathepsins B, D and G in all six HNmMM tissue samples, and cathepsins B and D but not cathepsin G in all four HNmMM-derived primary cell lines. Enzymatic activity assays demonstrated cathepsins B and D were active in all six HNmMM tissue samples. Immunofluorescence staining performed on two of the HNmMM tissue samples demonstrated expression of cathepsins B and D by the CSCs, and cathepsin G by cells within the peritumoral. Our novel findings suggest the possibility of targeting these CSCs by modulation of paracrine RAS signaling.

中文翻译：

---

头颈部转移性恶性黑色素瘤中癌症干细胞表达组织蛋白酶 B 和 D。

我们之前已经证明了头颈部转移性恶性黑色素瘤（HNmMM）中的癌症干细胞（CSC）亚群，以及这些CSC表达的肾素-血管紧张素系统（RAS）成分。组织蛋白酶 B、D 和 G 参与癌发生并构成 RAS 的旁路环。本研究调查了与这些 CSC 相关的组织蛋白酶 B、D 和 G 的表达和定位。免疫组织化学染色显示所有 20 名患者的 HNmMM 切片中均表达组织蛋白酶 B、D 和 G。蛋白质印迹证实所有六个 HNmMM 组织样本和四个 HNmMM 衍生的原代细胞系中都存在组织蛋白酶 B 和 D 蛋白。RT-qPCR 显示所有 6 个 HNmMM 组织样本中组织蛋白酶 B、D 和 G 的转录表达，以及所有 4 个 HNmMM 衍生的原代细胞系中组织蛋白酶 B 和 D 的转录表达，但组织蛋白酶 G 不表达。酶活性测定表明组织蛋白酶 B 和 D 在所有 6 个 HNmMM 组织样本中均具有活性。对两个 HNmMM 组织样本进行的免疫荧光染色表明，CSC 表达组织蛋白酶 B 和 D，瘤周细胞表达组织蛋白酶 G。我们的新发现表明通过调节旁分泌 RAS 信号传导来靶向这些 CSC 的可能性。