Institute of Life Sciences, Chongqing Medical University, 1 Yi Xue Yuan Road, Yuzhong District, Chongqing, 400016, People's Republic of China.
The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, China.
Cell Commun Signal. 2022 Mar 2;20(1):22. doi: 10.1186/s12964-022-00827-1.
The genesis and developments of solid tumors, analogous to the renewal of healthy tissues, are driven by a subpopulation of dedicated stem cells, known as cancer stem cells (CSCs), that exhibit long-term clonal repopulation and self-renewal capacity. CSCs may regulate tumor initiation, growth, dormancy, metastasis, recurrence and chemoresistance. While autophagy has been proposed as a regulator of the stemness of CSCs, the underlying mechanisms requires further elucidation.
The CSC component in human melanoma cell lines M14 and A375 was isolated and purified by repetitive enrichments for cells that consistently display anchorage-independent spheroid growth. The stemness properties of the CSCs were confirmed in vitro by the expressions of stemness marker genes, the single-cell cloning assay and the serial spheroid formation assay. Subcutaneous tumor transplantation assay in BALB/c nude mice was performed to test the stemness properties of the CSCs in vivo. The autophagic activity was confirmed by the protein level of LC3 and P62, mRFP-LC3B punta and cytoplasmic accumulation of autolysosomes. The morphology of ER was detected with transmission electron microscopy.
In the present study, by employing stable CSC cell lines derived from human melanoma cell lines M14 and A375, we show for the first time that Sec23a inhibits the self-renewal of melanoma CSCs via inactivation of ER-phagy. Mechanistically, inhibition of Sec23a reduces ER stress and consequently FAM134B-induced ER-phagy. Furthermore, TCGA data mining and analysis show that Sec23a is a favorable diagnostic and prognostic marker for human skin cutaneous melanoma.
This study has elucidated a new mechanism underlying the regulation of autophagy on stemness, i.e. CSCs can exploit the SEC23A/ER-stress/FAM134B/ER-phagy axis for the self-renewal. These observations provide new ideas for exploration of the regulatory network of CSC self-renewal to develop CSCs-based therapy strategies for malignant tumors. Video Abstract.
与健康组织的更新类似，实体瘤的发生和发展是由一群专门的干细胞驱动的，这些干细胞被称为癌症干细胞（CSC），它们具有长期的克隆再殖和自我更新能力。CSC 可能调节肿瘤的起始、生长、休眠、转移、复发和化疗耐药性。虽然自噬已被提议作为 CSC 干性的调节剂，但潜在的机制仍需要进一步阐明。
通过反复富集能够持续表现出无锚定球体生长的细胞，从人黑色素瘤细胞系 M14 和 A375 中分离和纯化 CSC 成分。通过干细胞标志物基因的表达、单细胞克隆测定和连续球体形成测定，在体外确认 CSCs 的干性特性。在 BALB/c 裸鼠中进行皮下肿瘤移植实验，以体内检测 CSCs 的干性特性。通过 LC3 和 P62 的蛋白水平、mRFP-LC3B 点状和细胞质中自噬溶酶体的积累来确认自噬活性。用透射电子显微镜检测 ER 的形态。
在本研究中，通过使用源自人黑色素瘤细胞系 M14 和 A375 的稳定 CSC 细胞系，我们首次表明 Sec23a 通过失活 ER 自噬来抑制黑色素瘤 CSCs 的自我更新。在机制上，Sec23a 的抑制减少了 ER 应激，从而减少了 FAM134B 诱导的 ER 自噬。此外，TCGA 数据挖掘和分析表明 Sec23a 是人类皮肤黑色素瘤的有利诊断和预后标志物。
本研究阐明了自噬调节干性的新机制，即 CSCs 可以利用 SEC23A/ER 应激/FAM134B/ER 自噬轴进行自我更新。这些发现为探索 CSC 自我更新的调控网络提供了新的思路，以开发基于 CSC 的恶性肿瘤治疗策略。
