CD44s is a crucial ATG7 downstream regulator for stem-like property, invasion, and lung metastasis of human bladder cancer (BC) cells.

Abstract

Over half a million US residents are suffering with bladder cancer (BC), which costs a total $4 billion in treatment annually. Although recent studies report that autophagy-related gene 7 (ATG7) is overexpressed in BCs, the regulatory effects of ATG7 on cancer stem-like phenotypes and invasion have not been explored yet. Current studies demonstrated that the deficiency of ATG7 by its shRNA dramatically reduced sphere formation and invasion in vitro, as well as lung metastasis in vivo in human invasive BC cells. Further studies indicated that the knockdown of ATG7 attenuated the expression of CD44 standard (CD44s), while ectopic introduction of CD44s, was capable of completely restoring sphere formation, invasion, and lung metastasis in T24T(shATG7) cells. Mechanistic studies revealed that ATG7 overexpression stabilized CD44s proteins accompanied with upregulating USP28 proteins. Upregulated USP28 was able to bind to CD44s and remove the ubiquitin group from CD44s' protein, resulting in the stabilization of CD44s protein. Moreover, ATG7 inhibition stabilized AUF1 protein and thereby reduced tet1 mRNA stability and expression, which was able to demethylate usp28 promoter, reduced USP28 expression, finally promoting CD44s degradation. In addition, CD44s was defined to inhibit degradation of RhoGDIβ, which in turn promotes BC invasion. Our results demonstrate that CD44s is a key ATG7 downstream regulator of the sphere formation, invasion, and lung metastasis of BCs, providing significant insight into understanding the BC invasions, metastasis, and stem-like properties.

• Authors: Junlan Zhu, Grace Huang, Xiaohui Hua, Yang Li, Huiying Yan, Xun Che, Zhongxian Tian, Huating Liufu, Chao Huang, Jingxia Li, Jiheng Xu, Wei Dai, Haishan Huang, Chuanshu Huang
• Journal: Oncogene (Oncogene) Vol. 38 Issue 17 Pg. 3301-3315 (04 2019) ISSN: 1476-5594 [Electronic] England
• PMID: 30635654 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• CD44 protein, human
• Hyaluronan Receptors
• RNA, Small Interfering
• Mixed Function Oxygenases
• Ubiquitin Thiolesterase
• Atg7 protein, human
• Autophagy-Related Protein 7

Topics

• Autophagy-Related Protein 7 (genetics, metabolism)
• Cell Line, Tumor
• Humans
• Hyaluronan Receptors (genetics, metabolism)
• Lung Neoplasms (genetics, pathology, secondary)
• Mixed Function Oxygenases (genetics, metabolism)
• Neoplasm Metastasis
• Promoter Regions, Genetic
• RNA, Small Interfering (genetics)
• Ubiquitin Thiolesterase (genetics, metabolism)
• Up-Regulation
• Urinary Bladder Neoplasms (genetics, metabolism, pathology)