OSCC cell-secreted exosomal CMTM6 induced M2-like macrophages polarization via ERK1/2 signaling pathway
Authors: Hua-Yang Fan
Jian Jiang
Ya-Ling Tang
Sha-Sha Wang
Mei Zhang
Xin Pang
Jia-Shun Wu
Hao-Fan Wang
Xin-Hua Liang
Journal: Cancer Immunology Immunotherapy (2021)
Discipline: IMMUNOLOGY
Keywords: CKLF-like MARVEL transmembrane domain-containing 6; Exosome; Macrophage; Oral squamous cell carcinoma; PD-L1.
Affiliations: State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases and Department of Oral and Maxillofacial Surgery, Hospital of Stomatology, Sichuan University, No.14, Sec. 3, Renminnan Road, Chengdu, 610041, West China, China., Department of Head and Neck Surgery, Sichuan Cancer Center, School of Medicine, Sichuan Cancer Hospital and Institute, University of Electronic Science and Technology of China, Chengdu, Sichuan, China., State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases and Department of Oral and Maxillofacial Surgery, Hospital of Stomatology, Sichuan University, No.14, Sec. 3, Renminnan Road, Chengdu, 610041, West China, China. .

Abstract:  Background: CKLF-like MARVEL transmembrane domain-containing 6 (CMTM6) is a critical regulator of tumor immunology among various cancers. However, the role and underlying molecular mechanism of CMTM6 in oral squamous cell carcinoma (OSCC) progression remains unclear. Methods: The expression of CMTM6, PD-L1 and CD163 in OSCC tissues were detected by immunohistochemistry on tissue microarray. The effect of CMTM6 knockdown on OSCC cells and macrophage polarization were analyzed by CCK-8 assay, apoptotic assay, would-healing assay, transwell assay and qPCR. OSCC cell derived exosomes were obtained by ultracentrifugation and the mechanistic studies were conducted by qPCR and Western Blot. 4-Nitroquinoline N-oxide (4NQO) induced OSCC mice were used for verifying the effect of CMTM6 downregulation on M2 macrophage infiltration and tumor growth. Results: In OSCC samples, higher CMTM6 expression has been obviously associated with higher pathological stage of OSCC patients, CD163 + macrophages infiltration and PD-L1 expression. CMTM6 knockdown of OSCC cells inhibited proliferative, migrative and invasive abilities of OSCC cells, as well as inhibited M2 macrophage polarization in vitro with downregulating PD-L1 expression. Importantly, exosomes from OSCC cells shuttled CMTM6 to macrophages and promoted M2-like macrophage polarization through activating ERK1/2 signaling. In addition, in 4NQO-induced OSCC mice, CMTM6 level was positively associated with CD163, CD206 and PD-L1 as well as M2-like macrophage infiltration. Conclusion: OSCC cell-secreted exosomal CMTM6 induces M2-like macrophages polarization to promote malignant progression via ERK1/2 signaling pathway, revealing a novel crosstalk between cancer cells and immune cells in OSCC microenvironment. 

Retracted: No

PubPeer comments:
 Figure 2E has a duplication after scaling up, with likely cranked up brightness of Si-NC * SCC25 ![file] , 
 This publication does not establish a role for exosomes, as suggested by the title. Exosomes are extracellular vesicles, EVs, from the multivesicular body, and as a population, they have similar composition and size as other EVs. Tetraspanin and other markers shown here in a single Western blot lane are not exclusive to exosomes, and no assays are done to rule out the presence of other EVs. As a result, use of the term  exosome is not indicated. Also, although the methods state that EV-depleted FBS was used for cell culture, the method and means of verifying this depletion are not shared. Even rigorous depletion of FBS leaves small EVs and numerous lipoprotein particles and protein aggregates that are stained by lipid dyes. The conclusions about exosomes and their uptake are not well supported. ,