miRNA‐ and cytokine‐associated extracellular vesicles mediate squamous cell carcinomas

Abstract

Exosomes, or small extracellular vesicles (sEVs), serve as intercellular messengers with key roles in normal and pathological processes. Our previous work had demonstrated that Dsg2 expression in squamous cell carcinoma (SCC) cells enhanced both sEV secretion and loading of pro-mitogenic cargo. In this study, using wild-type Dsg2 and a mutant form that is unable to be palmitoylated (Dsg2cacs), we investigated the mechanism by which Dsg2 modulates SCC tumour development and progression through sEVs. We demonstrate that palmitoylation was required for Dsg2 to regulate sub-cellular localisation of lipid raft and endosomal proteins necessary for sEV biogenesis. Pharmacological inhibition of the endosomal pathway abrogated Dsg2-mediated sEV release. In murine xenograft models, Dsg2-expressing cells generated larger xenograft tumours as compared to cells expressing GFP or Dsg2cacs. Co-treatment with sEVs derived from Dsg2over-expressing cells increased xenograft size. Cytokine profiling revealed, Dsg2 enhanced both soluble and sEV-associated IL-8 and miRNA profiling revealed, Dsg2 down-regulated both cellular and sEV-loaded miR-146a. miR-146a targets IRAK1, a serine-threonine kinase involved in IL-8 signalling. Treatment with a miR-146a inhibitor up-regulated both IRAK1 and IL-8 expression. RNAseq analysis of HNSCC tumours revealed a correlation between Dsg2 and IL-8. Finally, elevated IL-8 plasma levels were detected in a subset of HNSCC patients who did not respond to immune checkpoint therapy, suggesting that these patients may benefit from prior anti-IL-8 treatment. In summary, these results suggest that intercellular communication through cell-cell adhesion, cytokine release and secretion of EVs are coordinated, and critical for tumour growth and development, and may serve as potential prognostic markers to inform treatment options.

Cytokine Profiling in Low- and High-Density Small Extracellular Vesicles from Epidermoid Carcinoma Cells

“…We recently demonstrated that the membrane protein desmoglein 2 (Dsg2) modulates sEV biogenesis through the endocytic pathway (Overmiller et al, 2017;Flemming et al, 2020).…”

Paradoxical Roles of Desmosomal Components in Head and Neck Cancer

“…In vivo, associations between DSG2 and IL-8 have been demonstrated in patients with HNSCC. Furthermore, the oncogenic ability of DSG2 in SCC was correlated with the EV level [87]. These results suggest that intercellular communication can be coordinated through the secretion of DSG2 and EVs, critical for tumor growth, and may serve as a potential biomarker to guide treatment regimens.…”

“…The palmitoylation of DSG2 alters the trafficking of membrane raft proteins and early endosomal proteins. In the xenograft model, DSG2 promoted tumor growth and reduced this effect considerably with overexpression of non-palmitoylated DSG2 in cells [87]. These phenomena suggest that the post-translational modification of desmosomal cadherins is crucial in deciding its role in HNC.…”

Evaluation of the Ultrastructure and Expression of Desmoglein 2 in Breast Cancer: A Novel Biomarker

“…Kai et al showed that DSG2 expression is increased in lung cancer, and decreased regulation could suppress tumor growth [26]. Similarly, Barber et al, Abulrob et al, Plus Kamekura et al found that DSG2 de ciency leads to inhibition of cell proliferation and tumor growth in colon epithelial cancer [27][28][29]. Shuhang showed that desmoglein 2 is a biomarker that causes tumor proliferation and metastasis and is associated with a poor prognosis in the early stages of cervical cancer [30].…”