EGFR activation induced Snail-dependent EMT and myc-dependent PD-L1 in human salivary adenoid cystic carcinoma cells

Abstract

Epithelial-to-mesenchymal transition (EMT) confers cancer cells the ability of invasion and metastasis. However, how does EMT contribute to evasion of immune surveillance is unclear, especially in salivary adenoid cystic carcinoma (SACC). In this study, we investigated the molecular link between EGF-induced EMT and the immune checkpoint ligand programmed death-ligand 1 (PD-L1) by immunoprecipitation (IP) and Westernblot analysis. Cell migration and invasion activity was assayed by transwell assay. Immunohistochemical (IHC) staining analysis was performed for measurement of EMT markers and PD-L1 expression levels in tumor tissues. We found that EGF-induced EGFR activation stabilized Snail expression and induced EMT in SACC. Interestingly, EGFR activation induced simultaneously both EMT and PD-L1 in SACC. Importantly, knockdown of Snail greatly suppressed EGF-induced EMT, but not EGF-induced PD-L1 expression; whereas knockdown of c-Myc strongly repressed PD-L1 expression, but not snail expression and EMT. The molecular link is strongly supported by robust correlations between the EMT markers and PD-L1 expression in human cancer samples.These results suggest that EGFR activated EMT and PD-L1 via two distinct mechanisms. EGFR activation induced EMT and PD-L1 expression in SACC. Snail is required for EGF-induced EMT, but not PD-L1 expression; whereas c-Myc is required for EGFR-mediated PD-L1 upregulation but not EMT. Thus, targeting activated EGFR may inhibit both EMT and PD-L1, which may potentiate the therapeutic effect of PD-L1-based immunotherapy, especially in the malignant subgroups of SACC patients with activated EGFR.

Immune checkpoint blockade therapies for HCC: current status and future implications

“…Chen et al [105] demonstrated that EMT positive human esophageal cancer tissues had higher PD-L1 expression compared to an EMT negative subgroup. Similar studies have shown an association between EMT and immune checkpoint expression in several cancers including thymic carcinoma [106] , melanoma [107] , adeno cystic carcinoma [108] , extrahepatic cholangiocarcinoma [109] and renal cell carcinoma [110] .…”

“…Another study in lung cancer demonstrated that p-Smad2 dependent TGF-β signalling is involved in PD-L1 overexpression [101] . Epidermal growth factor also induced EMT and PD-L1 expression in breast cancer and salivary adenoid cystic carcinoma cells [108,112] .…”

Convergent evolution of p38/MAPK activation in hormone resistant prostate cancer mediates pro-survival, immune evasive, and metastatic phenotypes

“…Furthermore, PD-L1 can indirectly activate p38 through DNA-PKcs, which promotes chemoresistance (Wu et al, 2018), and therefore suggests a common feed forward loop that may connect PD-L1 expression, DNA repair and pro-metastatic pathways (Goodwin et al, 2015), and convergent p38 activity. Interestingly, PD-L1 expression in the tumor and tumor microenvironment is also associated with poor outcomes and an aggressive and metastatic phenotype in many cancer subtypes (Kim et al, 2016; Wang et al, 2018).…”

TNF‑α‑mediated epithelial‑to‑mesenchymal transition regulates expression of immune checkpoint molecules in hepatocellular carcinoma

“…eMT status is closely associated with cancer metastasis, stemness, immune escape and drug resistance in HCC (17,18). It was previously identified that eMT is involved in the regulation of Pd-l1 in several cancer types, including breast cancer (19,20), lung cancer (17,21), pancreatic cancer (22), esophageal cancer (23) and salivary adenoid cystic carcinoma (24). The authors previously demonstrated that eMT is associated with Pd-l1 expression in patients with Hcc (8).…”