Upregulation of lncRNA ADAMTS9-AS2 Promotes Salivary Adenoid Cystic Carcinoma Metastasis via PI3K/Akt and MEK/Erk Signaling.

Neurotropic infiltrative growth and distant metastasis are the main causes of death in salivary adenoid cystic carcinoma (SACC) patients. Long noncoding RNAs (lncRNAs) are involved in many human neoplasms, however, their potential roles in SACC are unclear. In our study, we found that ADAM metallopeptidase with thrombospondin type 1 motif, 9 (ADAMTS9) antisense RNA 2 (ADAMTS9-AS2) was significantly upregulated in SACC patients with metastasis and SACC-lung metastasis (LM) cells. Moreover, ADAMTS9-AS2 expression was closely associated with the prognosis and distant metastasis in SACC patients. Next, we found that c-myc could specifically bind to the promoter of ADAMTS9-AS2 and activated its transcription. Knockdown of ADAMTS9-AS2 significantly inhibited migration and invasion of SACC cells in vitro and distant lung metastasis in vivo. Furthermore, ADAMTS9-AS2, which mainly expressed in the cytoplasm, shared microRNA (miRNA) response elements with Integrin α6 (ITGA6). Overexpression of ADAMTS9-AS2 competitively bound to miR-143-3p that inhibited ITGA6 from miRNA-mediated degradation, and thus it activated the activity of PI3K/Akt and MEK/Erk signaling and facilitated SACC metastasis. In summary, ADAMTS9-AS2 promotes migration and invasion in SACC by competing with miR-143-3p. This sheds a new insight into the regulation mechanism of ADAMTS9-AS2, and it provides a possible application for the SACC treatment.

Xie S ，Yu X ，Li Y ，Ma H ，Fan S ，Chen W ，Pan G ，Wang W ，Zhang H ，Li J ，Lin Z ... -  《-》

EGF/EGFR Promotes Salivary Adenoid Cystic Carcinoma Cell Malignant Neural Invasion via Activation of PI3K/AKT and MEK/ERK Signaling.

Salivary adenoid cystic carcinoma (SACC) is one of the most common malignant cancers of the salivary gland, and 32.4-72.0% of SACC cases exhibit neural invasion (NI); however, the molecular mechanism underlying the high invasion potential of SACC remains unclear. The present study investigated the role of epidermal growth factor receptor (EGFR) in the AKT inhibition- or mitogen-activated protein kinase kinase (MEK)-induced NI and epithelialmesenchymal transition (EMT) in SACC cells using EGFR, PI3K, and MEK inhibitors. SACC-83 cell viability was assessed using an MTT assay, and a wound healing assay was performed to evaluate cell migration. Immunohistochemical staining with streptavidin peroxidase was used to detect the positive expression rate of EMT, AKT, phosphorylated (p)-AKT, ERK, and p-ERK proteins. The impact of EGFR, PI3K, and MEK inhibitors on tumor growth and NI was examined in a xenograft model in nude mice. EGF and EGFR are effective in increasing cell viability, migration, and invasion. SACC metastasis is affected by the PI3K/AKT and MEK/ERK pathways, both of which are initiated by EGF/EGFR. The EMT and NI are regulated by the EGF/EGFR, PI3K/AKT, and MEK/ERK pathways. The present findings demonstrate the importance of suppressed EGFR/AKT/MEK signaling in NI in SACC by neural-tumor co-culture in vitro. Furthermore, our preclinical experiment provides solid evidence that injection of EGFR, PI3K, and MEK inhibitors suppressed the tumor growth and NI of SACC cells in nude mice. It was identified that inhibitors of EGFR, PI3K/AKT or MEK/ERK suppressed the proliferation, migration, and NI of SACC-83 cells via downregulation of the PI3K/AKT or MEK/ERK pathways. It was also demonstrated that inhibition of EGFR abolishes EMT in SACC by inhibiting the signaling of PI3K/AKT and MEK/ERK. The present results suggest the potential effectiveness of targeting multiple oncogenes associated with downstream pathways of EGF/EGFR, as well as potential therapeutic targets to limit NI in SACC by PI3K/AKT or MEK/ERK inhibition.

Ren Y ，Hong Y ，He W ，Liu Y ，Chen W ，Wen S ，Sun M ... -  《-》

MiR-200b-5p inhibits tumor progression in salivary adenoid cystic carcinoma via targeting BTBD1.

Salivary adenoid cystic carcinoma (SACC) is a rare malignant tumor of the salivary gland. Studies have suggested that miRNA may play a crucial role in the invasion and metastasis of SACC. This study aimed to investigate the role of miR-200b-5p in SACC progression. Reverse transcription-quantitative PCR and western blot assay were used to detect the expression levels of miR-200b-5p and BTBD1. The biological functions of miR-200b-5p were evaluated via wound-healing assays, transwell assays, and xenograft nude mice model. The interaction between miR-200b-5p and BTBD1 was assessed using luciferase assay. Results showed that miR-200b-5p was downregulated in the SACC tissues while BTBD1 was upregulated. miR-200b-5p overexpression suppressed SACC cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT). Bioinformatics prediction and luciferase reporter assay revealed that miR-200b-5p could directly bind to BTBD1. Besides, miR-200b-5p overexpression could rescue the tumor-promoting effect of BTBD1. miR-200b-5p inhibited tumor progression by modulating EMT-related proteins, targeting BTBD1 and inhibiting PI3K/AKT signaling pathway. Overall, our findings indicate that miR-200b-5p can suppress SACC proliferation, migration, invasion, and EMT by regulating BTBD1 and PI3K/AKT axis, providing a promising therapeutic target for SACC treatment.

Tang Y ，Zhu Q ，Yang L ，Meng Y ，Zhang G ，Zhou T ，Wang C ，Song X ，Su YX ，Ye J ... -  《-》

MicroRNA-181a suppresses salivary adenoid cystic carcinoma metastasis by targeting MAPK-Snai2 pathway.

To date microRNAs and their contribution to the onset and propagation of salivary adenoid cystic carcinoma (SACC) are limited. The objective of this study was to identify miR-181a and its mechanism in the metastasis of SACC. At first microarray and quantitative RT-PCR were used to investigate microRNA profiles and miR-181a in paired SACC cell lines with different metastatic potential. Then the effect of miR-181a on metastatic potential of SACC was investigated. MiR-181a target genes and Snai2 promoter activity were investigated using luciferase reporter gene assays. Western blot was used to detect MAPK-Snai2 pathway-related protein level. A panel of deregulated microRNAs (including miR-181a) was identified in paired of SACC cell lines. Functional analysis indicated that miR-181a inhibited SACC cell migration, invasion and proliferation in vitro, and it suppressed tumor growth and lung metastasis in vivo. Direct targeting of miR-181a to MAP2K1, MAPK1 and Snai2 was confirmed by luciferase reporter gene assays. MiR-181a mimic inhibited the expression of MAP2K1, MAPK1 and Snai2 in SACC cells. MAP2K1 or MAPK1 siRNA suppressed Snai2 gene promoter activity and reduced Snai2 expression and the metastatic potential of SACC cells. Our results indicate that miR-181a plays an important role in the metastasis of SACC, and may serve as a novel therapeutic target for SACC. MiR-181a regulates the MAPK-Snai2 pathway both through direct cis-regulatory mechanism and through indirect trans-regulatory mechanism. To our knowledge, this is the first study revealing that miR-181a deregulation mediated the metastasis of SACC by regulating MAPK-Snai2 pathway.

He Q ，Zhou X ，Li S ，Jin Y ，Chen Z ，Chen D ，Cai Y ，Liu Z ，Zhao T ，Wang A ... -  《-》

Thioredoxin 1 mediates TGF-β-induced epithelial-mesenchymal transition in salivary adenoid cystic carcinoma.

Jiang Y ，Feng X ，Zheng L ，Li SL ，Ge XY ，Zhang JG ... -  《Oncotarget》