Synaptotagmin 11 scaffolds MKK7–JNK signaling process to promote stem-like molecular subtype gastric cancer oncogenesis

Abstract

Background Identifying biomarkers related to the diagnosis and treatment of gastric cancer (GC) has not made significant progress due to the heterogeneity of tumors. Genes involved in histological classification and genetic correlation studies are essential to develop an appropriate treatment for GC. Methods In vitro and in vivo lentiviral shRNA library screening was performed. The expression of Synaptotagmin (SYT11) in the tumor tissues of patients with GC was confirmed by performing Immunohistochemistry, and the correlation between the expression level and the patient’s survival rate was analyzed. Phospho-kinase array was performed to detect Jun N-terminal kinase (JNK) phosphorylation. SYT11, JNK, and MKK7 complex formation was confirmed by western blot and immunoprecipitation assays. We studied the effects of SYT11 on GC proliferation and metastasis, real-time cell image analysis, adhesion assay, invasion assay, spheroid formation, mouse xenograft assay, and liver metastasis. Results SYT11 is highly expressed in the stem-like molecular subtype of GC in transcriptome analysis of 527 patients with GC. Moreover, SYT11 is a potential prognostic biomarker for histologically classified diffuse-type GC. SYT11 functions as a scaffold protein, binding both MKK7 and JNK1 signaling molecules that play a role in JNK1 phosphorylation. In turn, JNK activation leads to a signaling cascade resulting in cJun activation and expression of downstream genes angiopoietin-like 2 (ANGPTL2), thrombospondin 4 (THBS4), Vimentin, and junctional adhesion molecule 3 (JAM3), which play a role in epithelial-mesenchymal transition (EMT). SNU484 cells infected with SYT11 shRNA (shSYT11) exhibited reduced spheroid formation, mouse tumor formation, and liver metastasis, suggesting a pro-oncogenic role of SYT11. Furthermore, SYT11-antisense oligonucleotide (ASO) displayed antitumor activity in our mouse xenograft model and was conferred an anti-proliferative effect in SNU484 and MKN1 cells. Conclusion SYT11 could be a potential therapeutic target as well as a prognostic biomarker in patients with diffuse-type GC, and SYT11-ASO could be used in therapeutic agent development for stem-like molecular subtype diffuse GC.

Non-kinase targeting of oncogenic c-Jun N-terminal kinase (JNK) signaling: the future of clinically viable cancer treatments

“…However, as each of these kinases is likely to regulate multiple downstream effectors and biological responses, it remains to be seen how they fare in terms of cellular toxicity. For instance, whilst MKK7 has been shown to promote the stemness of gastric cancers [77] and drive the metastasis of colon cancer cells [78], it also functions as a critical tumor suppressor in lung and mammary cancers through the stabilization of p53 [79]. Much like JNKs, the roles of MAP2Ks and MAP3Ks in tumorigenesis are highly context specific and a better understanding of their involvement in JNK signaling is required for the development of effective treatment strategies.…”

“…Whilst a number of JNK scaffolds have been identified, including JIP family members [82], arrestins [83,84], filamins [85,86] and WDR62 [87,88] (Figure 3), their JNK-related roles have almost exclusively been linked to stress-induced apoptosis and limited literature is available covering their relevance as scaffolds in cancer progression. To this end, SH3 domain containing ring finger 3 (SH3RF3, also POSH2) and Synaptotagmin 11 (SYT11) have both recently been identified as JNK scaffolds that positively regulate cancer stem cells (CSCs) in breast and gastric cancers [14,77]. CSCs are a tumor cell subpopulation that are capable of self-renewal, display tumor-initiating capabilities and are associated with metastasis, therapy resistance and disease recurrence.…”

“…With protein-protein interactions partly described for both the SH3RF3 and SYT11 JNK signaling complexes, it is clear that whilst these two scaffolds drive similar biological outcomes, they each regulate JNK through distinct mechanisms [14,77] (Figure 3). In the context of gastric cancer, Kim et al demonstrated that both MKK7 and JNK interact with the SYT11 in the cytoplasm via its N-terminal transmembrane domain.…”

“…In the context of gastric cancer, Kim et al demonstrated that both MKK7 and JNK interact with the SYT11 in the cytoplasm via its N-terminal transmembrane domain. SYT11-dependent JNK phosphorylation in turn activates c-Jun and the subsequent transcription of EMT-related genes that drive tumor formation and liver metastasis [77]. Alternately, Zhang et al reported that whist MKK7 directly binds the fourth SH3 domain of SH3RF3, JIP1 is required to mediate the interaction between SH3RF3 and JNK.…”

Identification of GNG7 as a novel biomarker and potential therapeutic target for gastric cancer via bioinformatic analysis and in vitro experiments

“…The diagnostic abilities of traditional tumor markers such as CEA, CA 125, CA19-9 and CA 72-4 for GC are largely limited owing to their inadequate sensitivity or specificity [ 34 , 35 ]. Furthermore, there is still a lack of ideal biological indicators to predict the progression and prognosis of GC and to be used as effective therapeutic targets in clinical practice [ 36 ]. Thus, the identification of novel biomarkers that play essential roles in the progression of GC, indicate treatment response, and act as targets for improving the prognosis of patients with GC is desperately needed.…”