Knockdown of serine/threonine-protein kinase 24 promotes tumorigenesis and myeloid-derived suppressor cell expansion in an orthotopic immunocompetent gastric cancer animal model

Abstract

A higher incidence of gastric cancer has been found in East Asia compared to the incidence in other regions. Gastric cancer patients have a poor prognosis due to distant metastasis and advanced cancer stages. Tumor escape pathways include the expansion of the immunosuppressive myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment. We have successfully established an orthotopic immunocompetent gastric cancer model in C57BL/6 mice. The cell line is named M12 and was deposited at the Bioresource Collection and Research Center of Taiwan on Sep. 13, 2016 (Patent No. I604054). The orthotopic animal model of gastric cancer has similar biological characteristics as human gastric cancer. Serine/threonine-protein kinase 24 (STK24) is a member of the germinal center kinase (GCK)-III family. GCKs participate in cancer and immunological disorders. The effects of STK24 in gastric cancer are less well understood. CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 technology was used to induce a STK24 genetic knockout at the genomic DNA level in tumor cells. The knockdown of the STK24 gene increased the tumor growth in an orthotopic model of gastric cancer. The STK24 gene silencing in tumors induced the expansion of CD11b+Ly6C+ cells and F4/80+ macrophages in vivo. To our knowledge, we have developed the first orthotopic transplantable model of gastric cancer in syngeneic inbred mice. Our results further indicate that STK24 is important for immune regulation during the tumorigenesis of gastric cancer.

Serine/threonine-protein kinase 24 is an inhibitor of gastric cancer metastasis

“…1c). In a previous study, the knockout of STK24 expression did not affect the cell growth rates of mouse M12 cancer cells [2]. Therefore, the suppression of STK24 did not affect the cell growth rates of gastric cancer.…”

“…Single guide RNAs (sgRNAs) targeting mouse Stk24 and human STK24 were purchased from the National RNAi Core Facility (Academia Sinica, Taiwan; http://rnai.genmed.sinica.edu.tw). The DNA sequences for generating mouse sgRNA were prepared as previously described [2]. The DNA sequences of human sgSTK24-RNA1 and sgSTK24-RNA2 were as follows: sgSTK24-RNA1 forward: 5′-CAC CGC GCC AAA GTC CGC CAG CTT C-3′; sgSTK24-RNA1 reverse: 5′-AAA CGA AGC TGG CGG ACT TTG GCG C-3′; sgSTK24-RNA2 forward: 5′-CAC CGT AGT TTC CTT CCA ACG TCG G-3′; and sgSTK24-RNA2 reverse: 5′-AAA CCC GAC GTT GGA AGG AAA CTA C-3′.…”

“…Serine/threonine-protein kinase 24 (STK24) belongs to the germinal center kinase III (GCKIII) subfamily and is expressed in normal and gastric cancer tissues [1,2]. In a previous study, the STK24 protein was found in normal tissues at signi cantly greater levels than in gastric cancer samples and, according to bioinformatics analyses of Kaplan-Meier Plotter and Oncomine data, the STK24 gene was associated with the poor prognosis of gastric cancer patients; importantly, STK24 knockdown was shown to promote the tumorigenicity of gastric cancer [2]. In a cell-based study, suppression of endogenous STK24 by small interference RNA was found to enhance cellular migration in MCF-7 breast cancer cells, whereas overexpression of STK24 inhibited the migration of these cells [3].…”

“…Both M-MDSCs and PMN-MDSCs are associated with the development of metastases and poor survival in melanoma cases [10]. Moreover, in an orthotopic immunocompetent gastric cancer model, STK24 silencing in tumors induces an expansion of CD11b + Ly6C + cells and F4/80 + macrophages cells [2].…”

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection induces dysregulation of immunity: in silico gene expression analysis

“…1.0.12 of R software 19 - 23 . Signals were processed and normalized as we previously described 24 - 32 . The Database for Annotation, Visualization, and Integrated Discovery (DAVID, vers.…”