ABCB1 Regulates Immune Genes in Breast Cancer.

Background: Resistance to standard chemotherapy is a critical problem for breast cancer patients. The ATP-binding cassette (ABC) superfamily transporters actively pump out drugs and play an important role in chemoresistance. ABCB1 (ABC subfamily B, member 1, also named as multidrug resistance protein 1, MDR1) and suppressive myeloid-derived suppressor cells (MDSCs) potentially involve in chemoresistance of breast cancer. The relationship between ABCB1 and immune genes in breast cancer has not been widely studied. Methods: Microarray and RNA sequencing data were obtained from The Cancer Genome Atlas Breast Invasive Carcinoma in Genomic Data Commons Data Portal and Gene Expression Omnibus database. A patient-derived xenograft (PDX) model of HER2+ breast cancer was established to investigate the association between ABCB1 and immune genes in breast cancer. Results: Expression of ABCB1 increased in doxorubicin-selected MCF-7/ADR cells. High expression of ABCB1 mRNA is correlated with lymph-node metastasis and worse overall survival in patients with breast cancer. ABCB1 is positively correlated with IL6, CSF1, CSF3, and PTGS2. In the HER2+ stage IIA breast cancer PDX model, both doxorubicin and paclitaxel suppressed growth of P2 tumors. IL6, CSF1, CSF3, and PTGS2 expression were suppressed by paclitaxel but not doxorubicin. Intrasplenic MDSCs, including CD11b+Ly6G+ and CD11b+Ly6C+ cells, were more abundant than intratumor MDSCs in PDX-carrying nude mice. Clinically, the patient developed cancer recurrence after adjuvant chemotherapy with doxorubicin-based regimen and was well controlled after paclitaxel-trastuzumab combined therapy. Conclusion: ABCB1 was a poor predictor of HER2+ LN- breast cancer. Regulation of immune genes by ABCB1 contributed to cancer recurrence and treatment effect. The PDX model was suitable for investigation the expression of target genes and expansion of immune cells.

Serine/threonine-protein kinase 24 is an inhibitor of gastric cancer metastasis through suppressing CDH1 gene and enhancing stemness.

Gastric cancer patients often present with distant metastasis and advanced stages. Suppressing serine/threonine-protein kinase 24 (STK24, also known as MST3) is known to promote gastric tumorigenesis. Here, we investigated the effects from STK24 on the metastasis of gastric cancer. We used CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 technology for genetic knockout of STK24 at the genomic DNA level in human MKN45 and mouse M12 gastric cancer cells. To assess the consequences of STK24 knockdown, western blot, cell migration, and wound healing assays were conducted in vitro. An in vivo mouse model of liver metastasis was established and tested, and bioinformatics analyses were performed. The knockdown of the STK24 gene enhanced cell migration and increased liver metastasis in the mouse model of gastric cancer. STK24-silenced tumors suppressed CD4+ T cells and enhanced the expansion of CD11b+Ly6C+ myeloid-derived suppressor cells (MDSCs) and F4/80+ macrophages in the spleen of the mice. In MKN45 cells, STK24 silencing resulted in downregulation of E-cadherin (gene CDH1, Cadherin-1, or epithelial cadherin). In 38 paired specimens of gastric adenocarcinomas and normal tissues, we examined STK24 and CDH1 expression levels via western blot; a positive correlation between the expression levels of STK24 and CDH1 was found (R2 = 0.5507, P = 9.72 × 10-8). Furthermore, in Oncomine database and Kaplan-Meier plotter analysis, the loss of CDH1, increase in CCL2, and upregulation of CD44 were correlated with poor prognosis of gastric cancer patients. Our results demonstrate that knockdown of STK24 increases cell migration through suppressing CDH1 and enhancing CD44. In experimental model of metastatic gastric cancer in syngeneic inbred mice, STK24 is important for immune suppression through expansion of CD11b+Ly6C+ MDSCs and F4/80+ macrophages. We confirmed that STK24 is an inhibitor of gastric cancer metastasis.

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

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.

Mucin 2 silencing promotes colon cancer metastasis through interleukin-6 signaling.

Downregulation of Mucin 2 (MUC2) expression is associated with early carcinogenesis events in colon cancer. MUC2 plays a role in the progression of colon cancer, and reduced MUC2 protein expression correlates with increased interleukin-6 (IL-6) expression. However, the interaction between MUC2 and IL-6 in colorectal cancer metastasis remains unclear. We systematically analyzed MUC2 and IL-6 expression and determined the survival of cancer patients with high or low MUC2 and IL-6 expression using the Oncomine and PrognoScan databases, respectively. This analysis identified downregulation of MUC2 and overexpression of IL-6 in colon cancer but not in normal colon tissue, and this expression pattern was correlated with poor survival of colon cancer patients. We examined the effects of MUC2 on colon cancer metastasis and used vector-mediated application of short hairpin RNA (shRNA) to suppress MUC2 expression. MUC2 suppressed the migration of colon cancer cells in vitro and dramatically diminished liver metastases in vivo. Treatment with IL-6 increased signal transducer and activator of transcription 3 (STAT3) phosphorylation, promoted checkpoint kinase 2 (Chk2) activation, attenuated cAMP response element-binding protein (CREB) phosphorylation, and suppressed E-cadherin protein expression in MUC2-silenced HT-29 cancer cells. Most importantly, MUC2 is a potential prognostic indicator for colon cancer.

Argininosuccinate synthetase 1 suppression and arginine restriction inhibit cell migration in gastric cancer cell lines.

Gastric cancer metastasis remains a major cause of cancer-related deaths. There is an urgent need to develop new therapeutic approaches targeting metastatic gastric cancer. Argininosuccinate synthetase 1 (ASS1) expression is increased in gastric cancer. We detected the protein expression of ASS1 in human gastric cancer cell lines (AGS, NCI-N87, and MKN45) and in murine gastric cancer cell lines (3I and 3IB2). We used vector-mediated short hairpin RNA (shRNA) expression to silence ASS1 expression in the MKN45 and 3IB2 cell lines, and analyzed the effects of this protein on cell migration and metastasis. We demonstrated that ASS1 silencing suppressed cell migration in the MKN45 and 3IB2 cell lines. ASS1 knockdown significantly reduced liver metastasis in mice after the intrasplenic implantation of 3IB2 cancer cell clones. To determine whether arginine restriction may represent a therapeutic approach to treat gastric cancer, the sensitivity of tumor cells to arginine depletion was determined in gastric cancer cells. Arginine depletion significantly inhibited cell migration in the gastric cancer cell line. The silencing of ASS1 expression in MKN45 and 3IB2 gastric cancer cells markedly decreased STAT3 protein expression. In conclusion, our results indicate that the ASS1 protein is required for cell migration in gastric cancer cell lines.

Suppression of mucin 2 promotes interleukin-6 secretion and tumor growth in an orthotopic immune-competent colon cancer animal model.

Mucin 2 (MUC2) is the major secreted mucin of the large intestine and is expressed by adenomas and mucinous carcinomas. Since colon cancer is associated with a proinflammatory microenvironment and dysregulated MUC2 expression, the aim of this study was to characterize the effects of MUC2 gene expression in colon tumor progression using colonic cancer cells. CT26 colon cancer cells were stably transfected with MUC2 siRNA (MUC2 RNAi) or a control construct containing a nonspecific sequence (scrambled RNAi). Expression of MUC2 was significantly decreased in the MUC2 RNAi cell clones. Although MUC2 suppression did not affect the cell growth of colon cancer cells in vitro, MUC2 knockdown promoted tumor growth in an orthotopic colon cancer model in vivo. MUC2 silencing also increased interleukin (IL)-6 secretion by colon cancer cells. IL-6 neutralization attenuated tumor formation by MUC2 RNAi cells; it also increased CD8 T cell infiltration into the peritoneum. Taken together, to the best of our knowledge, this is the first study indicating that the immune response to cancer cells plays an important role in tumor growth regulated by MUC2. Furthermore, given the effects of MUC2 on IL-6 secretion, its targeting may represent a potentially useful strategy to treat colonic carcinomas.

Establishment of an orthotopic transplantable gastric cancer animal model for studying the immunological effects of new cancer therapeutic modules.

Tumor cell growth is influenced by the cellular microenvironment including the presence of immune cells and blood vessels. Currently, no transplantable gastric cancer syngeneic animal models exist; therefore, we set out to establish a mouse gastric carcinoma cell line, which was named mouse gastric carcinoma cell line 3I (MGCC3I), from forestomach carcinoma developed in benzo[a]pyrene-treated ICR mice. MGCC3I cells showed epithelial-like morphology, multinuclear giant cell formation, and retained an intestinal phenotype, which are similar to human gastric cancer carcinoma cells. The expression of gastric cancer markers MUC1, MUC2, and MUC5AC, and oncogenes c-myc, c-met, cyclin E1, and cancer stem cell marker CD44 was determined in MGCC3I cells. MGCC3I cells formed poorly differentiated stomach tumors following orthotopic implantation into the stomachs of syngeneic ICR mice. Histone deacetylase inhibitors are recognized as a new class of anticancer drugs. The immunological therapeutic effects of the histone deacetylase inhibitors sodium butyrate and valproic acid were evaluated in this new animal tumor model. Sodium butyrate inhibited MGCC3I stomach tumor formation in animal models. Increased tumor infiltration by CD8 T cells and neutrophils was observed in mice treated with sodium butyrate or valproic acid. Depletion of CD8 T cells significantly attenuated tumor regression mediated by histone deacetylase inhibitors, which is correlated with enhancement of the MHC class I pathway in MGCC3I cells. Taken together, we have successfully established an orthotopic transplantable gastric tumor animal model and demonstrated its usefulness in revealing the role of CD8 T cells in the therapeutic effects of sodium butyrate.

Depletion of CD4(+)CD25(+) regulatory T cells can promote local immunity to suppress tumor growth in benzo[a]pyrene-induced forestomach carcinoma.

AIM: To elucidate the distribution of CD4(+)CD25(+) regulatory T cells (Tregs) in different lymphoid tissues and its local enhancement on tumor growth before and after depletion of CD4(+)CD25(+) Tregs. METHODS: Female ICR mice were gavaged with benzo[a]pyrene (BaP) to induce forestomach carcinoma. CD4(+)CD25(+) Tregs were intraperitoneally depleted with monoclonal antibody PC61. These mice were divided into BaP-only, BaP + IgG, BaP + PC61, and control groups. The forestomach of mice was dissected for histological analysis, and tunnel test was performed for apoptosis of tumor cells. CD4(+)CD25(+) Tregs were sorted from different lymphoid tissues and expression of Foxp3, IL-10, and chemokine receptors was analyzed by flow cytometry, semi-quantitative and real-time polymerase chain reaction. RESULTS: The mice gavaged with only BaP showed increased forestomach papilloma and carcinoma at wk 16 and 32. The proportion of CD4(+)CD25(+) Tregs was significantly higher in peri-stomach regional lymph nodes than in other lymphoid tissues. These CD4(+)CD25(+) Tregs in regional lymph nodes expressed higher levels of Foxp3 and IL-10, enriched in the CD62L-subset, and CCR1 and CCR5 chemokine receptors. In mice gavaged with BaP + PC61, the number of tumor nodules and tumor volume decreased significantly with massive infiltrating cells and apoptosis of tumor cells. In the draining regional lymph nodes, the number of CD4(+)CD25(+) Tregs also decreased significantly. CONCLUSION: Inducible and activated CD4(+)CD25(+) Tregs in the draining regional lymph nodes suppress host local immunity during tumor growth. Depletion of CD4(+)CD25(+) Tregs can promote host local immunity to suppress tumor growth.