Miwako Tanaka

Mesenchymal stem cells enhance growth and metastasis of colon cancer

Recently, mesenchymal stem cells (MSCs) were reported to migrate to tumor stroma as well as injured tissue. We examined the role of human MSCs in tumor stroma using an orthotopic nude mice model of KM12SM colon cancer. In in vivo experiments, systemically injected MSCs migrated to the stroma of orthotopic colon tumors and metastatic liver tumors. Orthotopic transplantation of KM12SM cells mixed with MSCs resulted in greater tumor weight than did transplantation of KM12SM cells alone. The survival rate was significantly lower in the mixed‐cell group, and liver metastasis was seen only in this group. Moreover, tumors resulting from transplantation of mixed cells had a significantly higher proliferating cell nuclear antigen labeling index, significantly greater microvessel area and significantly lower apoptotic index. Splenic injection of KM12SM cells mixed with MSCs, in comparison to splenic injection of KM12SM cells alone, resulted in a significantly greater number of liver metastases. MSCs incorporated into the stroma of primary and metastatic tumors expressed α‐smooth muscle actin and platelet‐derived growth factor receptor‐β as carcinoma‐associated fibroblast (CAF) markers. In in vitro experiments, KM12SM cells recruited MSCs, and MSCs stimulated migration and invasion of tumor cells through the release of soluble factors. Collectively, MSCs migrate and differentiate into CAFs in tumor stroma, and they promote growth and metastasis of colon cancer by enhancing angiogenesis, migration and invasion and by inhibiting apoptosis of tumor cells.

Vascular endothelial growth factor C stimulates progression of human gastric cancer via both autocrine and paracrine mechanisms.

Purpose: Vascular endothelial growth factor (VEGF)-C induces lymphangiogenesis by activating the VEGF receptor (VEGFR)-3, which is expressed by lymphatic endothelial cells. VEGFR-3 has also been detected on several malignant cells, but the significance of VEGFR-3 expression on malignant cells remains unclear. In this study, we examined the expression and function of VEGFR-3 in gastric carcinoma cells. Experimental Design: We examined the expression of VEGFR-3 by four human gastric carcinoma cell lines and in 36 surgical specimens of gastric carcinoma. We also used cDNA microarrays to examine the effect of VEGF-C on gene expression in VEGFR-3-expressing KKLS cells. To stimulate VEGF-C/VEGFR-3 signaling in an autocrine manner, the VEGF-C expression vector was transfected into KKLS cells, and stable transfectants were established. These cells were then transplanted into the gastric walls of nude mice. Results: Two of the four gastric carcinoma cell lines expressed VEGFR-3 mRNA. In 17 of 36 gastric carcinoma specimens, VEGFR-3-specific immunoreactivity was detected on tumor cells. In vitro treatment of KKLS cells with VEGF-C stimulated cell proliferation and increased expression of mRNAs encoding cyclin D1, placental growth factor, and autocrine motility factor. Following inoculation of VEGF-C-transfected and control cells into the gastric walls of nude mice, tumor growth of the VEGF-C-transfected cells was greatly accelerated in comparison with that of control cells. Greater angiogenesis and lymphangiogenesis were also detected in VEGF-C-transfected tumors than in control tumors. Conclusions: Gastric carcinoma cells express VEGF-C and VEGFR-3. VEGF-C may play a role in the progressive growth of human gastric carcinoma through both autocrine and paracrine mechanisms.

Expression of platelet‐derived growth factor (PDGF)‐B and PDGF‐receptor β is associated with lymphatic metastasis in human gastric carcinoma

Recent study of murine fibrosarcoma has revealed that platelet‐derived growth factor (PDGF) plays a direct role in promoting lymphangiogenesis and metastatic spread to lymph nodes. Thus, we investigated the relation between PDGF and PDGF receptor (PDGF‐R) expression and lymphatic metastasis in human gastric carcinoma. We examined PDGF‐B and PDGF‐Rβ expression in four human gastric carcinoma cell lines (TMK‐1, MKN‐1, MKN‐45, and KKLS) and in 38 surgical specimens of gastric carcinoma. PDGF‐B and PDGF‐Rβ expression was examined by immunofluorescence in surgical specimens and in human gastric carcinoma cells (TMK‐1) implanted orthotopically in nude mice. Groups of mice (n = 10, each) received saline (control) or PDGF‐R tyrosine kinase inhibitor imatinib. PDGF‐B and PDGF‐Rβ mRNA expression was significantly higher in patients with lymph node metastasis than in those without and was also significantly higher in diffuse‐type carcinoma than in intestinal‐type carcinoma. In surgical specimens, tumor cells expressed PDGF‐B, but PDGF‐Rβ was expressed predominantly by stromal cells. Under culture conditions, expression of PDGF‐B mRNA was found in all of the gastric cell lines, albeit at different levels. In orthotopic TMK‐1 tumors, cancer cells expressed PDGF‐B but not PDGF‐Rβ. PDGF‐Rβ was expressed by stromal cells, including lymphatic endothelial cells. Four weeks of treatment with imatinib significantly decreased the area of lymphatic vessels. Our data indicate that secretion of PDGF‐B by gastric carcinoma cells and expression of PDGF‐Rβ by tumor‐associated stromal cells are associated with lymphatic metastasis. Blockade of PDGF‐R signaling pathways may inhibit lymph node metastasis of gastric carcinoma. (Cancer Sci 2010)

Stroma‐directed imatinib therapy impairs the tumor‐promoting effect of bone marrow‐derived mesenchymal stem cells in an orthotopic transplantation model of colon cancer

Bone marrow‐derived mesenchymal stem cells (MSCs) are reported to contribute to formation of tumor‐promoting stromal cells. We reported recently that, in an orthotopic nude mice model of colon cancer, MSCs traveled to tumor stroma, where they differentiated into carcinoma‐associated fibroblast (CAF)‐like cells. We also found that CAFs express platelet‐derived growth factor receptor (PDGFR) at a high level and that imatinib therapy targeting PDGFR in CAFs inhibits growth and metastasis of human colon cancer. These findings led us to examine whether the tumor‐promoting effect of MSCs is impaired by blockade of PDGFR signaling achieved with imatinib. Orthotopic transplantation and splenic injection of human MSCs along with KM12SM human colon cancer cells, in comparison with transplantation of KM12SM cells alone, resulted in significantly greater promotion of tumor growth and liver metastasis. The KM12SM + MSC xenograft enhanced cell proliferation and angiogenesis and inhibited tumor cell apoptosis. When tumor‐bearing animals were treated with imatinib, there was no significant increase in primary tumor volume or total volume of liver metastases, despite the KM12SM+MSC xenograft, and survival in the mixed‐cell group was prolonged by imatinib treatment. Moreover, the ability of MSCs to migrate to tumor stroma was impaired, and the number of MSCs surviving in the tumor microenvironment was significantly decreased. In in vitro experiments, treatment with imatinib inhibited migration of MSCs. Our data suggest that blockade of PDGF signaling pathways influences the interaction between bone marrow‐derived MSCs and tumor cells in the tumor microenvironment and, hence, inhibits the progressive growth of colon cancer.

Anti-stromal therapy with imatinib inhibits growth and metastasis of gastric carcinoma in an orthotopic nude mouse model.

Recent studies have revealed that platelet‐derived growth factor (PDGF) plays a role in promoting progressive tumor growth in several organs; however, whether PDGF plays such a role in gastric carcinoma is undetermined. We examined whether inhibition of PDGF receptor (PDGF‐R) tyrosine kinase signaling by imatinib affects tumor growth and metastasis in an orthotopic nude mouse model of human gastric carcinoma. TMK‐1 human gastric carcinoma cells were injected into the gastric wall of nude mice. Groups of mice (n = 10 each) received sterile water (control), low‐dose imatinib (50 mg/kg/day), high‐dose imatinib (200 mg/kg/day), cancer chemotherapeutic agent irinotecan (5 mg/kg/week), or imatinib (50 mg/kg/day or 200 mg/kg/day) and irinotecan (5 mg/kg/week) in combination for 28 days. Tumor growth and metastasis were assessed. Resected tumors were analyzed immunohistochemically. Carcinoma‐associated fibroblasts, pericytes and lymphatic endothelial cells in stroma expressed high levels of PDGF‐R; carcinoma cells did not. Treatment with imatinib alone did not inhibit tumor growth and metastasis; however, treatment with irinotecan alone or combined with imatinib significantly inhibited tumor growth. Only treatment with high‐dose imatinib and irinotecan in combination inhibited lymph node and peritoneal metastases. Immunohistochemically, only imatinib alone or in combination with irinotecan was shown to significantly decrease the stromal reaction, microvessel area and pericyte coverage of tumor microvessels. These effects were marked with high‐dose imatinib. In conclusion, administration of PDGF‐R tyrosine kinase inhibitor in combination with irinotecan appears to impair the progressive growth of gastric carcinoma by blockade of PDGF‐R signaling pathways in stromal cells.

Antibodies to Helicobacter pylori and CagA protein are associated with the response to antibacterial therapy in patients with H. pylori‐positive API2–MALT1‐negative gastric MALT lymphoma

The aim of this study was to clarify predictive factors for response to eradication therapy in cases of Helicobacter pylori (H. pylori)‐positive API2–MALT1‐negative gastric mucosa‐associated lymphoid tissue (MALT) lymphoma. Sixty‐six patients who were examined for H. pylori infection and the presence of the API2–MALT1 chimeric transcript and who underwent H. pylori eradication therapy as first‐line therapy, were enrolled in this study. Immunohistochemical markers (p53, Ki‐67, and BCL10), microsatellite instability, loss of heterozygosity, serum levels of antibodies (anti‐H. pylori and anti‐CagA), and markers for gastritis (gastrin and pepsinogens) were examined, and the results were compared between patients whose tumors regressed completely after eradication therapy (responders) and patients whose tumors did not regress (non‐responders). Of the 66 patients with localized gastric MALT lymphoma, 47 (71.2%) showed complete remission after eradication therapy. None of the H. pylori‐negative (n = 9) and/or API2–MALT1‐positive (n = 7) patients responded to antibacterial treatment. Of 44 patients with H. pylori‐positive API2–MALT1‐negative gastric MALT lymphoma, 38 (86.4%) showed complete remission after eradication therapy. Titers of antibodies against H. pylori and CagA protein were significantly higher in the responders than in the non‐responders (P = 0.0235 and 0.0089, respectively). No significant difference between the groups was observed for the other factors. In conclusion, measurement of titers of serum antibodies to H. pylori and CagA protein may be useful for predicting the response to eradication therapy in patients with H. pylori‐positive API2–MALT1‐negative gastric MALT lymphoma. (Cancer Sci 2009; 100: 1075–1081)

Potential role for vascular endothelial growth factor-D as an autocrine factor for human gastric carcinoma cells.

Vascular endothelial growth factor (VEGF)‐D induces lymphangiogenesis by activating VEGF receptor (VEGFR)‐3, which is expressed mainly by lymphatic endothelial cells. VEGFR‐3 has also been detected in several types of malignant cells, but the significance of VEGFR‐3 expression by malignant cells remains unclear. We examined the expression and function of VEGF‐D/VEGFR‐3 in human gastric carcinoma cells. Expression of VEGF‐D and VEGFR‐3 was analyzed in three human gastric carcinoma cell lines and 29 surgical specimens. cDNA microarray analysis was used to examine the effect of VEGF‐D on the expression of genes associated with disease progression in VEGFR‐3‐expressing KKLS cells. VEGF‐D‐transfected cells and control cells were transplanted into the gastric wall of nude mice. In 10 of the 29 (34%) gastric carcinoma specimens and two of the three cell lines, cancer cells expressed both VEGF‐D and VEGFR‐3. In vitro treatment of KKLS cells with exogenous VEGF‐D increased expression of cyclin D1 and Bcl‐2 and stimulated cell proliferation. VEGF‐D transfection into KKLS cells resulted in stimulation of angiogenesis, lymphangiogenesis, and cell proliferation, and in inhibition of apoptosis. VEGF‐D may participate in the progression of human gastric carcinoma by acting via autocrine and paracrine mechanisms. (Cancer Sci 2010)

A case of large cell neuroendocrine carcinoma of the stomach with multiple liver metastases.

A 79-year-old man was admitted to our hospital to determine the cause of his melena. He underwent esophagogastric endoscopy and computed tomography, revealing a submucosal tumor on the anterior wall of the gastric antrum with multiple liver metastases. Endoscopic biopsy revealed a large cell neuroendocrine cell carcinoma. A subtotal gastrostomy was performed to prevent pyloric stenosis and anemia caused by tumor hemorrhage. Previous studies on gastric neuroendocrine carcinoma reported poor prognosis. Large- and small-cell types of gastric neuroendocrine carcinomas were differentiated for the first time in the 14th edition of the Japanese Classification of Gastric Carcinoma. It is expected that the number of reports of gastric neuroendocrine carcinomas classified as either the large-cell or small-cell type will increase. It is necessary to collect information on more cases to improve prognosis and to establish appropriate treatment guidelines.

Abstract 519: Blockade of PDGFR signaling impairs the tumor promoting effect of bone marrow-derived mesenchymal stem cells in colon cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Bone marrow-derived mesenchymal stem cells (MSCs) are reported to migrate to tumor stroma as well as injured tissue. We reported recently that, in an orthotopic nude mice model of colon cancer, MSCs traveled to tumor stroma, where they differentiated into carcinoma-associated fibroblasts (CAF)-like cells. We have also found that CAFs express platelet-derived growth factor receptor (PDGFR) at a high level and that imatinib therapy targeting PDGFR in CAFs combined with administration of a cytotoxic drug significantly inhibits growth and metastasis of human colon cancer. These findings led us to examine whether the tumor promoting effect of MSCs is impaired by blockade of PDGFR signaling achieved with imatinib. KM12SM colon cancer cells alone or KM12SM cells mixed with MSCs in a 1:2 ratio were transplanted into the cecal wall of nude mice. Orthotopic transplantation of KM12SM cells mixed with MSCs, in comparison to transplantation of KM12SM cells alone, resulted in tumors of greater weight. The survival rate was significantly lower in the mixed-cell group. Co-injection of MSCs with tumor cells promotes tumor growth and metastasis of colon cancer by enhancing angiogenesis and tumor migration and invasion and by inhibiting tumor cell apoptosis. When tumor bearing animals were treated with imatinib (by gavage once daily at 50 mg/kg for 35 days), there was no significant increase in primary tumor volume or number of metastases with the KM12SM+MSC xenograft and the lower survival rate in the mixed-cell group was prolonged by the treatment. Moreover, migratory ability of MSCs to tumor stroma was impaired, and MSCs surviving in the tumor microenvironment were significantly decreased. In in vitro experiments, treatment with imatinib inhibited migration and proliferation of MSCs. Our data suggest that blockade of PDGFR signaling pathways influences the interaction between bone marrow-derived MSCs and tumor cells in the tumor microenvironment and, hence, inhibits the progressive growth of colon cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 519. doi:10.1158/1538-7445.AM2011-519

Abstract LB-296: Involvement of T-cell immunity in changes in the plasma amino acid profiles of patients with colorectal cancer

Metabolic changes in patients with various disorders, including liver disease and cancer, lead to alterations in amino acid balance, and plasma amino acid profiles can be used to discriminate between non-malnourished patients with cancer and healthy individuals. Not with standing, the mechanisms of amino acid imbalance are not well understood. In patients with cancer, various factors including metabolic changes in the tumor itself and immune responses may affect plasma amino acid levels. To investigate involvement of the immune system, we measured plasma amino acid levels in an orthotopic transplant model of colon cancer established in both conventional BALB/c mice and athymic BALB/c nude mice (T-lymphocyte-deficient mice). CT26 colon cancer cells (murine colon cancer cell line) were implanted into the cecal wall of the BALB/c mice (n=10) and nude mice (n=10). Plasma samples were collected from the tumor-bearing mice at 7 and 14 days after transplantation, and changes in plasma amino acid profiles were compared. Plasma was also collected from mice that underwent sham operation (control mice, n=10). Plasma amino acid concentrations were measured by LC/MS/MS. The plasma concentrations of several amino acids changed significantly in tumor-bearing mice compared to concentrations in control mice. Although cells from the same line were injected into the cecal wall of BALB/c mice and nude mice, a difference was noted in the change in plasma amino acid levels. Plasma Val, Ile, Leu, and Met levels decreased in BALB/c mice but increased in nude mice. There was no difference in the amino acid profile of CT26 tumor tissues between BALB/c mice and nude mice. We then injected antiCD3-antibody into the peritoneal cavity of tumor-bearing BALB/c mice (n=5) to eliminate T-cell function. We also injected IgG into tumor-bearing BALB/c mice (n=5) for control. The pattern of change in amino-acid profiles differed between the two groups of mice. Our findings suggest that T-lymphocyte-mediated immunoreactions are involved in changes in the plasma amino acid profile in patients with colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-296. doi:10.1158/1538-7445.AM2011-LB-296