Jang Seong Kim

Targeting the EGFR, VEGFR, and PDGFR on colon cancer cells and stromal cells is required for therapy

Immunohistochemical analysis of human colon cancers growing in the cecal walls of nude mice revealed that epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor 2 (VEGFR2) were expressed by different tumor cells and tumor-associated endothelial cells, whereas platelet-derived growth factor receptor (PDGFR)β was expressed by tumor-associated endothelial cells and pericytes. We hypothesized that treatment of nude mice with AEE788 (an inhibitor of EGFR and VEGFR phosphorylation) and STI571 (an inhibitor of PDGFRβ phosphorylation) combined with irinotecan would overcome the intratumoral heterogeneity of these growth factors and efficiently inhibit colon cancer growth and metastasis. We implanted HT29 and KM12SM cells into the cecal walls of nude mice. Two weeks later, the mice were treated with oral vehicle solution; oral AEE788, oral STI571, or intraperitoneal injection of irinotecan as single agents; or the various combinations of these agents. We then assessed the mice for tumor growth and metastasis. Immunohistochemical analyses revealed that oral AEE788 suppressed proliferation and increased apoptosis of tumor cells and tumor-associated endothelial cells. Oral STI571 increased apoptosis of tumor-associated endothelial cells and pericytes. The combination of AEE788, STI571, and irinotecan produced the greatest inhibition of primary tumor growth and metastasis. Collectively, these data demonstrate that only targeting multiple tyrosine kinase receptors on colon cancer cells and tumor-associated stromal cells can overcome the effects of biologic heterogeneity for resistance to treatment and has the potential to improve therapeutic outcome for patients with this disease.

Consistent interactions between tumor cell IL-6 and macrophage TNF-α enhance the growth of human prostate cancer cells in the bone of nude mouse

To test the hypothesis that tumor-associated macrophages (TAMs) enhance the growth and metastasis of human prostate cancer in the bone, we evaluated the effects of decreasing interleukin-6 (IL-6) production by tumor cells and TAMs in a mouse model of bone metastasis. Human PC-3MM2 cells that produce IL-6 were transfected with lentivirus containing IL-6 small hairpin RNA (shRNA) or nonspecific RNA and injected into the tibias of nude mice treated intraperitoneally every 5days for 5weeks with phosphate-buffered saline (PBS), liposomes containing PBS, or liposomes containing clodronate (to decrease the number of macrophages). Transfection of PC-3MM2 cells with IL-6 shRNA significantly decreased cellular expression of IL-6 and the number of TAMs and osteoclasts in bone tumors, which correlated with significant decreases in tumor size, bone lysis, and incidence of lymph node metastasis. Treatment of mice with clodronate liposomes significantly decreased the number of TAMs and osteoclasts in the bone tumors, the expression of IL-6 in the PC3-MM2 cells, and the production of tumor necrosis factor (TNF)-α by TAMs. These findings correlated with a significant decrease in tumor size, bone lysis, and lymph node metastasis. Knocking down IL-6 in tumor cells and decreasing TAMs was associated with the lowest incidences of bone tumors and lymph node metastasis. These results suggest that TAMs enhance the growth of prostate cancer cells in the bone.

Abstract 601: Macitentan (ACT-064992), a tissue-targeting endothelin receptor antagonist enhances therapeutic efficacy of paclitaxel by modulating survival pathways in orthotopic models of metastatic human ovarian cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Introduction: In 2009, ovarian cancer was the leading cause of death from gynecologic cancer in the United States. Efforts to develop tools for early detection and therapeutic regimens to overcome drug resistance of the ovarian cancer have not made a significant achievement to prolong the median survial of the patients. Potential treatments for ovarian cancers that have become resistant to standard chemotherapies include modulators of tumor cell survival, such as endothelin receptor (ETR) antagonist. We investigated the therapeutic efficacy of the dual ETR antagonist, macitentan, on human ovarian cancer cells, SKOV3ip1 and IGROV1, growing orthotopically in nude mice. Materials and Methods: Mice were injected with one million cells of SKOV3ip1 or IGROV1. Ten days later, mice with established disease were randomized into vehicle (control), paclitaxel (weekly, intraperitoneal injections), macitentan (daily oral administrations) or a combination of paclitaxel and macitentan treatment groups. After 4 weeks of treatment, mice were necropsied and tumor incidence, tumor weight, and incidence of ascites were recorded. Tumor tissues were processed for immunohistochemical analyses. Results: Treatment with paclitaxel decreased tumor weight and volume of ascites. Combination therapy with macitentan and paclitaxel reduced tumor incidence and further reduced tumor weight and volume of ascites when compared with paclitaxel alone. Macitentan alone occasionally reduced tumor weight but alone had no effect on tumor incidence or ascites. Immunohistochemical analyses revealed that treatment with macitentan and macitentan plus paclitaxel inhibited the phosphorylation of ETRs and suppressed the survival pathways of tumor cells by decreasing the levels of pVEGFR2, pAkt, and pMAPK. The dose of macitentan necessary for inhibition of phosphorylation correlated with the dose required to increase antitumor efficacy of paclitaxel. Conclusion: Treatment with macitentan enhanced the cytotoxicity mediated by paclitaxel as measured by the degree of apoptosis in tumor cells and tumor-associated endothelial cells. Collectively, these results show that administration of macitentan in combination with paclitaxel prevents the progression of ovarian cancer in the peritoneal cavity of nude mice in part by inhibiting survival pathways of both tumor cells and tumor-associated endothelial cells. 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 601. doi:10.1158/1538-7445.AM2011-601