No abstract

Metronomic chemotherapy is the frequent administration of low doses of chemotherapeutic agents targeting tumor-associated endothelial cells. We examined the efficacy of metronomic irinotecan combined with low-intensity ultrasound (US) in human uterine sarcoma and evaluated its antiangiogenesis mechanism by measuring the circulating endothelial progenitor cells (CEP), a surrogate marker of angiogenesis. A human uterine sarcoma cell line, FU-MMT-3, was used in the present study because this tumor is one of the most malignant neoplasms of human solid tumors and it also has a high angiogenesis property. The combination of lowdose irinotecan and US irradiation significantly inhibited the tube formation of HUVEC and vascular endothelial growth factor expression of tumor cells in vitro. The FU-MMT-3 xenografts in nude mice were treated using US at a low intensity (2.0 w/cm 2 , 1 MHz) for 4 min three times per week each after the intraperitoneal administration of irinotecan; this treatment was continued for 5 weeks. The tumor vascularity was assessed by contrastenhanced color Doppler US in real time. The combination treatment significantly inhibited the mobilization of CEP and intratumoral vascularity compared with the control. This combination therapy showed a significant reduction in tumor volume, resulting in a significant prolongation of survival, in comparison with each treatment alone. These results suggest that the effect of metronomic chemotherapy for human uterine sarcoma was accelerated by US irradiation in vivo and this combination might therefore be potentially effective for new cancer therapy. (Cancer Sci 2011; 102: 452-459)

Cancer stem cells (CSCs) that display tumor-initiating properties have recently been identified. CD133, a surface glycoprotein linked to organ-specific stem cells, has been described as a marker of CSCs in different tumor types. We herein identify and characterize CSCs in human uterine carcinosarcoma (malignant mixed Mü llerian tumor), which is one of the most aggressive and therapy-resistant gynecological malignancies and is considered to be of mesodermal origin. The CD133 1 population was increased in uterine carcinosarcoma, and this population showed biphasic properties in the primary tumor. CD1331 cells predominantly formed spheres in culture and were able to differentiate into mesenchymal lineages. CD1331 cells were more resistant to cisplatin/paclitaxel-induced cytotoxicity in comparison with CD133 2 cells. A real-time polymerase chain reaction analysis of the genes implicated in stem cell maintenance revealed that CD133 1 cells express significantly higher levels of Oct4, Nanog, Sox2, and Bmi1 than CD133 2 cells. Moreover, CD133 1 cells showed a high expression level of Pax2 and Wnt4, which are genes essential for Mü llerian duct formation. These CD133 1 cells form serially transplantable tumors in vivo and the resulting CD1331 tumors replicated the EpCAM, vimentin, and estrogen and progesterone receptor expression of the parent tumor, indicating that CSCs likely differentiated into cells comprising the uterine carcinosarcoma tissue. Moreover, strong CD133 expression in both epithelial and mesenchymal elements in primary tumor demonstrated significant prognostic value. These findings suggest that CD1331 cells have the characteristics of CSCs and Mü llerian mesenchymal progenitors.

Uterine carcinosarcoma is a highly aggressive gynecological neoplasm that responds poorly to conventional chemotherapy and radiotherapy. Metronomic chemotherapy is accepted as a new approach for cancer treatment, and its underlying mechanism seems to involve the suppression of angiogenesis. However, the efficacy of metronomic and anti-angiogenic therapies against uterine carcinosarcoma is unknown. The anti-angiogenic effect of doxifluridine was assessed in vitro using human umbilical vein endothelial cells (HUVEC) co-cultured with FU-MMT-1 human uterine carcinosarcoma cells. The antitumor and anti-angiogenic effects of metronomic doxifluridine (delivered via oral gavage) in combination with TNP-470 were evaluated in vivo. Tumor vascularity was assessed by contrast-enhanced color Doppler ultrasound, laser Doppler and microvessel density staining. Doxifluridine suppressed tube formation of HUVEC and vascular endothelial growth factor production by FU-MMT-1 cells. Metronomic doxifluridine alone significantly suppressed tumor growth compared with the untreated (control) group, while metronomic doxifluridine in combination with TNP-470 significantly inhibited tumor growth compared with each treatment alone. A significant reduction of intratumoral vascularity was observed in FU-MMT-1 xenografts following treatment with metronomic doxifluridine in combination with TNP-470, as compared with each treatment alone. Intestinal bleeding was only observed when the maximum tolerated dose of doxifluridine was administered in combination with TNP-470. Metronomic doxifluridine chemotherapy in combination with TNP-470 might be effective for uterine carcinosarcoma without marked toxicity, possibly acting via its potent anti-angiogenic effects. Clinical studies are needed to evaluate the safety and efficacy of this treatment in humans.