The combination of the tyrosine kinase receptor inhibitor SU6668 with paclitaxel affects ascites formation and tumor spread in ovarian carcinoma xenografts growing orthotopically.

PURPOSE: The purpose of this study was to investigate the antitumor activity of SU6668, tyrosine kinase inhibitor of vascular endothelial growth factor receptor 2 (VEGFR2), fibroblast growth factor receptor 1 (FGFR1), and platelet-derived growth factor receptor beta (PDGFRbeta), as single-agent therapy and in combination with paclitaxel on ovarian carcinoma xenograft models transplanted in the peritoneal cavity of nude mice. EXPERIMENTAL DESIGN: HOC22 and HOC79 ascites-producing human ovarian carcinoma xenografts were transplanted i.p. into nude mice. SU6668 was given p.o. (200 mg/kg, daily) as a single agent or in combination with paclitaxel i.v. (6 mg/kg/dose every other day or 20 mg/kg/dose weekly). Tumor burden was evaluated at the end of the treatment period as ascites volume and tumor cells, VEGF, FGF-2, and PDGF levels in ascites, and involvement of the organ of the peritoneal cavity. Response was evaluated as percentage increment of life span (%ILS). RESULTS: SU6668 affected ascites formation and tumor burden in the peritoneal cavity of nude mice bearing HOC22 and HOC79 xenografts. Decreased levels of VEGF and PDGF in ascites paralleled this effect. The overall survival of the mice bearing HOC xenograft (HOC79 less response than HOC22) was significantly increased by the treatment with SU6668. The magnitude of the effects depended on the length of treatment and tumor burden at the beginning of treatment. The combination of SU6668 with paclitaxel significantly prolonged the survival of mice bearing HOC79, compared with single therapies. SU6668-based combination therapy was more effective with paclitaxel given at the optimal dose and schedule (20 mg/kg every 7 days for 3 doses) than at the same total dose but split (6 mg/kg every 2 days for 10 doses). However, a similar outcome was observed when giving high-dose paclitaxel (20 mg/kg every 7 days for 3 doses) in monotherapy or split low-dose paclitaxel (6 mg/kg every 2 days for 10 doses) but in combination with SU6668. The addition of paclitaxel, by either schedule, to SU6668 treatment inhibited tumor spread in the peritoneal organs (omentum, pancreas, and diaphragm) even at low doses of paclitaxel. A greater effect was observed with prolonged treatments. CONCLUSIONS: This study shows that SU6668 in combination with paclitaxel inhibits ovarian carcinoma progression in the peritoneal cavity, by blocking ascites formation and tumor spread. Because an adequate schedule and dose of the combination might be as effective as conventional chemotherapy, this should be considered as a therapeutic alternative. These findings provide a rationale for the clinical evaluation of combination therapies affecting multiple biological targets in this tumor type.

Antiangiogenic and antitumor activity of IDN 5390, a new taxane derivative.

PURPOSE: We previously reported that paclitaxel, a microtubule-stabilizing drug, inhibited angiogenesis, mainly by inhibiting endothelial cell motility (D. Belotti et al., Clin. Cancer Res., 2: 1843-1849, 1996). The aim of this study was to select a taxane with little cytotoxicity but with antimotility and hence antiangiogenic activity. EXPERIMENTAL DESIGN: Different taxanes, seco derivatives, and 14-beta-hydroxy-10-deacetyl baccatin III derivatives were tested for their effects on the proliferation and motility of human umbilical vein endothelial cells. The antiangiogenic and antineoplastic activities of the compound selected from this screening were further investigated in experimental models in vitro and in vivo. RESULTS: From the screening of different taxanes, we selected IDN 5390, a seco derivative that showed potent antimotility activity and less cytotoxicity than paclitaxel. In comparable experimental conditions, IDN 5390 inhibited endothelial cell migration without affecting proliferation. This compound dose-dependently inhibited the capacity of human umbilical vein endothelial cells plated on Matrigel to organize into a network of cords. In vivo, IDN 5390 significantly inhibited fibroblast growth factor-2-induced angiogenesis in Matrigel implants. Daily treatment with IDN 5390 in mice bearing established lung micrometastases from the B16BL6 murine melanoma caused a reduction in the size of metastases. Finally, IDN 5390 slowed the s.c. growth of the paclitaxel-resistant human ovarian carcinoma, 1A9/PTX22, xenografted in nude mice. CONCLUSIONS: The seco derivative IDN 5390 might represent the prototype of a new class of taxane derivatives with antiangiogenic properties.

Gene expression correlating with response to paclitaxel in ovarian carcinoma xenografts.

We have investigated gene expression profiles of human ovarian carcinomas in vivo during Taxol(R) (paclitaxel) treatment and observed a difference in expression. Nude mice bearing 1A9 or 1A9PTX22 xenografts were given 60 mg/kg of paclitaxel. Therapeutic efficacy was achieved for 1A9, while 1A9PTX22 did not respond. Tumor tissues harvested 4 and 24 h after treatment were evaluated by cDNA microarray against untreated tumors. Paclitaxel caused the modulation of more genes in 1A9 than in 1A9PTX22 tumors, in accordance to their therapeutic response. Most gene expression alterations were detected 24 h after paclitaxel administration and affected genes involved in various biological functions including cell cycle regulation and cell proliferation (CDC2, CDKN1A, PLAB, and TOP2A), apoptosis (BNIP3 and PIG8), signal transduction and transcriptional regulation (ARF1, ATF2, FOS, GNA11, HDAC3, MADH2, SLUG, and SPRY4), fatty acid biosynthesis and sterol metabolism (FDPS, IDI1, LIPA, and SC5D), and IFN-mediated signaling (G1P3, IFI16, IFI27, IFITM1, and ISG15). The modulation of two representative genes, CDKN1A and TOP2A, was validated by Northern analyses on a panel of seven ovarian carcinoma xenograft models undergoing treatment with paclitaxel. We found that the changes in expression level of these genes was strictly associated with the responsiveness to paclitaxel. Our study shows the feasibility of obtaining gene expression profiles of xenografted tumor models as a result of drug exposure. This in turn might provide insights related to the drugs' action in vivo that will anticipate the response to treatment manifested by tumors and could be the basis for novel approaches to molecular pharmacodynamics.

Small molecules in anti-angiogenic therapy.

Angiogenesis, or the formation of new blood vessels from preexisting capillaries, is a sequence of events that occurs in many physiological and pathological conditions, including cancer. The identification of several pro-angiogenic factors and the recent description of endogenous inhibitors of angiogenesis, has made interference with vessel formation an attractive potential therapeutic option. Several compounds with anti-angiogenic or antivascular properties have been identified, and several of them have entered patient studies in cancer on the basis of promising preclinical results. However, this development of compounds that are not directly cytotoxic to cancer cells is problematic in terms of trial design and interpretation. This review discusses classes of molecules that interfere specifically with regulatory elements of the angiogenic process, and comments upon their stage of development and characteristics in clinical trials.