Abstract 2362: Targeted suppression of TGF-beta2 by trabedersen (AP 12009) in an orthotopic xenograft melanoma mouse model

Abstract

Abstract Background: TGF-β2 is a mediator of carcinogenesis by regulating key mechanisms such as cell proliferation, metastasis, and immunosuppression. The antisense oligonucleotide trabedersen (AP 12009) specifically inhibits TGF-β2 expression. Clinical studies already demonstrated its antitumor activity in pancreatic cancer, high-grade glioma, and malignant melanoma. Here we examined the anti-tumorigenic and anti-metastatic effects of trabedersen in an orthotopic xenograft melanoma mouse model. Methods: BALB/c nu/nu mice were intradermally injected with 0.5x10E6 cells of the human TGF-β2 expressing melanoma cell line C8161. Intraperitoneal treatment with different doses of trabedersen or vehicle (controls) started 2 days after tumor implantation thrice weekly. Doses of trabedersen were 50/16 mg/kg (i.e. initial dose of 50 mg/kg and subsequent 16 mg/kg), 16 mg/kg, 4 mg/kg, 1 mg/kg, and 0.25 mg/kg. Treatment continued until first tumor reached 2000 mm3 (approx. 32-35 days after inoculation). The incidence of liver and lung metastases as well as growth and weight of the dermal tumors were determined. To evaluate the immunomodulatory effect of trabedersen, NK cells and MDSCs prepared from spleens were analyzed of trabedersen-treated or control mice (flow cytometry; MDSCs: anti-CD11b+, anti-Ly6G, anti-Ly6C; NK cells: CD49+, CD314+). Cellular uptake was examined by using fluorescently labeled trabedersen (5′-FAM-AP 12009) which was intra-tumorally injected 4 h prior to termination of the study. Cryosections were semi-quantitatively evaluated for the presence of fluorescence. Results: Tumor weight was significantly reduced for trabedersen-treated mice (50/16 mg/kg) compared to control (0.395 g vs. 0.715 g, p<0.05). Moreover, a dose dependent response for trabedersen treatment with 1 mg/kg, 4 mg/kg, and 16 mg/kg regarding tumor weight and tumor growth was observed. Trabedersen treatment significantly inhibited lung metastasis. There was no difference for liver metastasis between trabedersen and control. Analysis of spleen cell preparations of trabedersen-treated and control mice revealed a trend to less monocytic MDSCs under trabedersen treatment. There was no difference in the amount of granulocytic MDSCs and NK cells between trabedersen-treated and control mice. Intra-cellular and intra-nuclear fluorescence was clearly detectable in all tumor sections of all mice receiving the intratumoral injection of 5′-FAM-AP 12009, indicating uptake of trabedersen in the tumor cells and nuclear localisation. Conclusions: In an orthotopic xenograft melanoma mouse model trabedersen demonstrated potent antitumor activity as it inhibits the tumor promoting and metastatic effects of TGF-β2 such as tumor cell proliferation and immunosuppression. This is in line with promising results from clinical studies in patients with advanced pancreatic cancer or malignant melanoma (Phase I/II). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2362. doi:1538-7445.AM2012-2362