Pancreatic cancer is one of the most aggressive human cancers with a 5-year survival rate of <5%. Overexpression of transforming growth factor-beta 2 (TGF-b2) in pancreatic malignancies is suggested to be a pivotal factor for malignant progression by inducing immunosuppression, metastasis, angiogenesis and proliferation. Trabedersen (AP 12009) is a phosphorothioate antisense oligodeoxynucleotide specific for human TGF-b2 mRNA and was successfully tested in a randomized, active-controlled phase IIb clinical study in patients with high-grade glioma. Here, we report on the antitumor activity of trabedersen in human pancreatic cancer cells and in an orthotopic xenograft mouse model of human metastatic pancreatic cancer. Trabedersen reduced TGF-b2 secretion in human pancreatic cell lines with an IC 50 in the low lM range without transfection reagent, clearly inhibited cell proliferation, and completely blocked migration of pancreatic cancer cells. Additionally, trabedersen reversed TGF-b2-mediated immunosuppression of pancreatic cancer cells targeted by lymphokine activated killer (LAK) cells, resulting in considerably increased LAK cell-mediated cytotoxicity. Moreover, in an orthotopic mouse model of metastatic pancreatic cancer, intraperitoneal (i.p.) treatment with trabedersen significantly reduced tumor growth, lymph node metastasis and angiogenesis. These promising results warrant further clinical development of trabedersen. (Cancer Sci 2011; 102: 1193-1200

To investigate temporal changes in capillarization and increases in mitochondrial enzyme activity, rabbit tibialis anterior muscles underwent chronic low-frequency stimulation for up to 50 days. Capillary density (CD), capillary-to-fiber ratio (C/F), intercapillary distance (ICD), and mean capillary area (MCA), as well as several other parameters of capillarization, were examined. In addition, tissue levels of mRNA specific to vascular endothelial growth factor (VEGF) were assessed by reverse transcriptase-polymerase chain reaction. Citrate synthase (CS) activity, a marker of aerobic-oxidative metabolic potential, was measured in the same muscles. Significant increases in CD and C/F, respectively, and decreases in ICD and MCA were observed after 2 days. These changes reached stable maxima by 14 days. The increases in capillarization occurred in a fiber-type-specific manner, affecting type IId fibers before types IIda and IIa. VEGF mRNA levels increased in a bimodal time pattern with a first elevation (2.5-fold) after 1 day and a second (9-fold) after 6–8 days. Increases in CS were first noted after 8 days. Obviously, increases in capillarization as induced by enhanced contractile activity precede increases in the aerobic-oxidative potential of energy metabolism.

A quantitative reverse transcriptase-polymerase chain reaction was established to determine absolute amounts of mRNAs specific to four myosin heavy chain isoforms [MHCIIb, MHCIId(x), MHCIIa, and MHCIβ] in rat extensor digitorum longus muscle during forced contractile activity by chronic (10 h/day) low-frequency stimulation (CLFS). The induced changes in absolute and relative mRNA amounts were similar. MHCIIb mRNA decreased rapidly after 1 day, and MHCIIa mRNA increased after 3 days. MHCIId(x) started to decrease at day 7. After 42 days, the MHCIIb, MHCIId(x), MHCIIa, and MHCIβ mRNAs amounted to 2, 6, 90, and 2% of total MHC mRNAs, respectively. Changes at the protein level were studied in a second experimental series increasing CLFS (24 h/day, up to 100 days). Also under these conditions, MHCIβ reached only a fraction of 12% (2-fold elevation). The changes at the protein level remained restricted to the MHCIIb to MHCIIa transition, which agrees with the notion that the induced changes in MHC isoform expression primarily resulted from altered pretranslational activities. Rat fast-twitch muscle thus exhibits a restricted capacity for fast-to-slow conversion.

Despite remarkable advances in cancer research, patients with malignant tumors such as high-grade glioma or advanced pancreatic carcinoma still face a poor prognosis. Because of the severe morbidity and mortality of such malignant tumor types, the identification of suitable molecular drug targets for causal treatment approaches is an important area of current research. Transforming growth factor-beta 2 (TGF-β2) is an attractive target because it regulates key mechanisms of carcinogenesis, in particular immunosuppression and metastasis, and is frequently overexpressed in malignant tumors. Here we describe the development of the antisense phosphorothioate oligodeoxynucleotide trabedersen (AP 12009) which was designed for the specific inhibition of TGF-β2 biosynthesis. In vitro and in vivo experiments confirmed the mode of action, efficacy and tolerability of trabedersen and paved the way for clinical studies. In patients with high-grade glioma, intratumoral treatment with trabedersen is currently evaluated in a pivotal, randomized and active-controlled phase III study. Intravenous application of trabedersen for the treatment of patients with advanced pancreatic carcinoma, metastasizing melanoma, or metastatic colorectal carcinoma is assessed in a currently ongoing phase I/II dose escalation study.

Understanding the intrinsic mediators that render CD8+ T cells dysfunctional in the tumor microenvironment is a requirement to develop more effective cancer immunotherapies. Here, we report that C/EBP homologous protein (Chop), a downstream sensor of severe endoplasmic reticulum (ER) stress, is a major negative regulator of the effector function of tumor-reactive CD8+ T cells. Chop expression is increased in tumor-infiltrating CD8+ T cells, which correlates with poor clinical outcome in ovarian cancer patients. Deletion of Chop in T cells improves spontaneous antitumor CD8+ T cell immunity and boosts the efficacy of T cell-based immunotherapy. Mechanistically, Chop in CD8+ T cells is elevated primarily through the ER stress-associated kinase Perk and a subsequent induction of Atf4; and directly represses the expression of T-bet, a master regulator of effector T cell function. These findings demonstrate the primary role of Chop in tumor-induced CD8+ T cell dysfunction and the therapeutic potential of blocking Chop or ER stress to unleash T cell-mediated antitumor immunity.