Purpose: Histone deactylase inhibitors (HDACi) are a promising new class of anticancer therapeutics; however, little is known about HDACi activity in soft tissue sarcoma (STS), a heterogeneous cohort of mesenchymal origin malignancies. Consequently, we investigated the novel HDACi PCI-24781, alone/in combination with conventional chemotherapy, to determine its potential anti-STS-related effects and the underlying mechanisms involved. Experimental Design: Immunoblotting was used to evaluate the effects of PCI-24781 on histone and nonhistone protein acetylation and expression of potential downstream targets. Cell culture-based assays were utilized to assess the effects of PCI-24781 on STS cell growth, cell cycle progression, apoptosis, and chemosensitivity. Quantitative reverse transcription-PCR, chromatin immunoprecipitation, and reporter assays helped elucidate molecular mechanisms resulting in PCI-24781-induced Rad51 repression. The effect of PCI-24781, alone or with chemotherapy, on tumor and metastatic growth was tested in vivo using human STS xenograft models. Results: PCI-24781 exhibited significant anti-STS proliferative activity in vitro, inducing S phase depletion, G 2 /M cell cycle arrest, and increasing apoptosis. Superior effects were seen when combined with chemotherapy. A PCI-24781-induced reduction in Rad51, a major mediator of DNA double-strand break homologous recombination repair, was shown and may be a mechanism underlying PCI-24781 chemosensitization. We showed that PCI-24781 transcriptionally represses Rad51 through an E2F bindingsite on the Rad51 proximal promoter. Although single-agent PCI-24781 had modest effects on STS growth and metastasis, marked inhibition was observed when combined with chemotherapy. Conclusions: In light of these findings, this novel molecular-based combination may be applicable to multiple STS histologic subtypes, and potentially merits rigorous evaluation in human STS clinical trials.Antimetastatic soft tissue sarcoma (STS) systemic therapies remain elusive, resulting in 50% 5-year overall survival rates remaining stagnant for at least 30 years (1). New approaches are urgently needed yet difficult to develop because STS are rare and typified by marked intratumor and intertumor heterogeneity (2), rendering identification of specific STS subtype molecular "addictions" and their inhibition problematic (3). Alternatively, identifying target pathways that serve as convergence points for multiple STS subtypes is appealing; histone deacytelase inhibition is one such potential therapeutic strategy not yet explored in STS (4).Chromatin structure is affected by posttranslational core-histone modifications, including acetylation and deacetylation (5). Core-histone acetylation states, important for chromatin structure, function, and gene expression, are controlled by opposing actions of histone acetyl transferase enzymes and histone deacetylases (HDAC; ref. 6). The histone acetyl transferase enzymes:HDAC balance is crucial for normal cell growth maintenance; deregulat...

The AKT signaling pathway is activated in soft tissue sarcoma (STS). However, AKT blockade has not yet been studied as a potential targeted therapeutic approach. Here, we examined the in vitro and in vivo effects of AKT inhibition in STS cells. Western blot analysis was used to evaluate the expression of AKT pathway components and the effect of AKT stimulation and inhibition on their phosphorylation. Cell culture assays were used to assess the effect of AKT blockade (using a phosphatidylinositol 3-kinase inhibitor and a specific AKT inhibitor) on STS cell growth, cell cycle, and apoptosis. Oligoarrays were used to determine gene expression changes in response to AKT inhibition. Reverse transcription-PCR was used for array validation. Specific small inhibitory RNA was used to knockdown GADD45A. Human STS xenografts in nude mice were used for in vivo studies, and immunohistochemistry was used to assess the effect of treatment on GADD45A expression, proliferation, and apoptosis. Multiple STS cell lines expressed activated AKT. AKT inhibition decreased STS downstream target phosphorylation and growth in vitro; G 2 cell cycle arrest and apoptosis were also observed. AKT inhibition induced GADD45a mRNA and protein expression in all STS cells treated independent of p53 mutational status. GADD45A knockdown attenuated the G 2 arrest induced by AKT inhibition. In vivo, AKT inhibition led to decreased STS xenograft growth. AKT plays a critical role in survival and proliferation of STS cells. Modulation of AKT kinase activity may provide a novel molecularly based strategy for STStargeted therapies. [Cancer Res 2008;68(8):2895-903]

Purpose: Novel therapeutic approaches for complex karyotype soft tissue sarcoma (STS) are crucially needed. Consequently, we assessed the efficacy of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), in combination with chemotherapy, on local and metastatic growth of human STS xenografts in vivo.Experimental Design: TRAIL was evaluated alone and combined with low-dose doxorubicin in two human STS severe combined immunodeficient mouse xenograft models using fibrosarcoma (HT1080; wild-type p53) and leiomyosarcoma (SKLMS1; mutated p53), testing for effects on local growth, metastasis, and overall survival. Magnetic resonance imaging was used to evaluate local growth and bioluminescence was used to longitudinally assess lung metastases. Tissues were evaluated through immunohistocemistry and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining for treatment effects on tumor cell proliferation, apoptosis, angiogenesis, angiogenic factors, and TRAIL receptor expression. Quantitative real-time polymerase chain reaction (QRTPCR) angiogenesis array was used to assess therapy-induced gene expression changes.Results: TRAIL/doxorubicin combination induced marked STS local and metastatic growth inhibition in a p53-independent manner. Significantly increased (P < 0.001) host survival was also demonstrable. Combined therapy induced significant apoptosis, decreased tumor cell proliferation, and increased TRAIL receptor (DR4 and DR5) expression in all treated tumors. Moreover, decreased microvessel density was observed, possibly secondary to increased expression of the antiangiogenic factor CXCL10 and decreased proangiogenic interleukin-8 cytokine in response to TRAIL/doxorubicin combination, as was also observed in vitro.Conclusions: Given the urgent need for better systemic approaches to STS, clinical trials evaluating TRAIL in combination with low-dose chemotherapy are potentially warranted. Clin Cancer Res; 16(9); 2591-604. ©2010 AACR.Complex karyotype soft tissue sarcoma (STS; e.g., leiomyosarcoma and unclassified pleomorphic sarcoma) pose a significant therapeutic challenge (1). Surgical resection combined with radiotherapy is the optimal approach for localized STS management (2). However, STS exhibit a marked propensity for local and systemic failure, frequently manifesting therapeutic resistance. Doxorubicin, the single most active anti-STS chemotherapeutic agent, has a disappointing 30% overall response rate. After initial chemoresponsiveness, breakthrough tumor progression and local and/or distant recurrence are frequently observed (3, 4), contributing to a 50% 5-year STS overall survival rate that has remained stagnant for ∼50 years. Accordingly, more effective therapeutic approaches to complex karyotype STS are critically needed.One of the hallmarks of STS and other malignancies is their pronounced resistance to apoptosis, resulting in cell survival even when confronted by multiple stress stimuli. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L), a ...

Purpose: The epidermal growth factor receptor (EGFR) is highly expressed in many human soft tissue sarcomas (STS). However, EGFR blockade has not apparently been used for human STS therapy; therefore, we examined the in vitro and in vivo effects and the underlying mechanisms before considering EGFR blockade as a therapy for STS patients. Experimental Design: Human STS tissues and cell lines were used to study EGFR expression and activation. Western blot analysis was used to evaluate effects of EGFR activation on downstream signaling. Cell culture assays were used to assess the effect of EGF stimulation as well as EGFR blockade (using an EGFR tyrosine kinase inhibitor, Iressa; AstraZeneca) on STS cell growth, apoptosis, and chemosensitivity. An in vivo study (HT1080 human fibrosarcoma cell line in nude/nude mice: Iressa, doxorubicin, Iressa + doxorubicin, vehicle) was used to examine tumor growth; pEGFR, proliferating cell nuclear antigen, and terminal deoxyribonucleotide transferasem ediated nick-end labeling staining helped assess the effect of therapy in vivo on STS EGFR activation, proliferation, and apoptosis. Results: EGFR was expressed and activated in STS cell lines and tumors, probably due to ligand binding rather than EGFR mutation. Stimulation caused activation of AKTand mitogen-activated protein kinase pathways. EGFR blockade inhibited these effects and also caused increased apoptosis, a p53-independent G 0 -G 1 cell cycle arrest, and decreased cyclin D1 expression. In vivo, Iressa + doxorubicin had markedly synergistic anti-STS effects. Conclusion: EGFR blockade combined with conventional chemotherapy results in anti-human STS activity in vitro and in vivo, suggesting the possibility that combining these synergistic treatments will improve anti-STS therapy.

Dendritic cell (DC)-based tumor vaccines have only achieved limited clinical efficacy, underscoring the limitation of stimulatory strategies to elicit effective cytotoxic T lymphocyte (CTL) responses against self-tumor-associated antigens. Here, we investigate the role of human suppressor of cytokine signaling 1 (SOCS1), a feedback inhibitor of the Janusactivated kinase/signal transducer and activator of transcription signaling pathway, in regulating antigen presentation by human DCs (hDC). We find that human SOCS1 (hSOCS1)-silenced DCs have an enhanced stimulatory ability to prime self-antigen-specific CTLs in vitro and in a severe combined immunodeficient-hu mouse model. Human CTLs activated by SOCS1-silenced DCs, but not wild-type DCs, have an active lytic activity to natural antigen-expressing tumor cells. We further find that the capacity of hDCs to prime CTLs is likely controlled by SOCS1-restricted production and signaling of proinflammatory cytokines, such as interleukin-12. These results indicate a critical role of hSOCS1 in negatively regulating the immunostimulatory capacity of DCs and imply a translational potential of this alternative SOCS1 silencing strategy to develop effective DC vaccines. [Cancer Res 2009;69(20):8076-84]

Tumor cells harbor unique genetic mutations, which lead to the generation of immunologically foreign antigenic peptide repertoire with the potential to induce individual tumor-specific immune responses. Here, we developed an in situ tumor vaccine with the ability to elicit antitumor immunity. This vaccine comprised an E1B-deleted oncolytic adenovirus expressing beta-defensin-2 (Ad-BD2-E1A) for releasing tumor antigens, recruiting and activating plasmacytoid dendritic cells (pDCs). Intratumoral injections of Ad-BD2-E1A vaccine inhibited primary breast tumor growth and blocked naturally occurring metastasis in mice. Ad-BD2-E1A vaccination induced potent tumor-specific T-cell responses. Splenic and intratumoral DCs isolated from Ad-BD2-E1A-immunized mice were able to stimulate or promote the differentiation of naive T cells into tumor-specific cytotoxic T cells. We further found that the increased numbers of mature CD45RA(+)CD8alpha(+)CD40(+) pDCs infiltrated into Ad-BD2-E1A-treated tumors. The antitumor effect of Ad-BD2-E1A vaccination was abrogated in toll-like receptor 4 (TLR4) deficient mice, suggesting the critical role of TLR4 in the induction of antitumor immunity by Ad-BD2-E1A. The results of this study indicate that in situ vaccination with the oncolytic BD2-expressing adenovirus preferentially attracts pDCs and promotes their maturation, and thus elicits potent tumor-specific immunity. This vaccine represents an attractive therapeutic strategy for the induction of individualized antitumor immunity.

ABSTRACT

Purpose: Soft tissue sarcoma (STS) is a rare heterogeneous malignancy. Overall survival has been stagnant for decades, primarily because systemic therapies are ineffective versus metastases, the leading cause of STS lethality. Consequently, we examined whether tyrosine kinase receptors active in STS growth signaling might be blockable and whether multireceptor blockade might synergize with low-dose STS chemotherapy by therapeutically affecting STS cells and their associated microenvironment. Experimental Design: Vandetanib (AstraZenca), a tyrosine kinase inhibitor of vascular endothelial growth factor receptor 2 and epidermal growth factor receptor, was evaluated alone and with chemotherapy in vitro and in vivo in three human STS nude mouse xenograft models of different STS locations (muscle, uterus, lung), stages (primary, metastatic), and subtypes (leiomyosarcoma, fibrosarcoma, uterine sarcoma: luciferase-expressing MES-SA human uterine sarcoma cells surgically implanted into uterine muscularis with bioluminescence tumor growth assessment; developed by us). Results: In vitro, human STS cells were sensitive to vandetanib. Vandetanib alone and with chemotherapy statistically significantly inhibited leiomyosarcoma local growth and fibrosarcoma lung metastasis. Direct injection of MES-SA into nude mice uterine muscularis resulted in high tumor take (88%), whereas s.c. injection resulted in no growth, suggesting microenvironmental tumor growth modulation. Vandetanib alone and with chemotherapy statistically significantly inhibited uterine sarcoma growth. In all models, vandetanib induced increased apoptosis, decreased tumor cell proliferation, and decreased angiogenesis. Conclusions: Vandetanib has antitumor effects against human STS subtypes in vitro and in vivo, where it also affects the tumor-associated microenvironment. Given the urgent need for better systemic approaches to STS, clinical trials evaluating vandetanib, perhaps with low-dose chemotherapy, seem warranted.Available soft tissue sarcoma (STS) chemotherapies have modest response rates with significant toxicities (1). Consequently, new STS therapies must be developed to improve the current STS 5-year survival rates of <50%. However, new STS treatment development and trials validation are hampered by their rarity and remarkable clinical heterogeneity. More than 50 separate STS histologic subtypes are recognized; these possess markedly diverse clinical courses and outcomes, perhaps reflecting the complex and variable array of molecular derangements underlying these STS biological distinctions (2). In the era of targeted therapeutics, exploiting any relevant unifying molecular abnormalities as might exist in STS has appeal. Analogous to solid malignancies, STS consist of both tumor and tumor-associated normal cells; STS growth, migration, and dissemination depend on cross-talk between these two compartments. STS are generally highly vascular and angiogenic, resulting in increased metastatic potential (3). Amidst diversity, these common STS proper...