This study was designed to evaluate the role of heat shock protein 90 (HSP90) in tumor progression of murine islet cell tumors. Blockade of HSP90 has recently been proposed as a therapeutic target, but effects in models of islet cell tumors with AUY922, a newly developed HSP90 inhibitor, have not been examined.The carcinoid cell line BON-1 and the HSP90 inhibitor AUY922 were used to determine effects on signaling and growth in vitro. In vivo transgenic RIP1-Tag2 mice, which develop islet cell neoplasms, were treated with vehicle or AUY922 (25 mg/kg/twice per week) from week 5 until death. The resected pancreata were evaluated macroscopically and microscopically by immunohistochemistry. Quantitative real-time PCR was performed for HSP90 targets with RNA from islets isolated from treated and untreated RIP1-Tag2 mice.HSP90 blockade impaired constitutive and growth factor-induced signaling in vitro. Moreover, HSP90 inhibition attenuated in vitro cell growth in a dose-dependent manner. In vivo, AUY922 significantly reduced tumor volume by 92% compared to untreated controls (p = 0.000), and median survival in the used transgenic mouse model was prolonged (110 vs. 119 days; p = 0.75). Quantitative real-time PCR for downstream target genes of HSP90 demonstrated significant downregulation in the islet cell tumors of RIP1-Tag2 mice treated with AUY922, confirming our ability to achieve effective pharmacologic levels of AUY922 within the desired tissue site in vivo.This is the first study to show that the HSP90 antagonist AUY922 may provide a new option for therapy of islet cell neoplasms.
Supplementary Figure 1 from Blockade of Hedgehog Signaling Inhibits Pancreatic Cancer Invasion and Metastases: A New Paradigm for Combination Therapy in Solid Cancers
<div>Abstract<p>In the context of pancreatic cancer, metastasis remains the most critical determinant of resectability, and hence survival. The objective of this study was to determine whether Hedgehog (Hh) signaling plays a role in pancreatic cancer invasion and metastasis because this is likely to have profound clinical implications. In pancreatic cancer cell lines, Hh inhibition with cyclopamine resulted in down-regulation of <i>snail</i> and up-regulation of <i>E-cadherin</i>, consistent with inhibition of epithelial-to-mesenchymal transition, and was mirrored by a striking reduction of <i>in vitro</i> invasive capacity (<i>P</i> < 0.0001). Conversely, <i>Gli1</i> overexpression in immortalized human pancreatic ductal epithelial cells led to a markedly invasive phenotype (<i>P</i> < 0.0001) and near total down-regulation of <i>E-cadherin</i>. In an orthotopic xenograft model, cyclopamine profoundly inhibited metastatic spread; only one of seven cyclopamine-treated mice developed pulmonary micrometastases versus seven of seven mice with multiple macrometastases in control animals. Combination of gemcitabine and cyclopamine completely abrogated metastases while also significantly reducing the size of “primary” tumors. <i>Gli1</i> levels were up-regulated in tissue samples of metastatic human pancreatic cancer samples compared with matched primary tumors. Aldehyde dehydrogenase (ALDH) overexpression is characteristic for both hematopoietic progenitors and leukemic stem cells; cyclopamine preferentially reduced “ALDH-high” cells by ∼3-fold (<i>P</i> = 0.048). We confirm pharmacologic Hh pathway inhibition as a valid therapeutic strategy for pancreatic cancer and show for the first time its particular efficacy against metastatic spread. By targeting specific cellular subpopulations likely involved in tumor initiation at metastatic sites, Hh inhibitors may provide a new paradigm for therapy of disseminated malignancies, particularly when used in combination with conventional antimetabolites that reduce “bulk” tumor size. [Cancer Res 2007;67(5):2187–96]</p></div>
Cancer cachexia describes a syndrome of muscle wasting and lipolysis that is still largely untreatable and negatively impacts prognosis, mobility, and healthcare costs. Since upregulation of skeletal muscle monoamine-oxidase-A (MAO-A), a source of reactive oxygen species, may contribute to cachexia, we investigated the effects of the MAO-inhibitor harmine-hydrochloride (HH, intraperitoneal, 8 weeks) on muscle wasting in a triple-transgenic mouse model of pancreatic ductal adenocarcinoma (PDAC) and wild type (WT) mice. Gastrocnemius and soleus muscle cryo-cross-sections were analyzed for fiber type-specific cross-sectional area (CSA), fraction and capillarization using ATPase- and lectin-stainings. Transcripts of pro-apoptotic, -atrophic, and -inflammatory signals were determined by RT-qPCR. Furthermore, we evaluated the integrity of neuromuscular junction (NMJ, pre-/post-synaptic co-staining) and mitochondrial ultrastructure (transmission electron microscopy). MAO-A expression in gastrocnemius muscle was increased with PDAC vs. WT (immunohistochemistry: p < 0.05; Western blot: by trend). PDAC expectedly reduced fiber CSA and upregulated IL-1β in both calf muscles, while MuRF1 expression increased in soleus muscle only. Although IL-1β decreased, HH caused an additional 38.65% (p < 0.001) decrease in gastrocnemius muscle (IIBX) fiber CSA. Moreover, soleus muscle CSA remained unchanged despite the downregulation of E3-ligases FBXO32 (p < 0.05) and MuRF1 (p < 0.01) through HH. Notably, HH significantly decreased the post-synaptic NMJ area (quadriceps muscle) and glutathione levels (gastrocnemius muscle), thereby increasing mitochondrial damage and centronucleation in soleus and gastrocnemius type IIBX fibers. Moreover, although pro-atrophic/-inflammatory signals are reversed, HH unfortunately fails to stop and rather promotes PDAC-related muscle wasting, possibly via denervation or mitochondrial damage. These differential adverse vs. therapeutic effects warrant studies regarding dose-dependent benefits and risks with consideration of other targets of HH, such as the dual-specificity tyrosine phosphorylation regulated kinases 1A and B (DYRK1A/B).
As more knowledge on molecular alterations favoring carcinogenesis and spreading of gastroenteropancreatic endocrine tumors has become available, a number of targeted agents interfering with key growth and angiogenic pathways have been explored in preclinical and clinical studies. The mTOR inhibitor Everolimus, and the multi-target antiangiogenetic agent Sunitinib, have been shown to be effective and thus have been approved by the FDA for treatment of pancreatic endocrine tumors. However, there is little data on the primary resistance to targeted agents on these tumors. The goals of the present review are to elucidate the possible advantage of combined treatments in overcoming induced resistances, and to identify biomarkers able to predict clinical efficacy. Moreover, the role of interesting targets for which a strong biological rationale exists, and specific inhibitors are available, such as the Src Family Kinases and the Hedgehog Pathway, are discussed. There is now need for more preclinical studies on cell lines and animal models to provide a stronger preclinical background in this field, as well as clinical trials specifically comparing one targeted therapy with another or combining different targeted agents.
