These observations suggest that FASN can act as a prostate cancer oncogene in the presence of AR and that FASN exerts its oncogenic effect by inhibiting the intrinsic pathway of apoptosis.

Although B-Raf V600E is the most common somatic mutation in papillary thyroid carcinoma (PTC), how it induces tumor aggressiveness is not fully understood. Using gene set enrichment analysis and in vitro and in vivo functional studies, we identified and validated a B-Raf V600E gene set signature associated with tumor progression in PTCs. An independent cohort of B-Raf V600E -positive PTCs showed significantly higher expression levels of many extracellular matrix genes compared with controls. We performed extensive in vitro and in vivo validations on thrombospondin-1 (TSP-1), because it has been previously shown to be important in the regulation of tumor angiogenesis and metastasis and is present in abundance in tumor stroma. Knockdown of B-Raf V600E resulted in TSP-1 downregulation and a reduction of adhesion and migration/invasion of human thyroid cancer cells. Knockdown of TSP-1 resulted in a similar phenotype. B-Raf V600E cells in which either B-Raf V600E or TSP-1 were knocked down were implanted orthotopically into the thyroids of immunocompromised mice, resulting in significant reduction in tumor size and fewer pulmonary metastases from the primary carcinoma as compared with the control cells. Treatment of orthotopic thyroid tumors, initiated 1 week after tumor cell implantation with PLX4720, an orally available selective inhibitor of B-Raf V600E , caused a significant tumor growth delay and decreased distant metastases, without evidence of toxicity. In conclusion, B-Raf V600E plays an important role in PTC progression through genes (i.e., TSP-1) important in tumor invasion and metastasis. Testing of a patient's thyroid cancer for B-Raf V600E will yield important information about potential tumor aggressiveness and also allow for future use of targeted therapies with selective B-Raf V600E inhibitors, such as PLX4720. extracellular matrix | metastasis | papillary thyroid cancer | tumor microenvironment | cell invasion P apillary thyroid cancer (PTC), with its incidence increasing by almost 5% each year, currently ranks as the eighth most common malignancy diagnosed in women (1). Neck recurrences alone are responsible for a third of thyroid cancer-related deaths. There is no effective treatment for radioiodine-resistant metastatic disease; the 10-year survival rate in these cases is only 10% (2). Molecular understanding of the aggressive clinical behavior of this subset of patients is needed to develop new therapeutic options.

5′AMP-activated kinase (AMPK) constitutes a hub for cellular metabolic and growth control, thus representing an ideal therapeutic target for prostate cancers (PCas) characterized by increased lipogenesis and activation of mTORC1 pathway. However, whether AMPK activation itself is sufficient to block cancer cell growth remains to be determined. A small molecule screening was performed and identified MT 63–78, a specific and potent direct AMPK activator. Here, we show that direct activation of AMPK inhibits PCa cell growth in androgen sensitive and castration resistant PCa (CRPC) models, induces mitotic arrest, and apoptosis. In vivo, AMPK activation is sufficient to reduce PCa growth, whereas the allelic loss of its catalytic subunits fosters PCa development. Importantly, despite mTORC1 blockade, the suppression of de novo lipogenesis is the underpinning mechanism responsible for AMPK-mediated PCa growth inhibition, suggesting AMPK as a therapeutic target especially for lipogenesis-driven PCas. Finally, we demonstrate that MT 63–78 enhances the growth inhibitory effect of AR signaling inhibitors MDV3100 and abiraterone. This study thus provides a rationale for their combined use in CRPC treatment.

Deubiquitinating enzymes can prevent the destruction of protein substrates prior to proteasomal degradation. The ubiquitin-specific protease 2a (USP2a) deubiquitinates the antiapoptotic proteins Fatty Acid Synthase and Mdm2. Here, we show that when USP2a is overexpressed in nontransformed cells, it exhibits oncogenic behavior both in vitro and in vivo and prevents apoptosis induced by chemotherapeutic agents. Notably, USP2a silencing in several human cancer cell lines results in apoptosis. Gene set enrichment analysis, which focuses on groups of genes sharing biological function or regulatory pathways, was done on microarray expression data from human prostate cancers. The cell death-related gene set, as well as a selected cluster of validated p53 target genes, were significantly enriched in the low USP2a expression group of tumors. Conversely, genes implicated in fatty acid metabolism were significantly associated with tumors expressing high USP2a (44%). The expression profile analysis is consistent with the effects of USP2a on its known targets, i.e., Fatty Acid Synthase and Mdm2, defining a subset of prostate tumors resistant to apoptosis. USP2a thus represents a therapeutic target in prostate cancer. (Cancer Res 2006; 66(17): 8625-32)

Cancer cells may overcome growth factor dependence by deregulating oncogenic and/or tumor suppressor pathways that affect their metabolism, or by activating metabolic pathways de novo with targeted mutations in critical metabolic enzymes. It is unknown whether human prostate tumors develop a similar metabolic response to different oncogenic drivers or a particular oncogenic event results in its own metabolic reprogramming. Akt and Myc are arguably the most prevalent driving oncogenes in prostate cancer. Mass spectrometry-based metabolite profiling was performed on immortalized human prostate epithelial cells transformed by AKT1 or MYC, transgenic mice driven by the same oncogenes under the control of a prostate-specific promoter, and human prostate specimens characterized for the expression and activation of these oncoproteins. Integrative analysis of these metabolomic datasets revealed that AKT1 activation was associated with accumulation of aerobic glycolysis metabolites, whereas MYC overexpression was associated with dysregulated lipid metabolism. Selected metabolites that differentially accumulated in the MYC-high vs. AKT1-high tumors, or in normal vs. tumor prostate tissue by untargeted metabolomics, were validated using absolute quantitation assays. Importantly, the AKT1/MYC status was independent of Gleason grade and pathologic staging. Our findings show how prostate tumors undergo a metabolic reprogramming which reflects their molecular phenotypes, with implications for the development of metabolic diagnostics and targeted therapeutics.

The identification of biomarkers that distinguish between aggressive and indolent forms of prostate cancer (PCa) is crucial for diagnosis and treatment. In this study, we used cultured cells derived from prostate tissue from patients with PCa to define a molecular mechanism underlying the most aggressive form of PCa that involves the functional activation of eNOS and HIFs in association with estrogen receptor β (ERβ). Cells from patients with poor prognosis exhibited a constitutively hypoxic phenotype and increased NO production. Upon estrogen treatment, formation of ERβ/eNOS, ERβ/HIF-1α, or ERβ/HIF-2α combinatorial complexes led to chromatin remodeling and transcriptional induction of prognostic genes. Tissue microarray analysis, using an independent cohort of patients, established a hierarchical predictive power for these proteins, with expression of eNOS plus ERβ and nuclear eNOS plus HIF-2α being the most relevant indicators of adverse clinical outcome. Genetic or pharmacologic modulation of eNOS expression and activity resulted in reciprocal conversion of the transcriptional signature in cells from patients with bad or good outcome, respectively, highlighting the relevance of eNOS in PCa progression. Our work has considerable clinical relevance, since it may enable the earlier diagnosis of aggressive PCa through routine biopsy assessment of eNOS, ERβ, and HIF-2α expression. Furthermore, proposing eNOS as a therapeutic target fosters innovative therapies for PCa with NO inhibitors, which are employed in preclinical trials in non-oncological diseases. IntroductionIn the clinical management of prostate cancer (PCa), the second most common neoplasia in men worldwide (1), the ability to distinguish between aggressive and indolent forms of the disease is critical. Thus, therapeutic approaches would be substantially improved by the identification of the molecular mechanisms involved in tumor progression and the key biomarkers capable of improving patients' stratification at diagnosis, by discriminating between those at risk for relapse and those with indolent tumors not requiring further intervention beyond surgery.

The histopathologic and molecular heterogeneity of prostate cancer and the limited availability of human tumor tissue make unraveling the mechanisms of prostate carcinogenesis a challenging task. Our goal was to develop an ex vivo model that could be reliably

Fatty acid synthase (FASN), a key metabolic enzyme for liponeogenesis highly expressed in several human cancers, displays oncogenic properties such as resistance to apoptosis and induction of proliferation when overexpressed. To date, no mechanism has been identified to explain the oncogenicity of FASN in prostate cancer. We generated immortalized prostate epithelial cells (iPrEC) overexpressing FASN, and found that 14C-acetate incorporation into palmitate synthesized de novo by FASN was significantly elevated in immunoprecipitated Wnt-1 when compared to isogenic cells not overexpressing FASN. Overexpression of FASN caused membranous and cytoplasmic β-catenin protein accumulation and activation, while FASN knockdown by short hairpin RNA (shRNA) resulted in a reduction in the extent of β-catenin activation. Orthotopic transplantation of iPrEC cells overexpressing FASN in nude mice resulted in invasive tumors that overexpressed β-catenin. A strong significant association between FASN and cytoplasmic (stabilized) β-catenin immunostaining was found in 862 cases of human prostate cancer after computerized subtraction of the membranous β-catenin signal (P<0.001, Spearman’s rho=0.33). We propose that cytoplasmic stabilization of β-catenin through palmitoylation of Wnt-1 and subsequent activation of the pathway is a potential mechanism of FASN oncogenicity in prostate cancer.