Ewing sarcoma provides an important model for transcription-factor mediated oncogenic transformation because of its reliance on the ETS-type fusion oncoprotein EWS/FLI. EWS/FLI functions as a transcriptional activator and transcriptional activation is required for its oncogenic activity. Here we demonstrate that a previously less-well characterized transcriptional repressive function of the EWS/FLI fusion is also required for the transformed phenotype of Ewing sarcoma. Through comparison of EWS/FLI transcriptional profiling and genome-wide localization data, we define the complement of EWS/FLI direct downregulated target genes. We demonstrate that LOX is a previously undescribed EWS/FLI-repressed target that inhibits the transformed phenotype of Ewing sarcoma cells. Mechanistic studies demonstrate that the NuRD co-repressor complex interacts with EWS/FLI, and that its associated histone deacetylase and LSD1 activities contribute to the repressive function. Taken together, these data reveal a previously unknown molecular function for EWS/FLI, demonstrate a more highly coordinated oncogenic transcriptional hierarchy mediated by EWS/FLI than previously suspected, and implicate a new paradigm for therapeutic intervention aimed at controlling NuRD activity in Ewing sarcoma tumors.

The phosphatase of regenerating liver (PRL) family of phosphatases, consisting of PRL-1, PRL-2, and PRL-3, represents an intriguing group of proteins being validated as biomarkers and therapeutic targets in cancer. Individual PRLs are overexpressed in a variety of cancer cell lines and tissues when compared with their normal counterparts. More importantly, several recent studies have shown that PRL-3 is expressed at higher levels and at a greater frequency in colorectal cancer metastases compared with primary colorectal tumors and normal colon tissue. Ectopic expression of PRLs in nontumorigenic cells can influence proliferation and the migratory and invasive properties of cells, while knockdown of endogenous PRL-3 or PRL-1 in cancerous cells using small interfering RNA can abrogate cell motility and ability to metastasize in a mouse model. However, the exact biological function and cellular substrates of the PRLs remain unclear. This review will discuss what is known about the PRLs, what makes the PRLs possible attractive targets for therapeutic intervention, and the possible future directions in PRL biology and inhibitor identification. [Mol Cancer Ther 2005;4(11):1653 -61]

Lysine specific demethylase 1 (LSD1) plays an important role in regulating histone lysine methylation at residues K4 and K9 on histone H3 and is an attractive therapeutic target in multiple malignancies. Here we report a structure-based virtual screen of a compound library containing ∼2 million small molecular entities. Computational docking and scoring followed by biochemical screening led to the identification of a novel N'-(1-phenylethylidene)-benzohydrazide series of LSD1 inhibitors with hits showing biochemical IC50s in the 200-400 nM range. Hit-to-lead optimization and structure-activity relationship studies aided in the discovery of compound 12, with a Ki of 31 nM. Compound 12 is reversible and specific for LSD1 as compared to the monoamine oxidases shows minimal inhibition of CYPs and hERG and inhibits proliferation and survival in several cancer cell lines, including breast and colorectal cancer. Compound 12 may be used to probe LSD1's biological role in these cancers.

Purpose: The targeting protein for Xklp2 (TPX2) has recently gained attention as a putative oncogene possibly amplified in several human malignancies, including pancreatic adenocarcinoma. In this work, we sought to evaluate the copy number and expression of TPX2 in pancreatic cancer cell lines and tumor tissues and to further explore the potential of TPX2 as a therapeutic target. Experimental Design: The DNA copy number and expression of the TPX2 gene were surveyed in pancreatic cancer cell lines and tumor tissues and compared with those of immortalized normal pancreatic ductal cells and normal pancreatic tissues. The cellular effects of TPX2 knockdown using small interfering RNA oligonucleotides in pancreatic cancer cells, such as growth in tissue culture, in soft agar, and in nude mice; apoptosis; and sensitivity to paclitaxel, were also investigated using various assays. Results: Low-copy-number TPX2 amplification was found in pancreatic cancer cell lines and low-passage pancreatic cancer tumor xenografts. TPX2 expression was upregulated in pancreatic cancer cell lines at both the mRNA and protein levels relative to the immortalized pancreatic ductal epithelial cell line HPDE6. Immunohistochemical staining of a tissue microarray showed that TPX2 expression was higher in pancreatic tumors compared with their normal counterparts. Treatment with TPX2 targeting small interfering RNAs effectively reduced pancreatic cancer cell growth in tissue culture, induced apoptosis, and inhibited growth in soft agar and in nude mice. Knockdown of TPX2 also sensitized pancreatic cancer cells to paclitaxel treatment. Conclusions: Our results suggest that TPX2 might be an attractive target for pancreatic cancer therapy. (Clin Cancer Res 2009;15(21):6519-28) Pancreatic ductal adenocarcinoma (PDAC), with a 5-year survival rate of ∼5% for all stages combined in the United States, is among the most lethal of human cancers. In fact, the number of people estimated to die of pancreatic cancer (34,290 for 2008 in the United States) nearly matches the estimated number of individuals (37,680) who will be diagnosed with it (1). Currently, surgical resection is the only therapy that is considered to offer a cure; however, pancreatic adenocarcinoma is typically diagnosed as advanced inoperable disease characterized by resistance to current therapeutics. Therefore, new treatments as well as a better understanding of pancreatic cancer biology are urgently needed.Genomic instability is thought to drive cancer, as regions with gains often harbor oncogenes and regions with losses commonly harbor tumor suppressor genes. PDAC harbors complicated aberrations of chromosomal alleles, with numerous specific gains and losses reported (2-5). Chromosomal gains of 20q are found in various types of adenocarcinoma and are also prominent in pancreatic cancer (6). Recently, TPX2 was identified as a candidate oncogene from the amplicon on 20q11.2 showing copy number-driven overexpression in non-small-cell lung cancer and PDAC (7,8). However, the fre...