Pre-B-cell leukemia homeobox-1 (PBX1), a transcriptional factor and downstream effector of Notch signaling pathway, plays pivotal roles in a wide spectrum of tumors, as well as developmental, inflammatory, autoimmune, and neurodegenerative disorders. Exploiting the crystal structure of the Pbx1-DNA complex, we developed a novel small-molecular inhibitor T417 that can directly block Pbx1-binding to DNA, unlike other existing compounds that interfere with protein-protein interactions. When T417 docks into the hydrophobic pocket of Pbx1 protein, the small molecule can dampen PBX1 transcription activity by hindering its binding to the promoter regions of PBX1 downstream target genes. Intriguingly, the amount of PBX1 expression in cells can dictate its response to T417. Increment of PBX1 expression is found in the high-grade serous carcinoma (HGSC) and carboplatin-resistant (CR) cells, and its expression is generally low in normal tissues as compared to the transformed tissues, making it such an arguably unique therapeutic target in ovarian cancer cells. This expression pattern illustrates the very minimal toxicity of T417 on normal tissues and organs in animal models, while it imposed in vitro and in vivo detrimental effects toward HGSC and CR cells. Besides, T417 holds synergistic cytotoxic effects with DNA damage-related drugs including PARP inhibitor and platinum-based drug. As PBX1 was shown to participate in maintaining cancer stem cell (CSC)-like phenotypes and promoting resistance to antitumor drugs, T417 is able to hammer out the stemness traits of CR cells to revert to a differentiated status through tacking PBX1 signaling cascade. The novel PBX1-targeting compound selectively interferes with PBX1-binding to DNA, which potentially points to powerful therapeutics and broad applications for the treatment of different human malignancies and stem cell therapy. Citation Format: Yao-An Shen, Jin Jung, Yohan Suryo Rahmanto, Licia Selleri, Ie-Ming Shih, Chi-Mu Chuang, Tian-Li Wang. A novel small-molecule compound targeting PBX1-DNA interaction impedes cancer cell survival and carboplatin resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1966.
Cancer stem cells (CSCs) are a rare subset cancer cells with self-renewal property and cause many difficulties in clinical treatment. CSCs have been found in different tumors by specific surface markers. However, the surface marker of CSC remains unknown in various cancer types, including in nasopharyngeal carcinoma (NPC). Here, we took advantage of CSC's properties, such as chemoresistance, radioresistance, and the ability to form tumor spheres, to isolate CSCs from NPC cell lines. Combining these three isolation methods, and surface marker screening, we identified that NPC CSCs had high level of CD44 and CD24 surface antigen expression. We then validated the CD44/CD24 high positive as NPC CSC surface marker. In cell proliferation assay by MTT test, tumorigenity assay in soft agar and in vivo xenotransplantation, and radioresistant assay, CD44/CD24 high positive cells expressed significant CSC properties compared with CD44/CD24 double negative and parental NPC cells. We further found that CSCs underwent mitochondria resetting, including the distribution, quantity, and quality of mitochondria. Metabolic shift that largely relied on glycolysis also occured in CSCs. They predominately ultilized glycolysis instead of mitochondrial respiration to meet energy demand. Inhibiting glycolysis or treating antioxidants suppresses the viability and malignant traits of CSCs which provides therapeutic implication in NPC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 482. doi:10.1158/1538-7445.AM2011-482
Understanding the biological and clinical impact of copy number aberrations (CNA) in cancer remains an unmet challenge. Genetic amplification of chromosome 1q (chr1q-amp) is a major CNA conferring adverse prognosis in several cancers, including the blood cancer, multiple myeloma (MM). Although several chr1q genes portend high-risk MM disease, the underpinning molecular aetiology remains elusive. Here we integrate patient multi-omics datasets with genetic variables to identify 103 adverse prognosis genes in chr1q-amp MM. Amongst these, the transcription factor PBX1 is ectopically expressed by genetic amplification and epigenetic activation of its own preserved 3D regulatory domain. By binding to reprogrammed super-enhancers, PBX1 directly regulates critical oncogenic pathways, whilst in co-operation with FOXM1, activates a proliferative gene signature which predicts adverse prognosis across multiple cancers. Notably, pharmacological disruption of the PBX1-FOXM1 axis, including with a novel PBX1 inhibitor is selectively toxic against chr1q-amp cancer cells. Overall, our systems medicine approach successfully identifies CNA-driven oncogenic circuitries, links them to clinical phenotypes and proposes novel CNA-targeted therapy strategies in cancer.SignificanceWe provide a comprehensive systems medicine strategy to unveil oncogenic circuitries and inform novel precision therapy decisions against CNA in cancer. This first clinical multi-omic analysis of chr1q-amp in MM identifies a central PBX1-FOXM1 regulatory axis driving high-risk prognosis, as a novel therapeutic target against chr1q-amp in cancer.
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