SND1, a subunit of the miRNA regulatory complex RISC, has been implicated as an oncogene in hepatocellular carcinoma (HCC). In this study, we show that hepatocyte-specific SND1 transgenic mice (Alb/SND1 mice) develop spontaneous HCC with partial penetrance and exhibit more highly aggressive HCC induced by chemical carcinogenesis. Livers from Alb/SND1 mice exhibited a relative increase in inflammatory markers and spheroid-generating tumor initiating cells (TIC). Mechanistic investigations defined roles for Akt and NF-κB signaling pathways in promoting TIC formation in Alb/SND1 mice. In human xenograft models of subcutaneous or orthotopic HCC, administration of the selective SND1 inhibitor 3′, 5′-deoxythymidine bisphosphate (pdTp) inhibited tumor formation without effects on body weight or liver function. Our work establishes an oncogenic role for SND1 in promoting TIC formation, and highlights pdTp as a highly selective SND1 inhibitor as a candidate therapeutic lead to treat advanced HCC.
The staphylococcal nuclease and tudor domain containing 1 (SND1) is a multifunctional protein overexpressed in breast, prostate, colorectal and hepatocellular carcinomas and malignant glioma. Molecular studies have revealed the multifaceted activities of SND1 involved in regulating gene expression at transcriptional as well as post-transcriptional levels. Early studies identified SND1 as a transcriptional co-activator. SND1 is also a component of RNA-induced silencing complex (RISC) thus mediating RNAi function, a regulator of mRNA splicing, editing and stability, and plays a role in maintenance of cell viability. Such diverse actions allow the SND1 to modulate a complex array of molecular networks, thereby promoting carcinogenesis. Here, we describe the crucial role of SND1 in cancer development and progression, and highlight SND1 as a potential target for therapeutic intervention.
Nonalcoholic steatohepatitis (NASH) is the most prevalent cause of chronic liver disease in the Western world. However, an optimum therapy for NASH is yet to be established mandating more in-depth investigation into the molecular pathogenesis of NASH to identify novel regulatory molecules and develop targeted therapies. Here, we unravel a unique function of Astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) in NASH using a transgenic mouse with hepatocyte-specific overexpression of AEG-1 (Alb/AEG-1) and a conditional hepatocyte-specific AEG-1 knockout mouse (AEG-1ΔHEP). Alb/AEG-1 mice developed spontaneous NASH while AEG-1ΔHEP mice were protected from high fat diet (HFD)-induced NASH. Intriguingly, AEG-1 overexpression was observed in livers of NASH patients and WT mice that developed steatosis upon feeding high fat diet. In-depth molecular analysis unraveled that inhibition of PPARα activity resulting in decreased fatty acid β-oxidation, augmentation of translation of fatty acid synthase resulting in de novo lipogenesis, and increased NF-κB-mediated inflammation act in concert to mediate AEG-1-induced NASH. Therapeutically, hepatocyte-specific nanoparticle-delivered AEG-1 siRNA provided marked protection from HFD-induced NASH in wild-type mice. Conclusion AEG-1 might be a key molecule regulating initiation and progression of NASH. AEG-1 inhibitory strategies might be developed as a potential therapeutic intervention in NASH patients.
The cell of origin of colon cancer is typically thought to be the resident somatic stem cells, which are immortal and escape the continual cellular turnover characteristic of the intestinal epithelium. However, recent studies have identified certain conditions in which differentiated cells can acquire stem-like properties and give rise to tumors. Defining the origins of tumors will inform cancer prevention efforts as well as cancer therapies, as cancers with distinct origins often respond differently to treatments. We report here a new condition in which tumors arise from the differentiated intestinal epithelium. Inactivation of the differentiation-promoting transcription factor SMAD4 in the intestinal epithelium was surprisingly well tolerated in the short term. However, after several months, adenomas developed with characteristics of activated WNT signaling. Simultaneous loss of SMAD4 and activation of the WNT pathway led to dedifferentiation and rapid adenoma formation in differentiated tissue. Transcriptional profiling revealed acquisition of stem cell characteristics, and colabeling indicated that cells expressing differentiated enterocyte markers entered the cell cycle and reexpressed stem cell genes upon simultaneous loss of SMAD4 and activation of the WNT pathway. These results indicate that SMAD4 functions to maintain differentiated enterocytes in the presence of oncogenic WNT signaling, thus preventing dedifferentiation and tumor formation in the differentiated intestinal epithelium. This work identifies a mechanism through which differentiated cells prevent tumor formation by suppressing oncogenic plasticity. .
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