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Thyroid transcription factor‐1 (TTF‐1, encoded by the NKX2‐1 gene) is highly expressed in small‐cell lung carcinoma (SCLC) and lung adenocarcinoma (LADC), but how its functional roles differ between SCLC and LADC remains to be elucidated. Here, we compared the genome‐wide distributions of TTF‐1 binding regions and the transcriptional programs regulated by TTF‐1 between NCI‐H209 (H209), a human SCLC cell line, and NCI‐H441 (H441), a human LADC cell line, using chromatin immunoprecipitation‐sequencing (ChIP‐seq) and RNA‐sequencing (RNA‐seq). TTF‐1 binding regions in H209 and H441 cells differed by 75.0% and E‐box motifs were highly enriched exclusively in the TTF‐1 binding regions of H209 cells. Transcriptome profiling revealed that TTF‐1 is involved in neuroendocrine differentiation in H209 cells. We report that TTF‐1 and achaete‐scute homolog 1 (ASCL1, also known as ASH1, an E‐box binding basic helix–loop–helix transcription factor, and a lineage‐survival oncogene of SCLC) are coexpressed and bound to adjacent sites on target genes expressed in SCLC, and cooperatively regulate transcription. Furthermore, TTF‐1 regulated expression of the Bcl‐2 gene family and showed antiapoptotic function in SCLC. Our findings suggest that TTF‐1 promotes SCLC growth and contributes to neuroendocrine and antiapoptotic gene expression by partly coordinating with ASCL1. [ABSTRACT FROM AUTHOR]

The tumor microenvironment contains various components, including cancer cells, tumor vessels, and cancer‐associated fibroblasts, the latter of which are comprised of tumor‐promoting myofibroblasts and tumor‐suppressing fibroblasts. Multiple lines of evidence indicate that transforming growth factor‐β (TGF‐β) induces the formation of myofibroblasts and other types of mesenchymal (non‐myofibroblastic) cells from endothelial cells. Recent reports show that fibroblast growth factor 2 (FGF2) modulates TGF‐β‐induced mesenchymal transition of endothelial cells, but the molecular mechanisms behind the signals that control transcriptional networks during the formation of different groups of fibroblasts remain largely unclear. Here, we studied the roles of FGF2 during the regulation of TGF‐β‐induced mesenchymal transition of tumor endothelial cells (TECs). We demonstrated that auto/paracrine FGF signals in TECs inhibit TGF‐β‐induced endothelial‐to‐myofibroblast transition (End‐MyoT), leading to suppressed formation of contractile myofibroblast cells, but on the other hand can also collaborate with TGF‐β in promoting the formation of active fibroblastic cells which have migratory and proliferative properties. FGF2 modulated TGF‐β‐induced formation of myofibroblastic and non‐myofibroblastic cells from TECs via transcriptional regulation of various mesenchymal markers and growth factors. Furthermore, we observed that TECs treated with TGF‐β were more competent in promoting in vivo tumor growth than TECs treated with TGF‐β and FGF2. Mechanistically, we showed that Elk1 mediated FGF2‐induced inhibition of End‐MyoT via inhibition of TGF‐β‐induced transcriptional activation of α‐smooth muscle actin promoter by myocardin‐related transcription factor‐A. Our data suggest that TGF‐β and FGF2 oppose and cooperate with each other during the formation of myofibroblastic and non‐myofibroblastic cells from TECs, which in turn determines the characteristics of mesenchymal cells in the tumor microenvironment. [ABSTRACT FROM AUTHOR]

Clinical development of anti-angiogenic agents has been a major landmark in cancer therapy for several types of cancers. Signals mediated by both vascular endothelial growth factor ( VEGF) and bone morphogenetic protein ( BMP)-9 and 10 have been implicated in tumor angiogenesis. However, previous studies have shown that targeting the individual signals was not sufficiently effective in retarding tumor growth in certain preclinical and clinical conditions. In the present study, we developed a novel decoy chimeric receptor that traps both VEGF and BMP-9/10. Single targeting of either VEGF or BMP-9/10 signals significantly reduced the formation of tumor vessels in a mouse xenograft model of human pancreatic cancer; however, it did not show significant therapeutic effects on tumor growth. In contrast, dual targeting of the angiogenic signals resulted in more significant inhibition of tumor angiogenesis, leading to delay of tumor growth. Our findings suggest that simultaneous blockade of VEGF and BMP-9/10 signals is a promising therapeutic strategy for the cancers that are resistant to anti- VEGF and BMP-9/10 therapies. [ABSTRACT FROM AUTHOR]

Transforming growth factor-β ( TGF-β) plays central roles in endothelial-mesenchymal transition (End MT) involved in development and pathogenesis. Although End MT and epithelial-mesenchymal transition are similar processes, roles of micro RNAs in End MT are largely unknown. Here, we report that constitutively active micro RNA-31 (miR-31) is a positive regulator of TGF-β-induced End MT. Although the expression is not induced by TGF-β, miR-31 is required for induction of mesenchymal genes including α- SMA, actin reorganization and MRTF-A activation during End MT. We identified VAV3, a regulator of actin remodeling and MRTF-A activity, as a miR-31 target. Global transcriptome analysis further showed that miR-31 positively regulates End MT-associated unique secretory phenotype (End MT- SP) characterized by induction of multiple inflammatory chemokines and cytokines including CCL17, CX3 CL1, CXCL16, IL-6 and Angptl2. As a mechanism for this phenomenon, TGF-β and miR-31 suppress Stk40, a negative regulator of NF-κB pathway. Interestingly, TGF-β induces alternative polyadenylation ( APA)-coupled miR-31-dependent Stk40 suppression without concomitant miR-31 induction, and APA-mediated exclusion of internal poly(A) sequence in Stk40 3′ UTR enhances target efficiency of Stk40. Finally, miR-31 functions as a molecular hub to integrate TGF-β and TNF-α signaling to enhance End MT. These data confirm that constitutively active micro RNAs, as well as inducible micro RNAs, serve as phenotypic modifiers interconnected with transcriptome dynamics during End MT. [ABSTRACT FROM AUTHOR]

The precise control of micro RNA (mi RNA) biosynthesis is crucial for gene regulation. Lin28A and Lin28B are selective inhibitors of biogenesis of let-7 miRNAs involved in development and tumorigenesis. Lin28A selectively inhibits let-7 biogenesis through cytoplasmic uridylation of precursor let-7 by TUT4 terminal uridyl transferase and subsequent degradation by Dis3l2 exonuclease. However, a role of this uridylation pathway remains unclear in let-7 blockade by Lin28B, a paralog of Lin28A, while Lin28B is reported to engage a distinct mechanism in the nucleus to suppress let-7. Here we revisit a functional link between Lin28B and the uridylation pathway with a focus on let-7 metabolism in cancer cells. Both Lin28A and Lin28B interacted with Dis3l2 in the cytoplasm, and silencing of Dis3l2 upregulated uridylated pre-let-7 in both Lin28A- and Lin28B-expressing cancer cell lines. In addition, we found that amounts of let-7 precursors influenced intracellular localization of Lin28B. Furthermore, we found that MCPIP1 (Zc3h12a) ribonuclease was also involved in degradation of both non-uridylated and uridylated pre-let-7. Cancer transcriptome analysis showed association of expression levels of Lin28B and uridylation pathway components, TUT4 and Dis3l2, in various human cancer cells and hepatocellular carcinoma. Collectively, these results suggest that cytoplasmic uridylation pathway actively participates in blockade of let-7 biogenesis by Lin28B. [ABSTRACT FROM AUTHOR]

Asymmetric selection of single-stranded guide RNAs from double-stranded RNA precursors is crucial in RNA silencing-mediated gene regulation. However, the precise mechanisms of small-RNA asymmetry are unclear, especially because asymmetric selection can still occur when the putative asymmetry sensors Drosophila R2D2 and mammalian Dicer are depleted. Here we report a direct contribution of mammalian Argonaute 2 (Ago2) to microRNA (miRNA) asymmetry. Ago2 selects strands with 5′-uridine or 5′-adenosine and thermodynamically unstable 5′ ends in parallel through its two sensor regions, which contact the 5′ nucleobases and 5′-phosphates of prospective guide strands. Hence, miRNA asymmetry shows superposed patterns reflecting 5′-end nucleotide identity ('digital' pattern) and thermodynamic stability ('analog' pattern). Furthermore, we demonstrate that cancer-associated miRNA variations reprogram asymmetric selection. Finally, our study presents a model of this universal principle, to aid in comprehensive understanding of miRNA function and development of new RNA-silencing therapies in precision medicine. [ABSTRACT FROM AUTHOR]