Role of Sp Proteins in Regulation of Vascular Endothelial Growth Factor Expression and Proliferation of Pancreatic Cancer Cells

Abstract

Sp proteins play an important role in angiogenesis and growth of cancer cells, and specificity protein 1 (Sp1) has been linked to vascular endothelial growth factor (VEGF) expression in pancreatic cancer cells. RNA interference was used to investigate the role of Sp family proteins on regulation of VEGF expression and proliferation of Panc-1 pancreatic cancer cells. Using a series of constructs containing VEGF promoter inserts, it was initially shown that Sp1 and Sp3 were required for transactivation, and this was primarily dependent on proximal GC-rich motifs. We also showed that Sp4 was expressed in Panc-1 cells, and RNA interference assays suggested that Sp4 cooperatively interacted with Sp1 and Sp3 to activate VEGF promoter constructs in these cells. However, the relative contributions of Sp proteins to VEGF expression were variable among different pancreatic cancer cell lines. Small inhibitory RNAs for Sp3, but not Sp1 or Sp4, inhibited phosphorylation of retinoblastoma protein, blocked G 0 /G 1 3 S-phase progression, and up-regulated p27 protein/promoter activity of Panc-1 cells; similar results were observed in other pancreatic cancer cells, suggesting that Sp3-dependent growth of pancreatic cancer cells is caused by inhibition of p27 expression.

Mechanism of Metformin-dependent Inhibition of Mammalian Target of Rapamycin (mTOR) and Ras Activity in Pancreatic Cancer

“…Moreover, knockdown of Sp1 in pancreatic cancer cells decreases growth and invasion and induces apoptosis, confirming the pro-oncogenic functions of this factor (49). These results suggest that drugs such as metformin and other agents (31)(32)(33)(34)(35)(36)39) that target Sp1, Sp3, and Sp4 represent a class of new mechanism-based drugs that can be used in combination therapies for treating this deadly disease.…”

“…This involved down-regulation of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and pro-oncogenic Sp-regulated genes such as bcl2, fatty acid synthase (FAS), survivin, vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1) (31). The anticancer activities of metformin are also similar to * This work was supported, in whole or in part, by National Institutes of Health that observed after knockdown of Sp1 or all three Sp proteins by RNA interference in cancer cells, and this includes growth inhibition, induction of apoptosis, reversal of epithelial to mesenchymal transition, and decreased migration/invasion (32)(33)(34)(35)(36). Metformin also inhibits NFB and decreases cyclin D1 and ErbB2 in cancer cell lines (13,20,27,28), and these gene products are also decreased after Sp1, Sp3, and Sp4 silencing by RNAi or by other drugs that down-regulate Sp proteins (32)(33)(34)(35)(36).…”

miR-125a-5p upregulation suppresses the proliferation and induces the cell apoptosis of lung adenocarcinoma by targeting NEDD9

“…These miRNAs regulate gene expression by targeting the 3' untranslated regions (3'UTRs) of mRNAs (1)(2)(3)(4)(5)(6). Numerous studies have shown that miRNAs act as intrinsic regulators of many cellular processes, including cell proliferation, apoptosis, invasion and differentiation (7)(8)(9)(10)(11)(12).…”

<i>ADRBD1</i> (GRK2), <i>TBXA2R</i> and <i>VEGFA</i> rSNPs in KLF4 and SP1 TFBS Exhibit Linkage Disequilibrium

“…Consequently, an evaluation was made within the ADRBK1 [9], TBXA2R [10] [11] and VEGFA [12] genes for the rSNPs in LD [26] and their effect on potential KLF/SP TFBS (Table). Since it has been shown that KLF4 and SP1 physically interact, occupy the angiotensin II type 1 receptor (AT1R) promoter and induce AT1R transcription in VSMCs in a co-operative manner under basal conditions [8], the evaluation was based on these two TFs.…”

“…KLF4 and SP1 also have transcriptional factor binding sites (TFBS) in the regulatory regions of the adrenergic receptor kinase 1 (ADRBK1), thromboxane A2 receptor (TBXA2R) and vascular endothelial growth factor (VEGFA) genes. The SP1 TF has been shown to bind its transcriptional factor binding site (TFBS) and regulate the ADRBK1 [9], TBXA2R [10] [11] and VEGFA [12] genes. The ADRBK1 gene (also known as GRK2) is encoded on chromosome 11 and is expressed as a ubiquitous cytosolic enzyme that specifically phosphorylates the activated form of the beta-adrenergic and related G-protein-coupled receptors.…”