Loss of Krüppel-Like Factor 4 Expression Contributes to Sp1 Overexpression and Human Gastric Cancer Development and Progression

Abstract

Purpose: Increasing evidence indicates that the transcription factor, Sp1, regulates the expression of multiple genes involved in tumor development and progression.We have recently reported that Sp1overexpression is directly correlated with the angiogenic potential of and poor prognosis for human gastric cancer. However, the underlying mechanisms that result in Sp1overexpression remain unclear. Experimental Design:The expression of Sp1and Kru« ppel-like factor 4 (KLF4), a potential tumor suppressor gene, in gastric cancer tissue was analyzed by immunohistochemistry and Western blot analysis. Alterations of Sp1and KLF4 expression were achieved by gene transfer and verified by Northern andWestern blot analyses. Furthermore, Sp1promoter activity assay, electrophoretic mobility shift assay, and chromatin immunoprecipitation assay were done to identify the KLF4 binding sites on the Sp1promoter. Results: Mutually exclusive expression of Sp1and KLF4 was evident in gastric cancer and noncancerous tissue. Specifically, strong Sp1 expression but loss of KLF4 expression was found in cancer tissue, whereas the adjacent noncancerous tissue showed negative Sp1 expression but strong KLF4 expression. Enforced KLF4 expression repressed Sp1 expression at the promoter activity, mRNA, and protein levels. Moreover, a region within the proximal Sp1 promoter was identified to have overlapping KLF4-and Sp1-binding sites, to which KLF4 and Sp1compete for binding. Sp1positively regulated its own promoter, whereas KLF4 did the opposite. Conclusions: Our data suggests that disruption of KLF4-mediated negative regulation contributes to the molecular events of Sp1 overexpression and to the development and progression of human gastric cancer.Although the incidence of gastric cancer declined in the west from the 1940s to the 1980s, it remains a major public health problem throughout the world (1). In Asia and parts of South America in particular, it is the most common epithelial malignancy and is a leading cause of cancer-related death. In fact, gastric cancer remains the fourth most frequently diagnosed malignancy worldwide and is the cause of 12% of all cancer-related deaths annually (1). Advances in the treatment of this disease are likely to come from a fuller understanding of its biology and behavior. Although various genetic and molecular alterations have been found to be associated with the malignant transformation of gastric cancer, they may represent only the pathogenesis of this disease, and they have not been identified as a specific sequence of changes leading to gastric carcinoma (2, 3). Therefore, the role and detailed mechanisms of genetic and epigenetic changes in gastric cancer development and progression remain unclear.Sp1 is a zinc finger transcription factor that is important to the transcription of many cellular and viral genes that contain GC boxes in their promoter. Additional transcription factors that are similar to Sp1 in their structural and transcriptional properties (Sp2, Sp3, and Sp4) have been cloned, th...

Krüppel-like Factor 4 Induces p27Kip1 Expression in and Suppresses the Growth and Metastasis of Human Pancreatic Cancer Cells

“…S5). This result is consistent with our present and previous report (34) and indicates that the effect of KLF4 on gene expression (positive or negative) is specific to the gene promoters.…”

Loss of Epigenetic Kruppel-like Factor 4 Histone Deacetylase (KLF-4-HDAC)-mediated Transcriptional Suppression Is Crucial in Increasing Vascular Endothelial Growth Factor (VEGF) Expression in Breast Cancer

“…In the VEGF promoter, KLF-4 binds to the same region where SAF-1 interacts with the VEGF promoter (9) and thereby suppresses SAF-1 function. In addition to SAF-1, KLF-4 competes with the Sp1 transcription factor and down-regulates Sp1 function (43,46); binding sites for Sp1 have been identified in the (GϩC)-rich proximal promoter region of VEGF (19). Incidentally, Sp1 has been identified to be a positive regulator of VEGF expression in several Our finding of the involvement of HDAC2 and HDAC3 in the regulation of VEGF expression (Fig.…”

“…KLF-4 is shown to play a key role in phenotypic switching and proliferation of vascular smooth muscle cells, where loss of KLF-4 is shown to create a proinflammatory status due to inhibition of repression of basal and cytokine-mediated expression of a diverse set of proinflammatory factors (39,40). KLF-4 exerts a profound anti-inflammatory effect by promoting the expression of several negative cell cycle regulatory genes, including p21 (41), p27, Mdm2, and retinoblastoma, and positive cell cycle regulatory genes, such as cyclin B1 (29), cyclinD1, and ornithine decarboxylase (42), and loss of KLF-4 is seen to contribute to the development and progression of gastric cancer (43) and skin cancer (44). Recently, KLF-4 was found to inhibit tumorigenic progression and metastasis in a mouse model of breast cancer (45).…”

GRP78‐mediated antioxidant response and ABC transporter activity confers chemoresistance to pancreatic cancer cells

“…Multiple studies have underscored the importance of SP1 in malignant tissues (Banerjee et al ., 2013; Deniaud et al ., 2009; Kanai et al ., 2006). Interestingly, it has been reported in colon, gastric, pancreatic, and breast cancers that SP1 is overexpressed, whereas minimal‐to‐no SP1 expression is detected in normal differentiated cells (Banerjee et al ., 2013; Deniaud et al ., 2009; Kanai et al ., 2006). We have recently published that upon downregulation of SP1, transcriptional regulation of GRP78 is adversely affected and cannot recover from chronic ER stress, which leads to cell death (Dauer et al ., 2017).…”