Induction of cPLA2 in Lung Epithelial Cells and Non-small Cell Lung Cancer Is Mediated by Sp1 and c-Jun

Abstract

Activating mutations in ras genes are frequently associated with non-small cell lung cancer cells (NSCLC) and contribute to transformed growth in these cells. Expression of oncogenic forms of Ras in these cells is associated with increased expression and activity of cytosolic phospholipase A 2 (cPLA 2 ) and cyclooxygenase-2 (COX-2), leading to constitutively elevated levels of prostaglandin production. Expression of oncogenic Ras is sufficient to induce these enzymes in normal lung epithelial cells. We have previously reported that the JNK and ERK pathways are necessary for induction of cPLA 2 and have defined a minimal region of the cPLA 2 promoter from ؊58 to ؊12 that is required for Ha-Ras-mediated induction. To further characterize the cis-regulatory elements within this region involved in this response, site-directed mutagenesis was used to make mutations at various sites. Three cis-regulatory elements were identified: regions ؊21/؊18, ؊37/؊30, and ؊55/؊53. Mutations in any of these elements decreased basal and Ha-Ras-induced cPLA 2 promoter activity in both normal lung epithelial cells, as well as steady state promoter activity in A549 cells, with a mutation in element ؊21/؊18 completely eliminating all promoter activity. Overexpression studies and gel shift assays indicated that Sp1 may serve as a transcription factor functionally regulating promoter activity by directly interacting with two of the cis-regulatory elements, ؊21/؊18 and ؊37/؊30. Expression of Ha-Ras led to induction of c-Jun protein, which showed functional cooperation with Sp1 in driving promoter activity. Additional unidentified transcription factors bound to the regions from ؊55/؊53 and ؊37/؊34.

c-Jun and the dominant-negative mutant, TAM67, induce vimentin gene expression by interacting with the activator Sp1

“…Here, it would appear that removal of approximately 1/3 of the NH-terminus of c-Jun including the phosphorylation sites for JNK has created a molecule that functions better in coactivating Sp1. Interestingly, cPLA2 gene expression was also enhanced by either cJun or v-Jun, which lacks the JNK docking domain (Blaine et al, 2001). From these studies, it was suggested that the increased expression of c-Jun may be more important than direct phosphorylation of the protein.…”

“…To date, the interaction of c-Jun and Sp1 has been found to be important in the regulation of the lipoxygenase (Chen and Chang, 2000), p21 (Kardassis et al, 1999;Wang et al, 2000), cPLA 2 (Blaine et al, 2001), and neuronal nicotinic acetylcholine receptor (Melnikova and Gardner, 2001) genes. For p21, this (Kardassis et al, 1999) or repressed (Wang et al, 2000) gene expression in different cell types, suggesting that a c-Jun/Sp1 interaction might be promoter-specific and does not always confer activation.…”

Identification of differentially expressed genes in clear cell renal cell carcinoma by analysis of full-length enriched cDNA library

“…It has been reported that metabolism genes, for example proline oxidase [28,29] and cytosolic phospholipase A2 [30,31], were differentially expressed in tumor cells and might have a role in carcinogenesis. Many metabolism genes with abnormal expression in ccRCC tissues, including ASS, were identified by our investigation.…”

Bradykinin B2 Receptor Mediates NF-κB Activation and Cyclooxygenase-2 Expression via the Ras/Raf-1/ERK Pathway in Human Airway Epithelial Cells

“…The classic Ras-mediated pathway involves the binding of Raf-1 and subsequent phosphorylation of Raf-1 at Ser 338 by many kinases (24,25), which in turn activates ERKs (26), and consequently phosphorylates many target proteins including transcription factors and protein kinases (27). A role for Ras in COX-2 induction has been implied in many cell types (21,23). However, the role of the Ras/ Raf-1/ERK pathway in BK-induced COX-2 expression has not been investigated in human airway epithelial cells (A549).…”

“…Ras has been found to couple with multiple effector systems to activate distinct physiological and pathological responses such as cell proliferation and proinflammatory mediator release (22,23). An important class of Ras effectors is the MAPK family.…”