c-Rel and p65 subunits bind to an upstream NF-kappaB site in human granulocyte macrophage-colony stimulating factor promoter involved in phorbol ester response in 5637 cells

The molecular mechanism of NF-κB dysregulation across different subtypes of renal cell carcinoma

BACKGROUND

The nuclear factor kappa B (NF-κB) is a critical pathway that regulates various cellular functions, including immune response, proliferation, growth, and apoptosis. Furthermore, this pathway is tightly regulated to ensure stability in the presence of immunogenic triggers or genotoxic stimuli. The lack of control of the NF-κB pathway can lead to the initiation of different diseases, mainly autoimmune diseases and cancer, including Renal cell carcinoma (RCC). RCC is the most common type of kidney cancer and is characterized by complex genetic composition and elusive molecular mechanisms.

AIM OF REVIEW

The current review summarizes the mechanism of NF-κB dysregulation in different subtypes of RCC and its impact on pathogenesis.

KEY SCIENTIFIC CONCEPT OF REVIEW

This review highlights the prominent role of NF-κB in RCC development and progression by driving the expression of multiple genes and interplaying with different pathways, including the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway. In silico analysis of RCC cohorts and molecular studies have revealed that multiple NF-κB members and target genes are dysregulated. The dysregulation includes receptors such as TLR2, signal-transmitting members including RelA, and target genes, for instance, HIF-1α. The lack of effective regulatory mechanisms results in a constitutively active NF-κB pathway, which promotes cancer growth, migration, and survival. In this review, we comprehensively summarize the role of dysregulated NF-κB-related genes in the most common subtypes of RCC, including clear cell RCC (ccRCC), chromophobe RCC (chRCC), and papillary RCC (PRCC).

NF-κB c-Rel Is Dispensable for the Development but Is Required for the Cytotoxic Function of NK Cells

Natural Killer (NK) cells are cytotoxic lymphocytes critical to the innate immune system. We found that germline deficiency of NF-κB c-Rel results in a marked decrease in cytotoxic function of NK cells, both in vitro and in vivo, with no significant differences in the stages of NK cell development. We found that c-Rel binds to the promoters of perforin and granzyme B, two key proteins required for NK cytotoxicity, and controls their expression. We generated a NK cell specific c-Rel conditional knockout to study NK cell intrinsic role of c- Rel and found that both global and conditional c-Rel deficiency leads to decreased perforin and granzyme B expression and thereby cytotoxic function. We also confirmed the role of c-Rel in perforin and granzyme B expression in human NK cells. c-Rel reconstitution rescued perforin and granzyme B expressions in c-Rel deficient NK cells and restored their cytotoxic function. Our results show a previously unknown role of c-Rel in transcriptional regulation of perforin and granzyme B expressions and control of NK cell cytotoxic function.

Macrophage ubiquitin-specific protease 2 contributes to motility, hyperactivation, capacitation, and in vitro fertilization activity of mouse sperm

Macrophages are innate immune cells that contribute to classical immune functions and tissue homeostasis. Ubiquitin-specific protease 2 (USP2) controls cytokine production in macrophages, but its organ-specific roles are still unknown. In this study, we generated myeloid-selective Usp2 knockout (msUsp2KO) mice and specifically explored the roles of testicular macrophage-derived USP2 in reproduction. The msUsp2KO mice exhibited normal macrophage characteristics in various tissues. In the testis, macrophage Usp2 deficiency negligibly affected testicular macrophage subpopulations, spermatogenesis, and testicular organogenesis. However, frozen-thawed sperm derived from msUsp2KO mice exhibited reduced motility, capacitation, and hyperactivation. In addition, macrophage Usp2 ablation led to a decrease in the sperm population exhibiting high intracellular pH, calcium influx, and mitochondrial membrane potential. Interrupted pronuclei formation in eggs was observed when using frozen-thawed sperm from msUsp2KO mice for in vitro fertilization. Administration of granulocyte macrophage-colony stimulating factor (GM-CSF), whose expression was decreased in testicular macrophages derived from msUsp2KO mice, restored mitochondrial membrane potential and total sperm motility. Our observations demonstrate a distinct role of the deubiquitinating enzyme in organ-specific macrophages that directly affect sperm function.

ETS2 is involved in protein kinase C-activated expression of granulocyte-macrophage colony-stimulating factor in human non-small lung carcinoma cell line, A549

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine expressed in the non-small lung carcinoma cells (NSCLC). However, transcriptional regulation of GM-CSF is not well characterized in NSCLC. In this study we found that two cis-acting ETS family consensus sites are important for transcriptional regulation of GM-CSF in A549 human lung carcinoma cells. These two sites are located separately at around -40 and -100 bp from the transcription start site. Results of transient transfection assays with A549 cells indicated that ETS2 had a strong positive effect on GM-CSF promoter activity. Furthermore, this activity was enhanced by protein kinase C activator, phorbol 12-myristate 13-acetate (PMA), in an ETS consensus-dependent manner, while PMA could also enhance the expression level of ETS2. The protein kinase C inhibitors decreased GM-CSF promoter activity induced by the protein kinase C activator PMA. We also found that antisense ETS2 mRNA decreased PMA-induced GM-CSF promoter activity, supporting the possibility that ETS2 is involved in protein kinase C-induced GM-CSF transcriptional function. Endogenous expression of GM-CSF mRNA was increased by ETS2 transfection and the increased expression was further enhanced by PMA. These data indicate that GM-CSF is up-regulated by ETS2, a target of protein kinase C.

Regulation of granulocyte-macrophage colony-stimulating factor in human retinal pigment epithelial cells by IL-1beta and IFN-gamma

GM-CSF production by RPE cells, which form part of the blood-retina barrier, is upregulated by IL-1beta and this increase can be reversed by IFN-gamma. IL-1beta up-regulation is not dependent on PKC but the PKC activator PMA induces low levels of GM-CSF production and acts synergistically with IL-1beta to further increase GM-CSF. Although A23187 and ionomycin stimulated low levels of GM-CSF production, the IL-1beta pathway was cyclosporin A insensitive and did not interact with the calcium pathway. IL-1beta-stimulated GM-CSF mRNA expression and production was strongly dependent on NF-kappaB. IFN-gamma inhibition of the GM-CSF response to IL-1beta acted via NF-kappaB, reducing the translocation of NF-kappaB to the nuclei of RPE cells treated with IL-1beta and IFN-gamma. The results show that IFN-gamma down-regulation acts either directly on NF-kappaB or its activation or by blockade of a pathway upstream of NF-kappaB. However, any such blockade does not involve PKC or intracellular calcium.

Molecular regulation of granulocyte macrophage colony-stimulating factor in human lung epithelial cells by interleukin (IL)-1beta, IL-4, and IL-13 involves both transcriptional and post-transcriptional mechanisms

Interleukin (IL)-1beta stimulates the release of granulocyte macrophage colony-stimulating factor (GM-CSF) from lung epithelial cells. To investigate the molecular mechanisms underlying GM-CSF regulation, we studied GM-CSF production, messenger RNA (mRNA) expression levels, and GM-CSF promoter activity in A549 human alveolar carcinoma cells stimulated with IL-1beta. Coincubation with IL-4 or IL-13 dose-dependently inhibited IL-1beta-induced GM-CSF release. Time-course studies of intracellular and extracellular protein release and mRNA expression indicated tight coupling of protein and mRNA synthesis within 6 h after stimulation. IL-4 and IL-13 both inhibited expression of GM-CSF mRNA and protein by 2 h after stimulation. Stable transfection of A549 cells, with GM-CSF promoter/ enhancer constructs containing up to 3.3 kb upstream of the transcription start site, revealed maximal activation by IL-1beta and phorbol 12-myristate 13-acetate (PMA) with a reporter containing the proximal promoter (-627 to +35). This excludes sequences further upstream from a major regulatory role in GM-CSF promoter activation by IL-1beta or PMA in these cells. IL-4 and IL-13 downregulated promoter activation but had no effect on GM-CSF mRNA half-life. However, IL-1beta activation of all constructs was far less pronounced than in Jurkat T cells, suggesting a requirement for additional mechanisms, possibly post-transcriptional, to potentiate the observed transcriptional induction.

An upstream negative regulatory element in human granulocyte-macrophage colony-stimulating factor promoter is recognised by AP1 family members

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine involved in haematopoiesis and host defence. Production of GM-CSF has been detected in tumour cells including the U87MG astrocytoma cell line. Previous studies have been focused on the regulatory role of the proximal region of the GM-CSF promoter. Our studies on the distal region of the promoter in U87MG cells identify a negative cis element (-1377/-1298) which contains a AP1-like site able to bind c-jun and c-fos transcription factors, according to the results of DNA/protein binding assays. Mutagenesis of the AP1-like site eliminates AP1 binding and the negative effect on promoter activity.