Bridging the Gap: A Regulator of NF-κB Linking Inflammation and Cancer

κB-Ras proteins are fast-exchanging GTPases and function via nucleotide-independent binding of Ral GTPase-activating protein complexes

κB-Ras (NF-κB inhibitor-interacting Ras-like protein) GTPases are small Ras-like GTPases but harbor interesting differences in important sequence motifs. They act in a tumor-suppressive manner as negative regulators of Ral (Ras-like) GTPase and NF-κB signaling, but little is known about their mode of function. Here, we demonstrate that, in contrast to predictions based on primary structure, κB-Ras GTPases possess hydrolytic activity. Combined with low nucleotide affinity, this renders them fast-cycling GTPases that are predominantly GTP-bound in cells. We characterize the impact of κB-Ras mutations occurring in tumors and demonstrate that nucleotide binding affects κB-Ras stability but is not strictly required for RalGAP (Ral GTPase-activating protein) binding. This demonstrates that κB-Ras control of RalGAP/Ral signaling occurs in a nucleotide-binding- and switch-independent fashion.

A pan-cancer analysis implicates human NKIRAS1 as a tumor-suppressor gene

The NF-κB family of transcription factors and the Ras family of small GTPases are important mediators of proproliferative signaling that drives tumorigenesis and carcinogenesis. The κB-Ras proteins were previously shown to inhibit both NF-κB and Ras activation through independent mechanisms, implicating them as tumor suppressors with potentially broad relevance to human cancers. In this study, we have used two mouse models to establish the relevance of the κB-Ras proteins for tumorigenesis. Additionally, we have utilized a pan-cancer bioinformatics analysis to explore the role of the κB-Ras proteins in human cancers. Surprisingly, we find that the genes encoding κB-Ras 1 (NKIRAS1) and κB-Ras 2 (NKIRAS2) are rarely down-regulated in tumor samples with oncogenic Ras mutations. Reduced expression of human NKIRAS1 alone is associated with worse prognosis in at least four cancer types and linked to a network of genes implicated in tumorigenesis. Our findings provide direct evidence that loss of NKIRAS1 in human tumors that do not carry oncogenic RAS mutations is associated with worse clinical outcomes.

NFκB (RelA) mediates transactivation of hnRNPD in oral cancer cells

Heterogeneous Ribonucleoprotein D (hnRNPD) is an RNA binding protein involved in post-transcriptional regulation of multiple mediators of carcinogenesis. We previously demonstrated a strong association of hnRNPD over expression with poor outcome in Oral Squamous Cell Carcinoma (OSCC). However, hitherto the precise molecular mechanism of its overexpression in oral cancer was not clear. Therefore, in an attempt to elucidate the transcriptional regulation of hnRNPD expression, we cloned 1406 bp of 5ʹ flanking region of human hnRNPD gene along with 257 bp of its first exon upstream to promoterless luciferase reporter gene in pGL3-Basic. Transfection of the resulting construct in SCC-4 cells yielded 1271 fold higher luciferase activity over parent vector. By promoter deletion analysis, we identified a canonical TATA box containing 126 bp core promoter region that retained ~ 58% activity of the full length promoter. In silico analysis revealed the presence of four putative NFκB binding motifs in the promoter. Sequential deletion of these motifs from the full-length promoter reporter construct coupled with luciferase assays revealed an 82% decrease in promoter activity after deletion of the first (−1358/−1347) motif and 99% reduction after the deletion of second motif (−1052/−1041). In-vivo binding of NFκB (RelA) to these two motifs in SCC-4 cells was confirmed by ChIP assays. Site directed mutagenesis of even one of these two motifs completely abolished promoter activity, while mutagenesis of the remaining two motifs had marginal effect on the same. Consistent with these findings, treatment of SCC-4 cells with PDTC, a known inhibitor of NFκB dramatically reduced the levels hnRNPD mRNA and protein. Finally, the expression of hnRNPD and NFκB in clinical specimen from 37 oral cancer patients was assessed and subjected to Spearmen’s Correlation analysis which revealed a strong positive correlation between the two. Thus, results of the present study for the first time convincingly demonstrate NFκB (RelA) mediated transcriptional upregulation of hnRNPD expression in oral cancer.

Inflammatory Mediators in Oral Cancer: Pathogenic Mechanisms and Diagnostic Potential

Approximately 15% of cancers are attributable to the inflammatory process, and growing evidence supports an association between oral squamous cell carcinoma (OSCC) and chronic inflammation. Different oral inflammatory conditions, such as oral lichen planus (OLP), submucous fibrosis, and oral discoid lupus, are all predisposing for the development of OSCC. The microenvironment of these conditions contains various transcription factors and inflammatory mediators with the ability to induce proliferation, epithelial-to-mesenchymal transition (EMT), and invasion of genetically predisposed lesions, thereby promoting tumor development. In this review, we will focus on the main inflammatory molecules and transcription factors activated in OSCC, with emphasis on their translational potential.

SPINK7 expression changes accompanied by HER2, P53 and RB1 can be relevant in predicting oral squamous cell carcinoma at a molecular level

The oral squamous cell carcinoma (OSCC), which has a high morbidity rate, affects patients worldwide. Changes in SPINK7 in precancerous lesions could promote oncogenesis. Our aim was to evaluate SPINK7 as a potential molecular biomarker which predicts OSCC stages, compared to: HER2, TP53, RB1, NFKB and CYP4B1. This study used oral biopsies from three patient groups: dysplasia (n = 33), less invasive (n = 28) and highly invasive OSCC (n = 18). The control group consisted of clinically suspicious cases later to be confirmed as normal mucosa (n = 20). Gene levels of SPINK7, P53, RB, NFKB and CYP4B1 were quantified by qPCR. SPINK7 levels were correlated with a cohort of 330 patients from the TCGA. Also, SPINK7, HER2, TP53, and RB1, were evaluated by immunohistofluorescence. One-way Kruskal–Wallis test and Dunn's post-hoc with a p < 0.05 significance was used to analyze data. In OSCC, the SPINK7 expression had down regulated while P53, RB, NFKB and CYP4B1 had up regulated (p < 0.001). SPINK7 had also diminished in TCGA patients (p = 2.10e-6). In less invasive OSCC, SPINK7 and HER2 proteins had decreased while TP53 and RB1 had increased with respect to the other groups (p < 0.05). The changes of SPINK7 accompanied by HER2, P53 and RB1 can be used to classify the molecular stage of OSCC lesions allowing a diagnosis at molecular and histopathological levels.

The RAL signaling network: Cancer and beyond

The RAL proteins RALA and RALB belong to the superfamily of small RAS-like GTPases (guanosine triphosphatases). RAL GTPases function as molecular switches in cells by cycling through GDP- and GTP-bound states, a process which is regulated by several guanine exchange factors (GEFs) and two heterodimeric GTPase activating proteins (GAPs). Since their discovery in the 1980s, RALA and RALB have been established to exert isoform-specific functions in central cellular processes such as exocytosis, endocytosis, actin organization and gene expression. Consequently, it is not surprising that an increasing number of physiological functions are discovered to be controlled by RAL, including neuronal plasticity, immune response, and glucose and lipid homeostasis. The critical importance of RAL GTPases for oncogenic RAS-driven cellular transformation and tumorigenesis still attracts most research interest. Here, RAL proteins are key drivers of cell migration, metastasis, anchorage-independent proliferation, and survival. This chapter provides an overview of normal and pathological functions of RAL GTPases and summarizes the current knowledge on the involvement of RAL in human disease as well as current therapeutic targeting strategies. In particular, molecular mechanisms that specifically control RAL activity and RAL effector usage in different scenarios are outlined, putting a spotlight on the complexity of the RAL GTPase signaling network and the emerging theme of RAS-independent regulation and relevance of RAL.

κB-Ras and Ral GTPases regulate acinar to ductal metaplasia during pancreatic adenocarcinoma development and pancreatitis

Pancreatic ductal adenocarcinoma (PDAC) is associated with high mortality and therapy resistance. Here, we show that low expression of κB-Ras GTPases is frequently detected in PDAC and correlates with higher histologic grade. In a model of KRas^G12D-driven PDAC, loss of κB-Ras accelerates tumour development and shortens median survival. κB-Ras deficiency promotes acinar-to-ductal metaplasia (ADM) during tumour initiation as well as tumour progression through intrinsic effects on proliferation and invasion. κB-Ras proteins are also required for acinar regeneration after pancreatitis, demonstrating a general role in control of plasticity. Molecularly, upregulation of Ral GTPase activity and Sox9 expression underlies the observed phenotypes, identifying a previously unrecognized function of Ral signalling in ADM. Our results provide evidence for a tumour suppressive role of κB-Ras proteins and highlight low κB-Ras levels and consequent loss of Ral control as risk factors, thus emphasizing the necessity for therapeutic options that allow interference with Ral-driven signalling.

The molecular mechanisms of acinar-to-ductal metaplasia (ADM) in the course of pancreatitis and cancer development are unclear. Here, the authors show that loss of κB-Ras and consequent Ral activation promotes tumour initiation and progression through persistent ADM and enhanced cell proliferation

trans-Cinnamaldehyde Reverses Depressive-Like Behaviors in Chronic Unpredictable Mild Stress Rats by Inhibiting NF-κB/NLRP3 Inflammasome Pathway

trans-Cinnamaldehyde (TCA) is the main active component extracted from Cinnamomum cassia (C. cassia), which has many pharmacological effects, such as anti-inflammation, lowering blood glucose, and improving nerve function. However, there is no report of TCA in the treatment of depression. The purpose of this study was to investigate the antidepressant-like effect of TCA and the mechanism of NF kappa B (NF-κB) pathway and NLRP3 inflammasome inhibition by TCA. We divided 40 rats into the control group, CUMS group, FLU group, and the TCA group. The activation of the NF-κB pathway and NLRP3 inflammasome in prefrontal cortex and hippocampus of rats in each group was observed. After the treatments with FLU and TCA, the sucrose consumptions in rats increased significantly and the immobility time in forced swimming was decreased significantly compared to the CUMS group. The expression of TLR4, NF-κB-1, p-p65, TNF-α, NLRP3, ASC, caspase-1, IL-1β, and IL-18 proteins in prefrontal cortex and hippocampus was decreased, and the expression of IL-1β, IL-18, and TNF-α in serum was downregulated compared to the CUMS group. Similar to FLU, TCA reverses the depression-like behaviors in rats, which indicates that TCA has a significant antidepressant-like effect. The mechanism of the antidepressant property of TCA might be that it inhibits the activation of the NF-κB pathway and NLRP3 inflammasome in the prefrontal cortex and hippocampus of CUMS rats.

LncRNA NONHSAT113026 represses renal cell carcinoma tumorigenesis through interacting with NF-κB/p50 and SLUG

Renal cell carcinoma (RCC) is one of the most lethal urological malignancies, yet its pathogenesis remains unclear. Here, we reported a long non-coding RNA (lncRNA), NONHSAT 113026 (NOAT113026), which may play an important role in the pathogenesis of RCC. The expression level of NOAT113026 was estimated by qPCR from 76 pairs of RCC and non-tumor (NT) samples. The correlation between NOAT113026 and clinical data of RCC patients was analyzed. NOAT113026 was overexpressed in 786-O and ACHN cell lines by lentivirus-mediated technology and the oncological behavioral changes of RCC cells were observed along with tumorigenicity in experimental nude mice. Compared to the adjacent tissues, NOAT113026 was noticeably downregulated in RCC. Survival analysis showed that the lower the expression level of NOAT113026 was, the shorter the disease-free survival and overall survival in RCC would be. Overexpression of NOAT113026 can decrease the ability of cell migration, invasion, proliferation, and colony formation by regulating NF-κB/p50 and SLUG through a mechanism that involves lncRNA-mRNA interactions. In conclusion, our data suggest that NOAT113026 could be a carcinostatic RNA in RCC, which may serve as a potential prognostic factor and a promising therapeutic target for malignant RCC.

[Activation of nuclear factor-κB subunit p50/p65 enhances gefitinib resistance of lung adenocarcinoma H1650 cell line]

OBJECTIVE

To explore the intrinsic connection between activation of classical nuclear factor-κB (NF-κB) pathway and gefitinib resistance in human lung adenocarcinoma H1650 cells.

METHODS

Human lung adenocarcinoma H1650 cells were exposed to gefitinib continuously for 60 days to obtain resistant H1650 cells. The expressions of P-IκBα, P-p50 and P-p65 in the cytoplasm or nuclei were detected using Western blotting in human lung adenocarcinoma HCC827 cells, parental H1650 cells and gefitinib-resistant H1650 cells. The effects of gefitinib alone or in combination with PDTC on the survival rate and expressions of NF-κB P-p50 and P-p65 were compared among the 3 cell lines.

RESULTS

Gefitinib-resistant H1650 cells showed increased cytoplasmic and nuclear P-IκBα expressions. The expressions of P-p50 and P-p65 differed significantly among the 3 cell line, decreasing in the order of resistant H1650 cells, parental H1650 cells, and gefitinib sensitive HCC827 cell lines (P<0.05 or 0.01). Treatment with gefitinib alone resulted in a significantly lower cell inhibition rate in resistant H1650 cells than in the parental H1650 cells (P<0.05) and HCC827 cells (P<0.01). The resistant H1650 cells had a significantly higher expression of P-p50 and P-p65 than other two cell lines (P<0.05). In both the resistant and parental H1650 cells, gefitinib significantly lowered P-p50 and P-p65 expressions (P<0.05 or 0.01), and the combined treatment with gefitinib and PDTC significantly decreased the cell survival rate and further lowered the cytoplasmic and nuclear expressions of P-p50 and P-p65 (P<0.01 or 0.01).

CONCLUSION

The activation of classical NF-κB pathway is a key factor contributing to transformation of the parental H1650 cells into gefitinib-resistant cells. Gefitinib combined with PDTC can inhibit P-IκBα production and NF-κB P-p50 and P-p65 activation to suppress the survival of residual H1650 cells and the generation of gefitinib-resistant cells.

Signal regulatory protein α associated with the progression of oral leukoplakia and oral squamous cell carcinoma regulates phenotype switch of macrophages

Signal regulatory protein α (SIRPα) is a cell-surface protein expressed on macrophages that are regarded as an important component of the tumor microenvironment. The expression of SIRPα in oral leukoplakia (OLK) and oral squamous cell carcinoma (OSCC), and further explored the role of SIRPα on the phenotype, phagocytosis ability, migration, and invasion of macrophages in OSCC were investigated. The expression of SIRPα in OLK was higher than in OSCC, correlating with the expression of CD68 and CD163 on macrophages. After cultured with the conditioned media of oral cancer cells, the expression of SIRPα on THP-1 cells was decreased gradually. In co-culture system, macrophages were induced into M2 phenotype by oral cancer cells. Blockade of SIRPα inhibited phagocytosis ability and IL-6, TNF-α productions of macrophages. In addition, the proliferation, migration, and IL-10, TGF-β productions of macrophages were upregulated after blockade of SIRPα. Macrophages upregulated the expression of SIRPα and phagocytosis ability, and inhibited the migration and invasion when the activation of NF-κB was inhibited by pyrrolidine dithiocarbamate ammonium (PDTC). Hence, SIRPα might play an important role in the progression of OLK and oral cancer, and could be a pivotal therapeutic target in OSCC by regulating the phenotype of macrophages via targeting NF-κB.

The cytokine-cosmc signaling axis upregulates the tumor-associated carbohydrate antigen Tn

Tn antigen (GalNAc-α-O-Ser/Thr), a mucin-type O-linked glycan, is a well-established cell surface marker for tumors and its elevated levels have been correlated with cancer progression and prognosis. There are also reports that Tn is elevated in inflammatory tissues. However, the molecular mechanism for its elevated levels in cancer and inflammation is unclear. In the current studies, we have explored the possibility that cytokines may be one of the common regulatory molecules for elevated Tn levels in both cancer and inflammation. We showed that the Tn level is elevated by the conditioned media of HrasG12V-transformed-BEAS-2B cells. Similarly, the conditioned media obtained from LPS-stimulated monocytes also elevated Tn levels in primary human gingival fibroblasts, suggesting the involvement of cytokines and/or other soluble factors. Indeed, purified inflammatory cytokines such as TNF-α and IL-6 up-regulated Tn levels in gingival fibroblasts. Furthermore, TNF-α was shown to down-regulate the COSMC gene as evidenced by reduced levels of the COSMC mRNA and protein, as well as hypermethylation of the CpG islands of the COSMC gene promoter. Since Cosmc, a chaperone for T-synthase, is known to negatively regulate Tn levels, our results suggest elevated Tn levels in cancer and inflammation may be commonly regulated by the cytokine-Cosmc signaling axis.

A possible role of GDDR in the development of Helicobacter pylori-associated gastric cancer

Helicobacter pylori (H. pylori) infection plays an important part in the development of gastric carcinoma. GDDR has been confirmed as a tumor suppressor gene in gastric tumorigenesis. However, the underlying mechanism of GDDR in H. pylori-induced carcinogenesis is not well known. The aim of this study is to investigate the clinicopathological significance and possible molecular mechanism of GDDR in gastric cancer associated with H. pylori. Western blot, real-time quantitative PCR (qRT-PCR), and immunohistochemistry were used to detect the expression level of GDDR with or without H. pylori infection. The function and possible related molecular mechanisms of GDDR were further explored in vitro and in vivo. The variability of GDDR expression appeared in the early stage of gastric carcinogenesis with positive H. pylori infection status. GDDR might inhibit the progression of normal gastric epithelial cells to cancer cells by suppressing NF-kappaB signaling pathway, which in turn could be regulated by H. pylori infection. Our results suggested, for the first time, that the gradual change in GDDR expression might not only be directly related to H. pylori infection but also be an early molecular event in the development of gastric carcinoma.