The CC Genotype of the C825T Polymorphism of the G Protein β3 Gene (GNB3) is Associated with a High Relapse Rate in Patients with Chronic Lymphocytic Leukaemia

Establishment and Validation of a Comprehensive Prognostic Model for Patients With HNSCC Metastasis

Objective

To identify biomarkers related to head and neck squamous cell carcinoma (HNSCC) metastasis and establish a prognostic model for patients with HNSCC.

Methods

HNSCC mRNA expression data of metastasis and non-metastatic samples were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. After screening the differentially expressed genes (DEGs) in the two datasets, a prognostic model, including clinical factors and biomarkers, was established, and verified in 36 samples of HNSCC by quantitative real-time transcription (qRT)-PCR. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene sets enrichment analysis (GSEA) were consulted to explore the functions of the DEGs.

Results

In total, 108 DEGs were identified. GSEA, GO, and KEGG analyses showed that these DEGs were mainly involved in the proliferation and metastasis of HNSCC. Six genes that were significantly related to metastasis, immune cell infiltration and prognosis were further identified to construct a prognostic gene signature. The reliability of the gene signature was verified in 36 samples of HNSCC. A prognostic model, including tumor stage, risk level, and a nomogram for prediction were further established. Receiver operating characteristic (ROC) analysis, decision curve analysis (DCA), C-index, and calibration plots showed that the model and nomogram perform well.

Conclusion

We constructed a six-gene signature and a nomogram with high performance in predicting the prognosis of patients with HNSCC metastasis.

Targeting cAMP in chronic lymphocytic leukemia: a pathway-dependent approach for the treatment of leukemia and lymphoma

INTRODUCTION

Cyclic AMP (cAMP) promotes growth arrest and/or apoptosis of various types of lymphoma, in particular chronic lymphocytic leukemia (CLL). These responses have spurred the interest in developing agents that increase cAMP to treat such malignancies and to identify mechanisms of the responses.

AREAS COVERED

The murine T-lymphoma cell line S49, has provided an important, pioneering model to define mechanisms of cAMP-mediated lymphoid cell death. Studies with S49 cells demonstrated that cAMP, acting via protein kinase A (PKA), is pro-apoptotic through a mitochondria-dependent pathway and identified cAMP/PKA-regulated targets involved in apoptosis. Akin to such findings, cAMP promotes apoptosis via PKA of cells from patients with CLL. Analysis of mediators of cAMP accumulation and cAMP-promoted apoptosis in CLL cells has revealed approaches to increase cAMP and engage its pro-apoptotic action.

EXPERT OPINION

This 'pathway approach' targeted to cAMP has identified GPCR agonists/antagonists, AC activators (e.g., AC7), PDE inhibitors (e.g., PDE7B) and/or activators or inhibitors of downstream mediators (PKA and Epac, respectively), which might be utilized therapeutically in CLL. Therapy directed at such targets may prove to be clinically useful and may also provide a proof-of-principle of the utility of targeting cAMP signaling in other types of cancer.

The expanding roles of Gβγ subunits in G protein-coupled receptor signaling and drug action

Gβγ subunits from heterotrimeric G proteins perform a vast array of functions in cells with respect to signaling, often independently as well as in concert with Gα subunits. However, the eponymous term "Gβγ" does not do justice to the fact that 5 Gβ and 12 Gγ isoforms have evolved in mammals to serve much broader roles beyond their canonical roles in cellular signaling. We explore the phylogenetic diversity of Gβγ subunits with a view toward understanding these expanded roles in different cellular organelles. We suggest that the particular content of distinct Gβγ subunits regulates cellular activity, and that the granularity of individual Gβ and Gγ action is only beginning to be understood. Given the therapeutic potential of targeting Gβγ action, this larger view serves as a prelude to more specific development of drugs aimed at individual isoforms.

Post-GWAS functional characterization of susceptibility variants for chronic lymphocytic leukemia

Recent genome-wide association studies (GWAS) have identified several gene variants associated with sporadic chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Many of these CLL/SLL susceptibility loci are located in non-coding or intergenic regions, posing a significant challenge to determine their potential functional relevance. Here, we review the literature of all CLL/SLL GWAS and validation studies, and apply eQTL analysis to identify putatively functional SNPs that affect gene expression that may be causal in the pathogenesis of CLL/SLL. We tested 12 independent risk loci for their potential to alter gene expression through cis-acting mechanisms, using publicly available gene expression profiles with matching genotype information. Sixteen SNPs were identified that are linked to differential expression of SP140, a putative tumor suppressor gene previously associated with CLL/SLL. Three additional SNPs were associated with differential expression of DACT3 and GNG8, which are involved in the WNT/β-catenin- and G protein-coupled receptor signaling pathways, respectively, that have been previously implicated in CLL/SLL pathogenesis. Using in silico functional prediction tools, we found that 14 of the 19 significant eQTL SNPs lie in multiple putative regulatory elements, several of which have prior implications in CLL/SLL or other hematological malignancies. Although experimental validation is needed, our study shows that the use of existing GWAS data in combination with eQTL analysis and in silico methods represents a useful starting point to screen for putatively causal SNPs that may be involved in the etiology of CLL/SLL.

[Genotype of the GNB3 C825T polymorphism, A risk factor for the development and course of prostate cancer?]

BACKGROUND

G protein-mediated signal transduction plays a key role in pathways of metastasis. A C/T polymorphism (dbSNP rs5443) at position 825 of the GNB3 gene has been described. Previous studies demonstrated an association between the GNB3 C825T genotype and different cancer entities.

PATIENTS AND METHODS

In this report genotyping for this marker was performed in 235 prostate cancer patients and 111 healthy control subjects. Clinical follow-up data were available for a subset of 197 patients.

RESULTS

Neither significant evidence for differences in genotype distributions between the prostate cancer cases and controls (odds ratio CT/TT=0.94, 95% CI 0.58-1.51, p=.82) nor evidence for genotype differences in e.g. progression-free survival in the subset of patients was observable (hazard ratio CT/TT=0.77, 95% CI 0.44-1.37, p=.38). Similar results were obtained in the subgroup of patients with primary tumor stage ≤ pT2 N0 M0 undergoing radical prostatectomy.

CONCLUSION

Our data do not support an association between prostate cancer and the genotype of the GNB3 C825T polymorphism. This finding might either indicate a much smaller genetic effect undetectable with the given sample size or a possible hormone dependence of the disease superimposed on the potential effect of the GNB3 C825T genotype.

SNPs in genes encoding G proteins in pharmacogenetics

Heterotrimeric guanine-binding proteins (G proteins) transmit signals from the cell surface to intracellular signal cascades and are involved in various physiological and pathophysiological processes. Polymorphisms in the genes GNB3 (encoding the Gβ3 subunit), GNAS (encoding the Gαs subunit) and GNAQ (encoding the Gαq subunit) have been the primary focus of investigation. Polymorphisms in these genes could be associated with different complex phenotypes underlining that alterations in G-protein signaling can cause multiple disorders. G proteins present a point of convergence or ‘bottleneck’ between various receptors and effectors, thus making them a sensible tool for pharmacogenetic studies. The pharmacogenetic studies performed to date mostly demonstrate an association between G-protein polymorphisms and response to therapy or occurrence of adverse drug effects. Therefore, polymorphisms in genes encoding G-protein subunits may help to individualize drug treatment in various diseases with regard to both efficacy and safety.

Prognostic assessment of three single-nucleotide polymorphisms (GNB3 825C>T, BCL2-938C>A, MCL1-386C>G) in extrahepatic cholangiocarcinoma

BACKGROUND/AIMS

Cholangiocellular carcinoma (CCA) has a devastating prognosis and markers enabling a precise prediction of the clinical outcome have long remained scarce. Recently, it has been demonstrated that genotype distribution of several single-nucleotide polymorphisms (SNPs) in genes that modulate G protein-signal transduction and apoptosis can serve as helpful predictive parameters in various carcinomas. We here aimed at extending the panel of SNPs suitable for predicting the outcome of CCA.

METHODOLOGY

Forty Caucasian patients with extrahepatic CCA and 40 age- and sex-matched healthy white Caucasians were genotyped to elucidate putative associations between clinical outcome and genotypes of the three following SNPs: G protein beta 3 (GNB3) 825C>T, B-cell-lymphoma-2 (Bcl-2) -938C>A, and myeloid cell leukemia-1 (Mcl-1) -386C>G.

RESULTS

Patients homozygous for the C allele of the GNB3 825C>T polymorphism exhibited a significant prolonged overall survival compared with patients displaying the CT or TT genotype (median survival [months]: 31 vs. 13 vs. 7; p < .05) and also showed lower bilirubin serum levels. Additionally, the CC genotype of the BCL2-938C>A polymorphism was associated with higher GLDH serum activities (U/l; 29.8 +/- 7.1 vs. 11.4 +/- 4.3 vs. 5.6 +/- 1.7 comparing CC vs. CA vs. AA; p < .05). Genotype distributions for all SNPs were not significantly different in patients vs. controls.

CONCLUSIONS

GNB3 825C>T SNP may be a novel independent prognostic marker for patients suffering from extrahepatic CCA with the CC genotype to be associated with a favorable clinical outcome. Further prospective studies are needed to confirm these results and reveal additional functional SNP effects.

The role of the calcium-sensing receptor in the development and progression of cancer

The calcium-sensing receptor (CaR) is responsive to changes in the extracellular Ca(2+) (Ca(2+)(o)) concentration. It is a member of the largest family of cell surface receptors, the G protein-coupled receptors, and it has been shown to be involved in Ca(2+)(o) homeostasis. Apart from its primary role in Ca(2+)(o) homeostasis, the CaR may be involved in phenomena that allow for the development of many types of benign or malignant tumors, from parathyroid adenomas to breast, prostate, and colon cancers. For example, whereas the CaR is expressed in both normal and malignant breast tissue, increased CaR levels have been reported in highly metastatic primary breast cancer cells and breast cancer cell lines, possibly contributing to their malignancy and associated alterations in their biological properties. In these settings the CaR exhibits oncogenic properties. Enhanced CaR expression and altered proliferation of prostate cancer cells in response to increased Ca(2+)(o) have also been described. In contrast, colon and parathyroid cancers often present with reduced or absent CaR expression, and activation of this receptor decreases cell proliferation, suggesting a role for the CaR as a tumor suppressor gene. Thus, the CaR may play an important role in the development of many types of neoplasia. Herein, we review the role of the CaR in various benign and malignant tumors in further detail, describing its contribution to parathyroid tumors, breast, prostate, and colon cancers, and we evaluate how pharmacological manipulations of this receptor may be of interest for the treatment of certain cancers in the future.

Characterization of intron-1 haplotypes of the G protein beta 4 subunit gene--association with survival and progression in patients with urothelial bladder carcinoma

PURPOSE

Polymorphisms in genes encoding subunits of heterotrimeric G proteins have been repeatedly associated with various cancers. As G beta gamma signaling is presumed to be involved in proliferation and invasion processes, we analyzed genetic variations in regulatory regions of GNB4, which encodes the G beta 4 subunit, for their potential influence on cancer progression.

EXPERIMENTAL DESIGN

We characterized the promoter of GNB4 and screened the promoter as well as exon 1 and intron 1 for single nucleotide polymorphisms by sequencing 100 healthy controls. Following a haplotype analysis, we determined the functional impact upon gene expression of the defined haplotypes by reporter assays, electrophoretic mobility shift assay and western blot. In addition, these haplotypes were tested for their relation to the disease course of urothelial bladder cancer.

RESULTS

Whereas the promoter of GNB4 revealed no polymorphisms, 33 single nucleotide polymorphisms located in exon 1 and intron 1 were identified and together with a common exon-4 polymorphism implemented in haplotype analysis, which resulted in the determination of distinct haplotype blocks. Reporter activity was haplotype-dependently different (P=0.001). 1*1/1*1 showed increased G beta 4 protein (P=0.003), and bladder cancer patients carrying this diplotype displayed more progressive disease (P=0.046) and a significantly increased mortality (P=0.046). In multivariate analysis,the diplotypes were independent prognostic factors for survival and progression.

CONCLUSION

Intron-1 haplotypes of GNB4 may, thus, serve as predictive markers for progression and survival of patients suffering from bladder cancer.

Association study of the G-protein beta3 subunit C825T polymorphism with disease progression an overall survival in patients with head and neck squamous cell carcinoma

The T-allele of a common C825T single nucleotide polymorphism (SNP) in the gene GNB3, encoding the G3 subunit of heterotrimeric G-proteins, is associated with a truncated form of the G3 protein that imparts a greater signaling capacity than the alternative C-allele encoding a nontruncated protein. We analyzed the C825T-allele status with regard to disease progression in patients with head and neck squamous cell carcinoma (HNSCC). The prognostic value of the SNP was evaluated in an unselected series of 341 patients treated with curative intent for HNSCC including all tumor stages with different therapeutic regimens. Genotype analysis was done by Pyrosequencing using DNA from paraffin-embedded tissue samples. Genotypes were correlated with relapse-free and overall survival. Proportions of 5-year relapse-free intervals were 62% for CC, 60% for TC, and 42% for TT genotypes. Kaplan-Meier curves revealed a significant genotype-dependent relapse-free interval (P = 0.036). In multivariate analysis with stage, localization, grade, gender, and smoking habits as covariates, GNB3 825T homozygous patients displayed a higher risk for relapse than C825 homozygous patients (TT versus CC, hazard ratio; 95% confidence interval, 1.4-4.8; P = 0.002). The same genotype effect was found for overall survival, TT genotypes were at higher risk for death compared with CC genotypes (hazard ratio, 2.6; 95% confidence interval, 1.6-4.3; P < 0.001), and 5-year survival proportions were 60% for CC, 52% for TC, and 33% for TT. The GNB3 C825T SNP thus represents a host derived prognostic marker in HNSCC, which allows identifying high-risk patients, which could benefit from novel and/or more aggressive therapeutic regimes.

Association of a novel regulatory polymorphism (−938C>A) in the BCL2 gene promoter with disease progression and survival in chronic lymphocytic leukemia

Bcl-2 plays a key role in the regulation of apoptosis. We investigated the role of a novel regulatory single-nucleotide polymorphism (−938C>A) in the inhibitory P2 BCL2 promoter in B-cell chronic lymphocytic leukemia (B-CLL). The −938C allele displayed significantly increased BCL2 promoter activity and binding of nuclear proteins compared with the A allele. Concomitantly, Bcl-2 protein expression in B cells from CLL patients carrying the −938 AA genotype was significantly increased compared with CC genotypes. Genotype distribution between 123 CLL patients (42 AA, 55 AC, 26 CC) and 120 genotyped healthy controls (36 AA, 63 AC, 21 CC) was not significantly different, suggesting that genotypes of this polymorphism do not increase the susceptibility for B-CLL. However, median time from first diagnosis to initiation of chemotherapy and median overall survival were significantly shorter in patients with −938AA genotype (38 and 199 months, respectively) compared with AC/CC genotypes (120 and 321 months, respectively; P = .008 and P = .003, respectively). Multivariable Cox regression identified the BCL2−938AA genotype as an independent prognostic factor for the time to first treatment (hazard ratio [HR] 1.9; P = .034) together with disease stage at diagnosis (HR 2.5; P = .004) and ZAP-70 status (HR 3.0; P = .001). The BCL2−938AA genotype is associated with increased Bcl-2 expression and a novel unfavorable genetic marker in patients with B-CLL.