A polymorphism in the G protein β3-subunit gene is associated with bone metastasis risk in breast cancer patients

Subtype-dependent regulation of Gβγ signalling

G protein-coupled receptors (GPCRs) transmit information to the cell interior by transducing external signals to heterotrimeric G protein subunits, Gα and Gβγ subunits, localized on the inner leaflet of the plasma membrane. Though the initial focus was mainly on Gα-mediated events, Gβγ subunits were later identified as major contributors to GPCR-G protein signalling. A broad functional array of Gβγ signalling has recently been attributed to Gβ and Gγ subtype diversity, comprising 5 Gβ and 12 Gγ subtypes, respectively. In addition to displaying selectivity towards each other to form the Gβγ dimer, numerous studies have identified preferences of distinct Gβγ combinations for specific GPCRs, Gα subtypes and effector molecules. Importantly, Gβ and Gγ subtype-dependent regulation of downstream effectors, representing a diverse range of signalling pathways and physiological functions have been found. Here, we review the literature on the repercussions of Gβ and Gγ subtype diversity on direct and indirect regulation of GPCR/G protein signalling events and their physiological outcomes. Our discussion additionally provides perspective in understanding the intricacies underlying molecular regulation of subtype-specific roles of Gβγ signalling and associated diseases.

Speeding up the discovery of combinations of differentially expressed genes for disease prediction and classification

BACKGROUND AND OBJECTIVE

Finding combinations (i.e., pairs, or more generally, q-tuples with q ≥ 2) of genes whose behavior as a group differs significantly between two classes has received a lot of attention in the quest for the discovery of simple, accurate, and easily interpretable decision rules for disease classification and prediction. For example, the Top Scoring Pair (TSP) method seeks to find pairs of genes so that the probability of the reversal of the relative ranking of the expression levels of the genes in the two classes is maximized. The computational cost of finding a q-tuple of genes that scores highest under a given metric is O(G^q), where G is the total number of genes. This cost is often problematic or prohibitive in practice (even for q=2), as the number of genes G is often in the order of tens of thousands.

METHODS

In this paper, we show that this computational cost can be significantly reduced by excluding from consideration genes whose behavior is almost identical in the two classes and therefore their inclusion in any q-tuple is rather non-informative. Our criterion for the exclusion of genes is supported by a statistically robust metric, the Area Under the Curve (AUC) of the corresponding Receiver Operating Characteristic (ROC) curve. By filtering out genes whose AUC value is below a user-chosen threshold, as determined by a procedure that we describe in the paper, dramatic reductions in the run times are obtained while maintaining the same classification accuracy.

RESULTS

We have experimentally verified the gains of this approach on several case studies involving ovarian, colon, leukemia, breast and prostate cancers, and diffuse large b-cell lymphoma.

CONCLUSIONS

The proposed method is not only faster (for example, we observed an average 78.65% reduction over the run time of TSP) while maintaining the same classification accuracy, but it can even result in better classification accuracy due to its inherent ability to avoid the so-called "pivot" (non-informative) genes that may intrude in q-tuples chosen otherwise.

An Integrative Approach Uncovers Biomarkers that Associate with Clinically Relevant Disease Outcomes in Vulvar Carcinoma

Vulvar squamous cell carcinoma (VSCC) is a rare disease that has a high mortality rate (∼40%). However, little is known about its molecular signature. Therefore, an integrated genomics approach, based on comparative genome hybridization (aCGH) and genome-wide expression (GWE) array, was performed to identify driver genes in VSCC. To achieve that, DNA and RNA were extracted from frozen VSCC clinical specimens and examined by aCGH and GWE array, respectively. On the basis of the integration of data using the CONEXIC algorithm, PLXDC2 and GNB3 were validated by RT-qPCR. The expression of these genes was then analyzed by IHC in a large set of formalin-fixed paraffin-embedded specimens. These analyses identified 47 putative drivers, 46 of which were characterized by copy number gains that were concomitant with overexpression and one with a copy number loss and downregulation. Two of these genes, PLXDC2 and GNB3, were selected for further validation: PLXDC2 was downregulated and GNB3 was overexpressed compared with non-neoplastic tissue. By IHC, both proteins were ubiquitously expressed throughout vulvar tissue. High expression of GNB3 and low PLXDC2 immunostaining in the same sample was significantly associated with less lymph node metastasis and greater disease-free survival. On the basis of a robust methodology never used before for VSCC evaluation, two novel prognostic markers in vulvar cancer are identified: one with favorable prognosis (GNB3) and the other with unfavorable prognosis (PLXDC2).

IMPLICATIONS

This genomics study reveals markers that associate with prognosis and may provide guidance for better treatment in vulvar cancer. Mol Cancer Res; 14(8); 720-9. ©2016 AACR.

Correction of the Pathogenic Alternative Splicing, Caused by the Common GNB3 c.825C>T Allele, Using a Novel, Antisense Morpholino

The very common GNB3 c.825C>T polymorphism (rs5443) is present in approximately half of all human chromosomes. Significantly, the presence of the GNB3 825T allele has been strongly associated with predisposition to essential hypertension. Paradoxically the presence of the GNB3 825T allele, in exon 10, introduces a pathogenic alternative RNA splice site into the middle of exon 9. To attempt to correct this pathogenic aberrant splicing, we, therefore, bioinformatically designed, using a Gene Tools(®) algorithm, a GNB3-specific, antisense morpholino. It was hoped that this morpholino would behave in vitro as either a potential splice blocker and/or exon skipper, to both bind and inhibit/reduce the aberrant splicing of the GNB3 825T allele. On transfecting a human lymphoblast cell line homozygous for the 825T allele, with this antisense morpholino, we encouragingly observed both a significant reduction (from ∼58% to ∼5%) in the production of the aberrant smaller GNB3 transcript, and a subsequent increase in the normal GNB3 transcript (from ∼42% to ∼95%). Our results demonstrate the potential use of a GNB3-specific antisense morpholino, as a pharmacogenetic therapy for essential hypertension.

Differential G protein subunit expression by prostate cancer cells and their interaction with CXCR5

Background

Prostate cancer (PCa) cell lines and tissues differentially express CXCR5, which positively correlate with PCa progression, and mediate PCa cell migration and invasion following interaction with CXCL13. However, the differential expression of G protein α, β, and γ subunits by PCa cell lines and the precise combination of these proteins with CXCR5 has not been elucidated.

Methods

We examined differences in G protein expression of normal prostate (RWPE-1) and PCa cell lines (LNCaP, C4-2B, and PC3) by western blot analysis. Further, we immunoprecipitated CXCR5 with different G protein subunits, and CXCR4, following CXCL13 stimulation. To investigate constitutive coupling of CXCR5 with CXCR4 and PAR-1 we performed invasion assay in PCa cells transfected with G_αq/i2 or G_α13 siRNA, following CXCL13 treatment. We also investigated Rac and RhoA activity by G-LISA activation assay in PCa cells following CXCL13/thrombin stimulation.

Result

Of the 22 G proteins studied, G_αi1-3, G_β1-4, G_γ5, G_γ7, and G_γ10 were expressed by both normal and PCa cell lines. G_αs was moderately expressed in C4-2B and PC3 cell lines, G_αq/11 was only present in RWPE-1 and LNCaP cell lines, while G_α12 and G_α13 were expressed in C4-2B and PC3 cell lines. G_γ9 was expressed only in PCa cell lines. G_α16, G_β5, G_γ1-4, and G_γ13 were not detected in any of the cell lines studied. Surprisingly, CXCR4 co-immunoprecipitated with CXCR5 in PCa cell lines irrespective of CXCL13 treatment. We also identified specific G protein isoforms coupled to CXCR5 in its resting and active states. G_αq/11/G_β3/G_γ9 in LNCaP and G_αi2/G_β3/G_γ9 in C4-2B and PC3 cell lines, were coupled to CXCR5 and disassociated following CXCL13 stimulation. Interestingly, G_α13 co-immunoprecipitated with CXCR5 in CXCL13-treated, but not in untreated PCa cell lines. Inhibition of G_αq/i2 significantly decreased the ability of cells to invade, whereas silencing G_α13 did not affect CXCL13-dependent cell invasion. Finally, CXCL13 treatment significantly increased Rac activity in G_αq/i2 dependent manner, but not RhoA activity, in PCa cell lines.

Conclusions

These findings offer insight into molecular mechanisms of PCa progression and can help to design some therapeutic strategies involving CXCR5 and/or CXCL13 blockade and specific G protein inhibition to abrogate PCa metastasis.

G Protein β3 subunit gene C825T polymorphism and its association with the presence and clinicopathological characteristics of prostate cancer

PURPOSE

A C825T polymorphism in the GNB3 gene encodes the Gβ3 subunit of heterotrimeric G proteins. Due to increased G protein activation the GNB3 825T allele, a truncated form of the G3 protein, is associated with enhanced signal transduction capacity. This splice variant is associated with various malignant diseases. We investigated the possible association of GNB3 gene polymorphism with prostate cancer and its clinicopathological characteristics.

MATERIALS AND METHODS

Using polymerase chain reaction and restriction fragment length polymorphism the allele frequency of the C825T polymorphism was investigated in 172 patients with prostate cancer. Results were compared with those of 344 age matched, healthy blood donors.

RESULTS

The frequency of the GNB3 825T allele in patients with prostate cancer was significantly higher than in controls (49.1% vs 42.7%, OR 3.76, p = 0.003). Patients with prostate cancer who had the TT genotype were at 2.52 times higher risk for prostate cancer than the CC genotype referent group (OR 2.22, 95% CI 1.18-4.22, p = 0.008). Accordingly a significant increased risk of advanced disease was observed in men carrying the GNB3 TT genotype compared with those homozygous for the wild-type C allele (OR 6.24, 95% CI 4.16-12.45, p = 0.001). Men lacking the C825 allele were at approximately sevenfold higher risk for high grade (Gleason score greater than 7) prostate cancer than men with the GNB3 CC genotype.

CONCLUSIONS

Our study presents preliminary but intriguing data suggesting that GNB3 gene polymorphism influences susceptibility to prostate cancer.

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.

Novel somatic mutations in heterotrimeric G proteins in melanoma

Heterotrimeric guanine nucleotide-binding proteins (G proteins) mediate signals between G-protein coupled receptors and their downstream pathways, and have been shown to be mutated in cancer. In particular, GNAQ was found to be frequently mutated in blue nevi of the skin and uveal melanoma, acting as an oncogene in its mutated form. To further examine the role of heterotrimeric G proteins in malignant melanoma, we performed a comprehensive mutational analysis of the 35 genes in the heterotrimeric G protein gene family in a panel of 80 melanoma samples. Somatic alterations in a G protein subunit were detected in 17% of samples spanning 7 genes. The highest rates of somatic, non-synonymous mutations were found in GNG10 and GNAZ, neither of which has been previously reported to be mutated in melanoma. Our study is the first systematic analysis of the heterotrimeric G proteins in melanoma and indicates that multiple mutated heterotrimeric G proteins may be involved in melanoma progression.

Analysis of common germline polymorphisms as prognostic factors in patients with lymph node-positive breast cancer

PURPOSE

Women with breast cancer that initially involves local lymph nodes have a higher risk for local recurrence or developing metastases. Recent data suggest that germline polymorphism is a significant, previously unrecognized factor in breast cancer progression and metastasis. We assessed the influence of 16 selected common germline polymorphisms in disease-free survival and overall survival among 216 women diagnosed with lymph node-positive breast cancer.

RESULTS

The rare allele of FAS 1377G>A was significantly associated with prolonged disease-free survival (P = 0.012, risk ratio of recurrence (RR) = 0.557, 95% confidence interval (CI) = 0.353-0.878) in univariate analysis. After adjusting for known breast cancer prognostic factors the association remained significant (P = 0.050, RR = 0.500, CI = 0.309-0.809). In overall survival analysis we found a significant association of the FAS 1377G>A (P = 0.040, RR = 0.451, CI = 0.496-1.188) and IL10 592C>A polymorphisms (P = 0.020, RR = 1.707, CI = 1.087-2.680) in the univariate Cox regression. The effect remained statistically significant in the multivariate analysis for the IL10 592C>A polymorphism (P = 0.013, RR 1.841, CI 1.140-2.973). No association was found for MTHFR 677C>T, VEGF 936C>T, CCND1 870G>A, TGFB1 29T>C, FASLG 844C>T, FAS 670A>G, GPB3 825C>T, ITGA2 807C>T, ITGA2 1648G>A, ITGB3 176T>C, MMP1 -1607 1G/2G, MMP3 5A/6A, PTGS2 8473T>C, IL10 592C>A and SULT1A1 638G>A polymorphisms and disease-free survival or overall survival.

CONCLUSIONS

Our data suggest that the FAS 1377G>A and IL10 592C>A polymorphisms could modify disease-free and overall survival in women with lymph node-positive breast cancer.

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.

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.