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

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.

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.

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.

Reduced prevalence of the C825T polymorphism of the G-protein beta subunit gene in women with breast cancer

OBJECTIVE

To evaluate the prevalence of the C825T polymorphism in the GNB3 gene in women with and without breast cancer and its possible association with clinical or pathological features of breast disease.

SUBJECTS AND METHODS

We included 134 women with breast cancer and a control group of 129 healthy women. The case group responded to a questionnaire on lifestyle, reproductive factors and family history. Clinical data were also evaluated. The risk for cancer was calculated and PCR was carried out for the detection of the polymorphism. Statistical analysis was performed using the package R Environment, with confidence intervals of 95% and a significance level of 5% (p and lt;0.05).

RESULTS

The frequency of the TT genotype was significantly greater in women of the control group (30.2%) than women with breast cancer (14.9%) (p=0.02). The polymorphism was not associated with clinical features, age at diagnosis (p=0.07), age at menarche (p=0.17), and age at menopause (p=0.60). The TT genotype did not have a higher frequency in patients with high BMI (p=0.98). The risk for cancer showed no correlation with the presence of the polymorphism.

CONCLUSIONS

Our data indicate that the C825T polymorphism in the GNB3 gene has no relationship to the risk for breast cancer or the characteristics of the disease.

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.

Intensity of opiate withdrawal in relation to the 825C>T polymorphism of the G-protein beta 3 subunit gene

OBJECTIVES

The intensity of withdrawal in opiate dependence shows a high inter-individual variability. The 825C>T polymorphism (rs5443) of the G-protein beta 3 (GNB3) subunit gene has a strong influence on clinical signs of sympathetic activity in cardiac research. This study was carried out in order to test the hypothesis that carriers of the T allele have an increased sympathetic activity in opiate withdrawal.

METHODS

Thirty-nine monovalent opiate addicted patients consecutively admitted to a detoxification ward were investigated. The main parameter for sympathetic activity was the pulse rate in the first 3 days after the regular end of gradual methadone reduction.

RESULTS

Thirty-three out of 39 patients achieved a drug-free state: 22 carried a T allele (TT, CT), 11 belonged to the CC genotype group. The pulse rate was significantly (p<0.05) raised in the T allele group compared to the CC genotype group on the first 2 days after stopping methadone administration. In addition, about a third of the T allele carriers needed clonidine treatment on the respective days, but only one patient among the 11 CC homozygotes. There was no significant difference between groups in systolic and diastolic blood pressures as well as in subjective withdrawal ratings.

CONCLUSION

A group difference regarding pulse rate could be observed in a small sample and despite a higher degree of concomitant clonidine medication in T allele carriers. The failure to detect group differences in blood pressure and self-rated withdrawal symptoms may be attributed to the more complex regulation of blood pressure and the known weak correlation between objective and subjective withdrawal symptoms.