The lncRNA TRG-AS1 promotes the growth of colorectal cancer cells through the regulation of P2RY10/GNA13

BACKGROUND

The lncRNA TRG-AS1 and its co-expressed gene P2RY10 are important for colorectal cancer (CRC) occurrence and development. The purpose of our research was to explore the roles of TRG-AS1 and P2RY10 in CRC progression.

METHODS

The abundance of TRG-AS1 and P2RY10 in CRC cell lines (HT-29 and LoVo) and normal colon cells FHC was determined and difference between CRC cells and normal cells was compared. LoVo cells were transfected with si-TRG-AS1 and si-P2RY10 constructs. Subsequently, the viability, colony formation, and migration of the transfected cells were analyzed using cell counting kit-8, clonogenicity, and scratch-wound/Transwell® assays, respectively. Cells overexpressing GNA13 were used to further explore the relationship between TRG-AS1 and P2RY10 along with their downstream functions. Finally, nude mice were injected with different transfected cell types to observe tumor formation in vivo.

RESULTS

TRG-AS1 and P2RY10 were significantly upregulated in HT-29 and LoVo compared to FHC cells. TRG-AS1 knockdown and P2RY10 silencing suppressed the viability, colony formation, and migration of LoVo cells. TRG-AS1 knockdown downregulated the expression of P2RY10, GNA12, and GNA13, while P2RY10 silencing downregulated the expression of TRG-AS1, GNA12, and GNA13. Additionally, GNA13 overexpression reversed the cell growth and gene expression changes in LoVo cells induced by TRG-AS1 knockdown or P2RY10 silencing. In vivo experiments revealed that CRC tumor growth was suppressed by TRG-AS1 knockdown and P2RY10 silencing.

CONCLUSIONS

TRG-AS1 knockdown repressed the growth of HT-29 and LoVo by regulating P2RY10 and GNA13 expression.

GNA13 inhibits glioblastoma metastasis via the ERKs/FOXO3 signaling pathway

Glioblastoma (GBM) is a malignant tumor characterized by poor prognosis and low overall survival (OS) rate. Identification of novel biological markers for the diagnosis and treatment of GBM is crucial to developing interventions to improve patient survival. GNA13, a member of the G12 family, has been reported to play important roles in a variety of biological processes involved in tumorigenesis and development. However, its role in GBM is currently unknown. Here, we explored the expression patterns and functions of GNA13 in GBM, as wells its impact on metastasis process. Results showed that GNA13 was downregulated in GBM tissues and correlated with poor prognosis of GBM. Downregulation of GNA13 promoted the migration, invasion and proliferation of GBM cells; whereas its overexpression abolished these effects. Western blots revealed that GNA13 knockdown and overexpression upregulated and inhibited the phosphorylation of ERKs, respectively. Moreover, GNA13 was the upstream of ERKs signaling to regulating ERKs phosphorylation level. Furthermore, U0126 alleviated the metastasis effect induced by GNA13 knockdown. Bioinformatics analyses and qRT-PCR experiments demonstrated that GNA13 could regulate FOXO3, a downstream signaling molecule of ERKs pathway. Overall, our results demonstrate that GNA13 expression is negatively correlated with GBM and can suppress tumor metastasis by inhibiting the ERKs signaling pathway and upregulating FOXO3 expression.

Overexpressed Gα13 activates serum response factor through stoichiometric imbalance with Gβγ and mislocalization to the cytoplasm

Gα13, a heterotrimeric G protein α subunit of the G12/13 subfamily, is an oncogenic driver in multiple cancer types. Unlike other G protein subfamilies that contribute to cancer progression via amino acid substitutions that abolish their deactivating, intrinsic GTPase activity, Gα13 rarely harbors such mutations in tumors and instead appears to stimulate aberrant cell growth via overexpression as a wildtype form. It is not known why this effect is exclusive to the G12/13 subfamily, nor has a mechanism been elucidated for overexpressed Gα13 promoting tumor progression. Using a reporter gene assay for serum response factor (SRF)-mediated transcription in HEK293 cells, we found that transiently expressed, wildtype Gα13 generates a robust SRF signal, approximately half the amplitude observed for GTPase-defective Gα13. When epitope-tagged, wildtype Gα13 was titrated upward in cells, a sharp increase in SRF stimulation was observed coincident with a "spillover" of Gα13 from membrane-associated to a soluble fraction. Overexpressing G protein β and γ subunits caused both a decrease in this signal and a shift of wildtype Gα13 back to the membranous fraction, suggesting that stoichiometric imbalance in the αβγ heterotrimer results in aberrant subcellular localization and signalling by overexpressed Gα13. We also examined the acylation requirements of wildtype Gα13 for signalling to SRF. Similar to GTPase-defective Gα13, S-palmitoylation of the wildtype α subunit was necessary for SRF activation but could be replaced functionally by an engineered site for N-terminal myristoylation. However, a key difference was observed between wildtype and GTPase-defective Gα13: whereas the latter protein lacking palmitoylation sites was rescued in its SRF signalling by either an engineered polybasic sequence or a C-terminal isoprenylation site, these motifs failed to restore signalling by wildtype, non-palmitoylated Gα13. These findings illuminate several components of the mechanism in which overexpressed, wildtype Gα13 contributes to growth and tumorigenic signalling, and reveal greater stringency in its requirements for post-translational modification in comparison to GTPase-defective Gα13.

Overexpression of GNA13 correlates with poor prognosis in esophageal squamous cell carcinoma after esophagectomy

BACKGROUND

This study aimed to explore the expression and clinical implication of guanine nucleotide-binding protein alpha 13 (GNA13) in esophageal squamous cell carcinoma (ESCC).

METHODS

We first employed western blot analysis to test the GNA13 protein expression level in ESCC tissues. Subsequently, we used immunohistochemistry assays to detect the GNA13 in ESCC specimens from 173 patients who underwent esophagectomy. Survival analysis was performed to define the impact of GNA13 expressions on the prognosis of the ESCC patients based on the clinical and follow-up data.

RESULTS

The GNA13 protein was shown to be considerably higher in ESCC tissues than in normal esophageal tissues. The level of expression was closely related to the tumor, node, TNM stage, and tumor size. More importantly, ESCC patients with high GNA13 expression carried an increased risk of tumor recurrence compared to those with low GNA13 expression. In addition, a high GNA13 expression level could independently predict worse overall survival and disease-free survival in ESCC.

CONCLUSIONS

GNA13 could be a novel prognostic biomarker for ESCC patients after esophagectomy.

Overexpressed GNA13 induces temozolomide sensitization via down-regulating MGMT and p-RELA in glioma

Temozolomide (TMZ), one of the few effective drugs used during adjuvant therapy, could effectively prolong the overall survival (OS) of glioma patients. In our previous study, the mRNA level of G Protein Subunit Alpha 13 (GNA13) was found to be inversely correlated with OS and was therefore identified as a potential biomarker for the prognosis of glioma. Henceforth, this study aims to identify the molecular mechanism of GNA13 in enhancing TMZ sensitization through bioinformatic analyses of GSE80729 and GSE43452 and other experiments. In glioma, overexpression of GNA13 downregulated PRKACA, which is a subunit of PKA, hence reducing phosphorylated RELA and MGMT. Since p-RELA and MGMT were proven to be closely associated with TMZ resistance, we therefore investigated whether thetwo signaling pathways, "GNA13/PRKACA/p-RELA", and "GNA13/PRKACA/MGMT", were involved in the molecular mechanism of GNA13 in TMZ sensitization. Our conclusion was that, GNA13 overexpression in glioma cells were more sensitive in TMZ treatment.

SP3 is associated with migration, invasion, and Akt/PKB signalling in MDA-MB-231 breast cancer cells

Specificity proteins (SPs) have pro-oncogenic functions in cancer cells, ranging from cancer cell proliferation, migration, invasion, and angiogenesis. There is strong evidence that several antineoplastic drugs target depletion of SP proteins via different pathways. However, the mode of action of SP3 and the underlying consequences of its depletion are not well understood. Here, we demonstrate that SP3 is overexpressed in invasive breast cancer cells vs normal counterparts. The gene expression analysis from The Cancer Genome Atlas datasets indicated that SP3 is strongly correlated with Akt signalling-related proteins, G protein subunit alpha 13, and RAB33B (RAB33B, member RAS oncogene family). RNA interference of SP3 decreased active phosphorylation of Akt at serine and threonine sites. These findings indicate that SP3 exhibits a pro-oncogenic function, which clearly fits the description of an nononcogene addiction gene. Future analyses are prompted to uncover the SP3 gene regulation function and to reveal downstream targets of SP3 in breast cancer.

Gα-13 induces CXC motif chemokine ligand 5 expression in prostate cancer cells by transactivating NF-κB

GNA13, the α subunit of a heterotrimeric G protein, mediates signaling through G-protein-coupled receptors (GPCRs). GNA13 is up-regulated in many solid tumors, including prostate cancer, where it contributes to tumor initiation, drug resistance, and metastasis. To better understand how GNA13 contributes to tumorigenesis and tumor progression, we compared the entire transcriptome of PC3 prostate cancer cells with those cells in which GNA13 expression had been silenced. This analysis revealed that GNA13 levels affected multiple CXC-family chemokines. Further investigation in three different prostate cancer cell lines singled out pro-tumorigenic CXC motif chemokine ligand 5 (CXCL5) as a target of GNA13 signaling. Elevation of GNA13 levels consistently induced CXCL5 RNA and protein expression in all three cell lines. Analysis of the CXCL5 promoter revealed that the -505/+62 region was both highly active and influenced by GNA13, and a single NF-κB site within this region of the promoter was critical for GNA13-dependent promoter activity. ChIP experiments revealed that, upon induction of GNA13 expression, occupancy at the CXCL5 promoter was significantly enriched for the p65 component of NF-κB. GNA13 knockdown suppressed both p65 phosphorylation and the activity of a specific NF-κB reporter, and p65 silencing impaired the GNA13-enhanced expression of CXCL5. Finally, blockade of Rho GTPase activity eliminated the impact of GNA13 on NF-κB transcriptional activity and CXCL5 expression. Together, these findings suggest that GNA13 drives CXCL5 expression by transactivating NF-κB in a Rho-dependent manner in prostate cancer cells.

GNA13 promotes tumor growth and angiogenesis by upregulating CXC chemokines via the NF-κB signaling pathway in colorectal cancer cells

GNA13 has been found overexpressed in various types of cancer, which is related to tumor metastasis and progression. However, the biological functions of GNA13 in colorectal cancer (CRC) progression remain unclear. This study aimed to explore the role of GNA13 in CRC and investigate the mechanism of how GNA13 promotes tumor growth. Interestingly, our findings showed that GNA13 is commonly upregulated in CRC, where these events are associated with a worse histologic grade and poor survival. Increased expression levels of GNA13 promoted cell growth, migration, invasion, and epithelial-mesenchymal transition, whereas GNA13 silencing abrogated these malignant phenotypes. In addition, overexpressing GNA13 in cancer cells increased the levels of the chemokines CXCL1, CXCL2, and CXCL4, which contributed to CRC proliferation and colony formation. Moreover, our mechanistic investigations suggest that the NF-κB/p65 signaling pathway was activated by the increase in GNA13 levels. Inhibiting the NF-κB/p65 pathway with an inhibitor decreased GNA13-induced migration, invasion and CXCL chemokine level increases, indicating the critical role of NF-κB/p65 signaling in mediating the effects of GNA13 in CRC. Together, these results demonstrate a key role of GNA13 overexpression in CRC that contributes to malignant behavior in cancer cells, at least in part through stimulating angiogenesis and increasing the levels of the NF-κB-dependent chemokines CXCL1, CXCL2, and CXCL4.

miRNA-30d serves a critical function in colorectal cancer initiation, progression and invasion via directly targeting the GNA13 gene

MicroRNAs (miRNAs or miRs) are reported to be dysregulated in the progression and invasion of various human cancer types, including colorectal cancer (CRC). They are also reported to be molecular biomarkers and therapeutic targets in CRC. miRNAs serve functions in a plethora of biological processes, including proliferation, migration, invasion and apoptosis, and several miRNAs have been demonstrated to be involved in CRC carcinogenesis, invasion and metastasis. Aberrant miR-30d expression and its effects have been reported in certain cancer types. However, the function and underlying mechanism of miR-30d in the progression of CRC remains largely unknown. In the current study, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to quantify miR-30d expression in CRC tissues. In vivo and in vitro functional assays indicated that miR-30d inhibits CRC cell proliferation. Target prediction online software packages, miRBase, TargetScan and miRANDA, and luciferase reporter assays were used to confirm the target gene GNA13. Specimens from 45 patients with CRC were analyzed for correlation between the expression of miR-30d and the expression of target gene GNA13, evaluated by RT-qPCR. miR-30d was downregulated in CRC tissues and cell lines. Ectopic expression of miR-30d inhibited cell proliferation and invasion and tumor growth ability. By contrast, inhibition of endogenous miR-30d promoted cell proliferation and tumor growth ability of CRC cells. It was indicated that miR-30d directly targets the 3'-untranslated region of the GNA13 gene. Downregulation of miR-30d led to the activation of cell proliferation in CRC. In addition, miR-30d expression was negatively correlated with the expression of GNA13 in CRC tissues. In conclusion, miR-30d inhibits cancer initiation, proliferation and invasion in colorectal cancer via targeting GNA13.

FZD10-Gα13 signalling axis points to a role of FZD10 in CNS angiogenesis

Among the 10 Frizzled (FZD) isoforms belonging to the Class F of G protein-coupled receptors (GPCRs), FZD₁₀ remains the most enigmatic. FZD₁₀ shows homology to FZD₄ and FZD₉ and was previously implicated in both β-catenin-dependent and -independent signalling. In normal tissue, FZD₁₀ levels are generally very low; however, its upregulation in synovial carcinoma has attracted some attention for therapy. Our findings identify FZD₁₀ as a receptor interacting with and signalling through the heterotrimeric G protein Gα₁₃ but not Gα_12, Gα_i1, Gα_oA, Gα_s, or Gα_q. Stimulation with the FZD agonist WNT induced the dissociation of the Gα₁₃ protein from FZD₁₀, and led to global Gα_12/13-dependent cell changes assessed by dynamic mass redistribution measurements. Furthermore, we show that FZD₁₀ mediates Gα_12/13 activation-dependent induction of YAP/TAZ transcriptional activity. In addition, we show a distinct expression of FZD₁₀ in embryonic CNS endothelial cells at E11.5-E14.5. Given the well-known importance of Gα₁₃ signalling for the development of the vascular system, the selective expression of FZD₁₀ in brain vascular endothelial cells points at a potential role of FZD₁₀-Gα₁₃ signalling in CNS angiogenesis.

GNA13 as a prognostic factor and mediator of gastric cancer progression

Guanine nucleotide binding protein (G protein), alpha 13 (GNA13) has been implicated as an oncogenic protein in several human cancers. In this study, GNA13 was characterized for its role in gastric cancer (GC) progression and underlying molecular mechanisms. The expression dynamics of GNA13 were examined by immunohistochemistry (IHC) in two independent cohorts of GC samples. A series of in-vivo and in-vitro assays was performed to elucidate the function of GNA13 in GC and its underlying mechanisms. In both two cohorts of GC samples, we observed that GNA13 was markedly overexpressed in GC tissues and associated closely with aggressive magnitude of GC progression and poor patients' survival. Further study showed that upregulation of GNA13 expression increased the proliferation and tumorigenicity of GC cells in vitro and in vivo, by promoting cell growth rate, colony formation, and tumor formation in nude mice. By contrast, knockdown of GNA13 effectively suppressed the proliferation and tumorigenicity of GC cells in vitro and in vivo. Our results also demonstrated that the molecular mechanisms of the effect of GNA13 in GC included promotion of G1/S cell cycle transition through upregulation of c-Myc, activation of AKT and ERK activity, suppression of FOXO1 activity, upregulation of cyclin-dependent kinase (CDK) regulator cyclin D1 and downregulation of CDK inhibitor p21Cip1 and p27Kip1. Our present study illustrated that GNA13 has an important role in promoting proliferation and tumorigenicity of GC, and may represent a novel prognostic biomarker and therapeutic target for this disease.

Gα13 mediates human cytomegalovirus-encoded chemokine receptor US28-induced cell death in melanoma

US28, a constitutively active G-protein-coupled receptor encoded by the human cytomegalovirus, leads to mechanistically unknown programmed cell death. Here we show that expression of wild-type US28 in human melanoma cells leads to apoptotic cell death via caspase 3 activation along with reduced cell proliferation. Reduced tumor growth upon US28 expression was observed in a xenograft mouse model. The signaling mute US28R129A showed a reduced antiproliferative effect. On evaluating different G-proteins coupled to US28 for signal transduction, Gα13 was identified as the main G-protein executing the apoptotic effect. Silencing of Gα13 but not Gαq resulted in a substantial increase in cell survival. Overexpression of Gα13 but not Gαq and their GTPase deficient forms Gα13Q226L and GαqQ209L, respectively, confirmed the requirement of Gα13 for US28 mediated cell death. Increasing expression of Gα13 alone induced cell death underscoring its relay function for US28 mediated decreased cell viability. Further reduced expression of Gα13 in melanoma cell lines isolated from advanced lesions and melanoma tissue was observed. These findings identified Gα13 as crucial for US28-induced cell death, substantiating that the effect of US28 on cell fate depends on preferred G-protein binding.

MiR-29c mediates epithelial-to-mesenchymal transition in human colorectal carcinoma metastasis via PTP4A and GNA13 regulation of β-catenin signaling

BACKGROUND

Distant metastasis is the major cause of cancer-related death, and epithelial-to-mesenchymal transition (EMT) has a critical role in this process. Accumulating evidence indicates that EMT can be regulated by microRNAs (miRNAs). miR-29c has been implicated as a tumor suppressor in several human cancers. However, the role of miR-29c in the progression of colorectal cancer (CRC) metastasis remains largely unknown.

PATIENTS AND METHODS

The expression of miR-29c was examined by qRT-PCR in a cohort of primary CRC (PC) and distant liver metastasis (LM) tissues. A series of in vivo and in vitro assays were carried out in order to elucidate the functions of miR-29c and the molecular mechanisms underlying the pathogenesis of metastatic CRC.

RESULTS

miR-29c was markedly downregulated in PCs with distant metastasis and determined to be an independent predictor of shortened patient survival. But LM tissues showed higher levels of miR-29c than that in PC tissues. In CRC cells, miR-29c dramatically suppressed cell migration and invasion abilities in vitro and cancer metastasis in vivo. In addition, miR-29c inhibited EMT and negatively regulated Wnt/β-catenin signaling pathway. Guanine nucleotide binding protein alpha13 (GNA13) and protein tyrosine phosphatase type IVA (PTP4A) were identified as direct targets of miR-29c, which acted through ERK/GSK3β/β-catenin and AKT/GSK3β/β-catenin pathways, respectively, to regulate EMT. Furthermore, significant associations between miR-29c, its target genes (GNA13 and PTP4A) and EMT markers were validated in both PC and LM tissues.

CONCLUSION

Our findings highlight the important role of miR-29c in regulating CRC EMT via GSK-3β/β-catenin signaling by targeting GNA13 and PTP4A and provide new insights into the metastatic basis of CRC.

Breast cancer cell invasion mediated by Gα12 signaling involves expression of interleukins-6 and -8, and matrix metalloproteinase-2

Background

Recent studies on the involvement of the G12 family of heterotrimeric G proteins (Gα12 and Gα13, the products of the GNA12 and GNA13 genes, respectively) in oncogenic pathways have uncovered a link between G12 signaling and cancer progression. However, despite a well characterized role of Rho GTPases, the potential role of secreted factors in the capacity of G12 signaling to promote invasion of cancer cells is just beginning to be addressed.

Methods

MDA-MB-231 and MCF10A breast cancer cell lines were employed as a model system to explore the involvement of secreted factors in G12-stimulated cell invasion. Factors secreted by cells expressing dominant-active Gα12 were identified by protein array, and their involvement in breast cancer cell invasion was assessed through both RNAi-mediated knockdown and antibody neutralization approaches. Bioinformatics analysis of the promoter elements of the identified factors suggested NF-κB elements played a role in their enhanced expression, which was tested by chromatin immunoprecipitation.

Results

We found that signaling through the Gα12 in MDA-MB-231 and MCF10A breast cancer cell lines enhances expression of interleukins (IL)-6 and −8, and matrix metalloproteinase (MMP)-2, and that these secreted factors play a role in G12-stimulated cell invasion. Furthermore, the enhanced expression of these secreted factors was found to be facilitated by the activation of their corresponding promoters, where NF-κB seems to be one of the major regulators. Inhibition of IL-6 and IL-8, or MMP-2 activity significantly decreased Gα12-mediated cell invasion.

Conclusions

These studies confirm and extend findings that secreted factors contribute to the oncogenic potential of G12 signaling, and suggest potential therapeutic targets to control this process.