Vav3 Oncogene Research Articles

VAV3 oncogene expression in colorectal cancer: clinical aspects and functional characterization.

Although colorectal cancer (CRC) is one of the most common malignancies worldwide, the current therapeutic approaches for advanced CRC are ineffective. In this study, we investigated the involvement of the VAV3 oncogene in tumor progression and in the prognosis of human CRC. The two patient cohorts in this study comprised 354 CRC cases from 1998 to 2005 with documented pathologic and clinical factors and clinical outcomes. VAV3 protein levels were significantly correlated with the depth of invasion (P = 0.0259), the nodal status (P < 0.0001), distant metastasis (P = 0.0354), the stage (P < 0.0001), and poor disease-free survival (P = 0.003). Multivariate Cox regression analysis showed that VAV3 overexpression is an independent prognostic marker for CRC (P = 0.041). In vitro experiments indicated that VAV3 knockdown inhibited CRC cell growth, spread, and xenograft proliferation. Mechanistic studies further revealed that VAV3 overexpression could dysregulate the expression of cell cycle control- and metastasis-related molecules by activating the PI3K-AKT signaling pathway in both CRC cells and xenografts. This study suggests that VAV3 overexpression could be a useful marker for predicting the outcomes of CRC patients and that VAV3 targeting represents a potential modality for treating CRC.

Vav3 oncogene is upregulated and a poor prognostic factor in breast cancer patients.

The Vav3 oncogene is overexpressed and has a significant role in the tumorigenesis of prostate cancer and glioblastoma. In the present study, the expression status and prognostic value of Vav3 expression was investigated in breast cancer. Vav3 protein levels were analyzed by immunoblotting in human breast cancer and epithelial cell lines. Immunohistochemistry was used to detect Vav3 in a tissue microarray of 173 breast cancers and 19 benign breast lesions. Statistical analysis was performed to reveal the association between Vav3 expression and clinicopathological parameters. Disease-free survival (DFS) and overall survival (OS) were calculated by Kaplan-Meier analysis and the Cox regression model. The Vav3 protein level was higher in the breast cancer cell lines than in the normal human breast cells. Vav3 was expressed in 86.1% of breast cancer patients, but in only 15.6% patients with benign breast disease. Patients with negative estrogen receptor expression, axillary lymph node involvement and a high tumor-node-metastasis stage demonstrated a higher positive rate of Vav3 expression. The Kaplan-Meier survival analysis revealed that patients with higher Vav3 expression exhibited shorter DFS and OS times. The multivariate Cox analysis revealed that Vav3 was a prognostic factor of survival. Overall, Vav3 was overexpressed in human breast cancer cells and this correlated with a shorter survival time, indicating that Vav3 is a biomarker of a poor prognosis for breast cancer patients.

The Vav3 oncogene enhances the malignant potential of prostate cancer cells under chronic hypoxia

ObjectivesWe had previously reported that chronic hypoxia induces androgen-independent growth in the human prostate cancer cell line LNCaP. In this study, we have identified a key molecule, the Vav3 oncogene, and investigated the effects of Vav3 overexpression on cancer cell growth and malignant behavior and the possible apoptosis-inducing effect of Vav3 expression knockdown by small interfering ribonucleic acid (siRNA) in LNCaP cells under chronic hypoxia (LNCaP/CH). Methods and materialsHypoxia-inducible oncogenes were identified by complementary deoxyribonucleic acid (cDNA) microarray and Ingenuity Pathway Analysis in order to investigate gene ontology and functional pathways and networks. siRNA was used to knockdown the Vav3 target gene and analyze the effects on proliferation, invasion, migration, and apoptosis of LNCaP/CH cells. Vav3 cDNA was transfected into LNCaP cells under normoxia (LNCaP/N) to establish Vav3-overexpressing clonal cell lines, whose proliferation, invasion, and migration was then examined. Immunoblot analysis was used to investigate the activation of Akt, a Vav3 downstream target molecule. ResultscDNA microarray analysis and Ingenuity Pathway Analysis identified Vav3 as a hypoxia-inducible oncogene that was highly associated with malignant behavior. Vav3 messenger RNA and protein expression in LNCaP/CH cells were higher than in LNCaP/N and LNCaP cells cultured under acute hypoxia (LNCaP/AH). The growth rate of LNCaP/CH cells was lower than that of LNCaP/N cells but higher than that of LNCaP/AH cells. LNCaP/CH cells showed higher invasion and migration than LNCaP/N and LNCaP/AH cells. Interrupting Vav3 expression strongly suppressed the proliferation, invasion, and migration of LNCaP/CH cells. Furthermore, siRNA led to apoptosis with increased caspase-3 and cleaved poly (adenosine diphosphate-ribose) polymerase activation in LNCaP/CH cells. Stable Vav3 overexpression in LNCaP cells promoted cell proliferation, invasion, and migration with Akt activation. ConclusionsOur results demonstrate that Vav3 plays a crucial role in prostate cancer growth and malignant behavior, thus revealing a novel potential therapeutic target.

Novel Interaction between the Co-chaperone Cdc37 and Rho GTPase Exchange Factor Vav3 Promotes Androgen Receptor Activity and Prostate Cancer Growth*

Elevated androgen receptor (AR) activity in castration-resistant prostate cancer may occur through increased levels of AR co-activator proteins. Vav3, a guanine nucleotide exchange factor, is up-regulated following progression to castration resistance in preclinical models and is overexpressed in a significant number of human prostate cancers. Vav3 is a novel co-activator of the AR. We sought to identify Vav3 binding partners in an effort to understand the molecular mechanisms underlying Vav3 enhancement of AR activity and to identify new therapeutic targets. The cell division cycle 37 homolog (Cdc37), a protein kinase-specific co-chaperone for Hsp90, was identified as a Vav3 interacting protein by yeast two-hybrid screening. Vav3-Cdc37 interaction was confirmed by GST pulldown and, for native proteins, by co-immunoprecipitation experiments in prostate cancer cells. Cdc37 potentiated Vav3 co-activation of AR transcriptional activity and Vav3 enhancement of AR N-terminal-C-terminal interaction, which is essential for optimal receptor transcriptional activity. Cdc37 increased prostate cancer cell proliferation selectively in Vav3-expressing cells. Cdc37 did not affect Vav3 nucleotide exchange activity, Vav3 protein levels, or subcellular localization. Disruption of Vav3-Cdc37 interaction inhibited Vav3 enhancement of AR transcriptional activity and AR N-C interaction. Diminished Vav3-Cdc37 interaction also caused decreased prostate cancer cell proliferation selectively in Vav3-expressing cells. Taken together, we identified a novel Vav3 interacting protein that enhances Vav3 co-activation of AR and prostate cancer cell proliferation. Vav3-Cdc37 interaction may provide a new therapeutic target in prostate cancer.

Targeting the Vav3 oncogene enhances docetaxel-induced apoptosis through the inhibition of androgen receptor phosphorylation in LNCaP prostate cancer cells under chronic hypoxia

BackgroundThe Vav family of Rho/Rac guanosine nucleotide exchange factors comprises three members in mammalian cells. Vav3 enhances androgen receptor (AR) activity during progression to androgen independence in prostate cancer. We examined Vav3 small interfering RNA (siRNA) effects on cell proliferation and apoptosis in docetaxel-treated LNCaP cells under chronic hypoxia (LNCaPH).MethodsWe examined individual and combined effects of Vav3 siRNA (si-Vav3) and docetaxel on cell growth and apoptosis under chronic hypoxia by cell proliferation, flow cytometric, DNA fragmentation, and immunoblot analyses. To clarify the molecular basis of si-Vav3- and docetaxel-induced apoptosis, we analyzed alterations in phosphatidylinositol 3-kinase (PI3K)/Akt, extracellular signal-regulate kinase (ERK), c-jun N-terminal kinase (JNK), and AR pathways using kinase inhibitors in LNCaPH cells. The effects of si-Vav3/atelocollagen complex alone or in combination with docetaxel were assessed on xenografts in nude mice by tumor growth delay.ResultsVav3 overexpression was observed in LNCaPH compared with the expression under normoxia. Interrupting Vav3 signaling using siRNA enhanced docetaxel-induced cell growth suppression compared with that induced by docetaxel alone by inhibition of Akt and ERK phosphorylation, resulting in AR phosphorylation inhibition. In addition to increased B-cell lymphoma 2 (Bcl-2) phosphorylation through JNK signaling in response to docetaxel, si-Vav3 enhanced docetaxel-induced apoptosis, as characterized by the accumulation of sub-G1 phase cells and DNA fragmentation, through Bcl-xL/Bcl-2-associated death promoter (Bad) dephosphorylation, resulting in increased caspase-9, caspase-3, and cleaved poly(ADP-ribose) polymerase activation. Xenograft tumor growth was slightly inhibited by si-Vav3/atelocollagen complex injection and combined use of si-Vav3/atelocollagen complex and docetaxel produced a greater effect than docetaxel alone.ConclusionsInterrupting Vav3 signaling enhances docetaxel-induced apoptosis in LNCaP cells under chronic hypoxia by inhibiting the PI3K/Akt, ERK, and AR signaling pathways. Therapy targeting Vav3 in combination with docetaxel may have practical implications for managing castration-resistant prostate cancer.

Abstract 1651: Targeting Vav3 oncogene enhances docetaxel-induced apoptosis in LNCaP cells under chronic hypoxia

Abstract Introduction and Objective: We previously reported that chronic hypoxic condition (1% oxygen for over six months) induced Vav3 oncogene expression with androgen-independent growth and malignant behavior in LNCaP cells. And overexpression of Vav3 oncogene promoted the growth of LNCaP cells with increased invasion and migration under normoxic condition. The objective of this study was to examine the effect of Vav3 siRNA on cell proliferation and apoptosis in docetaxel-treated LNCaP cells under chronic hypoxic condition. Methods: We analyzed the sensitivity of docetaxel in LNCaP cells under normoxic and chronic hypoxic conditions by 2-(4-lodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-1) and flow cytometric analyses. The effects of Vav3 siRNA on cell growth and apoptosis were examined under chronic hypoxia with or without docetaxel treatment. To seek a molecular understanding of Vav3 siRNA induced apoptosis, we analyzed alterations in the growth signaling components in the PI3K/Akt and ERK mediated pathways by immunoblot analysis. Results: Overexpression of Vav3 was observed in LNCaP cells under chronic hypoxia compared with its expression under normoxia. Although the growth rates were reduced in a dose- and time-dependent manner by docetaxel in LNCaP cells under both normoxic and chronic hypoxic conditions, these effects were significantly decreased in LNCaP cells under chronic hypoxia. In addition, we found that docetaxel induced apoptosis following activation of caspase-3 and cleaved poly (ADP-ribose) polymerase, and that the interrupting the Vav3 signaling pathway using siRNA enhanced docetaxel sensitivity of LNCaP cells under chronic hypoxia and led to apoptosis. A profound activation of PI3K/Akt pathway was observed under chronic hypoxic condition. Treatment with Vav3 siRNA showed weak inhibition of Akt phosphorylation and treatment with Vav3 siRNA plus docetaxel strongly inhibited this signaling. Conclusions: Our results showed that Vav3 siRNA enhances docetaxel-induced apoptosis in LNCaP cells under chronic hypoxia and that targeting Vav3 oncogene may have important practical implications for managing hormone refractory prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1651. doi:10.1158/1538-7445.AM2011-1651

Vav3 oncogene is involved in regulation of secretory phospholipase A2-IIa expression in prostate cancer

Our previous study revealed that Vav3 oncogene and secretory phospholipase A2-IIa (sPLA2-IIa) are overexpressed in androgen-independent prostate cancer cells relative to their androgen-dependent counterparts and contribute to development of hormone refractory prostate cancer. Vav3 is a multiple function protein with both signaling molecule and coactivator activities. sPLA2-IIa is a downstream effector of HER/HER2-PI3K-Akt-NF-κB signaling and involved in inflammatory response and tumorigenesis. The aim of the current study was to determine whether Vav3 is involved in up-regulation of sPLA2-IIa expression, given that Vav3 signals in the HER/HER2-elicited pathway. Among 46 prostate cancer specimens examined, Vav3 and sPLA2-IIa are overexpressed in 48 and 83% human prostate cancers, respectively. Vav3 overexpression is significantly associated with a high level expression of sPLA2-IIa. In addition, significant Vav3 nuclear localization is observed in two prostate cancer specimens, supporting a coactivator activity in prostate cancer cells. Further analysis revealed that Vav3 up-regulates expression of the sPLA2-IIa gene at the transcriptional level via HER/HER2-PI3K-Akt-NF-κB signaling. These data revealed that Vav3 overexpression as an additional underlying mechanism contributes to elevated sPLA2-IIa expression in prostate cancer.

418 TARGETING VAV3 ONCOGENE ENHANCES DOCETAXEL SENSITIVITY VIA INDUCTION OF APOPTOSIS IN LNCAP CELLS UNDER CHRONIC HYPOXIA

You have accessJournal of UrologyProstate Cancer: Basic Research1 Apr 2011418 TARGETING VAV3 ONCOGENE ENHANCES DOCETAXEL SENSITIVITY VIA INDUCTION OF APOPTOSIS IN LNCAP CELLS UNDER CHRONIC HYPOXIA Takeo Nomura, Kenichi Hirai, Mutsushi Yamasaki, Fuminori Sato, and Hiromitsu Mimata Takeo NomuraTakeo Nomura Oita, Japan More articles by this author , Kenichi HiraiKenichi Hirai Oita, Japan More articles by this author , Mutsushi YamasakiMutsushi Yamasaki Oita, Japan More articles by this author , Fuminori SatoFuminori Sato Oita, Japan More articles by this author , and Hiromitsu MimataHiromitsu Mimata Oita, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.507AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The Vav family are Rho/Rac guanosine nucleotide exchange factor (GEFs) consisting of three members in mammalian cells and Vav3 enhances AR activity during progression to androgen independence. We previously reported that chronic hypoxic condition (1% oxygen for over six months) induced Vav3 oncogene expression with androgen-independent growth and malignant behavior in LNCaP cells. And overexpression of Vav3 oncogene promoted the growth of LNCaP cells with increased invasion and migration under normoxic condition. The objective of this study was to examine the effect of Vav3 siRNA on cell proliferation and apoptosis in docetaxel-treated LNCaP cells under chronic hypoxic condition. METHODS We analyzed the sensitivity of docetaxel in LNCaP cells under normoxic and chronic hypoxic conditions by 2-(4-lodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-1) analysis. The effects of Vav3 siRNA on cell growth and apoptosis were examined under chronic hypoxia with or without docetaxel treatment by WST-1 and flow cytometric analyses. To seek a molecular understanding of Vav3 siRNA induced apoptosis, we analyzed alterations in the growth signaling components in the PI3K/Akt and ERK mediated pathways and caspase activation by immunoblot analysis. RESULTS Overexpression of Vav3 was observed in LNCaP cells under chronic hypoxia compared with its expression under normoxia. Although the growth rates were reduced in a dose- and time-dependent manner by docetaxel in LNCaP cells under both normoxic and chronic hypoxic conditions, these effects were significantly decreased in LNCaP cells under chronic hypoxia. In addition, we found that docetaxel induced apoptosis following activation of caspase-3, -9 and cleaved poly (ADP-ribose) polymerase, and that the interrupting the Vav3 signaling pathway using siRNA enhanced docetaxel sensitivity of LNCaP cells under chronic hypoxia and led to apoptosis. Although a profound activation of PI3K/Akt pathway was observed under chronic hypoxic condition, treatment with Vav3 siRNA showed weak inhibition of Akt phosphorylation. CONCLUSIONS Our results showed that Vav3 siRNA enhances docetaxel-induced apoptosis in LNCaP cells under chronic hypoxia via activation of caspase cascade and that targeting Vav3 oncogene may have important practical implications for managing castration resistant prostate cancer. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e168 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Takeo Nomura Oita, Japan More articles by this author Kenichi Hirai Oita, Japan More articles by this author Mutsushi Yamasaki Oita, Japan More articles by this author Fuminori Sato Oita, Japan More articles by this author Hiromitsu Mimata Oita, Japan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Progress in Vav3 and breast cancer research

Vav3 oncogene is a member of the Vav family. Vav3 protein contains multiple functional motifs and is involved in cancer development and progression through its role in various cellular signaling processes, including cytoskeleton organization, calcium influx, genetic transcription, cell transformation, proliferation and apoptosis. In addition, Vav3 interacts with estrogen receptor and enhances ERα-mediated signaling axis, therefore plays an important role in breast cancer. Key words: Vav3 oncogene; Breast neoplasms; Signal transduction; Receptors, estrogen

The molecular mechanism of Vav3 oncogene on upregulation of androgen receptor activity in prostate cancer cells

Our previous studies revealed that Vav3 oncogene is overexpressed in human prostate cancer, enhances androgen receptor (AR)-mediated signaling, and may play a role in prostate cancer development and progression. The purpose of this study was to determine the molecular mechanisms responsible for AR activation by Vav3. We found that interaction between N-terminus and C-terminus of AR is essential for its elevated activity stimulated by Vav3. The DH and PH domains of Vav3 are involved in direct interaction with AR. Both cytoplasmic and nuclear levels of AR and Vav3 are elevated and their nuclear localization is further stimulated by DHT in androgen-independent LNCaP-AI cells relative to their parental androgen-dependent LNCaP cells. Vav3 is colocalized with AR, phospho(P)-Akt, and HER2 with a short term stimulation by EGF and DHT. PI3K inhibitor LY294002 blocks colocalization of Vav3 with P-Akt. Consistently, EGF and DHT stimulate Vav3 and AR interaction and enhance PI3K-Akt signaling. Mutation of tyrosines to phenylalanines in the acidic domain or deletion of the SH2 and SH3 domains significantly enhances Vav3 ability for AR activation, while deletion of the DH domain abolishes this activity. Given that an elevated interaction of Vav3 with AR, P-Akt, and HER2 in both cytoplasm and nucleus upon the short-term of DHT stimulation, our data suggest that Vav3 may enhance non-genomic AR activity via PI3K-Akt signaling in addition to AR transcriptional activity and further support a role in androgen-independent growth in prostate cancer.

Targeted Overexpression of Vav3 Oncogene in Prostatic Epithelium Induces Nonbacterial Prostatitis and Prostate Cancer

Our previous study revealed that Vav3 oncogene is overexpressed in human prostate cancer, activates androgen receptor (AR), and stimulates growth in prostate cancer cells. The purpose of this study is to further determine the potential role of Vav3 in prostate cancer development in genetically engineered mouse model. We generated Vav3 transgenic mice by targeted overexpression of a constitutive active Vav3 in the prostatic epithelium. We found that overexpression of Vav3 led to development of mouse prostatic intraepithelial neoplasia and prostate cancer at the age of as early as 3 months. The AR signaling axis and phosphatidylinositol 3-kinase-Akt signaling were elevated in the prostate glands of Vav3 transgenic mice. In addition to prostate cancer, Vav3 transgenic mice developed significant nonbacterial chronic prostatitis in the prostate gland with notable infiltration of lymphomononuclear cells (monocytes, lymphocytes, and plasma cells), which was associated with elevated incidence of prostate cancer. DNA microarray and signaling pathway analysis revealed that the top diseases and disorders were inflammatory diseases and cancer of the prostate gland in Vav3 transgenic mice. In vitro analysis showed that overexpression of Vav3 in prostate cancer cells enhanced nuclear factor-kappaB (NF-kappaB) activity, implicating an underlying mechanism of innate inflammatory response induced by elevated Vav3 activity. These data showed that Vav3 overexpression in the prostate epithelium enhanced both the AR signaling axis and NF-kappaB-mediated pathway, which potentially contributed to the development of nonbacterial prostatitis and prostate cancer.

Vav3 oncogene activates estrogen receptor and its overexpression may be involved in human breast cancer

BackgroundOur previous study revealed that Vav3 oncogene is overexpressed in human prostate cancer, activates androgen receptor, and stimulates growth in prostate cancer cells. The current study is to determine a potential role of Vav3 oncogene in human breast cancer and impact on estrogen receptor a (ERα)-mediated signaling axis.MethodsImmunohistochemistry analysis was performed in 43 breast cancer specimens and western blot analysis was used for human breast cancer cell lines to determine the expression level of Vav3 protein. The impact of Vav3 on breast cancer cell growth was determined by siRNA knockdown of Vav3 expression. The role of Vav3 in ERα activation was examined in luciferase reporter assays. Deletion mutation analysis of Vav3 protein was performed to localize the functional domain involved in ERα activation. Finally, the interaction of Vav3 and ERα was assessed by GST pull-down analysis.ResultsWe found that Vav3 was overexpressed in 81% of human breast cancer specimens, particularly in poorly differentiated lesions. Vav3 activated ERα partially via PI3K-Akt signaling and stimulated growth of breast cancer cells. Vav3 also potentiated EGF activity for cell growth and ERα activation in breast cancer cells. More interestingly, we found that Vav3 complexed with ERα. Consistent with its function for AR, the DH domain of Vav3 was essential for ERα activation.ConclusionVav3 oncogene is overexpressed in human breast cancer. Vav3 complexes with ERα and enhances ERα activity. These findings suggest that Vav3 overexpression may aberrantly enhance ERα-mediated signaling axis and play a role in breast cancer development and/or progression.

Vav3 Oncogene Is Overexpressed and Regulates Cell Growth and Androgen Receptor Activity in Human Prostate Cancer

The purpose of this research was to investigate the role of Vav3 oncogene in human prostate cancer. We found that expression of Vav3 was significantly elevated in androgen-independent LNCaP-AI cells in comparison with that in their androgen-dependent counterparts, LNCaP cells. Vav3 expression was also detected in other human prostate cancer cell lines (PC-3, DU145, and 22Rv1) and, by immunohistochemistry analysis, was detected in 32% (26 of 82) of surgical specimens of human prostate cancer. Knockdown expression of Vav3 by small interfering RNA inhibited growth of both androgen-dependent LNCaP and androgen-independent LNCaP-AI cells. In contrast, overexpression of Vav3 promoted androgen-independent growth of LNCaP cells induced by epidermal growth factor. Overexpression of Vav3 enhanced androgen receptor (AR) activity regardless of the presence or absence of androgen and stimulated the promoters of AR target genes. These effects of Vav3 could be attenuated by either phosphatidylinositol 3-kinase (PI3K) inhibitors or dominant-negative Akt and were enhanced by cotransfection of PI3K. Moreover, phosphorylation of Akt was elevated in LNCaP cells overexpressing Vav3, which could be blocked by PI3K inhibitors. Finally, we ascertained that the DH domain of Vav3 was responsible for activation of AR. Taken together, our data show that overexpression of Vav3, through the PI3K-Akt pathway, inappropriately activates AR signaling axis and stimulates cell growth in prostate cancer cells. These findings suggest that Vav3 overexpression may be involved in prostate cancer development and progression.