Growth Factor Receptor-bound Protein 7 Research Articles

Aquaporin-1 facilitates proliferation and invasion of gastric cancer cells via GRB7-mediated ERK and Ras activation

ABSTRACT Gastric cancer, one of the most common malignant tumors of the digestive tract, is devoid of effective treatment owing to its highly invasive ability. Aquaporins (AQPs), transmembrane water channel proteins, has been shown to be involved in the malignancy of gastric cancer. This study aims to investigate the pathophysiological roles of AQP-1 in gastric cancer. We first demonstrated quantitative real-time polymerase chain reaction analysis and found up-regulation of AQP-1 in gastric cancer cell lines. Additionally, silence of AQP-1 inhibited cell proliferation via decrease of proliferating cell nuclear antigen (PCNA) and minichromosome maintenance complex component 2 (MCM2). Moreover, migration and invasion of gastric cancer cells were also suppressed by the interference of AQP-1. However, the tumorigenic mechanism of AQP-1 on gastric cancer is yet to be found. We demonstrated western blot analysis and found that knockdown of AQP-1 decreased protein expression of phospho (p)-GRB7 (growth factor receptor-bound protein 7) and led to a remarkable reduction of p-extracellular signal-regulated kinase (ERK) via inactivation of RAS. In general, our findings indicated that AQP-1 facilitates proliferation and invasion of gastric cancer cells via GRB7-mediated ERK and Ras activation, illuminating a novel AQP-1-RAS/ERK molecular axis as regulator in gastric cancer progression and suggesting potential implications in the treatment of gastric cancer.

Growth factor receptor bound protein-7 regulates proliferation, cell cycle, and mitochondrial apoptosis of thyroid cancer cells via MAPK/ERK signaling.

It is of great significance to explore the molecular mechanism of thyroid cancer (TC) pathogenesis for its improvement and therapy. Growth factor receptor bound protein-7 (GRB7) has been regarded as an important regulatory gene in the developments of various malignant tumors. Our study aimed to illustrate the role of GRB7 in the TC pathology mechanism. Firstly, GRB7 was found to be significantly upregulated in 49 cases of TC tissues and 5 TC cell lines by using real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting. Silencing GRB7 with siRNA dramatically inhibited proliferation and induced cell cycle arrest in TC cells. Besides, GRB7 silence resulted in the decrease of adenosine triphosphate content, glucose uptake, and lactose production in TC cells and attenuated the activity and expression of mitochondrial respiratory complex. We also demonstrated that GRB7 downregulation increased the levels of Bax and caspase 3, and inhibited the expression of Bcl-2, suggesting the induced mitochondrial apoptosis. More importantly, our study proved that mitogen-activated protein kinase/extracellular-regulated protein kinases (MAPK/ERK) signaling played a crucial role in the regulation of GRB7 on TC cell functions. In general, the present research verified that GRB7 was upregulated during TC development and modulated the proliferation, cell cycle, and mitochondrial apoptosis of TC cells by activating MAPK/ERK pathway. This may provide a novel target for the therapeutic strategy of TC.

Abstract P4-04-05: circHEACA promotes anti-HER2 drug resistance by HEACA-GRB7/AKT axis in HER2+ breast cancer patients

Abstract Background: Some HER2-positive (HER2+) breast cancer patient are resistant to anti-HER2 therapy, and the potential reasons of anti-HER2 drug resistance remain unclear. It has been demonstrated that circRNAs play an important role in breast cancer progression, however, the role of circRNAs in anti-Her2 drug resistance remains unknown. In our study, we found and identified a HER2-related circRNA that is associated with malignant progression of HER2 positive breast cancer and preliminary explore their potential mechanisms and clinical significance. Materials and Methods: To identify the HER2-related circRNAs, the deep circRNAs RNA sequencing was performed between the HER2 positive and HER2 negative human breast cancer tissues, and then selected the candidate circRNAs using qPCR to verify the expression level. K-M model was used to define the prognostic performance of circRNA candidates in a breast cancer patient cohort with anti-HER2 drug treatment(N=120). Divergent primers assay and actinomycin D experiments were used to identify the circular features of circRNA candidates. To detect the biological function in breast cancer cells, we knocked-down or over-expressed the circular RNA by siRNA and plasmid transfection. We conducted CHiRP (Chromatin Isolation by RNA Purification) assay to pull down protein complex using biotinylated circRNA probe, and performed mass spectrometric to find out the potential binding protein. Western blot and immunofluorescence (IF) verified that circRNA interacted the protein candidate Results: In this study, we identified a HER2 -Associated CircRNA (named HEACA), and found that divergent primers were amplified in cDNA but not gDNA. Convergent primers amplified in the both cDNA and gDNA. As expected, HEACA was more stable than its linear mRNA when both of them were treated by actinomycin D. Clinical data indicated that HER2+ breast cancer patients with high expression level of HEACA was significantly associated with larger tumour size, more much lymphatic metastasis and higher ki67 index. Kaplan-Meier survival curves showed that HER2+ breast cancer patients with high HEACA who received anti-HER2 therapy has shorter disease-free survival (DFS) and overall survival (OS) than those with low HEACA. Next, we found that know-down HEACA significantly inhibited the proliferation of HER2 positive breast cancer cells through cell variability assay and colony formation, while over-express HEACA highly increased cell proliferation. However, neither know-down nor over-express resulted in affecting the biological function in MCF-7 cells. CircRNA pull down assay and mass spectrometric indicated HEACA may bind to Growth factor receptor-bound protein 7(GRB7). Western blot and IF showed that the protein expression of GRB7 increased or decreased by knocking down or over-express HEACA. Furthermore, we demonstrated that upregulated HEACA promoted breast cancer progression via GRB7/AKT axis in HER2+ cell lines, consequently resulted in a malignant progression of breast cancer cells in vitro and in vivo. Conclusions: HEACA-GRB7/AKT axis plays a critical role in HER2+ breast cancer progression and may be a predictive biomarker for anti-her2 therapy for HER2+ BC patients. Citation Format: Yun Ling, Liang Gehao, Zihao Liu, Zhenluan Tian, Wenjing Zhong, Wanyi Lin, Erwei Song, Gong Chang. circHEACA promotes anti-HER2 drug resistance by HEACA-GRB7/AKT axis in HER2+ breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-04-05.

Upregulated GRB7 promotes proliferation and tumorigenesis of Bladder Cancer via Phospho-AKT Pathway.

Growth factor receptor-bound protein 7 (GRB7) has been found closely related to the occurrence and development of various tumors, but its function in bladder cancer has not yet been elucidated. The study is aiming at investigating the expression and function of GRB7 in bladder cancer. The Cancer Genome Atlas (TCGA) database was selected to analyze mRNA levels of GRB7 in bladder cancer. RT-qPCR and Western blot were conducted to detect the expression of GRB7 in normal bladder epithelial cells, seven bladder cancer cell lines and eight pairs of malignant/nonmalignant bladder tissues. The role of GRB7 in tumor proliferation and tumorigenesis was explored by establishing stable cells, in vitro cell experiments and in vivo xenograft models. The molecular regulation mechanism of GRB7 in bladder cancer was investigated by treatment with AKT inhibitor. GRB7 mRNA was upregulated in bladder cancer samples compared with that in normal tissue samples. Overexpressing GRB7 significantly promoted the proliferation and tumorigenesis of bladder cancer. However, silencing GRB7 played the retarding part. GRB7 promoted G1/S transition by activating the AKT pathway. Our results indicate that GRB7 plays an important role in promoting proliferation and tumorigenesis of bladder cancer.

Methylation-associated silencing of miR-193a-3p promotes ovarian cancer aggressiveness by targeting GRB7 and MAPK/ERK pathways.

Human growth factor receptor-bound protein-7 (GRB7) is a pivotal mediator involved in receptor tyrosine kinase signaling and governing diverse cellular processes. Aberrant upregulation of GRB7 is frequently associated with the progression of human cancers. However, the molecular mechanisms leading to the upregulation of GRB7 remain largely unknown. Here, we propose that the epigenetic modification of GRB7 at the post-transcriptional level may be a crucial factor leading to GRB7 upregulation in ovarian cancers. Methods: The upstream miRNA regulators were predicted by in silico analysis. Expression of GRB7 was examined by qPCR, immunoblotting and immunohistochemical analyses, while miR-193a-3p levels were evaluated by qPCR and in situ hybridization in ovarian cancer cell lines and clinical tissue arrays. MS-PCR and pyrosequencing analyses were used to assess the methylation status of miR-193a-3p. Stable overexpression or gene knockdown and Tet-on inducible approaches, in combination with in vitro and in vivo tumorigenic assays, were employed to investigate the functions of GRB7 and miR-193a-3p in ovarian cancer cells. Results: Both miR-193a-3p and its isoform, miR-193b-3p, directly targeted the 3' UTR of GRB7. However, only miR-193a-3p showed a significantly inverse correlation with GRB7-upregulated ovarian cancers. Epigenetic studies revealed that methylation-mediated silencing of miR-193a-3p led to a stepwise decrease in miR-193a-3p expression from low to high-grade ovarian cancers. Intriguingly, miR-193a-3p not only modulated GRB7 but also ERBB4, SOS2 and KRAS in the MAPK/ERK signaling pathway to enhance the oncogenic properties of ovarian cancer cells in vitro and in vivo. Conclusion: These findings suggest that epigenetic silencing of miR-193a-3p by DNA hypermethylation is a dynamic process in ovarian cancer progression, and miR-193a-3p may be explored as a promising miRNA replacement therapy in this disease.

GRB7 Expression and Correlation With HER2 Amplification in Invasive Breast Carcinoma.

Growth factor receptor-bound protein 7 (GRB7) gene is located adjacent to the HER2 gene on the 17q12-21 amplicon, is often coamplified with HER2 in a subset of breast cancers, and has been implicated in resistance to anti-HER2 and antiestrogen therapy. This study investigated the correlation of GRB7 expression by immunohistochemistry with HER2 expression, HER2 amplification, increased chromosome 17 copy number, and other prognostic and predictive factors in invasive breast cancer, including histologic grade, pathologic stage, and ER, PR, and p53 status. Paraffin-embedded samples of 188 invasive breast carcinomas with documented HER2, ER, and PR testing were collected and divided into 3 groups: cases positive for HER2 overexpression/gene amplification (n=60), negative for HER2 overexpression (n=97), and cases with increased chromosome 17 copy number without HER2 amplification (n=31). GRB7 expression was evaluated on all 188 cases. In addition, p53 immunohistochemistry was performed on 13 HER2+/GRB7+ cases and 39 HER2+/GRB7- cases. GRB7 expression correlated strongly with HER2 overexpression. GRB7 expression was present in 20/60 (33.33%) of HER2+ cases, compared with 1/97 (1.03%) HER2- cases, and 1/31 (3.22%) increased chromosome 17 copy number cases (P<0.0001). In HER2+ cases, GRB7 expression was found to correlate significantly with a greater degree of HER2 amplification. The mean±SEM HER2 copy number was 21.14±2.59 in GRB7+ cases, compared with 9.8±1.38 in GRB7- cases (P=0.0001). GRB7 expression correlated significantly with ER negativity (P=0.012) and p53 positivity (P=0.03). GRB7 expression did not correlate with histologic grade, pathologic stage, or PR expression. Our data shows that GRB7 expression in invasive breast cancer correlates with markers of a more aggressive phenotype, including HER2 overexpression, a greater degree of HER2 amplification, ER negativity, and p53 positivity.

Abstract LB-324: Methylation-associated silencing of miR-193a-3p promotes ovarian cancer aggressiveness via targeting GRB7

Abstract The human growth factor receptor-bound protein-7 (GRB7) is a pivotal mediator involved in receptor tyrosine kinase signaling and governing diverse cellular processes. We and others have reported that GRB7 is frequently upregulated and associated with the progression of human cancers. Clinicopathological analysis has shown that the overexpressed GRB7 is correlated with high grade and metastatic ovarian cancers. However, the molecular mechanisms leading to the upregulation of GRB7 remain largely unknown. In this study, we propose that the epigenetic modification of GRB7 at the post-transcriptional level may be a crucial factor leading to GRB7 upregulation in ovarian cancers. We found that the protein level of GRB7 was much higher than its mRNA levels in a subset of ovarian cancer cell lines, indicating aberrant post-transcriptional alterations in GRB7. Using an in silico study, we identified miR-193a-3p and its isoform, miR-193b-3p, by specifically targeting the conserved site (GGCCAGT) at position 332-338 in the 3’ UTR (length: 387) of the human GRB7 gene. QPCR and western blot analyses revealed that only the expression levels of miR-193a-3p but not miR-193b-3p were inversely correlated in ovarian cancer cell lines accompanied with high levels of GRB7 protein levels. Further biochemical analyses using luciferase reporter assays in combination with mutational analyses identified miR-193a-3p specifically targeting GRB7 3’UTR, confirming miR-193a-3p, instead of its isoform miR-193b-3p, has a more important role in GRB7 post-transcriptional regulation in ovarian cancer cells. Constitutive expression or knockdown of miR-193a-3p could significantly alter GRB7 expression, as well as oncogenic capacities of ovarian cancer cells such as cell growth, cell migration and cell invasion. Importantly, we observed that there was a significant stepwise decrease of miR-193a-3p expression from low to high grade ovarian cancers, and was inversely correlated with GRB7 expressions. Intriguingly, treatment with the DNA methyl transferase inhibitor (5’-Aza-dc) could restore the expression of miR-193a-3p, suggesting the epigenetic inhibition of miR-193a-3p is clinically relevant. Importantly, such epigenetic alteration may be the clue leading to overexpression of GRB7 in ovarian cancer cells. Taken together, our findings suggest that epigenetically silencing of miR-193a-3p upregulates GRB7 and contribute to ovarian cancer aggressiveness in tumor progression. Citation Format: Kangmei Chen, Hextan YS Ngan, David W. Chan. Methylation-associated silencing of miR-193a-3p promotes ovarian cancer aggressiveness via targeting GRB7 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-324. doi:10.1158/1538-7445.AM2017-LB-324

HER-2 gene amplification in human breast cancer without concurrent HER-2 over-expression

BackgroundTesting for human epidermal growth factor receptor-2 (HER-2) in breast cancer is performed by either immunohistochemistry (IHC) or in situ hybridization (ISH). The growth factor receptor-bound protein-7 (GRB7) gene is in close proximity to HER-2 on chromosome 17q11-12 and codes a signal transduction molecule shown to be an independent adverse marker in breast cancer.MethodsHER-2 and GRB7 protein expression from 613 frozen breast tumors was determined by Western analysis. HER-2 protein results were confirmed with IHC. Commercial HER-2 FISH was performed on a subset of tumors with multi-probe FISH used to assess the extent of HER-2 gene amplification. mRNA expression was determined by Multi-plex RT-PCR.ResultsSeven tumors with GRB7 protein over-expression scored HER-2 FISH amplified but had no HER-2 protein over-expression. Four of the 7 tumors showed elevated GRB7 but not HER-2 mRNA over-expression. The breast cancer cell line HCC3153 did not over-express HER-2 protein but showed HER-2 FISH amplification of a limited segment around the HER-2 gene. Ten breast cancer tumors from the TCGA database had gene copy number increases around HER-2 without HER-2 mRNA or protein over-expression.ConclusionsA subset of human breast cancers that test positive with FISH for HER-2 gene amplification do not over-express HER-2 protein. One mechanism for this discordance is the incomplete amplification of the smallest HER-2 region of chromosome 17q11-12, which includes GRB7. HER-2 gene amplification without protein over-expression is clinically significant because patients with such tumors are unlikely to benefit from HER-2 targeted therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-386) contains supplementary material, which is available to authorized users.

Genome Wide Proteomics of ERBB2 and EGFR and Other Oncogenic Pathways in Inflammatory Breast Cancer

In this study we selected three breast cancer cell lines (SKBR3, SUM149 and SUM190) with different oncogene expression levels involved in ERBB2 and EGFR signaling pathways as a model system for the evaluation of selective integration of subsets of transcriptomic and proteomic data. We assessed the oncogene status with reads per kilobase per million mapped reads (RPKM) values for ERBB2 (14.4, 400, and 300 for SUM149, SUM190, and SKBR3, respectively) and for EGFR (60.1, not detected, and 1.4 for the same 3 cell lines). We then used RNA-Seq data to identify those oncogenes with significant transcript levels in these cell lines (total 31) and interrogated the corresponding proteomics data sets for proteins with significant interaction values with these oncogenes. The number of observed interactors for each oncogene showed a significant range, e.g., 4.2% (JAK1) to 27.3% (MYC). The percentage is measured as a fraction of the total protein interactions in a given data set vs total interactors for that oncogene in STRING (Search Tool for the Retrieval of Interacting Genes/Proteins, version 9.0) and I2D (Interologous Interaction Database, version 1.95). This approach allowed us to focus on 4 main oncogenes, ERBB2, EGFR, MYC, and GRB2, for pathway analysis. We used bioinformatics sites GeneGo, PathwayCommons and NCI receptor signaling networks to identify pathways that contained the four main oncogenes and had good coverage in the transcriptomic and proteomic data sets as well as a significant number of oncogene interactors. The four pathways identified were ERBB signaling, EGFR1 signaling, integrin outside-in signaling, and validated targets of C-MYC transcriptional activation. The greater dynamic range of the RNA-Seq values allowed the use of transcript ratios to correlate observed protein values with the relative levels of the ERBB2 and EGFR transcripts in each of the four pathways. This provided us with potential proteomic signatures for the SUM149 and 190 cell lines, growth factor receptor-bound protein 7 (GRB7), Crk-like protein (CRKL) and Catenin delta-1 (CTNND1) for ERBB signaling; caveolin 1 (CAV1), plectin (PLEC) for EGFR signaling; filamin A (FLNA) and actinin alpha1 (ACTN1) (associated with high levels of EGFR transcript) for integrin signalings; branched chain amino-acid transaminase 1 (BCAT1), carbamoyl-phosphate synthetase (CAD), nucleolin (NCL) (high levels of EGFR transcript); transferrin receptor (TFRC), metadherin (MTDH) (high levels of ERBB2 transcript) for MYC signaling; S100-A2 protein (S100A2), caveolin 1 (CAV1), Serpin B5 (SERPINB5), stratifin (SFN), PYD and CARD domain containing (PYCARD), and EPH receptor A2 (EPHA2) for PI3K signaling, p53 subpathway. Future studies of inflammatory breast cancer (IBC), from which the cell lines were derived, will be used to explore the significance of these observations.

Correlation Between HER2 Amplification and Growth Factor Receptor-Bound Protein-7 Expression in Invasive Breast Carcinoma

Correlation Between HER2 Amplification and Growth Factor Receptor-Bound Protein-7 Expression in Invasive Breast Carcinoma

Abstract P4-08-03: False Positive HER-2 Testing by Fluorescence In Situ Hybridization in Human Breast Cancer

Abstract Background: Testing for human epidermal growth factor receptor-2 (HER-2) is routinely performed after breast cancer diagnosis by either immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH). FISH is more accurate and reproducible, often considered the gold standard, and a more reliable predictor of a patient's response to HER-2 directed therapies in clinical practice. The growth factor receptor-bound protein-7 gene (GRB7) encodes a multi-domain signal transduction molecule located in close proximity to HER-2 on chromo some 17q11-12 and has been shown to be an independent adverse prognostic marker in breast cancer. Methods: We performed western blotting analysis of protein extracts from 563 annotated frozen breast tumors, collected from 1988 - 1998. GRB7 and HER-2 bands were assigned low or high values compared to specific protein controls, and tubulin bands. HER-2 FISH was performed on a subset of these tumors using an FDA approved Path Vysion kit on 4 μm frozen sections. HER-2 and chromosome 17 centromere (CEP17) signals were enumerated according to ASCO/CAP guidelines. Results: Sixty-six tumors (11.5%) over-expressed HER-2 and GRB7 proteins by Western analysis, 66 (11.5%) over-expressed HER-2 but not GRB7, and 30 (5.5%) over-expressed GRB7 but not HER-2. All 32 tumors (32/32) submitted to FISH analysis that over-expressed both HER-2 and GRB7 proteins demonstrated HER-2 gene amplification, while only one out of thirty-five (1/35) tumors that over-expressed HER-2 without GRB7 protein over-expression were HER-2 amplified. Interestingly, 7 of 28 tumors over-expressing GRB7 but not HER-2 protein were amplified for the HER-2 gene. Clinical laboratory HER-2 IHC testing confirmed the absence of HER-2 protein over-expression in all 7 of these tumors. Conclusions: Our study demonstrates that about ten percent of human breast cancers that test positive with FISH for HER-2 gene amplification do not over-express HER-2 protein, which may influence sensitivity to HER-2 directed therapy. All tumors that show false positive HER-2 gene amplification over-express GRB7 protein, suggesting the presence of GRB7 driven gene amplification in these tumors. Given that the HER-2 FISH probe contains GRB7 sequences, it is possible that HER-2 FISH false positivity may reflect GRB7 gene amplification. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-08-03.

Expression profiling of formalin-fixed paraffin-embedded primary breast tumors using cancer-specific and whole genome gene panels on the DASL®platform

BackgroundThe cDNA-mediated Annealing, extension, Selection and Ligation (DASL) assay has become a suitable gene expression profiling system for degraded RNA from paraffin-embedded tissue. We examined assay characteristics and the performance of the DASL 502-gene Cancer Panelv1 (1.5K) and 24,526-gene panel (24K) platforms at differentiating nine human epidermal growth factor receptor 2- positive (HER2+) and 11 HER2-negative (HER2-) paraffin-embedded breast tumors.MethodsBland-Altman plots and Spearman correlations evaluated intra/inter-panel agreement of normalized expression values. Unequal-variance t-statistics tested for differences in expression levels between HER2 + and HER2 - tumors. Regulatory network analysis was performed using Metacore (GeneGo Inc., St. Joseph, MI).ResultsTechnical replicate correlations ranged between 0.815-0.956 and 0.986-0.997 for the 1.5K and 24K panels, respectively. Inter-panel correlations of expression values for the common 498 genes across the two panels ranged between 0.485-0.573. Inter-panel correlations of expression values of 17 probes with base-pair sequence matches between the 1.5K and 24K panels ranged between 0.652-0.899. In both panels, erythroblastic leukemia viral oncogene homolog 2 (ERBB2) was the most differentially expressed gene between the HER2 + and HER2 - tumors and seven additional genes had p-values < 0.05 and log2 -fold changes > |0.5| in expression between HER2 + and HER2 - tumors: topoisomerase II alpha (TOP2A), cyclin a2 (CCNA2), v-fos fbj murine osteosarcoma viral oncogene homolog (FOS), wingless-type mmtv integration site family, member 5a (WNT5A), growth factor receptor-bound protein 7 (GRB7), cell division cycle 2 (CDC2), and baculoviral iap repeat-containing protein 5 (BIRC5). The top 52 discriminating probes from the 24K panel are enriched with genes belonging to the regulatory networks centered around v-myc avian myelocytomatosis viral oncogene homolog (MYC), tumor protein p53 (TP53), and estrogen receptor α (ESR1). Network analysis with a two-step extension also showed that the eight discriminating genes common to the 1.5K and 24K panels are functionally linked together through MYC, TP53, and ESR1.ConclusionsThe relative RNA abundance obtained from two highly differing density gene panels are correlated with eight common genes differentiating HER2 + and HER2 - breast tumors. Network analyses demonstrated biological consistency between the 1.5K and 24K gene panels.

GRB7 protein over-expression and clinical outcome in breast cancer

The growth factor receptor-bound protein-7 gene (GRB7) encodes a multi-domain signal transduction molecule. The purpose of this study was to examine the clinical significance of GRB7 protein expression in human breast cancer. Western blotting analysis of protein extracts from 563 annotated frozen breast tumors was performed. Expression status of GRB7 and HER-2 was correlated with clinical covariates and outcomes. Cox proportional hazards were used to identify factors associated with breast cancer-free interval. The median follow-up was 71 months. P values <0.05 were considered statistically significant (two-sided). A discrepancy between HER-2 and GRB7 protein over-expression was observed. GRB7 protein over-expression was associated with negative estrogen and progesterone receptor status, higher tumor grade, larger primary tumor size, (more) axillary lymph node involvement, higher clinical stage, and shortened breast cancer-free interval. HER-2 protein over-expression was associated only with higher tumor grade. Multi-variate analysis revealed that GRB7 protein over-expression was an independent adverse prognostic factor for breast cancer-free interval (hazard ratio 1.69, 95% confidence interval 1.07-2.67; P = 0.024). The same was true of the subset of patients who did not receive any adjuvant systemic therapy (hazard ratio 1.68, 95% confidence interval 1.16-2.31; P = 0.0055). Using FISH analysis, 32/32 (100%; 95% CI 89-100%) tumors which over-expressed both HER-2 and GRB7 proteins and 1/35 (3%; 95% CI 0-15%) tumors with HER-2 but no GRB7 protein over-expression with Western blotting analysis demonstrated HER-2 gene amplification. GRB7 protein over-expression is an independent adverse prognostic factor in human breast cancer.

Growth factor receptor-bound protein-7 (Grb7) as a prognostic marker and therapeutic target in breast cancer

BackgroundGrowth factor receptor-bound protein-7 (Grb7) is an adapter-type signaling protein recruited to various tyrosine kinases, including HER2/neu. Grb7-specific inhibitors are in early development. As with other targeted therapies, response to therapy might be associated with target expression. Materials and methodsTissue microarrays containing 638 primary breast cancer specimens with 15-year patient follow-up were employed to assess Grb7 expression using our Automated QUantitative Analysis method; cytokeratin defines pixels as breast cancer (tumor mask) within the histospot, and Grb7 expression within the mask is measured with Cy5-conjugated antibodies. ResultsHigh Grb7 expression was strongly associated with decreased survival in the entire cohort and in the node-positive subset (P=0.0034 and P= 0.0019, respectively). On multivariable analysis, it remained an independent prognostic marker (P =0.01). High Grb7 was strongly associated with high HER2/neu, and coexpression of these molecules was associated with worse prognosis than HER2/neu overexpression alone. ConclusionsHigh Grb7 defines a subset of breast cancer patients with decreased survival, indicating that Grb7 might be a valuable prognostic marker and drug target. Coexpression with HER2/neu indicates that cotargeting these molecules might be an effective approach for treating HER2/neu-positive breast cancers. Future studies using Grb7-targeting agents should include assessment of Grb7 levels.

Tyrosine Phosphorylation of Growth Factor Receptor-bound Protein-7 by Focal Adhesion Kinase in the Regulation of Cell Migration, Proliferation, and Tumorigenesis

We have previously reported that growth factor receptor-bound protein-7 (Grb7), an Src-homology 2 (SH2)-containing adaptor protein, enables interaction with focal adhesion kinase (FAK) to regulate cell migration in response to integrin activation. To further elucidate the signaling events mediated by FAK*Grb7 complexes in promoting cell migration and other cellular functions, we firstly examined the phosphorylated tyrosine site(s) of Grb7 by FAK using an in vivo mutagenesis. We found that FAK was capable of phosphorylating at least 2 of 12 tyrosine residues within Grb7, Tyr-188 and Tyr-338. Moreover, mutations converting the identified Tyr to Phe inhibited integrin-dependent cell migration as well as impaired cell proliferation but not survival compared with the wild-type control. Interestingly, the above inhibitory effects caused by the tyrosine phosphorylation-deficient mutants are probably attributed to their down-regulation of phospho-Tyr-397 of FAK, thereby implying a mechanism by competing with wild-type Grb7 for binding to FAK. Consequently, these tyrosine phosphorylation-deficient mutants evidently altered the phospho-Tyr-118 of paxillin and phosphorylation of ERK1/2 but less on phospho-Ser-473 of AKT, implying their involvement in the FAK*Grb7-mediated cellular functions. Additionally, we also illustrated that the formation of FAK*Grb7 complexes and Grb7 phosphorylation by FAK in an integrin-dependent manner were essential for cell migration, proliferation and anchorage-independent growth in A431 epidermal carcinoma cells, indicating the importance of FAK*Grb7 complexes in tumorigenesis. Our data provide a better understanding on the signal transduction event for FAK*Grb7-mediated cellular functions as well as to shed light on a potential therapeutic in cancers.

GRB7 and HER2 protein overexpression and breast cancer outcome

11102 Background: The growth factor receptor-bound protein-7 gene (GRB7) encodes a multi-domain signal transduction molecule and is located in close proximity to human epidermal growth factor receptor 2 (HER2) on chromosome 17q11–12. This study examines the roles of GRB7 protein in human breast cancer. Methods: We performed western blotting analysis of protein extracts from 563 annotated frozen breast tumors, collected from 1988 - 1998. GRB7 and HER2 bands were assigned low or high values compared to specific protein controls, and tubulin bands. Chi-square tests were used to test the hypothesis that there was no association between expression status of GRB7 or HER2 with clinical covariates and outcomes. Univariate Cox regression was performed to identify risk factors and Cox proportional hazards backward step model for variable selection to identify independent predictors of progression free survival. All P values were two sided. P values less than 0.05 were considered statistically significant. HER 2 gene amplification status was determined by fluorescence in situ hybridization (FISH). Results: GRB7 protein over-expression was associated with negative estrogen (&lt; 5 fmole/mg protein) and progesterone receptor (&lt; 10fmole/mg protein) status, higher grade (1, 2, or 3), larger primary tumor size (&lt; 2.0 vs. &gt; 2.0 cm), (more) axillary lymph node involvement (continuous), higher clinical stage (1, 2, 3, or 4) and shortened progression free survival (months). We found a discrepancy in HER2 and GRB7 protein over-expression. Isolated GRB7 protein over-expression correlated with inferior progression free survival, while HER2 protein over-expression without GRB7 protein over-expression did not. Multivariate analysis revealed that GRB7 over-expression was an independent predictor of progression free survival (hazard ratio 1.69: 95% confidence interval, 1.073 - 2.672; P = 0.0236). All 18 tumors submitted to FISH analysis that over-expressed both HER2 and GRB7 proteins and no tumors (0 / 10) with HER2 but no GRB7 protein over-expression demonstrated HER2 gene amplification. Conclusions: GRB7 protein over-expression is an independent adverse prognostic factor in breast cancer. No significant financial relationships to disclose.

GRB-7 facilitates HER-2/Neu-mediated signal transduction and tumor formation

Growth factor receptor-bound protein-7 (GRB-7), an adaptor molecule, can interact with multiple signal transduction molecules. GRB-7 is amplified concurrently with HER-2/Neu in most, if not all, of breast cancer with chromosome 17q11-21 amplification. GRB-7 gene amplification is associated with RNA over-expression. We show GRB-7 protein is over-expressed by immunoblotting in breast cancer cell lines and primary breast tumors with HER-2/Neu protein over-expression. Over-expression of GRB-7 in MCF-7 breast cancer cells that over-express HER-2/Neu leads to activation of tyrosine phosphorylation of HER-2/Neu. Knockdown of GRB-7 expression in SKBR-3 breast cancer cells with naturally occurring HER-2/Neu gene amplification decreases tyrosine phosphorylation of HER-2/Neu. Activation of HER-2/Neu phosphorylation is associated with increase in tyrosine phosphorylation of phosphoinositide-specific lipase C-gamma-1 (PLC-gamma-1) and recruitment of PLC-gamma-1 to HER-2/Neu protein molecule. Activation of downstream protein kinase C (PKC) pathway is evidenced by increase in the phosphorylation of a common PKC substrate-myristoylated alanine-rich protein kinase C substrate (MARCKS). In addition, over-expression of GRB-7 in MCF-7 breast cancer cells that over-express HER-2/Neu leads to activation of AKT phosphorylation. Knockdown of GRB-7 expression in MB-453 and SKBR-3 breast cancer cells results in decrease in AKT phosphorylation. GRB-7 over-expression therefore facilitates activation of phosphorylation of HER-2/Neu and AKT in breast cancer cells with HER-2/Neu over-expression. GRB-7 over-expression in MCF-7 cells over-expressing HER-2/Neu leads to morphologic change of cells and promotes tumor xenograft growth in nude mice. GRB-7 over-expression therefore plays pivotal roles in activating signal transduction and promoting tumor growth in breast cancer cells with chromosome 17q11-21 amplification.

Identification of genes with correlated patterns of variations in DNA copy number and gene expression level in gastric cancer

To identify DNA copy number changes that had a direct influence on mRNA expression in gastric cancer, cDNA microarray-based comparative genomic hybridization (aCGH) and gene expression profiling were performed using 17 K cDNA microarrays. A set of 158 genes showing Pearson correlation coefficients over 0.6 between DNA copy number changes and mRNA expression level variations was selected. In an independent gene expression profiling of 60 tissue samples, the 158 genes were able to distinguish most of the normal and tumor tissues in an unsupervised hierarchical clustering, suggesting that the differential expression patterns displayed by this specific group of genes are most likely based on the gene copy number changes. Furthermore, 43 statistically significant ( P < 0.01) genes were selected that correctly distinguished all of the tissue samples. The copy number changes detected by aCGH can be verified by fluorescence in situ hybridization and real-time polymerase chain reaction. The selected genes include those that were previously identified as being tumor suppressors or deleted in various tumors, including GATA binding protein 4 (GATA4), monoamine oxidase A (MAOA), cyclin C (CCNC), and oncogenes including malignant fibrous histiocytoma amplified sequence 1 (MFHAS1/MASL1), high mobility group AT-hook 2 (HMGA2), PPAR binding protein (PPARBP), growth factor receptor-bound protein 7 (GRB7), and TBC1 (tre-2, BUB2, cdc16) domain family, member 1 (TBC1D1).