9232

PTTG1

pituitary tumor-transforming 1;PTTG1;pituitary tumor-transforming 1

ESP1-associated protein 1|pituitary tumor-transforming gene 1 protein|securin|tumor-transforming protein 1

5q35.1

protein-coding

Human pituitary tumour-transforming gene 1 (hPTTG1) is an oncogenic transcription factor that is overexpressed in many tumour types, especially tumours with metastatic abilities. However, how hPTTG1 overexpression drives metastasis is not yet clear. As a transcription factor, hPTTG1 may promote metastasis by activating target genes that are involved in the metastatic process. Here, we showed that Rho guanine nucleotide exchange factor-H1 (GEF-H1) was transcriptionally activated by hPTTG1, thereby promoting breast cancer metastasis. Luciferase reporter analyses and chromatin immunoprecipitation (ChIP) assays showed that hPTTG1 directly bound and activated the GEF-H1 gene promoter. In this study, RNA interference-mediated knockdown of hPTTG1 in highly metastatic breast tumour cells decreased GEF-H1 expression and RhoA activation, thereby reducing cell motility and invasion, and interfering with cytoskeletal remodelling in vitro, and impairing the tumour metastasis in vivo. The restoration of GEF-H1 expression in hPTTG1-knockdown cells rescued the hPTTG1-knockdown effects on cytoskeletal changes in vitro and tumour metastasis in vivo. Conversely, ectopic expression of hPTTG1 in non-metastatic breast tumour cells induced cytoskeletal rearrangements, and allowed these cells to metastasise in a mouse model by orthotopic implantation. In human tumour samples, hPTTG1 expression was also correlated to GEF-H1 expression in aggressive breast carcinoma. Altogether, these findings definitively establish a role for hPTTG1 in activating the GEF-H1/RhoA pathway as a newly identified mechanism in breast cancer metastasis.

Pituitary tumor-transforming gene (PTTG), the index mammalian securin, is abundantly expressed in several tumors and regulates tumor growth and progression. Molecular mechanisms elucidating PTTG regulation and actions remain elusive. Here, we provide evidence that PTTG acts as a signal transducer and activator of transcription factor 3 (STAT3) target gene. Total STAT3 and Tyr705 phosphorylated STAT3 were concordantly expressed with PTTG in human colorectal tumors (n=97 and n=95, respectively, P<0.001). STAT3 specifically bound the human PTTG promoter and induced PTTG transcriptional activity (twofold) as assessed by chromatin immunoprecipitation and luciferase reporter assays. STAT3 transfection increased PTTG mRNA and protein abundance twofold in HCT116 human colon cancer cells, and induction was further enhanced (threefold) by constitutively active STAT3 (STAT3-C), whereas strongly abrogated by dominant-negative STAT3 (STAT3-DN). Attenuating PTTG expression by siRNA in STAT3 HCT116 stable transfectants suppressed cell growth and colony formation in vitro, and PTTG cell knockout also constrained activated STAT3-induced explanted murine tumor growth in vivo. STAT3 increased HCT116 cell migration and invasion up to fivefold, whereas cell mobility was abolished by STAT3-DN (>85%). Impairing PTTG expression by siRNA also strongly suppressed STAT3-faciliated cell migration and invasion by up to 90%. Knocking out PTTG in STAT3-C HCT116 stable transfectants strongly decreased tumor metastases in nude mice, indicating the requirement of PTTG for STAT3-promoted metastasis. These results elucidate a mechanism for tumor cell PTTG regulation, whereby STAT3 induces PTTG expression to facilitate tumor growth and metastasis, and further support the rationale for targeting PTTG to abrogate colorectal cancer growth.

BACKGROUND: Recently, a vertebrate securin [pituitary tumor transforming gene (PTTG) in humans] has been identified that inhibits sister chromatid separation and is involved in malignant transformation and tumorigenesis. Abundance of this protein would disrupt cell division, generate chromosomal instability and thereby increase cell susceptibility to acquisition of further mutations during subsequent division. Esophageal cancer is a disease with poor prognosis with early local invasion and lymph node metastasis. It is important to identify factors that influence the aggressiveness of esophageal cancer. METHODS: expression of PTTG messenger ribonucleic acid (mRNA) was evaluated by real-time reverse transcription polymerase chain reaction in 48 esophageal cancer specimens and matched normal esophageal mucosa. The data were analyzed with reference to clinicopathological factors. RESULTS: tumor tissue expressed a significantly higher level of PTTG1 mRNA than the corresponding normal tissue (P < 0.0001). PTTG1 mRNA expression was significantly higher in tumors with higher pathological stage (IV vs 0-III, P = 0.0442) or more extensive lymph node metastasis (pathological N factor; N4 vs N0-3, P = 0.003). The median survival for patients with high PTTG1 expression (8.5 months) was less than that for patients with low PTTG1 expression (14.0 months, P = 0.039). PTTG1 expression was one of the significant predictors of survival on univariate analysis (hazard ratio 2.225; 95% confidence interval 1.007-4.915). CONCLUSIONS: Detection of high PTTG1 expression in surgically excised esophagus tumor tissues might help to identify patients with aggressive disease who require adjuvant therapy and provide prognostic information.

Human pituitary tumor-transforming 1 (PTTG1)/securin is a putative oncoprotein that is overexpressed in various tumor types. However, the involvement of PTTG1 in gastrointestinal cancer development and progression remains unclear. In this study, we investigated the clinical significance and biological effects of PTTG1 in esophageal squamous cell carcinoma (ESCC). Immunohistochemical studies performed on 113 primary ESCC specimens revealed a high prevalence of PTTG1 overexpression (60.2%), which was significantly associated with lymph node metastasis (regional, P = 0.042; distant, P = 0.005), advanced tumor stage (P = 0.028), and poorer overall survival (P = 0.017, log-rank test; P = 0.044, Cox proportional hazard model). Eleven ESCC cell lines expressed PTTG1 protein at levels 2.4 to 6.6 times higher than those in normal esophageal epithelial cells (HEEpiC). PTTG1 protein expression was confined to the nucleus in HEEpiC cells but present in both the cytoplasm and nucleus in ESCC cells. Two small interfering RNAs (siRNA) inhibited PTTG1 mRNA and protein expression in three ESCC cell lines by 77% to 97%. In addition, PTTG1 down-regulation by these siRNAs significantly reduced cell motility in all three ESCC cell lines (P < 0.01) in vitro, as well as popliteal lymph node metastases of ESCC cells in nude mice (P = 0.020). Global gene expression profiling suggested that several members of the Ras and Rho gene families, including RRAS, RHOG, ARHGAP1, and ARHGADIA, represented potential downstream genes in the PTTG1 pathway. Taken together, these findings suggest that PTTG1 overexpression promotes cell motility and lymph node metastasis in ESCC patients, leading to poorer survival. Thus, PTTG1 constitutes a potential biomarker and therapeutic target in ESCCs with lymph node metastases.

Human pituitary tumor transforming gene (PTTG) overexpression correlates with metastasis in multiple tumors, and yet its molecular mechanisms of action remain elusive. We detected PTTG overexpression in 66% (111 of 169) of primary esophageal squamous cell carcinoma (ESCC) tumor tissues by in situ hybridization. PTTG overexpression correlated with lymph node metastasis (P < 0.05). Ectopic PTTG overexpression in a representative ESCC cell line, EC9706, increased in vitro cell migration and invasion and promoted in vivo lymph node metastasis. Suppressing PTTG expression by siRNA decreased cell motility in both PTTG-HA/EC9706 and KYSE150 cells. By using mass spectrometric analysis, we identified that PTTG up-regulated S100A4 and galectin-1 secretion and down-regulated tissue inhibitor of metalloproteinase-2 secretion to the culture media. PTTG induced S100A4 and galectin-1 mRNA and protein expression as assessed by Western blot and reverse transcription-PCR. Attenuating galectin-1 expression by siRNA constrained PTTG-HA/EC9706 cell motility (P < 0.05). PTTG activated E-box transcription and induced c-Myc protein expression in EC9706 cells, which in turn may act on an E-box motif within the galectin-1 promoter. Chromatin immunoprecipitation assays further confirmed specific c-Myc binding to galectin-1 promoter. PTTG-induced galectin-1 transactivation and expression were mediated by c-Myc, and both inductions were suppressed by c-Myc RNAi cotranfection. These findings elucidate the molecular mechanisms of PTTG overexpression in promoting tumor metastasis, whereby up-regulated PTTG modulates expression and secretion of metastasis-related factors to facilitate cell motility.

AIM: Pituitary tumor transforming gene (PTTG1) is overexpressed in a variety of tumors, including carcinomas of the lung, breast, colon, as well as in leukemia, lymphoma and pituitary adenomas. However, there is little information on its expression in gastric carcinoma. We sought to investigate the expression of PTTG1 in gastric carcinoma and to explore the relationship between its expression and clinicopathological factors. METHODS: We studied 75 primary human gastric adenocarcinomas, including 17 mucosal carcinomas, 21 submucosal infiltrative carcinomas, 12 carcinomas invading proprial muscle layers, 6 carcinomas reaching the subserosa, and 19 carcinomas penetrating the serosal surface. Immunohistochemical analysis was performed using paraffin-embedded sections of gastric adenocarcinomas. RESULTS: PTTG1 was expressed heterogeneously in carcinomas. Positive PTTG1 staining was observed in 65.3% of the carcinomas (49 of 75). Its expression did not correlate significantly with either the histological type or the depth of infiltration of the gastric carcinomas. However, a statistical analysis showed significant differences between the primary adenocarcinomas and the associated metastatic lymph nodes. CONCLUSION: The results of this study demonstrate that PTTG1 expression is enhanced in metastatic lymph nodes in comparison to that in primary carcinomas. We suggest that PTTG1 may contribute to lymph node metastases in gastric carcinoma.

The aim of this study was to investigate the expression and clinical significance of hPTTG1 in gastric cancer. Immunohistochemistry was performed to determine the expression of hPTTG1 in gastric cancer tissues. Results showed that the positive expression of hPTTG1 in gastric cancer tissues was 60.00%, while in adjacent normal tissues it was 17.78%. The expression of hPTTG1 was correlated with differentiation levels, clinical classification and lymph node metastasis, but did not correlate with gender, age or pathological types. hPTTG1 was, therefore, overexpressed in gastric cancer tissues. The progression of gastric cancer was found to be correlated with the upregulation of the expression of hPTTG1. hPTTG1 detection may be helpful in evaluating the ability of the clinical classification and lymph node metastasis in gastric cancer to predict outcomes. These factors act as indicators of the biological behavior of gastric cancer and are fairly good markers for prognosis and therapy.