The proto-oncogene PTTG and its binding partner PBF have been widely studied in multiple cancer types, particularly thyroid and colorectal, but their combined role in tumourigenesis is uncharacterised. Here, we show for the first time that together PTTG and PBF significantly modulate DNA damage response (DDR) genes, including p53 target genes, required to maintain genomic integrity in thyroid cells. Critically, DDR genes were extensively repressed in primary thyrocytes from a bitransgenic murine model (Bi-Tg) of thyroid-specific PBF and PTTG overexpression. Irradiation exposure to amplify p53 levels further induced significant repression of DDR genes in Bi-Tg thyrocytes (P=2.4x10-4) compared to either PBF- (P=1.5x10-3) or PTTG-expressing thyrocytes (P=NS). Consistent with this, genetic instability was greatest in Bi-Tg thyrocytes (mean GI index of 35.8±2.6%), as well as significant induction of gross chromosomal aberrations in thyroidal TPC-1 cells following overexpression of PBF and PTTG. We extended our findings to human thyroid cancer using TCGA datasets (n=322) and found striking correlations with PBF and PTTG expression in well-characterised DDR gene panel RNA-seq data. In addition, genetic associations and transient transfection identified PBF as a downstream target of the RTK-BRAF signalling pathway, emphasising a role for PBF as a novel component in a pathway well-described to drive neoplastic growth. We also showed that overall survival (P=1.91x10-5) and disease-free survival (P=4.9x10-5) was poorer for TCGA patients with elevated tumoural PBF/PTTG expression and mutationally activated BRAF. Together our findings indicate that PBF and PTTG have a critical role in promoting thyroid cancer that is predictive of poorer patient outcome.
Primary hyperparathyroidism (PHPT) is not an uncommon disease in the western countries. In Thailand, on the contrary, PHPT was a rare condition with various clinical presentations. All 45 PHPT patients who underwent parathyroidectomy at the Department of Surgery, Siriraj Hospital during January 1997 and December 2007 were retrospectively reviewed. Demographic data, clinical presentation, localizations imaging, operative procedures, findings, complications, and pathological reports were analyzed. Median age was 49 years (range 15–89 years) with female: male ratio of 3 : 1. Only one patient (2.2%) was asymptomatic PHPT. Of all symptomatic cases, 30 (66.7%) had skeletal symptoms, 7 (15.6%) had renal impairment, and 39 (86.7%) had mixed symptoms. 42 patients (93.3%) had parathyroid scan and all had bilateral exploration of the neck. Postoperative hungry bone syndrome was noted in 10 patients (22%). On followup, skeletal and neuropsychiatric symptoms were improved but the renal impairment was remained. The s small number of asymptomatic PHPT in our study may refer to large number of underdiagnosed PHPT in general population. The guideline for screening serum calcium for diagnosis of PHPT in Thai populations will improve the long-term consequence of the disease but will need further information to identify the target group.
Context:Metastatic disease is responsible for the majority of endocrine cancer deaths. New therapeutic targets are urgently needed to improve patient survival rates.Objective:The proto-oncogene PTTG1-binding factor (PBF/PTTG1IP) is overexpressed in multiple endocrine cancers and circumstantially associated with tumor aggressiveness. This study aimed to understand the role of PBF in tumor cell invasion and identify possible routes to inhibit its action.Design, Setting, Patients, and Interventions:Thyroid, breast, and colorectal cells were transfected with PBF and cultured for in vitro analysis. PBF and cortactin (CTTN) expression was determined in differentiated thyroid cancer and The Cancer Genome Atlas RNA-seq data.Primary Outcome Measure:Pro-invasive effects of PBF were evaluated by 2D Boyden chamber, 3D organotypic, and proximity ligation assays.Results:Our study identified that PBF and CTTN physically interact and co-localize, and that this occurs at the cell periphery, particularly at the leading edge of migrating cancer cells. Critically, PBF induces potent cellular invasion and migration in thyroid and breast cancer cells, which is entirely abrogated in the absence of CTTN. Importantly, we found that CTTN is over-expressed in differentiated thyroid cancer, particularly in patients with regional lymph node metastasis, which significantly correlates with elevated PBF expression. Mutation of PBF (Y174A) or pharmacological intervention modulates the PBF: CTTN interaction and attenuates the invasive properties of cancer cells.Conclusion:Our results demonstrate a unique role for PBF in regulating CTTN function to promote endocrine cell invasion and migration, as well as identify a new targetable interaction to block tumor cell movement.
Pituitary tumor-transforming gene 1-binding factor (PTTG1IP; PBF) is a multifunctional glycoprotein, which is overexpressed in a wide range of tumours, and significantly associated with poorer oncological outcomes, such as early tumour recurrence, distant metastasis, extramural vascular invasion and decreased disease-specific survival. PBF transforms NIH 3T3 fibroblasts and induces tumours in nude mice, while mice harbouring transgenic thyroidal PBF expression show hyperplasia and macrofollicular lesions. Our assumption that PBF becomes an oncogene purely through increased expression has been challenged by the recent report of mutations in PBF within the Catalogue of Somatic Mutations in Cancer (COSMIC) database. We therefore sought to determine whether the first 10 PBF missense substitutions in human cancer might be oncogenic. Anisomycin half-life studies revealed that most mutations were associated with reduced protein stability compared to wild-type (WT) PBF. Proliferation assays narrowed our interest to two mutational events which significantly altered cell turnover: C51R and R140W. C51R was mainly confined to the endoplasmic reticulum while R140W was apparent in the Golgi apparatus. Both C51R and R140W lost the capacity to induce cellular migration and significantly reduced cell invasion. Colony formation and soft agar assays demonstrated that, in contrast to WT PBF, both mutants were unable to elicit significant colony formation or anchorage-independent growth. However, C51R and R140W retained the ability to repress radioiodide uptake, a functional hallmark of PBF. Our data reveal new insight into PBF function and confirm that, rather than being oncogenic, mutations in PBF are likely to be passenger effects, with overexpression of PBF the more important aetiological event in human cancer.
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