Endocrine Abstracts

The ability of the thyroid to accumulate iodide provides the basis for radioiodine ablation of differentiated thyroid cancers and their metastases. Most differentiated thyroid tumours exhibit reduced iodide uptake, however, and the mechanisms accounting for this remain poorly understood. Pituitary tumor transforming gene (PTTG) is a proto-oncogene implicated in the pathogenesis of thyroid tumours. We recently reported that PTTG and its binding factor PBF, also a potent transfo...

Introduction: New therapeutic strategies are urgently needed to improve radioiodide (RAI) uptake and efficiently ablate thyroid cancer cells, thereby reducing the risk of recurrent disease. We recently utilised high throughput screening and identified FDA-approved compounds capable of inducing sodium iodide symporter (NIS) function to enhance iodide uptake. Categorisation revealed a high proportion of drugs that modulate proteostasis, with 6 of the top 15 targeting activity of...

Dysregulation of sodium-iodide symporter (NIS) function is common in differentiated thyroid cancer, resulting in sub-optimal radioiodide therapy and poorer clinical outcome. Recent developments in identifying proteins that regulate the function of the sodium iodide symporter have highlighted two proteins involved in internalisation of NIS from the plasma membrane: AP-2 and moesin. Clathrin-mediated endocytosis (CME) of NIS is facilitated through the adaptor protein 2 (AP2) com...

Loss of function of succinate dehydrogenase (SDH), caused by mutations in each of the 4 subunits – SDHA/B/C and D – is associated with development of phaeochromocytomas and paragangliomas (PPGLs). The mutations lead to loss of enzymatic activity and subsequent accumulation of the oncometabolite succinate, a driver of tumourigenesis. It is well established but poorly understood why mutations in SDHB are associated with more aggressi...

The proto-oncogene pituitary tumor-transforming gene-binding factor (PBF) is upregulated in multiple tumours including thyroid cancer. PBF overexpression mediates tumorigenic processes such as cell motility and accelerates thyroid cancer cell invasion. We have recently shown that both PBF phosphorylation at tyrosine 174 (Y174) and PBF endocytosis are required for PBF-stimulated thyroid and breast cancer cell migration and invasion. This prompted further investigation into a ph...

The most common form of endocrine cancer is differentiated thyroid cancer (DTC). Outcomes of DTC largely depend on radioiodine treatment, which is mediated the sodium-iodide symporter (NIS). However, many tumours exhibit NIS dysregulation, resulting in a poorer prognosis. Since breast cancer can also overexpress NIS, albeit of limited function, radioiodine treatment may be a promising treatment option. Our previous data show that overexpression of the pituitary tumor-transform...

Whilst the majority of familial medullary thyroid cancer (MTC) is caused by germline mutations of the RET proto-oncogene, there are families and individuals with predisposition to MTC in whom no RET mutation has been identified (non-RET MTC). Recently, we identified novel mutations in a single gene termed MTC2 in non-RET MTC individuals by whole exome sequencing. The precise role of these MTC2 germline mutations in MTC tumorigenesis is however unclear. Here, we examined the fu...

Although the sodium iodide symporter (NIS) is expressed in 70–80% of breast cancers, only 20–30% is located at the plasma membrane (PM) and therefore functional. Previous work in thyroid cells leads demonstrated that PBF redistributes NIS from the PM into intracellular vesicles, potently reducing radioiodide uptake. We therefore examined whether increased membranous NIS could facilitate radioiodide therapy for breast cancer. Immunofluorescent microscopy revealed co-l...

Pituitary tumor-transforming gene binding factor (PBF) is a ubiquitous glycoprotein which is over-expressed in thyroid, breast and other endocrine cancers, and modulates cellular invasion, radioiodine uptake and thyroid hormone efflux. Papillary thyroid cancer patients with high PBF expression show decreased disease-specific survival compared to those with lower expression. PBF expression has recently been correlated with breast cancer metastasis and colon cancer extra-mural v...

Metastasis is a multistep process responsible for the vast majority of endocrine cancer deaths. We have previously identified the proto-oncogene PBF to be upregulated in differentiated thyroid cancer, and recently PBF expression has been correlated with distant thyroid cancer metastasis at diagnosis. Further, PBF potently induces breast cancer cell invasion in vitro, and our recent in vivo data demonstrate that colorectal tumours with higher PBF protein expre...