The CREB/CRE transcriptional pathway has been implicated in circadian clock timing and light-evoked clock resetting. To date, much of the work on CREB in circadian physiology has focused on how changes in the phosphorylation state of CREB regulate the timing processes. However, beyond changes in phosphorylation, CREB-dependent transcription can also be regulated by the CREB co-activator CRTC (CREB-regulated transcription coactivator), also known as TORC (Transducer of Regulated CREB). Here we profiled both the rhythmic and light-evoked regulation of CRTC1 and CRTC2 in the murine suprachiasmatic nucleus (SCN), the locus of the master mammalian clock. Immunohistochemical analysis revealed rhythmic expression of CRTC1 in the SCN. CRTC1 expression was detected throughout the dorso-ventral extent of the SCN in the middle of the subjective day, with limited expression during early night, and late night expression levels intermediate between mid-day and early night levels. In contrast to CRTC1, robust expression of CRTC2 was detected during both the subjective day and night. During early and late subjective night, a brief light pulse induced strong nuclear accumulation of CRTC1 in the SCN. In contrast with CRTC1, photic stimulation did not affect the subcellular localization of CRTC2 in the SCN. Additionally, period1 reporter gene profiling and ChIP analysis revealed that CRTC1 was associated with CREB in the 5′ regulatory region of the period1 gene, and that over-expression of CRTC1 leads to a marked upregulation in period1 transcription. Together these data raise the prospect that CRTC1 plays a role in fundamental aspects of SCN clock timing and entrainment.

Targeted radioiodine therapy for thyroid cancer is based on selective stimulation of Na+/I− Symporter (NIS)-mediated radioactive iodide uptake (RAIU) in thyroid cells by thyrotropin. Patients with advanced thyroid cancer do not benefit from radioiodine therapy due to reduced or absent NIS expression. To identify inhibitors that can be readily translated into clinical care, we examined oncological pipeline inhibitors targeting Akt, MEK, PI3K, Hsp90 or BRAF in their ability to increase RAIU in thyroid cells expressing BRAFV600E or RET/PTC3 oncogene. Our data showed that (1) PI3K inhibitor GDC-0941 outperformed other inhibitors in RAIU increase mainly by decreasing iodide efflux rate to a great extent; (2) RAIU increase by all inhibitors was extensively reduced by TGF-β, a cytokine secreted in the invasive fronts of thyroid cancers; (3) RAIU reduction by TGF-β was mainly mediated by NIS reduction and could be reversed by Apigenin, a plant-derived flavonoid; and (4) In the presence of TGF-β, GDC-0941 with Apigenin co-treatment had the highest RAIU level in both BRAFV600E expressing cells and RET/PTC3 expressing cells. Taken together, Apigenin may serve as a dietary supplement along with small molecule inhibitors to improve radioiodine therapeutic efficacy on invasive tumor margins thereby minimizing future metastatic events.

Radioactive iodine (RAI) is a key therapeutic modality for thyroid cancer. Loss of RAI uptake in thyroid cancer inversely correlates with patient’s survival. In this review, we focus on the challenges encountered in delivering sufficient doses of I-131 to eradicate metastatic lesions without increasing the risk of unwanted side effects. Sodium iodide symporter (NIS) mediates iodide influx, and NIS expression and function can be selectively enhanced in thyroid cells by thyroid-stimulating hormone. We summarize our current knowledge of NIS modulation in normal and cancer thyroid cells, and we propose that several reagents evaluated in clinical trials for other diseases can be used to restore or further increase RAI accumulation in thyroid cancer. Once validated in preclinical mouse models and clinical trials, these reagents, mostly small-molecule inhibitors, can be readily translated into clinical practice. We review available genetically engineered mouse models of thyroid cancer in terms of their tumor development and progression as well as their thyroid function. These mice will not only provide important insights into the mechanisms underlying the loss of RAI uptake in thyroid tumors but will also serve as preclinical animal models to evaluate the efficacy of candidate reagents to selectively increase RAI uptake in thyroid cancers. Taken together, we anticipate that the optimal use of RAI in the clinical management of thyroid cancer is yet to come in the near future.

MicroSPECT/CT image acquisition and analysis for thyroidal RAI uptake is greatly improved by the cradle and the CTViewer software, respectively. Furthermore, the approach of superimposing thyroid VOIs from t24 images to select thyroid VOIs on corresponding aligned t1 images can be applied to studies in which the target tissue has differential radiotracer retention from surrounding tissues.