Objective: Our objective was to evaluate the efficacy and safety of sunitinib following at least one course of radioactive iodine treatment in patients with advanced differentiated thyroid cancer (DTC). The study endpoints included best response rate (including best objective response rate) and progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, measurement of serum thyroglobulin (Tg), and toxicity evaluation.Design and methods: This was a single center, nonrandomized, open-label, phase 2 clinical trial. In total, 23 patients were enrolled and were treated with a starting daily, oral dose of 37.5 mg sunitinib. Patients were evaluated with imaging, laboratory tests, and physical examination periodically per protocol.Results: The mean best response was a decrease of 17.2% (s.d. 22.8) in tumor sum from baseline. Six (26%) patients achieved a partial response (PR), and 13 (57%) had stable disease (SD) for a clinical benefit rate (PR+SD) of 83%. The overall median PFS was 241 days (interquartile limits, 114–518). No statistically significant difference was observed between the medians of the baseline and post-treatment Tg values (P=0.24). The most common adverse events included grades 1 and 2 decreases in blood cell counts (especially leukocytes), diarrhea, fatigue, hand–foot skin reaction, nausea, musculoskeletal pain, and hypertension.Conclusions: These data demonstrate that sunitinib exhibits significant anti-tumor activity in patients with advanced DTC. Since sunitinib was relatively well-tolerated, there is the potential for clinical benefit in these patients, and further investigation of this agent is warranted.

The nuclear-encoded subunit 4 of cytochrome c oxidase (COX4) plays a role in regulation of oxidative phosphorylation and contributes to cancer progression. We sought to determine the role of COX4 in differentiated (DTC) and medullary (MTC) thyroid cancers. We examined the expression of COX4 in human thyroid tumors by immunostaining and used shRNA-mediated knockdown of COX4 to evaluate its functional contributions in thyroid cancer cell lines. In human thyroid tissue, the expression of COX4 was higher in cancers than in either normal thyroid (p = 0.0001) or adenomas (p = 0.001). The level of COX4 expression correlated with tumor size (p = 0.04) and lymph-node metastases (p = 0.024) in patients with MTCs. COX4 silencing had no effects on cell signaling activation and mitochondrial respiration in DTC cell lines (FTC133 and BCPAP). In MTC-derived TT cells, COX4 silencing inhibited p70S6K/pS6 and p-ERK signaling, and was associated with decreased oxygen consumption and ATP production. Treatment with potassium cyanide had minimal effects on FTC133 and BCPAP, but inhibited mitochondrial respiration and induced apoptosis in MTC-derived TT cells. Our data demonstrated that metastatic MTCs are characterized by increased expression of COX4, and MTC-derived TT cells are vulnerable to COX4 silencing. These data suggest that COX4 can be considered as a novel molecular target for the treatment of MTC.

The detection of rare mutational targets in plasma (liquid biopsy) has emerged as a promising tool for the assessment of patients with cancer. We determined the presence of cell-free DNA containing the BRAFV600E mutations (cfBRAFV600E) in plasma samples from 57 patients with papillary thyroid cancer (PTC) with somatic BRAFV600E mutation-positive primary tumors using microfluidic digital PCR, and co-amplification at lower denaturation temperature (COLD) PCR. Mutant cfBRAFV600E alleles were detected in 24/57 (42.1%) of the examined patients. The presence of cfBRAFV600E was significantly associated with tumor size (p = 0.03), multifocal patterns of growth (p = 0.03), the presence of extrathyroidal gross extension (p = 0.02) and the presence of pulmonary micrometastases (p = 0.04). In patients with low-, intermediate- and high-risk PTCs, cfBRAFV600E was detected in 4/19 (21.0%), 8/22 (36.3%) and 12/16 (75.0%) of cases, respectively. Patients with detectable cfBRAFV600E were characterized by a 4.68 times higher likelihood of non-excellent response to therapy, as compared to patients without detectable cfBRAFV600E (OR (odds ratios), 4.68; 95% CI (confidence intervals)) 1.26–17.32; p = 0.02). In summary, the combination of digital polymerase chain reaction (dPCR) with COLD-PCR enables the detection of BRAFV600E in the liquid biopsy from patients with PTCs and could prove useful for the identification of patients with PTC at an increased risk for a structurally or biochemically incomplete or indeterminate response to treatment.

Background: ¹³¹ I treatment (tx) of differentiated thyroid cancer (DTC) is associated with hematopoietic toxicity. It was hypothesized that metformin could have radioprotective effects on bone-marrow function. The objective was to determine whether metformin prevents ¹³¹ I-induced changes in complete blood counts (CBC) in patients with DTC. Methods: A retrospective analysis was performed of CBC values in DTC patients who were (40 patients: metformin group) or were not taking metformin (39 patients: control group) at the time of administration of ¹³¹ I. Repeated measures analysis of variance was used for the analysis of the differences in the averages of CBC that were documented at baseline and at 1, 6, and 12 months post ¹³¹ I tx. Results: The groups were comparable in terms of age, sex, stage of DTC, ¹³¹ I dose administered, and baseline CBC values. In the control group, the decrease in white blood cells (WBC) was 35.8% ( p < 0.0001) at one month, 21.8% ( p < 0.0001) at six months, and 19.4% ( p < 0.0001) at 12 months. In the metformin group, the decrease in WBC was 17.1% ( p < 0.0001) at one month, and 8.6% at six months ( p = 0.01), while at 12 months WBC had returned to baseline values ( p = 0.9). Differences between the two groups were highly statistically significant at all time points ( p < 0.0001, p = 0.0027, and p < 0.0001, respectively). Lymphocytes were more sensitive to ¹³¹ I, but metformin's radioprotective properties were more prominent in neutrophils. At 12 months, the decrease in platelets in the control group was 15.5% ( p < 0.0001) versus 5.6% ( p = 0.056) in the metformin group, while at one and six months the reductions in the two groups were comparable. No statistically significant differences were observed between the two groups in the change from baseline values for hemoglobin. Conclusions: Metformin attenuated the ¹³¹ I-induced decrease in CBC parameters, and its radioprotective properties were more prominent in WBC. Patients who were taking metformin during ¹³¹ I tx also experienced a faster recovery in their blood counts, when compared to the control group. Further study is warranted in order to examine if the radioprotective properties of metformin observed in the current study for ¹³¹ I tx can also apply to other forms of therapeutic chemo- and radiotherapy.

Mitotane is used for the treatment of adrenocortical cancer and elicits its anticancer effects via inhibition of mitochondrial respiration. Targeting mitochondria‑dependent metabolism has emerged as a promising strategy for thyroid cancer (TC) treatment. We hypothesized that mitotane targets mitochondria and induces apoptosis in TC cells. Cell lines representative of the major histological variants of TC were chosen: Follicular (FTC‑133), poorly differentiated (BCPAP), anaplastic (SW1736 and C643) and medullary (TT) TC cells, and were treated with mitotane (0‑100 µM). Mitochondrial membrane potential, cell viability and apoptosis were examined by JC‑1 staining and by western blot analysis using an antibody against caspase‑3. The expression of mitochondrial molecules and DNA damage markers and the activation of endoplasmic reticulum (ER) stress were determined by western blotting. The expression of mitochondrial ATP synthase subunit β (ATP5B) was examined by immunostaining in 100 human TC tissue samples. Treatment with mitotane (50 µM for 24 h) decreased the viability of FTC‑133, BCPAP, SW1736, C643 and TT cells by 12, 59, 54, 31 and 66%, respectively. Morphological evidence of ER stress and overexpression of ER markers was observed in TC cells following exposure to mitotane. The treatment led to increased expression of histone γH2AX, indicating DNA damage, and to caspase‑3 cleavage. Consistent with the results of the cell viability assays, the overexpression of pro‑apoptotic genes following treatment with mitotane was more prominent in TC cells harboring mutations in the serine/threonine‑protein kinase B‑raf gene and proto‑oncogene tyrosine‑protein kinase receptor Ret. Treatment with mitotane was associated with loss of mitochondrial membrane potential and decreased expression of ATP5B, particularly in the medullary TC (MTC)‑derived TT cells. Immunohistochemical analysis of mitochondrial ATP5B in human TC specimens demonstrated its overexpression in cancer compared with normal thyroid tissue. The level of ATP5B expression was higher in MTC compared with the follicular, papillary or anaplastic types of TC. Mitotane elicited pleiotropic effects on TC cells, including induction of ER stress, inhibition of mitochondrial membrane potential and induction of apoptosis. The results of the present study suggest that mitotane could be considered as a novel agent for the treatment of aggressive types of TC.