Differentiated thyroid cancer (DTC) is the most frequent endocrine tumor with a good prognosis after primary treatment in most cases. By contrast, 30-40% of patients with metastatic DTC are... Show moreDifferentiated thyroid cancer (DTC) is the most frequent endocrine tumor with a good prognosis after primary treatment in most cases. By contrast, 30-40% of patients with metastatic DTC are unresponsive to I-131 radioactive iodide (RAI) treatment due to tumor dedifferentiation. Currently, underlying molecular mechanisms of dedifferentiation remain elusive and predictive biomarkers are lacking. Therefore, the present study aimed to identify molecular biomarkers in primary tumors associated with RAI refractoriness. A retrospective cohort was gathered consisting of RAI-sensitive patients with DTC and RAI-refractory patients with poorly DTC. In all patients, extensive intratumoral mutation profiling, gene fusions analysis, telomerase reverse transcriptase (TERT) promoter mutation analysis and formalin-fixed paraffin-embedded-compatible RNA sequencing were performed. Genetic analyses revealed an increased mutational load in RAI-refractory DTC, including mutations in AKT1, PTEN, TP53 and TERT promoter. Transcriptomic analyses revealed profound differential expression of insulin-like growth factor 2 (IGF2), with up to 100-fold higher expression in RAI-refractory DTC compared with in RAI-sensitive DTC cases. ELISA revealed significant lower IGF2 plasma concentrations after surgery and subsequent I-131 RAI therapy in patients with DTC compared with pretreatment baseline. Overall, the current findings suggested that the tumor-promoting growth factor IGF2 may have a potential role in acquiring RAI refractoriness. Show less
Purpose Non-medullary thyroid cancer (NMTC) treatment is based on the ability of thyroid follicular cells to accumulate radioactive iodide (RAI). However, in a subset of NMTC patients tumor... Show morePurpose Non-medullary thyroid cancer (NMTC) treatment is based on the ability of thyroid follicular cells to accumulate radioactive iodide (RAI). However, in a subset of NMTC patients tumor dedifferentiation occurs, leading to RAI resistance. Digoxin has been demonstrated to restore iodide uptake capacity in vitro in poorly differentiated and anaplastic NMTC cells, termed redifferentiation. The aim of the present study was to investigate the in vivo effects of digoxin in TPO-Cre/LSL-Braf(V600E) mice and digoxin-treated NMTC patients. Methods Mice with thyroid cancer were subjected to 3D ultrasound for monitoring tumor growth and I-124 PET/CT for measurement of intratumoral iodide uptake. Post-mortem analyses on tumor tissues comprised gene expression profiling and measurement of intratumoral autophagy activity. Through PALGA (Dutch Pathology Registry), archived tumor material was obtained from 11 non-anaplastic NMTC patients who were using digoxin. Clinical characteristics and tumor material of these patients were compared to 11 matched control NMTC patients never treated with digoxin. Results We found that in mice, tumor growth was inhibited and I-124 accumulation was sustainably increased after short-course digoxin treatment. Post-mortem analyses revealed that digoxin treatment increased autophagy activity and enhanced expression of thyroid-specific genes in mouse tumors compared to vehicle-treated mice. Digoxin-treated NMTC patients exhibited significantly higher autophagy activity and a higher differentiation status as compared to matched control NMTC patients, and were associated with favourable clinical outcome. Conclusions These in vivo data support the hypothesis that digoxin may represent a repositioned adjunctive treatment modality that suppresses tumor growth and improves RAI sensitivity in patients with RAI-refractory NMTC. Show less
Although non-medullary thyroid cancer (NMTC) generally has a good prognosis, 30-40% of patients with distant metastases develop resistance to radioactive iodine (RAI) therapy due to tumor... Show moreAlthough non-medullary thyroid cancer (NMTC) generally has a good prognosis, 30-40% of patients with distant metastases develop resistance to radioactive iodine (RAI) therapy due to tumor dedifferentiation. For these patients, treatment options are limited and prognosis is poor. In the present study, expression and activity of autophagy was assessed in large sets of normal, benign and malignant tissues and was correlated with pathology, SLC5A5/hNIS (solute carrier family 5 member 5) protein expression, and with clinical response to RAI ablation therapy in NMTC patients. Fluorescent immunostaining for the autophagy marker LC3 was performed on 100 benign and 80 malignant thyroid tissues. Semiquantitative scoring was generated for both diffuse LC3-I intensity and number of LC3-II-positive puncta and was correlated with SLC5A5 protein expression and clinical parameters. Degree of diffuse LC3-I intensity and number of LC3-II-positive puncta scoring were not discriminative for benign vs. malignant thyroid lesions. Interestingly, however, in NMTC patients significant associations were observed between diffuse LC3-I intensity and LC3-II-positive puncta scoring on the one hand and clinical response to RAI therapy on the other hand (odds ratio [OR] = 3.13, 95% confidence interval [CI] =1.91-5.12, P = 0.01; OR = 5.68, 95%CI = 3.02-10.05, P = 0.002, respectively). Mechanistically, the number of LC3-II-positive puncta correlated with membranous SLC5A5 expression (OR = 7.71, 95%CI = 4.15-11.75, P<0.001), number of RAI treatments required to reach remission (P = 0.014), cumulative RAI dose (P = 0.026) and with overall remission and recurrence rates (P = 0.031). In conclusion, autophagy activity strongly correlates with clinical response of NMTC patients to RAI therapy, potentially by its capacity to maintain tumor cell differentiation and to preserve functional iodide uptake. Show less
