The mTOR protein as a target in thyroid cancer

The potential role of reprogrammed glucose metabolism: an emerging actionable codependent target in thyroid cancer

Although the incidence of thyroid cancer is increasing year by year, most patients, especially those with differentiated thyroid cancer, can usually be cured with surgery, radioactive iodine, and thyroid-stimulating hormone suppression. However, treatment options for patients with poorly differentiated thyroid cancers or radioiodine-refractory thyroid cancer have historically been limited. Altered energy metabolism is one of the hallmarks of cancer and a well-documented feature in thyroid cancer. In a hypoxic environment with extreme nutrient deficiencies resulting from uncontrolled growth, thyroid cancer cells utilize "metabolic reprogramming" to satisfy their energy demand and support malignant behaviors such as metastasis. This review summarizes past and recent advances in our understanding of the reprogramming of glucose metabolism in thyroid cancer cells, which we expect will yield new therapeutic approaches for patients with special pathological types of thyroid cancer by targeting reprogrammed glucose metabolism.

PI3K/mTOR inhibitor VS-5584 combined with PLK1 inhibitor exhibits synergistic anti-cancer effects on non-small cell lung cancer

Small molecule drugs are of significant importance in the treatment of non-small cell lung cancer (NSCLC). Here, we explored biological effects of the PI3K/mTOR inhibitor VS-5584 on NSCLC. Our findings indicated that VS-5584 administration resulted in a dose-dependent inhibition of NSCLC cell proliferation, as well as the induction of apoptosis and cycle arrest. Additionally, we observed a significant increase in intracellular reactive oxygen species (ROS) levels following VS-5584 treatment. The use of the ROS inhibitor N-acetylcysteine (NAC) effectively reduced ROS levels and decreased the proportion of apoptotic cells. Treatment with VS-5584 led to an upregulation of genes associated with apoptosis and cell cycle, such as c-caspase 3 and P21. Conversely, a downregulation of cyclin-dependent kinase 1 (CDK1) expression was observed. Next, transcriptome analyses revealed that VS-5584 treatment altered the abundance of 1520 genes/transcripts in PC-9 cells, one of which was polo-like kinase 1 (PLK1). These differentially expressed genes were primarily enriched in biological processes such as cell cycle regulation and cell apoptosis, which are closely linked to the P53 and apoptosis pathways. Co-treatment with VS-5584 and PLK1 inhibitor NMS-P937 resulted in enhanced cancer cell death, exhibiting synergistic inhibitory activity. Notably, VS-5584 inhibited the growth of NSCLC in a patient-derived xenograft (PDX) mouse model without observable abnormalities in major organs. Overall, VS-5584 effectively suppressed the growth of NSCLC cells both in vitro and in vivo. VS-5584 combined with NMS-P937 exhibited a synergistic effect in inhibiting NSCLC cell growth. These findings suggest that VS-5584 has potential as a therapeutic strategy for treating NSCLC.

Pin1 inhibitor API-1 sensitizes BRAF-mutant thyroid cancers to BRAF inhibitors by attenuating HER3-mediated feedback activation of MAPK/ERK and PI3K/AKT pathways

BRAFV600E mutation is one of the most therapeutic targets in thyroid cancers. However, its specific inhibitors have shown little clinical benefit because they can reactivate the MAPK/ERK and PI3K/AKT pathways by feedback upregulating the transcription of HER3. Peptidyl-prolyl cis/trans isomerase Pin1 has been proven to be closely associated with tumor progression. Here, we aimed to determine antitumor activity of Pin1 inhibitor API-1 in thyroid cancer and its effect on cellular response to BRAF inhibitors. The results showed that API-1 exhibited strong antitumor activity against thyroid cancer. Meanwhile, it improved the response of BRAF-mutant thyroid cancer cells to BRAF inhibitor PLX4032 and there was a synergistic effect between them. Specially, a combination therapy of API-1 and PLX4032 significantly inhibited cell proliferation, colony formation, and the growth of xenograft tumors as well as induced cell apoptosis in BRAF-mutant thyroid cancer cells compared with API-1 or PLX4032 monotherapy. Similar results were also observed in transgenic mice with BrafV600E-driven thyroid cancer. Mechanistically, API-1 enhanced XPO5 ability to export pre-microRNA 20a (pre-miR-20a) from the nucleus to cytoplasm, thereby promoting the maturation of miR-20a-5p. Further studies showed that miR-20a-5p specifically targeted and down-regulated HER3, thereby blocking the reactivation of MAPK/ERK and PI3K/AKT signaling pathways caused by PLX4032. These results, taken together, demonstrate that Pin1 inhibitor API-1 significantly improves the sensitivity of BRAF-mutant thyroid cancer cells to PLX4032. Thus, this study not only determines the potential antitumor activity of Pin1 inhibitor API-1 in thyroid cancer but also offers an alternative therapeutic strategy for BRAF-mutant thyroid cancers by a combination of Pin1 inhibitor and BRAF kinase inhibitor.

Identification of Prognostic Biomarkers in Papillary Thyroid Cancer and Developing Non-Invasive Diagnostic Models Through Integrated Bioinformatics Analysis

BACKGROUND

Papillary thyroid cancer (PTC) is the most frequent subtype of thyroid carcinoma, mainly detected in patients with benign thyroid nodules (BTN). Due to the invasiveness of accurate diagnostic tests, there is a need to discover applicable biomarkers for PTC. So, in this study, we aimed to identify the genes associated with prognosis in PTC. Besides, we performed a machine learning tool to develop a non-invasive diagnostic approach for PTC.

METHODS

For the study purposes, the miRNA dataset GSE130512 was downloaded from the GEO database and then analyzed to identify the common differentially expressed miRNAs in patients with non-metastatic PTC (nm-PTC)/metastatic PTC (m-PTC) compared with BTNs. The SVM was also applied to differentiate patients with PTC from those patients with BTN using the common DEMs. A protein-protein interaction network was also constructed based on the targets of the common DEMs. Next, functional analysis was performed, the hub genes were determined, and survival analysis was then executed.

RESULTS

A total of three common miRNAs were found to be differentially expressed among patients with nm-PTC/m-PTC compared with BTNs. In addition, it was established that the autophagosome maturation, ciliary basal body-plasma membrane docking, antigen processing as ubiquitination & proteasome degradation, and class I MHC mediated antigen processing & presentation are associated with the pathogenesis of PTC. Furthermore, it was illustrated that RPS6KB1, CCNT1, SP1, and CHD4 might serve as new potential biomarkers for PTC prognosis.

CONCLUSION

RPS6KB1, CCNT1, SP1, and CHD4 may be considered new potential biomarkers used for prognostic aims in PTC. However, performing validation tests is inevitable in the future.

A Ferroptosis-Related Signature Robustly Predicts Clinical Outcomes and Associates With Immune Microenvironment for Thyroid Cancer

Objective: This study aimed to construct a prognostic ferroptosis-related signature for thyroid cancer and probe into the association with tumor immune microenvironment.

Methods: Based on the expression profiles of ferroptosis-related genes, a LASSO cox regression model was established for thyroid cancer. Kaplan-Meier survival analysis was presented between high and low risk groups. The predictive performance was assessed by ROC. The predictive independency was validated via multivariate cox regression analysis and stratified analysis. A nomogram was established and verified by calibration curves. The enriched signaling pathways were predicted via GSEA. The association between the signature and immune cell infiltration was analyzed by CIBERSORT. The ferroptosis-related genes were validated in thyroid cancer tissues by immunohistochemistry and RT-qPCR.

Results: A ferroptosis-related eight gene model was established for predicting the prognosis of thyroid cancer. Patients with high risk score indicated a poorer prognosis than those with low risk score (p = 1.186e-03). The AUCs for 1-, 2-, and 3-year survival were 0.887, 0.890, and 0.840, respectively. Following adjusting other prognostic factors, the model could independently predict the prognosis (p = 0.015, HR: 1.870, 95%CI: 1.132–3.090). A nomogram combining the signature and age was constructed. The nomogram-predicted probability of 1-, 3-, and 5-year survival approached the actual survival time. Several ferroptosis-related pathways were enriched in the high-risk group. The signature was distinctly associated with the immune cell infiltration. After validation, the eight genes were abnormally expressed between thyroid cancer and control tissues.

Conclusion: Our findings established a prognostic ferroptosis-related signature that was associated with the immune microenvironment for thyroid cancer.

Akt1 genetic variants confer increased susceptibility to thyroid cancer

The PI3K-Akt-mTOR pathway plays a central role in the development of non-medullary thyroid carcinoma (NMTC). Although somatic mutations have been identified in these genes in NMTC patients, the role of germline variants has not been investigated. Here, we selected frequently occurring genetic variants in AKT1, AKT2, AKT3, PIK3CA and MTOR and have assessed their effect on NMTC susceptibility, progression and clinical outcome in a Dutch discovery cohort (154 patients, 188 controls) and a Romanian validation cohort (159 patients, 260 controls). Significant associations with NMTC susceptibility were observed for AKT1 polymorphisms rs3803304, rs2494732 and rs2498804 in the Dutch discovery cohort, of which the AKT1 rs3803304 association was confirmed in the Romanian validation cohort. No associations were observed between PI3K-Akt-mTOR polymorphisms and clinical parameters including histology, TNM staging, treatment response and clinical outcome. Functionally, cells bearing the associated AKT1 rs3803304 risk allele exhibit increased levels of phosphorylated Akt protein, potentially leading to elevated signaling activity of the oncogenic Akt pathway. All together, germline encoded polymorphisms in the PI3K-Akt-mTOR pathway could represent important risk factors in development of NMTC.

Treatment of Aggressive Thyroid Cancer

Although thyroid cancer generally has a good prognosis, there is a subset of patients for whom standard care (ie, treatment limited to surgery or surgery plus radioactive iodine) is either not appropriate because of the aggressive nature of their disease or not sufficient because of disease progression through standard treatment. Most of these tumors are in 3 groups: radioactive iodine-refractory differentiated thyroid carcinoma including poorly differentiated thyroid carcinoma anaplastic thyroid carcinoma, and progressive medullary thyroid carcinoma. Major classes of treatments in clinical development for these aggressive thyroid tumors include tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors, and mitogen-activated protein kinase kinase inhibitors.

Identification and characterization of two novel oncogenic mTOR mutations

Mammalian target of rapamycin (mTOR) signaling is often aberrantly activated, particularly when genetically altered, in human cancers. mTOR inhibitors targeting the activated mTOR signaling are highly promising anti-cancer drugs. Knowing the activating genetic change in mTOR can help guide the use of mTOR inhibitors for cancer treatment. This study was conducted to identify and characterize novel oncogenic mTOR mutations that can potentially be therapeutic targets in human cancer. We sequenced 30 exons of the mTOR gene in 12 thyroid cancer cell lines, 3 melanoma cell lines, 20 anaplastic thyroid cancer (ATC) tumors, and 23 melanoma tumors and functionally characterized the identified novel mTOR mutations in vitro and in vivo. We identified a novel point mutation A1256G in ATC cell line and G7076A in melanoma tumor in exon 9 and exon 51 of the mTOR gene, respectively. Over-expression of the corresponding mTOR mutants H419R and G2359E created through induced mutagenesis showed markedly elevated protein kinase activities associated with the activation of mTOR/p70S6K signaling in HEK293T cells. Stable expression of the two mTOR mutants in NIH3T3 cells strongly activated the mTOR/p70S6K signaling pathway and induced morphologic transformation, cell focus formation, anchorage-independent cell growth, and invasion. Inoculation of these mutant-expressing cells in athymic nude mice induced rapid tumor development, showing their driving oncogenicity. We also demonstrated that transfection with the novel mutants conferred cells high sensitivities to the mTOR inhibitor temsirolimus. We speculate that human cancers harboring these mTOR mutations, such as ATC and melanoma, may be effectively treated with inhibitors targeting mTOR.

miRNA-125a modulates autophagy of thyroiditis through PI3K/Akt/mTOR signaling pathway

The present study examined the potential function and underlying mechanisms of microRNA-125a (miR-125a) in thyroiditis. Mice were subcutaneously administered with 100 µg porcine thyroglobulin weekly for 2 weeks to establish the thyroiditis model. Results of the in vivo study demonstrated that miR-125a serum expression was upregulated in thyroiditis mice compared with the control group. In vitro studies were performed on a mouse macrophage cell line in which a model of thyroiditis was established using 10 ng/ml human interferon-γ. Upregulated miR-125a expression was achieved via mimic transfection. Increased miR-125a expression reduced autophagy and cell proliferation, increased the apoptotic rate and the expression of pro-inflammatory factors tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-18 via downregulation of the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway. PI3K inhibition enhanced the ability of miR-125a to increase the inflammatory response in vitro via regulation of the PI3K/Akt/mTOR signaling pathway. These results suggest miR-125a inhibited autophagy in a model of thyroiditis through the PI3K/Akt/mTOR signaling pathway.

mTOR Pathway in Papillary Thyroid Carcinoma: Different Contributions of mTORC1 and mTORC2 Complexes for Tumor Behavior and SLC5A5 mRNA Expression

The mammalian target of rapamycin (mTOR) pathway is overactivated in thyroid cancer (TC). We previously demonstrated that phospho-mTOR expression is associated with tumor aggressiveness, therapy resistance, and lower mRNA expression of SLC5A5 in papillary thyroid carcinoma (PTC), while phospho-S6 (mTORC1 effector) expression was associated with less aggressive clinicopathological features. The distinct behavior of the two markers led us to hypothesize that mTOR activation may be contributing to a preferential activation of the mTORC2 complex. To approach this question, we performed immunohistochemistry for phospho-AKT Ser473 (mTORC2 effector) in a series of 182 PTCs previously characterized for phospho-mTOR and phospho-S6 expression. We evaluated the impact of each mTOR complex on SLC5A5 mRNA expression by treating cell lines with RAD001 (mTORC1 blocker) and Torin2 (mTORC1 and mTORC2 blocker). Phospho-AKT Ser473 expression was positively correlated with phospho-mTOR expression. Nuclear expression of phospho-AKT Ser473 was significantly associated with the presence of distant metastases. Treatment of cell lines with RAD001 did not increase SLC5A5 mRNA levels, whereas Torin2 caused a ~6 fold increase in SLC5A5 mRNA expression in the TPC1 cell line. In PTC, phospho-mTOR activation may lead to the activation of the mTORC2 complex. Its downstream effector, phospho-AKT Ser473, may be implicated in distant metastization, therapy resistance, and downregulation of SLC5A5 mRNA expression.

Novel targeted therapies and immunotherapy for advanced thyroid cancers

Thyroid cancer is a frequently encountered endocrine malignancy. Despite the favorable prognosis of this disease, 15–20% of differentiated thyroid cancer (DTC) cases and most anaplastic types, remain resistant to standard treatment options, including radioactive iodine (RAI). In addition, around 30% of medullary thyroid cancer (MTC) cases show resistance after surgery. The evolving understanding of disease-specific molecular therapeutic targets has led to the approval of two targeted therapies (Sorafenib and Lenvatinib) for RAI refractory DTC and another two drugs (Vandetanib and Cabozantinib) for MTC. These advanced therapies exert their effects by blocking the MAPK pathway, which has been widely correlated to different types of thyroid cancers. While these drugs remain reserved for thyroid cancer patients who failed all treatment options, their ability to improve patients’ overall survival remain hindered by their low efficacy and other molecular factors. Among these factors is the tumor’s ability to activate parallel proliferative signaling pathways other than the cascades blocked by these drugs, along with overexpression of some tyrosine kinase receptors (TKR). These facts urge the search for novel different treatment strategies for advanced thyroid cases beyond these drugs. Furthermore, the growing knowledge of the dynamic immune system interaction with tumor microenvironment has revolutionized the cancer immune therapy field. In this review, we aim to discuss the molecular escape mechanisms of thyroid tumors from these drugs. We also highlight novel therapeutic options targeting other pathways than MAPK, including PI3K pathway, ALK translocations and HER2/3 receptors and their clinical impact. We also aim to discuss the usage of targeted therapy in restoring thyroid tumor sensitivity to RAI, and finally turn to extensively discuss the role of immunotherapy as a potential alternative treatment option for advanced thyroid diseases.

Molecular imaging of platelet-derived growth factor receptor-alpha (PDGFRα) in papillary thyroid cancer using immuno-PET

INTRODUCTION

Receptor tyrosine kinase (RTK) platelet-derived growth factor receptor-alpha (PDGFRα) was recently identified as a molecular switch for dedifferentiation in thyroid cancer that predicts resistance to therapy as well as recurrence of disease in papillary thyroid cancer. Here we describe the radiolabeling and functional characterization of an imaging probe based on a PDGFRα-specific monoclonal antibody (mAb) for immuno-PET imaging of PDGFRα in papillary thyroid cancer.

METHODS

Antibody D13C6 (Cell Signaling) was decorated with chelator NOTA using bioconjugation reaction with 2-(p-NCS-Bz)-NOTA. Radiolabeling was carried out using 40 μg of antibody-NOTA conjugate with 143-223 MBq of [⁶⁴Cu]CuCl₂ in 0.25 M NaOAc (pH 5.5) at 30 °C for 1 h. The reaction mixture was purified with size-exclusion chromatography (PD-10 column). PDGFRα and mock transfected B-CPAP thyroid cancer cells lines for validation of ⁶⁴Cu-labeled immuno-conjugates were generated using LVX-Tet-On technology. PET imaging was performed in NSG mice bearing bilaterally-induced PDGFRα (+/-) B-CPAP tumors.

RESULTS

Bioconjugation of NOTA chelator to monoclonal antibody D13C6 resulted in 2.8 ± 1.3 chelator molecules per antibody as determined by radiometric titration with ⁶⁴Cu. [⁶⁴Cu]Cu-NOTA-D13C6 was isolated in high radiochemical purity (>98%) and good radiochemical yields (19-61%). The specific activity was 0.9-5.1 MBq/μg. Cellular uptake studies revealed a specific radiotracer uptake in PDGFRα expressing cells compared to control cells. PET imaging resulted in SUV_mean values of ~5.5 for PDGFRα (+) and ~2 for PDGFRα (-) tumors, after 48 h p.i.. After 1 h, radiotracer uptake was also observed in the bone marrow (SUV_mean ~5) and spleen (SUV_mean ~8.5).

CONCLUSION

Radiolabeled antibody [⁶⁴Cu]Cu-NOTA-D13C6 represents a novel and promising radiotracer for immuno-PET imaging of PDGFRα in metastatic papillary thyroid cancer.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

The presented work has the potential to allow physicians to identify papillary thyroid cancer patients at risk of metastases by using the novel immuno-PET imaging assay based on PDGFRα-targeting antibody [⁶⁴Cu]Cu-NOTA-D13C6.

Bisphenol A and estrogen induce proliferation of human thyroid tumor cells via an estrogen-receptor-dependent pathway

OBJECTIVE

To determine the relationship between papillary thyroid carcinoma and environmental exposure to bisphenol A (BPA) or 17-β estrogen (E₂) by assessing the effects of these compounds on estrogen receptor expression and AKT/mTOR signaling.

METHODS

The effects of low levels of BPA (1mM-10nM) and 17β-estradiol (E2, 0.1mM-1nM) on ER expression and cellular proliferation were determined in human thyroid papillary cancer BHP10-3 cells. Protein and mRNA levels of estrogen nuclear receptors (ERα/ERβ) and membrane receptors (GPR30) were determined by immunofluorescence assay, Western blotting, and RT-PCR, respectively, and proliferation was assessed by CCK-8 assay.

RESULTS

The proliferative effects of BPA and E₂ were both concentration- and time-dependent. Expression of ERα/ERβ and GPR30 were enhanced by BPA and E_2. BPA and E₂ could quickly phosphorylate AKT/mTOR. Moreover, ICI suppressed ERα expression and activated GPR30 as did G-1. G-15 reversed the effects of E₂ on GPR30 and AKT/mTOR, but did not alter the effect of BPA.

CONCLUSIONS

BPA influences thyroid cancer proliferation by regulating expression of ERs and GPR30, a mechanism that differs from E₂. In addition, ICI and G-15 may have the potential to be used as anti-thyroid cancer agents.

PI3K/AKT Pathway and Its Mediators in Thyroid Carcinomas

Thyroid malignancies are the most common endocrine system carcinomas, with four histopathological forms. The phosphoinositide 3-kinase-protein kinase B/AKT (PI3K-PKB/AKT) pathway is one of the most critical molecular signaling pathways implicated in key cellular processes. Its continuous activation by several aberrant receptor tyrosine kinases (RTKs) and genetic mutations in its downstream effectors result in high cell proliferation in a broad number of cancers, including thyroid carcinomas. In this review article, the role of different signaling pathways of PI3K/AKT in thyroid cancers, with the emphasis on the PI3K/AKT/mammalian target of rapamycin (mTOR), PI3K/AKT/forkhead box O (FOXO) and PI3K/AKT/phosphatase and tensin homolog deleted on chromosome ten (PTEN) pathways, and various therapeutic strategies targeting these pathways have been summarized. In most of the in vitro studies, agents inhibiting mTOR in monotherapy or in combination with chemotherapy for thyroid malignancies have been introduced as promising anticancer therapies. FOXOs and PTEN are two outstanding downstream targets of the PI3K/AKT pathway. At the present time, no study has been undertaken to consider thyroid cancer treatment via FOXOs and PTEN targeting. According to the critical role of these proteins in cell cycle arrest, it seems that a treatment strategy based on the combination of FOXOs or PTEN activity induction with PI3K/AKT downstream mediators (e.g., mTOR) inhibition will be beneficial and promising in thyroid cancer treatment.

Combinatorial Antitumor Effect of Rapamycin and β-Elemene in Follicular Thyroid Cancer Cells

Background. mTOR signaling would be a promising target for thyroid cancer therapy. However, in clinical trials, objective response rate with mTOR inhibitor monotherapy in most cancer types was modest. A new focus on development of combinatorial strategies with rapalogs is increasing. Objective. Investigating the combinatorial antitumor effect of rapamycin and β-elemene in follicular thyroid cancer cells. Methods. MTT assay was used to determine the FTC-133 cell proliferation after culturing with rapamycin and/or β-elemene. To analyze their combinatorial effect, immunoblotting was performed to analyze the activation status of AKT. Moreover, β-elemene attenuated rapamycin-induced immunosuppression was tested in mice. Results. Combination of rapamycin and β-elemene exerted significant synergistic antiproliferative effects in FTC-133 cell lines in vitro, based on inhibiting the AKT feedback activation induced by rapamycin. In vivo, the β-elemene could attenuate rapamycin-induced immunosuppression via reversing imbalance of Treg/Th17, with the underlying mechanism needed to be declared. Conclusions. We demonstrate that the novel combination of mTOR inhibitor with β-elemene synergistically attenuates tumor cell growth in follicular thyroid cancer, which requires additional preclinical validation.

Autophagy activity is associated with membranous sodium iodide symporter expression and clinical response to radioiodine therapy in non-medullary thyroid cancer

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 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.

Retrospective Study of Sirolimus and Cyclophosphamide in Patients with Advanced Differentiated Thyroid Cancers

BACKGROUND

We hypothesize that the combination of an mTOR inhibitor, sirolimus, with a well-known cytotoxic agent, cyclophosphamide, provides a well-tolerated and promising alternative treatment for advanced, differentiated thyroid cancers (DTC).

METHODS

This retrospective review extracted data from patients treated for advanced DTC at the University of Michigan Comprehensive Cancer Center from 1995 through 2013. Fifteen patients treated with combination sirolimus and cyclophosphamide were identified as the sirolimus+cyp group. Seventeen patients treated with standard of care and enrolled in clinical trials were identified as the comparison group.

RESULTS

The one-year progression free survival rate (PFS) was 0.45, 95% CI [0.26, 0.80] in the sirolimus+cyp population and 0.30, 95% CI [0.13, 0.67] in the comparison population. The hazard ratio for PFS from initiation of treatment was 1.47, 95% CI [0.57, and 3.78]. In patients treated as first line, one-year PFS rate was 0.57, 95% CI [0.30, 1.00] in the sirolimus+cyp group and relatively unchanged at 0.29, 95% CI [0.11, 0.74] in the comparison group. The hazard ratio for PFS for first line patients was 1.10, 95% CI[ 0.4, and 3.5]. In patients with 3 or fewer sites of metastases, the one year PFS was 0.58, 95% CI [0.33, 1.00] in the sirolimus+cyp group, and 0.37, 95% CI [0.17, 0.80] in the comparison group. The average number of toxicities was 0.87 in the sirolimus+cyp patients and 1.71 in the comparison group.

CONCLUSIONS

The combination of sirolimus and cyclophosphamide was generally well tolerated with similar progression free survival, highlighting its applicability in patients with limited options.

Autophagy in thyroid cancer: present knowledge and future perspectives

Thyroid cancer is the most common endocrine malignancy. Despite having a good prognosis in the majority of cases, when the tumor is dedifferentiated it does no longer respond to conventional treatment with radioactive iodine, the prognosis worsens significantly. Treatment options for advanced, dedifferentiated disease are limited and do not cure the disease. Autophagy, a process of self-digestion in which damaged molecules or organelles are degraded and recycled, has emerged as an important player in the pathogenesis of different diseases, including cancer. The role of autophagy in thyroid cancer pathogenesis is not yet elucidated. However, the available data indicate that autophagy is involved in several steps of thyroid tumor initiation and progression as well as in therapy resistance and therefore could be exploited for therapeutic applications. The present review summarizes the most recent data on the role of autophagy in the pathogenesis of thyroid cancer and we will provide a perspective on how this process can be targeted for potential therapeutic approaches and could be further explored in the context of multimodality treatment in cancer and personalized medicine.

Advances in thyroid cancer treatment: latest evidence and clinical potential

Advanced thyroid carcinoma is an infrequent tumor entity with limited treatment possibilities until recently. The extraordinary improvement in the comprehension of genetic and molecular alterations involving the RAS/RAF/mitogen-activated protein kinase and phosphatidylinositide 3-kinase/Akt/mammalian target of rapamycin signaling and interacting pathways that are involved in tumor survival, proliferation, differentiation, motility and angiogenesis have been the rationale for the development of new effective targeted therapies. Data coming from phase II clinical trials have confirmed the efficacy of those targeted agents against receptors in cell membrane and cytoplasmic molecules. Moreover, four of those investigational drugs, vandetanib, cabozantinib, sorafenib and lenvatinib, have reached a phase III clinical trial with favorable results in progression-free survival and overall survival in medullary thyroid carcinoma and differentiated thyroid carcinoma. Further analysis for an optimal approach has been conducted according to mutational profile and tumor subtypes. However, consistent results are still awaited and the research for adequate prognostic and predictive biomarkers is ongoing. The following report offers a comprehensive review from the rationale to the basis of targeted agents in the treatment of thyroid carcinoma. In addition, current and future therapeutic developments by the inhibition of further molecular targets are discussed in this setting.

Multikinase inhibitors use in differentiated thyroid carcinoma

Thyroid cancer is the most common endocrine malignancy, and its incidence is increasing. Standard therapy for most patients with localized differentiated thyroid cancer (DTC) includes surgery, radioactive iodine, and thyroid hormone replacement. A minority of thyroid cancer patients requires systemic therapy for metastatic disease. Patients with metastatic DTC do not usually benefit from traditional cytotoxic chemotherapy. In this review, we describe newly developed small-molecule tyrosine kinase inhibitors (TKIs) that are being actively tested and used in the management of advanced thyroid cancer. The use of TKIs as a form of molecular targeted therapy is evolving based on understanding of the pathways involved in DTC. Disrupting tumor vascular supply by targeting vascular endothelial growth factor receptor signaling is the most commonly used approach to treat advanced/metastatic DTC. Other mechanisms include targeting BRAF, MAPK/ERK kinase, or mammalian target of rapamycin signaling. Although TKIs appear to have superior efficacy compared to cytotoxic chemotherapy, they can cause substantial adverse effects; symptomatic management of adverse effects, dose adjustment, or cessation of therapy may be required.

Evaluation of PTEN, PI3K, MTOR, and KRAS expression and their clinical and prognostic relevance to differentiated thyroid carcinoma

Aim of the study

Important signalling pathways play fundamental roles in the pathogenesis of thyroid carcinoma (TC). PTEN, mTOR, PI3K-p85 and K-Ras are the principal factors involved in these signalling pathways. To immunohistochemically examine the expressions of PI3K, mTOR and PTEN in patients suffering from follicular TC, papillary TC or variants thereof, as well as to investigate KRAS mutations via PCR to determine their clinical and prognostic relevance to differentiated thyroid cancer.

Material and methods

The expression of PTEN, PI3K-p85 and mTOR was immunohistochemically examined, and the mutation of K-Ras was examined via PCR. The results obtained were compared to the clinico-pathologic characteristics of the patients.

Results

A significant correlation was found between p85 expression and lymphovascular invasions and between PTEN expression and multifocality (p = 0.048 and p = 0.04, respectively), and a correlation between p85 and capsular invasion was found, with a borderline statistical significance (p = 0.056). No expression of PTEN, p85 or Mtor was detected in normal tissue. K-Ras mutation was examined in 66 of the 101 patients (57.4%), and the percentage of patients exhibiting a K-Ras mutation was 17.4%. All of the patients exhibiting a K-Ras mutation were women (p = 0.047). The disease-free survival was 44.6 months (95% CI: 37.9–51.3) and was statistically significantly higher in the group that displayed level 1 or lower expression of p85 (p = 0.043).

Conclusions

The expression levels of the aforementioned markers were significantly higher in TC cells than in normal tissue. A significant correlation was detected between K-Ras mutation and gender. This study demonstrates that p85 and PTEN are markers that should be evaluated in further studies of TC.

AMP-activated protein kinase signaling is upregulated in papillary thyroid cancer

AMP-activated protein kinase (AMPK) is activated by the depletion in cellular energy levels and allows adaptive changes in cell metabolism and cell survival. Recently, our group described that AMPK plays an important role in the regulation of iodide and glucose uptake in thyroid cells. However, AMPK signaling pathway in human thyroid carcinomas has not been investigated so far.

OBJECTIVE

To evaluate the expression and activity of AMPK in papillary thyroid carcinomas.

METHODS

We examined total and phosphorylated AMPK (tAMPK and pAMPK) and phosphorylated acetyl-CoA-carboxylase (pACC) expressions through imunohistochemistry, using a tissue microarray block composed of 73 papillary thyroid carcinomas (PAP CA) or microcarcinomas (PAP MCA) and six adenoma (AD) samples from patients followed at the Federal University Hospital. The expression levels were compared with the non-neoplastic tissues from the same patient. Two different pathologists analyzed the samples and attributed scores of staining intensity and the proportion of stained cells. A total index was obtained by multiplying the values of intensity and the proportion of stained cells (INTxPROP).

RESULTS

tAMPK, pAMPK, and pACC showed a predominant cytoplasmic staining in papillary carcinomas, adenomas, and non-neoplastic thyroid tissues. However, the intensity and the proportion of stained cells were higher in carcinomas, so that a significant increase was found in the INTxPROP score both in PAP CA and PAP MCA, when compared with their respective controls.

CONCLUSION

Our results show unequivocally that AMPK pathway is highly activated in papillary thyroid carcinomas; however, more studies are necessary to understand the pathophysiological significance of AMPK activation in thyroid carcinogenesis.

Estrogen-related receptor alpha modulates lactate dehydrogenase activity in thyroid tumors

Metabolic modifications of tumor cells are hallmarks of cancer. They exhibit an altered metabolism that allows them to sustain higher proliferation rates in hostile environment outside the cell. In thyroid tumors, the expression of the estrogen-related receptor α (ERRα), a major factor of metabolic adaptation, is closely related to the oxidative metabolism and the proliferative status of the cells. To elucidate the role played by ERRα in the glycolytic adaptation of tumor cells, we focused on the regulation of lactate dehydrogenases A and B (LDHA, LDHB) and the LDHA/LDHB ratio. Our study included tissue samples from 10 classical and 10 oncocytic variants of follicular thyroid tumors and 10 normal thyroid tissues, as well as samples from three human thyroid tumor cell lines: FTC-133, XTC.UC1 and RO82W-1. We identified multiple cis-acting promoter elements for ERRα, in both the LDHA and LDHB genes. The interaction between ERRα and LDH promoters was confirmed by chromatin immunoprecipitation assays and in vitro analysis for LDHB. Using knock-in and knock-out cellular models, we found an inverse correlation between ERRα expression and LDH activity. This suggests that thyroid tumor cells may reprogram their metabolic pathways through the up-regulation of ERRα by a process distinct from that proposed by the recently revisited Warburg hypothesis.

Autophagy induction of reversine on human follicular thyroid cancer cells

The incurable differentiated thyroid cancer (DTC), poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) are the most aggressive in all of the thyroid cancers. Unfortunately, there are almost no effective therapies. A novel and effective treatment is urgently needed to develop. Recently, reversine, a small synthetic purine analogue, has been reported to be effective in human thyroid cancer suppression through cell cycle arrest and apoptosis induction. In this study, we performed an in vitro evaluation of reversine on autophagy activation, one of the programmed cell death, and the related mechanisms in human follicular thyroid cancer cell line WRO. Incubation of WRO cells with reversine induced autophagosome formation in a short time treatment. LC3-II overexpression in a dosage-dependent manner with reversine treatment was demonstrated in the autophagy activation. Moreover, reversine suppressed Akt/mTOR related signaling pathway activation, a major pathway for autophagy activation, was also revealed in WRO cells. Our data demonstrated that reversine is effective to induce autophagy. Moreover, the LC3-II overexpression and the p62 protein were degraded in a time-dependent manner, indicating that the autophagic flux has happened in the reversine treated WRO cells. In addition, the activation of Akt/mTOR/p70S6K related pathways were shown to be reduced, suggesting these pathways may involve in the reversine mediated autophagy induction. Reversine is therefore worthy of further investigation in clinical therapeutics.

Thyroid cancer: molecular aspects and new therapeutic strategies

Despite that thyroid cancer accounts for over 90% of tumors that arise from the endocrine system, these tumors barely represent 2% of solid tumors in adults. Many entities are grouped under the general term of thyroid cancer, and they differ in histological features as well as molecular and clinical behavior. Thus, the prognosis for patients with thyroid cancer ranges from a survival rate of >97% at 5 years, in the case of differentiated thyroid tumors sensitive to radioactive iodine, to a 4-month median survival for anaplastic tumors. The high vascularity in these tumors and the important role that oncogenic mutations may have in the RAS/RAF/MEK pathway and oncogenicity (as suggested by activating mutations and rearrangements of the RET gene) have led to the development of multitarget inhibitors in different histological subgroups of patients. The correct molecular characterization of patients with thyroid cancer is thought to be a key aspect for the future clinical management of these patients.