Targeting BRAF in thyroid cancer

Targeting the RAS upstream and downstream signaling pathway for cancer treatment

Cancer often involves the overactivation of RAS/RAF/MEK/ERK (MAPK) and PI3K-Akt-mTOR pathways due to mutations in genes like RAS, RAF, PTEN, and PIK3CA. Various strategies are employed to address the overactivation of these pathways, among which targeted therapy emerges as a promising approach. Directly targeting specific proteins, leads to encouraging results in cancer treatment. For instance, RTK inhibitors such as imatinib and afatinib selectively target these receptors, hindering ligand binding and reducing signaling initiation. These inhibitors have shown potent efficacy against Non-Small Cell Lung Cancer. Other inhibitors, like lonafarnib targeting Farnesyltransferase and GGTI 2418 targeting geranylgeranyl Transferase, disrupt post-translational modifications of proteins. Additionally, inhibition of proteins like SOS, SH2 domain, and Ras demonstrate promising anti-tumor activity both in vivo and in vitro. Targeting downstream components with RAF inhibitors such as vemurafenib, dabrafenib, and sorafenib, along with MEK inhibitors like trametinib and binimetinib, has shown promising outcomes in treating cancers with BRAF-V600E mutations, including myeloma, colorectal, and thyroid cancers. Furthermore, inhibitors of PI3K (e.g., apitolisib, copanlisib), AKT (e.g., ipatasertib, perifosine), and mTOR (e.g., sirolimus, temsirolimus) exhibit promising efficacy against various cancers such as Invasive Breast Cancer, Lymphoma, Neoplasms, and Hematological malignancies. This review offers an overview of small molecule inhibitors targeting specific proteins within the RAS upstream and downstream signaling pathways in cancer.

RAS-RAF-miR-296-3p signaling axis increases Rad18 expression to augment radioresistance in pancreatic and thyroid cancers

Oncogenic RAS and RAF signaling has been implicated in contributing to radioresistance in pancreatic and thyroid cancers. In this study, we sought to better clarify molecular mechanisms contributing to this effect. We discovered that miRNA 296-3p (miR-296-3p) is significantly correlated with radiosensitivity in a panel of pancreatic cancer cells, and miR-296-3p is highly expressed in normal cells, but low in cancer cell lines. Elevated expression of miR-296-3p increases radiosensitization while decreasing the expression of the DNA repair enzyme RAD18 in both pancreatic and thyroid cancer cells. RAD18 is overexpressed in both pancreatic and thyroid tumors compared to matched normal controls, and high expression of RAD18 in tumors is associated with poor prognostic features. Modulating the expression of mutant KRAS in pancreatic cancer cells or mutant BRAF in thyroid cancer cells demonstrates a tight regulation of RAD18 expression in both cancer types. Depletion of RAD18 results in DNA damage and radiation-induced cell death. Importantly, RAD18 depletion in combination with radiotherapy results in marked and sustained tumor regression in KRAS mutant pancreatic cancer orthotopic tumors and BRAF mutant thyroid heterotopic tumors. Overall, our findings identify a novel coordinated RAS/RAF-miR-296-3p-RAD18 signaling network in pancreatic and thyroid cancer cells, which leads to enhanced radioresistance.

Leveraging molecular targeted drugs and immune checkpoint inhibitors treat advanced thyroid carcinoma to achieve thyroid carcinoma redifferentiation

Thyroid cancer can be classified into three different types based on the degree of differentiation: well-differentiated, poorly differentiated, and anaplastic thyroid carcinoma. Well-differentiated thyroid cancer refers to cancer cells that closely resemble normal thyroid cells, while poorly differentiated and anaplastic thyroid carcinoma are characterized by cells that have lost their resemblance to normal thyroid cells. Advanced thyroid carcinoma, regardless of its degree of differentiation, is known to have a higher likelihood of disease progression and is generally associated with a poor prognosis. However, the process through which well-differentiated thyroid carcinoma transforms into anaplastic thyroid carcinoma, also known as "dedifferentiation", has been a subject of intensive research. In recent years, there have been significant breakthroughs in the treatment of refractory advanced thyroid cancer. Clinical studies have been conducted to evaluate the efficacy and safety of molecular targeted drugs and immune checkpoint inhibitors in the treatment of dedifferentiated thyroid cancer. These drugs work by targeting specific molecules or proteins in cancer cells to inhibit their growth or by enhancing the body's immune response against the cancer cells. This article aims to explore some of the possible mechanisms behind the dedifferentiation process in well-differentiated thyroid carcinoma. It also discusses the clinical effects of molecular targeted drugs and immune checkpoint inhibitors in thyroid cancer patients with different degrees of differentiation. Furthermore, it offers insights into the future trends in the treatment of advanced thyroid cancer, highlighting the potential for improved outcomes and better patient care.

Unraveling the role of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer by multi-omics analyses

The role of the serine/glycine metabolic pathway (SGP) has recently been demonstrated in tumors; however, the pathological relevance of the SGP in thyroid cancer remains unexplored. Here, we perform metabolomic profiling of 17 tumor-normal pairs; bulk transcriptomics of 263 normal thyroid, 348 papillary, and 21 undifferentiated thyroid cancer samples; and single-cell transcriptomes from 15 cases, showing the impact of mitochondrial one-carbon metabolism in thyroid tumors. High expression of serine hydroxymethyltransferase-2 (SHMT2) and methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is associated with low thyroid differentiation scores and poor clinical features. A subpopulation of tumor cells with high mitochondrial one-carbon pathway activity is observed in the single-cell dataset. SHMT2 inhibition significantly compromises mitochondrial respiration and decreases cell proliferation and tumor size in vitro and in vivo. Collectively, our results highlight the importance of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer and suggest that SHMT2 is a potent therapeutic target.

A Clinical Viewpoint on the Use of Targeted Therapy in Advanced Gastric Cancer

The development of therapies for advanced gastric cancer (GC) has made significant progress over the past few years. The identification of new molecules and molecular targets is expanding our understanding of the disease's intricate nature. The end of the classical oncology era, which relied on well-studied chemotherapeutic agents, is giving rise to novel and unexplored challenges, which will cause a significant transformation of the current oncological knowledge in the next few years. The integration of established clinically effective regimens in additional studies will be crucial in managing these innovative aspects of GC. This study aims to present an in-depth and comprehensive review of the clinical advancements in targeted therapy and immunotherapy for advanced GC.

Disulfiram/Cu Kills and Sensitizes BRAF-Mutant Thyroid Cancer Cells to BRAF Kinase Inhibitor by ROS-Dependently Relieving Feedback Activation of MAPK/ERK and PI3K/AKT Pathways

BRAF^V600E, the most common genetic alteration, has become a major therapeutic target in thyroid cancer. Vemurafenib (PLX4032), a specific inhibitor of BRAF^V600E kinase, exhibits antitumor activity in patients with BRAF^V600E-mutated thyroid cancer. However, the clinical benefit of PLX4032 is often limited by short-term response and acquired resistance via heterogeneous feedback mechanisms. Disulfiram (DSF), an alcohol-aversion drug, shows potent antitumor efficacy in a copper (Cu)-dependent way. However, its antitumor activity in thyroid cancer and its effect on cellular response to BRAF kinase inhibitors remain unclear. Antitumor effects of DSF/Cu on BRAF^V600E-mutated thyroid cancer cells and its effect on the response of these cells to BRAF kinase inhibitor PLX4032 were systematically assessed by a series of in vitro and in vivo functional experiments. The molecular mechanism underlying the sensitizing effect of DSF/Cu on PLX4032 was explored by Western blot and flow cytometry assays. DSF/Cu exhibited stronger inhibitory effects on the proliferation and colony formation of BRAF^V600E-mutated thyroid cancer cells than DSF treatment alone. Further studies revealed that DSF/Cu killed thyroid cancer cells by ROS-dependent suppression of MAPK/ERK and PI3K/AKT signaling pathways. Our data also showed that DSF/Cu strikingly increased the response of BRAF^V600E-mutated thyroid cancer cells to PLX4032. Mechanistically, DSF/Cu sensitizes BRAF-mutant thyroid cancer cells to PLX4032 by inhibiting HER3 and AKT in an ROS-dependent way and subsequently relieving feedback activation of MAPK/ERK and PI3K/AKT pathways. This study not only implies potential clinical use of DSF/Cu in cancer therapy but also provides a new therapeutic strategy for BRAF^V600E-mutated thyroid cancers.

Rare adult pilocytic astrocytoma of the septum pellucidum with novel RIN2::BRAF fusion

Pilocytic astrocytoma is mostly a pediatric tumor with the majority of patients under age 20. Although tumors can occur throughout neuraxis, most tumors are in the cerebellum and optic chiasm. Pilocytic astrocytoma in unusual locations is often associated with different genetic alterations than the classic KIAA1549::BRAF fusion. We report a rare adult pilocytic astrocytoma of the septum pellucidum that presented with progressive headache. A detailed genomic evaluation found a fusion between BRAF and a novel partner RIN2, a gene overexpressed in both low-grade glioma and glioblastoma. The RIN2::BRAF transcript encodes a chimeric protein containing a dimerization domain SH2 and an intact kinase domain, consistent with a prototypic oncogenic kinase rearrangement. In addition, we discuss the potential oncogenic mechanisms of BRAF signaling and its implication in targeted therapy with kinase inhibitors.

Systemic Therapy in Thyroid Cancer

Thyroid cancer is the most common endocrine malignancy. While surgery remains the mainstay of the treatment of all different histologies, for differentiated thyroid cancers, radioactive iodine also plays an important role in management. Once tumor becomes radio-iodine refractory, it needs systemic therapy. Earlier, these tumors had very dismal prognosis. However, with the advancement of technology and research, it has become clear now that thyroid cancer cells are driven by various mutations. Targeting these oncogenic drivers by various molecules have proven to be effective therapeutic strategy in thyroid cancer. Besides, as in other solid tumors, immunotherapy is also being evaluated in thyroid cancer. While these new therapeutic approaches have revolutionized the treatment on advanced/metastatic thyroid cancer, there are definite challenges which limit their use in common clinical practice. These challenges include higher treatment cost and lack of testing to identify the driver mutations. Moreover, there is still need for further research in thyroid cancers to identify oncogenic targets and agent to act upon them.

Vitamin C sensitizes BRAFV600E thyroid cancer to PLX4032 via inhibiting the feedback activation of MAPK/ERK signal by PLX4032

BACKGROUND

BRAFV600E mutation is the most common mutation in thyroid cancer. It strongly activates MAPK/ERK pathway and indicates an invasive subtype of thyroid cancer. PLX4032 is a selective oral inhibitor of the BRAFV600 kinase although with limited effect in treating this panel of thyroid cancer, due to the feedback activation of MAPK/ERK as well as PI3K/AKT pathways. It was investigated that Vitamin C plays a positive role in inhibiting these pathways in thyroid cancer. However, whether Vitamin C could enhance the antitumor effect of PLX4032 remains largely unclear.

METHODS

The antitumor efficacy of combination therapy with PLX4032 and Vitamin C on BRAF^MT thyroid cancer cell was assessed by the MTT assay, EdU assay and colony formation, Chou-Talalay way was employed to analyze the synergistic effect. Flow cytometry were employed to assess cells' apoptosis and cell cycle arrest in response to combination therapy. Xenograft models were used to test its in vivo antitumor activity. Western blot and IHC were applied to investigate the mechanism underlying synergistic effect.

RESULTS

PLX4032 or Vitamin C monotherapy was mildly effective in treating BRAF^MT thyroid cancer cell and xenografts model. The combination therapy significantly inhibited cancer cell proliferation and tumor growth in nude mice, and induced cell apoptosis and cell cycle arrest compared to either monotherapy. PLX4032 monotherapy induced feedback activation of MAPK/ERK as well as PI3K/AKT pathway; while combination therapy significantly relieved this feedback.

CONCLUSION

Vitamin C promotes the antitumor effect of PLX4032 in BRAF^MT thyroid cancer cell and xenografts model via relieving the feedback activation of MAPK/ERK as well as PI3K/AKT pathway. PLX4032/Vitamin C combination may be a potential therapeutic approach to treat BRAF^MT thyroid cancer.

Functional Gene Clusters in Global Pathogenesis of Clear Cell Carcinoma of the Ovary Discovered by Integrated Analysis of Transcriptomes

Clear cell carcinoma of the ovary (ovarian clear cell carcinoma (OCCC)) is one epithelial ovarian carcinoma that is known to have a poor prognosis and a tendency for being refractory to treatment due to unclear pathogenesis. Published investigations of OCCC have mainly focused only on individual genes and lack of systematic integrated research to analyze the pathogenesis of OCCC in a genome-wide perspective. Thus, we conducted an integrated analysis using transcriptome datasets from a public domain database to determine genes that may be implicated in the pathogenesis involved in OCCC carcinogenesis. We used the data obtained from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) DataSets. We found six interactive functional gene clusters in the pathogenesis network of OCCC, including ribosomal protein, eukaryotic translation initiation factors, lactate, prostaglandin, proteasome, and insulin-like growth factor. This finding from our integrated analysis affords us a global understanding of the interactive network of OCCC pathogenesis.

MAPK mutations and cigarette smoke promote the pathogenesis of pulmonary Langerhans cell histiocytosis

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare smoking-related lung disease characterized by dendritic cell (DC) accumulation, bronchiolocentric nodule formation, and cystic lung remodeling. Approximately 50% of patients with PLCH harbor somatic BRAF-V600E mutations in cells of the myeloid/monocyte lineage. However, the rarity of the disease and lack of animal models have impeded the study of PLCH pathogenesis. Here, we establish a cigarette smoke-exposed (CS-exposed) BRAF-V600E-mutant mouse model that recapitulates many hallmark characteristics of PLCH. We show that CD11c-targeted expression of BRAF-V600E increases DC responsiveness to stimuli, including the chemokine CCL20, and that mutant cell accumulation in the lungs of CS-exposed mice is due to both increased cellular viability and enhanced recruitment. Moreover, we report that the chemokine CCL7 is secreted from DCs and human peripheral blood monocytes in a BRAF-V600E-dependent manner, suggesting a possible mechanism for recruitment of cells known to dominate PLCH lesions. Inflammatory lesions and airspace dilation in BRAF-V600E mice in response to CS are attenuated by transitioning animals to filtered air and treatment with a BRAF-V600E inhibitor, PLX4720. Collectively, this model provides mechanistic insights into the role of myelomonocytic cells and the BRAF-V600E mutation and CS exposure in PLCH pathogenesis and provides a platform to develop biomarkers and therapeutic targets.

BRAF Inhibitors in Thyroid Cancer: Clinical Impact, Mechanisms of Resistance and Future Perspectives

The Kirsten rat sarcoma viral oncogene homolog (RAS)/v-raf-1 murine leukemia viral oncogene homolog 1 (RAF)/mitogen-activated protein kinase 1 (MAPK) signaling cascade is the most important oncogenic pathway in human cancers. Tumors leading mutations in the gene encoding for v-raf murine sarcoma viral oncogene homolog B (BRAF) serine-threonine kinase are reliant on the MAPK signaling pathway for their growth and survival. Indeed, the constitutive activation of MAPK pathway results in continuous stimulation of cell proliferation, enhancement of the apoptotic threshold and induction of a migratory and metastatic phenotype. In a clinical perspective, this scenario opens to the possibility of targeting BRAF pathway for therapy. Thyroid carcinomas (TCs) bearing BRAF mutations represent approximately 29–83% of human thyroid malignancies and, differently from melanomas, are less sensitive to BRAF inhibitors and develop primary or acquired resistance due to mutational events or activation of alternative signaling pathways able to reactivate ERK signaling. In this review, we provide an overview on the current knowledge concerning the mechanisms leading to resistance to BRAF inhibitors in human thyroid carcinomas and discuss the potential therapeutic strategies, including combinations of BRAF inhibitors with other targeted agents, which might be employed to overcome drug resistance and potentiate the activity of single agent BRAF inhibitors.

DDR1 regulates thyroid cancer cell differentiation via IGF-2/IR-A autocrine signaling loop

Patients with thyroid cancers refractory to radioiodine (RAI) treatment show a limited response to various therapeutic options and a low survival rate. The recent use of multikinase inhibitors has also met limited success. An alternative approach relies on drugs that induce cell differentiation, as the ensuing increased expression of the cotransporter for sodium and iodine (NIS) may partially restore sensitivity to radioiodine. The inhibition of the ERK1/2 pathway has shown some efficacy in this context. Aggressive thyroid tumors overexpress the isoform-A of the insulin receptor (IR-A) and its ligand IGF-2; this IGF-2/IR-A loop is associated with de-differentiation and stem-like phenotype, resembling RAI-refractory tumors. Importantly, IR-A has been shown to be positively modulated by the non-integrin collagen receptor DDR1 in human breast cancer. Using undifferentiated human thyroid cancer cells, we now evaluated the effects of DDR1 on IGF-2/IR-A loop and on markers of cell differentiation and stemness. DDR1 silencing or downregulation caused significant reduction of IR-A and IGF-2 expression, and concomitant increased levels of differentiation markers (NIS, Tg, TSH, TPO). Conversely, markers of epithelial-to-mesenchymal transition (Vimentin, Snail-2, Zeb1, Zeb2 and N-Cadherin) and stemness (OCT-4, SOX-2, ABCG2 and Nanog) decreased. These effects were collagen independent. In contrast, overexpression of either DDR1 or its kinase-inactive variant K618A DDR1-induced changes suggestive of less differentiated and stem-like phenotype. Collagen stimulation was uneffective. In conclusion, in poorly differentiated thyroid cancer, DDR1 silencing or downregulation blocks the IGF-2/IR-A autocrine loop and induces cellular differentiation. These results may open novel therapeutic approaches for thyroid cancer.

Antitumor effects of anlotinib in thyroid cancer

There is no effective treatment for patients with poorly differentiated papillary thyroid cancer or anaplastic thyroid cancer (ATC). Anlotinib, a multi-kinase inhibitor, has already shown antitumor effects in various types of carcinoma in a phase I clinical trial. In this study, we aimed to better understand the effect and efficacy of anlotinib against thyroid carcinoma cells in vitro and in vivo. We found that anlotinib inhibits the cell viability of papillary thyroid cancer and ATC cell lines, likely due to abnormal spindle assembly, G2/M arrest, and activation of TP53 upon anlotinib treatment. Moreover, anlotinib suppresses the migration of thyroid cancer cells in vitro and the growth of xenograft thyroid tumors in mice. Our data demonstrate that anlotinib has significant anticancer activity in thyroid cancer, and potentially offers an effective therapeutic strategy for patients of advanced thyroid cancer type.

Radioiodination and biodistribution of newly synthesized 3-benzyl-2-([3-methoxybenzyl]thio)benzo[g]quinazolin-4-(3H)-one in tumor bearing mice

3-Benzyl-2-((3-methoxybenzyl)thio)benzo[g]quinazolin-4(3H)-one was previously synthesized and proved by physicochemical analyses (HRMS, 1H and 13C NMR). The target compound was examined for its radioactivity and the results showed that benzo[g]quinazoline was successfully labeled with radioactive iodine using NBS via an electrophilic substitution reaction. The reaction parameters that affected the labeling yield such as concentration, pH and time were studied to optimize the labeling conditions. The radiochemical yield was 91.2 ± 1.22% and the in vitro studies showed that the target compound was stable for up to 24 h. The thyroid was among the other organs in which the uptake of 125I-benzoquinazoline has increased significantly over the time up to 4.1%. The tumor uptake was 6.95%. Radiochemical and metabolic stability of the benzoquinazoline in vivo/in vitro and biodistribution studies provide some insights about the requirements for developing more potent radiopharmaceutical for targeting the tumor cells.

LncRNA-MALAT1 as a novel biomarker of cadmium toxicity regulates cell proliferation and apoptosis

Cadmium (Cd) and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not well understood. This study aimed to investigate whether lncRNA-MALAT1 could serve as a novel biomarker of Cd toxicity in cells, animals and Cd-exposed workers, and regulate cell proliferation, apoptosis, migration and invasion. MALAT1 expression increased gradually in CdCl2 transformed 16HBE cells. The cell apoptosis, migration and invasion were significantly inhibited, and the mRNA and protein expression of FOXC2, STAT, BAX, EGFR, and TGF-β1 reduced, but BCL-2 increased (P < 0.05) after silencing MALAT1 by siRNA in CdCl2 treated 16HBE cells of 15th and 35th passages. Cadmium increased MALAT1 expression in the lung of Cd-exposed rats in a dose-dependent manner. A significant positive correlation was observed between blood MALAT1 expression and urinary/blood Cd concentrations, and there were significant correlations of MALAT1 expression with the expressions of target genes in the lung of Cd-exposed rats and the blood of Cd exposed workers. This study suggests that the expression of MALAT1 is upregulated and regulates the cell cycle progression, proliferation, apoptosis, migration and invasion in Cd toxicity. MALAT1 may serve as a novel valuable biomarker of cadmium exposure and cadmium toxicity.

B-Raf mutation and papillary thyroid carcinoma patients

Thyroid carcinoma is the most prevalent endocrine neoplasm globally. In the majority of thyroid carcinoma cases, a positive prognosis is predicted following administration of the appropriate treatment. A wide range of genetic alterations present in thyroid carcinoma exert their oncogenic actions partially through the activation of the mitogen-activated protein kinase pathway, with the B-Raf mutation in particular being focused on by experts for decades. The B-Raf gene has numerous mutations, however, V600E presents with the highest frequency. It is believed that the existence of the V600E mutation may demonstrate an association with the clinicopathological characteristics of patients, however, inconsistencies remain in the literature. A number of explanatory theories have been presented in order to resolve these discrepancies. Recently, it has been suggested that the V600E mutation may function as a target in a novel approach that may aid the diagnosis and prognosis of thyroid carcinoma, with a number of vying methods put forward to that effect. The current review aims to assist researchers in further understanding the possible association between B-Raf mutations and thyroid carcinoma.

Circular RNAs are long-lived and display only minimal early alterations in response to a growth factor

Circular RNAs (circRNAs) are widespread circles of non-coding RNAs with largely unknown function. Because stimulation of mammary cells with the epidermal growth factor (EGF) leads to dynamic changes in the abundance of coding and non-coding RNA molecules, and culminates in the acquisition of a robust migratory phenotype, this cellular model might disclose functions of circRNAs. Here we show that circRNAs of EGF-stimulated mammary cells are stably expressed, while mRNAs and microRNAs change within minutes. In general, the circRNAs we detected are relatively long-lived and weakly expressed. Interestingly, they are almost ubiquitously co-expressed with the corresponding linear transcripts, and the respective, shared promoter regions are more active compared to genes producing linear isoforms with no detectable circRNAs. These findings imply that altered abundance of circRNAs, unlike changes in the levels of other RNAs, might not play critical roles in signaling cascades and downstream transcriptional networks that rapidly commit cells to specific outcomes.

Implications of mitogen-activated protein kinase signaling in glioma

Gliomas are the most common primary central nervous system tumors. Gliomas originate from astrocytes, oligodendrocytes, and neural stem cells or their precursors. According to WHO classification, gliomas are classified into four different malignant grades ranging from grade I to grade IV based on histopathological features and related molecular aberrations. The induction and maintenance of these tumors can be attributed largely to aberrant signaling networks. In this regard, the mitogen-activated protein kinase (MAPK) network has been widely studied and is reported to be severely altered in glial tumors. Mutations in MAPK pathways most frequently affect RAS and B-RAF in the ERK, c-Jun N-terminal kinase (JNK), and p38 pathways leading to malignant transformation. Also, it is linked to both inherited and sequential accumulations of mutations that control receptor tyrosine kinase (RTK)-activated signal transduction pathways, cell cycle growth arrest pathways, and nonresponsive cell death pathways. Genetic alterations that modulate RTK signaling can also alter several downstream pathways, including RAS-mediated MAP kinases along with JNK pathways, which ultimately regulate cell proliferation and cell death. The present review focuses on recent literature regarding important deregulations in the RTK-activated MAPK pathway during gliomagenesis and progression.

Identification of potential therapeutic targets for papillary thyroid carcinoma by bioinformatics analysis

The aim of the present study was to identify potential therapeutic targets for papillary thyroid carcinoma (PTC) and to investigate the possible mechanism underlying this disease. The gene expression profile, GSE53157, was downloaded from the Gene Expression Omnibus database. Only 10 chips, including 3 specimens of normal thyroid tissues and 7 specimens of well-differentiated thyroid carcinomas, were analyzed in the present study. Differentially-expressed genes (DEGs) between PTC patients and normal individuals were identified. Next, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses of DEGs were performed. Modules in the protein-protein interaction (PPI) network were identified. Significant target genes were selected from the microRNA (miRNA) regulatory network. Furthermore, the integrated network was constructed with the miRNA regulatory and PPI network modules, and key target genes were screened. A total of 668 DEGs were identified. Modules M1, M2 and M3 were identified from the PPI network. From the modules, DEGs of cyclin-dependent kinase inhibitor 1A, S100 calcium binding protein A6 (S100A6), dual specificity phosphatase 5, keratin 19, met proto-oncogene (MET) and lectin galactoside-binding soluble 3 were included in the Malacards database. In the miRNA regulatory and integrated networks, genes of cyclin-dependent kinase inhibitor 1C (CDKN1C), peroxisome proliferator-activated receptor γ, aryl hydrocarbon receptor, basic helix-loop-helix family, member e40 and reticulon 1 were the key target genes. S100A6, MET and CDKN1C may exhibit key roles in the progression and development of PTC, and may be used as specific therapeutic targets in the treatment of PTC. However, further experiments are required to confirm these results.

Treatment of advanced thyroid cancer: role of molecularly targeted therapies

Advanced thyroid cancer is not amenable to therapy with conventional cytotoxic chemotherapy. However, newer advances in the understanding of the molecular pathogenesis of different subtypes of thyroid cancer have provided new opportunities for the evaluation of molecularly targeted therapies. This has led to multiple clinical trials using various multi-kinase inhibitors and the subsequent US FDA approval of sorafenib for differentiated thyroid cancer and vandetanib and cabozantinib for medullary thyroid carcinoma. This review provides a summary of the current literature for the treatment of advanced thyroid carcinoma and future directions in this disease.

Sorafenib for the treatment of thyroid cancer: an updated review

INTRODUCTION

Sorafenib (Nexavar) is an oral multi-kinase inhibitor targeting B-type Raf kinase (BRAF) (both wild type and BRAF(V600E)), VEGFR1, VEGFR2, VEGFR3, PDGFRβ and RET (also RET/PTC) influencing both differentiated thyroid cancer (DTC) cell proliferation and angiogenesis.

AREAS COVERED

Encouraging results achieved in numerous Phase II trials were confirmed in a Phase III study conducted in radioiodine-refractory DTC. Sorafenib compared to placebo significantly prolongs progression-free survival, 10.8 versus 5.8 months, respectively. However, its administration resulted mainly in disease stabilization. No complete remission was obtained in any study. Beneficial effects were also demonstrated for medullary and anaplastic thyroid cancer; however further studies fulfilling evidence based medicine criteria are necessary. Its toxicity profile is convergent with other VEGFR inhibitors. The most common treatment-related side-effects involve skin toxicity (predominantly hand-foot skin reaction, different rashes and alopecia), gastrointestinal disturbances (diarrhea, abdominal pain), constitutional adverse reactions (anorexia, weight loss, fatigue) and hypertension. Although most adverse reactions are manageable, > 50% of patients required dose reduction.

EXPERT OPINION

Sorafenib constitutes the first line treatment option in advanced, radioiodine-refractory DTC. However, there are still no data on its efficacy in patients progressed after another tyrosine kinase inhibitor. Other applications of the drug, such as use as adjuvant therapy to 131-I treatment, requires further studies.

Low VHL mRNA expression is associated with more aggressive tumor features of papillary thyroid carcinoma

Alterations of the von Hippel–Lindau (VHL) tumor suppressor gene can cause different hereditary tumors associated with VHL syndrome, but the potential role of the VHL gene in papillary thyroid carcinoma (PTC) has not been characterized. This study set out to investigate the relationship of VHL expression level with clinicopathological features of PTC in an ethnically and geographically homogenous group of 264 patients from Serbia, for the first time. Multivariate logistic regression analysis showed a strong correlation between low level of VHL expression and advanced clinical stage (OR = 5.78, 95% CI 3.17–10.53, P<0.0001), classical papillary morphology of the tumor (OR = 2.92, 95% CI 1.33–6.44, P = 0.008) and multifocality (OR = 1.96, 95% CI 1.06–3.62, P = 0.031). In disease-free survival analysis, low VHL expression had marginal significance (P = 0.0502 by the log-rank test) but did not appear to be an independent predictor of the risk for chance of faster recurrence in a proportion hazards model. No somatic mutations or evidence of VHL downregulation via promoter hypermethylation in PTC were found. The results indicate that the decrease of VHL expression associates with tumor progression but the mechanism of downregulation remains to be elucidated.

Sorafenib and thyroid cancer

The emergence of serine-threonine small molecule, multi-targeted kinase inhibitors over the past decade is greatly impacting the therapeutic armamentarium for numerous malignancies, especially thyroid carcinoma. Chief among them are a class of agents referred to as vascular endothelial growth factor signal pathway inhibitors. Sorafenib is a lead compound that has been recently approved by the US FDA for radioactive iodine-refractory differentiated thyroid cancer (DTC). Sorafenib clearly is altering the natural history of DTC. In the largest randomized Phase III study ever conducted in DTC, sorafenib significantly improved progression-free survival compared to placebo (10.8 vs 5.8 months) and had an acceptable and manageable safety profile, though commonly attributed side effects of hand-foot skin reaction, diarrhea and hypertension were more frequent than in other settings. This agent represents a new treatment option for patients with progressive radioactive iodine-refractory DTC.

The prognostic implication and potential role of BRAF mutation in the decision to perform elective neck dissection for thyroid cancer

The BRAF V600E mutation is the most common genetic change in patients with papillary thyroid cancer (PTC). Many studies have shown that detection of the BRAF V600E mutation is useful for confirming or establishing the preoperative diagnosis of PTC. Moreover, the mutation is associated with aggressive tumor characteristics or poor prognostic factors in most. However, whether preoperative detection of this mutation changes the treatment strategy or surgical extent, including prophylactic central neck dissection (CND), remains controversial. In this paper, we review the currently available literature regarding the potential role of the BRAF V600E mutation in the decision to perform elective neck dissection for PTC.

Prediction of occult central lymph node metastasis in papillary thyroid carcinoma by preoperative BRAF analysis using fine-needle aspiration biopsy: a prospective study

CONTEXT

Few reports have determined whether preoperative detection of the BRAF V600E mutation in fine-needle aspiration biopsy (FNAB) may influence determination of surgical extent such as prophylactic central lymph node dissection (CLND) in patients with papillary thyroid carcinoma (PTC).

OBJECTIVES

Our objectives were to investigate whether preoperative BRAF analysis may assist determination of surgical extent, including prophylactic CLND with variable clinicopathological risk factors for central lymph node metastasis, in patients with PTC and clinically node-negative neck.

PATIENTS AND METHODS

From July 2009 to May 2011, we prospectively enrolled 148 PTC patients with clinically node-negative neck who received a total thyroidectomy and prophylactic CLND. BRAF mutation by pyrosequencing was tested on preoperative FNAB specimens. The relationships between occult central lymph node metastasis and preoperative BRAF mutation or clinicopathological factors were analyzed. Additionally, we assessed the associations between preoperative BRAF mutation status and various clinicopathological characteristics of PTC revealed postoperatively.

RESULTS

The prevalence of the BRAF V600E mutation was 53.4%, and the rate of occult central lymph node metastasis was 25.7%. Multivariate analysis showed that tumor size over 1 cm [P = 0.006; odds ratio (OR) = 3.559], perithyroidal invasion (P = 0.023; OR = 2.893), and preoperative positive BRAF mutation (P = 0.029; OR = 2.727) were independent risk factors for the presence of occult central lymph node metastasis. BRAF mutation examined in FNAB specimens, compared with the wild-type allele, strongly predicted perithyroidal invasion (48 vs. 29%; P = 0.017), extracapsular spread (65 vs. 45%; P = 0.017), occult central lymph node metastasis (35 vs. 15%; P = 0.004), and advanced TNM stage (44 vs. 28%; P = 0.035). In the multivariate analysis, patients with preoperative positive BRAF mutation were significantly more likely (P = 0.023; OR = 2.848) to have occult central lymph node metastasis.

CONCLUSION

Preoperative BRAF analysis by FNAB and primary tumor size based on ultrasonography may assist in predicting occult central lymph node metastasis in patients with PTC and clinically node-negative neck.

Long-term analysis of the efficacy and tolerability of sorafenib in advanced radio-iodine refractory differentiated thyroid carcinoma: final results of a phase II trial

OBJECTIVE

We conducted a prospective phase II clinical trial to determine the efficacy of sorafenib in patients with advanced radio-iodine refractory differentiated thyroid cancer. In this article, the long-term results are presented.

PATIENTS AND METHODS

Thirty-one patients with progressive metastatic or locally advanced radioactive iodine refractory differentiated thyroid cancer received sorafenib 400 mg orally twice daily. The study end points included response rate, progression-free survival (PFS), overall survival (OS), best response by Response Evaluation Criteria in Solid Tumors criteria 1.0, and toxicity.

RESULTS

Median PFS was 18 months (95% confidence interval (95% CI): 7-29 months) and median OS was 34.5 months (95% CI: 19-50 months). Eight patients (31%) achieved a partial response and 11 patients (42%) showed stable disease after a median follow-up of 25 months (range 3.5-39 months). Toxicity mostly included hand foot syndrome, weight loss, diarrhea, and rash.

CONCLUSION

Sorafenib has clinically relevant antitumor activity in patients with progressive metastatic or locally advanced radio-iodine refractory differentiated thyroid cancer. Sorafenib can nowadays be considered as the standard option in these patients.

Genetic alterations in poorly differentiated and undifferentiated thyroid carcinomas

Thyroid gland presents a wide spectrum of tumours derived from follicular cells that range from well differentiated, papillary and follicular carcinoma (PTC and FTC, respectively), usually carrying a good prognosis, to the clinically aggressive, poorly differentiated (PDTC) and undifferentiated thyroid carcinoma (UTC).It is usually accepted that PDTC and UTC occur either de novo or progress from a pre-existing well differentiated carcinoma through a multistep process of genetic and epigenetic changes that lead to clonal expansion and neoplastic development. Mutations and epigenetic alterations in PDTC and UTC are far from being totally clarified. Assuming that PDTC and UTC may derive from well differentiated thyroid carcinomas (WDTC), it is expected that some PDTC and UTC would harbour genetic alterations that are typical of PTC and FTC. This is the case for some molecular markers (BRAF and NRAS) that are present in WDTC, PDTC and UTC. Other genes, namely P53, are almost exclusively detected in less differentiated and undifferentiated thyroid tumours, supporting a diagnosis of PDTC or, much more often, UTC. Thyroid-specific rearrangements RET/PTC and PAX8/PPARγ, on the other hand, are rarely found in PDTC and UTC, suggesting that these genetic alterations do not predispose cells to dedifferentiation. In the present review we have summarized the molecular changes associated with the two most aggressive types of thyroid cancer.

Diagnostic and prognostic markers in differentiated thyroid cancer

The MAPK/ERK (mitogen-activated protein kinase/extracellular signal- regulated kinase signaling pathway) and PI3K/Akt (lipid kinase phoshoinositide-3-kinase signaling pathway) play an important role in transmission of cell signals through transduction systems as ligands, transmembrane receptors and cytoplasmic secondary messengers to cell nucleus, where they influence the expression of genes that regulate important cellular processes: cell growth, proliferation and apoptosis. The genes, coding the signaling cascade proteins (RET, RAS, BRAF, PI3K, PTEN, AKT), are mutated or aberrantly expressed in thyroid cancer derived from follicular thyroid cell. Genetic and epigenetic alternations, concerning MAPK/ERK and PI3K/Akt signaling pathways, contribute to their activation and interaction in consequence of malignant follicular cell transformation. Moreover, it is additionally pointed out that genetic, as well as epigenetic DNA changing via aberrant methylation of several tumor suppressor and thyroid-specific genes is associated with tumor aggressiveness, being a jointly responsible mechanism for thyroid tumorigenesis. In the present manuscript the currently developed diagnostic and prognostic genetic/epigenetic markers are presented; the understanding of this molecular mechanism provides access to novel molecular therapeutic strategies.

The insulin and igf-I pathway in endocrine glands carcinogenesis

Endocrine cancers are a heterogeneous group of diseases that may arise from endocrine cells in any gland of the endocrine system. These malignancies may show an aggressive behavior and resistance to the common anticancer therapies. The etiopathogenesis of these tumors remains mostly unknown. The normal embryological development and differentiation of several endocrine glands are regulated by specific pituitary tropins, which, in adult life, control the function and trophism of the endocrine gland. Pituitary tropins act in concert with peptide growth factors, including the insulin-like growth factors (IGFs), which are considered key regulators of cell growth, proliferation, and apoptosis. While pituitary TSH is regarded as tumor-promoting factor for metastatic thyroid cancer, the role of other pituitary hormones in endocrine cancers is uncertain. However, multiple molecular abnormalities of the IGF system frequently occur in endocrine cancers and may have a role in tumorigenesis as well as in tumor progression and resistance to therapies. Herein, we will review studies indicating a role of IGF system dysregulation in endocrine cancers and will discuss the possible implications of these findings for tumor prevention and treatment, with a major focus on cancers from the thyroid, adrenal, and ovary, which are the most extensively studied.

BRAF, GNAQ, and GNA11 mutations and copy number in pediatric low-grade glioma

Fifty-two samples of pediatric low-grade glioma (48 primary, 4 recurrent) were analyzed for BRAF copy number variation (digital PCR analysis, CopyCaller) and point mutations of BRAF V600E, and exon 5 Q209 in GNAQ, and GNA11, using the MALDI-TOF mass spectrometer with validation by direct sequencing. An increased BRAF copy number was found in 18/47 primary samples tested; 15 of them (83.3%) were pilocytic astrocytomas. A BRAF mutation was found in 3/48 primary tumors, all with a normal BRAF copy number and no GNAQ mutation. One sample had a GNAQ209 mutation (Q209P626) with a normal BRAF gene; none of the tumors had a GNA11Q209 mutation. Recurrent or progressive tumors, analyzed in four patients, had the same molecular genotype as their primary. Increased BRAF copy number and activating BRAF mutations may be involved in the development of low-grade glioma via overactivation of the Ras/Raf pathway. This is the first report of a mutation in GNAQ209 in pediatric low-grade glioma. Understanding the molecular mechanisms underlying glioma initiation and growth may assist in the development of targeted therapies.

New treatment modalities in advanced thyroid cancer

BACKGROUND

Thyroid cancer is a heterogeneous disease that is classified into differentiated thyroid carcinoma (DTC), undifferentiated/anaplastic thyroid carcinoma (ATC) and medullary thyroid carcinoma. Results of conventional treatment modalities in advanced thyroid cancer have been disappointing and therefore, new therapies are needed.

METHODS

We searched PubMed, The Cochrane Library, Medline and EMBASE databases and abstracts published in annual proceedings for new treatment modalities in advanced thyroid cancer. We also searched for ongoing trials in www.clinicaltrials.gov.

RESULTS

Six phase I, 17 phase II and 1 phase III trials with tyrosine kinase inhibitors were carried out. We found 2 pilot studies and 11 phase II trials with redifferentiation therapies, mainly in DTC. For antiproliferative approaches, three phase I and four phase II trials were found. Immunomodulatory gene therapy was tested in a pilot study in ATC patients. Two phase II trials were carried out with immunotherapy. One phase I and nine phase II trials were found with radionucleotide therapy in patients with DTC.

CONCLUSION

The developments in the treatment of advanced thyroid cancer are intriguing. Future trials should aim at combinations of targeted agents with or without other treatment modalities, and will hopefully contribute to further improvement of outcomes.

Multi-institutional phase II study of selumetinib in patients with metastatic biliary cancers

PURPOSE

Biliary cancers (BCs) carry a poor prognosis, but targeting the RAS/RAF/mitogen-activated protein kinase kinase (MEK)/extracellular signal-related kinase (ERK) pathway is of significance. Selumetinib is an inhibitor of MEK1/2, so this trial was designed to determine the safety and efficacy of selumetinib in BC.

PATIENTS AND METHODS

This was a multi-institutional phase II study of selumetinib at 100 mg given orally twice per day to patients with advanced BC. The primary end point was response rate. All patients were required to provide tissue before enrolling. The levels of phosphorylated ERK (pERK) and AKT (pAKT) were assessed by immunohistochemistry. Tumors were genotyped for the presence of BRAF- and/or RAS-activating mutations.

RESULTS

Twenty-eight eligible patients with a median age of 55.6 years were enrolled. Thirty-nine percent of patients had received one prior systemic therapy. Three patients (12%) had a confirmed objective response. Another 17 patients (68%) experienced stable disease (SD), 14 of whom (56%) experienced prolonged SD (> 16 weeks). Patients gained an average nonfluid weight of 8.6 pounds. Median progression-free survival was 3.7 months (95% CI, 3.5 to 4.9) and median overall survival was 9.8 months (95% CI, 5.97 to not available). Toxicities were mild, with rash (90%) and xerostomia (54%) being most frequent. Only one patient experienced grade 4 toxicity (fatigue). All patients had tissue available for analysis. No BRAF V600E mutations were found. Two patients with short-lived SD had KRAS mutations. Absence of pERK staining was associated with lack of response.

CONCLUSION

Selumetinib displays interesting activity and acceptable tolerability in patients with metastatic BC. Our results warrant further evaluation of selumetinib in patients with metastatic BC.

Multi-institutional phase II study of selumetinib in patients with metastatic biliary cancers

PURPOSE

Biliary cancers (BCs) carry a poor prognosis, but targeting the RAS/RAF/mitogen-activated protein kinase kinase (MEK)/extracellular signal-related kinase (ERK) pathway is of significance. Selumetinib is an inhibitor of MEK1/2, so this trial was designed to determine the safety and efficacy of selumetinib in BC.

PATIENTS AND METHODS

This was a multi-institutional phase II study of selumetinib at 100 mg given orally twice per day to patients with advanced BC. The primary end point was response rate. All patients were required to provide tissue before enrolling. The levels of phosphorylated ERK (pERK) and AKT (pAKT) were assessed by immunohistochemistry. Tumors were genotyped for the presence of BRAF- and/or RAS-activating mutations.

RESULTS

Twenty-eight eligible patients with a median age of 55.6 years were enrolled. Thirty-nine percent of patients had received one prior systemic therapy. Three patients (12%) had a confirmed objective response. Another 17 patients (68%) experienced stable disease (SD), 14 of whom (56%) experienced prolonged SD (> 16 weeks). Patients gained an average nonfluid weight of 8.6 pounds. Median progression-free survival was 3.7 months (95% CI, 3.5 to 4.9) and median overall survival was 9.8 months (95% CI, 5.97 to not available). Toxicities were mild, with rash (90%) and xerostomia (54%) being most frequent. Only one patient experienced grade 4 toxicity (fatigue). All patients had tissue available for analysis. No BRAF V600E mutations were found. Two patients with short-lived SD had KRAS mutations. Absence of pERK staining was associated with lack of response.

CONCLUSION

Selumetinib displays interesting activity and acceptable tolerability in patients with metastatic BC. Our results warrant further evaluation of selumetinib in patients with metastatic BC.

RAF kinase activity regulates neuroepithelial cell proliferation and neuronal progenitor cell differentiation during early inner ear development

Background

Early inner ear development requires the strict regulation of cell proliferation, survival, migration and differentiation, coordinated by the concerted action of extrinsic and intrinsic factors. Deregulation of these processes is associated with embryonic malformations and deafness. We have shown that insulin-like growth factor I (IGF-I) plays a key role in embryonic and postnatal otic development by triggering the activation of intracellular lipid and protein kinases. RAF kinases are serine/threonine kinases that regulate the highly conserved RAS-RAF-MEK-ERK signaling cascade involved in transducing the signals from extracellular growth factors to the nucleus. However, the regulation of RAF kinase activity by growth factors during development is complex and still not fully understood.

Methodology/Principal Findings

By using a combination of qRT-PCR, Western blotting, immunohistochemistry and in situ hybridization, we show that C-RAF and B-RAF are expressed during the early development of the chicken inner ear in specific spatiotemporal patterns. Moreover, later in development B-RAF expression is associated to hair cells in the sensory patches. Experiments in ex vivo cultures of otic vesicle explants demonstrate that the influence of IGF-I on proliferation but not survival depends on RAF kinase activating the MEK-ERK phosphorylation cascade. With the specific RAF inhibitor Sorafenib, we show that blocking RAF activity in organotypic cultures increases apoptosis and diminishes the rate of cell proliferation in the otic epithelia, as well as severely impairing neurogenesis of the acoustic-vestibular ganglion (AVG) and neuron maturation.

Conclusions/Significance

We conclude that RAF kinase activity is essential to establish the balance between cell proliferation and death in neuroepithelial otic precursors, and for otic neuron differentiation and axonal growth at the AVG.

Mutational and immunohistochemical study of the PI3K/Akt pathway in papillary thyroid carcinoma in Greece

PI3K/Akt signaling pathway plays critical role in many cell processes. There is indication that enhanced activation of PI3K/Akt cascade is implicated in thyroid tumors. Aim of this study was to evaluate the mutational status and expression of PI3K/Akt pathway mediators in papillary thyroid carcinoma in Greece. We evaluated the presence of mutations in PIK3CA (exons 9 and 20), AKT1 (exons 6-11), AKT2 (exons 6-11), AKT3 (exons 5-10), PTEN (exons 3-8), and PDPK1 (exons 4-10) genes in 83 papillary thyroid carcinomas by DNA sequencing. The expression levels of phospho-Akt and insulin-like growth factor I receptor (IGF-IR) were evaluated by immunohistochemistry. PIK3CA mutations were found in three samples. The analysis of AKT1 revealed one silent mutation in exon 9 (G726A) in 16 samples. One specimen carried an AKT3 mutation. One missense mutation was found in one sample in PTEN. No mutations were found in AKT2 and PDPK1. Increased levels of phosphorylated total Akt and IGF-IR were identified in some papillary cancers. Our findings indicate that PI3K/Akt signaling pathway is activated in some papillary tumors. However, mutations in genes coding most mediators of the pathway have not been proven to be the major modus of enhanced activation. These data suggest a potential role for PI3K/Akt-mediated signaling in papillary thyroid tumors.

Is BRAF mutation screening useful for preoperative risk stratification in papillary thyroid cancer?

Evaluation of: Xing M, Clark D, Guan H et al.: BRAF mutation testing of thyroid fine-needle aspiration biopsy specimens for preoperative risk stratification in papillary thyroid cancer. J. Clin. Oncol. 27(18), 2977–2982 (2009). Although the majority of patients with papillary thyroid cancer are effectively treated with thyroidectomy and selective use of postoperative 131I therapy, disease persistence/recurrence can afflict a proportion of patients after the initial treatments. BRAF mutations, present in a large proportion of papillary thyroid cancers, illustrate one of the most impressive examples of phenotype–genotype correlation in human pathology. In this study, the authors propose that preoperative BRAF mutation testing of fine-needle aspiration biopsy specimens provides a novel tool for a preoperative risk stratification strategy for predicting the extent of initial disease and subsequent clinical outcomes.

Multi-targeted approach in the treatment of thyroid cancer

Thyroid cancer is the most common malignancy of the endocrine system. There are several variants, ranging from well-differentiated cancers, such as papillary carcinomas, to poorly differentiated types, which carry a worse prognosis. Many patients with well-differentiated thyroid cancers are cured by surgical intervention alone, while others require adjuvant therapy. For those patients with more aggressive tumors, such as metastatic and anaplastic thyroid cancers, surgery rarely offers a definitive cure and alternative treatment methods such as chemotherapy do not improve survival. Due to the difficulty in treating aggressive thyroid cancers, other novel therapies are needed. In this paper, we will review current strategies for managing the various types of thyroid carcinomas. We will also address many of the studied genetic pathways and new therapeutic drug targets for treating individual thyroid malignancies.

MAPK pathway activation and the origins of pediatric low-grade astrocytomas

Low-grade astrocytomas (LGAs) are the most common type of brain tumor in children. Until recently, very little was known about the underlying biology and molecular genetics of these tumors. However, within the past year a number of studies have shown that the MAPK pathway is constitutively activated in a high proportion of LGAs. Several genetic aberrations which generate this deregulation of the MAPK pathway have been identified, most notably gene fusions between KIAA1549 and BRAF. In this review we summarize these findings, discuss how these gene fusions may arise and consider possible implications for diagnosis and treatment.

Proliferation and survival molecules implicated in the inhibition of BRAF pathway in thyroid cancer cells harbouring different genetic mutations

Background

Thyroid carcinomas show a high prevalence of mutations in the oncogene BRAF which are inversely associated with RAS or RET/PTC oncogenic activation. The possibility of using inhibitors on the BRAF pathway as became an interesting therapeutic approach. In thyroid cancer cells the target molecules, implicated on the cellular effects, mediated by inhibition of BRAF are not well established. In order to fill this lack of knowledge we studied the proliferation and survival pathways and associated molecules induced by BRAF inhibition in thyroid carcinoma cell lines harbouring distinct genetic backgrounds.

Methods

Suppression of BRAF pathway in thyroid cancer cell lines (8505C, TPC1 and C643) was achieved using RNA interference (RNAi) for BRAF and the kinase inhibitor, sorafenib. Proliferation analysis was performed by BrdU incorporation and apoptosis was accessed by TUNEL assay. Levels of protein expression were analysed by western-blot.

Results

Both BRAF RNAi and sorafenib inhibited proliferation in all the cell lines independently of the genetic background, mostly in cells with BRAF^V600E mutation. In BRAF^V600E mutated cells inhibition of BRAF pathway lead to a decrease in ERK1/2 phosphorylation and cyclin D1 levels and an increase in p27^Kip1. Specific inhibition of BRAF by RNAi in cells with BRAF^V600E mutation had no effect on apoptosis. In the case of sorafenib treatment, cells harbouring BRAF^V600E mutation showed increase levels of apoptosis due to a balance of the anti-apoptotic proteins Mcl-1 and Bcl-2.

Conclusion

Our results in thyroid cancer cells, namely those harbouring BRAF^V600Emutation showed that BRAF signalling pathway provides important proliferation signals. We have shown that in thyroid cancer cells sorafenib induces apoptosis by affecting Mcl-1 and Bcl-2 in BRAF^V600E mutated cells which was independent of BRAF. These results suggest that sorafenib may prove useful in the treatment of thyroid carcinomas, particularly those refractory to conventional treatment and harbouring BRAF mutations.

Molecular markers of aggressiveness of thyroid cancer

PURPOSE OF REVIEW

To review recent progress at defining molecular markers that predict the biological behavior of thyroid cancer.

RECENT FINDINGS

Thyroid cancer behavior is defined by the effects of the initiating oncogene as well as secondary events in tumor cells and the tumor microenvironment that are both genetic and epigenetic. Over the past several years, there has been intense focus on identifying molecular markers to better predict the aggressiveness of thyroid cancers and also to define therapeutic targets. The results of recent articles in this area of work are summarized with a focus of differentiated follicular-cell-derived forms of thyroid cancer.

SUMMARY

Clinical staging predicts tumor behavior in many cases, but does not allow true 'personalization' of initial therapy or identify potential therapeutic targets for patients with progressive disease that does not respond to standard therapies. Recent data point to several new opportunities to refine thyroid cancer treatment based on molecular information. Several highlighted articles have begun to apply this information with clinical intent.

BRAFV600E mutation in papillary thyroid carcinoma: a potential target for therapy?

This article reviews the therapeutic significance of the close genotype-phenotype association in papillary thyroid carcinoma, namely regarding the association between genetic alterations in RET, BRAF or RAS genes and the histopathological variants of papillary thyroid carcinoma. Based upon the aforementioned review on morphology and molecular pathology, the most recent prognostic and therapeutic data are reviewed and the role of targeted therapies, namely those interfering with BRAF-activated pathways are discussed, which may play a role in the treatment of patients with papillary thyroid carcinoma unresponsive to radioactive iodine.