Pathways In Thyroid Cancer Research Articles

Blocks to thyroid cancer cell apoptosis can be overcome by inhibition of the MAPK and PI3K/AKT pathways

Current treatment for recurrent and aggressive/anaplastic thyroid cancers is ineffective. Novel targeted therapies aimed at the inhibition of the mutated oncoprotein BRAFV600E have shown promise in vivo and in vitro but do not result in cellular apoptosis. TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a tumor-selective manner by activating the extrinsic apoptotic pathway. Here, we show that a TRAIL-R2 agonist antibody, lexatumumab, induces apoptosis effectively in some thyroid cancer cell lines (HTh-7, TPC-1 and BCPAP), while more aggressive anaplastic cell lines (8505c and SW1736) show resistance. Treatment of the most resistant cell line, 8505c, using lexatumumab in combination with the BRAFV600E inhibitor, PLX4720, and the PI3K inhibitor, LY294002, (triple-drug combination) sensitizes the cells by triggering both the extrinsic and intrinsic apoptotic pathways in vitro as well as 8505c orthotopic thyroid tumors in vivo. A decrease in anti-apoptotic proteins, pAkt, Bcl-xL, Mcl-1 and c-FLIP, coupled with an increase in the activator proteins, Bax and Bim, results in an increase in the Bax to Bcl-xL ratio that appears to be critical for sensitization and subsequent apoptosis of these resistant cells. Our results suggest that targeting the death receptor pathway in thyroid cancer can be a promising strategy for inducing apoptosis in thyroid cancer cells, although combination with other kinase inhibitors may be needed in some of the more aggressive tumors initially resistant to apoptosis.

Revealing Biological Pathways Implicated in Lung Cancer from TCGA Gene Expression Data Using Gene Set Enrichment Analysis.

Analyzing biological system abnormalities in cancer patients based on measures of biological entities, such as gene expression levels, is an important and challenging problem. This paper applies existing methods, Gene Set Enrichment Analysis and Signaling Pathway Impact Analysis, to pathway abnormality analysis in lung cancer using microarray gene expression data. Gene expression data from studies of Lung Squamous Cell Carcinoma (LUSC) in The Cancer Genome Atlas project, and pathway gene set data from the Kyoto Encyclopedia of Genes and Genomes were used to analyze the relationship between pathways and phenotypes. Results, in the form of pathway rankings, indicate that some pathways may behave abnormally in LUSC. For example, both the cell cycle and viral carcinogenesis pathways ranked very high in LUSC. Furthermore, some pathways that are known to be associated with cancer, such as the p53 and the PI3K-Akt signal transduction pathways, were found to rank high in LUSC. Other pathways, such as bladder cancer and thyroid cancer pathways, were also ranked high in LUSC.

Key genes and pathways in thyroid cancer based on gene set enrichment analysis

The incidence of thyroid cancer and its associated morbidity has shown the most rapid increase among all cancers since 1982, but the mechanisms involved in thyroid cancer, particularly significant key genes induced in thyroid cancer, remain undefined. In many studies, gene probes have been used to search for key genes involved in causing and facilitating thyroid cancer. As a result, many possible virulence genes and pathways have been identified. However, these studies lack a case contrast for selecting the most possible virulence genes and pathways, as well as conclusive results with which to clarify the mechanisms of cancer development. In the present study, we used gene set enrichment and meta-analysis to select key genes and pathways. Based on gene set enrichment, we identified 5 downregulated and 4 upregulated mixed pathways in 6 tissue datasets. Based on the meta-analysis, there were 17 common pathways in the tissue datasets. One pathway, the p53 signaling pathway, which includes 13 genes, was identified by both the gene set enrichment analysis and meta-analysis. Genes are important elements that form key pathways. These pathways can induce the development of thyroid cancer later in life. The key pathways and genes identified in the present study can be used in the next stage of research, which will involve gene elimination and other methods of experimentation.

Abstract 3098: MiRNA-145 is a master regulator of the hallmarks of thyroid cancer.

Abstract microRNA-145 (miR-145) in an important member of the family of microRNAs which are downregulated in several types of tumors. However, miR-145 expression and function in thyroid cancer and in cellular differentiation is unknown. In our study, we performed miRNA profiling in normal, benign and malignant thyroid cancers including undifferentiated tumors with validation of differentially expressed miRNAs by quantitative RT PCR. We found significant downregulation of miR-145 in differentiated and undifferentiated thyroid cancer. We performed functional studies in thyroid cancer cell lines and found that miR-145 decreases cell proliferation, induces cell cycle arrest, decreases cell invasion and targets the PI3K/Akt pathway, one of the most commonly activated pathways in thyroid cancer and which is associated with epithelial-mesenchymal transition (EMT). Overexpression of miR-145 in cell lines also decreased the expression of EMT markers vimentin and N-cadherin. Furthermore, inhibition of miR-145 in normal primary thyroid cultured cells decreased NIS and PAX8 expression, key regulators of thyroid cell differentiation. miRNA-145 expression in tumor tissue was inversely correlated with VEGF serum levels in the same patients and overexpression of miR-145 in vitro decreased angiogenesis and VEGF secretion. MiRNA-145 has important regulatory effects on the hallmarks of thyroid cancer cells and thus may be involved in thyroid cancer progression. Citation Format: Myriem Boufraqech, Lisa Zhang, Meenu Jain, Neelam Gulati, Naris Nilubol, Mio Kitano, Yin Xiong, Electron Kebebew. MiRNA-145 is a master regulator of the hallmarks of thyroid cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3098. doi:10.1158/1538-7445.AM2013-3098

Role of the Wnt Pathway in Thyroid Cancer

Aberrant activation of Wnt signaling is involved in the development of several epithelial tumors. Wnt signaling includes two major types of pathways: (i) the canonical or Wnt/β-catenin pathway; and (ii) the non-canonical pathways, which do not involve β-catenin stabilization. Among these pathways, the Wnt/β-catenin pathway has received most attention during the past years for its critical role in cancer. A number of publications emphasize the role of the Wnt/β-catenin pathway in thyroid cancer. This pathway plays a crucial role in development and epithelial renewal, and components such as β-catenin and Axin are often mutated in thyroid cancer. Although it is accepted that altered Wnt signaling is a late event in thyroid cell transformation that affects anaplastic thyroid tumors, recent data suggest that it is also altered in papillary thyroid carcinoma (PTC) with RET/PTC mutations. Therefore, the purpose of this review is to summarize the main relevant data of Wnt signaling in thyroid cancer, with special emphasis on the Wnt/β-catenin pathway.

Genetic Alterations in the Phosphatidylinositol-3 Kinase/Akt Pathway in Thyroid Cancer

Aberrant activation of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway plays a fundamental role in thyroid tumorigenesis, particularly in follicular thyroid cancer (FTC) and aggressive thyroid cancer, such as anaplastic thyroid cancer (ATC). As the drivers of this process, many genetic alterations activating the PI3K/Akt pathway have been identified in thyroid cancer in recent years. This review summarizes the current knowledge on major genetic alterations in the PI3K/Akt pathway. These include PIK3CA mutations and genomic amplification/copy gain, Ras mutations, PTEN mutations, RET/PTC and PPARgamma/Pax8 rearrangements, as well as amplification/copy gain of PIK3CB, PDK1, Akt, and various receptor tyrosine kinase genes. Most of these genetic alterations are particularly common in FTC and many of them are even more common in ATC; they are generally less common in papillary thyroid cancer (PTC), in which the MAP kinase (MAPK) pathway activated by the BRAF mutation instead plays a major role. Methylation and, thus, epigenetic silencing of PTEN, a major negative regulator of the PI3K/Akt pathway, occurs in close association with activating genetic alterations of the PI3K/Akt pathway, constituting a unique self-enhancement mechanism for this pathway. Many of these genetic alterations are mutually exclusive in differentiated thyroid tumors, but with increasing concurrence from benign tumors to FTC to ATC. RET/PTC, Ras, and receptor tyrosine kinase could dually activate the PI3K/Akt and MAPK pathways. Most cases of ATC harbor genetic alterations in these genes or other genetic combinations that can activate both pathways. It is proposed that genetic alterations in the PI3K/Akt pathway promote thyroid cell transformation to FTC and that genetic alterations in the MAPK pathway promote cell transformation to PTC; accumulation of multiple genetic alterations that can activate both pathways promotes thyroid cancer aggressiveness and progression to ATC. Genetic alterations are common in the PI3K/Akt pathway in thyroid cancer and play a fundamental role in the tumorigenesis and progression of this cancer. This provides a strong basis for the emerging development of novel genetic-based diagnostic, prognostic, and therapeutic strategies for thyroid cancer.

Phase I trial of combination sorafenib and tipifarnib: The experience in advanced differentiated thyroid cancer (DTC) and medullary thyroid cancer (MTC).

5586 Background: Metastatic, progressive thyroid cancer, not amenable to standard treatment, is a deadly disease. Ras/Raf/MEK/ERK is the most important pathway in thyroid cancer. Sorafenib has activity against BRAF, RET and VEGFR. Tipifarnib inhibits farnesyl transferase, preventing activation of Ras and selectively killing Ras-transformed cells. Methods: As part of a phase I trial, we treated 35 differentiated and medullary thyroid cancer patients. Secondary endpoints included efficacy. Sorafenib and tipifarnib were given for 21 days and repeated every 28. RECIST was used to determine response. Results: We enrolled 22 patients with metastatic DTC (16 PTC, 5 FTC, 1 poorly differentiated), 13 with MTC, of which 15 DTC and 10 MTC patients were restaged. Ten patients were discontinued from the study prior to first re-staging due to toxicities. Best response in DTC: 1/15 (7%) PR, 13/15 (86%) SD, 1/15 (7%) PD; MTC: 5/10 (50%) PR, 5/10 (50%) SD, 0/10 PD. Durable responses (PR or SD ≥6 months): 13/15 (87%) of DTC; 9/10 (90%) of MTC. The median follow up was 19 months in DTC and 27 months in MTC. Median PFS was 20 months in the DTC group and 15 months in MTC. Median overall survival has not been reached in either group, but at 24 months, overall survival was 79% in DTC and 88% in MTC. Major dose-limiting toxicities in this cohort were grade 3 rash in 4/36 (11%). Other common skin toxicites were grade 1-2 hand-foot skin reaction 13/35 (37%); grade 1-2 rash 15/35 (43%). Maximum tolerated dose was sorafenib 600mg/tipifarnib 200mg (split dosing). Conclusions: Combination sorafenib/tipifarnib is promising for treatment of metastatic DTC and MTC, however, further evaluation in phase II trials is warranted. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Bayer, Johnson & Johnson Bayer, Johnson & Johnson Bayer

Abstract 5075: PI3K activation restores KrasG12D oncogenic ability in a mouse model of follicular thyroid cancer by directly opposing multiple Kras-initiated negative feedback signals

Abstract Activating mutations of Ras family members and aberrant activation of the PI3K/AKT pathway are quite common in thyroid cancer originating from the follicular epithelium. We have recently shown in a relevant in vivo model that, contrary to many other cell types, Kras activation is unable to induce oncogenic transformation of the thyroid follicular cells. However, PI3K activation is able to potently cooperate with Kras oncogenic mutation, thus inducing aggressive and metastatic thyroid follicular carcinomas. We now show that one key event mediated by PI3K in this cross-talk is the inhibition of multiple Kras-initiated negative feedback signals shutting down MAPK signaling and the induction of proliferation. Through these mechanisms, PI3K signaling restores Kras-initiated MAPK activation, induction of proliferation, and oncogenic transformation. In particular, our data reveal that activation of p38α MAPK, as well as up-regulation of MKP2 and MKP3 phosphatases, play a pivotal role in mediating the growth-suppressive negative feedback initiated by Kras oncogenic activation. Activation of p38α MAPK acts by inducing cell cycle arrest and the establishment of cellular senescence, while MKP2 and MKP3 stunt ERK1/2 activation through direct dephosphorylation of these kinases. Strikingly, we have found that PI3K acts through Akt1 (but not Akt2) to potently suppress p38 phosphorylation and activation. Furthermore, PI3K activation results in the transcriptional repression of MKP2 and MKP3 promoters. Through these two molecular mechanisms, PI3K activation contributes to unleashing to its full extent Kras oncogenic ability. These data not only uncover novel oncogenic pathways controlled by PI3K signaling, but also further strengthen the rationale for the dual targeting of PI3K and MAPK pathways in thyroid cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5075.

Targeting the RET Pathway in Thyroid Cancer

The RET (rearranged during transfection) protooncogene encodes a single pass transmembrane receptor that is expressed in cells derived from the neural crest and the urogenital tract. As part of a cell-surface complex, RET binds glial derived neurotrophic factor (GDNF) ligands in conjunction with GDNF-family alpha co-receptors (GFRalpha). Ligand-induced activation induces dimerization and tyrosine phosphorylation of the RET receptor with downstream activation of several signal transduction pathways. Activating germline RET mutations play a central role in the development of the multiple endocrine neoplasia (MEN) syndromes MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC) and also in the development of the congenital abnormality Hirschsprung's disease. Approximately 50% of patients with sporadic MTC have somatic RET mutations, and a significant portion of papillary thyroid carcinomas result from chromosomal inversions or translocations, which activate RET (RET/PTC oncogenes). The RET protooncogene has a significant place in cancer prevention and treatment. Timely thyroidectomy in kindred members who have inherited a mutated RET allele, characteristic of MEN2A, MEN2B, or FMTC, can prevent MTC, the most common cause of death in these syndromes. Also, recently developed molecular therapeutics that target the RET pathway have shown activity in clinical trials of patients with advanced MTC, a disease for which there has been no effective therapy.

Oncogenic Kras Requires Simultaneous PI3K Signaling to Induce ERK Activation and Transform Thyroid Epithelial Cells In vivo

Thyroid tumors arising from the follicular cells often harbor mutations leading to the constitutive activation of the PI3K and Ras signaling cascades. However, it is still unclear what their respective contribution to the neoplastic process is, as well as to what extent they interact. We have used mice harboring a Kras oncogenic mutation and a Pten deletion targeted to the thyroid epithelium to address in vivo these questions. Here, we show that although each of these two pathways, alone, is unable to transform thyroid follicular cells, their simultaneous activation is highly oncogenic, leading to invasive and metastatic follicular carcinomas. In particular, phosphatidylinositol-3-kinase (PI3K) activation suppressed Kras-initiated feedback signals that uncouple mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) and ERK activation, thus stunting MAPK activity; in addition, PI3K and Kras cooperated to drastically up-regulate cyclin D1 mRNA levels. Finally, combined pharmacologic inhibition of PI3K and MAPK completely inhibited the growth of double-mutant cancer cell lines, providing a compelling rationale for the dual targeting of these pathways in thyroid cancer.

Genetic Alterations and Their Relationship in the Phosphatidylinositol 3-Kinase/Akt Pathway in Thyroid Cancer

To investigate the overall occurrence and relationship of genetic alterations in the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in thyroid tumors and explore the scope of this pathway as a therapeutic target for thyroid cancer. We examined collectively the major genetic alterations and their relationship in this pathway, including PIK3CA copy number gain and mutation, Ras mutation, and PTEN mutation, in a large series of primary thyroid tumors. Occurrence of any of these genetic alterations was found in 25 of 81 (31%) benign thyroid adenoma (BTA), 47 of 86 (55%) follicular thyroid cancer (FTC), 21 of 86 (24%) papillary thyroid cancer (PTC), and 29 of 50 (58%) anaplastic thyroid cancer (ATC), with FTC and ATC most frequently harboring these genetic alterations. PIK3CA copy gain was associated with increased PIK3CA protein expression. A mutual exclusivity among these genetic alterations was seen in BTA, FTC, and PTC, suggesting an independent role of each of them through the PI3K/Akt pathway in the tumorigenesis of the differentiated thyroid tumors. However, coexistence of these genetic alterations was increasingly seen with progression from differentiated tumor to undifferentiated ATC. Their coexistence with BRAF mutation was also frequent in PTC and ATC. The data provide strong genetic implication that aberrant activation of PI3K/Akt pathway plays an extensive role in thyroid tumorigenesis, particularly in FTC and ATC, and promotes progression of BTA to FTC and to ATC as the genetic alterations of this pathway accumulate. Progression of PTC to ATC may be facilitated by coexistence of PI3K/Akt pathway-related genetic alterations and BRAF mutation. The PI3K/Akt pathway may thus be a major therapeutic target in thyroid cancers.

PTTG promotes a novel VEGF‐KDR‐ID3 autocrine mitogenic pathway in thyroid cancer

Background. VEGF exerts its effects by binding to tyrosine kinase receptors, KDR and VEGFR1. KDR is critical for transmitting signals for proliferation of endothelial cells but is also expressed in several non‐endothelial cells suggesting existence of autocrine stimulatory pathways. Study‐design. We investigated VEGF and KDR expression in human thyroid epithelial cells in vitro and thyroid cancers samples ex vivo. Results. Expression of KDR was demonstrated using Taqman RT‐PCR and Western blotting in a human follicular thyroid cancer line (FTC133) and primary thyroid epithelial cells. Further, VEGF‐specific and dose‐dependent activation of KDR‐dependent MAPK signalling and KDR‐dependent mitogenesis was demonstrated. KDR mRNA expression was elevated in thyroid cancers (2.5‐fold, n = 38, P < 0.001), and immunohistochemistry demonstrated stronger phosphorylated‐KDR staining in thyroid cancer cells. Further, we showed that PTTG, an oncogene known to promote angiogenesis, up‐regulates KDR (2.2‐fold, P = 0.006) and VEGF (2.4‐fold, P < 0.001) expression in FTC133 thyroid cells. Next, we examined expression of ID3, known to be important in VEGF‐dependent angiogenesis, and VEGF mRNA expression in a series of thyroid cancers. We observed a strong positive correlation between expression of these genes (R2 = 0.62, P < 0.001). Stimulation of FTC133 cells with exogenous VEGF increased ID3 expression (2.1‐fold, P < 0.001), an effect abrogated by a KDR‐specific inhibitor, suggesting VEGF regulation of ID3 is KDR‐dependent. Conclusion. We suggest the presence of a VEGF‐KDR‐ID3 dependent autocrine pathway in thyroid cells. By up‐regulating both VEGF and KDR expression, we propose that PTTG may promote this autocrine proliferative pathway which may in turn be critical to thyroid cancer progression.

Involvement of Wnt pathway in thyroid cancer around Semipalatinsk Nuclear Test Site

A total of 459 nuclear tests were officially conducted at the Semipalatinsk Nuclear Test Site of Kazakhstan during the period from 1949 to 1989. The exposure to radioactive fallout could affect the population health. The aberrant activation of Wnt pathway elements is linked to thyroid tumorigenesis. The activated Wnt signaling stabilizes β-catenin and results in transactivation of target genes including cyclin D1. To investigate the involvement of the Wnt/β-catenin pathway in thyroid carcinomas around the Semipalatinsk Nuclear Test Site, we compared immunohistochemical results for β-catenin and cyclin D1 expression in chronic thyroiditis, follicular adenoma and papillary carcinoma. This study revealed a higher prevalence of both aberrant β-catenin expression and cyclin D1 overexpression in papillary thyroid cancers around the Semipalatinsk Nuclear Test Site than sporadic cases. The analysis of the alteration of the Wnt signaling-related molecules in thyroid cancer around the Semipalatinsk Nuclear Test Site may be important to gain an insight into radiation-induced thyroid tumorigenesis.