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Molecular Biology, Pathobiology and Genetics |
1 Institute of Molecular Pathology and Immunology of Porto University, Porto, Portugal; 2 Dipartimento di Biologia e Patologia Cellulare e Molecolare, Universita "Federico II" di Napoli/Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Naples, Italy; 3 Department of Public Health and Preventive Medicine, School of Medicine, Oviedo University; 4 Department of Otolaryngology, Hospital Universitario Central de Asturias; 5 Department of Pathology, School of Medicine, Instituto Universitario de Oncología del Principado de Asturias, Oviedo, Spain; and 6 Department of Pathology, Hospital Clinico Universitario de Santiago de Compostela, Santiago de Compostela, Spain
Requests for reprints: Ginesa García-Rostán, Institute of Molecular Pathology and Immunology of Porto University, Rua Roberto Frias s/n, 4200-465 Porto, Portugal. Phone: 351-22-557-0700; Fax: 351-22-557-0799; E-mail: grostan{at}ipatimup.pt.
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of a class IA phosphatidylinositol 3'-kinase (PI3K). PI3K is a component of the PTEN/PI3K/AKT pathway that regulates fundamental cellular processes linked to tumorigenesis, including cell cycle progression, cell survival, adhesion, motility and spreading, angiogenesis, glucose homeostasis, and cell size and organ size control (1, 2). Available genetic evidences strongly suggest that the PTEN/PI3K/AKT pathway constitutes a pivotal signaling cascade in thyroid carcinogenesis (3–10). Signaling through PI3K begins with signals relayed to the internal cellular environment by transmembrane receptor tyrosine kinases (RTK). Upon ligand activation, RTKs engage the p85-regulatory subunit of PI3K that forms a heterodimer with the p110-catalytic subunit (PIK3CA) leading to the membrane recruitment of PI3K and the generation of phosphatidylinositol-3-4-5-triphosphate (PIP3). Subsequently, PIP3 acts as membrane-embedded second messenger that bind the pleckstrin homology domain of two serine/threonine protein kinases, PDK1 and Akt, which colocalize at the membrane. Once in the membrane, Akt is activated, in part through phosphorylation by PDK1, and is then capable of phosphorylating several downstream targets, enhancing cell proliferation and survival (1, 2). The cell has evolved, however, a mechanism for switching "off" the PI3K signaling in both the normal response to growth stimuli and the abnormal response to transforming signals. The PTEN lipid phosphatase, by removing a phosphate group from the inositol ring of PIP3, is responsible for turning "off" the PI3K pathway, antagonizing the activity of Akt (1, 2). In thyroid cancer, it has been shown that PTEN inactivation and Akt activation are associated with tumor progression. PTEN is down-regulated or lost among highly malignant or late-stage thyroid cancers as the anaplastic thyroid carcinoma (ATC; >50%; refs. 3–8), and Akt activation correlates with regions of tumor invasion and with tumor metastases (9, 10). Because loss of PTEN function is regarded as a critical step in the progression of thyroid cancer, it is reasonable to hypothesize that PI3K activation through gain-of-function mutations might have similar effects. In fact, four recent studies, focused in establishing if PI3Ks are genetically altered in human cancers, have revealed a high frequency of PIK3CA somatic mutations (25-40%) among colorectal, gastric, breast, ovarian cancer, and high-grade brain tumors, being the majority of the mutants located within the helical (exon 9) and the kinase (exon 20) domains (11–16). In the attempt to improve our present knowledge about the PTEN/PI3K/AKT pathway in the development and progression of thyroid cancer, we investigated in this study the existence of PIK3CA mutations in 80 well-differentiated thyroid carcinomas of follicular (WDFC) and papillary (WDPC) type and 70 ATC. |
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DNA isolation. Overall, DNA was isolated from 248 tissue samples (189 tumor and 59 nontumoral samples). Whenever necessary, tumor material was microdissected to increase the proportion of cancer cells that always represented at least 80% of the total. Genomic DNA was extracted from tissue samples accordingly to a previously described phenol-chloroform method (18) and from the thyroid cancer cell lines with the Puregene DNA isolation kit (Gentra Systems, Minneapolis, MN).
Mutational and sequencing analysis. Mutational analysis was limited to the helical domain encoded by exon 9 and the kinase domain encoded by exon 20 because recent large-scale analyses of PIK3CA mutations in different tumor types revealed that 80% of the mutations clustered within those domains (11, 13). Genomic DNA was evaluated for the existence of mutations by PCR of the target sequences followed by direct sequencing. Primer pairs flanking PIK3CA exons 9 and 20 were specifically designed to avoid the frequent cross-amplification of chromosome 22q observed with those previously reported. Primer sequences were as follows: exon 9 forward, 5'-ATCATCTGTGAATCCAGA-3'; exon 9 reverse, 5'-TTAGCACTTACCTGTGAC-3'; exon 20 forward, 5'-TGACATTTGAGCAAAGACC-3'; and exon 20 reverse, 5'-GTGTGGAATCCAGAGTGA-3'. The PCR was carried out in 30 µL of reaction mixture containing 20 to 100 ng of genomic DNA, 0.5 µmol/L of each exon 9 primer, 0.25 µmol/L of each exon 20 primer, 200 µmol/L deoxynucleotide triphosphates, 3 mmol/L MgCl2, 1x buffer/MgCl2 free, and 1 unit of DNA polymerase. The mixture was heated for 10 minutes at 95°C for initial target strand dissociation followed by 40 cycles of denaturation (45 seconds at 94°C), annealing (45 seconds at 55°C for exon 9 and 58°C for exon 20), and extension (45 seconds at 72°C). Yield products were electrophoresed onto 3% agarose gels to verify the adequacy of the PCR reaction and purified using the GFX PCR DNA and gel band purification Kit (Amersham Biosciences, Piscataway, NJ). Direct sequencing was done in a capillary automatic sequencer (ABI PRISM 3100 Genetic Analyzer, Applied Biosystems, Foster City, CA) using the BigDye terminator v3.1 cycle sequencing kit (Applied Biosystems) and the aforementioned primers. Nucleotide sequencing from both the sense and antisense orientation was done for confirmation. All mutated cases were verified by repeated PCR from a new DNA template and sequencing.
Immunohistochemistry for phospho-Akt. A tissue microarray (TMA) of ATC, including 38 of the tumors analyzed for PIK3CA mutations, was used to carry out the immunohistochemical analysis of phospho-Akt. To improve the representativity of the expression analyses, two to six core biopsies of 1 mm in diameter from different regions of the same specimen or different blocks of the tumor were included in the TMA block (192 tissue cores). In addition, whenever observed, within a particular tumor, a concurrent better-differentiated component representative tissue cores from that area were also extruded into the recipient TMA block. To ensure the reproducibility of the results, phospho-Akt was evaluated in two consecutive TMA slides. Each section was deparaffinized, soaked in ethanol and, after treatment by immersion in a conventional steamer with antigen unmasking solution [buffer Tris-EDTA (pH 9.0), DAKO, Glostrup, Denmark] at 90°C for 40 minutes, incubated with blocking solution at room temperature. Anti-phospho-Akt (Ser473) polyclonal antibody (immunohistochemistry specific; Cell Signaling Technology, Beverly, MA) was then applied to sections at 1:25 dilution. After incubation with the primary antibody, immunodetection was done using a universal secondary antibody kit that incorporates a peroxidase-conjugated labeled dextran polymer (Peroxidase/3,3'-Diaminobenzidine EnVision System for polyclonal antibodies, DAKO). Negative controls by omitting the primary antibody were included in the assay. Immunoreactivity was expressed as the percentage of positively stained target cells in four intensity categories (–, staining; +, low/weak; ++, moderate/distinct; +++, high/intense). The presence or absence of staining was independently estimated by two blinded investigators (G.G.R. and J.C.T.), and a consensus was reached on all values used for computation.
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Within the ATC group, in 56 patients, it was known the existence of vascular invasion (86%, 48 cases), extrathyroidal extension (98%, 55 cases), spread of tumor cells (70%, 39 cases), lymph node metastases (46%, 26 cases), and distant metastases (41%, 23 cases) at diagnosis. Although the 16 PIK3CA-mutated ATC were commonly associated with vascular invasion (81%, 13 cases), extrathyroidal extension (100%, all 16 cases), spread of tumor cells (62.5%, 10 cases), lymph node metastases (50%, eight cases), and distant metastases (37.5%, six cases) at diagnosis, the correlation between PIK3CA mutations and all the unfavorable clinicopathologic variables listed above did not reach statistical significance due to the uniformly poor prognosis of ATC in this series. However, the comparison of PIK3CA mutations with clinicopathologic variables in all the thyroid carcinoma patients (ATC, WDFC, and WDPC), for which it was recorded that information, showed that missense PIK3CA mutations were more frequent among males (P = 0.28, Fisher's exact test) and were significantly correlated with age 
58 years old (P = 0.028, Fisher's exact test) and extrathyroidal extension (P = 0.020, Fisher's exact test). No attempt was made to correlate PIK3CA mutations with patient survival, because all the ATC patients in this series died within 1 year of the diagnosis.
PIK3CA mutations and clinicopathologic features of well-differentiated carcinomas. On microscopic examination, one of the two WDFC bearing missense, somatic mutations was a widely invasive tumor (one of three studied, 33%). The other positive WDFC was a minimally invasive tumor (1 of 10 studied, 10%; see Fig. 2). Of note, this was the only minimally invasive WDFC that behaved aggressively, developing distant metastases 17 months after surgery and killing the patient in 57 months from diagnosis. This minimally invasive WDFC disclosed the H1047R mutation, the most commonly targeted residue at the kinase domain of PIK3CA in different tumor types with demonstrated oncogenic-transforming activity (19).
The WDPC mutated at PIK3CA, despite being only 4 cm in diameter, was a highly infiltrative tumor that by the time of diagnosis had invaded the trachea and the esophagus. Indeed, it was the only WDPC that behaved very aggressively killing the patient in 1 month from diagnosis. Phenotypically, it displayed a mixed pattern of growth, with areas showing the classic papillary architecture intermingled with areas exhibiting a follicular pattern of growth. Of note, the E545Q amino acid substitution, which represents the most frequently mutated residue of PIK3CA in ovarian (15) and colon cancer (11), was only observed in the area with a follicular pattern of growth. Identical mutation arose in the lymph node metastasis analyzed from that patient.
Fourteen of 19 (74%) patients diagnosed of WDFC and 18 of 21 (86%) patients diagnosed of WDPC, with available follow-up data, were alive without any evidence of disease after an average follow-up period of 6 years on each group. Five WDFC patients (26%), including those whose tumors harbored PIK3CA missense mutations, developed lung and/or bone metastases between 2 and 26 months from diagnosis, dying of disease in 3 years of average follow-up. Three WDPC patients (14%), including the only one whose tumor resulted PIK3CA positive, died of disease in 2 years of average follow-up. Statistical analysis showed a borderline correlation between the presence of missense mutations in WDFC and the development of distant metastases during the follow-up (P = 0.05, Fisher's exact text). Among WDFC, missense mutations were also more frequently detected in males (P = 0.13, Fisher's exact text) and tumors >5.5 cm in diameter (P = 0.087, Fisher's exact test).
Correlation of PIK3CA mutations with Ras, BRAF, and P53 status in anaplastic thyroid cancer. All but one of the thyroid carcinomas (69 ATC, 54 WDPC, and 26 WDFC) included in this study had been analyzed for Ras (H-ras, K-ras, and N-Ras) mutations (data partially reported in ref. 20) and for BRAF mutations.7 No statistically significant association was found between Ras or BRAF oncogenic activation and PIK3CA mutations in ATC. Twenty-eight percent of the ATC wild type at PIK3CA (15 of 54) were mutated at Ras and 33% of the ATC mutated at PIK3CA (5 of 15) harbored also a Ras mutation. Likewise, 24% of the ATC wild type at PIK3CA (13 of 54) displayed a BRAF mutation and 40% of the PIK3CA mutated ATC (6 of 15) were concurrently mutated at BRAF. As expected, no ATC was simultaneously mutated at Ras and BRAF, as recognized alternative events in thyroid tumorigenesis (21). More than half of the ATC wild type at PIK3CA (28 of 54, 52%) were mutated at Ras or at BRAF. Our finding of coexisting PIK3CA/Ras mutations or PIK3CA/BRAF mutations in 11 ATC (73%; Table 2) is consistent with previous observations in colon cancer (11). Sixty-two percent (43 of 69) of the ATC were mutated in at least one of the three genes.
Data not shown of p53 expression, in a TMA with 38 of the ATC studied for PIK3CA mutations (including 10 PIK3CA mutation positive), were available for the correlation with PIK3CA mutations. Seventy-nine percent of the ATC wild type at PIK3CA (22 of 28) exhibited high to moderate levels of p53 immunoreactivity and 70% of the ATC mutated at PIK3CA (7 of 10) showed also distinct levels of p53 staining. Although the statistical analysis did not revealed a significant association between p53 protein expression and PIK3CA mutations, the frequent coexistence of p53 inactivation and PI3K activation in some ATC suggests that the two events may cooperate in thyroid tumorigenesis.
Akt activation in anaplastic thyroid cancer. Correlation with PIK3CA, Ras, BRAF mutations, and proliferative activity. The level of expression and subcellular localization of activated Akt, as a downstream effector of the PI3K gene product, was analyzed in our own TMA of ATC. Total activated Akt was determined using a non–isoform-specific antibody against Akt phosphorylated at Ser473. Phospho-Akt staining was considered indicative of Akt activation and, thus, the case recorded as positive, when at least 5% of the cells expressed the phosphorylated form of the protein. Although all of the tissue cores representative of normal thyroid or nodular hyperplasia that were included in the TMA (10 cores from six cases) disclosed focal immunoreactivity, the tumors exhibited a diffuse pattern of staining. The presence of immunoactive Akt in normal thyroid tissue, besides providing an internal control for staining distribution and intensity, may reflect the response of thyroid follicular cells to endogenous physiologic stimuli by thyrotropin and insulin growth factor (22). Activation of Akt was detected in 38 of 41 ATC (93%). High levels of phospho-Akt were identified in 10 ATC (26%), moderate levels in 19 ATC (50%), and low levels in nine ATC (24%). Of note, in 36 ATC cytoplasmic localization of phospho-Akt was accompanied by different percentages of nuclear reactivity. In two ATC, which were known to originate in a previous tall cell and a follicular variant of papillary carcinoma, the expression of activated Akt was limited to the cytoplasm (see Fig. 3D and P). Figure 3 illustrates phospho-Akt immunoreactivity in several ATC, mutated or not at PIK3CA, as well as its expression in concurrent better-differentiated areas within some ATC and three normal thyroids. The correlation between the level of phospho-Akt expression and the mutational status of PIK3CA, Ras, and BRAF genes is summarized in Table 3. Ten of 16 ATC mutated at PIK3CA were present in the TMA and nine (90%) showed activation of Akt. Two tumors (22%) displayed high levels of phospho-Akt, four tumors (45%) moderate/distinct levels, and three tumors (33%) low levels. The only ATC mutated at PIK3CA scored negative harbored also a Ras mutation. Seventy-four percent of the ATC featuring immunoactive Akt (26 of 35) were found to be wild type at PIK3CA. Putative alternative molecular mechanisms that may explain Akt activation in those cases are PTEN down-regulation or Ras activation. Indeed, our data indicate that Ras mutations could account for 23% of the ATC that came out wild type at PIK3CA and were Akt positive (6 of 26). Overall, 63% of the ATC showing phospho-Akt immunoreactivity (22 of 35) were mutated either at PIK3CA alone or in association with Ras or BRAF (nine cases), Ras (six cases), or BRAF (seven cases). No evidence of Akt activation was detected in two ATC wild type at PIK3CA.
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5% and 
25%; ++, >25% and < 60%; +++, 60%). One-way ANOVA, with a Bonferroni correction for multiple comparisons across groups, showed a significant association (P < 0.0001) between the mean phospho-Akt score values and all three categories of Ki67/Mib1 immunoreactivity. Likewise, linear regression analysis of phospho-Akt and Ki67/Mib1 values, in all of the 41 ATC included in the TMA, disclosed a highly significant correlation (r = 0.894) between the expression of both proteins (P < 0.0001; SPSS software version 11.0). When considering only the 10 ATC mutated at PIK3CA, which were present in the TMA, no statistical effect was observed beyond the correlation already shown between Akt activation and proliferative activity on 41 ATC. All of the PIK3CA-mutated ATC showing high levels of phospho-Akt (two cases) segregated into the +++ category of Ki67/Mib1 and all of the PIK3CA-mutated ATC featuring low levels of phospho-Akt (three cases) segregated into the + Ki67/Mib1 group. When the four PIK3CA-mutated ATC displaying moderate levels of phospho-Akt were divided according to their proliferation rates, two cases fall within the ++ group and two within the + group. The only PIK3CA-mutated ATC scored as phospho-Akt negative revealed a low Ki67/Mib1 index (+). |
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Our data suggest that PIK3CA mutations may contribute to thyroid cell neoplastic progression. Although further studies are mandatory, the fact that in our series the prevalence of PIK3CA missense mutations was higher in ATC than in well-differentiated thyroid carcinomas seems to support that hypothesis. Moreover, in 18 of 20 ATC cases in which a better differentiated carcinoma component was analyzed, PIK3CA mutations, when present, were restricted to the undifferentiated area. On the other hand, the finding of a E545Q mutation in a highly infiltrative WDPC and the corresponding lymph node metastasis and the finding of a H1047R mutation in a minimally invasive WDFC that gave rise to distant metastases seem also to indicate that PI3K activation plays some role in the spread of thyroid tumor cells both, locally and to distant sites. Accordingly, it has been recently shown that activation of Akt is more pronounced in the invasive regions of thyroid carcinomas and the corresponding lymph node or distant metastases (10). Further support for a putative role of PIK3CA mutations in the regulation of thyroid cancer cell invasiveness is provided by the correlation observed between PIK3CA mutations or PTEN loss and lymph node metastasis on breast cancer patients (16, 24). These findings suggest that, in some cases, increased PIP3 production and activation of the PI3K/AKT pathway may enhance invasion of cancer cells. Indeed, PIP3 is involved in the regulation of cell motility (25). The hypothesis that gain-of-function mutations at PIK3CA (e.g., H1047R) might contribute to the invasive and metastatic phenotypes in naturally occurring tumors is also in agreement with the common occurrence of PIK3CA mutations during the stage of colon tumorigenesis when invasion is initiated (11). Because it is known that PTEN, which negatively regulates PI3K signaling, is down-regulated in 37% of the well-differentiated thyroid carcinomas and down-regulated or lost in most ATC (3, 7, 8) and constitutively active Ras, which positively regulates PI3K signaling (26, 27), is found in 50% of the ATC (20), the activation of PI3K in those tumors might confer and additional advantage for thyroid cancer cells to spread. A phenomenon that could be also mimicked by mutational activation of PIK3CA.
As a readout of PI3K functional activation, we tested Akt phosphorylation in ATC. Despite most of the PIK3CA-mutated ATC were positive for phospho-Akt, our findings show that Akt is generally activated in ATC (93%), regardless of the presence of PIK3CA mutations. In addition to oncogenic activation of PI3K, a wide variety of molecular mechanisms may lead to Akt activation on ATC (e.g., Ras activation or PTEN inactivation reported both in >50% of the cases; refs. 3–8, 20). Although unfortunately in six of the PIK3CA-mutated ATC could not be assessed Akt activation, our results seem to indicate that multiple signaling pathways (PI3K and Ras), in a separate (Ras in six tumors and PIK3CA in five tumors) and coordinate (Ras plus PIK3CA in four tumors) way, modulate Akt activation. Overall, Ras and/or PIK3CA mutations were observed in 43% of the ATC featuring phospho-Akt immunoreactivity. Of note, 95% of the ATC disclosing activated cytosolic Akt (36 of 38), revealed also different percentages of nuclear reactivity. These findings are in agreement with the fact that the majority of the downstream targets phosphorylated by Akt are located in the cytosol, and some seem to be primarily phosphorylated at the nucleus (28). Indeed, compartmentalization of activated Akt may be important in determining its cellular effects. Vasko et al. have recently shown that subcellular localization of activated Akt differs between follicular and papillary thyroid cancers. Whereas in follicular cancers phospho-Akt localizes primarily to the nucleus, in papillary cancers, it localizes to the cytoplasm, except for the invasive and metastatic regions where it is expressed in both compartments (10). It could be hypothesized that phosphorylated Akt is shuttled into the nucleus related to the cell cycle and/or as response to cell division and growth. Although further studies are necessary to determine if differential subcellular compartmentalization of Akt might play some as yet undefined role in delivering mitogenic and survival signals, our results indicate that activation of Akt in ATC is significantly associated with enhanced cellular proliferation. Intriguingly, one of the Akt phosphorylation targets known to play a role in cell cycle control, the cyclin-dependent kinase inhibitor p27, was previously reported to be down-regulated and/or mislocalized to the cytoplasm in a subset of the ATC included in this work (29). Accordingly, it has been recently shown that p27 is a key target of the growth-regulatory activity and cellular proliferation signals exerted by the PTEN/PI3K/AKT pathway in thyroid cancer cells (30).
The PTEN/PI3K/AKT pathway is known to have a close crosstalk with the Ras/RAF/mitogen-activated protein kinase kinase kinase signaling cascade (26, 27). Many of our PIK3CA-mutated ATC showed coexisting Ras or BRAF alterations. The presence of double PIK3CA/Ras mutants might indicate that certain PIK3CA mutations (E522K, G1009E, T1031I, and K1041N) are less potent activators of the PI3K pathway. Whatever the explanation for coexisting mutations, the putative cooperation of PI3K signaling and RET/PTC, Ras, or BRAF signaling might have important implications in the behavior of a subset of thyroid carcinomas. Moreover, the frequent coexistence of p53 inactivation and PI3K activation in some ATC might render the cancer cells highly resistant to apoptosis and prone to escape from any restriction of growth. The latter association may also contribute to the high genomic instability of ATC, to the clinical presentation of ATC as a rapidly enlarging neck mass as well as to the chemotherapy and radiotherapy resistance of ATC.
In conclusion, oncogenic activation of PIK3CA in thyroid cancer is primarily associated with ATC, which represents the least differentiated histotype and the end point of tumor progression, in the multistage genetic model of thyroid follicular cell tumorigenesis. The study raises the possibility that highly specific small-molecule inhibitors targeting PI3K or downstream kinases, such as AKT, might have significant therapeutic activity and could be developed into effective anticancer drugs for patients with ATC. Kang et al. have already shown that the inhibitor of TOR, rapamycin, strongly interferes with the transformation of chicken embryo fibroblast induced by the H1047R mutant (19). Taken together, our data with previously reported alterations in upstream (PTEN, Ras, and RET/PTC; refs. 3–8, 20) and downstream (Akt and p27; refs. 8, 9, 29, 30) members of the pathway, it would seem that a majority of thyroid cancers have activation of the PTEN/PI3K/AKT pathway, making this pathway extremely attractive for gene-targeted therapies. Finally, it would be important to remark that a significant fraction of human cancers share with thyroid cancer the lost of PIP3 homeostasis, due to PTEN inactivation and PIK3CA activation. Because alterations of these two genes tend to be mutually exclusive, it is likely that a big proportion of the most common human neoplasms, such as breast, ovarian, endometrial, colon, prostate cancer, and glioblastomas, have selected for the activation of the PTEN/PI3K/AKT pathway in their pathogenesis, and may therefore benefit from the same small molecule inhibitors.
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Acknowledgments |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
We are grateful to Professor Sobrinho's laboratory for providing DNA from the cell lines K1, K2, K5, and XTC-1. We also thank Elena Couso Folgueiras for her outstanding technical assistance in the immunohistochemical analysis of phospho-Akt and the assistant graduated fellow Severina Moreira for her contribution in the sequencing analysis of some tumors.
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Footnotes |
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Received 12/ 6/04. Revised 8/15/05. Accepted 9/ 7/05.
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 P. Hou, D. Liu, Y. Shan, S. Hu, K. Studeman, S. Condouris, Y. Wang, A. Trink, A. K. El-Naggar, G. Tallini, et al. Genetic Alterations and Their Relationship in the Phosphatidylinositol 3-Kinase/Akt Pathway in Thyroid Cancer Clin. Cancer Res., February 15, 2007; 13(4): 1161 - 1170. [Abstract] [Full Text] [PDF]
|
|
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N. Yeager, A. Klein-Szanto, S. Kimura, and A. Di Cristofano Pten Loss in the Mouse Thyroid Causes Goiter and Follicular Adenomas: Insights into Thyroid Function and Cowden Disease Pathogenesis Cancer Res., February 1, 2007; 67(3): 959 - 966. [Abstract] [Full Text] [PDF]
|
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 |
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 G. L. Gallia, V. Rand, I-M. Siu, C. G. Eberhart, C. D. James, S. K.N. Marie, S. M. Oba-Shinjo, C. G. Carlotti, O. L. Caballero, A. J.G. Simpson, et al. PIK3CA Gene Mutations in Pediatric and Adult Glioblastoma Multiforme Mol. Cancer Res., October 1, 2006; 4(10): 709 - 714. [Abstract] [Full Text] [PDF]
|
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|
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|
|
C. Mesa Jr., M. Mirza, N. Mitsutake, M. Sartor, M. Medvedovic, C. Tomlinson, J. A Knauf, G. F. Weber, and J. A. Fagin Conditional Activation of RET/PTC3 and BRAFV600E in Thyroid Cells Is Associated with Gene Expression Profiles that Predict a Preferential Role of BRAF in Extracellular Matrix Remodeling. Cancer Res., July 1, 2006; 66(13): 6521 - 6529. [Abstract] [Full Text] [PDF]
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|
 P. R. Cutillas, A. Khwaja, M. Graupera, W. Pearce, S. Gharbi, M. Waterfield, and B. Vanhaesebroeck Ultrasensitive and absolute quantification of the phosphoinositide 3-kinase/Akt signal transduction pathway by mass spectrometry PNAS, June 13, 2006; 103(24): 8959 - 8964. [Abstract] [Full Text] [PDF]
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