Biomedical subjects

Giovanni Tallini

Publications and source records attributed to Giovanni Tallini.

At least 19 recordsLinked to original sources

PubMed2026

Genome-Wide Single-Nucleotide Polymorphism (SNP)-based Profiling of Loss of Heterozygosity Reveals Distinct Molecular Subgroup-Specific Patterns in Gastrointestinal Stromal Tumors (GIST).

PURPOSE: Gastrointestinal stromal tumors (GIST) are molecularly heterogeneous neoplasms defined by mutually exclusive driver alterations (KIT, PDGFRA, SDH, BRAF, RAS, and NF1). However, driver mutations alone do not fully explain their biological and clinical variability. Chromosomal imbalances and loss of heterozygosity (LOH) may represent an additional layer of tumor characterization. We developed a single-nucleotide polymorphism (SNP)-based next-generation sequencing panel enabling genome-wide LOH assessment from formalin-fixed paraffin-embedded tissue. MATERIALS AND METHODS: Forty-nine GIST cases molecularly classified using targeted next-generation sequencing (KIT n = 19, PDGFRA n = 9, SDH-deficient n = 8, NF1 n = 7, quadruple wild-type n = 6) were analyzed. LOH was inferred from variant allele frequency patterns across 1826 genome-wide SNPs. RESULTS: Chromosome 14 was the most commonly affected (63%), followed by chromosomes 22 (45%), 15 (41%), 21 (27%), and 13 (20%). Loss of chromosome arm 1p occurred in 43% of tumors. Distinct subgroup-specific patterns emerged: KIT-mutant GIST exhibited the highest degree of genomic instability, whereas both SDH-deficient tumors and PDGFRA-mutant GIST displayed minimal chromosomal instability. NF1-mutant tumors showed recurrent single-arm chromosome 17 LOH. Quadruple wild-type GISTs were heterogeneous, including 1 case with extensive chromosomal instability. CONCLUSIONS: Genome-wide SNP-based LOH profiling reveals distinct, subgroup-specific patterns of chromosomal imbalance in GIST and may serve as a feasible complementary approach to driver mutation analysis for refined molecular characterization and potential future clinical utility.

Humans↗

PubMed2006

Monitoring HCV RNA viral load by locked nucleic acid molecular beacons real time PCR.

Locked nucleic acids (LNA) based real time PCR was used in particular situations where there are difficulties in primer design due to sequence complexity. In this study a new real time RT-PCR assay was developed using LNA modified primers and LNA molecular beacon probes to monitor hepatitis C virus (HCV) viral load in plasma and serum samples. The technique did not suffer from an heterogeneity of the HCV genome and, in addition, an internal RNA control was amplified in the same reaction tube with different short primers and beacon probe. Due to the short consensus LNA primers length, the PCR efficiency was close to 100% with no formation of hairpin loop structures. In summary a new LNA molecular beacon based real time RT-PCR assay was used successfully to measure quantitatively the total level of HCV RNA in both experimental and clinical specimens. The high sensitivity (50 IU/ml), the wide range of genotype detection, increased specificity and robustness obtained with this test are particularly useful for screening large number of specimens and measuring viral loads to monitor the progress of the disease.

5' Untranslated Regions↗

PubMed2006

Association of aberrant methylation of tumor suppressor genes with tumor aggressiveness and BRAF mutation in papillary thyroid cancer.

The role of aberrant tumor suppressor gene methylation in the aggressiveness of papillary thyroid cancer (PTC) has not been documented. By showing promoter methylation-induced gene silencing in PTC-derived cell lines, we first demonstrated the functional consequence of methylation of several recently identified tumor suppressor genes, including those for tissue inhibitor of metalloproteinase-3 (TIMP3), SLC5A8, death-associated protein kinase (DAPK) and retinoic acid receptor beta2 (RARbeta2). We then investigated the role of methylation of these genes in the aggressiveness of PTC by examining the relationship of their aberrant methylation to clinicopathological characteristics and BRAF mutation in 231 primary PTC tumors. Methylation of TIMP3, SLC5A8 and DAPK was significantly associated with several aggressive features of PTC, including extrathyroidal invasion, lymph node metastasis, multifocality and advanced tumor stages. Methylation of these genes was also significantly associated with BRAF mutation in PTC, either individually or collectively in various combinations. Methylation of these genes, either individually or collectively, occurred more frequently in more aggressive classical and tall-cell PTC subtypes than in less aggressive follicular-variant PTC, with the latter known to infrequently harbor BRAF mutation. Several other tumor suppressor genes investigated were not methylated. These results suggest that aberrant methylation and hence silencing of TIMP3, SLC5A8, DAPK and RARbeta2, in association with BRAF mutation, may be an important step in PTC tumorigenesis and progression.

Apoptosis Regulatory Proteins↗

PubMed2006

Follicular variant of papillary thyroid carcinoma: a clinicopathologic study of a problematic entity.

BACKGROUND: There is continuous debate regarding the optimal classification, prognosis, and treatment of the follicular variant of papillary thyroid carcinoma (FVPTC). The objective of this study was to assess the behavior of FVPTC, especially its encapsulated form, and shed more light on its true position in the classification scheme of well differentiated thyroid carcinoma. METHODS: All patients with FVPTC, follicular thyroid adenoma (FTA), and follicular thyroid carcinoma (FTC) who were diagnosed between 1980 and 1995 were reviewed and reclassified according to the currently accepted definition of FVPTC. The tumors were separated into encapsulated and nonencapsulated (infiltrative/diffuse) types. Encapsulated tumors were subdivided further into tumors with or without capsular/vascular invasion. These different subtypes of FVPTC were correlated with outcome and with other clinicopathologic parameters. RESULTS: After review by 4 pathologists, 78 patients were included in the study. Sixty-one of 78 patients (78%) had encapsulated tumors (18 invasive, 43 noninvasive), and 17 patients had nonencapsulated tumors (infiltrative/diffuse). The gender distribution, age at presentation, and tumor size did not differ between patients with encapsulated and nonencapsulated FVPTC. Patients who had encapsulated FVPTC had a significantly lower rate of marked intratumor fibrosis (18%), extrathyroid extension (5%), and positive margins (2%) compared with patients who had nonencapsulated tumors (88%, 65%, and 50% respectively; P < .0001). Regional lymph node metastases were present in 14 of 78 patients (18%), and no patients had distant metastases. The lymph node metastatic rate was significantly higher in patients who had nonencapsulated tumors (11 of 17 patients; 65%) compared with patients who had encapsulated neoplasms (3 of 61 patients; 5%; P < .0001). In addition, lymph node metastases were not detected in any noninvasive, encapsulated FVPTCs. With a median follow-up of 10.8 years, only 1 patient developed a recurrence, which occurred in an encapsulated FVPTC that had numerous invasive foci. None of the patients with noninvasive, encapsulated FVPTCs developed recurrences, including 31 patients who underwent lobectomy alone, with a median follow-up of 11.1 years. CONCLUSIONS: FVPTC appeared to be a heterogeneous disease composed of 2 distinct groups: an infiltrative/diffuse (nonencapsulated) subvariant, which resembles classic papillary carcinoma in its metastatic lymph node pattern and invasive growth, and an encapsulated form, which behaves more like FTA/FTC. Patients who had noninvasive, encapsulated FVPTCs did not develop lymph node metastases or recurrences and could be treated by lobectomy alone. If the current findings are confirmed, then strong consideration should be given to reclassifying encapsulated FVPTC as an entity that is close to the FTA/FTC class of tumors.

Adenocarcinoma, Follicular↗

PubMed2006

Defective oxidative phosphorylation in thyroid oncocytic carcinoma is associated with pathogenic mitochondrial DNA mutations affecting complexes I and III.

Oncocytic tumors are characterized by cells with an aberrant accumulation of mitochondria. To assess mitochondrial function in neoplastic oncocytic cells, we studied the thyroid oncocytic cell line XTC.UC1 and compared it with other thyroid non-oncocytic cell lines. Only XTC.UC1 cells were unable to survive in galactose, a condition forcing cells to rely solely on mitochondria for energy production. The rate of respiration and mitochondrial ATP synthesis driven by complex I substrates was severely reduced in XTC.UC1 cells. Furthermore, the enzymatic activity of complexes I and III was dramatically decreased in these cells compared with controls, in conjunction with a strongly enhanced production of reactive oxygen species. Osteosarcoma-derived transmitochondrial cell hybrids (cybrids) carrying XTC.UC1 mitochondrial DNA (mtDNA) were generated to discriminate whether the energetic failure depended on mitochondrial or nuclear DNA mutations. In galactose medium, XTC.UC1 cybrid clones showed reduced viability and ATP content, similarly to the parental XTC.UC1, clearly pointing to the existence of mtDNA alterations. Sequencing of XTC.UC1 mtDNA identified a frameshift mutation in ND1 and a nonconservative substitution in cytochrome b, two mutations with a clear pathogenic potential. In conclusion, this is the first demonstration that mitochondrial dysfunction of XTC.UC1 is due to a combined complex I/III defect associated with mtDNA mutations, as proven by the transfer of the defective energetic phenotype with the mitochondrial genome into the cybrids.

Adenoma, Oxyphilic↗

PubMed2006

RET/papillary thyroid cancer rearrangement in nonneoplastic thyrocytes: follicular cells of Hashimoto's thyroiditis share low-level recombination events with a subset of papillary carcinoma.

CONTEXT: RET/papillary thyroid cancer (PTC) is a marker for papillary thyroid carcinoma, but its specificity has been questioned because of the disputed identification of RET/PTC in Hashimoto's thyroiditis (HT), oncocytic tumors, and other thyroid lesions. OBJECTIVE: The objective of this study was to determine 1) whether RET/PTC occurs in nonneoplastic follicular cells of HT, and 2) its recombination rate in thyroid tumors. DESIGN/PATIENTS: Forty-three samples from 31 cases of HT were examined using interphase fluorescence in situ hybridization (FISH) with RET probes spanning the breakpoint region; real-time RT-PCR to quantify RET/PTC1, RET/PTC3, and c-RET transcripts; and RT-PCR after laser capture microdissection to enrich samples for follicular cells. The results were compared with those similarly obtained in 34 papillary carcinomas, eight thyroid oncocytic tumors, and 21 normal thyroids. RESULTS: Normal samples showed no RET rearrangement. Sixty-eight percent (15 of 22) of HT were positive by FISH; in all thyroiditis, signals were localized to rare nonneoplastic follicular cells; low-level RET/PTC was identified in 17% (five of 29) of thyroiditis cases by real-time RT-PCR and in an additional six of 11 real-time negative cases after increasing sensitivity with laser capture microdissection. Low RET/PTC1 levels were detected in 26% (nine of 34) of papillary carcinomas with an expression pattern and proportion of FISH-positive cells similar to those of the thyroiditis. Forty-seven percent (16 of 34) of papillary carcinomas and one oncocytic carcinoma expressed high RET/PTC1 mRNA levels. CONCLUSIONS: Low-level RET/PTC recombination occurs in nonneoplastic follicular cells in HT and in a subset of papillary thyroid carcinomas. RET/PTC expression variability should be taken into account for the molecular diagnosis of thyroid lesions. Overlapping molecular mechanisms may govern early stages of tumor development and inflammation in the thyroid.

Carcinoma, Papillary↗

PubMed2006

Clinical experience with gefitinib: an update.

Gefitinib is an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) that blocks signal transduction pathways involved in cell proliferation. This drug demonstrated impressive and durable responses in patients with heavily pretreated non-small cell lung cancer (NSCLC). In two large phase II trials, responses were observed in 9-19% of unselected patients, along with symptom improvement and benefit in quality of life. Biological mechanisms underlying TKI sensitivity have recently been discovered. There is evidence that specific EGFR gene mutations and/or amplification confer a particularly sensitive phenotype, especially in individuals with tumors demonstrating activation of the anti-apoptotic protein Akt. However, in all so far conducted clinical trials, no patient selection has been made, providing a logical explanation for the negative results observed in large phase III studies. In the present review, we will summarize the results observed in clinical trials with gefitinib. We will present results obtained in NSCLC and in other solid tumor, focusing on biological and clinical markers predicting drug sensitivity.

Clinical Trials as Topic↗

PubMed2005

Tumor-specific changes in mtDNA content in human cancer.

Mitochondrial DNA (mtDNA) alterations are associated with various cancer types, suggesting that the mitochondrial genome may be a critical contributing factor in carcinogenesis. mtDNA alterations have been suggested as a potentially sensitive and specific biomarker for several cancer types. We examined mtDNA content in 25 pairs of normal and tumor breast tissue samples, 37 papillary thyroid carcinoma (PTC), 21 benign thyroid neoplasms and in 20 paired normal and PTC samples. Our results showed that mtDNA content was reduced in 80% of the breast tumors relative to their corresponding normal. mtDNA was increased in papillary thyroid carcinomas, however, when compared to the corresponding normal DNA taken from the same individual. Also, mtDNA content was increased in none-paired PTC samples compared to the normal controls. Our findings indicate that changes in mtDNA content during carcinogenesis may be regulated in a tumor specific manner. Additionally, changes in mtDNA levels did not correlate with tumor grade and metastasis, suggesting that these alterations may occur in the early stages of tumorigenesis. Our findings suggest that mtDNA content can be used as a molecular diagnostic tool to help identify genetic abnormalities in human tumors.

Breast Neoplasms↗

PubMed2005

BRAF mutation predicts a poorer clinical prognosis for papillary thyroid cancer.

CONTEXT: Use of BRAF mutation in papillary thyroid cancer (PTC) has the potential to improve risk stratification of this cancer. OBJECTIVE: The objective of the study was to investigate the prognostic value of BRAF mutation in patients with PTC. DESIGN, SETTING, AND SUBJECTS: In a multicenter study of 219 PTC patients, data on their clinicopathological characteristics and clinical courses between 1990 and 2004 were retrospectively collected, and their tumor BRAF mutation status was determined. Associations of BRAF mutation with initial tumor characteristics and subsequent recurrence were analyzed. MAIN OUTCOME MEASURE: Relationships between the BRAF mutation status and clinicopathological outcomes, including recurrence, were measured. RESULTS: We found a significant association between BRAF mutation and extrathyroidal invasion (P < 0.001), lymph node metastasis (P < 0.001), and advanced tumor stage III/IV (P = 0.007) at initial surgery. This association remained significant on multivariate analysis, adjusting for conventional clinicopathological predictors of recurrence excluding the histological PTC subtype, but was lost when the tumor subtype was included in the model. BRAF mutation was also significantly associated with tumor recurrence, 25 vs. 9% with and without mutation, respectively (P = 0.004), during a median of 15 (interquartile range, 3-29) months of follow-up. This association remained significant on multivariate analysis adjusting for conventional clinicopathological predictors of recurrence, even including the PTC subtype (odds ratio, 4.0; 95% confidence interval, 1.1-14.1; P = 0.03). BRAF mutation was even an independent predictor of recurrence in patients with stage I/II disease, 22 vs. 5% with and without BRAF mutation, respectively (P = 0.002). BRAF mutation was also more frequently associated with absence of tumor I-131 avidity and treatment failure of recurrent disease. CONCLUSIONS: In patients with PTC, BRAF mutation is associated with poorer clinicopathological outcomes and independently predicts recurrence. Therefore, BRAF mutation may be a useful molecular marker to assist in risk stratification for patients with PTC.

Adult↗

PubMed2005

HMGA proteins in malignant peripheral nerve sheath tumor and synovial sarcoma: preferential expression of HMGA2 in malignant peripheral nerve sheath tumor.

Histological separation of synovial sarcomas from malignant peripheral nerve sheath tumors can be difficult and available immunohistochemical markers sometimes give rise to overlapping staining patterns. Additional markers are needed to better define the two entities in the routine surgical pathology practice. To this end, we explored diagnostic applications of HMGA (HMGA1 and HMGA2) protein immunohistochemistry in comparable groups of synovial sarcoma and malignant peripheral nerve sheath tumors. The histological diagnosis of these cases was confirmed by the presence or absence of synovial sarcoma specific SYT-SSX fusion transcript analyzed by real-time reverse transcription polymerase chain reaction. In all, 13 malignant peripheral nerve sheath tumors and 15 synovial sarcomas were included in this study. Immunohistochemically, most malignant peripheral nerve sheath tumors expressed both HMGA1 and HMGA2 protein (12/13 and 12/13 cases, respectively) with moderate to strong nuclear staining patterns. Most cases of synovial sarcomas demonstrated variable expression of HMGA1. However, significant immunoreactivity for HMGA2 was present in the glandular component of a biphasic tumor (1/1) and rarely detected in monophasic synovial sarcomas (1/14). In summary, expression of HMGA2 is a feature of MPNST but not of synovial sarcoma and immunohistochemical staining of HMGA2 may be a useful marker to separate malignant peripheral nerve sheath tumor from synovial sarcoma.

Adult↗

PubMed2005

Assessment of RET/PTC oncogene activation in thyroid nodules utilizing laser microdissection followed by nested RT-PCR.

Single palpable nodules of the thyroid gland are common in clinical practice; the majority of such lesions are benign. However, noninvasive thyroid nodules that exhibit borderline morphological signs of papillary cancer represent a diagnostic challenge. Rearrangements of the RET oncogene have been proposed as a marker for papillary thyroid cancer. In this chapter, methods for the analysis of the RET oncogene in laser microdissected papillary thyroid cancer tissue are described.

Biomarkers, Tumor↗

PubMed2004

Menstrual and reproductive factors and risk of non-Hodgkin's lymphoma among Connecticut women.

Several recent studies have suggested a potential role of menstrual and reproductive factors in the risk of non-Hodgkin's lymphoma. To further examine the relation, the authors analyzed data from a population-based case-control study of non-Hodgkin's lymphoma in Connecticut women between 1996 and 2000. A total of 601 histologically confirmed cases and 717 randomly selected population-based controls were included in this study. An in-person interview was conducted using a standardized and structured questionnaire to collect information on menstrual and reproductive factors and potential confounding factors. Compared with nulliparous women, women who had four or more pregnancies during their lifetime were found to have a significantly reduced risk of non-Hodgkin's lymphoma (odds ratio (OR) = 0.6, 95% confidence interval (CI): 0.4, 0.9). Risk appeared to decrease with increasing number of pregnancies (p(trend) = 0.03). The authors also observed an increased risk of non-Hodgkin's lymphoma overall (OR = 1.5, 95% CI: 1.0, 2.2) and of diffuse non-Hodgkin's lymphoma (OR = 1.7, 95% CI: 1.1, 2.7) for women who started their first menstrual period at age 15 or more years compared with those who started their first menstrual period before age 12 years. These findings support a reduced risk of non-Hodgkin's lymphoma associated with multiple pregnancies and an increased risk of non-Hodgkin's lymphoma associated with later age at menarche.

Adolescent↗

PubMed2004

Blood transfusion and risk of non-Hodgkin's lymphoma in Connecticut women.

The incidence and mortality rates of non-Hodgkin's lymphoma have been increasing worldwide. Allogeneic blood transfusion has been suggested as a risk factor for non-Hodgkin's lymphoma, but the results from epidemiologic studies have been inconsistent. Data from a population-based case-control study of Connecticut women were analyzed to evaluate this relation. A total of 601 histologically confirmed, non-Hodgkin's lymphoma incident cases identified between 1996 and 2000 and 717 randomly selected controls were included in this study. Allogeneic blood transfusion was not associated with the increased risk of non-Hodgkin's lymphoma overall (odds ratio = 1.0, 95% confidence interval: 0.7, 1.3) or by subtype of the disease. The risk also did not vary by number of allogeneic blood transfusions, age at first transfusion, or time since first transfusion. When the reason for blood transfusion was considered, an increased risk of non-Hodgkin's lymphoma was found only for allogeneic blood transfusion for reason of anemia. In summary, the authors' findings do not support the hypothesis that allogeneic blood transfusion increases the risk of non-Hodgkin's lymphoma.

Adult↗

PubMed2004

Three-dimensional reconstruction of vessel distribution in benign and malignant lesions of thyroid.

In order to better understand the spatial distribution of thyroid vessels, a series of benign and malignant thyroid lesions were studied with three-dimensional (3D) histological stereomicroscopic reconstruction. Cases consisted of normal autoptic thyroids (n=6), colloid goitres (n=6), Basedow's disease (n=2), follicular adenoma (FA) (n=4) one of which with Hurthle cells (HC), minimally invasive, well-differentiated follicular carcinoma (FTC) (n=1), well-differentiated FTC with HC (n=1), poorly differentiated FTC (n=13) with extensive angioinvasion, papillary carcinoma (PTC) (n=8) and medullary carcinoma (MTC) (n=1). From each selected nodule, parallel sections were obtained for 3D reconstruction and for histological and immunohistochemical studies. In normal thyroid, large vessels were located at the periphery of the gland with smaller branches present within the thyroid parenchyma that encircled follicles. The same pattern of vascularisation is maintained in lesions showing a follicular architecture as colloid goitre, Basedow's disease, FA, well-differentiated FTC and the follicular variant of PTC. Neoplastic lesions, at variance with non-neoplastic lesions, contained rare anastomoses. Poorly differentiated FTC and MTC contained large intratumoural vessels surrounding avascular areas corresponding to solid neoplastic cellular sheets with necrosis. PTC were more vascularised and contained numerous vascular anastomoses. In conclusion, the present data indicate that the vascular distribution is related to the follicular, papillary or solid type of growth. Vascular anastomoses and intratumoural vessels surrounding solid avascular areas are signs of malignancy.

Adult↗

PubMed2004

Genome-wide profiling of papillary thyroid cancer identifies MUC1 as an independent prognostic marker.

Clinicopathological variables used at present for prognostication and treatment selection for papillary thyroid carcinomas (PTCs) do not uniformly predict tumor behavior, necessitating identification of novel prognostic markers. Complicating the assessment is the long natural history of PTC and our rudimentary knowledge of its genetic composition. In this study we took advantage of differences in clinical behavior of two distinct variants of PTC, the aggressive tall-cell variant (TCV) and indolent conventional PTC (cPTC), to identify molecular prognosticators of outcome using complementary genome wide analyses. Comparative genome hybridization (CGH) and cDNA microarray (17,840 genes) analyses were used to detect changes in DNA copy number and gene expression in pathological cPTC and TCV. The findings from CGH and cDNA microarray analyses were correlated and validated by real-time PCR and immunohistochemical analyses on a series of 100 cases of cPTC and TCV. Genes identified by this approach were evaluated as prognostic markers in cPTC by immunohistochemistry on tissue arrays. CGH identified significant differences in the presence (76 versus 27%; P = 0.001) and type of DNA copy number aberrations in TCV compared with cPTC. Recurrent gains of 1p34-36, 1q21, 6p21-22, 9q34, 11q13, 17q25, 19, and 22 and losses of 2q21-31, 4, 5p14-q21, 6q11-22, 8q11-22, 9q11-32, and 13q21-31 were unique to TCV. Hierarchical clustering of gene expression profiles revealed significant overlap between TCV and cPTC, but further analysis identified 82 dysregulated genes differentially expressed among the PTC variants. Of these, MUC1 was of particular interest because amplification of 1q by CGH correlated with MUC1 amplification by real-time PCR analysis and protein overexpression by immunohistochemistry in TCV (P = 0.005). Multivariate analysis revealed a significant association between MUC1 overexpression and treatment outcome, independent of histopathological categorization (P = 0.03). Analysis of a validation series containing a matched group of aggressive and indolent cPTCs confirmed the association between MUC1 overexpression and survival (relative risk, 2.3; 95% confidence interval, 1.1-5.5; P = 0.03). Our data suggest that MUC1 dysregulation is associated with aggressive behavior of PTC and may serve as a prognostic marker and potential therapeutic target in this disease.

Carcinoma, Papillary↗

PubMed2004

Diet and nutrient intakes and risk of non-Hodgkin's lymphoma in Connecticut women.

A population-based case-control study (601 cases and 717 controls) was conducted in 1995-2001 among Connecticut women to evaluate the relation between diet and nutrient intakes and the risk of non-Hodgkin's lymphoma (NHL). When the highest quartile of intake was compared with the lowest, the authors found an increased risk of NHL associated with animal protein (odds ratio = 1.7, 95% confidence interval: 1.2, 2.4) and saturated fat (odds ratio = 1.9, 95% confidence interval: 1.1, 2.3) but a reduced risk for polyunsaturated fat (odds ratio = 0.6, 95% confidence interval: 0.4, 0.9) and no relation for vegetable protein and monounsaturated fat. An increased risk was also observed for higher intakes of retinol, eggs, and dairy products. On the other hand, a reduced risk was found for higher intakes of dietary fiber and for several fruit and vegetable items. Risk of NHL associated with diet and nutrient intakes appeared to vary based on NHL subtype. An association between dietary intake and NHL risk is biologically plausible because diets high in protein and fat may lead to altered immunocompetence, resulting in an increased risk of NHL. The antioxidant or inhibiting nitrosation reaction properties of vegetables and fruits may result in a reduced risk. Further investigation of the role of dietary intakes on the risk of NHL is warranted.

Adult↗

PubMed2004

Early occurrence of RASSF1A hypermethylation and its mutual exclusion with BRAF mutation in thyroid tumorigenesis.

Follicular epithelial cell-derived thyroid tumors are common neoplasms comprised mainly of benign thyroid adenomas, follicular thyroid cancers, and papillary thyroid cancers (PTCs). Hypermethylation of the tumor suppressor gene RASSF1A and activating mutation of BRAF gene have been reported recently in thyroid cancers. To additionally investigate the roles of these two epigenetic/genetic alterations in thyroid tumor progression, we examined their occurrences and relationship in both benign and malignant thyroid neoplasms. With real-time quantitative methylation-specific PCR, we found that 4 of 9 (44%) benign adenomas, 9 of 12 (75%) follicular thyroid cancers tumors, and 6 of 30 (20%) of PTC tumors harbored promoter methylation in > or = 25% of RASSF1A alleles. Additional quantitative analysis revealed RASSF1A methylation only in BRAF mutation-negative PTCs. A similar inverse correlation of RASSF1A methylation with BRAF mutation was seen in thyroid tumor cell lines. Our results, therefore, suggest that epigenetic inactivation of RASSF1A through aberrant methylation is an early step in thyroid tumorigenesis. Like the previously reported mutually exclusive relationship between BRAF mutation and other Ras pathway components such as RET/PTC rearrangement, a mutually exclusive relationship also exists between BRAF mutation and RASSF1A methylation in thyroid tumorigenesis.

Cell Line, Tumor↗

PubMed2004

The oncogenic activity of RET point mutants for follicular thyroid cells may account for the occurrence of papillary thyroid carcinoma in patients affected by familial medullary thyroid carcinoma.

Activating germ-line point mutations in the RET receptor are responsible for multiple endocrine neoplasia type 2-associated medullary thyroid carcinoma (MTC), whereas somatic RET rearrangements are prevalent in papillary thyroid carcinomas (PTCs). Some rare kindreds, carrying point mutations in RET, are affected by both cancer types, suggesting that, under specific circumstances, point mutations in RET can drive the generation of PTC. Here we describe a family whose siblings, affected by both PTC and MTC, carried a germ-line point mutation in the RET extracellular domain, converting cysteine 634 into serine. We tested on thyroid follicular cells the transforming activity of RET(C634S), RET(K603Q), another mutant identified in a kindred with both PTC and MTC, RET(C634R) a commonly isolated allele in MEN2A, RET(M918T) responsible for MEN2B and also identified in kindreds with both PTC and MTC, and RET/PTC1 the rearranged oncogene that characterizes bona fide PTC in patients without MTC. We show that the various RET point mutants, but not wild-type RET, scored constitutive kinase activity and exerted mitogenic effects for thyroid PC Cl 3 cells, albeit at significantly lower levels compared to RET/PTC1. The low mitogenic activity of RET point mutants paralleled their reduced kinase activity compared to RET/PTC. Furthermore, RET point mutants maintained a protein domain, the intracellular juxtamembrane domain, that exerted negative effects on the mitogenic activity. In conclusion, RET point mutants can behave as dominant oncogenes for thyroid follicular cells. Their transforming activity, however, is rather modest, providing a possible explanation for the rare association of MTC with PTC.

Adenocarcinoma, Follicular↗