Alterations of p53 and expression of WAF1/p21 in human thyroid tumors

P53 and expression of immunological markers may identify early stage thyroid tumors

Background. Besides its major role in cell proliferation, DNA repair, and apoptosis, functional p53 protein is involved in the induction of antitumor cytotoxic-T-cell activity against carcinoma cells. We aimed to investigate p53 and immune cell markers utility as diagnostic and prognostic markers of differentiated thyroid cancer (DTC). Methods. ACIS-III system was used to evaluate p53 and immune cell markers including tumor-associated macrophages (TAM); CD68 and tumor-infiltrating lymphocytes (TIL) subsets such as CD3, CD4, CD8, and CD20 in 206 thyroid carcinomas, 105 benign nodules, and 18 normal tissues. Also, TP53 was sequenced in 78 out of 164 patients with papillary thyroid carcinoma. Results. P53 expression was observed more frequently in malignant than in benign lesions (P < 0.0001) and helped discriminate follicular patterned lesions. In addition, p53 was more frequent in smaller (P = 0.0015), unique tumors (P = 0.0286), with thyroiditis (P = 0.0486) and without metastasis at diagnosis (P = 0.0201). TAM was more frequent in P53 negative tumors (P = 0.002). Infiltration of CD8+ TIL was found in 61.7% of P53 positive and 25.6% of P53 negative DTC (P < 0.001). Conclusions. We suggest that p53 and CD8+ TIL immune profile analysis might be useful in DTC.

Prognostic factors in surgical stage I endometrial carcinoma

The prognostic impact of DNA ploidy, MIB-1 and p53 was evaluated in relation to clinical and histopathological features in surgical stage I endometrial carcinoma (n = 284) and in the histopathological endometrioid subgroup (n = 257). Tumour material from 284 consecutive patients was analysed regarding image cytometric DNA ploidy and the immunohistochemical MIB-1 and p53 expression. Twenty-four tumours relapsed. In univariate analysis, histopathological subgroup (endometrioid vs. non-endometrioid), grade, DNA ploidy and p53 were highly significant prognostic factors (p < or = 0.001). MIB-1 was also significant (p = 0.039). In the endometrioid subgroup only DNA ploidy and p53 were significant (p < 0.001). In multivariate analysis of the entire material, ploidy and histopathological subgroup retained their significance (p = 0.001, p = 0.004), whereas only ploidy was significant in the endometrioid subgroup (p = 0.001). DNA ploidy was the strongest predictor of relapse-free survival and the only independent prognostic factor in the endometrioid subgroup.

Clinical significance of p53 protein expression in papillary thyroid carcinoma

BACKGROUND

Although mutations in the p53 suppressor gene in thyroid carcinoma have usually been detected in anaplastic carcinoma, P53 protein expression has been detected immunohistochemically in papillary thyroid carcinoma (PTC). In the present study, we examined the immunohistochemical expression of P53 protein in PTC to investigate the relations between its expression and the clinicopathologic features.

METHODS

The study was performed on 68 patients in whom thyroidectomy with lymph node dissection had been performed to treat PTC at Teikyo University Hospital. Expression of P53 protein was evaluated immunohistochemically in sections of paraffin-embedded tissue in 68 primary tumors and 196 lymph node metastases.

RESULTS

Overexpression of P53 protein in the primary tumor was observed in 29 cases (43%). Statistical analysis revealed significant correlation between P53 protein expression in the primary tumor and large tumor size (unpaired t-test: p < 0.01), the presence of lymph node metastasis (unpaired t-test: p < 0.05), and the mean number of lymph node metastases (unpaired t-test: p < 0.05). Although 29 (43%) of the primary tumors overexpressed P53 protein, 143 (73%) of the metastatic lymph nodes overexpressed P53 protein irrespective of whether there was P53 overexpression by the primary tumor.

CONCLUSIONS

The results of this study suggest that immunohistochemistry for P53 in the primary tumor could be useful in the clinical evaluation of patients with PTC. Moreover, P53 protein overexpression in lymph node metastasis may be useful as a treatment guide or target for lymph node recurrences.

Anaplastic thyroid cancer: molecular pathogenesis and emerging therapies

Anaplastic thyroid cancer (ATC) is a rare malignancy. While external beam radiation therapy has improved locoregional control, the median survival of approximately 4 months has not changed in more than half a century due to uncontrolled systemic metastases. The objective of this study was to review the literature in order to identify potential new strategies for treating this highly lethal cancer. PubMed searches were the principal source of articles reviewed. The molecular pathogenesis of ATC includes mutations in BRAF, RAS, catenin (cadherin-associated protein), beta 1, PIK3CA, TP53, AXIN1, PTEN, and APC genes, and chromosomal abnormalities are common. Several microarray studies have identified genes and pathways preferentially affected, and dysregulated microRNA profiles differ from differentiated thyroid cancers. Numerous proteins involving transcription factors, signaling pathways, mitosis, proliferation, cell cycle, apoptosis, adhesion, migration, epigenetics, and protein degradation are affected. A variety of agents have been successful in controlling ATC cell growth both in vitro and in nude mice xenografts. While many of these new compounds are in cancer clinical trials, there are few studies being conducted in ATC. With the recent increased knowledge of the many critical genes and proteins affected in ATC, and the extensive array of targeted therapies being developed for cancer patients, there are new opportunities to design clinical trials based upon tumor molecular profiling and preclinical studies of potentially synergistic combinatorial novel therapies.

Expression of p21cip1, p27kip1, and p16INk4a cyclin-dependent kinase inhibitors in papillary thyroid carcinoma: correlation with clinicopathological factors

In a variety of human malignancies, aberrant expression of proteins involved in the control of cell-cycle progression has been reported. In this study, p21cip1, p27kip1, and p16INk4a cyclin-dependent kinase inhibitors were analyzed to evaluate their usefulness in clinical management of papillary thyroid carcinoma (PTC). Archived material derived from 46 cases of PTC was analyzed immunohistochemically. Protein expression was ascertained on tissue microarrays, and results were correlated with clinicopathological features of the patients. Positive immunostaining was observed in 14 (30,4%) p21cip1, 26 (56,5%) p27kip1, and 14 (30,4%) p16INk4a cases. No significant correlation between p21cip1 or p27kip1 and clinical factors was found. In contrast, p16INk4a expression showed a significant correlation with initial extension of the disease. Therefore, 45.8% of patients with loco-regional extension were p16INk4a positive, whereas overexpression was only seen in 15.7% of cases with intrathyroid disease (p < 0.05). Moreover, all patients with simultaneous p16INk4a positivity and lack of p27kip1 staining (four patients) presented lymph node metastases. In contrast, only 12 (28.5%) of the remaining patients showed lymph node tumor involvement. In conclusion, p16INk4a expression suggests extrathyroid neck extension of PTC. This effect is enhanced when p27kip1 is negative. We think that their analysis by immunohistochemistry could be useful in the management of patients with PTC.

Patterns of expression of cell cycle/apoptosis genes along the spectrum of thyroid carcinoma progression

BACKGROUND

Genetic screening studies suggest that genetic changes underlie progression from well differentiated to anaplastic thyroid cancers. The aim of this study is to determine to what extent cell cycle/apoptosis regulators contribute to cancer progression.

METHODS

Tissue microarrarys (TMAs) were constructed from well-differentiated papillary thyroid carcinoma (WDPTC; n = 41), poorly differentiated thyroid carcinoma (PDTC; n = 43), and anaplastic thyroid carcinoma (ATC; n = 22). TMAs were immunostained for 7 different cell cycle/apoptosis-related genes (p53, Ki-67, bcl-2, mdm-2, cyclin D1, p21, and p27).

RESULTS

p53 (0%, 12%, 32%) and Ki-67 (5%, 49%, 82%) were expressed with increasing frequency, and bcl-2 (68%, 42%, 0%) and p21 (40%, 7%, 0%) with decreasing frequency in WDPTC to PDTC and ATC, respectively (P < .001). Interestingly, mdm-2 (54%, 5%, 0%) showed decreased expression along the progression axis (P < .001). p27 and cyclin D1 were expressed in <15% of cases, with a trend toward decreasing expression from WDPTC to PDTC to ATC.

CONCLUSIONS

These data confirm the presence of increasing genetic complexity with progressive dedifferentiation in thyroid cancer, with aberrant tumor suppressor activity and increased proliferative activity being most prevalent in ATC. The data also confirm the intermediate position of PDTC in the classification scheme of thyroid carcinomas.

Clinical significance of RET/PTC and p53 protein expression in sporadic papillary thyroid carcinoma

AIMS

Rearranged during Transfection (RET)/papillary thyroid carcinoma (PTC) and p53 are two genes involved in the pathogenesis of PTC. It has been suggested that RET/PTC expression is associated with higher rates of local extension and lymph node involvement, whereas p53 mutations are more frequent in poorly differentiated and anaplastic carcinomas. In addition, experimental studies have shown that p53 activity can modify the behaviour of PTC carrying RET/PTC. The aim of this study was to investigate the expression of both RET/PTC and p53 in order to evaluate their usefulness as prognostic factors.

METHODS AND RESULTS

Resected specimens of 61 cases of PTC were studied immunohistochemically using a polyclonal antibody to RET and a monoclonal antibody to p53 protein. RET/PTC expression was associated with extrathyroid extension of PTC, at diagnosis (P < 0.05). In contrast, no relationship between p53 immunoreactivity and clinical status was found. In addition, p53 expression was more prevalent among RET/PTC+ patients, and significantly influenced the relationship observed between RET/PTC and extrathyroid extension of the disease.

CONCLUSION

Our results suggest that immunohistochemistry for both PTC/RET and p53 could be useful in the clinical evaluation of patients with PTC.

Altered expression of cyclins and cell cycle inhibitors in papillary thyroid cancer: prognostic implications

Currently we lack biochemical or molecular markers that predict recurrence and metastases in thyroid cancer. Recent studies in a number of other human malignancies indicate that expression and/or subcellular localization of certain cell cycle regulators has prognostic utility. We have investigated the expression of cyclins D1 and E and of cyclin-dependent kinase inhibitor's p21 and p27 in papillary thyroid cancer (PTC) and correlated this with clinical/histological stage at diagnosis and with clinical outcome. PTCs were compared to normal thyroid, adenomas, and undifferentiated thyroid cancers (UTCs). Our studies indicate that PTCs and UTCs demonstrate low nuclear expression of cyclin E and p27, allowing a clear distinction between adenomas and these carcinomas (p < 0.004). A pattern of low nuclear expression of all four markers was observed in stage IV PTCs and UTCs, while stage I PTCs had low D1 and E accompanied by high p21 or p27. Expression of cytoplasmic cyclin D1 was significantly lower in stage IV PTCs and UTCs than in stage I-III PTC's (p </= 0.020), and appeared to correlate inversely with poor outcome in PTCs (p = 0.010). These studies suggest that evaluation of a panel of these markers and attention to their subcellular localization may be a useful adjunct in differentiating benign from malignant thyroid neoplasms and in predicting tumor behavior.

HDM2 overexpression and focal loss of p14/ARF expression may deregulate the p53 tumour suppressor pathway in meningeal haemangiopericytomas. Study by double immunofluorescence and laser scanning confocal microscopy

AIMS

To investigate the p53 pathway in meningeal haemangiopericytomas (MHPCs), p14/ARF, p53 protein expression and two wild-type (wt) p53-induced proteins (HDM2 and p21/WAF1) were studied in 18 MHPCs, 11 primary, four of them recurrent on one, one, two and four occasions.

METHODS

Immunohistochemical detection of p14/ARF, p53, p21/WAF1, HDM2 and Ki67 proliferative index (PI) protein expression.

RESULTS

Ki67 index was > 5% in eight out 18 cases (44.4%). The PI in recurrent cases increased with neoplastic progression. Simultaneous p53 and wt p53 transactivated gene (p21/WAF, HDM2) expression occurred in all cases. This argues against p53 mutation. HDM2 overexpression was observed in 10 cases (55.5%). Double-immunofluorescence staining and laser scanning confocal microscopy (LSCM) displayed HDM2 and p53 colocalization. This strongly suggests that HDM2 binds and inactivates p53 that could be pathogenic for MHPCs, by a different mechanism than point mutation. p14/ARF expression > 5% was observed in 12 cases (66.6%). A normal (diffuse) pattern of expression was seen in 13 cases (72.2%). Focal loss of expression was observed in five patients (27.7%): three primary cases and two recurrences. Therefore, p14/ARF down-regulation may also contribute to the development of MHPC.

CONCLUSION

HDM2 overexpression, sometimes combined with focal loss of p14/ARF expression, may play a pathogenic role in MHPCs.

Patterns of Cyclin E, Retinoblastoma Protein, and p21Cip1/WAF1 Immunostaining in the Oncogenesis of Papillary Thyroid Carcinoma

Purpose: Uncontrolled cell proliferation, a hallmark of cancer, may result from an increased expression of cell cycle up-regulators, and/or from a reduced expression of cell cycle down-regulators. In the present study, we analyzed, by immunohistochemistry, the expression of a panel of three proteins: cyclin E and two cell cycle inhibitors, p21Cip1/WAF1 and retinoblastoma protein (pRb) product, in different stages of papillary thyroid carcinomas (PTC).

Experimental Design: We investigated immunostaining patterns of the proteins in question in 51 resected PTC in pathologic stages, ranging from pT1a to pT4, taking into consideration their relation to clinicohistopathologic factors.

Results: We observed a significant, progressive loss of expression of p21Cip1/WAF1 with advancing tumor grade. The differences reached values of significance between pT1a [papillary thyroid microcarcinomas (PMC)] and pT2 and between PMC and pT4 stages of PTC. pRb presented a similar immunostaining pattern to that of p21Cip1/WAF1 and the differences reached values of significance between pT1a and pT2, and between PMC and pT4 stages of PTC. The results of cyclin E immunostaining corresponded to our recently published result, and a negative correlation was observed between the immunostaining index of cyclin E and pRb.

Conclusions: The results of the present study suggest that cyclin E expression and suppression of pRb and p21Cip1/WAF1 may be characteristic patterns of immunostaining for PTC with a tendency to early metastasizing. If our results are confirmed in a larger study, the diagnostic panel, constructed of the antibodies against these proteins, may become a valuable tool in predicting the metastatic potential in PTC.

Molecular pathogenesis of thyroid cancer

A number of molecular abnormalities have been described in association with the progression from normal thyroid tissue to benign adenomas to well-differentiated and finally anaplastic epithelial thyroid cancer. These include upregulation of proliferative factors, such as growth hormones and oncogenes, downregulation of apoptotic and cell-cycle inhibitory factors, such as tumor suppressors, disruption of normal cell-to-cell interactions, and cellular immortalization. The progression model for thyroid carcinoma has not been proven, but evidence suggests that an evolutionary molecular process is involved, especially in the development of follicular thyroid cancers for which there are distinct intermediate phenotypes. We present a comprehensive evaluation of factors involved in thyroid tumorigenesis and attempt to describe preliminary attributes of a progression model. The organization of this model should also provide a template for the incorporation of new information as it is derived from large-scale genomic studies.

Is atypical follicular adenoma of the thyroid a preinvasive malignancy?

Among the follicular neoplasms of the thyroid, the definition and nature of atypical adenoma have been confusing. Despite the original speculation about the biologic behavior of preinvasive malignancies, this term is currently used as an expression of uncertainty. To examine the molecular features of a typical adenoma, we analyzed the p53 genes in 2 atypical adenomas and 12 control lesions (6 typical follicular adenomas and 6 follicular carcinomas). Mutations of p53 were detected in the bizarre cells of the atypical adenomas, but not in the bland-looking follicular cells or in the control specimens. Both atypical adenomas showed an identical point mutation in codon 273 (CGT-->CAT), a common mutation in various human cancers, including anaplastic carcinoma of the thyroid. This finding supports the view that atypical follicular adenoma is a precursor of thyroid anaplastic carcinoma and suggests that "atypical adenoma" should not be used to express diagnostic uncertainty about the nature of a lesion.

Thyroid cell proliferation in response to forced expression of gap junction proteins

Gap junctions are known to play a role in the control of cell proliferation, and connexins (Cx) are considered to be tumor suppressors. However, the effects of Cx on cell proliferation are dependent on the Cx which is expressed and on the cell type under consideration. We previously found that restoration of cell-to-cell communication by stable transfection of two independent thyroid-derived cell lines, FRTL-5 and FRT cells, with the Cx32 gene induced a marked reduction of their proliferation rate. This study aimed i) at determining whether Cx43, which is coexpressed with Cx32 by thyroid epithelial cells, exerts the same action as Cx32 on cell proliferation and ii) at identifying alterations of the cell cycle control system that might account for the Cx32-induced proliferation slowdown in thyrocytes. In contrast with previous data on different epithelial cell types, we report that restoration of intercellular communication in FRTL-5 and FRT cells by stable expression of Cx43 did not modify their proliferation properties. Cell cycle analyses revealed that the Cx32-induced proliferation slow-down was related to a lengthening of the G1 phase. The level of expression of two regulatory proteins of the Cip/Kip cyclin-dependent kinase inhibitor family, p27kip1 and p2cip1, was increased in the two cell lines expressing Cx32. In conclusion, Cx32 and Cx43, physiologically coexpressed by thyrocytes, have a differential impact on thyroid cell proliferation in vitro. The cyclin-dependent kinase inhibitors, p27kip1 and p21cip1 might represent cell cycle effectors relaying the down-regulatory effect of Cx32 on the proliferation of thyroid epithelial cells.

P53 mutations in thyroid carcinoma: tidings from an old foe

The underlying mechanism leading to carcinogenesis involves genomic instability, likely related to aneuploidy. While p53 as a "guardian of the genome" is an appealing candidate as an initiator of genomic instability, its mutations or deletions usually occur late in the course of tumor progression. P53 may, however, become a target of events initiated by genomic instability. P53 is a transcription factor with multifaceted regulatory functions in the cell cycle, DNA repair and apoptosis. Inactivating p53 mutations have been described in some 50% of human cancers. These mutations are not only important in tumor progression but apparently also in the response of some tumors to chemotherapy and radiation treatment, thus to clinical outcome. P53 mutations are found in 14% of malignant thyroid tumors and are more frequent in poorly differentiated and anaplastic tumors. We have examined the mutation rates of p53 as a measure of genomic instability (hypermutability) of malignant thyroid tumors. We also wondered whether radiation enhances this tendency to genomic instability. To those ends we extracted all available entries from the p53 mutations database (http://www.perso@curies.fr), verified, extended where applicable, and supplemented that information from the original published reports. We were able to locate 100 entries. The distribution of the types of p53 aberrations in thyroid cancer was similar to those in the database as a whole. The silent mutation rate of 20%, not different from the expected 25%, is consistent with a random occurrence of these mutations. This silent mutation rate is 130 times that expected and is 7 times that of the p53 database. Moreover the distribution of p53 mutations is compatible with Poisson's distribution, which, when considered in the context of the silent mutation rates, indicates that p53 is particularly hypermutable in thyroid cancer. Epigenetic deamination of CpG dinucleotides at highly transforming DNA-contact residues is a feature of poorly differentiated tumors and thus associated with tumor progression. The rates of p53 mutations in radiation-related thyroid cancers (15.4%) are similar to those in spontaneously arising tumors, although there was a highly significant heterogeneity (p<0.0005) in the residues mutated in the two tumor sets. None of the residues mutated in radiation-related thyroid cancer involved CpG deamination. Based on the evidence of p53 hypermutability, thyroid cancer appears to exhibit remarkable genomic instability. Spontaneous epigenetic mutational events are involved in tumor progression. While thyroid cancer related to radiation exposure does not increase the rates of p53 mutation, they exhibit mutation at residues not involved in p53/DNA interface.

Thyroid carcinoma is characterized by genomic instability: evidence from p53 mutations

p53 is a transcription factor with multifaceted regulatory functions in cell cycle progression, DNA repair, and programmed cell death. Inactivating mutations have been described in 50% of human cancers. These mutations appear to be important in tumor progression and response to chemotherapy and radiation treatment and thus clinical outcome. p53 mutations are found in 14% of malignant thyroid tumors and are more frequent in poorly differentiated and anaplastic tumors. Given that p53 is a late event in the notional multistep pathogenesis of cancer, we examined its mutation rates as a measure of genomic instability (hypermutability) of malignant thyroid tumors and also wondered whether radiation enhances that proclivity to genomic instability. To that end we have extracted all available data from the p53 mutation database (http://www.perso@curie.fr), verified, extended, where applicable, and supplemented that information from published reports. We were able to identify 100 entries. The distribution of the p53 mutational events--deletions/insertions, transitions versus transversion mutations--was similar to that of the database as a whole. The silent mutation rate of 17.8%, not different from the expected 25%, is consistent with a random occurrence of these mutations. The silent mutation rate is 120 times that expected and is 6 times that of the database. Moreover, the distribution of p53 mutations is compatible with Poisson's distribution, which taken with silent mutation rates indicates that p53 is particularly hypermutable in thyroid carcinomas. Epigenetic deamination of CpG dinucleotide at highly oncogenic DNA-contact residues is a feature of poorly differentiated tumors and thus associated with tumor progression. The rates of p53 mutations (15.4%) in radiation-related cancers were very similar to those in apparently spontaneously arising tumors, although there was a highly significant heterogeneity (P < 0.0005) in the residues mutated. None involved CpG deamination. It is apparent that thyroid cancer exhibits remarkable genomic instability evidenced by p53 hypermutability. Spontaneous epigenetic mutational events are involved in tumor progression and while radiation increases the absolute prevalence of thyroid cancer in the susceptible it does not increase the rate of p53 mutation and seemingly targets different non-DNA-contact residues than those in spontaneously arising tumors.

Bax expression in benign and malignant thyroid tumours: Dysregulation of wild-type P53 is associated with a high Bax and P21 expression in thyroid carcinoma

The purpose of our study was to determine the expression of the pro-apoptotic BAX protein in relation to the mutational status of BAX and p53 (as transcriptional activator of the BAX gene) in benign and malignant thyroid tissue. In 47 patients with thyroid tumours (14 follicular and 3 papillary carcinomas, 14 adenomas and 16 goitres), the DNA was screened for mutations of BAX (exon 1-6) and p53 (exon 5-8) by single-strand conformation polymorphism polymerase chain reaction (SSCP-PCR). Furthermore, the protein expression of BAX, p53 and p21 (which is also increased transcriptionally by p53) was investigated by immunohistochemistry. Surprisingly, we observed elevated BAX levels in patients with thyroid carcinomas compared with patients with adenomas (unpaired t-test: p<0.05) or with goitres (p<0.02). This is in clear contrast to other carcinomas where BAX is frequently inactivated which correlates to a poor prognosis (Sturm et al. J. Clin. Oncol. 1999;17:1364-74.). There were no significant differences of the BAX levels between goitres or the adenomas. In the SSCP-PCR analysis, no BAX mutations were detectable. P53 mutation analysis by SSCP-PCR did not reveal any functional p53 mutations in the patients with carcinomas, adenomas or goitres. Nevertheless, patients with carcinomas showed an overexpression (preferentially cytoplasmic) of p53 protein compared with patients with benign tumours (p<0.05). The absence of p53 mutations suggests that the overexpressed p53 is wild type. This is in line with the expression profile of BAX and p21, which showed a higher protein expression in these p53 positive tumours (p<0.05 in the carcinomas compared with the non-malignant lesions). Consequently, the overexpressed p53 might be a correlate for dysregulation without loss of function. This, in turn, might be a reason for the good outcome of some patients with thyroid cancer.

Molecular pathogenesis of thyroid nodules and cancer

Tumours derived from the thyroid follicular epithelium represent an informative model for understanding the molecular pathogenesis of multistage tumourigenesis, which is the prevailing theory on cancer development and progression nowadays. The early stages of thyroid tumour development appear to be the consequence of the activation or 'de novo' expression of several proto-oncogenes or growth factor receptors, such as ras, ret, NTRK, met, gsp and the thyrotropin (TSH) receptor. Alterations in the expression pattern of these genes are associated with the development of differentiated neoplasms, ranging from benign toxic adenomas (gsp and TSH receptor), to follicular (ras) and papillary (ret/PTC, NTRK, met) carcinomas. They may all be considered to be early events of thyroid cell transformation and, for some, experimental evidence derived from gene transfer studies supports this hypothesis. Alterations in tumour suppressor genes (p53, Rb) are associated instead with the most aggressive and poorly differentiated forms of thyroid cancer, indicating that, in the thyroid tumourigenic process, they represent late genetic events. Specific environmental factors (iodine deficiency, ionizing radiations) have been shown to play a crucial role in promoting the development of thyroid cancer, influencing both its genotypic and phenotypic features. Interestingly, a high percentage of genetic lesions causing thyroid cancer originate from gene rearrangements and chromosomal translocations (ret/PTC, NTRK, Pax-8/PPARgamma) a finding which, being a rare event in most epithelial tumours, makes the molecular pathogenesis of thyroid cancer unique. The uninterrupted flow of information on the molecular genetics of thyroid nodules and cancer will broaden the correlation between genotype and phenotype and will also provide important information for the development of more accurate preoperative diagnostic tools and more efficient treatment choices for the different forms of thyroid cancer.

Recurrent fallopian tube carcinoma: TP53 mutation and clinical course

Primary fallopian tube carcinoma is a rare, aggressive gynecological cancer; little is known about its cause. Previous studies have indicated that p53 immunopositivity is correlated with short-term survival in primary fallopian tube carcinoma. We examined p53 and p21/WAF1 immunostaining and TP53 mutation in exons 5 to 8 by single-stranded conformation polymorphism and constant denaturant gel electrophoresis in nine cases of primary fallopian tube carcinoma and their metastases/recurrences from patients who survived for between a few months and more than 20 years after diagnosis. We found that 1.) p53 immunopositivity without detectable p21/WAF1 immunostaining did not correlate with TP53 mutations in the conserved domains; 2.) mutations in TP53 occurred in two metastases/recurrences but not in their corresponding primary tumors; 3.) in two cancers, a TP53 mutation was observed in the primary tumor but not in the metastases/recurrences; 4.) constant denaturant gel electrophoresis seems to be more sensitive than single-stranded conformation polymorphism in detecting TP53 mutations; and 5.) in the nine cases studied, p53 immunoreactivity and/or TP53 mutation analysis did not correlate with tumor progression, survival, or response to treatment.

Insular and anaplastic carcinoma of the thyroid: a 45-year comparative study at a single institution and a review of the significance of p53 and p21

OBJECTIVE

To analyze the clinicopathologic features of a large cohort of patients with insular or anaplastic carcinomas treated at a single institution.

SUMMARY BACKGROUND DATA

Insular and anaplastic carcinomas of the thyroid, although uncommon, have more aggressive clinical behavior than well-differentiated carcinomas of the thyroid. In the literature, the incidence and features of these carcinomas have not been fully characterized.

METHODS

The authors reclassified 740 primary thyroid carcinomas diagnosed and treated between January 1, 1954, and December 30, 1998, to select those with features that met the histologic criteria of insular or anaplastic carcinoma. The clinicopathologic features of these carcinomas were studied and compared. The expression of p53 and p21 in these tumors was analyzed by immunohistochemistry.

RESULTS

Twenty-two patients (5 men, 17 women) with insular carcinoma and 38 patients (7 men, 31 women) with anaplastic carcinoma were found. Patients with insular carcinomas were younger (mean age 45 vs. 70 years) and had smaller tumors than those with anaplastic carcinomas (mean diameter 5 vs. 8 cm). Insular carcinomas were commonly mislabeled as other histologic subtypes, whereas anaplastic carcinomas might be overdiagnosed on pathologic examination. A history of longstanding goiter (>10 years) was noted in 27% of patients with insular carcinoma and 24% of patients with anaplastic carcinomas. Concomitant well-differentiated carcinomas of the thyroid were noted in 59% of patients with insular carcinoma and 39% of patients with anaplastic carcinoma. In anaplastic carcinomas, 13% of patients had concomitant insular carcinoma. Calcification or bone was noted in the stroma of 23% of patients with insular carcinomas and 47% of those with anaplastic carcinomas. The 10-year survival rates for patients with insular carcinoma and anaplastic carcinoma were 42% and 3%, respectively. Distant metastases were seen in 32% of patients with insular carcinoma and in 47% of patients with anaplastic carcinomas. In both types of carcinomas, metastatic tumors were often seen in bone and lung. Distant metastases were noted in a variety of organs in anaplastic carcinomas. In insular carcinoma, neither p53 nor p21 expression was present. In anaplastic carcinoma, p53 and p21 expression was identified in 69% and 3%, respectively. Concomitant expression of p53 and p21 was noted in one tumor.

CONCLUSIONS

Insular carcinoma and anaplastic carcinoma had distinctive clinicopathologic features, and recognition of these histologic variants is important for better management of these tumors in the future. p53 overexpression might have a role in dedifferentiation from insular carcinoma to anaplastic carcinoma.

Molecular alterations involving p53 codons 167 and 183 in papillary thyroid carcinomas from chernobyl-contaminated regions of belarus

After the Chernobyl accident in 1986, there was a significant increase in the incidence of papillary thyroid carcinoma in fallout-exposed children from Belarus. We studied the p53 gene from 24 papillary thyroid carcinoma cases presenting in 1996. All subjects lived in contaminated regions of Belarus at the time of the accident and were under age 20 when exposed to fallout. Exons 5 through 9 of p53 were amplified from genomic tumor DNA using the polymerase chain reaction (PCR). The PCR products were analyzed by direct DNA sequencing using an automated sequencer. Five cases each exhibited two molecular alterations within exon 5. Alterations were confirmed by sequencing in both directions. One alteration, involving codon 167 (CAG-->CAT) in all five cases, resulted in the substitution of HIS for GLN. The second alteration, involving codon 183 (TCA-->TGA) in all five cases, resulted in a premature termination codon. Leukocyte DNA from each of the positive cases was analyzed and found to contain only wild-type p53 sequence. These results suggest that mutations involving codons 167 and 183 in the p53 locus are important in the pathogenesis of a subset (21%) of radiation-induced papillary thyroid carcinomas from Belarus.

Prognostic significance of p53 and p21(waf1/cip1) immunoreactivity in epithelial cancers of the ovary

OBJECTIVES

Theprognostic value of p53 expression in epithelial ovarian cancer remains unresolved. We hypothesized that prognosis may relate more to expression of p21(waf1/cip1), the major downstream effector of p53, which can also be induced through p53-independent mechanisms. We therefore studied the relationship of p53 and p21(waf1/cip1) expression in epithelial ovarian cancers to clinicopathological variables and prognosis.

METHODS

Fixed, embedded tumors from 85 patients with untreated, primary epithelial ovarian cancer were immunostained with antibodies to p53 and p21(waf1/cip1). Expression was correlated with clinicopathological features and prognosis. Survival curves were calculated by the Kaplan-Meier method and compared using the log-rank test for p53, p21(waf1/cip1), and all combinations of expression of the two markers.

RESULTS

Sixty-two percent of tumors expressed p53, and 42% expressed p21(waf1/cip1). There was no correlation between p53 and p21(waf1/cip1) expression. Advanced stage, grade, age >/=50, and p53 expression were associated with worse disease-free survival. Patients whose tumors were p53(+)/waf1(-), however, had a particularly strong association with poorer disease-free survival when compared with other combinations of p53 and p21(waf1/cip1) expression (P = 0.003). Neither p53, nor p21(waf1/cip1), nor combinations of expression were independently related to survival when histology, age, stage, and differentiation were considered.

CONCLUSIONS

p53 expression in the absence of p21(waf1/cip1) expression is a better marker of poor prognosis than either p53 or p21(waf1/cip1) expression status alone in univariate analysis. Absence of independent prognostic significance may be related to the paucity of early stage cases in the current study.

K-ras and p53 mutations in the pathogenesis of classical and goblet cell carcinoids of the appendix

BACKGROUND

Mutations in the K-ras oncogene and the p53 tumor suppressor gene are present in approximately 50% of colonic adenocarcinomas. Goblet cell carcinoids (GCCs) are uncommon neoplasms of the appendix that appear to be intermediate between carcinoid tumors and adenocarcinomas, both histologically and biologically. The current study was undertaken to examine the role of p53 and K-ras mutations in the pathogenesis of GCCs and typical carcinoids (TCs) of the appendix.

METHODS

Archival materials from 22 GCCs and 18 TCs were analyzed. K-ras mutations in codons 12, 13, and 61 were studied by a polymerase chain reaction (PCR) based designed restriction fragment length polymorphism method using mismatched nested primers. Mutations in exons 5-8 of the p53 tumor suppressor gene were analyzed in 16 GCCs and 18 TCs by PCR and single-strand conformational polymorphism followed by direct sequencing. Immunostains for p53 and chromogranin were performed in all cases.

RESULTS

K-ras mutations and nuclear accumulation of p53 by immunohistochemistry were not detected in any of the GCCs or TCs. p53 mutations were found in 4 of 16 GCCs (25%) and 8 of 18 TCs (44%). Immunoreactivity for chromogranin was seen in the vast majority of GCCs and TCs.

CONCLUSIONS

p53 mutations appear to play a role in the pathogenesis of some GCCs and in approximately 50% of TCs of the appendix, whereas mutations in the K-ras oncogene do not appear to be important in the development of these tumors. The minimal cytologic atypia, low incidence of metastases, and lack of K-ras mutations in goblet cell appendiceal neoplasms suggest that they are variants of carcinoid tumors. Our findings lend support to the recommendation that the therapeutic guidelines applied to TCs of the appendix should be the same for GCCs.

p27kip1: a multifunctional cyclin-dependent kinase inhibitor with prognostic significance in human cancers

p27kip1 (p27) is a member of the universal cyclin-dependent kinase inhibitor (CDKI) family. p27 expression is regulated by cell contact inhibition and by specific growth factors, such as transforming growth factor (TGF)-beta. Since the cloning of the p27 gene in 1994, a host of other functions have been associated with this cell cycle protein. In addition to its role as a CDKI, p27 is a putative tumor suppressor gene, regulator of drug resistance in solid tumors, and promoter of apoptosis; acts as a safeguard against inflammatory injury; and has a role in cell differentiation. The level of p27 protein expression decreases during tumor development and progression in some epithelial, lymphoid, and endocrine tissues. This decrease occurs mainly at the post-translational level with protein degradation by the ubiquitin-proteasome pathway. A large number of studies have characterized p27 as an independent prognostic factor in various human cancers, including breast, colon, and prostate adenocarcinomas. Here we review the role of p27 in the regulation of the cell cycle and other cell functions and as a diagnostic and prognostic marker in human neoplasms. We also review studies indicating the increasingly important roles of p27, other CDKIs, and cyclins in endocrine cell hyperplasia and tumor development.

The molecular genetics of endocrine tumours

The molecular genetics of endocrine tumours is an area of great interest, due to the heterogeneity of endocrine tumour types, the association of hormone over-production in some cases, and the wide variation in tumour behaviour. Genes implicated fall into functional categories such as oncogenes, in which mutations tend to cause activation, and tumour suppressor genes, in which mutations lead to loss of function. Oncogenes include the receptor tyrosine kinases such as RET, signal transduction proteins and other molecules such as cell cycle regulators and nuclear proteins. Tumour suppressor genes include cell cycle regulators such as p53 and other molecules such as the MEN 1 gene. Loss of heterozygosity studies help in the initial localisation of the latter. Endocrine tumours, as with other tumours, develop as a result of a combination of genetic events, and in the paediatric age group they often occur in the setting of familial cancer syndromes. In this review we analyse the main genetic lesions which have been described in endocrine tumours. There has been an explosion of knowledge in the last 5 years including the identification of the causative genes for MEN 2 and most recently for MEN 1. Characterisation of such genes also aids in the study of somatic mutations in sporadic versions of the same tumour types as occur in the familial syndromes. Identification of a genetic predisposition to a certain tumour has management implications that are still to be clarified in most cases, although in the case of MEN 2 the guidelines for prophylactic thyroidectomy are generally well accepted.

The pattern of p53 and p21WAF1/CIP1 immunoreactivity in non-Hodgkin's lymphomas predicts p53 gene status

P53 and p21WAF1/CIP1 (p21) immunostaining was performed on 92 non-Hodgkin's lymphomas (NHLs), and the staining pattern correlated with the presence or absence of p53 hot spot mutations as detected by PCR-SSCP of exons 5-8 and direct sequencing. Twenty-nine of 92 lymphomas overexpressed p53, and 17 overexpressed p21. Of the p53 overexpressing lymphomas, 14 also overexpressed p21, and none of these 14 harbored a detectable hot spot mutation. However, mutations were detected in 13 (87%) of 15 p53 overexpressing, p21 negative lymphomas. One of the 63 p53-negative lymphomas harbored a detectable hot spot mutation, and it was also negative for p21. These results demonstrate that among NHLs that overexpress p53 protein, those which also show p21 overexpression do not harbor p53 hot spot mutations, and furthermore, provide evidence that the transactivating function of p53 is retained. On the other hand, p53 overexpression in NHLs that lack p21 expression is usually indicative of p53 gene mutation.

Absence of p21 expression is associated with abnormal p53 in human breast carcinomas

The p53 tumour-suppressor gene is important in the regulation of cell growth and apoptosis, and loss of functional wild-type activity may be associated with tumour formation and resistance to therapy. Differentiation of functionally normal wild-type protein from mutant or abnormal protein remains difficult using either immunohistochemical assays or mutational DNA sequencing. p21(WAF1/CIP1) (p21) is induced by wild type p53 and plays an important role in promoting cell cycle arrest. To test the hypothesis that p21 protein expression may act as a downstream marker of tumours from patients with locally advanced breast cancer before treatment with doxorubicin, pretreatment p53 status had been characterized in 63 tumours by p53 protein immunostaining and DNA mutational analysis. There was a significant association between immunostaining for p53 and the presence of p53 mutations (P = 0.01). Of 56 patients available for determination of p21, 31 (55%) expressed p21 protein. Twenty-eight out of 31 patients (90%) positive for p21 had low negative p53 protein expression, whereas only 3 of 13 patients (23%) with high p53 expressed p21 (P = 0.009). No association was seen between p21 protein expression and p53 mutations (P = 0.24). The combination of p53 and p21 immunostaining results improved the specificity of the immunostaining but at a cost of significant reduction in sensitivity. Immunohistochemical assessment of p21 protein expression is inversely associated with abnormal p53 protein in human breast cancer. The detection of p21 protein expression in combination with p53 protein expression did not improve the ability of immunohistochemistry (IHC) to differentiate between normal and mutant p53 protein.