P53 Gene Alterations Research Articles

P53 Mutation in Inflammatory Breast Cancer Cell Lines.

Abstract Background: Inflammatory breast cancer (IBC) is the most aggressive manifestation of primary breast cancer and represents 1% to 2% of primary breast cancer in the United States. IBC is characterized by an acute inflammation of the skin of the affected breast generally believed to be caused by blockage of the dermal lymphatics by tumor emboli. Wild type (WT) p53 is a tumor suppressor gene, which induces apoptosis and p53 mutations are associated with poor prognosis in breast cancer. Compared with locally advanced breast cancers, IBC patients have higher levels of mutated p53 protein that has been associated with more aggressive tumors, anthracycline resistance, shorter progression free survival, shorter overall survival, and less favorable long-term outcome. The aim of this study was to determine if there are unique genetic variations in IBC cell lines that would provide specific genetic p53 mutations that could be exploited for targeted therapy with the intent of improving response to treatment and overall survival in IBC.Materials and Methods: Genomic DNA was extracted from six breast cancer cell lines (MDA-453, SUM149, MCF-7, KPL4, MDA321, and SUM190) and the immortalized human mammary epithelial cells (HMLE) using the Qiagen DNA Blood Mini Kit (Valencia, CA). Among the 6 breast cancer cell lines, KPL-4, SUM149 and SUM190 are IBC cell lines; MDA231 and SUM149 have basal-like phenotype; MCF-7 has wild-type p53; SUM190 and KPL-4 are Her2 amplified. The DNA purity and concentration were determined by spectrophotometric measurements of absorbance at 260nm and 280 nm. Polymerase chainreaction (PCR) was performed to amplify the fragments of exons 2-11 of the p53gene using consensus primers. The PCR products were scanned and identified using the Agilent Bioanalyzer 2100. DNA sequencing was performed on PCR products in the ABI PRISM 310 Genetic Analyzer. The BLAST search was used to identify p53 mutations compared with the reference sequence, X54156, from Genbank.Results: We screened 2-11 exon sequences of the p53 gene in the 7 human breast cell lines. We identified two IBC cell lines (SUM149, SUM-190) with a p53 gene alteration that predicted a change in the encoded protein, SUM149 at exon 7 (ATG to ATA, Met-237-Ile) and SUM190 at exon 9 (CAG to TAG, Gln -317-stop). Both mutations have been previously reported. Five nonsense mutations were identified in two other cell lines, MDA-453 and MDA321. No mutations were identified in KPL4 and HMLE cells.Conclusions: The p53 mutation profile in breast cancer cell lines suggests an additional biological feature for the characterization of IBC. Furthermore, these data support the previously reported association between p53 status and chemo- and radioresistance in this disease responsible for poor prognosis. Therapies directed to restore p53 function should be explored in IBC models and in clinical trials. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3161.

Oligonucleotide Probe Array for p53 Gene Alteration Analysis in DNA from Formalin‐Fixed Paraffin‐Embedded Breast Cancer Tissues

Mutations in the TP53 tumor-suppressor (p53) gene represent the most common molecular changes in various malignancies, including breast cancer (BC). We sequenced the p53 gene in DNA extracted from archival paraffin-embedded BC tissues and compared the results obtained from direct sequencing with those obtained by oligonucleotide probe array (OPA). DNA was extracted from 34 samples. OPA correctly detected 13 genetic alterations in 14 cases, with a mutation frequency of 41.2%. No changes were detected in exons 3, 4, 9, 10, and 11 and no polymorphisms were found. Direct manual sequencing in which DNA was amplified by PCR showed 21 genetic mutations in 19 (55.9%) cases. Eight mutations were identified by both OPA and PCR methods. Although OPA detected fewer gene alterations than direct sequencing, the difference was not significant (P= 0.11). In conclusion, the OPA may be safely used to identify individual genetic variations of human p53 gene in BC specimens.

P53 mutations in keratocystic odontogenic tumour

AbstractAim: The abrogation of the function for the tumour suppressor gene p53 has been suggested as one of the most common genetic alterations in neoplasia. We evaluated p53 mutations, clinico‐pathological and immunohistochemical findings in patients with sporadic keratocystic odontogenic tumours (KCOTs).Material and methods: A total of 32 patients with KCOT treated surgically were enrolled in this study. We performed mutation analysis of p53 using archival formalin‐fixed paraffin‐embedded tissue. The immunohistological technique was employed to identify TP53 expression. P53 mutations in exons 5–8 were evaluated by direct sequencing. These results were compared with the characteristics of each tumour.Results: Forty‐four percent of the cysts showed overexpression of TP53. P53 mutations were detected in 10 cases (31.3%) of 32 KCOTs; two cases within exon 5, two cases within exon 8, five cases within exon 7 and one case in both exons 5 and 7. Five missense mutations (R248G, D247K, Q136R, V272M, V143A) and four silence mutations (138A, 158R, 247D, 279G,) were detected. P53 mutation was detected in two (50%) out of four recurrence cases and eight (28.5%) out of 28 non‐recurrence cases (P = 0.572). R248G mutation was the most common in KCOTs (15.6%). We did not detect any remarkable associations of these cases carrying p53 mutations to clinico‐pathological and immunohistochemical characteristics.Conclusion: The results implied that the p53 gene alterations are involved in the development of KCOT.

Correlation of p53 over-expression and alteration in p53 gene detected by polymerase chain reaction-single strand conformation polymorphism in adenocarcinoma of gastric cancer patients from India

To study the alterations in p53 gene among Indian gastric cancer patients and to correlate them with the various clinicopathological parameters. A total of 103 gastric cancer patients were included in this study. The p53 alterations were studied by both immunohistochemical method as well as polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis. We only studied four (exon 5, 6, 7, and 8) of the 11 p53 exons. The alterations in p53 were also correlated with respect to various clinicopathological parameters. Among 103 cases, p53 over-expression and alteration were detected in 37 (35.92%) and 19 (18.44%) cases, respectively. Most of the p53 alterations were found at exon 5 (31.54%), followed by exon 6 (26.31%), exon 7 (21.04%) and exon 8 (21.04%). A significant correlation of p53 over-expression was found with p53 alteration (P = 0.000). Concordance between p53 alteration (as detected by SSCP) and over-expression [as detected by immunohistochemistry (IHC)] was found in 75% cases. We found that IHC-positive/SSCP-negative cases accounted for 21% of cases and IHC-negative/SSCP-positive cases accounted for remaining 4% cases. Our results show that p53 gene mutations are significantly correlated with p53 protein over-expression, with 75% concordance in over-expression and alteration in the p53 gene, but 25% disconcordance also cautions against the assumption that p53 over-expression is always associated with a gene mutation. There may be other mechanisms responsible for stabilization and accumulation of p53 protein with no evidence of gene mutation that reflect an accumulation of a non-mutated protein, or a false negative SSCP result.

Malignant transformation of mature cystic teratoma to squamous cell carcinoma involves altered expression of p53‐ and p16/Rb‐dependent cell cycle regulator proteins

Ovarian mature cystic teratomas (MCT) uncommonly undergo malignant transformation to squamous cell carcinoma (SCC). While alterations in the p53 tumor suppressor gene and protein have been shown, few studies have analyzed other molecular changes leading to this malignant conversion. The purpose of the present study was to investigate 21 samples of SCC arising in MCT for altered expression in known p53- and p16/Rb-dependent cell cycle regulatory proteins, and the association between their expression and cellular proliferation and histological features. Overexpression of the p53 protein was observed in 14 SCC (67%), while four (19%) had point mutations in the p53 gene. Reduced expression of the p16 protein was observed in 18 SCC (86%), while p16 gene alterations (hypermethylation (29%) and point mutation (33%)) were found in 11 (52%). Furthermore, a statistically significant correlation was observed between p53 and Rb overexpression (P=0.0010), and the overexpression of both p53 and Rb was respectively significantly correlated with increased cellular proliferation. The results indicate that alterations in both the p53 and p16-Rb pathways are associated with SCC arising in MCT.

Establishment and characterization of a new human acute myelocytic leukemia cell line SH-2 with a loss of Y chromosome, a derivative chromosome 16 resulting from an unbalanced translocation between chromosomes 16 and 17, monosomy 17, trisomy 19, and p53 alteration

To report here a new acute myelocytic leukemia (AML) cell line SH-2 and describe its biological characteristics. Mononuclear cells isolated from a patient with AML-M2 subtype were passaged by liquid culture medium. Interleukin-3 and bone marrow stromal cells were used to support cell proliferation at the first 3 months. Various methods, including cytogenetic analysis, fluorescence in situ hybridization (FISH), multiplex FISH (M-FISH), reverse transcriptase polymerase chain reaction (RT-PCR), multiplex RT-PCR, short tandem repeat (STR)-PCR, direct sequencing of DNA, clonogenic assay, and tumorigenicity in nude and severe combined immunodeficient (SCID) mice were employed to identify and characterize SH-2 cell line. SH-2 cells were maintained without cytokine and stromal cells for 3 years. It had no Epstein-Barr virus or mycoplasma contamination. The SH-2 cell line showed typical myelocytic features in morphology and simultaneous strongly expressed myeloid antigens (CD13, 99.6% and CD33, 99.26%) and natural killer (NK)-related antigens (CD56, 99.5% and CD16/56, 99.62%) suggesting that SH-2 is an AML cell line with NK-antigen expression. SH-2 cell line initially showed a karyotype of 45, X, -Y, der(16)t(16;17)(q24;q12), -17, +19. During the passage period, the cells with a hypodiploid karyotype gradually decreased and were replaced by the near-tetraploid cells with a karyotype of 71-105(86), XX, -Y, -Y, der(16)t(16;17)x2, -17, -17, +19, +19. FISH and M-FISH delineated all abnormalities. SH-2 cells had the approximately same morphological, immunophenotypical, and cytogenetic features as the patient's leukemia cells had. STR-PCR provided powerful evidence for the derivation of SH-2 cell line from the patient's leukemia cells. SH-2 cells showed multiple drug resistance (MDR), which may be related to the p53 gene alteration, including the loss of one p53 allele due to the monosomy 17 and a point mutation of CAG to CAT at codon 576 of exon 5 in another p53 allele resulting in the loss of p53 gene function. In addition, SH-2 cell line did not express MDR-related genes, such as MDR1, multidrug resistance-related protein, and lung resistance protein, but expressed apoptosis-related genes, such as Bcl-2, Fas, glutathione S-transferase-pi, and p21, which were also related to the MDR. SH-2 cell line had tumorigenic capacities in nude and SCID mice. Because SH-2 cell line had a clear biology background, it will provide a useful tool for the study of the pathogenesis and treatment strategy of AML with MDR.

P53 gene alterations and HPV16 infection in early stages of cervical carcinomas in Serbia

p53 gene alterations and HPV16 infection in early stages of cervical carcinomas in Serbia

Chromosome 9 instability and alterations of p16 gene in squamous cell carcinoma of the lung and in adjacent normal bronchi: FISH and immunohistochemical study

p16, a tumour suppressor gene located at 9p21 chromosome and involved in cell cycle regulation, is often inactivated in lung carcinoma. Inactivation is also supported by the loss of p16 protein, a strong inhibitor of cyclin-dependent kinase (CDK) 4 and 6. The aim of this study was to examine alterations of p16 both in pulmonary squamous cell carcinoma (SCC) and in morphological normal bronchi contiguous with neoplasia. p16 gene and chromosome 9 alterations were examined by fluorescence in situ hybridization and the expression of p16 protein by immunohistochemistry in pulmonary surgical specimens from 31 patients with SCC. As controls, surgical specimens from 13 patients with non-neoplastic pathology were examined. Tumours showed molecular alterations for p16 gene and chromosome 9 abnormalities in, respectively, 29/31 and 19/31 cases respectively. p16 protein was unexpressed in 29/31 cases. In morphologically normal bronchi p16 gene and chromosome 9 alterations occurred in, respectively, 13/31 and 4/31 cases respectively; loss of protein immunoreactivity occurred in 14/31 cases. No alterations were seen in any of the control cases. Inactivation of p16 gene in histologically normal bronchi could aid the identification of individuals at risk of developing SCC of the lung.

Epithelial and stromal genetic instability linked to tumor suppressor genes in ulcerative colitis-associated tumorigenesis

Objective. We have previously documented not only epithelial but also stromal genetic instability in ulcerative colitis (UC)-associated lesions, including adenocarcinomas, using microsatellite markers close to the p53 gene on chromosome 17 (Chr.17). However, about half of the UC-associated tumors do not have p53 gene alterations. The purpose of this study was to detect early genetic instability (loss of heterozygosity (LOH) and microsatellite instability (MSI)) of both epithelial and stromal cells in UC-associated tumorigenesis, using different microsatellite markers from the p53 gene. Material and methods. The laser-captured microdissection-PCR-GeneScan method was applied to investigate genetic instability in both the epithelial and stromal elements of early UC-associated lesions (regenerative mucosa and dysplasia) and carcinomas using multiple microsatellite markers, chiefly close to tumor suppressor genes (TSGs: p16INK4A, Rb, Smad4 and fragile histidine triad (FHIT)). Furthermore, expression of their gene products was analyzed by immunohistochemistry. Results. In epithelium, although LOH for Chr.17 markers increased along with histological progression, the frequencies of LOH or MSI for TSG markers were found to be almost constantly increased in both stromal and epithelial components of all lesion types. In contrast, genetic instability of National Cancer Institute (NCI)-recommended standard markers was not found to be significantly correlated with UC-associated tumorigenesis. Immunohistochemically, epithelial p16INK4A expression tended to be decreased in LOH-positive lesions (p=0.0780) and Smad4 expression was significantly decreased (p<0.05). Conclusions. These results suggest that genetic instability in the stroma, especially regarding TSG markers, may play an important role in early-phase, UC-associated tumorigenesis. In addition, decreased expression of TSG due to genetic alteration might contribute to tumorigenesis.

Diagnostic And Prognostic Significance Of p53 Protein Expression In Squamous Cell Lesions Of The Oral Cavity

Aims: The present study evaluated the role of tumour suppressor gene protein p53 in squamous cell lesions of the oral cavity. Settings and Design: A single institutional prospective study. Methods and Material: The evaluation of p53 (by IHC using Clone DO7 monoclonal antibody, DAKO, USA) was done on 50 cases of squamous cell lesions of oral cavity. Statistical analysis used: Student's't' test was performed. Results: The p53 expression increased with increasing degree of dysplasia and grade of SCC. There was a statistically significant difference of p53 positivity between dysplasia & SCC (P< 0.001), WD-SCC & MD-SCC (P< 0.05), and WD-SCC & PD-SCC (P< 0.001). Significantly high p53 positivity (P< 0.001) was noted in cases presenting with lymph node metastasis. Conclusions: Alterations of p53 gene seem to be an early event in multistage oral carcinogenesis. Role of p53 gene even at later stages when metastasis has occurred has not been properly dealt with; taking the research a step further, our study has found a statistically significant increase in p53 expression in cases presenting with nodal metastasis thus suggesting that the mutant p53 gene continues to be important for progression and metastasis of SCC, and a higher p53 expression indicates poorer prognosis.

Overexpression of inducible nitric oxide synthase and accumulation of 8‐OHdG in nasopharyngeal carcinoma

Nitric oxide (NO), produced by inducible NO synthase (iNOS), has been suggested to cause oxidative stress, leading to 8-hydroxydeoxyguanosine (8-OHdG) accumulation and subsequent transversion mutation of DNA. The aim was to evaluate iNOS expression and the status of oxidative stress in nasopharyngeal carcinoma (NPC). Seventy-three cases of NPC were investigated to examine the immunohistochemical expression of iNOS, 8-OHdG and latent membrane protein-1 (LMP-1) and Epstein-Barr virus-encoded small RNA (EBER) expression using in situ hybridization. iNOS mRNA expression and p53 gene mutations were also assessed. Overexpression of iNOS, LMP-1 and EBER was observed in 62 (84.9%), 28 (38.4%) and 53 (72.6%) cases respectively. p53 gene mutation was found in 10 of 73 (13.7%) cases. Immunohistochemical iNOS expression was associated with the 8-OHdG labelling index, iNOS mRNA expression and p53 gene alteration (P < 0.0001, P = 0.016 and 0.0082 respectively). Our present findings suggest that the expression of iNOS induces oxidative stress in NPC. Although the presence of p53 mutation was associated with iNOS overexpression, the type of acid-base change of p53 was transition, but not transversion, which suggests that the p53 gene is not the direct target of DNA damage by 8-OHdG accumulation.

The pattern of p53 gene mutations on oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the result of accumulation genetic lesion and caused by specific mutation in specific key regulation genes. p53 gene is key target specific regulatory genes which function as negative regulators in cell cycle control. The highest mutation rates found in human cancers and the etiology in high risk populations and the pattern of molecular pathogenesis mechanism involved in the OSCC remain unclear. The purpose of this study was to determine the presence of alteration or mutation of p53 gene and to associate these mutations histopathological status of the patients such as well differentiated and poorly differentiated in OSCC in order to elucidate the molecular pathogenesis mechanism of OSCC based on the pattern of p53 gene. Using 40 untreated well and poorly differentiated OSCC biopsy samples and 16 normal patients were analyzed for the presence of mutation in the conserved region of the p53 gene exons 5 and or 7 by PCR-SSCP mutational analysis for p53 gene showed 70% of total samples : exon 5: 27.5% with heterozygous mutation 81.8%, exon 7: 55% with heterozygous mutation 100%. The incidence of p53 mutation was not significantly associated with well and poorly differentiated OSCC with the exception in exon 5 of p53 gene (p = 0.013) using contingency coefficient. This study concludes that mutation of p53 gene especially in exon 7 may not indirectly play in the progressivity of OSCC with the exception of mutation in exon 5 of p53 which indicates the essential role in the progressivity of OSCC.

Genetic alterations of APC, K-ras, p53, MSI, and MAGE in Korean colorectal cancer patients

Colorectal cancer (CRC) is one of the most rapidly increasing cancers in Korea, but no comprehensive analysis has been performed to speculate the genetic basis of CRC development. We investigated the presence of adenomatous polyposis coli gene (APC), Kirsten-ras (K-ras), p53, microsatellite instability (MSI), and melanoma antigen gene (MAGE) alterations in CRC and correlated the results obtained with clinical data. We collected 78 cancer tissues from CRC patients. Genetic analyses were performed on APC, K-ras, p53, and MSI (BAT 25 and BAT 26), and in addition, MAGE expression was tested by reverse transcription polymerase chain reaction. Correlations between genetic markers and clinical factors were analyzed after reviewing medical records. The positive rates for alterations of APC, K-ras, p53, MSI, and MAGE in 78 tissue samples were 33.3, 29.5, 34.6, 9.0, and 68.4%, respectively. Mutations were frequently detected in codons 1291 and 1450 of APC, in codon 12 of K-ras and in codons 248, 282, and 176 of p53. APC mutations were frequently noted in early-stage cancer, whereas MSI was observed in right-sided and multiple cancers. No associations were found between the presence of alterations in APC, K-ras, p53, MSI, and MAGE. In Koreans, positive rates of alterations in APC and p53 were slightly lower than those of APC and p53 in Caucasians, and the genetic alterations including MAGE expression are involved in 92.1% of CRCs. The lack of multiple mutations and of a relation between mutation rates and clinical stage suggest that genetic alterations might have independent influences on CRC development in Koreans.

Organ‐dependent susceptibility of p53 knockout mice to 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ)

p53 knockout mice are now being frequently used to identify the carcinogenic potential of chemicals, thus it is important to precisely assess the susceptibility of the animals to various test chemicals. In the present study the susceptibility of p53 nullizygous((-/-)), heterozygous((+/-)), and wild-type((+/+)) mice to 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) was investigated. Mice of all three genotypes were first fed a diet containing 100 or 300 p.p.m. IQ for 15 weeks in a short-term experiment. p53((+/-)) and ((+/+)) mice were then treated with IQ for 40 weeks and maintained without further treatment for an additional 12 weeks in the long-term experiment. In the forestomach, the incidence of squamous cell hyperplasia was significantly higher in p53((-/-)) than in ((+/-)) and ((+/+)) mice at 15 weeks and higher in ((+/-)) mice than ((+/+)) mice with long-term IQ treatment, indicating an elevated susceptibility of p53 knockout mice. In contrast, in the liver, various hepatocellular lesions developed mainly in female mice with long-term IQ exposure but no significant differences were evident between p53 knockout and wild-type mice, indicating a lack of elevated susceptibility in the knockout animals. Furthermore, polymerase chain reaction-single strand conformation polymorphism and sequencing analysis revealed relatively high (13/30) and low (1/15) incidences of p53 mutations (exons 5-8) in squamous cell hyperplasia and hepatocellular tumors, respectively. These results clearly indicate that the susceptibility of p53 knockout mice is organ-dependent, coinciding to some extent with the likelihood of p53 gene alteration in the induced tumors.

NEW P53 GENE MUTATION IN NON-CANCEROUS MUSTARD GAS EXPOSED LUNG

Objective Mustard gas (MG) is a poisoning chemical, mutagenic and carcinogenic alkylating agent. It is used during World War I and also Iran-Iraq conflict. The p53 tumor suppressor gene is involved in the pathogenesis of malignant disease. The aim of this study is to determine possible mutation in p53 gene of lung sample from mustard gas exposed patients. Material and Methods Twelve lung biopsy samples from 12 Mustard Gas exposed soldiers cases along with control cell line were studied for the presence of mutations in exons 4-9 of the p53 gene by PCR and direct sequencing. Results Among examined biopsies most of the samples demonstrated normal polymorphism with no significant defected mutations but in one sample one type of p53 gene alteration at codon 278 (CCT→CCA) on transcribed strand was detected. This Mutation has not been observed in another studies related to mustard gas exposure and p53 mutation databases. Conclusion In this study we have reported for the first time new p53 mutation in the lung sample of MG exposed patients. It is concluded that only one silent mutation were scanned with no signs of any type of cancer. This type of mutation was not in IARC p53 gene mutation database. Moreover, surrounding sequences of the mutated p53 gene codons have more 5'-GT and 5-GC sequences which have been found both by our study and only one another study on Japanese exposed to MG.

Study of p53 gene alteration as a biomarker to evaluate the malignant risk of Lugol-unstained lesion with non-dysplasia in the oesophagus

Mutations of the p53 gene are detected frequently in oesophageal dysplasia and cancer. It is unclear whether Lugol-unstained lesions (LULs) with non-dysplastic epithelium (NDE) are precursors of oesophageal squamous cell carcinoma (ESCC). To study the genetic alterations of NDE in the multistep process of oesophageal carcinogenesis, we determined the relationship between p53 mutations and LULs-NDE. Videoendoscopy with Lugol staining was performed prospectively in 542 oesophageal cancer-free subjects. Lugol-unstained lesions were detected in 103 subjects (19%). A total of 255 samples, including 152 LULs (NDE, 137; dysplasia, 15) and 103 paired samples of normal staining epithelium, were obtained from 103 subjects. After extraction of DNA and polymerase chain reaction analysis, direct sequencing method was applied to detect mutations of the p53 gene. The p53 mutation was detected in five of 137 samples with LULs-NDE (4%) and in five of 15 samples with dysplasia (33%). A hotspot mutation was found in 20% of LULs-NDE with p53 mutation and in 40% of dysplasia with p53 mutation. In contrast, no p53 mutations were found in 103 paired NDE samples with normal Lugol staining. In biopsy samples from oesophageal cancer-free individuals, the p53 missense mutations containing a hotspot mutation were found in NDE, which was identified as an LUL. These findings suggest that some LULs-NDE may represent the earliest state of oesophageal squamous cell carcinoma in Japanese individuals.

Clinicopathological Roles of Alterations of Tumor Suppressor Gene p16 in Papillary Thyroid Carcinoma

Alterations of the p16 gene are common in human cancers, but their roles in thyroid cancers have not been clearly defined. The aim of the present study was to investigate the clinicopathological roles of the p16 gene in papillary thyroid carcinoma (PTC). p16 gene alterations were investigated in 44 patients with PTC (9 men, 35 women) by immunohistochemistry, reverse transcriptase-polymerase chain reaction and methylation-specific polymerase chain reaction. The findings were correlated with their clinicopathological features. p16 protein expression, mRNA alterations, and promoter methylation were detected in 89% (n = 39), 77% (n = 33), and 41% (n = 18) of patients with PTC, respectively. There was no marked relationship between p16 protein expression, mRNA alteration, and promoter methylation. In follicular variant of PTC (FVPTC), there was a frequent lack of p16 protein expression and promoter methylation. PTCs showing p16 promoter methylation were often associated with a high AMES (age, metastasis to distant sites, extrathyroidal invasion, size) risk group and advanced pTNM (tumor-lymph node-metastasis) stages. p16 gene alterations are common and correlate with histological features and biological aggressiveness in PTC, suggesting that they might play an important role in its pathogenesis.

Interplay between human papilloma virus infection and p53 gene alterations in head and neck squamous cell carcinoma of an Indian patient population

Aim: To investigate the complex interplay between human papilloma virus (HPV) infection and p53 gene alteration in 92 head and neck squamous cell carcinoma (HNSCC) and 28 leukoplakia samples from...

Estudo genético do gene p16 pela técnica de PCR-SSCP e expressão de proteína p16 em melanomas de mucosa oral e melanomas cutâneos

FUNDAMENTOS: A deleção e mutação do gene CDKN2a que codifica um inibidor específico da ciclina dependente de quinase 4, a proteína p16, têm sido implicadas na tumorigênese do melanoma cutâneo. Entretanto, pouco se conhece sobre essas alterações genéticas em melanomas de mucosa oral. OBJETIVOS: Verificar a presença de alterações no gene p16 e sua expressão protéica em melanomas esporádicos orais e cutâneos. MATERIAL E MÉTODOS: Avaliaram-se 36 espécimes de melanoma primário (sete orais e 29 cutâneos). Analisaram-se três exons do gene p16, pela técnica da reação em cadeia da polimerase/polimorfismo conformacional de fita simples do DNA.Verificou-se a expressão tecidual de proteína p16 por técnica imuno-histoquímica. Relacionaram-se os resultados com a espessura dos melanomas cutâneos. RESULTADOS: Cinco dos sete melanomas orais e 17 dos 29 melanomas cutâneos apresentaram indício de alteração no gene p16. Alterações do exon 2 foram as mais freqüentes, sendo 19 casos nos produtos obtidos com o mesmo iniciador. Observou-se expressão tecidual de p16 em apenas um melanoma oral, em 10/13 (76,9%) casos de melanoma cutâneo de espessura até 1mm e em sete de oito (87,5%) casos de espessura superior a 1mm. CONCLUSÃO: A freqüência de indícios de alteração na análise genética de p16 nos melanomas de mucosa oral foi de 71,42% e de 58,6% nos cutâneos. É possível sugerir a participação de alterações do gene p16 na patogenia do melanoma esporádico de mucosa oral. Não houve relação da sugestão de alteração genética do gene p16 e de sua expressão tecidual com a espessura dos melanomas cutâneos de diferentes subtipos histológicos.

Colon Cancer and Gene Alterations: Their Immunological Implications and Suggestions for Prognostic Indices and Improvements in Biotherapy

Studies have shown that changes occur in c-Ki-ras, p53, and Bcl2 gene structure and function during the various stages of human colon carcinogenesis. Alterations of these genes are responsible for the establishment of a state of continuous stimulus for cell division and apoptotic inhibition at physiological and pharmacological levels. This paper focuses on the results of our research aimed at investigating how these gene alterations influence tumoral mechanisms on an immunological level and how immunological parameters can be used as prognostic markers for the passage of normal tissue to adenoma and adenoma to carcinoma. Overall, our data suggest that an alteration in the c-Ki-ras gene results in a switch to a suppressive type of immune response, determining an impairment of immune cell activation at both antigen- presenting-cell and T-cell levels. c-Ki-ras gene mutations, p53 deletions, and Bc12 expression, on the other hand, can be used as prognostic markers for the passage of normal tissue to adenoma and adenoma to carcinoma. The p53 oncogene does not appear to impair patients' immunological response further. In conclusion, an evaluation of c-Ki-ras, rather than p53 gene alterations, would seem to be more relevant in colon cancer prevention programs and biotherapy improvement.