TP53 mutations and MDM2 gene amplification in squamous-cell carcinomas of the esophagus in south Thailand

A Genomic Analysis of Esophageal Squamous Cell Carcinoma in Eastern Africa

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) comprises 90% of all esophageal cancer cases globally and is the most common histology in low-resource settings. Eastern Africa has a disproportionately high incidence of ESCC.

METHODS

We describe the genomic profiles of 61 ESCC cases from Tanzania and compare them to profiles from an existing cohort of ESCC cases from Malawi. We also provide a comparison to ESCC tumors in The Cancer Genome Atlas (TCGA).

RESULTS

We observed substantial transcriptional overlap with other squamous histologies via comparison with TCGA PanCan dataset. DNA analysis revealed known mutational patterns, both genome-wide as well as in genes known to be commonly mutated in ESCC. TP53 mutations were the most common somatic mutation in tumors from both Tanzania and Malawi but were detected at lower frequencies than previously reported in ESCC cases from other settings. In a combined analysis, two unique transcriptional clusters were identified: a proliferative/epithelial cluster and an invasive/migrative/mesenchymal cluster. Mutational signature analysis of the Tanzanian cohort revealed common signatures associated with aging and cytidine deaminase activity (APOBEC) and an absence of signature 29, which was previously reported in the Malawi cohort.

CONCLUSIONS

This study defines the molecular characteristics of ESCC in Tanzania, and enriches the Eastern African dataset, with findings of overall similarities but also some heterogeneity across two unique sites.

IMPACT

Despite a high burden of ESCC in Eastern Africa, investigations into the genomics in this region are nascent. This represents the largest comprehensive genomic analysis ESCC from sub-Saharan Africa to date.

Mouse double minute 2 amplification in oesophageal squamous cell carcinoma is associated with better outcome

AIMS

This study aimed to determine the frequency of mouse double minute 2 (MDM2) amplification in oesophageal squamous cell carcinomas (ESCC) and to clarify its prognostic significance.

METHODS AND RESULTS

We investigated MDM2 amplification on tissue microarrays using fluorescence in-situ hybridisation and analysed its correlations with clinicopathological features and outcomes in 515 Chinese ESCC patients. MDM2 amplifications were found in 37 of 515 ESCC patients (7.2%). They were significantly negatively correlated with tumour size (P = 0.045), disease progression (P = 0.002) and death (P = 0.003). Univariate analysis showed that the following clinicopathological factors were associated with disease-free survival (DFS) and overall survival (OS): differentiation (P = 0.025 for DFS and P = 0.061 for OS), vessel invasion (P = 0.001 and P = 0.002), nerve invasion (P = 0.009 and P = 0.001), clinical stage (P < 0.001 and P < 0.001) and MDM2 amplification (P = 0.012 and P = 0.014). Multivariate Cox regression analysis showed that MDM2 amplification was an independent prognostic factor for improved outcomes (P = 0.023 for DFS, P = 0.027 for OS) and the clinical stage was an independent prognostic factor for poor outcomes (P < 0.001). When survival analyses were conducted at different clinical stages, MDM2 amplification was associated with longer DFS and OS in stages I-II ESCC (P = 0.003 for DFS and P = 0.003 for OS), but there was no significant survival difference in stages III-IVa ESCC.

CONCLUSIONS

MDM2 amplification was significantly correlated with an improved patient outcome, especially in stage I and II disease, and was verified as an independent prognostic factor in our patients. Therefore, MDM2 amplification may be a potential biomarker for risk stratification of the lower stages of ESCC.

MDM2 copy number increase: a poor prognostic, molecular event in esophageal squamous cell carcinoma

The present study aimed to elucidate the clinicopathological significance of molecular alterations in MDM2 in esophageal squamous cell carcinoma (ESCC). A total of 399 resected cases of ESCC were examined by dual-color in situ hybridization for MDM2 and immunohistochemistry for p53 using tissue microarrays. Clinicopathological features were correlated with the MDM2 status. Among 362 cases with a successful dual-color in situ hybridization analysis, 19 (5%) and 13 (4%) had MDM2 amplification and chromosome 12 polysomy, respectively, and these were examined as an MDM2-positive group. A comparison between amplified and polysomic cases revealed that the latter were more strongly associated with preoperative chemotherapy than the former. Sixteen (50%) of 32 MDM2-positive cases had positive results in all tissue cores examined, indicating diffuse MDM2 alterations. Cases with the diffuse alteration of MDM2 were characterized by an advanced pT stage and extensive vascular infiltration. The relationship between MDM2 copy number increases and p53 mutations was weak, with the overexpression of p53 being similarly detected in MDM2-positive and MDM2-negative cases (59% versus 49%; P = .267). Overall survival was shorter in patients with MDM2-positive ESCC than in those without MDM2 alterations (P = .033). The poor prognostic value of MDM2 alterations became more obvious when only diffusely altered cases were counted (P = .005). In conclusion, the present study revealed that MDM2 copy number increases occurred in 9% of ESCC cases, and MDM2 alterations, particularly diffuse abnormalities, were associated with a poor prognosis. MDM2-altered ESCC may achieve beneficial effects from MDM2-targeted therapy.

The African Esophageal Cancer Consortium: A Call to Action

Esophageal cancer is the eighth most common cancer worldwide and the sixth most common cause of cancer-related death; however, worldwide incidence and mortality rates do not reflect the geographic variations in the occurrence of this disease. In recent years, increased attention has been focused on the high incidence of esophageal squamous cell carcinoma (ESCC) throughout the eastern corridor of Africa, extending from Ethiopia to South Africa. Nascent investigations are underway at a number of sites throughout the region in an effort to improve our understanding of the etiology behind the high incidence of ESCC in this region. In 2017, these sites established the African Esophageal Cancer Consortium. Here, we summarize the priorities of this newly established consortium: to implement coordinated multisite investigations into etiology and identify targets for primary prevention; to address the impact of the clinical burden of ESCC via capacity building and shared resources in treatment and palliative care; and to heighten awareness of ESCC among physicians, at-risk populations, policy makers, and funding agencies.

MDM2 gene amplification in esophageal carcinoma

Esophageal cancer (EC) is one of the most common malignancies diagnosed in the Western world with an increasing incidence noted for esophageal adenocarcinoma (EAC). Despite improvements in staging, surgical procedures and postoperative treatments, the overall survival of patients with EC remains low. Murine double minute‑2 (MDM2) acts as an oncogene by inducing the degradation of the tumor‑suppressor protein TP53. In order to evaluate the MDM2 gene amplification status in EAC and squamous cell carcinoma (SCC), we established a quantitative PCR (qPCR) assay, screening a total of 127 esophageal carcinoma cases for MDM2 amplification. Esophageal carcinoma cases with enhanced MDM2 gene copy numbers were further analyzed by fluorescence in situ hybridisation (FISH) and MDM2 immunostaining. Among a total of 23 specimens (18%), identified by qPCR to possess elevated MDM2 gene copy numbers, one third (6.3%) showed a cluster‑like fluorescence pattern by FISH analyses and marked MDM2 protein immunostaining. MDM2 gene amplifications did not correlate with the occurrence of TP53 mutations. Due to the high therapeutic relevance of MDM2 overexpression, but the high cost of FISH, we suggest a primary screening of MDM2 copy number variations by qPCR, followed by detailed FISH analysis of the identified ECs.

Specific intronic p53 mutation in esophageal squamous cell carcinoma in Southern Thailand

AIM

To investigate p53 mutations in esophageal cancer in a high-risk population, and correlate them with smoking, alcohol consumption and betel chewing.

METHODS

One hundred and sixty-five tumor samples of esophageal squamous cell carcinoma (ESCC) obtained from a university hospital in Songkhla province, Southern Thailand were investigated for p53 mutations in exons 5-8, using polymerase chain reaction-single strand conformation polymorphism analysis, followed by direct sequencing. A polymerase chain reaction-restriction fragment length polymorphism (RFLP) assay was additionally used to confirm possible germline mutation in intron 6. A history of risk habits was obtained by interviews. The association between risk habits and mutation frequency was evaluated using the χ(2) test.

RESULTS

The studied specimens were from 139 male and 26 female patients with ESCC, treated at Songklanagarind Hospital. Most of the patients were smokers (86.7%) and alcohol consumers (72.73%), and 38.3% were betel chewers. Forty-three mutations of the p53 gene were detected in 25.5% (42/165) of tumor samples. Mutations were most commonly found in exon 5 (25.6%) and exon 8 (25.6%). Mutations in the hot-spot codon 248 were found in four cases (9.3% of all mutations). G:C→C:G (30.23%), G:C→A:T (27.90%) and G:C→T:A (16.28%) were the prevalent spectra of mutations. Unexpectedly, among 10 intronic mutations, eight cases harbored a similar mutation: G→C substitution in intron 6 (nucleotide 12759, GenBank NC_000017). These were additionally confirmed by the RFLP technique. Similar mutations were also detected in their matched blood samples using RFLP and direct sequencing, which suggested germline mutations. There was no significant correlation between risk habits and p53 mutation frequency.

CONCLUSION

A proportion of Thai ESCC patients harbored specific intronic p53 mutations, which might be germline mutations. Further studies are needed to explore this novel finding.

MDM2 is overexpressed and regulated by the eukaryotic translation initiation factor 4E (eIF4E) in human squamous cell carcinoma of esophagus

BACKGROUND

We investigated the association between the increased eukaryotic translation initiation factor 4E (eIF4E) level and MDM2 overexpression in the esophageal cancer tissue and cells.

METHODS

This was a retrospective study of specimens from esophageal cancer patients treated over a 5-year period in a Taiwan university hospital. The predictor variable was eIF4E level in esophageal tumors and CE48T/VGH and TE6 esophageal carcinoma cell lines. The main outcome variable was MDM2 overexpression. Appropriate descriptive and univariate statistics were computed, and a P value of <0.05 was considered statistically significant.

RESULTS

There were two study sample groups. Immunohistochemistry analyses of the first sample group (51 esophageal tumors) revealed that 19 specimens demonstrated MDM2 elevation and 20 specimens had eIF4E overexpression. eIF4E elevation was evidenced by accumulation of the protein in the cytoplasm. There was a significant association between the eIF4E and MDM2 expression (P < 0.001). Western blot analysis and semiquantitative reverse transcriptase-polymerase chain reaction of the second specimen group (20 pairs of tumors and normal tissues) revealed the co-elevation of MDM2 and eIF4E (P = 0.008). There was no increased mdm2 transcript in most of the specimens. Without significant alterations in the mdm2 mRNA level and subcellular distribution, MDM2 protein was upregulated in CE48T/VGH cultured cells expressing ectopic eIF4E. Conversely, reduction of eIF4E by specific siRNA enabled TE6 cells synthesizing reduced amounts of MDM2.

CONCLUSIONS

Our findings indicate that MDM2 protein levels are strongly associated with and regulated by eIF4E in a posttranscriptional mechanism in esophageal cancer.

p53 Mutations in carcinoma of the esophagus and gastroesophageal junction

BACKGROUND

Recent studies suggested p53 mutations as a prognostic factor. Tumors of the esophagus and gastroesophageal (GE) junction show raising incidence with a general poor prognosis.

METHODS

p53 Mutational spectra in 103 patients (68 squamous cell carcinoma/SCC and 35 adenocarcinoma/AC) were compared to clinical and pathologic data.

RESULTS AND CONCLUSIONS

p53 Mutations were found in 26 of 68 SSC (38.2%) and in 12 of 35 AC (34.5%). We only found G > T transversions in smokers with SCC. The survival of patients was not affected by p53 mutational status. In our study, the frequency and mutational spectrum of mutant p53 is similar in both histological types without prognostic relevance.

p53 gene mutations in esophageal squamous cell carcinoma and their relevance to etiology and pathogenesis: results in Japan and comparisons with other countries

Esophageal squamous cell carcinoma is a form of cancer that has varying incidence rates among different countries, distinct geographic areas and different ethnic groups. According to previous reports, p53 gene mutations have been identified in 20-80% of these tumors, and these mutations have occurred at an early stage. These findings suggest that such mutations play an important role in esophageal carcinogenesis, and highlight the importance of mutagens, which cause sequence alterations in the p53 gene. In order to clarify the environmental factors and the molecular mechanisms that may be responsible for the occurrence and prevention of a specific mutation in the process of esophageal carcinogenesis, we analyzed p53 gene mutations in 95 samples of esophageal squamous cell carcinoma. We further reviewed published reports investigating the frequency of p53 gene mutations in esophageal cancer from high-risk areas to normal-risk areas and compared these findings to our results in Japan. The frequency of p53 gene mutations in Japanese esophageal cancer is 47.4% and there are three prominent features: (1) a predominance of transversions, in particular the G:C to T:A transversion; (2) a relatively low frequency of transitions; and (3) a relatively high percentage of frameshift mutations. These results indicate the possible importance of the benzo[a]pyrene metabolite and oxidative DNA damage in esophageal carcinogenesis and scarcely correlate with DNA replication errors or alkylation in comparison to other gastrointestinal cancers. In addition, we observed a peculiar sequence of frameshift mutations. Taken together, these data suggest that this tumor suppressor gene plays a critical role in the multistep carcinogenesis process for esophageal squamous cell cancer.

Regulating the p53 pathway: in vitro hypotheses, in vivo veritas

Mutations in TP53, the gene that encodes the tumour suppressor p53, are found in 50% of human cancers, and increased levels of its negative regulators MDM2 and MDM4 (also known as MDMX) downregulate p53 function in many of the rest. Understanding p53 regulation remains a crucial goal to design broadly applicable anticancer strategies based on this pathway. This Review of in vitro studies, human tumour data and recent mouse models shows that p53 post-translational modifications have modulatory roles, and MDM2 and MDM4 have more profound roles for regulating p53. Importantly, MDM4 emerges as an independent target for drug development, as its inactivation is crucial for full p53 activation.

TP53 and KRAS2 Mutations in Plasma DNA of Healthy Subjects and Subsequent Cancer Occurrence: A Prospective Study

In cancer patients, plasma often contains mutant DNA released by cancer cells. We have assessed the significance of plasma DNA mutations for subsequent cancer development in healthy subjects in a large longitudinal prospective study. The European Prospective Investigation into Cancer and Nutrition study was analyzed with a nested case-control design. Cases were nonsmokers or ex-smokers for >10 years and newly diagnosed with lung, bladder, or upper aerodigestive tract cancers or leukemia accrued after a median follow-up of 6.3 years. Controls were matched 2:1 for follow-up, age, sex, area of recruitment, and smoking status. KRAS2 mutations were detected by mutant-enriched PCR and sequencing (n = 1,098). TP53 mutations were detected by denaturing high-performance liquid chromatography, temporal temperature gradient electrophoresis, and sequencing (n = 550). KRAS2 or TP53 mutations were detected in 13 of 1,098 (1.2%) and 20 of 550 (3.6%) subjects, respectively, 16 of whom developed cancer on average after 18.3 months of follow-up. Among 137 subjects who developed bladder cancer, 5 had KRAS2 mutations [odds ratio (OR), 4.25; 95% confidence interval (95% CI), 1.27-14.15] and 7 had TP53 mutations (OR, 1.81; 95% CI, 0.66-4.97). There was a nonsignificant trend for association between TP53 mutations and bulky adducts in lymphocyte DNA (OR, 2.78; 95% CI, 0.64-12.17). This is the first report of TP53 or KRAS2 mutations in the plasma of healthy subjects in a prospective study, suggesting that KRAS2 mutation is detectable ahead of bladder cancer diagnosis. TP53 mutation may be associated with environmental exposures. These observations have implications for monitoring early steps of carcinogenesis.

Negative implication of C-MYC as an amplification target in esophageal cancer

Chromosomal aberrations (amplifications and deletions) underlie the genesis or development of cancer. Amplification of 8q24 is one of the most frequent events in esophageal cancer. To define whether C-MYC is the target gene for 8q24 amplification, we performed fluorescence in situ hybridization using a MYC (8q24.12 approximately q24.13) probe in esophageal cancer from southern China. Furthermore, we detected the expression status of several genes including C-MYC, TRIB1 (alias C8FW), and FAM84B (alias NSE2) in the regions of 8q24 via reverse transcriptase-polymerase chain reaction or immunohistochemical analysis (or both). Distinct amplification of 8q24 was found in esophageal carcinomas. Only 4 of 46 cases showed obvious protein expression in part of the esophageal cancerous nest. In particular, increased protein expression of C-MYC was shown only in a small part of a cancerous nest in the four cases. Positive C-MYC staining was detected mainly in the cytoplasm of esophageal cancer cells. No expression of TRIB1 was detected in esophageal squamous cell carcinomas. Of 59 cases, 39 (66%) cases showed increased expression of FAM84B in esophageal carcinomas. The results suggest that C-MYC and TRIB1 may not be the amplification target of 8q24 in esophageal cancer. FAM84B might be involved in the genesis or development of esophageal cancer in southern China. Whether FAM84B is the amplification target of esophageal cancer awaits further investigation.

Risk of p53 gene mutation in esophageal squamous cell carcinoma and habit of betel quid chewing in Taiwanese

A recent report suggested that BQ (BQ) chewing significantly correlated with the occurrence of esophageal squamous cell carcinoma (ESCC) in Taiwanese. BQ chewing was shown to be associated with p53 mutation in oral cancers. However, the relationship between BQ chewing and p53 mutation in ESCC is unclear. Seventy-five primary ESCC patients were enrolled for mutational analysis of the p53 gene using polymerase chain amplification and direct sequencing of amplified product. Thirty-seven mutations of the p53 gene were detected in 45.5% (34/75) of tumor specimens. These mutations significantly clustered in exon 5 (21/37) of the p53 gene. The incidence of p53 mutations did not associate with clinicopathological characteristics or the habits of cigarette smoking or alcohol consumption. However, BQ chewers exhibited significantly higher incidence of p53 gene mutations than non-chewers (67.6% vs 32.4%, P = 0.007). After controlling the confounding factors of cigarette smoking and alcohol intake, BQ chewing still showed significant association with the incidence of p53 mutation in ESCCs (RR = 4.23; 95% CI, 1.317-13.60). The A:T to G:C transition (8/37, 21.6%) and G:C to T:A transversion (5/23, 13.5%) were the prevalent spectrum of p53 gene mutations. All A:T to G:C transitional mutations occurred in patients with the habits of BQ chewing and cigarette smoking. Noticeably, alcohol consumption could enhance this peculiar spectrum of p53 mutation in ESCC. Accordingly, p53 might be an important molecular target of BQ carcinogens in the development of ESCC in Taiwanese.

p53 mutation profile of squamous cell carcinomas of the esophagus in Kashmir (India): a high-incidence area

Esophageal squamous cell carcinoma (ESCC) has been reported to show geographical variation in its incidence, even within areas of ethnic homogeneity. Kashmir valley, in north of India, has been described as a high-risk area for ESCC. Here, we make a preliminary attempt to study mutations in exons 5-8 (the DNA binding domain) of the tumor suppressor gene, p53, in 55 ESCC patients from Kashmir. Polymerase chain reaction followed by direct sequencing analysis revealed the presence of mutations in 36.36% (20/55) tumors, assessed for the extent of allelic instability. The 20 mutations, found in 20 patients, comprised of 17 single-base substitutions (11 transitions + 6 transversions) and 3 deletions. The 17 single-base variations represented 12 missense mutations, 2 nonsense mutations and 3 variations located in intron 6, 1 of which resulted in a splicing variant. The patients when compared for the incidence of p53 mutation with various demographic features revealed females to be at increased risk (p = 0.016; OR = 4.13; 95% CI = 1.26-13.46). Comparison of mutation profile with other high-risk areas reflected both differences and similarities indicating coexposure to a unique set of risk factors. This might be due to the special dietary and cultural practices of Kashmir that needs validation, as does the gender-based difference in the incidence of p53 mutation observed in this study.

Human papillomavirus infection in Egyptian esophageal carcinoma: correlation with p53, p21, mdm2, C-erbB2 and impact on survival

The etiological role of human papillomavirus (HPV) in esophageal carcinoma (EC) in relation to p53, mdm2, p21(waf), c-erbB2 and the overall survival (OS) rate was investigated. Tumor and normal tissues from 50 EC were evaluated by polymerase chain reaction and InnoLiPA for HPV. Single strand conformation polymorphism/sequencing were used to detect p53 gene mutations. Immunohistochemistry was performed to determine p53, mdm2, p21(waf)and c-erbB2 expression. Human papillomavirus was detected in 54% of tumors and in 24% of normal tissues. p53, mdm2 and c-erbB2 overexpression was detected in 68%, 70% and 60% of tumors and in 14%, 16% and 10% of normal samples, whereas loss of p21(waf) was evident in 64% of tumors. p53 mutations were detected in 20% of cases. Exon 8 and 5 showed the highest mutation rate (40% each), followed by exons 6 and 7 (10% each). There was a significant correlation between HPV and p53, mdm2, c-erbB2 overexpression. The OS was significantly associated with overexpression of p53 and loss of p21(waf). Human papillomavirus infection is frequent in Egyptian EC. Both p53-dependent and p53-independent pathways seem to be involved in HPV-associated EC. mdm2 and c-erbB2 are possible targets for HPV in the p53-independent pathway. However, only advanced stage and aberrant expression of p53 and p21(waf) are independent prognostic markers.

TP53 mutations as biomarkers for cancer epidemiology in Latin America: current knowledge and perspectives

Due to particular social and economical development, and to the impact of globalization of lifestyles, Latin America shows a superposition of cancers that are frequent in low resource countries (gastric, oesophageal squamous cell and cervical cancers) and high resource countries (cancers of breast, colon and rectum, lung and prostate). Latin America thus offers opportunities for investigating the impact on changing lifestyle patterns on the occurrence of cancer. At the molecular level, mutations in the tumor suppressor gene TP53 are common in many cancers and their distribution can be informative of the nature of the mutagenic mechanisms, thus giving clues to cancer etiology and molecular pathogenesis. However most of the data available are derived from studies in industrialized countries. In this review, we discuss current trends on cancer occurrence in Latin American countries, and we review the literature available on TP53 mutations and polymorphisms in patients from Latin America. Overall, a total of 285 mutations have been described in 1213 patients in 20 publications, representing 1.5% of the total number of mutations reported world-wide. Except for hematological cancers, TP53 mutation frequencies are similar to those reported in other regions of the world. The only tumor site presenting significant differences in mutation pattern as compared to other parts of the world is colon and rectum. However, this difference is based on a single study with 35 patients. Recently, a characteristic TP53 mutation at codon 337 (R337H) has been identified in the germline of children with adrenocortical carcinoma in Southern Brazil. Further and better focused analyses of TP53 mutation patterns in the context of epidemiological studies, should help to improve our understanding of cancer etiology in order to develop appropriate health policies and public health programs in Latin America.

DHPLC is superior to SSCP in screening p53 mutations in esophageal cancer tissues

Mutations of the p53 tumor-suppressor gene universally occur on exons 5-8 in human cancer. We analyzed these mutations in esophageal cancer tissue from 207 patients in China using 2 methods, single-strand conformation polymorphism (SSCP), one of the most frequently used methods, and the recently developed denaturing high-performance liquid chromatography (DHPLC), and compared their sensitivity and efficiency. Exons 5-8 of p53 were amplified from esophageal cancer tissue genomes, screened for fragments of mutations and polymorphisms by SSCP and DHPLC in a blind study and confirmed by direct sequencing to detect the mutations and polymorphisms. The numbers detected by DHPLC were greater than those detected by SSCP, though the rate of mutations and polymorphisms was lower in SSCP than in DHPLC, which appeared to detect smaller mutations (substitutions and 1 bp insertions/deletions). Of the mutations with substitutions detected by DHPLC but not by SSCP, 50% substituted adenosine for other nucleotides, suggesting that these mutations are often missed when SSCP is used. According to these data, the sensitivity of SSCP and DHPLC was 81% and 97%, respectively, and the specificity was 97% and 85%, respectively. Our results suggest that DHPLC may be recommended over SSCP when screening gene mutations. Thus, rates of p53 mutations and polymorphisms in esophageal cancer tissue in Chinese patients were 49% and 41% by DHPLC and SSCP, respectively.

MDM2 gene amplification: a new independent factor of adverse prognosis in non-small cell lung cancer (NSCLC)

The prognostic impact of MDM2 amplification in non-small cell lung cancer (NSCLC) remains unknown. In this study, we investigated the occurrence of MDM2 amplification in surgically treated NSCLC patients. Molecular data were correlated with clinicopathological factors and evaluated for their prognostic value. The study group included 116 NSCLC patients who underwent pulmonary resection between 1996 and 1999. MDM2 amplification was assessed by real-time PCR using hybridization probe format on a LightCycler (Roche). The calculated ratio was a MDM2 value normalized to the amplification of the housekeeping gene phenylalaninhydroxylase (PAH). Survival curves were drawn according to the Kaplan-Meier method and compared with the use of the log-rank test. Multivariate analysis was based on Cox regression analysis. MDM2 amplification was found in 24 patients (21%). There was no relationship between MDM2 amplification and clinicopathological factors, such as sex, age and stage of disease, pT, pN, histology and tumor differentiation. Median disease-free survival (DFS) in patients with and without MDM2 amplification was 3 and 31 months, and 5-year DFS 24 and 33%, respectively (log-rank, P = 0.02). Likewise, median overall survival (OS) in patients with and without MDM2 amplification was 9 and 33 months, respectively, and 5-year OS 24 and 39%, respectively (log-rank, P = 0.01). The strong prognostic relevance of MDM2 amplification for both DFS and OS was confirmed in multivariate analysis (P < 0.01 for both comparisons). Our results suggest that MDM2 gene amplification analysis provides additional prognostic information in surgically treated NSCLC patients.

The p53 network in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide and, despite advances in treatment, still represents a clinical challenge. Inactivation of one or more components of the p53 network is an extremely common event in human neoplasia. In HNSCC, disabling of p53 occurs in a high proportion of cases by mutation in the p53 gene, but other mechanisms of inactivation, such as the presence of human papillomavirus (HPV) and molecular abnormalities in other components of the pathway, are also recognised. The frequent changes occurring in the p53 pathway in HNSCC imply that molecular genetic and immunocytochemical analysis of this critical tumour suppressor network may be of diagnostic and prognostic utility in the clinical management of HNSCC. Further, these changes also provide targets for the development of novel therapeutic approaches to this increasingly common cancer, in which clinical cure for advanced disease remains an elusive goal.

TP53 mutation pattern of esophageal squamous cell carcinomas in a high risk area (Southern Brazil): role of life style factors

In an attempt to correlate the TP53 mutation pattern of squamous cell carcinomas of the esophagus (ESCC) and life style factors of patients from the high risk area Rio Grande do Sul, Brazil, 135 ESCC were analyzed, after prescreening by p53 immunohistochemistry, by SSCP and DNA sequencing of TP53, exon 5-9. Forty-nine somatic TP53 mutations (and 1 case with p53 polymorphism) were identified as missense (n = 39), frameshift (n = 6), silent (n = 1), amber (n = 1) or intron border mutations (n = 2) that cause splicing aberrations. They were preferentially found in exon 5 (36.7%) and exon 8 (32.7%). Several mutations were located in the mutation hot spot codons 248, 273 and 282, mainly at CpG sites. Transition mutations were observed in 53.1% (among them 50% G > A), transversion mutations in 34.7% (among them 47.1% G > T) and frameshifts in 12.2%, the latter 2 mainly in smokers and alcohol drinkers. Transitions were more prevalent in females than in males (p < 0.05). TP53 mutations, mainly transversions, were more frequently found in heavy smokers (p = 0.03), with the same tendency after chronic alcohol consumption. Comparison with the worldwide IARC database disclosed differences in the TP53 mutation pattern of the Brazilian tumors, with a higher accumulation of TP53 mutations in exon 8 and a higher prevalence of transition mutations. Mutations at the reported hot spot codon 176 were missing. Although difficult because of the documented coexposure to various life style risk factors in most patients of this series, the hypothesis is proposed that besides smoking and alcohol drinking the commonly consumed hot mate tea in this high risk area for ESCC is responsible for this different pattern of TP53 mutations because of chronic hyperthermic irritation and inflammation in the esophagus with an endogenous formation of radicals or carcinogenic factors that lead to a higher prevalence of transition mutations.

Relationship of tobacco smoking CYP1A1 GSTM1 gene polymorphism and esophageal cancer in Xi'an

AIM

To analyze the association of tobacco smoking polymorphism of CYP1A1 (7th exon) and GSTM1 genotype and esophageal cancer(EC) in Xi'an.

METHODS

A hospital based case-control study, with molecular epidemiological method, was carried out. Polymorphism of CYP1A1 and GSTM1 of samples from 127 EC cases and 101 controls were detected by PCR method.

RESULTS

There were no significant difference of age and gender between cases and controls. Tobacco smoking was the main risk factor OR=1.97;95% CI=1.12-3.48 for EC in Xi'an. The proportions of CYP1A1 Ile/Ile, Ile/Val and Val/Val gene types in cases and controls was 19.7% 45.7% 34.6% and 30.7%,47.5%, 21.8% respectively(P=0.049). Individuals with CYP1A1 Val/Val genotype compared to those with CYP1A1 Ile/Ile genotype had higher risk for EC increased (OR=2.48, 95%CI=1.12-5.54). The proportions of GSTM1 deletion genotype in cases and controls were 58.3% and 43.6%(OR=1.81, 95%CI=1.03-3.18, P=0.028). Analysis of gene-environment interaction showed that tobacco smoking and CYP1A1 Val/Val genotype; tobacco smoking and GSTM1 deletion genotype had synergism interaction respectively. Analysis of gene-gene interaction did not find synergistic interaction between these two genes. But in GSTM1 deletion group there was significant difference of distribution of CYP1A1 genotype between cases and controls (P=0.011).

CONCLUSION

CYP1A1 Val/Val and GSTM1 deletion genotypes are genetic susceptibility biomarkers for EC. The risk increases, when person with CYP1A1 Val/Val and/or GSTM1 deletion genotype. And these two-metabolic enzymes seem to have interactions with tobacco smoking, in which the mechanism still needs further study.

Distinct pattern of TP53 mutations in squamous cell carcinoma of the esophagus in Iran

Extremely high rates of squamous cell carcinoma of the esophagus (SCCE) are observed in Iran, reflecting unknown, genetic and/or epidemiological risk factors. Among genetic alterations in SCCE, TP53 mutations are the most frequent, vary among populations, and may provide clues on etiological mechanisms. We have analysed mutations in TP53 (exons 5-8) in 98 SCCE from Iran by temporal temperature gel electrophoresis and direct sequencing. We found 58 mutations in 49 patients (50%), with a high prevalence of C to T transitions at CpG dinucleotides (29.3%). The TP53 mutation pattern in Iran was significantly different from that observed in SCCEs from high incidence areas of China and Western Europe (P=0.007). Moreover, the prevalence of mutations at A : T base pairs (transitions and transversions) was higher in men than in women (38.7% vs 11.1%, P=0.033). COX-2 overexpression was detected in 69% of the cases evaluated (24/35), without significant association with TP53 mutation. Accumulation of nitrotyrosine, a marker of protein damage by excess levels of nitric oxide, was observed in tumor cells in six of 18 [corrected] cases analysed. These results are consistent with the hypothesis that several factors are involved in TP53 mutagenesis in Iran. These factors include a baseline of chronic inflammatory stress, which may have a multiplicative impact on the sensitivity of esophageal cells to exogenous factors of risk.

TP53 mutations, amplification of P63 and expression of cell cycle proteins in squamous cell carcinoma of the oesophagus from a low incidence area in Western Europe

In Europe, high incidence rates of oesophageal squamous cell carcinoma (SCCE) are observed in western France (Normandy and Brittany) and in north-eastern Italy. Analysis of TP53 mutations in tumours from these regions has shown a high prevalence of mutations at A:T basepairs that may result from DNA damage caused by specific mutagens. However, the spectrum of TP53 mutations in regions of low incidence is unknown. We report here TP53 mutation analysis in 33 SCCE collected in Lyon, an area of low incidence. These tumours were also examined for MDM2 and P63 amplification, and for expression of p16(INK4a/CDKN2a), cyclin E, p27(Kipl)and Cox2. TP53 mutations were detected in 36% of the cases (12/33). In contrast with regions of high incidence, the mutation spectrum did not show a high prevalence of mutations at A:T base pairs. P63 was amplified in 5/32 cases tested (15.5%). No amplification of MDM2 was found. Expression studies revealed frequent loss of p16(INK4a/CDKN2a)(46%) and p27(Kipl)(25%) expression, and frequent overexpression of Cyclin E (70%) and Cox2 (42%). Overall, these results indicate that in Europe, SCCE from areas of high and low incidence present a similar pattern of molecular alterations but differ by the type of TP53 mutations.