Tumor suppressor genes: at the crossroads of molecular carcinogenesis, molecular epidemiology and human risk assessment

Shared genetic factors and the interactions with fresh fruit intake contributes to four types squamous cell carcinomas

Studies have reported risk factors for a single-squamous cell carcinoma(Single-SCCs). However, the shared common germline genetic factors and environmental factors have not been well elucidated with respect to augmented risk of pan-squamous cell carcinoma(Pan-SCCs). By integrating a large-scale genotype data of 1,928 Pan-SCCs cases and 7,712 age- and sex-matched controls in the UK Biobank cohort, as well as multiple transcriptome and protein databases, we conducted a multi-omics analysis. Genome-wide association analysis (GWAS) was used to identify genetic susceptibility loci of SCCs. High resolution human leucocyte antigen (HLA) alleles and corresponding amino acid sequences were imputed using SNP2HLA and tested for association with SCCs. Credible risk variants (CRVs) were combined risk SNPs reported in GWAS Catalog and our study, followed by comprehensive bioinformatics analyses. We identified six novel index SNPs in the progression of SCCs, which were also strongly interacted with fresh fruit intake. Moreover, our study systematically characterize the HLA variants and their relationship to SCCs susceptibility. We identified HLA-A*01 and six HLA-A amino acid position were associated independently with SCCs. Credible risk variants were annotated to 469 target genes, further GO and KEGG Pathway Enrichment Analysis showed that SCCs genes were primarily involved in immune-related pathways, espechially regulated by HLA region. The transcriptome analysis showed that there were 270 differentially expressed genes(DEGs), with the upregulated genes were enriched in the regulation of stem cell differentiation, proliferation, development, and maintenance. The PPI Network and Modular Analysis uncovered the Keratin(KRT) genes may serve as a potential marker in SCCs. Our results illustrate the molecular basis of both well-studied and new susceptibility loci of SCCs, providing not only novel insights into the genetic commonality among SCCs but also a set of plausible gene targets for post-GWAS functional experiments.

p53 immunostaining pattern is a useful surrogate marker for TP53 gene mutations

BACKGROUND

TP53 is the most frequently mutated gene in the human cancer, and the awareness of its mutational status is useful in the diagnosis and treatment of cancer patients. In the present study, we investigated the association between TP53 gene mutations and p53 immunohistochemical staining (IHC) patterns and non-genetic effect of MDM2 as a negative regulator of p53.

METHODS

A total of 135 solid cancer cases with next generation sequencing data were subjected to p53 IHC and classified as overexpression, null type or usual pattern.

RESULTS

TP53 mutation was observed in 104 out of 135 cases (77.0%). When the TP53 mutations were annotated into DISRUPTED (truncations, frameshifts, splice site mutations, and deep deletions) and IF-DBD (in-frame mutations in the DNA binding domain), the null type p53 IHC pattern was associated with DISRUPTED mutations (sensitivity 86.2%, specificity 97.2%) while the overexpression pattern was associated with IF-DBD mutations (sensitivity 100%, specificity 81.7%). The specificity of p53 IHC usual pattern predicting wild type TP53 was also as high as 100%. Regardless of MDM2 amplification, p53 IHC pattern showed a perfect association with TP53 mutation pattern.

CONCLUSIONS

p53 IHC pattern (overexpression, null type, usual) reasonably predicted TP53 mutational status (DISRUPTED, IF-DBD), and MDM2 amplification status did not have any impact on the p53 IHC pattern.

Targeting HSP90 Inhibits Proliferation and Induces Apoptosis Through AKT1/ERK Pathway in Lung Cancer

Lung cancer is one of the most common malignant cancers worldwide. Searching for specific cancer targets and developing efficient therapies with lower toxicity is urgently needed. HPS90 is a key chaperon protein that has multiple client proteins involved in the development of cancer. In this study, we investigated the transcriptional levels of HSP90 isoforms in cancerous and normal tissues of lung cancer patients in multiple datasets. The higher expression of HSP90AA1 in cancer tissues correlated with poorer overall survival was observed. The higher levels of transcription and expression of HSP90AA1 and the activity of AKT1/ERK pathways were confirmed in lung cancer patient tissues. In both human and mouse lung cancer cell lines, knocking down HSP90AA1 promoted cell apoptosis through the inhibition of the pro-survival effect of AKT1 by decreasing the phosphorylation of itself and its downstream factors of mTOR and BAD, as well as downregulating Mcl1, Bcl-xl, and Survivin. The knockdown also suppressed lung cancer cell proliferation by inhibiting ERK activation and downregulating CyclinD1 expression. The treatment of 17-DMAG, an HSP90 inhibitor, recaptured these effects in vitro and inhibited tumor cell growth, and induced apoptosis without obvious side effects in lung tumor xenograft mouse models. This study suggests that targeting HSP90 by 17-DMAG could be a potential therapy for the treatment of lung cancer.

Title- Genomic landscape of squamous cell carcinoma- Different genetic pathways culminating in a common phenotype

INTRODUCTION

Squamous cell carcinomas (SqCCs) are the most common solid tumors in humans and are found across multiple organ systems. Although, integrated analysis of genetic alterations divulge similarities between SqCCs from various body sites, certain genes appear to be more frequently mutated in a given SqCC. These subtle differences may hold the key to determining the differentiation characteristics and predicting aggressiveness of tumors.

MATERIALS AND METHOD

Fifty-four cases of SqCCs, in which the primary location of the tumor could be ascertained by clinical and radiological findings, were included in this study. Next generation sequencing data was analyzed for recurrent genetic abnormalities.

RESULTS

Genetic alterations were found in 219 genes in the 54 cases studied. TP53 mutations were found to be more frequent in pulmonary SqCCs (86.5%) as compared to non-pulmonary SqCCs (58.8%) (p<0.05). NOTCH gene family mutations and CREBBP mutations were limited to non-pulmonary SqCC (p<0.005) and were mutated in 41.2% and 17.6% cases.

CONCLUSION

A detailed comparative analysis of the genetic alterations identified by sequencing identified higher frequency of TP53 mutations in lung SqCCs as compared to non-pulmonary SqCCs. NOTCH and CREBPP mutations were found to be absent in lung and head and neck SqCCs and more frequent in SqCCs from other locations.

Differences in molecular epidemiology of lung cancer among ethnicities (Asian vs. Caucasian)

Background

Differences in carcinogenesis and therapeutic efficacy according to ethnicity have been reported for lung cancer, and understanding differences in genetic mutation profiles among ethnicities is important for interpreting the results of clinical trials, preventing carcinogenesis, and individualizing treatment. However, no studies have focused on differences in mutation profiles among different ethnicities using large-scale genomic analysis data with detailed information on smoking history, the main cause of lung cancer.

Methods

To clarify the differences in genetic mutation profiles between Caucasian and Japanese subjects, we compared data from The Cancer Genome Atlas, which mainly included Caucasians, with results from the Japan Molecular Epidemiology for lung cancer study, which is an epidemiological study only involving Japanese subjects. We divided the participants into four groups according to smoking status and performed comparative analysis by tissue type (lung adenocarcinoma and squamous cell lung cancer).

Results

In patients with lung adenocarcinoma, the frequency of EGFR mutations was lower in Caucasian subjects than in Japanese subjects (14.6% vs. 51.1%), whereas the frequencies of mutations in other genes, namely KRAS (32.9% vs. 9.3%), TP53 (45.2% vs. 20.7%), BRAF (9.6% vs. 1.3%), PIK3CA (5.9% vs. 2.6%), KEAP1 (17.8% vs. 0.5%), NF1 (10.9% vs. 0.5%), STK11 (17.8% vs. 0.7%), RBM10 (8.7% vs. 0.1%), and MET (7.8% vs. 0.1%), were higher in Caucasian subjects. Among patients with squamous cell carcinoma, TP53 (81.2% vs. 49.1%), PIK3CA (14.5% vs. 6.8%), KEAP1 (12.7% vs. 0.9%), and NFE2L2 mutations (15.8% vs. 13.6%) were more common in Caucasian subjects.

Conclusions

Ethnicity is an important and complex characteristic that must be recognized and considered, even in the era of precision medicine. We should collaborate to share data for different ethnicities and incorporate them into clinical practice and the design of global clinical studies. Carefully designed molecular epidemiological studies focusing on ethnic differences are warranted.

Squamous Cell Cancers: A Unified Perspective on Biology and Genetics

Squamous cell carcinomas (SCCs) represent the most frequent human solid tumors and are a major cause of cancer mortality. These highly heterogeneous tumors arise from closely interconnected epithelial cell populations with intrinsic self-renewal potential inversely related to the stratified differentiation program. SCCs can also originate from simple or pseudo-stratified epithelia through activation of quiescent cells and/or a switch in cell-fate determination. Here, we focus on specific determinants implicated in the development of SCCs by recent large-scale genomic, genetic, and epigenetic studies, and complementary functional analysis. The evidence indicates that SCCs from various body sites, while clinically treated as separate entities, have common determinants, pointing to a unified perspective of the disease and potential new avenues for prevention and treatment.

Mutation screening of the TP53 gene by temporal temperature gel electrophoresis (TTGE)

A protocol for detection of mutations in the TP53 gene using temporal temperature gradient electrophoresis (TTGE) is described. TTGE is a mutation detection technique that separates DNA fragments differing by single base pairs according to their melting properties in a denaturing gel. It is based on constant denaturing conditions in the gel combined with a temperature gradient during the electrophoretic run. This method combines some of the advantages of the related techniques, denaturing gradient gel electrophoresis and constant denaturant gel electrophoresis, and eliminates some of the problems. The result is a rapid and sensitive screening technique which is robust and easily set up in smaller laboratory environments.

Promoter hypermethylation of p73 and p53 genes in cervical cancer patients among north Indian population

Hypermethylation of CpG islands leads to transcriptional silencing and it is the predominant mechanism of tumor suppressor gene inactivation in many tumors. Methylation-specific polymerase chain reaction was performed to analyse the methylation status of the promoter region of the tumor suppressor genes. Hypermethylation of the 5' CpG island of the p21 ( CIP1 ), p27 ( KIP1 ), p57 ( KIP2 ), p53, p73 and RB 1 gene promoter were found in 8.8, 8.8, 11.2, 12, 25.6 and 4.8 % of 125 cervical cancer samples from north Indian population, respectively. Methylation of p73 was significantly (P < 0.001) associated with the cervical cancer cases in comparison to controls. Significant correlation was also observed between the methylation of p73 gene and increase in the risk of cervical cancer among passive smokers. Promoter hypermethylation of p53 gene was also observed to be significant among oral contraceptive users and cervical cancer patients having age at first sexual intercourse <20 years whereas hypermethylation of other genes was not found to be significant in the present study. This is the first report showing significant hypermethylation of p73 and p53 genes among cervical cancer patients in north Indian population. This is also the first report on significant p53 hypermethylation in cervical cancer in any population. Our findings did not show any correlation between promoter methylation of p73 and the other genes under study with clinicopathological parameters, including human papillomavirus infection and stage of the disease. The frequency of aberrant methylation of p73 and p53 gene promoter was unchanged according to the age of patients.

Immunohistochemical staining patterns of p53 can serve as a surrogate marker for TP53 mutations in ovarian carcinoma: an immunohistochemical and nucleotide sequencing analysis

Immunohistochemical staining for p53 is used as a surrogate for mutational analysis in the diagnostic workup of carcinomas of multiple sites including ovarian cancers. Strong and diffuse immunoexpression of p53 is generally interpreted as likely indicating a TP53 gene mutation. The immunoprofile that correlates with wild-type TP53, however, is not as clear. In particular, the significance of completely negative immunostaining is controversial. The aim of this study was to clarify the relationship of the immunohistochemical expression of p53 with the mutational status of the TP53 gene in ovarian cancer. A total of 57 ovarian carcinomas (43 high-grade serous ovarian/peritoneal carcinomas, 2 malignant mesodermal mixed tumors (carcinosarcomas), 2 low-grade serous carcinomas, 4 clear cell carcinomas, 1 well-differentiated endometrioid carcinoma, and 5 carcinomas with mixed epithelial differentiation) were analyzed for TP53 mutations by nucleotide sequencing (exons 4-9), and subjected to immunohistochemical analysis of p53 expression. Thirty six tumors contained functional mutations and 13 had wild type TP53. Five tumors were found to harbor known TP53 polymorphism and changes in the intron region were detected in three. Tumors with wild-type TP53 displayed a wide range of immunolabeling patterns, with the most common pattern showing ≤10% of positive cells in 6 cases (46%). Mutant TP53 was associated with 60-100% positive cells in 23 cases (64% of cases). This pattern of staining was also seen in three cases with wild-type TP53. Tumors that were completely negative (0% cells staining) had a mutation of TP53 in 65% of cases and wild-type TP53 in 11%. Combining two immunohistochemical labeling patterns associated with TP53 mutations (0% and 60-100% positive cells), correctly identified a mutation in 94% of cases (P<0.001). Immunohistochemical analysis can be used as a robust method for inferring the presence of a TP53 mutation in ovarian carcinomas. In addition to a strong and diffuse pattern of p53 expression (in greater than 60% of cells), complete absence of p53 immunoexpression is commonly associated with a TP53 mutation. Accordingly, this latter pattern, unlike low-level expression (10-50% cells), should not be construed as indicative of wild-type TP53.

Estrogen-induced reactive oxygen species-mediated signalings contribute to breast cancer

Elevated lifetime estrogen exposure is a major risk factor for breast cancer. Recent advances in the understanding of breast carcinogenesis clearly indicate that induction of estrogen receptor (ER) mediated signaling is not sufficient for the development of breast cancer. The underlying mechanisms of breast susceptibility to estrogen's carcinogenic effect remain elusive. Physiologically achievable concentrations of estrogen or estrogen metabolites have been shown to generate reactive oxygen species (ROS). Recent data implicated that these ROS induced DNA synthesis, increased phosphorylation of kinases, and activated transcription factors, e.g., AP-1, NRF1, E2F, NF-kB and CREB of non-genomic pathways which are responsive to both oxidants and estrogen. Estrogen-induced ROS by increasing genomic instability and by transducing signal through influencing redox sensitive transcription factors play important role (s) in cell transformation, cell cycle, migration and invasion of the breast cancer. The present review discusses emerging data in support of the role of estrogen induced ROS-mediated signaling pathways which may contribute in the development of breast cancer. It is envisioned that estrogen induced ROS mediated signaling is a key complementary mechanism that drives the carcinogenesis process. ROS mediated signaling however occurs in the context of other estrogen induced processes such as ER-mediated signaling and estrogen reactive metabolite-associated genotoxicity. Importantly, estrogen-induced ROS can function as independent reversible modifiers of phosphatases and activate kinases to trigger the transcription factors of downstream target genes which participate in cancer progression.

p53 mutations as fingerprints for aristolochic acid: an environmental carcinogen in endemic (Balkan) nephropathy

The activation of protooncogenes and inactivation of tumor suppressor genes are considered to be the main molecular events in the multistep process of carcinogenesis. Mutations of the TP53 tumor suppressor gene have been found in nearly all tumor types and are estimated to contribute to more than 50% of all cancers. Most mutations lead to the synthesis of highly stable, inactive proteins that accumulate in the nucleus of cancer cells. Among the 393 codons of the human p53 gene, 222 are targets of 698 different types of mutations. Alterations of codons 175, 248, 273 and 282 correspond to 19% of all mutations and are considered general hot spot mutations. Dietary exposure to aristolochic acid (AA), an established nephrotoxin and human carcinogen found in all Aristolochia species was shown to be the causative agent of aristolochic acid nephropathy (previously called Chinese herbs nephropathy). This syndrome is characterized by proximal tubular damage, renal interstitial fibrosis, slow progression to the end stage renal disease and a high prevalence of upper urinary tract urothelial carcinoma (otherwise a highly unusual location). AA preferentially binds to purines in DNA and is associated with a high frequency of A-->T transversions in the p53 gene. Rats treated with AA develop A:T-->T:A mutations in codon 61. The pathological and clinical features of endemic (Balkan) nephropathy closely resemble those associated with aristolochic acid nephropathy except for the slower progression to end stage renal disease and longer cumulative period before the appearance of urothelial cancer. Recently, we reported the presence of AA-DNA adducts in renal cortex and A-->T p53 mutations in tumor tissue of patients from Croatia and Bosnia with endemic nephropathy. These data support the hypothesis that dietary exposure to AA is a major risk factor for endemic (Balkan) nephropathy.

Determinants of protein function revealed by combinatorial entropy optimization

We use a new algorithm (combinatorial entropy optimization [CEO]) to identify specificity residues and functional subfamilies in sets of proteins related by evolution. Specificity residues are conserved within a subfamily but differ between subfamilies, and they typically encode functional diversity. We obtain good agreement between predicted specificity residues and experimentally known functional residues in protein interfaces. Such predicted functional determinants are useful for interpreting the functional consequences of mutations in natural evolution and disease.

Tat peptide-mediated intracellular delivery of pharmaceutical nanocarriers

Cell-penetrating peptides (CPPs) including TAT peptide (TATp) have been successfully used for intracellular delivery of a broad variety of cargoes including various nanoparticulate pharmaceutical carriers (liposomes, micelles, nanoparticles). Here, we will consider the main results in this area, with a special emphasis on TATp-mediated delivery of liposomes and DNA. We will also address the development of "smart" stimuli-sensitive nanocarriers, where cell-penetrating function can be activated by the decreased pH only inside the biological target minimizing thus the interaction of drug-loaded nanocarriers with non-target cells.

Aberrant p16 promoter methylation among Greek lung cancer patients and smokers: correlation with smoking

Genetic and environmental factors (dietary and smoking) influence lung cancer epidemiology and induce epigenetic modifications that should be assessed in individual populations. We analyzed p16 methylation among Greek non-small cell lung carcinoma patients and smokers using two-stage methylation-specific polymerase chain reaction. One hundred and fifty specimens from cancerous and adjacent non-cancerous tissue, bronchial washings and sputum from patients and 48 specimens, mostly sputum, from disease-free smokers were included. p16 methylation was very frequent in biopsies (82.85%) and bronchial washings (non-small cell lung carcinoma, 80.35%; small cell lung carcinoma, 16.66%) from patients, but also in adjacent non-cancerous tissue (45.71%). Concordance of p16 methylation and positivity by cytological examination was 51.78%. Methylation was also observed in sputum from asymptomatic cytology-negative smokers (22.5%) and chronic obstructive pulmonary disease patients (three of eight). Among disease-free individuals, methylation correlated only with heavy smoking (>50 pack-years, P<0.001) and differed among male and female disease-free smokers. In summary, p16 methylation is very frequent among non-small cell lung carcinoma patients, and correlates with heavy cigarette consumption only in disease-free smokers.

TP53 mutations and hepatocellular carcinoma: insights into the etiology and pathogenesis of liver cancer

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and the major risk factors include chronic infections with the hepatitis B (HBV) or C (HCV) virus, and exposure to dietary aflatoxin B(1) (AFB(1)) or alcohol consumption. Multiple genetic and epigenetic changes are involved in the molecular pathogenesis of HCC, for example, somatic mutations in the p53 tumor suppressor gene (TP53) and the activation of the WNT signal transduction pathway. AFB(1) frequently induces G:C to T:A transversions at the third base in codon 249 of TP53 and cooperates with HBV in causing p53 mutations in HCC. The detection of TP53 mutant DNA in plasma is a biomarker of both AFB(1) exposure and HCC risk. Chronic infection with HBV and HCV viruses, and oxyradical disorders including hemochromatosis, also generate reactive oxygen/nitrogen species that can both damage DNA and mutate cancer-related genes such as TP53. Certain mutant p53 proteins may exhibit a 'gain of oncogenic function'. The p53 biological network is a key responder to this oxidative and nitrosative stress. Depending on the extent of the DNA damage, p53 regulates the transcription of protective antioxidant genes and with extensive DNA damage, transactivates pro-oxidant genes that contribute to apoptosis. The X gene of HBV (HBx) is the most common open reading frame integrated into the host genome in HCC and the integrated HBx is frequently mutated. Mutant HBx proteins still retain their ability to bind to p53, and attenuate DNA repair and p53-mediated apoptosis. In summary, both viruses and chemicals are implicated in the etiology of TP53 mutations during the molecular pathogenesis of HCC.

Dextran sodium sulfate strongly promotes colorectal carcinogenesis in Apc(Min/+) mice: inflammatory stimuli by dextran sodium sulfate results in development of multiple colonic neoplasms

The mouse model for familial adenomatous polyposis, Apc(Min/+) mouse, contains a truncating mutation in the Apc gene and spontaneously develops numerous adenomas in the small intestine but few in the large bowel. Our study investigated whether dextran sodium sulfate (DSS) treatment promotes the development of colonic neoplasms in Apc(Min/+) mice. Apc(Min/+) and Apc+/+ mice of both sexes were exposed to 2% dextran sodium sulfate in drinking water for 7 days, followed by no further treatment for 4 weeks. Immunohistochemistry for cyclooxygenase-2, inducible nitric oxide synthase, beta-catenin, p53, and nitrotyrosine, and mutations of beta-catenin and K-ras and loss of wild-type allele of the Apc gene in the colonic lesions were examined. Sequential observation of female Apc(Min/+) mice that received DSS was also performed up to week 5. At week 5, numerous colonic neoplasms developed in male and female Apc(Min/+) mice but did not develop in Apc+/+ mice. Adenocarcinomas developed in Apc(Min/+) mice that received DSS showed loss of heterozygosity of Apc and no mutations in the beta-catenin and K-ras genes. The treatment also significantly increased the number of small intestinal polyps. Sequential observation revealed increase in the incidences of colonic neoplasms and dysplastic crypts in female Apc(Min/+) mice given DSS. DSS treatment increased inflammation scores, associated with high intensity staining of beta-catenin, cyclooxygenase-2, inducible nitric oxide synthase and nitrotyrosine. Interestingly, strong nuclear staining of p53 was specifically observed in colonic lesions of Apc(Min/+) mice treated with DSS. Our results suggest a strong promotion effect of DSS in the intestinal carcinogenesis of Apc(Min/+) mice. The findings also suggest that strong oxidative/nitrosative stress caused by DSS-induced inflammation may contribute to the colonic neoplasms development.

Non-CpG cytosine methylation of p53 exon 5 in non-small cell lung carcinoma

Non-CpG methylation of cytosine residues, a mechanism associated with regulation of gene expression, has not been investigated in human cancer until now. Analysis of the p53 exon 5 mutation spectrum in mutation databases for lung cancer reveals frequent GC>AT transitions, several of which occur at non-CpG sequences. To investigate the involvement of cytosine methylation in this mutagenesis process, we analyzed the methylation profile of p53 exon 5, in lung carcinoma. In this report, we present evidence that extensive clustered non-CpG methylation is observed in three regions of this exon, namely the sequences spanning codons 156-159, 175-179 and the 3' splice site, as well as in scattered CpA sequences. This methylation pattern was verified using direct methylation sequencing, and a two-stage methylation-specific PCR assay (MSP), designed for the detection of methylation in a GC rich region (oligo C sequence, of codons 175-179) of exon 5. The results from this MSP assay reveal that DNA from cancerous specimens was more heavily methylated in non-CpG cytosines, compared to that from non-cancerous lung tissue of cancer patients (14/19 cancerous and 6/19 non-cancerous, respectively). DNA isolated from human leucocytes and some non-cancerous specimens (2/19) was free of non-CpG methylation. Careful analysis of the mutations reported in p53 mutation databases also provides corroborating evidence that the high incidence of GC>AT mutations in the p53 gene, observed in lung cancer, might also be related to non-CpG methylation, as well as to the overall increase of methylation sites in this locus.

p53 Mutations in human cholangiocarcinoma: a review

The reported mortality from intrahepatic bile duct tumours is increasing markedly in industrialised countries, for reasons that remain unknown. Inactivation of the tumour suppressor gene p53, is the commonest genetic abnormality in human cancer and has been implicated in the genesis of cholangiocarcinoma in various immunohistochemical and molecular epidemiological investigations, including gene sequencing studies. The structure and function of p53 and its role in linking cancer to specific carcinogens by way of mutational signatures is reviewed. The findings of previous p53 studies and their relevance in human cholangiocarcinoma are summarised.

Familial multiple primary lung cancers: a population-based analysis from Sweden

Multiple primary cancers arise because of inherited or acquired deficiencies, and their causes may depend on the first primary cancer, or they may be entirely independent. We used a nation-wide family dataset to search for evidence for a genetic predisposition to lung cancer. The Swedish Family-Cancer Database includes all Swedes born in 1932 and later with their parents, totalling over 10.2 million individuals. Cancer cases were retrieved from the Swedish Cancer Registry up to year 2000. Standardized incidence ratios (SIR) and 95% confidence limits (CI) were calculated for first and second primary lung cancers by a family history. The incidence of second primary lung cancer was nine times higher among cases with familial lung cancer compare to that of first primary lung cancer. The proportion of multiple primary lung cancer patients with family history for lung cancer was 4.7% (9/190) for men and 6.5% (5/77) for women. Lung cancer patients with a family history of lung cancer were at a significantly increased risk for subsequent primary lung cancer among both men (SIR=9.89, 95%CI 4.48-18.66) and women (SIR=17.86, 95%CI 5.63-42.00). The corresponding SIRs in patients without a family history were 2.04 (95%CI 1.75-2.36) and 5.10 (95%CI 3.99-6.43) for men and women, respectively. The present study suggests that the development from the first primary lung cancer to the second primary lung cancer may be more strongly affected by genetic factor than the first primary lung cancer.

The PI3K inhibitor LY294002 prevents p53 induction by DNA damage and attenuates chemotherapy-induced apoptosis

The p53 tumor suppressor plays a key role in the natural protection against cancer. Activation of p53 by DNA-damaging agents can contribute to successful elimination of cancer cells via chemotherapy-induced apoptosis. The phosphatidylinositol-3 kinase (PI3K) pathway, triggered in normal cells upon exposure to growth factors, regulates a cascade of proliferation and survival signals. The PI3K pathway is abnormally active in many cancers, thus making it an attractive target for inactivation in an attempt to achieve better cancer therapy. We report here that exposure to LY294002, a potent PI3K inhibitor, aborts the activation of p53 by several drugs commonly used in cancer chemotherapy. Concomitantly, LY294002 attenuates p53-dependent, chemotherapy-induced apoptosis of cancer cells. These findings invoke an unexpected positive role for PI3K in p53 activation by anticancer agents, and suggest that the efficacy of PI3K inhibitors in cancer therapy may be greatly affected by the tumor p53 status.

High frequency of frameshift mutation on p53 gene in Taiwanese with non small cell lung cancer

Extensive researches have found that the mutation of p53 tumor suppressor gene is the most frequent event in many human cancers and associated with a poor clinical outcome in lung cancer patients. Because the p53 molecular mutation involved in tumorigenesis of patients with lung cancer in Taiwan remains poorly defined, the aim of this study was to assess the p53 mutation spectrum and possible etiological factors of Taiwan's patients with Non-Small Cell Lung Cancer (NSCLC). Cancer specimens were obtained surgically from 61 patients with pathologically proven NSCLC. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and direct sequencing were used to study p53 mutations in exon 4-8. We also performed immunohistochemistry (IHC) to detect p53 protein expression. Our results provided that 34 mutations of p53 gene were found in 27 cases with a mutation rate of 44% (27/61). There were six cases having more than two p53 mutations. Among the 34 mutations, 19 were point mutations (56%, 19/34) consisted of a majority of missense mutations including transversion (13/19, 68%) and transitions (6/19, 32%) with four cases (4/6, 67%) occurring in the CpG sequence. One of the most important finding in our study was the high frequency of frameshift (44%, 15/34) which included 11 insertions and 4 deletions of p53 in NSCLC in Taiwan. Surprisingly, our results disclosed distinct novel mutations at codon 181, 185, 208 (Exon 5-6) of p53. Especially, 4 cases with mutation at codon181 and codon 185 seemed to have more advanced clinical outcome with survival time less than 6 months. In addition, there were two recurring mutations at codon 168 and three at condon193. The different mutation spectrum in our series, including a high frequency of frameshift mutations and distinctly novel hot spots suggested the heterogenous entity of exogenous mutagens in NSCLC in Taiwan.

Influence of GSTM1, GSTT1, GSTP1 and NAT2 genotypes on the p53 mutational spectrum in bladder tumours

Genetic polymorphisms affecting expression or activity of the corresponding enzymes can influence the risk of acquiring gene mutations and various cancers. We have studied 327 bladder cancer patients with regard to the functionally related polymorphisms of GSTM1, GSTT1, GSTP1 and NAT2 and analysed the p53 mutational status of their tumours. Fifty p53 mutations, 26% transversions and 74% transitions, were detected in 44 patients. P53 mutation frequency was significantly higher in higher-grade tumours than in low-grade tumours (OR = 2.09, 95% CI 1.44-3.02, adjusted for age and sex). Also, a significant association was found between tumour stage (Tis and T2+ vs. Ta and T1) and presence of the GSTP1 val allele (adjusted OR = 2.00, CI 1.14-3.52). Overall, there was no significant difference in frequency of p53 mutation among patients with different genotypes. Among patients with p53 mutation, transversions were significantly more frequent in GSTM1-negative as compared to GSTM1-positive individuals (OR = 5.18, CI 1.07-25.02, adjusted for age, sex and tumour stage). With one exception, all tumours with the most common type of transversion, G:C-C:G, occurred in GSTM1-negative patients. Among smokers, all transversions (3 of 3), but only 2 of 13 transitions, were found among carriers of the GSTP1 variant allele, and samples carrying at least 1 variant GSTP1 allele had more transitions at CpG sites than wild-type samples (adjusted OR = 4.61, CI 0.82-26.04). No significant associations were found for the NAT2 gene. Our results suggest that impaired glutathione conjugation may affect the mutation spectrum in critical target genes.

Association of habitual smoking and drinking with single nucleotide polymorphism (SNP) in 40 candidate genes: data from random population-based Japanese samples

Basic information on the association between lifestyle factors and candidate genes is valuable for genetic-environmental study. We screened the association of habitual smoking or drinking with polymorphism in 40 candidate genes for a total of 153 single nucleotide polymorphisms (SNPs) using a sample of 339 middle-aged, randomly selected Japanese men. Smoking and drinking statuses were elicited during questionnaire-based interviews. Genes were selected based on their possible involvement in genetic-environmental, life-style interactions and constitute the genes expressing xenobiotic metabolism enzymes, DNA repair enzymes, and other stress-related proteins. The P values of odds ratios to habitual smoking for CYP17A1, ESR1, EPHX1, GSTT2, ALDH2, NOS2A, OGG1, and SLC6A4 and those of odds ratios to habitual drinking for CYP1B1, ESR1, HSD17B3, GSTM3, COMT, ADH1C, ALDH2, NOS3, and NUDT1 were under 0.05. These variables were included in a stepwise logistic analysis in order to develop a predictive model for smoking or drinking behavior. In the final model, the only significant variables selected for smoking were OGG1, SLC6A4, EPHX1, ESR1, and CYP17A1, and for drinking, ALDH2 and NUDT1. The findings of the present study suggest that polymorphism in associated candidate genes plays a role in the habitual use of tobacco and alcohol among Japanese men.

Inherited predisposition to early onset lung cancer according to histological type

The role of hereditary factors in lung cancer is less well understood than in many other human neoplastic diseases. We used a nation-wide family dataset to search for evidence for a genetic predisposition in lung cancer. The Swedish Family-Cancer Database includes all Swedes born in 1932 and later (0- to 68-year-old offspring) with their parents, totaling over 10.2 million individuals. Cancer cases were retrieved from the Swedish Cancer Registry up to year 2000. Standardized incidence ratios (SIR) and 95% confidence limits (CI) were calculated for age-specific familial risks in offspring by parental or sibling proband, separately. A Kappa test was used to examine the association between familial risk and histology. Compared to the rate of lung cancers among persons without family history, a high risk by parental family history in adenocarcinoma (2.03) and large cell carcinoma (2.14) was found, and only a slightly lower risk was found among patients with squamous cell carcinoma (1.63) and small cell carcinoma (1.55). Among siblings, an increased risk was shown for concordant adenocarcinoma and small cell carcinoma at all ages and for all histological types when cancer was diagnosed before age 50. At young age, risks between siblings were higher than those between offspring and parents. The present data suggest that a large proportion of lung cancers before age 50 years appears to be heritable and probably due to a high-penetrant recessive gene or genes that predispose to tobacco carcinogens; however, this hypothesis needs to be tested in segregation analysis with a large number of pedigrees.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Dietary cancer and prevention using antimutagens

Many of the cancers common in the Western world, including colon, prostate and breast cancers, are thought to relate to dietary habits. Of the known risk factors, many will act through increasing the probability of mutation. Recognised dietary mutagens include cooked meat compounds, N-nitroso compounds and fungal toxins, while high meat and saturated fat consumption, increasing rates of obesity, and regular consumption of alcohol and tobacco are all dietary trends that could indirectly enhance the probability of mutation. However, there are significant difficulties in implementing and sustaining major dietary changes necessary to reduce the population's intake of dietary mutagens. Dietary antimutagens may provide a means of slowing progression toward cancer, and be more acceptable to the population. Consideration of genetic mechanisms in cancer development suggest several distinct targets for intervention. Strategies that reduce mutagen uptake may be the most simple intervention, and the one least likely to result in undesirable side effects. Certain (but not all) types of dietary fibres appear to reduce mutation through this mechanism, as may certain probiotics and large planar molecules such as chlorophyllin. Antioxidants have been suggested to scavenge free radicals, and prevent their interactions with cellular DNA. Small molecule dietary antioxidants include ascorbic acid, Vitamin E, glutathione, various polyphenols and carotenoids. We found a statistically significant relationship between colon cancer incidence and soil selenium status across different regions of New Zealand. Additionally, a study of middle-aged men suggested that blood selenium levels lower than 100 ng/ml were inadequate for repair or surveillance of oxidative (and other) DNA damage. We suggest that selenium will be an important antimutagen, at least in New Zealand, possibly through antioxidant effects associated with selenium's role in enzymes associated with endogenous repair of DNA damage. Modulation of xenobiotic metabolizing enzymes is well recognised as cancer-protective, and is a property of various flavonoids and a number of sulfur-containing compounds. Many fruits and vegetables contain compounds that will protect against mutation and cancer by several mechanisms. For example, kiwifruit has antioxidant effects and may also affect DNA repair enzymes. Dietary folate may be a key factor in maintenance of methylation status, while enhanced overall levels of vitamins and minerals may retard the development of genomic instability. The combination of each of these factors could provide a sustainable intervention that might usefully delay the development of cancer in New Zealand and other populations. Although there are a range of potentially antimutagenic fruits, vegetables and cereals available to these populations, current intake is generally below the level necessary to protect from dietary or endogenous mutagens. Dietary supplementation may provide an alternative approach.

Attenuation of the p53 response to DNA damage by high cell density

The p53 tumor suppressor is critical for preventing cancer progression. Numerous observations suggest that p53 function can be modulated by the cells' microenvironment. We addressed specifically the impact of cell crowding on the induction of p53 by DNA damage. We report that cell crowding attenuates markedly p53 upregulation, transcriptional activation and subsequent p53-dependent apoptosis following exposure to genotoxic stress. The p53 protein remains short-lived in confluent cultures regardless of the extent of DNA damage, even though it undergoes efficient phosphorylation on the mouse equivalent of human p53 serine 15. This inhibitory effect of cell crowding is not a secondary consequence of density-dependent cell cycle arrest (contact inhibition). Microscopic examination indicates that dense cultures display prominent cadherin-mediated cell-cell junctions, and only poor cell-matrix focal adhesions, whereas sparse cells possess conspicuous matrix adhesions and essentially no cell-cell contacts. High-density cell culture might recapitulate the microenvironment of cells in a living organism, where the response of p53 to DNA damage is reported to be low in some organs and ages. The impact of cell density on p53 activation may have important bearings on the involvement of p53 in tumor suppression and the cellular response to anticancer therapy.

Inhibition of mutant p53 expression and growth of DMS-153 small cell lung carcinoma by antagonists of growth hormone-releasing hormone and bombesin

We investigated the effects of growth hormone-releasing hormone (GHRH) antagonists, JV-1-65 and JV-1-63, and bombesin/gastrin-releasing peptide (BN/GRP) antagonist RC-3940-II on DMS-153 human small cell lung carcinoma xenografted into nude mice. Treatment with 10 microg/day JV-1-65 or RC-3940-II decreased tumor volume by 28% (P < 0.05) and 77% (P < 0.01), respectively, after 42 days compared with controls. Combination of JV-1-65 and RC-3940-II induced the greatest inhibition of tumor proliferation (95%; P < 0.01), suggesting a synergism. Western blotting showed that the antitumor effects of these antagonists were associated with inhibition of the expression of the mutant tumor suppressor protein p53 (Tp53). Mutation was detected by sequence analysis of the p53 gene at codon 155: ACC [Thr] --> CCC [Pro]. Combination of JV-1-65 and RC-3940-II decreased the levels of mutant p53 protein by 42% (P < 0.01) compared with controls. JV-1-65, JV-1-63, and RC-3940-II, given singly, reduced mutant p53 protein expression by 18-24% (P < 0.05). Serum insulin-like growth factor (IGF)-I levels were diminished in animals receiving GHRH antagonists. mRNA levels for IGF-II, IGF receptor-I, GRP receptor, and EGF receptor in tumors were significantly decreased by combined treatment with JV-1-65 and RC-3940-II. DMS-153 tumors expressed mRNAs for GHRH and GHRH receptor splice variants 1 and 2, suggesting that GHRH could be an autocrine growth factor. Proliferation of DMS-153 cells in vitro was stimulated by GRP and IGF-II and inhibited by JV-1-65. This study indicates that GHRH antagonists and BN/GRP antagonist inhibit the growth of DMS-153 small cell lung carcinoma concomitantly with the expression of mutant Tp53, which might uncouple the signal transduction pathways for cell growth stimulation.

Modulation of benzo[a]pyrene-induced p53 DNA activity by acrolein

Acrolein, a highly electrophilic alpha,beta-unsaturated aldehyde, is by far the most reactive amongst the aldehydes present in smoke. The relative contribution of acrolein to complex mixture toxicity of smoke at the molecular level remains unknown. The current study examines the ability of acrolein to modulate the effect of benzo[a]pyrene (B[a]P), a major carcinogen found in smoke, on p53. Exposure of human lung adenocarcinoma A549 cells to 1 mM B[a]P for 48 h strongly activated the expression of p53 as seen by western blotting, and its DNA binding as shown by an electrophoretic mobility shift assay. Treatment of A549 cells with a non-lethal dose of acrolein alone (50 fmol/cell for 0.5 h) depleted 80% of total cellular glutathione but had no effect on basal p53 protein levels. When B[a]P-treated cells (48 h) were exposed to acrolein for 0.5 h there was also no effect on B[a]P-induced p53 protein levels. However, acrolein treatments profoundly inhibited the DNA binding of p53 under both basal and B[a]P-induced conditions. Depleting glutathione with buthionine sulfoximine in B[a]P-treated cells to levels similar to those obtained with acrolein decreased p53 DNA binding substantially less than with acrolein. Using a p53 dual luciferase reporter assay, acrolein caused an 83% decrease in the p53 activity induced by B[a]P (1 mM for 24 h post-transfection). The p53 protein that was immunoprecipitated after acrolein treatment was reactive with an anti-acrolein antibody indicating covalent modification. Results from this study suggest that acrolein can inhibit p53 DNA binding and activity by direct covalent modification as well as alteration of intracellular redox status. As both acrolein and B[a]P are found in cigarette smoke, this type of interaction may play an important role in the initiation of lung cancer by altering the tumor suppressor activity of p53.

The role of the tumour suppressor p33 ING1b in human neoplasia

The inhibitor of growth (ING) genes (ING1-4) probably descend from tumour suppressor genes. ING1 was the first to be identified and later isolated using an approach to detect genes whose expression is suppressed in cancer. The others were isolated through homology and similarity searches in human and mouse databases. All members contain a plant homeodomain involved in macromolecule recognition. Apart from the extensively studied ING1, little is known about the number of transcripts encoded by the other members or their gene structure. ING1 encodes several differentially spliced mRNAs, which may produce a family of proteins. The most widely expressed protein isoform is p33(INGb1), which is involved in restriction of cell growth and proliferation, apoptosis, tumour anchorage independent growth, cellular senescence, maintenance of genomic stability, and modulation of cell cycle checkpoints. ING1 gene mutation is uncommon in cancer, although the subcellular localisation of p33(INGb1) may have an effect on its function. The p33(INGb1) cellular compartmental shift from the nucleus to the cytoplasm may cause loss of normal cellular function, and may play a central role in the pathogenesis of several cancers.

Peptide and protein drug delivery to and into tumors: challenges and solutions

The potential of peptide and protein anticancer agents has yet to be realized owing to the many unresolved problems concerning their delivery to the site of a tumor and into tumor cells. However, our understanding of the mechanisms underlying the biological fate and biodistribution of protein and peptide drugs has advanced to the stage where methods that use or influence these mechanisms are now available. There are different approaches that can improve the stability, longevity and targeting of peptides and proteins in the body, such as their modification with various soluble polymers, incorporation into microparticular drug carriers, enhanced permeability and retention effect-based tumor targeting and the use of targeting moieties. Furthermore, new approaches to intracellular drug delivery, including the use of transduction proteins and peptides, are being developed. These advances promise the delivery of a new generation of anticancer drugs.

TP53 and liver carcinogenesis

Primary hepatocellular carcinoma (HCC) is one of the most common malignancies and has the fourth highest mortality rate worldwide. The major risk factors, including chronic infections with the hepatitis B or C virus, are exposure to dietary aflatoxin B1(AFB1), vinyl chloride, or alcohol consumption. Southern China and sub-Saharan Africa have the highest dietary AFB1 exposure, making it and hepatitis B virus (HBV) the major causes of cancer mortality in these geographic areas. Recent studies have discovered genetic and epigenetic changes involved in the molecular pathogenesis of HCC, including somatic mutations in the p53 tumor suppressor gene (TP53). AFB1 induces typical G:C to T:A transversions at the third base in codon 249 of p53. Chronic active hepatitis B and C (HCV) infection, and further inflammatory and oxyradical disorders including Wilson disease (WD) or hemochromatosis, generate reactive oxygen/nitrogen species that can damage DNA and mutate the p53 gene. The X gene of HBV (HBx) is the most common open reading frame integrated into the host genome in HCC. The integrated HBx is frequently mutated and has a diminished ability to function as a transcriptional cotransactivator and to activate the NF-kappa B pathway. However, the mutant HBx proteins still retain their ability to bind to and abrogate p53-mediated apoptosis. In summary, both viruses and chemicals are implicated in the etiology and molecular pathogenesis of HCC. The resultant molecular changes in the ras and Wnt signal-transduction pathways, and the p53 and Rb tumor suppressor pathways significantly contribute to liver carcinogenesis

The TP53 gene, tobacco exposure, and lung cancer

Of the various genetic alterations in lung cancer, the abnormalities of the TP53 gene (p53) are among the most frequent and important events. Because of its importance, many aspects of TP53 have been studied, including preneoplastic lesions and TP53as a marker for early detection and prognosis and as a therapeutic option. We summarize recent knowledge of TP53 in lung cancer with a special emphasis on the relationship between smoking exposure (e.g, cigarette, etc.) and specific mutational pattern of TP53by analyzing the latest version of the International Agency for Research on Cancer (IARC) database on TP53 mutations in human cancer. Our analysis confirmed several other studies showing significant differences in the frequencies of G:C to T:A transversions between ever-smokers and never-smokers. Furthermore, when comparing the mutational spectrum by gender, important differences were noted between male and female never-smokers. We concluded that the previously noted G:C to T:A transversions were mainly due to female smokers having a high frequency of these changes compared to female never-smokers. There was no relationship between adenocarcinomas and squamous cell carcinomas independent of gender. We also examined the seven codons which have been previously identified as hot spots, that is, the sites of frequent G:C to T:A transversions in smoking-related lung cancers. However, there was no specific codon which was strongly related to smoke exposure despite a moderate relationship. We considered the term "warmspot" may be more appropriate. While mutations of TP53 are frequent in lung cancers, further investigation is necessary to understand their role for lung carcinogenesis, especially as they relate to gender differences, and to translate our laboratory knowledge to clinical applications.

Loss of heterozygosity analysis of mouse pulmonary adenomas induced by coal tar

Manufactured gas plant (MGP) residues, commonly known as coal tars, were generated several decades ago as a byproduct of residential and industrial gas production from the distillation of coal. Previous short-term exposure studies have shown MGP residues to be tumorigenic in mouse liver and lung. In order to gain further insight into carcinogenesis by complex mixtures of environmental chemicals containing known carcinogenic polycyclic aromatic hydrocarbons, we investigated mouse pulmonary tumors for loss of heterozygosity (LOH) as a result of multiple exposure to MGP residues. Twenty mouse lung adenomas produced in (C57BL/6 x C3H)F1 hybrid mice and manually microdissected were selected to examine genome-wide allelic losses at 58 microsatellite loci. Regions of chromosomes 1, 4, 5, 8, and 11 were affected in 30-40% of tumors. The elevated rates of allelic imbalance in these chromosomes may indicate the location of unknown tumor suppressor genes significant to neoplastic transformation in mouse lung tissues. Laser capture microdissection-based LOH analysis of pulmonary adenomas showed that contamination of nonneoplastic tissues was not masking the allelic losses in the manually microdissected tumor analysis. The low frequency of chromosome instability in these tumors, measured by means of inter-simple sequence repeat PCR, suggests the presence of discrete regions of LOH instead of extensive structural rearrangements.