Associations between common polymorphisms in TP53 and p21WAF1/Cip1 and phenotypic features of breast cancer

Association between tobacco substance usage and a missense mutation in the tumor suppressor gene P53 in the Saudi Arabian population

The tumor suppressor gene TP53 and its downstream genes P21 and MDM2 play crucial roles in combating DNA damage at the G1/S cell cycle checkpoint. Polymorphisms in these genes can lead to the development of various diseases. This study was conducted to examine a potential association between tobacco substance usage (TSU) and single-nucleotide polymorphism (SNP) at the exon regions of the P53, P21, and MDM2 genes by comparing populations of smokers and non-smokers from Saudi Arabia. P53 rs1042522 (C/G), P21 rs1801270 (A/C), and MDM2 rs769412 (A/G) were investigated by genotyping 568 blood specimens: 283 from male/female smokers and 285 from male/female non-smokers. The results obtained from the smokers and their control non-smokers were compared according to age, sex, duration of smoking, and type of TSU. Heterozygous CG, homozygous GG, and CG+GG genotypes, as well as the G allele of rs1042522 were significantly associated with TSU in Saudi smokers compared with non-smokers. The C allele frequency of rs1801270 was also associated with TSU in smokers (OR = 1.33, p = 0.049) in comparison with non-smokers, in younger smokers (≤29 years) (OR = 1.556, p = 0.03280) in comparison with non-smokers of the same age, in smokers who had smoked cigarettes for seven years or less (OR = 1.596, p = 0.00882), and in smokers who had consumed shisha (OR = 1.608, p = 0.04104) in comparison with the controls. However, the genotypic and allelic frequencies for rs769412 did not show significant associations with TSU in Saudis. The selected SNP of P53 was strongly associated with TSU and may be linked to TSU-induced diseases in the Saudi Arabian population.

Naphthazarin enhances ionizing radiation-induced cell cycle arrest and apoptosis in human breast cancer cells

Naphthazarin (Naph, DHNQ, 5,8-dihydroxy-l,4-naphthoquinone) is one of the naturally available 1,4-naphthoquinone derivatives that are well-known for their anti-inflammatory, antioxidant, antibacterial and antitumor cytotoxic effects in cancer cells. Herein, we investigated whether Naph has effects on cell cycle arrest and apoptosis in MCF-7 human breast cancer cells exposed to ionizing radiation (IR). Naph reduced the MCF-7 cell viability in a dose-dependent manner. We also found that Naph and/or IR increased the p53-dependent p21 (CIP/WAF1) promoter activity. Noteworthy, our ChIP assay results showed that Naph and IR combined treatment activated the p21 promoter via inhibition of binding of multi-domain proteins, DNMT1, UHRF1 and HDAC1. Apoptosis and cell cycle analyses demonstrated that Naph and IR combined treatment induced cell cycle arrest and apoptosis in MCF-7 cells. Herein, we showed that Naph treatment enhances IR-induced cell cycle arrest and death in MCF-7 human breast cancer cells through the p53-dependent p21 activation mechanism. These results suggest that Naph might sensitize breast cancer cells to radiotherapy by enhancing the p53-p21 mechanism activity.

Association of TP53 codon 72 and intron 3 16-bp Ins/Del polymorphisms with cervical cancer risk

Cervical cancer incidence has grown worldwide, with it being a more significant problem in developing countries. Invasive squamous cell cervical cancers are preceded by a long phase of preinvasive disease, known as cervical intraepithelial neoplasia. Cervical cancer can develop when the virus takes advantage of any TP53 gene dysfunction of the host organism. TP53 is responsible for encoding the tumor suppressor p53 phosphoprotein, which helps preserve genome integrity. Currently, many studies have focused on genetic polymorphisms as an important contribution to cancer susceptibility, but few related to cervical intraepithelial neoplasia (CIN). Thus, the present study aimed to see whether patients with suspected CIN had TP53 gene polymorphisms that might have contributed to the development of neoplasia. This study included 133 women who were referred to the Cervical Pathology Clinic of the Maternity School Assis Chateaubriand MEAC for suspected cervical lesions. Polymorphism genotyping was carried out by the PCR-RFLP technique using DNA extracted from patients' blood. The most frequent genotype in both CIN(+) and CIN(-) patients was Arg/Pro TP53 codon 72 and A1A1 for 16-bp Del in intron 3. No risk of cervical cancer was found for the polymorphisms studied. However, a significant association was found when the two polymorphisms were combined: patients with the A1A1/ArgPro genotype were statistically more frequent in the CIN(-) group (p = 0.042), while A2A2-A1A2/ProArg was significantly more frequent in the CIN(+) group. The results of our study suggest that combined analysis of TP53 polymorphisms Arg72Pro and 16-bp Ins/Del may help to monitor the development of CIN in Brazilian women.

Aberrant promoter hypermethylation of p21 (WAF1/CIP1) gene and its impact on expression and role of polymorphism in the risk of breast cancer

p21 (Waf-1) is a cyclin-dependent kinase inhibitor that plays essential roles in cell growth arrest, terminal differentiation, and apoptosis. Statistically significant difference in the level of methylation of p21/CIP1 (p < 0. 05) between the patients with breast cancer and the healthy controls was observed. Risk of breast cancer was increased in patients with hypermethylated p21/CIP1 promoter by 2.31-fold (OR = 2.31, 95 % CI 1.95-2.74). The downregulation of p21/CIP1 mRNA expression was statistically significant in patients with methylated promoter (p < 0.00) in comparison to patients with unmethylated genes. Downregulation of mRNA expression of p21/CIP1 was up to 79% due to promoter hypermethylation. We examined several p21/CIP1 genotypes in the patients with breast cancer and found that there is no significant association of these p21/CIP1 genotypes with the risk of developing breast cancer. However, a significant 2.21-fold increase in the chance of developing breast cancer was observed in the candidates carrying at least one allele Arg mutant in p21/CIP1 genotype (i.e., Ser/Arg + Arg/Arg) with age >50 (OR = 2.21; 95 % CI 1.03-4.79).

Association of p21 Ser31Arg and p53 Arg72Pro polymorphisms with lung cancer risk in CAPUA study

BACKGROUND

The aim of this study was to investigate how Ser31Arg polymorphisms in p21 may modify lung cancer susceptibility. Because p21 is the major downstream mediator of p53, we analyzed the combined effect of two polymorphisms, p21 Ser31Arg and TP53 Arg72Pro, to elucidate whether polymorphic variants determine the risk of lung cancer.

METHODS

This was designed as a hospital-based case-control study, and included 675 cases and 675 control subjects matched by ethnicity, gender, and age. Genotypes were determined by polymerase chain reaction restriction fragment length polymorphism, and multivariate unconditional logistic regression was performed to analyze the results.

RESULTS

Subjects who carried the p21 Ser31Arg allele had a higher risk of lung cancer (adjusted odds ratio [OR] 1.38; 95% confidence interval [CI] 0.99-2.03). This risk was increased in men aged younger than 55 years (adjusted OR 2.35; 95% CI 1.00-5.51). Smokers had an increased risk of lung cancer (adjusted OR 2.23; 95% CI 1.24-4.02). Men younger than 55 years carrying risk alleles for both genes (p21 Ser31Arg and TP53 Arg72Pro) had an increased risk (adjusted OR 5.78; 95% CI 1.38-24.19), as did smokers with both risk alleles (adjusted OR 4.52; 95% CI 1.52-13.50).

CONCLUSION

The presence of both variant alleles increased the risk of developing lung cancer in men, particularly in smokers younger than 55 years.

Mutations and polymorphisms in TP53 gene--an overview on the role in colorectal cancer

A functionally normal TP53 is essential to protect organisms from developing cancer. Somatic mutations in the gene represent one of the highest recurring perturbations in human tumours, including colorectal cancer (CRC). However, the variegated phenotype of wide spectrum of somatic mutations in TP53 and the complexity of the disease prevent a straight interpretation of the mutational analysis in tumours. In addition to the presence of somatic mutations, polymorphic features of the gene may also contribute to alteration of the normal TP53 functioning and variants, mainly in the form of single nucleotide polymorphisms, can be expected to impact susceptibility to sporadic CRC. In the present study, we reviewed the potential role of alterations in the TP53 gene, both somatic mutations and inherited sequence variations, in predisposition to CRC and in the prognosis and response to therapy. The available data from association studies have mostly shown contradictory outcomes. The majority of the studies were based on limited sample sizes and focussed on a limited number of polymorphisms, with main being the rs1042522 (Arg72Pro). Thus far, there is no possible generalisation of the role of TP53 as also a predictor of therapeutic response and prognosis. The effects of TP53, and its abnormalities, on the response of tumours to cytotoxic drugs, radiation and chemoradiation are complex. However, from studies it is emerging that the inherited genetics of TP53 pathway components could be utilised to further define patient populations in their abilities to induce p53 activity in response to either DNA damaging or p53-targeted therapies.

Involvement of single-nucleotide polymorphisms in predisposition to head and neck cancer in Saudi Arabia

AIM

Individuals differ in their inherited tendency to develop cancer. This has been suggested to be due to genetic variations between individuals. Single-nucleotide polymorphisms (SNPs) are the most common form of genetic variations found in the human population. The aim of this study was to investigate the association between 10 SNPs in genes involved in cell cycle control and DNA repair (p21 C31A, p53 G72C, ATM G1853A, XRCC1 G399A, XRCC3 C241T, Ku80 A2790G, DNA Ligase IV C9T, DNA-PKcs A3434G, TGF-beta T10C, MDM2 promoter T309G) and the risk to develop head and neck cancer.

MATERIALS AND METHODS

A cohort of 407 individuals (156 cancer patients and 251 controls) was included. DNA was extracted from peripheral blood. SNPs were genotyped by direct sequencing.

RESULTS

Data showed significant allelic associations for p21 C31A (p=0.04; odds ratio [OR]=1.44; confidence interval [CI]: 1.02-2.03), Ku80 A2790G (p=0.04; OR=1.5; CI: 1.01-2.23), and MDM2 T309G (p=0.0003; OR=0.58; CI: 0.43-0.78) and head and neck cancer occurrence. Both cancer cases and controls were in Hardy-Weinberg equilibrium.

CONCLUSION

SNPs can be associated with head and neck cancer in the Saudi population. The p21 C31A, Ku80 A2790G, and MDM2 T309G SNPs could be used as genetic biomarkers to screen individuals at high cancer risk.

The TP53 gene polymorphisms and survival of sporadic breast cancer patients

The TP53 gene polymorphisms, Arg72Pro and PIN3 (+16 bp), can have prognostic and predictive value in different cancers including breast cancer. The aim of the present study is to investigate a potential association between different genotypes of these polymorphisms and clinicopathological variables with survival of breast cancer patients in Croatian population. Ninety-four women with sporadic breast cancer were retrospectively analyzed. Median follow-up period was 67.9 months. The effects of basic clinical and histopathological characteristics of tumor on survival were tested by Cox's proportional hazards regression analysis. The TNM stage was associated with overall survival by Kaplan-Meier analysis, univariate, and multivariate Cox's proportional hazards regression analysis, while grade was associated with survival by Kaplan-Meier analysis and univariate Cox's proportional hazards regression analysis. Different genotypes of the Arg72Pro and PIN3 (+16 bp) polymorphisms had no significant impact on survival in breast cancer patients. However, in subgroup of patients treated with chemotherapy without anthracycline, the A2A2 genotype of the PIN3 (+16 bp) polymorphism was associated with poorer overall survival than other genotypes by Kaplan-Meier analysis (P = 0.048). The TP53 polymorphisms, Arg72Pro and PIN3 (+16 bp), had no impact on survival in unselected sporadic breast cancer patients in Croatian population. However, the results support the role of the A2A2 genotype of the PIN3 (+16 bp) polymorphism as a marker for identification of patients that may benefit from anthracycline-containing chemotherapy.

MDM2 and CDKN1A gene polymorphisms and risk of Kaposi's sarcoma in African and Caucasian patients

A single-nucleotide polymorphism in the MDM2 promoter (SNP309; rs2279744) causes elevated transcription of this major negative regulator of p53 in several cancer types. We investigated MDM2 SNP309 and CDKN1A (p21/Waf1/Cip1) codon 31 (rs1801270) polymorphisms in 86 cases of cutaneous Kaposi's sarcoma (KS) from African and Caucasian patients, and 210 healthy controls. A significant increase of the MDM2 SNP309 T/G genotype was observed among classic KS cases (odds ratio 2.38, 95% confidence interval 1.0-5.5). Frequencies of CDKN1A codon 31 genotypes were not significantly different between cases and controls. The results suggest that the MDM2 SNP309 G allele may act as a susceptibility gene for the development of classic KS in Caucasian patients.

The role of TP53 and p21 gene polymorphisms in breast cancer biology in a well specified and characterized German cohort

OBJECTIVE

Abrogation of the function of TP53 gene is supposed to lead to a more aggressive breast cancer phenotype that produces a less favorable clinical outcome. The p21 gene on chromosome 6p21.2 can be stimulated by an activated TP53 gene. A product of transcription, the p21 protein, an inhibitor of cyclin-dependent kinases, has its function in gene repair and angiogenesis during cell division, and can regulate apoptosis. The purpose of this analysis was to examine for an association between the genotypes measured on two single nucleotide polymorphisms (SNPs) located within the TP53 and p21 genes.

METHODS

In a clinical epidemiological case-control study, 814 individuals were recruited. 550 samples (275 cases/275 control) of peripheral blood obtained from women (aged 22-87 years) with breast cancer and from healthy women (aged 23-87 years) were genotyped for frequencies of the following gene variances: R72P/rs1042522 (gene TP53) and S31R/ss4388499 (gene p21).

RESULTS

For the variance in gene TP53 no significant differences between the control group and women with breast cancer could be estimated. For the variance in gene p21 a statistically significant association between the SNP measured within p21 and breast cancer status was observed. The odds ratio for the increased risk for those carrying the CA genotype as opposed to the CC genotype is 1.74 (95% confidence ratio = 1.00-3.05).

CONCLUSION

Despite this finding p21 does not appear to act as an exclusive prognostic marker for breast cancer disease.

Genetic polymorphisms of p21 and risk of second primary malignancy in patients with index squamous cell carcinoma of the head and neck

p21 plays an important role in modulating cell cycle control, inducing apoptosis, and inhibiting cell growth, subsequently affecting cancer risk. We investigated the association between two putatively functional single-nucleotide polymorphisms (SNPs) of p21 (p21 C98A and p21 C70T) among 1282 patients diagnosed with incident squamous cell carcinoma of the head and neck (SCCHN) and risk of second primary malignancy (SPM) in an ongoing molecular epidemiology study. We used Log-rank test and Cox proportional hazard models to assess the association of these two SNPs with SPM-free survival and SPM risk. We found that patients with either p21 variant genotypes of the two polymorphisms had a significantly reduced SPM-free survival compared with patients with either p21 wild-type homozygous genotypes (Log-rank test, P = 0.0016). Compared with patients having the p21 98 CC and p21 70 CC genotypes, the patients having p21 98 CA/AA and p21 70 CT/TT variant genotypes had a significantly greater risk of developing SPM, respectively, [hazard ratio (HR) = 1.80, 95% CI = 1.14-2.82 for p21 C98A and HR = 1.82, 95% confidence interval (CI) = 1.16-2.85 for p21 C70T]. Moreover, after combining the variant genotypes of two SNPs, patients with variant genotypes had a significantly moderately increased risk for SPM compared with patients with no variant genotypes (HR = 2.00, 95% CI = 1.26-3.00), and the risk was particularly pronounced in several subgroups. Our results support an increased risk of SPM after index SCCHN with both p21 polymorphisms individually and in combination.

Polymorphisms in p53 and the p53 pathway: roles in cancer susceptibility and response to treatment

The p53 tumour suppressor protein lies at the crossroads of multiple cellular response pathways that control the fate of the cell in response to endogenous or exogenous stresses and inactivation of the p53 tumour suppressor signalling pathway is seen in most human cancers. Such aberrant p53 activity may be caused by mutations in the TP53 gene sequence producing truncated or inactive mutant proteins, or by aberrant production of other proteins that regulate p53 activity, such as gene amplification and overexpression of MDM2 or viral proteins that inhibit or degrade p53. Recent studies have also suggested that inherited genetic polymorphisms in the p53 pathway influence tumour formation, progression and/or response to therapy. In some cases, these variants are clearly associated with clinico-pathological variables or prognosis of cancer, whereas in other cases the evidence is less conclusive. Here, we review the evidence that common polymorphisms in various aspects of p53 biology have important consequences for overall tumour susceptibility, clinico-pathology and prognosis. We also suggest reasons for some of the reported discrepancies in the effects of common polymorphisms on tumourigenesis, which relate to the complexity of effects on tumour formation in combination with other oncogenic changes and other polymorphisms. It is likely that future studies of combinations of polymorphisms in the p53 pathway will be useful for predicting tumour susceptibility in the human population and may serve as predictive biomarkers of tumour response to standard therapies.

Effect of the p53 codon 72 and intron 3 polymorphisms on non-small cell lung cancer (NSCLC) prognosis

A total of 42 polymorphisms have been identified in the TP53 gene. The polymorphic site of p53 at codon 72 in exon 4 and p53PIN3, a 16 bp insertion/duplication in intron 3, are the most studied. We tested p53PIN3 and the combined effect of the p53 codon72 and PIN3 polymorphisms on prognosis in 101 NSCLC cases. This study provides support for the prognostic effects of the multi-variant alleles from p53 exon 4 and intron 3, resulting in a significantly poorer prognosis in NSCLC. This approach highlights the value of examining multiple polymorphisms in genes to improve survival estimates.

Polymorphic TP53BP1 and TP53 Gene Interactions Associated with Risk of Squamous Cell Carcinoma of the Head and Neck

PURPOSE

Tumor protein 53-binding protein 1 (TP53BP1) and TP53 interact during TP53-mediated transcriptional activation and during checkpoint activation in response to DNA damage. Because suboptimal repair of tobacco-induced DNA damage is associated with risk of squamous cell carcinoma of the head and neck (SCCHN), we hypothesized that potentially functional polymorphisms in TP53BP1 and TP53 may contribute jointly to SCCHN risk.

EXPERIMENTAL DESIGN

In a case-control study, DNA samples from age- and sex-matched SCCHN patients (n=818) and cancer-free controls (n=821) were genotyped for the presence of three variants of TP53BP1 (T-885G, Glu(353)Asp, and Gln(1136)Lys) and three variants of TP53 (Arg(72)Pro, PIN3, and MspI). Multivariate logistic regression was used to assess the adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

Although none of these six genetic variants alone was associated with SCCHN risk, the combined TP53BP1 genotypes were associated with a significant, dose response-dependent decrease in SCCHN risk among carriers of TP53Pro(72)Pro, TP53PIN3del/del, and TP53Msp1AA genotypes (trend test: P=0.024, 0.016, and 0.016, respectively). Furthermore, TP53BP1 variant haplotype GGC carriers who were also TP53 variant homozygotes had a significantly lower risk of SCCHN than did TP53BP1 haplotype TCA carriers (adjusted OR, 0.48; 95% CI, 0.25-0.94 for TP53Pro(72)Pro; adjusted OR, 0.17; 95% CI, 0.04-0.69 for TP53PIN3del/de; and adjusted OR, 0.16; 95% CI, 0.04-0.65 for TP53Msp1AA). There was statistical evidence of interaction between TP53BP1 and TP53 diplotypes (P=0.017).

CONCLUSION

Our data suggest that TP53BP1 variants may have protective effects on SCCHN risk but such effects were confined to TP53 variant allele/haplotype carriers.

Polymorphism of TP53 codon 72 showed no association with breast cancer in Iranian women

Breast cancer is the most common female malignancy worldwide. Despite the high incidence of sporadic cases, the rate of familial breast cancer is low. The tumor suppressor gene TP53 (alias p53), located on chromosome 17, has been involved in various malignancies. Mutations in codon 72 of TP53 have been studied in breast cancer and most solid tumors. For study of polymorphisms and allele frequency, 221 female patients with sporadic breast cancer and 205 healthy blood donors as control group were recruited. DNA from peripheral blood mononuclear cells was extracted and amplified using allele-specific polymerase chain reaction. Frequency of homozygotic arginine at codon 72 was 37.6% in patients and 36.6% in controls, for homozygotic proline it was 13.1 and 19.5%, and for heterozygotic Arg/Pro it was 49.3 and 43.9%, respectively. No significant difference was found between patients and controls regarding allele frequencies. Mutation in codon 72 of TP53 gene was not associated with breast cancer in Iranian patients.

The novel p21 polymorphism p21G251A is associated with locally advanced breast cancer

PURPOSE

p21 is a main effector of growth arrest induced by p53. In addition, a second transcript from the same gene (p21B) has been linked to apoptosis. We previously analyzed p21 status in breast cancer and reported two novel polymorphisms of the p21 gene. In the present study, we present a larger study designed to explore a possible association between these novel polymorphisms and breast cancer.

EXPERIMENTAL DESIGN

The p21/p21B polymorphisms were analyzed in 507 breast cancer patients and 1,017 healthy individuals using cDNA or genomic DNA from tumor and/or blood samples.

RESULTS

We detected five polymorphisms of the p21 gene. Three of these polymorphisms are earlier reported by others, whereas two were reported for the first time in a recent study by us. The presence of the A allele of the p21G251A polymorphism was observed more frequently among patients with primary stage III breast cancer (4.5%) compared with stage I and II tumors (1.5%) and healthy female controls (1.4%; P = 0.007, comparing the three groups; P = 0.0049 and P = 0.0057, comparing locally advanced to stage I/II and healthy controls, or to healthy controls alone, respectively). The allele frequencies of the remaining four polymorphisms were evenly distributed among patients and healthy individuals.

DISCUSSION

The finding of an association between locally advanced breast cancer and one particular polymorphism of the p21 gene suggests this polymorphism to be related to tumor behavior, including enhanced growth rate. If confirmed in other studies, this may add significant information to our understanding of the biology as well as of the clinical behaviour of locally advanced breast cancers.

Variant genotypes of CDKN1A and CDKN1B are associated with an increased risk of breast cancer in Chinese women

p21(Cip1) and p27(Kip1) are cyclin-dependent kinase inhibitors, which can arrest cell proliferation and serve as tumor suppressors. Reduced protein expression of p21(Cip1) and p27(Kip1) was frequently observed in a subset of cancers, including breast cancer. In this study, we hypothesized that genetic variants in CDKN1A (encode for p21(Cip1)) and CDKN1B (encode for p27(Kip1)) may modulate the risk of breast cancer. To test this hypothesis, we evaluated the associations of the polymorphisms of Ser31Arg and C+20T in CDKN1A and C-79T and Gly109Val in CDKN1B, as well as their combinations, with breast cancer risk in a case-control study of 368 breast cancer cases and 467 cancer-free controls in a Chinese population. We found that a significantly increased risk of breast cancer was associated with the variant genotypes of CDKN1B C-79T [adjusted OR = 1.43 (95% CI = 1.03-1.98) for -79TC/TT], compared with the -79CC genotype, but no associations were observed for other variant genotypes. However, the combined variant genotypes of the 4 loci were associated with a significantly increased breast cancer risk (adjusted OR = 1.49, 95% CI = 1.11-2.01 among subjects carrying 3 or more variant alleles), especially among premenopausal women (adjusted OR= 2.30, 95% CI = 1.45-3.66). Furthermore, in premenopausal women, this significant association remained unchanged, after including other individual risk factors in the multivariate logistic regression model, suggesting an independent role of CDKN1A and CDKN1B variants in breast cancer risk. Although the exact biological mechanism remains to be explored, our findings suggest possible involvement of CDKN1A and CDKN1B variants in the etiology of breast cancer. Further large and functional studies are needed to confirm our findings.

Single tube genotyping of GSTM1, GSTT1 and TP53 polymorphisms by multiplex PCR

Glutathione S-transferases (GST) are enzymes involved in the conjugation of a number of human carcinogens, while p53 tumour suppressor gene is the most frequently mutated gene identified till now in human neoplasias. Typically, GSTM1 and GSTT1 genotyping are performed together, with several different protocol described and sometimes with the risk of misclassification due to "false negative", depending on the internal positive control employed. Here, we report a modification of the classical multiplex polymerase chain reaction (PCR) method, allowing the genotyping of GSTM1, GSTT1, together with a polymorphism within the intron 3 of TP53 tumour suppressor gene (a 16 base pairs (bp) duplication) in a single tube, with an appropriate internal positive control. To test the applicability of the method, the frequencies of the deleted alleles of GSTM1 and GSTT1 (null genotypes), and the 16 bp duplication of TP53 gene were assayed in a series of Caucasian DNA samples.

Polymorphisms in the p53 pathway

The p53 tumor suppressor gene continues to be distinguished as the most frequently mutated gene in human cancer; this gene can be found mutated in up to 50% of human tumors of diverse histological type. It is generally accepted that the ability of p53 to induce either growth arrest or programmed cell death in response to diverse stimuli underlies the powerful selection against this protein in the development of cancer. It is somewhat surprising, then, to find p53 and several target genes in this pathway containing polymorphisms that impair their function. The nature of these polymorphic variants, and the mechanism whereby they impair the function of the p53 pathway, are reviewed here-in. The impact of these polymorphisms on cancer risk and the efficacy of therapy are only now becoming unraveled. Of particular relevance in these efforts will be the generation of mouse models of polymorphic variants in p53 and its target genes. Equally important will be better-controlled human studies, where-in haplotypes for p53 (that is, combinations of different polymorphisms in the p53 gene) and for p53-target genes are taken into account, instead of analyses of single gene variants, which have largely predominated to date. Studies in both regards should shed light on an emerging area in cancer biology, the significance of inter-individual differences in genotype on cancer risk, prognosis, and the efficacy of cancer therapy.

TP53 and P21 polymorphisms: response to cisplatinum/paclitaxel-based chemotherapy in ovarian cancer

Ovarian cancer (OC) is the most lethal gynaecologic cancer and its standard treatment consists of platinum-based chemotherapy after cytoreductive surgery. The p53 protein plays a critical role on different cellular processes in response to DNA damage and it is responsible for transcriptional induction of the P21 gene. We have analysed 114 blood samples in order to investigate the effect of the TP53 codon 72 and the P21 3'UTR polymorphisms in response to cisplatinum/paclitaxel chemotherapy for OC treatment. The genotypes of the TP53 codon 72 and P21 3'UTR polymorphism were identified using AS-PCR and PCR-RFLP, respectively. Our results indicate that the TP53 P allele is associated with a worse prognosis (P=0.011) while P21 polymorphism genotypes did not reveal any statistically significant result (P>0.05). Furthermore, simultaneous carriers of the TP53 AA genotype and the P21 CC genotype demonstrate a longer progression-free interval (P=0.020). This study suggests that the characterisation of a genetic profile can contribute to the definition of a better chemotherapy treatment.

Association between TP53 and p21 genetic polymorphisms and acute side effects of radiotherapy in breast cancer patients

p53 and p21 play an important role in G1/S checkpoint control in response to ionizing radiation. Yet the genetic polymorphisms in these genes have not been investigated with respect to radiation toxicity in patients. We therefore assessed the association between TP53 Arg72Pro, p53PIN3 and p21 Ser31Arg polymorphisms and the risk of acute skin toxicity after radiotherapy in a prospective study of 446 female breast cancer patients (average age 60.3+/-9.0 years) receiving radiotherapy after breast conserving surgery. The p53PIN3 polymorphism was determined by standard PCR, and TP53 Arg72Pro and p21 Ser31Arg polymorphisms using melting point analysis of sequence-specific hybridization probes. The development of acute skin toxicity (moist desquamation) was modelled using Cox proportional hazards, accounting for cumulative biologically effective radiation dose. Overall, the development of acute skin toxicity, which presented in 77 patients, was not significantly associated with the polymorphisms studied. Risks were however differential by body mass index. Compared to non-carriers, TP53 72Pro carriers had a non-significantly decreased risk of acute skin toxicity in normal weight women (hazard ratio 0.46, 95% CI, 0.18-1.18) but not in overweight patients (hazard ratio 1.07, 95% CI, 0.61-1.89) (p(interaction) =0.14). Haplotype analysis for the TP53 polymorphisms suggested that effect modification by TP53 72Pro may differ according to the p53PIN3 allele (p(interaction)=0.06). Furthermore, in TP53 72Pro carriers with p21 Ser/Ser genotype, the occurrence of acute toxicity was reduced in normal weight but not overweight patients. In conclusion, the TP53 72Pro variant may be associated with the development of acute skin toxicity after radiotherapy in patients with normal weight. Large clinical studies are needed to clearly confirm this association.

Genetic polymorphisms of p21 are associated with risk of squamous cell carcinoma of the head and neck

The p21 (Waf1/Cip1/CDKN1A) protein regulates the transition from the G1 to the S phase and has an important role in modulating cell-cycle control, apoptosis and cell growth. Two polymorphisms of the p21 gene at codon 31 (p21 C98A, dbSNP rs1801270) and at the 3' untranslated region (p21 T70C, dbSNP rs1059234) may have an effect on the protein function and may thus play a role in the development of cancer. We hypothesized that these two p21 polymorphisms are associated with the risk of squamous cell carcinoma of the head and neck (SCCHN). We tested this hypothesis in a hospital-based case-control study of 712 patients newly diagnosed with SCCHN and 1222 cancer-free controls who were frequency-matched by age, sex and ethnicity. All subjects were non-Hispanic whites. Our results showed that the variant alleles and genotypes were more common among cases than among controls (P < 0.001 and P = 0.013 for p21C70T, and P < 0.001 and P = 0.035 for p21C98A, respectively). Compared with the p21 70CC genotype, there was a significantly greater risk of SCCHN associated with the variant p21 70TC [odds ratio (OR) = 1.47, 95% confidence interval (CI) = 1.12-1.93] and combined p21 70TC/TT (OR = 1.49, 95% CI = 1.14-1.95) genotypes. Similarly, compared with the p21 98CC genotype, there was also a significantly greater SCCHN risk associated with the variant p21 98AC (OR = 1.32, 95% CI = 1.00-1.73) and combined p21 98AC/AA (OR = 1.37, 95% CI = 1.05-1.79) genotypes. When these two polymorphisms were evaluated together by the number of risk alleles, there was a significant increase in SCCHN risk that was dependent on the number of risk alleles (P(trend) = 0.001). Our results suggest that the presence of these two p21 polymorphisms may be a marker of genetic susceptibility to SCCHN.

Genetic polymorphisms in the MMP-2 and MMP-9 genes and breast cancer phenotype

The matrix metalloproteinases (MMPs) have been shown to play important roles in cancer progression. In this study we examined whether common genetic variants in two key MMPs are associated with phenotypic features of breast cancers and patient outcome. A single nucleotide polymorphism in the promoter region of MMP-2 (-1306 C-->T) abolishes Sp1 binding and is associated with lower transcriptional activity, while another in the promoter region of MMP-9 (-1562 C-->T) increases the transcription of this gene. MMP-2 TT homozygous patients had smaller tumors (p=0.006) and contained lower concentrations of estrogen receptor (ER; p=0.002) compared to patients with the MMP-2 CC or CT genotype. Homozygosity for the MMP-2 -1306 T allele was associated with markedly different patient survival depending upon tumor ER status. For patients with ER negative tumors, the MMP-2 TT genotype was associated with poor survival (2/8 patients alive at end of study, 25%) compared to the CC or CT genotypes (59/70, 84%; p < 0.001). For patients with ER positive tumors, the MMP-2 TT genotype was associated with a trend for very good survival (10/10, 100%) compared to the CC or CT genotypes (130/157, 83%; p=0.16). The MMP-9 -1562 T allele was associated with features of good prognosis including non-ductal type histology, positive ER status and the absence of TP53 mutation. Patients with MMP-9 -1562 CT or TT genotypes showed marginally better prognosis compared to CC homozygotes (p=0.06). These findings suggest that breast cancer phenotype and outcome can be influenced by common functional polymorphisms in MMP genes.

p53 Codon 72 and p21 Codon 31 Polymorphisms in Prostate Cancer

The tumor suppressor gene p53 and its downstream effector p21 are thought to play major roles in the development of human malignancy. Polymorphic variants of p53 at codon 72, and p21 at codon 31, have been found to be associated with cancer susceptibility, but few studies have investigated their effect on prostate cancer risk. In this case-control study, we investigated the association of p53 codon 72 and p21 codon 31 polymorphisms with prostate cancer risk in a Taiwanese population. In total, 200 patients with prostate cancer, 247 age-matched male controls, and 181 non–age-matched symptomatic benign prostatic hyperplasia (BPH; American Urological Association symptom score ≥ 8 and prostate volume &gt; 20 gm) recruited from two medical centers in southern Taiwan were genotyped. Overall, we found no significant association between p53 polymorphism and risk of prostate cancer. However, for p21 polymorphism, the frequencies of p21 Ser/Ser, Ser/Arg and Arg/Arg were 52 (26.0%), 85 (42.5%), 63 (31.5%) in case patients, 48 (26.5%), 82 (45.3%), 51 (28.2%) in BPH patients, and 76 (30.8%), 119 (48.2%), 52 (21.1%) in controls, respectively. Among the prostate cancer cases and controls, subjects with Arg/Arg genotype were found to have a 1.78-fold increased risk [95% confidence interval (CI), 1.06-3.01] of developing prostate cancer compared with those having the Ser/Ser genotype, after adjusting for other potential covariates. This significant association was slightly stronger [odds ratio (OR), 2.13; 95% CI, 1.16-3.92] in younger men (≤ 72 years; n = 99 and 126 for cases and controls, respectively) and correlated with localized disease stage (OR, 1.96; 95 % CI, 1.15-3.35) and moderately differentiated prostate cancer (OR, 2.04; 95% CI, 1.17-3.53). In addition, the Arg/Arg genotype was associated with BPH risk in those with large prostate volumes (&gt; 50 mL) compared with those having the Ser/Ser genotype [OR, 2.29; 95% CI, 1.07-4.98]. Our findings suggest that the p21 codon 31 polymorphism may be associated with the development of prostate enlargement and cancer.

Associations between breast cancer susceptibility gene polymorphisms and clinicopathological features

PURPOSE

Genetic polymorphisms may affect not only cancer development but also cancer progression, and as a result could influence cancer phenotypes. The aim of this study was to examine the relationship between breast cancer susceptibility gene polymorphisms and clinicopathological features.

EXPERIMENTAL DESIGN

We genotyped 664 Korean primary breast cancer patients for 17 single-nucleotide polymorphisms (SNPs) in nine genes, using a high-throughput SNP scoring method.

RESULTS

CYP1A1 codon 462 Ile/Val or Val/Val variants and the CYP1B1 codon 432 Leu/Val variant were found more in breast cancer patients </=35 years of age at onset than the common homozygote [odds ratio (OR), 1.6 and 1.7, respectively]. In combination analysis of these two SNPs, the OR was 1.9 when one of them was heterozygous or a rare homozygous form, and increased to 2.3 when both were variants (P = 0.006). Cases with Ile/Val at CYP1A1 codon 462 were 2.6-fold and those with Val/Val were 5.1-fold more likely to have first-degree relatives with breast cancer than those with Ile/Ile (P = 0.002). In the haplotype study of BRCA1, the 2430C/2731T/3667G/4427C/4956G homozygote showed less estrogen receptor negativity than the most common diplotype (OR, 0.5; 95% confidence interval, 0.26-0.94). TP53 codon 72 Arg/Pro or Pro/Pro variants were associated with negative axillary lymph node status (OR, 0.7; 95% confidence interval, 0.49-0.94).

CONCLUSIONS

These results indicate that polymorphisms of some selected breast cancer susceptibility genes are associated with the clinicopathological phenotypes of breast cancer.

A TP53 polymorphism is associated with increased risk of colorectal cancer and with reduced levels of TP53 mRNA

We undertook a case-control study to examine the possible associations of the TP53 variants Arg > Pro at codon 72 and p53PIN3, a 16 bp insertion/duplication in intron 3, with the risk of colorectal cancer (CRC). The p53PIN3 A2 allele (16 bp duplication) was associated with an increased risk (OR 1.55, 95% CI 1.10-2.18, P = 0.012), of the same order of magnitude as that observed in previous studies for other types of cancer. The Pro72 allele was weakly associated with CRC (OR = 1.34, 95% CI 0.98-1.84, P = 0.066). The possible functional role of p53PIN3 was investigated by examining the TP53 mRNA transcripts in 15 lymphoblastoid cell lines with different genotypes. The possibility that the insertion/deletion could lead to alternatively spliced mRNAs was excluded. However, we found reduced levels of TP53 mRNA associated with the A2 allele. In conclusion, the epidemiological study suggests a role for p53PIN3 in tumorigenesis, supported by the in vitro characterization of this variant.

Expression of p21(WAF1) and p53 and polymorphism of p21(WAF1) gene in gastric carcinoma

AIM

To investigate the relationship between expression of p21(WAF1) and p53 gene, and to evaluate the deletion and polymorphism of p21(WAF1) gene in gastric carcinoma (GC).

METHODS

Expression of p21 and p53 proteins, and deletion and polymorphism of p21 gene in GC were examined by streptavidin-peroxidase conjugated method (SP) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) respectively.

RESULTS

The expression of p21 and p53 was found in 100% (20/20) and 0% (0/20) of normal gastric mucosae(NGM), 92.5% (37/40) and 15.0% (6/40) of dysplasia (DP) and 39.8% (43/108) and 56.5% (61/108) of GC, respectively. The positive rate of p21 in GC was lower than that in NGM and DP (P<0.05), while the positive rate of p53 in GC was higher than that in NGM and DP (P<0.05). p21 and p53 were significantly expressed in 63.3% (19/30) and 36.7% (11/30), 35.0% (14/40) and 77.5% (31/40), 26.7% (4/15) and 80.0% (12/15), 30.8% (4/13) and 30.8% (4/13), and 20.0% (2/10) and 30.0% (3/10) of well-differentiated, poorly-differentiated, undifferentiated carcinomas, mucoid carcinomas and signet ring cell carcinomas. The expression of p21 in well-differentiated carcinomas was significantly higher than that in poorly-differentiated, un-differentiated, mucoid carcinomas and signet ring cell carcinomas (P<0.05). Contrarily, The expression of p53 was increased from well-differentiated to poorly-differentiated and un-differentiated carcinomas (P<0.05). The expression of p21 and p53 in paired primary and metastatic GC (35.3% and 70.6%) was different from non-metastatic GC (62.5% and 42.5%) markedly (P<0.05). The expression of p21 in invasive superficial muscle (60.0%) was higher than that in invasive deep muscle or total layer (35.2%) (P<0.05) and was higher in TNM stages I (60.0%) and II (56.2%) than in stages III (27.9%) and IV (22.2%) (P<0.05), whereas the expression of p53 did not correlate to invasion depth or TNM staging (P>0.05). The exoression patterns of p53+/p21-, and of p53-/p21+ were found in 5.0% and 82.5% of DP. There was a significant correlation between expression of p21 and p53 (P<0.05). But there was no significant correlation between expression of both in GC (P>0.05). There was no deletion in exon 2 of p21 gene in 30 cases of GC and 45 cases of non-GC, but polymorphism of p21 gene at exon 2 was found in 26.7% (8/30) of GC and 8.9% (4/45) of non-GC, a significant difference was found between GC and non-GC (P<0.05). There was no significant relation between p21 expression of polymorphism (37.5%, 3/8) and non-polymorphism (45.5%, 10/22) in GC (P>0.05).

CONCLUSION

The loss of p21 protein and abnormal expression of p53 are related to carcinogenesis, differentiation and metastasis of GC. The expression of p21 is related to invasion and clinical staging in GC intimately. The expression of p21 protein depends on p53 protein largely in NGM and DP, but not in GC. No deletion of p21 gene in exon 2 can be found in GC. The polymorphism of p21 gene might be involved in gastric carcinogenesis.There is no significant association between polymorphism of p21 gene and expression of p21 protein.

The -174 G/C gene polymorphism in interleukin-6 is associated with an aggressive breast cancer phenotype

Serum and tissue levels of interleukin-6 (IL-6) have been implicated in the biological phenotype of breast carcinoma. A common G/C polymorphism at position −174 of the IL-6 promoter can influence the expression level of this gene. We therefore investigated for associations between this polymorphism and various phenotypic features in a series of 256 breast cancers. Individuals who were homozygous for the C allele (n=55) were more likely to have higher-grade tumours (P=0.039) with ductal histology (P=0.030) compared to those harbouring at least one wild-type G allele (n=201). Homozygosity for the C allele was also associated with significantly worse overall survival (P=0.031). We conclude that the −174 C allele of IL-6 is associated with a more aggressive breast cancer phenotype.

Association between p21 codon 31 polymorphism and esophageal cancer risk in a Taiwanese population

P21, which regulates the cell growth cycle, is crucial for normal growth and differentiation. One polymorphism in the p21 codon 31 produces variant proteins with an amino acid change (serine (ser) or arginine (arg)). Although several epidemiologic studies have examined the effect of this polymorphism on cancer risk, the findings remain inconclusive, which has motivated us to evaluate the relationship between p21 codon 31 polymorphism and esophageal cancer risk. In this study, 128 cases of esophageal squamous cell carcinoma and 178 control cases from two hospitals in southern Taiwan were genotyped. Frequencies of arg/arg, arg/ser and ser/ser were 23 (18.0%), 62 (48.4%) and 43 (33.6%) in carcinoma cases and 51 (28.6%), 84 (47.2%) and 43 (24.2%) in control cases, respectively. After factoring out other potential contributing factors, patients with ser/ser or arg/ser were 2.17 times more at risk (95% CI=1.03-4.56) for developing esophageal cancer than those with arg/arg. Males (n=274) were found to have a slightly stronger association (adjusted OR=2.45; 95% CI=1.03-5.80). Although the sample size is relatively small, these findings suggest that a codon 31 polymorphism in p21 may be associated with the development of esophageal cancer.

p21Waf1/Cip1 as a therapeutic target in breast and other cancers

The cyclin kinase inhibitor p21, originally described as a universal inhibitor of cyclin-dependent kinases, has since been shown to have additional functions other than CDK inhibition. It is likely that a key role of p21 is to keep cells alive after DNA damage and subsequent p53 induction, in order for the cell to effect repairs. Thus, the increase in p21 seen in some cancers may impart these cells with a survival advantage. Here we discuss how this antiapoptotic aspect of p21 makes it an attractive target for cancer therapy; attenuation of p21 in malignant cells may subvert the normal repair process induced by DNA-damaging chemotherapeutic agents and thus make such drugs more effective.

TP53 and breast cancer

The TP53 gene (p53) is found altered in breast carcinomas in approximately 20-40% of all cases depending on tumor size and stage of the disease. It seems to be an early event in breast tumorigenesis. Several polymorphisms in the TP53 gene have been detected and their possible roles in breast cancer risk and association to type of cancer developed are discussed. The different mutation spectra seen in geographical and ethnic populations may be used to identify environmental exposure contributing to breast cancer development. The role of TP53 mutation as a prognostic marker is reviewed as well as its role as a predictor for therapy response. All data available on TP53 mutation analyses of human breast carcinomas, as well data from transgenic animal studies and experimental cell studies, support an important role for TP53 in mammary carcinogenesis.