Novel polymorphism in p21(waf1/cip1) cyclin dependent kinase inhibitor gene: association with human esophageal cancer

The molecular characteristics could supplement the staging system of pT2/T3N0M0 esophageal squamous cell carcinoma: a translational study based on a cohort with over 20 years of follow-up

OBJECTIVE

This study aimed to construct a model based on 23 enrolled molecules to evaluate prognoses of pT2/3N0M0 esophageal squamous cell carcinoma (ESCC) patients with up to 20 years of follow-up.

METHODS

The lasso-Cox model was used to identify the candidate molecule. A nomogram was conducted to develop the survival model (molecular score, MS) based on the molecular features. Cox regression and Kaplan-Meier analysis were used in this study. The concordance index (C-index) was measured to compare the predicted ability between different models. The primary endpoint was overall survival (OS).

RESULTS

A total of 226 patients and 23 proteins were enrolled in this study. Patients were classified into high-risk (MS-H) and low-risk (MS-L) groups based on the MS score of 227. The survival curves showed that the MS-L cohort had better 5-year and 10-year survival rates than the MS-H group (5-year OS: 51.0% vs. 8.0%; 10-year OS: 45.0% vs. 5.0%, all p < 0.001). Furthermore, multivariable analysis confirmed MS as an independent prognostic factor after eliminating the confounding factors (Hazard ratio 3.220, p < 0.001). The pT classification was confirmed to differentiate ESCC patients' prognosis (Log-rank: p = 0.029). However, the combination of pT and MS could classify survival curves evidently (overall p < 0.001), which showed that the prognostic prediction efficiency was improved significantly by the combination of the pT and MS than by the classical pT classification (C-index: 0.656 vs. 0.539, p < 0.001).

CONCLUSIONS

Our study suggested an MS for significant clinical stratification of T2/3N0M0 ESCC patients to screen out subgroups with poor prognoses. Besides, the combination of pT staging and MS could predict survival more accurately for this cohort than the pT staging system alone.

Lifestyle chemical carcinogens associated with mutations in cell cycle regulatory genes increases the susceptibility to gastric cancer risk

In the present study, we correlated the various lifestyle habits and their associated mutations in cell cycle (P21 and MDM2) and DNA damage repair (MLH1) genes to investigate their role in gastric cancer (GC). Multifactor dimensionality reduction (MDR) analysis revealed the two-factor model of oral snuff and smoked meat as the significant model for GC risk. The interaction analysis between identified mutations and the significant demographic factors predicted that oral snuff is significantly associated with P21 3'UTR mutations. A total of five mutations in P21 gene, including three novel mutations in intron 2 (36651738G > A, 36651804A > T, 36651825G > T), were identified. In MLH1 gene, two variants were identified viz. one in exon 8 (37053568A > G; 219I > V) and a novel 37088831C > G in intron 16. Flow cytometric analysis predicted DNA aneuploidy in 07 (17.5%) and diploidy in 33 (82.5%) tumor samples. The G2/M phase was significantly arrested in aneuploid gastric tumor samples whereas high S-phase fraction was observed in all the gastric tumor samples. This study demonstrated that environmental chemical carcinogens along with alteration in cell cycle regulatory (P21) and mismatch repair (MLH1) genes may be stimulating the susceptibility of GC by altering the DNA content level abnormally in tumors in the Mizo ethic population.

Knowledge database assisted gene marker selection for chronic lymphocytic leukemia

Objective

To investigate whether previously curated chronic lymphocytic leukemia (CLL) risk genes could be leveraged in gene marker selection for the diagnosis and prediction of CLL.

Methods

A CLL genetic database (CLL_042017) was developed through a comprehensive CLL-gene relation data analysis, in which 753 CLL target genes were curated. Expression values for these genes were used for case-control classification of four CLL datasets, with a sparse representation-based variable selection (SRVS) approach employed for feature (gene) selection. Results were compared with outcomes obtained by using analysis of variance (ANOVA)-based gene selection approaches.

Results

For each of the four datasets, SRVS selected a subset of genes from the 753 CLL target genes, resulting in significantly higher classification accuracy, compared with randomly selected genes (100%, 100%, 93.94%, 89.39%). The SRVS method outperformed ANOVA in terms of classification accuracy.

Conclusion

Gene markers selected from the 753 CLL genes could enable significantly greater accuracy in the prediction of CLL. SRVS provides an effective method for gene marker selection.

Lysosome-associated protein transmembrane4β is involved in multidrug resistance processes of colorectal cancer

Colorectal cancer (CRC) is one of the most common reasons for cancer-associated mortality worldwide. The present study aimed to investigate the drug resistance mechanism of the oxaliplatin (OXA)-resistant HT-29 cell line (HT-29/L-OHP) and examine the expression of lysosome-associated protein transmembrane 4β (LAPTM4β), a drug resistance-associated gene. In the present study, a drug concentration gradient method was used to establish the drug-resistant HT-29/L-OHP cell line. Cell apoptosis was analyzed by flow cytometry. LAPTM4β mRNA expression was examined by reverse transcription-quantitative polymerase chain reaction analysis and LAPTM4β-35 expression was examined by western blot analysis. Cell morphology of the HT-29/L-OHP drug-resistant cell line was examined. The results indicated that the intercellular space among HT-29 cells was small, with aggregative growth while the intercellular space among HT-29/L-OHP cells was large, with scattered growth. The apoptotic rate in HT-29/L-OHP cells (11.7%) was significantly lower compared with that in HT-29 cells (17.7%) (P<0.05). LAPTM4β mRNA expression in HT-29/L-OHP cells was significantly increased compared with that in HT-29 cells (P<0.05). The relative expression of LAPTM4β-35 protein in HT-29/L-OHP cells was significantly higher compared with that inHT-29 cells (P<0.05). In conclusion, LAPTM4β may be involved in the multidrug resistance processes of CRC. Therefore, LAPTM4β may serve as a novel biomarker for drug resistance of CRC.

Nucleolar GTP-binding Protein-1 (NGP-1) Promotes G1 to S Phase Transition by Activating Cyclin-dependent Kinase Inhibitor p21 Cip1/Waf1

Nucleolar GTP-binding protein (NGP-1) is overexpressed in various cancers and proliferating cells, but the functional significance remains unknown. In this study, we show that NGP-1 promotes G1 to S phase transition of cells by enhancing CDK inhibitor p21(Cip-1/Waf1) expression through p53. In addition, our results suggest that activation of the cyclin D1-CDK4 complex by NGP-1 via maintaining the stoichiometry between cyclin D1-CDK4 complex and p21 resulted in hyperphosphorylation of retinoblastoma protein at serine 780 (p-RB(Ser-780)) followed by the up-regulation of E2F1 target genes required to promote G1 to S phase transition. Furthermore, our data suggest that ribosomal protein RPL23A interacts with NGP-1 and abolishes NGP-1-induced p53 activity by enhancing Mdm2-mediated p53 polyubiquitination. Finally, reduction of p-RB(Ser-780) levels and E2F1 target gene expression upon ectopic expression of RPL23a resulted in arrest at the G1 phase of the cell cycle. Collectively, this investigation provides evidence that NGP-1 promotes cell cycle progression through the activation of the p53/p21(Cip-1/Waf1) pathway.

The effects of two polymorphisms on p21cip1 function and their association with Alzheimer's disease in a population of European descent

With the exception of ApoE4, genome-wide association studies have failed to identify strong genetic risk factors for late-onset Alzheimer’s disease, despite strong evidence of heritability, suggesting that many low penetrance genes may be involved. Additionally, the nature of the identified genetic risk factors and their relation to disease pathology is also largely obscure. Previous studies have found that a cancer-associated variant of the cell cycle inhibitor gene p21^cip1 is associated with increased risk of Alzheimer’s disease. The aim of this study was to confirm this association and to elucidate the effects of the variant on protein function and Alzheimer-type pathology. We examined the association of the p21^cip1 variant with Alzheimer’s disease and Parkinson’s disease with dementia. The genotyping studies were performed on 719 participants of the Oxford Project to Investigate Memory and Ageing, 225 participants of a Parkinson’s disease DNA bank, and 477 participants of the Human Random Control collection available from the European Collection of Cell Cultures. The post mortem studies were carried out on 190 participants. In the in-vitro study, human embryonic kidney cells were transfected with either the common or rare p21^cip1 variant; and cytometry was used to assess cell cycle kinetics, p21^cip1 protein expression and sub-cellular localisation. The variant was associated with an increased risk of Alzheimer’s disease, and Parkinson’s disease with dementia, relative to age matched controls. Furthermore, the variant was associated with an earlier age of onset of Alzheimer’s disease, and a more severe phenotype, with a primary influence on the accumulation of tangle pathology. In the in-vitro study, we found that the SNPs reduced the cell cycle inhibitory and anti-apoptotic activity of p21^cip1. The results suggest that the cancer-associated variant of p21^cip1 may contribute to the loss of cell cycle control in neurons that may lead to Alzheimer-type neurodegeneration.

The role of glycogen synthase kinase 3-β in immunity and cell cycle: implications in esophageal cancer

Esophageal cancer (EC) is one of the most aggressive gastrointestinal malignancies, possessing an insidious onset and a poor prognosis. Numerous transcription factors and inflammatory mediators have been reported to play a pivotal role in the initiation and progression of this cancer. However, the specifics of the signaling network responsible for said factors, especially which elements are the critical regulators, are still being elucidated. Glycogen synthesis kinases 3 (GSK3)β was originally regarded as a kinase regulating glucose metabolism. Accumulating evidence demonstrated that it also played an essential role in a variety of cellular processes including proliferation, differentiation, inflammation, motility, and survival by regulating various transcription factors such as c-Jun, AP-1, β-catenin, CREB, and NF-κB. Aberrant regulation of GSK3β has been shown to promote cell growth in some cancers, while suppressing it in others, and thus may play an important role in the development of EC. This review will discuss our current understanding of GSK3β signaling, and its control of the expression and activation of various transcription factors that mediate the inflammatory response. We will also explore some of the known mediators of EC progression, and based on current literature, elucidate the potential roles and implications of GSK3 in this disease.

p21(WAF1/Cip1/Sdi1) knockout mice respond to doxorubicin with reduced cardiotoxicity

Doxorubicin (Dox) is an antineoplastic agent that can cause cardiomyopathy in humans and experimental animals. As an inducer of reactive oxygen species and a DNA damaging agent, Dox causes elevated expression of p21(WAF1/Cip1/Sdi1) (p21) gene. Elevated levels of p21 mRNA and p21 protein have been detected in the myocardium of mice following Dox treatment. With chronic treatment of Dox, wild type (WT) animals develop cardiomyopathy evidenced by elongated nuclei, mitochondrial swelling, myofilamental disarray, reduced cardiac output, reduced ejection fraction, reduced left ventricular contractility, and elevated expression of ANF gene. In contrast, p21 knockout (p21KO) mice did not show significant changes in the same parameters in response to Dox treatment. In an effort to understand the mechanism of the resistance against Dox induced cardiomyopathy, we measured levels of antioxidant enzymes and found that p21KO mice did not contain elevated basal or inducible levels of glutathione peroxidase and catalase. Measurements of 6 circulating cytokines indicated elevation of IL-6, IL-12, IFNγ and TNFα in Dox treated WT mice but not p21KO mice. Dox induced elevation of IL-6 mRNA was detected in the myocardium of WT mice but not p21KO mice. While the mechanism of the resistance against Dox induced cardiomyopathy remains unclear, lack of inflammatory response may contribute to the observed cardiac protection in p21KO mice.

Current status of biodosimetry based on standard cytogenetic methods

Knowledge about dose levels in radiation protection is an important step for risk assessment. However, in most cases of real or suspected accidental exposures to ionizing radiation (IR), physical dosimetry cannot be performed for retrospective estimates. In such situations, biological dosimetry has been proposed as an alternative for investigation. Briefly, biodosimetry can be defined as individual dose evaluation based on biological endpoints induced by IR (so-called biomarkers). The relationship between biological endpoints and absorbed dose is not always straightforward: nausea, vomiting and diarrhoea, for example, are the most well-known biological effects of individual irradiation, but a precise correlation between those symptoms and absorbed dose is hardly achieved. The scoring of unstable chromosomal-type aberrations (such as dicentrics and rings) and micronuclei in mitogen-stimulated peripheral blood, up till today, has been the most extensively biodosimetry assay employed for such purposes. Dicentric assay is the gold standard in biodosimetry, since its presence is generally considered to be specific to radiation exposure; scoring of micronuclei (a kind of by-product of chromosomal damages) is easier and faster than that of dicentrics for dose assessment. In this context, the aim of this work is to present an overview on biodosimetry based on standard cytogenetic methods, highlighting its advantages and limitations as tool in monitoring of radiation workers' doses or investigation into accidental exposures. Recent advances and perspectives are also briefly presented.

Role of p53 and p21 polymorphisms in the risk of cervical cancer among Chinese women

The objective of this study was to identify whether polymorphic variants of p53 at codon 72 and p21 at codon 31 were associated with increased risk for cervical cancer, either independently or jointly, among Chinese women from southern Han. We genotyped p53 codon 72 and p21 codon 31 polymorphisms of peripheral blood DNA from 104 cervical cancer patients and 160 controls. Genotyping was confirmed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct DNA sequencing. We observed an increased risk of cervical cancer associated with the p53 Arg/Arg (OR, 2.25; 95% CI, 1.11-4.54) or p21 Ser/Ser (OR, 2.09; 95% CI, 1.04-4.19) genotype, compared with the p53 Pro/Pro or p21 Arg/Arg genotype, respectively. In additional, interaction between these p53 and p21 polymorphisms increased the risk of cervical cancer in a multiplicative manner, with the OR being 3.96 (95% CI, 1.51-10.41) for subjects carrying both p53 Arg/Arg and p21 Ser/Ser genotypes. These findings suggest that there is a significant association between the genetic polymorphism of p53, p21, and the risk of cervical cancer among Chinese southern women, and there is a possible gene-gene interaction in the incidence of cervical cancer.

Alcohol drinking, cigarette smoking, and the development of squamous cell carcinoma of the esophagus: molecular mechanisms of carcinogenesis

Esophageal cancer is the eighth most common incident cancer in the world and ranks sixth among all cancers in mortality. Esophageal cancers are classified into two histological types; esophageal squamous cell carcinoma (ESCC), and adenocarcinoma, and the incidences of these types show a striking variety of geographic distribution, possibly reflecting differences in exposure to specific environmental factors. Both alcohol consumption and cigarette smoking are major risk factors for the development of ESCC. Acetaldehyde is the most toxic ethanol metabolite in alcohol-associated carcinogenesis, while ethanol itself stimulates carcinogenesis by inhibiting DNA methylation and by interacting with retinoid metabolism. Cigarette smoke contains more than 60 carcinogens and there are strong links between some of these carcinogens and various smoking-induced cancers; these mechanisms are well established. Synergistic effects of cigarette smoking and alcohol consumption are also observed in carcinogenesis of the upper aerodigestive tract. Of note, intensive molecular biological studies have revealed the molecular mechanisms involved in the development of ESCC, including genetic and epigenetic alterations. However, a wide range of molecular changes is associated with ESCC, possibly because the esophagus is exposed to many kinds of carcinogens including alcohol and cigarette smoke, and it remains unclear which alterations are the most critical for esophageal carcinogenesis. This brief review summarizes the general mechanisms of alcohol- and smoking-induced carcinogenesis and then discusses the mechanisms of the development of ESCC, with special attention to alcohol consumption and cigarette smoking.

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.

Polymorphisms of the ICAM-1 exon 6 (E469K) are associated with differentiation of colorectal cancer

Background

Genetic factors are thought to play a role in development for colorectal carcinogenesis. ICAM-1 is a polymorphic gene, thus, the present study investigated the relationship between the polymorphisms of ICAM-1 and the susceptibility and phenotypical characteristics of colorectal cancer (CRC).

Methods

The polymorphisms at ICAM-1 exon 4 (G241R) and exon 6 (E469K) were detected by PCR with sequence-specific primers. The relationship between specific genotypes of ICAM-1 and differentiation of CRC was evaluated by the histological grade.

Results

We showed only GG genotype of ICAM-1 individuals in either CRC or normal controls. The KK genotype of ICAM-1 K469E was found more frequently than in the controls (P < 0.05). Patients with well-differentiated CRC displayed the KK more frequently than those of poor differentiation (P < 0.05).

Conclusion

The findings indicate that polymorphisms of G241R are rare in Chinese population and that KK genotype of ICAM-1 K469E is significantly associated with well differentiation of CRC.

Human papillomavirus E7 oncoprotein overrides the tumor suppressor activity of p21Cip1 in cervical carcinogenesis

The E7 oncoprotein of the high-risk human papillomaviruses (HPV) is thought to contribute to cervical carcinogenesis at least in part by abrogating cell cycle regulation. E7 can dysregulate the cell cycle through its interaction with several cellular proteins including the retinoblastoma suppressor protein pRb, as well as the cyclin-dependent kinase inhibitor p21(Cip1). Inactivation of pRb in cervical epithelia is not sufficient to explain the ability of E7 to cause cervical cancers in transgenic mice. In the current study, we focused on the role of p21(Cip1) in cervical cancer. Cervical disease was significantly increased in p21(-/-) mice compared with p21(+/+) mice, showing that p21(Cip1) can function as a tumor suppressor in this tissue. Importantly, the ability of E7 to induce cervical cancers was not significantly enhanced on the p21-null background, consistent with the hypothesis that the ability of E7 to inhibit p21(Cip1) contributes to its carcinogenic properties. Further supportive of this hypothesis, cervical carcinogenesis in mice expressing a mutant form of HPV-16 E7, E7(CVQ), which fails to inactivate p21(Cip1), was significantly reduced compared with that in K14E7(WT) mice expressing wild-type HPV-16 E7. However, K14E7(CVQ) mice still displayed heightened levels of cervical carcinogenesis compared with that in nontransgenic mice, indicating that activities of E7 besides its capacity to inactivate p21(Cip1) also contribute to cervical carcinogenesis. Taken together, we conclude that p21(Cip1) functions as a tumor suppressor in cervical carcinogenesis and that p21(Cip1) inactivation by HPV-16 E7 partially contributes to the contribution of E7 to cervical carcinogenesis.

A novel type of p53 pathway dysfunction in chronic lymphocytic leukemia resulting from two interacting single nucleotide polymorphisms within the p21 gene

The ATM-p53 pathway plays an important role in the biology of chronic lymphocytic leukemia (CLL). Its functional integrity can be probed by exposing CLL cells to ionizing radiation (IR) and measuring levels of p53 protein and one of its transcriptional targets, the cyclin-dependent kinase inhibitor p21. We have previously identified two abnormal p53/p21 response patterns associated with inactivating mutations of TP53 and ATM, respectively. Here, we describe a third abnormal response pattern characterized by failure of p21 protein accumulation despite a normal p53 protein response. This so-called "type C" response was detected in 10.6% of unselected patients and was associated with resistance of CLL cells to p53-dependent killing by IR, with the clinically more aggressive variant of CLL characterized by unmutated immunoglobulin heavy-chain genes and with a single nucleotide polymorphism at codon 31 of the p21 gene in which Ser is replaced by Arg. CLL samples with this allelic variant displayed impaired IR-induced up-regulation of total p21 mRNA and did not express the Arg-encoding transcript, except in those cases harboring an additional single nucleotide polymorphism (T instead of C) in the 3'-untranslated region of the same p21 allele. Our data provide new insight into the importance of p21 in CLL biology.

p21 in cancer: intricate networks and multiple activities

One of the main engines that drives cellular transformation is the loss of proper control of the mammalian cell cycle. The cyclin-dependent kinase inhibitor p21 (also known as p21WAF1/Cip1) promotes cell cycle arrest in response to many stimuli. It is well positioned to function as both a sensor and an effector of multiple anti-proliferative signals. This Review focuses on recent advances in our understanding of the regulation of p21 and its biological functions with emphasis on its p53-independent tumour suppressor activities and paradoxical tumour-promoting activities, and their implications in cancer.

Polymorphisms in cell cycle regulatory genes, urinary arsenic profile and urothelial carcinoma

INTRODUCTION

Polymorphisms in p53, p21 and CCND1 could regulate the progression of the cell cycle and might increase the susceptibility to inorganic arsenic-related cancer risk. The goal of our study was to evaluate the roles of cell cycle regulatory gene polymorphisms in the carcinogenesis of arsenic-related urothelial carcinoma (UC).

METHODS

A hospital-based case-controlled study was conducted to explore the relationships among the urinary arsenic profile, 8-hydroxydeoxyguanosine (8-OHdG) levels, p53 codon 72, p21 codon 31 and CCND1 G870A polymorphisms and UC risk. The urinary arsenic profile was determined using high-performance liquid chromatography (HPLC) and hydride generator-atomic absorption spectrometry (HG-AAS). 8-OHdG levels were measured by high-sensitivity enzyme-linked immunosorbent assay (ELISA) kits. Genotyping was conducted using polymerase chain reaction-restriction fragment length polymerase (PCR-RFLP).

RESULTS

Subjects carrying the p21 Arg/Arg genotype had an increased UC risk (age and gender adjusted OR=1.53; 95% CI, 1.02-2.29). However, there was no association of p53 or CCND1 polymorphisms with UC risk. Significant effects were observed in terms of a combination of the three gene polymorphisms and a cumulative exposure of cigarette smoking, along with the urinary arsenic profile on the UC risk. The higher total arsenic concentration, monomethylarsonic acid percentage (MMA%) and lower dimethylarsinic acid percentage (DMA%), possessed greater gene variant numbers, had a higher UC risk and revealed significant dose-response relationships. However, effects of urinary 8-OHdG levels combined with three gene polymorphisms did not seem to be important for UC risk.

CONCLUSIONS

The results showed that the variant genotype of p21 might be a predictor of inorganic arsenic-related UC risk.

p21-LacZ reporter mice reflect p53-dependent toxic insult

There is an urgent need to discover less toxic and more selective drugs to treat disease. The use of transgenic mice that report on toxic insult-induced transcription can provide a valuable tool in this regard. To exemplify this strategy, we have generated transgenic mice carrying a p21-LacZ transgene. Transgene activity reflected endogenous p21 gene activation in various tissues, displayed compound-specific spatial expression signatures in the brain and immune tissues and enabled p53-dependent and p53-independent responses to be identified. We discuss the application of these mice in delineating the molecular events in normal cellular growth and disease and for the evaluation of drug toxicity.

Regulation of cyclin-dependent kinase inhibitor p21WAF1/CIP1 by protein kinase Cdelta-mediated phosphorylation

Cyclin-dependent kinase (CDK) inhibitor p21(WAF1/CIP1(-/-))-null mice have an increased incidence of tumor formation. Here, we demonstrate that p21(WAF1/CIP1) is unstable in HeLa cells treated with siRNA duplexes that target PKCdelta. PKCdelta phosphorylates p21(WAF1/CIP1 )at a serine residue ((146)Ser) located in its C-terminal domain. In cells treated with 12-O-tetradecanoylphorbol 13-acetate, the levels of both p21(WAF1/CIP1) and its (146)Ser-phosphorylated form increased significantly. We also show that a substitution, resulting from a single nucleotide polymorphism (SNP) at (149)Asp found in certain cancer patients, strongly compromises PKCdelta-mediated phosphorylation at (146)Ser and results in cells that are relatively resistant to TNFalpha-induced apoptosis. Thus, post-translational phosphorylation of p21(WAF1/CIP1) is important from an apoptotic cell death, and may also have patho-physiological relevance for the development of human cancer.

Genetic polymorphisms and esophageal cancer risk

The aim of this paper is to review and evaluate, in a comprehensive manner, the published data regarding the contribution of genetic polymorphisms to risk of esophageal cancer, including squamous cell carcinoma (SCC) and adenocarcinoma, in humans. All relevant studies available in MEDLINE and published before February 2007 were identified. Studies carried out in humans and that compared esophageal cancer patients with at least 1 standard control group were considered for analysis. One-hundred studies and 3 meta-analyses were identified. Eighty (80%) studies were conducted in Asian countries, particularly China including Taiwan (60 (60%) studies). The most intensively examined genes were those encoding carcinogen metabolic enzymes. The most widely studied gene was GSTM1 (15 studies), followed by ALDH2 (11 studies). ALDH2, MTHFR C677T, CYP1A1 Ile/Val, CYP1A1MspI, CYP2E1, GSTP1, GSTM1 and GSTT1 were examined by meta-analyses and significant relations were found between ALDH2*1*2 and the CYP1A1 Val allele and increased risk of esophageal cancer. In addition, increased risk of esophageal SCC was consistently associated with the ADH2*1*2 and the p53 codon 72 Pro/Pro genotypes. Cohort studies that simultaneously consider multiple genetic and environmental factors possibly involved in esophageal carcinogenesis are needed to ascertain not only the relative contribution of these factors to tumor development but also the contributions of their putative interactions.

Relationship between LAPTM4B gene polymorphism and susceptibility of colorectal and esophageal cancers

BACKGROUND

Lysosome-associated protein transmembrane 4 beta (LAPTM4B) is a novel gene of the mammalian LAPTM family and has been shown to be overexpressed in human hepatocellular carcinoma. There are two alleles, LAPTM4B*1 and *2, which share the same sequence except for one segment of 19 bp in the 5' untranslated region of the exon 1. LAPTM4B*1 has one 19 bp segment, while LAPTM4B*2 has two tight tandem segments. The current case-control study was aimed to identify relationship between the gene polymorphism of LAPTM4B and the susceptibility of colorectal and esophageal cancers.

PATIENTS AND METHODS

Blood samples were collected from patients with colon, rectal or esophageal cancers and control subjects. Genotypes of LAPTM4B were determined by PCR to detect differences between cancer cases (n = 701) and healthy controls (n = 350). Association between the LAPTM4B polymorphism and the risk of cancer was calculated by unconditional logistic regression models.

RESULTS

We found that there was a significant difference (P = 0.0016) in allelic frequencies of LAPTM4B*2 between colon cancer cases (33.2%) and controls (24.1%). The risk of colon cancer was elevated significantly in cases with *1/2 genotype [odds ratio (OR) = 1.474; 95% confidence interval (CI) = 1.037-2.095] and *2/2 genotype (OR = 2.531; 95% CI = 1.316-4.868) when compared with the *1/1 genotype. No significant difference was observed for LAPTM4B*2 between the rectal or esophageal cancer cases when compared with the controls. The polymorphism in LAPTM4B was associated with increased risk of colon cancer but not of rectal and esophageal cancers.

CONCLUSIONS

These results indicate that the genetic polymorphism of LAPTM4B is a potential risk factor for the development of colon cancer.

The oncogenic potential of human papillomaviruses: a review on the role of host genetics and environmental cofactors

Human papillomaviruses (HPVs), with over 100 genotypes, are a very complex group of human pathogenic viruses. In most cases, HPV infection results in benign epithelial proliferations (verrucae). However, oncogenic types of HPV may induce malignant transformation in the presence of cofactors. For example, over 99% of all cervical cancers and a majority of vulval, vaginal, anal and penile cancers are the result of oncogenic HPV types. Such HPV types have been increasingly linked to other epithelial cancers involving the skin, larynx and oesophagus. Although viral infection is necessary for neoplastic transformation, evidence suggests that host and environmental cofactors are also required. Research investigating HPV oncogenesis is complex and quite extensive. The inability to produce mature HPV virions in animal models has been a major limitation in fully elucidating the oncogenic potential and role of associated cofactors in promoting malignant transformation in HPV-infected cells. We have reviewed the literature and provide a brief account of the current understanding of HPV oncogenesis, emphasizing the role of genetic susceptibility, immune response, and environmental and infectious cofactors.

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.

Protection against esophageal cancer in rodents with lyophilized berries: potential mechanisms

For several years, our laboratory has been evaluating the ability of lyophilized (freeze-dried) black raspberries (Rubus occidentalis, BRBs), blackberries (R. fructicosus, BBs), and strawberries (Fragaria ananasia, STRWs) to inhibit carcinogen-induced cancer in the rodent esophagus. To assure "standardized" berry preparations for study, each berry type is of the same cultivar, picked at about the same degree of ripeness, washed and frozen within 2-4 h of the time of picking, and freeze-dried under conditions that preserve the components in the berries. Some of the known chemopreventive agents in berries include vitamins A, C, and E and folic acid; calcium and selenium; beta-carotene, alpha-carotene, and lutein; polyphenols such as ellagic acid, ferulic acid, p-coumaric acid, quercetin, and several anthocyanins; and phytosterols such as beta-sitosterol, stigmasterol, and kaempferol. In initial bioassays, freeze-dried STRW, BRB, and BB powders were mixed into AIN-76A synthetic diet at concentrations of 5% and 10% and fed to Fischer 344 rats before, during, and after treatment with the esophageal carcinogen N-nitrosomethylbenzylamine (NMBA). At 25 wk of the bioassay, all three berry types were found to inhibit the number of esophageal tumors (papillomas) in NMBA-treated animals by 24-56% relative to NMBA controls. This inhibition correlated with reductions in the formation of the NMBA-induced O6-methylguanine adduct in esophageal DNA, suggesting that the berries influenced the metabolism of NMBA leading to reduced DNA damage. Studies are ongoing to determine the mechanisms by which berries influence NMBA metabolism and DNA adduct formation. BRBs and STRWs were also tested in a postinitiation scheme and were found to inhibit NMBA-induced esophageal tumorigenesis by 31-64% when administered in the diet following treatment of the animals with NMBA. Berries, therefore, inhibit tumor promotion and progression events as well as tumor initiation. In vivo mechanistic studies with BRBs indicate that they reduce the growth rate of premalignant esophageal cells, in part, through down-regulation of cyclooxygenase-2 leading to reduced prostaglandin production and of inducible nitric oxide synthase leading to reduced nitrate/nitrite levels in the esophagus. Based upon the preclinical data on rodents, we have initiated prevention trials in humans to determine if berries might exhibit chemopreventive effects in the esophagus.

KLF4, p21 and context-dependent opposing forces in cancer

Krüppel-like factors are transcriptional regulators that influence several cellular functions, including proliferation. Recent studies have shown that one family member, KLF4, can function both as a tumour suppressor and an oncogene. The ability of KLF4 to affect the levels of expression of the cell-cycle regulator p21 seems to be involved, in that this protein might function as a switch that determines the outcome of KLF4 signalling. Is this role of p21 restricted to KLF4, or does p21 represent a nodal point for signals from multiple other factors with opposing functions in cancer?

Lack of evidence that proline homozygosity at codon 72 of p53 and rare arginine allele at codon 31 of p21, jointly mediate cervical cancer susceptibility among Indian women

OBJECTIVES

The objective of this study was to identify whether variants of p53Arg72Pro and p21Ser31Arg were associated with increased risk for cervical cancer (CaCx), either independently or jointly, among Indian women.

METHODS

Genotyping was done by PCR-RFLP using DNA from (i) 120 cervical biopsy tissues of squamous cell carcinoma of the cervix (of which 82 were HPV16/18 positive), and (ii) a total of 205 cytologically normal cervical scrapes (121 HPV-negative and 84 HPV16/18-positive samples, considered as discreet groups). Multiple logistic regression analyses were performed to examine additive or interactive effects of the two factors and for determining age-adjusted OR (95% CI) and P values.

RESULTS

The observed association of proline homozygosity at codon 72 of p53 with CaCx infection (Bhattacharya, P., Duttagupta, C., Sengupta, S. 2002.Proline homozygosity in codon 72 of p53: A risk genotype for Human Papillomavirus related cervical cancer in Indian women. Cancer Lett 188: 207-211) was retained among Indian women harboring HPV16/18 (OR(age-adjusted) = 3.76; 95% CI = 1.03-13.80; P = 0.04). Significant independent association was evident between the p21 arginine allele (rare allele with frequency of 0.1) at codon 31 and CaCx, compared to HPV-negative cytologically normal controls (OR(age-adjusted) = 2.01; 95% CI = 1.00-4.06; P = 0.05). The two risk factors jointly failed to show statistical interaction towards susceptibility to CaCx. The p21 arginine allele was significantly associated with CaCx in the p53 proline non-homozygous group of subjects (OR(age-adjusted) = 2.68; 95% CI: 1.21-5.91; P = 0.01), and specifically in the p53 heterozygous group (OR(age-adjusted) = 2.91; 95% CI = 1.12-7.56; P = 0.03).

CONCLUSIONS

p53 and p21 act in series in mediating cell cycle arrest. However, the two risk factors, p53 proline homozygosity and p21 arginine allele, although part of a common causal pathway, appear to act in a mutually exclusive manner.

Molecular biology of esophageal cancer in the genomics era

The incidence of esophageal adenocarcinoma is rising in the United States and Western countries. Significant differences exist between esophageal adenocarcinoma and squamous cell carcinoma in the molecular mechanisms responsible for the tumorigenesis process. State-of-the-art techniques such as gene microarrays and proteomics will greatly aid in the development of new therapies targeting specific molecular pathways,ultimately leading to improved survival in patients who have esophageal cancer.

Cytosolic p21Waf1/Cip1 increases cell cycle transit in vascular smooth muscle cells

The intracellular localization of signaling proteins is critical in directing their interactions with both upstream and downstream signaling cascade components. While initially described as a cyclin kinase inhibitor, p21Waf1/Cip1 has since been shown to have bimodal effects on cell cycle progression and cell proliferation, and evidence is emerging that intracellular localization of this protein plays a role in directing its signaling properties by dictating its interactions with downstream molecules. Since we have previously demonstrated a pro-apoptotic and cell cycle inhibitory effect of p21 attenuation after transfection of antisense p21 oligodeoxynucleotides (ODN) in several cell lines, we asked whether cytosolic p21 mediates a positive effect on vascular smooth muscle (VSM) cell cycle transit. We now show that transfection of a nuclear-localization signal deficient (DeltaNLS) p21 construct into VSM cells results in increased cytosolic levels of p21 and causes increased cell cycle transit as measured by [3H]thymidine incorporation. Thus, at least in VSM cells, cytosolic localization of p21 is a means by which this signaling protein transmits pro-mitogenic signals to the proteins responsible for G1/S transition. Furthermore, compartmentalization of p21 may help explain the biphasic nature of p21 in a variety of cell types and may lead to therapeutic advances directed at modulating pathologic cell growth in vascular diseases and cancer.

Molecular aspects of esophageal squamous cell carcinoma carcinogenesis

BACKGROUND

The development of human esophageal cancer is a multistep, progressive process. An early indicator of this process is an increased proliferation of esophageal epithelial cells morphologically including basal cell hyperplasia, dysplasia, carcinoma in situ and advanced esophageal squamous cell carcinoma. The process of tumorigenesis at cellular level is related to disorders of the control of cell proliferation and differentiation and controlled cell death (apoptosis). Most of cancer cells contain genetic alterations related to the control of these processes, including transcription factors and apoptosis related proteins.

AIM

In this review, the current knowledge of the genetic profile of this subtype of esophageal tumor is discussed, focusing on the potential of the development of novel tools for clinical management of esophageal squamous cell carcinoma.

CONCLUSIONS

The advances in the field of molecular biology have let us to deeper our knowledge of the process of carcinogenesis of esophagus. Ideally, this knowledge should be translated in benefits for patients suffering from cancer. Thus, better understanding of molecular alterations during carcinogenesis is expected to improve tumor control and prevention and also may lead to better disease management.

Influences of lifestyle habits and p53 codon 72 and p21 codon 31 polymorphisms on gastric cancer risk in Taiwan

Influences of lifestyle habits and p53 codon 72 and p21 codon 31 polymorphisms on the risk for developing primary gastric cancer were examined in 89 gastric adenocarcinoma cases (51 males, 38 females) and 192 controls (106 males, 86 females) in a hospital-based, case-control study in Taiwan. In the final regression model, Helicobacter pylori infection and substance use (cigarette smoking, areca chewing) were significant predictors of risk for developing gastric cancer. Compared with subjects negative for H. pylori infection, positive subjects were 3.65-fold (95% CI = 2.07-6.42) more likely to develop gastric cancer. Compared with non-smokers or non-chewers, subjects with more than a 15 pack-year history or more than a 498 betel-year history (about 20 betel quids/day for 25 years) were 2.27- and 4.86-fold more at risk (95% CI = 1.06-4.84 and 1.20-19.74), respectively. Frequencies of arg/arg, arg/pro and pro/pro in p53 were 11 (12.4%), 53 (59.5%) and 25 (28.1%) in carcinoma cases and 40 (20.8%), 95 (49.5%) and 57 (29.7%) in control cases, respectively. Frequencies of arg/arg, ser/arg and ser/ser in p21 were 26 (29.2%), 36 (40.5%) and 27 (30.3%) in carcinoma cases and 49 (25.5%), 94 (49.0%) and 49 (25.5%) in control cases, respectively. Neither p53, nor p21 polymorphisms were significantly different in cases and controls ( P = 0.16 and P = 0.41, respectively). Results remained insignificant after dichotomizing with respect to cigarette smoking, areca chewing and H. pylori infection. In summary, our data indicate that in Taiwan, H. pylori infection, smoking and areca chewing are significant risk predictors for developing gastric cancer. p53 codon 72 and p21 codon 31 genotypes did not modify these risks.

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.

P53 (codon 72) and P21 (codon 31) polymorphisms alter in vivo mRNA expression of p21

p21 (Waf1/Cip1) is a downstream target of p53. We evaluated the association between p21 polymorphism (codon 31), p53 polymorphism (codon 72) and their corresponding in vivo mRNA expression. In this study, p21 and p53 genetic polymorphisms (using standard PCR-RFLP techniques) and p21 and p53 gene expressions (using a radiolabelled ribonuclease protection assay (RPA) technique) were evaluated in the peripheral leukocytes of 84 individuals (63 with lung cancer). Log-transformed values of mRNA expression by RPA, which approximated a normal distribution, were analyzed. p53 genotypes did not correlate with p53 mRNA log-expression (P>0.05 for all comparisons), but the Pro allele variants of p53 were associated with a significant decrease in mRNA log-expression of its downstream target, p21. The variant Arg allele of p21 was also associated with a significant decrease in p21 mRNA log-expression. When individuals with at least one variant allele of both p53 and p21 (double-variants) were compared with all other genotype groups, these double-variants had significantly lower log-expression of p21 (P<0.005 by both t-tests (crude) and linear regression analyses (adjusted)). This is translated into an approximate 48% reduction in the geometric mean of the mRNA expression of the double-variants, when compared with all other groups. Results were consistent in both patients with lung cancer (n=63) and in normal controls (n=21). In conclusion, the presence of a p53 Pro allele and/or p21 Arg allele is associated with lower downstream target gene expression of p21.

Analysis of CDKN1A polymorphisms: markers of cancer susceptibility?

The CDKN1A (TP21) gene encodes a 21-kD protein that is a critical downstream mediator of wild-type TP53 and an important regulator of the cell cycle. Failure in the function of this gene would be expected to result in abnormal cell proliferation and transformation. Tumor-associated mutations of the coding region of the TP21 are rare. On the other hand, some TP21 polymorphisms have been identified and characterized by single base substitutions. In the present study, we investigated the potential role of TP21 gene polymorphisms in skin, head, and neck tumorigenesis. A total of 261 samples were examined by polymerase chain reaction single-strand conformational analysis, and one mutation at codon 31 and four polymorphisms in exons 2 (codon 55) and 3 [nucleotide (nt)590] and in promoter region (nt2298) were identified. In conclusion, this investigation confirmed the rarity of mutations in this gene, arguing against a role for TP21 mutations in skin, head, and neck cancers. Also, our results show significant differences in nt2298 allele frequencies between normal individuals and skin malignant tumors (P < 0.05). The results suggest that this polymorphism affects TP21 transactivator binding and may be important during the pathogenesis of skin cancer.

On the nature of genetic changes required for the development of esophageal cancer

It is clear that genetic mutations are necessary for the development of cancer, but the exact number required is not clear, with estimates ranging from one critical hit (e.g., p53) to dozens or perhaps even hundreds of expression changes (by microarray analysis) or chromosomal aberrations. We have used a mathematical model to estimate the critical number of mutations required for the development of esophageal cancer (EC) and to test for the likelihood of an EC major susceptibility gene. Our results suggest that six or seven mutations are required for the development of EC and that there is no evidence of a major susceptibility gene. This does not exclude the possibility that gene-environment interactions may not confer susceptibility or risk. The gradual accumulation of aberrant gene function also can explain the progression of pathologic states seen in the esophagus, from early dysplasia through mild to severe dysplasia and, finally, to cancer, as illustrated in our model.

Esophageal cancer in Chinese population: no polymorphism in codon 149 of P21(Waf1/Cip1) cyclin dependent kinase gene

It has recently been suggested that people of the Indian population who carried the codon 149 polymorphism (GAT-->GGT) of P21(Waf1/Cip1) gene were more susceptible to esophageal cancer and oral cancer than the individuals without that polymorphism. Since esophageal cancer is a high incident neoplasm in China, we analysed the same codon of P21(Waf1/Cip1) in the Chinese population. Blood samples from 80 esophageal cancer patients and 80 normal blood donors were collected for DNA extraction. Methods of Polymerase Chain Reaction (PCR) and direct sequencing were used for detection of the polymorphism in codon 149 of P21(Waf1/Cip1). Bioinformatics analysis was also thoroughly performed for this gene. No polymorphism was found in all samples tested. Bioinformatics analysis revealed that the so-called polymorphism of codon 149 reported previously was a wrong one. In conclusion, no polymorphism exists in codon 149 of P21(Waf1/Cip1). It is not appropriate to use it as a susceptible site of the gene in cancer study.

Correlation of p21 gene codon 31 polymorphism and TNF-alpha gene polymorphism with nasopharyngeal carcinoma

Background p21 (WAF1/CIP1) is a downstream protein from p53 and can arrest the cell cycle at the G1/S phase in response to signal from p53. The most frequently seen polymorphic site is at codon 31, where a base change from AGC to AGA causes an amino acid change from serine to arginine. Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that is secreted from macrophages, and is related to a sequence of events in the response to inflammation and cancer formation. The TNF-alpha gene promoter -308 G/A polymorphism has been reported to be associated with some cancers. In this study, these polymorphisms were proposed to be a candidate genetic marker of nasopharyngeal carcinoma (NPC). The distribution was analyzed in 47 NPC patients and a control group of 119 healthy people. The association of the p21 codon 31 polymorphism with NPC was detected by polymerase chain reaction (PCR) and restriction analysis by Blp I endonuclease, and calculated by the chi-square test. The TNF-alpha gene promoter -308 G/A polymorphism was identified by Nco I endonuclease. The distribution of the gene p21 codon 31 polymorphisms showed no significant difference between the two groups. The serine form of p21 codon 31 was more prominent in smokers than nonsmokers among the NPC patients (P < 0.05). There was no significant difference in the distribution of TNF-alpha gene promoter -308 G/A polymorphism between control and cancer patients. The results indicate that the gene p21 codon 31 polymorphism and TNF-alpha promoter -308 polymorphism are not correlated with NPC. However, the difference between smokers and nonsmokers suggests that an environmental factor may be involved in association with the p21 gene in the formation of NPC.

p21 gene codon 31 polymorphism is associated with bladder cancer

The function of p21 is related to cell apoptosis, progression and malignancies. It is thought that p21 is related to cancer formation but is not related to tumor grade. We aimed to investigative the polymorphism of p21 codon 31 as a candidate for the genetic marker of bladder cancer and its progression. The distribution was analyzed in 53 bladder cancer patients, 119 healthy controls in Taiwanese patients. Polymerase chain reaction based restriction analysis was used for the study of the association of p21 codon 31 polymorphism with bladder cancer. There was a significant difference in p21 codon 31 polymorphism between the control and the cancer patients (p < 0.01). The arginine form was prominent in the cancer patient (per copy of the A allele, odds ratio = 2.03, 95% confidence interval = 1.23-3.37). Furthermore, the distribution of this polymorphism was significantly different from non-invasive to invasive bladder cancer (p < 0.05). Serine heterozygote was more prominent in the invasive group with 25 to 1% respectively when compared with the non-invasive group. The polymorphism of p21 codon 31 is associated with bladder cancer. An individual possessing one allele of arginine form in p21 codon 31 has a higher risk of developing bladder cancer than the serine form. Although the mechanism is unclear, our results show p21 gene is associated with tumor grade.

p21 gene codon 31 arginine/serine polymorphism: non-association with endometriosis

p21, an important regulator of the cell cycle, acts as a mediator of the growth-suppressing and -promoting functions of p53. We aimed to investigate the association between codon 31 polymorphisms of p21 gene and endometriosis. Women were divided into two groups: endometriosis (n = 102) and nonendometriosis (n = 119). The gene polymorphism for p21 codon 31 involved a base change from AGC to AGA and amino acid changes from serine (Ser) to arginine (Arg). Polymorphisms (Ser homozygotes, heterozygotes, Arg homozygotes) between both groups were detected and compared. Associations between the endometriosis and polymorphisms were evaluated. The results revealed that the distributions of different p21 polymorphisms in both groups were nonsignificantly different. The proportions of Ser homozygote/heterozygote/Arg homozygote in endometriosis and nonendometriois populations were 26.5/48.0/25.5% and 17.6/50.4/31.9%, respectively. We concluded the noncorrelation between the endometriosis and the p21 codon 31 polymorphism. p21 gene codon 31 arginine/serine polymorphism is not a useful marker for prediction of endometriosis susceptibility.

Predictive molecular markers in non-small cell lung cancer

Recent biotechnologic knowledge has enabled the discovery of a cornucopia of genetic abnormalities commonly involved not only in cancer but also in other diseases ranging from the plague to arteriosclerosis. The wealth of possibilities uncovered by this knowledge inspires the hope that today's dream of a unified concept of common treatment for multiple diseases could become a future reality. This review arbitrarily categorizes recent findings into five major areas. First, cisplatin resistance associated with the nucleotide excision repair pathway can help clinical oncologists to choose between cisplatin and noncisplatin combinations. Second, the relevant role of nuclear factor-kappa B as a predictor of chemosensitivity can lead to the development of new drugs abrogating nuclear factor-kappa B expression. Third, the presence of tubulin mutations, which are directly involved in resistance to microtubule-interactive drugs, can guide chemotherapy based on taxane or nontaxane combinations. In addition, certain chromosomal deletions affect genes involved in deoxyribonucleotide synthesis, like ribonucleotide reductase, that intervene in gemcitabine metabolism; this raises interest in investigating deletion at chromosome 11p15.5 as a potential mechanism of gemcitabine resistance. Finally, an overwhelming number of publications have analyzed genes involved in cell cycle regulation and development as predictive markers of survival; however, where these pieces fit into the puzzle of cancer management is still unclear.