Growing evidence suggests that single nucleotide polymorphisms (SNPs) in nucleotide excision repair (NER) pathway genes play an important role in bladder cancer etiology. However, only a limited number of genes and variations in this pathway have been evaluated to date.
In this study, we applied a comprehensive pathway-based approach to assess the effects of 207 tagging and potentially functional SNPs in 26 NER genes on bladder cancer risk using a large case-control study consisting of 803 bladder cancer cases and 803 controls.
A total of 17 SNPs were significantly associated with altered bladder cancer risk at P<0.05, of which 7 SNPs retained noteworthiness after assessed by a Bayesian approach for the probability of false discovery. The most noteworthy SNP was rs11132186 in ING2 gene. Compared to the major allele-containing genotypes, the odds ratio (OR) was 0.52 (95% confidence interval [CI] 0.32–0.83, P = 0.005) for the homozygous variant genotype. Three additional ING2 variants also exhibited significant associations with bladder cancer risk. Significant gene-smoking interactions were observed for three of the top 17 SNPs. Furthermore, through an exploratory classification and regression tree (CART) analysis, we identified potential gene-gene interactions.
We conducted a large association study of NER pathway with bladder cancer risk and identified several novel predisposition variants. We identified potential gene-gene and gene-environment interactions in modulating bladder cancer risk. Our results reinforce the importance of a comprehensive pathway-focused and tagging SNP-based candidate gene approach to identify low-penetrance cancer susceptibility loci.
bladder cancer; genetic susceptibility; nucleotide excision repair; SNP; gene-smoking interaction
Cell cycle progression contributes to the cellular response to DNA-damaging factors, such as chemotherapy and radiation. We hypothesized that the genetic variations in cell cycle pathway genes may modulate treatment responses and affect survival in patients with advanced non-small-cell lung cancer (NSCLC). We genotyped 374 single-nucleotide polymorphisms (SNPs) from 49 cell cycle-related genes in 598 patients with stages III–IV NSCLC treated with first-line platinum-based chemotherapy with/without radiation. We analyzed the individual and combined associations of these SNPs with survival and evaluated their gene–gene interactions using survival tree analysis. In the analysis of survival in all the patients, 39 SNPs reached nominal significance (P < 0.05) and 4 SNPs were significant at P <0.01. However, none of these SNPs remained significant after correction for multiple comparisons at a false discovery rate of 10%. In stratified analysis by treatment modality, after adjusting for multiple comparisons, nine SNPs in chemotherapy alone and one SNP in chemoradiation remained significant. The most significant SNP in chemotherapy group was CCNB2:rs1486878 [hazard ratio (HR) = 1.69, 95% confidence interval (CI), 1.25–2.30, P = 0.001]. TP73: rs3765701 was the only significant SNP in chemoradiation group (HR = 1.87; 95% CI = 1.35–2.59, P = 1.8 × 10−4). In cumulative analysis, we found a significant gene-dosage effect in patients receiving chemotherapy alone. Survival tree analysis demonstrated potential higher order gene–gene and gene–treatment interactions, which could be used to predict survival status based on distinct genetic signatures. These results suggest that genetic variations in cell cycle pathway genes may affect the survival of patients with stages III–IV NSCLC individually and jointly.
Clinical factors predicting pulmonary complications after lung resection have been well described, whereas the role of genetics is unknown. The vascular endothelial growth factor (VEGF) signaling pathway has been linked to acute lung injury. We hypothesized that genetic variations in this pathway may be associated with postoperative pulmonary complications after lung resection.
One hundred ninety-six single nucleotide polymorphisms (SNPs) in 17 genes in the VEGF pathway were genotyped in a discovery set of 264 patients and a replication set of 264 patients who underwent lobectomy for lung cancer. Multivariable analysis adjusting for baseline clinical factors was used to identify SNPs associated with pulmonary complications. Cumulative and classification and regression tree (CART) analyses were used to further stratify risk groups.
The overall number of pulmonary complications was 164/528 (31%). The effects of 6 SNPs were consistent in the discovery and replication sets (pooled p value < 0.05). The rs9319425 SNP in the VEGF receptor gene FLT1 resulted in a 1.50-fold increased risk (1.15–1.96; p = 0.003). A cumulative effect for the number of risk genotypes and complications was also evident (p < 0.01). Patients carrying 5 risk genotypes had a 5.76-fold increase in risk (2.73–12.16; p = 4.44 × 10−6). Regression tree analysis identified potential gene-gene interactions between FLT1:rs9319425 and RAF1:rs713178. The addition of the 6 SNPs to the clinical model increased the area under the receiver operating characteristic curve by 6.8%.
Genetic variations in the VEGF pathway are associated with risk of pulmonary complications after lobectomy. This may offer insight into the underlying biological mechanisms of pulmonary complications.
NSCLC is the leading cause of cancer-related death in the US. Patients with NSCLC are mostly treated with platinum-based chemotherapy, often in combination with radiation therapy. However, the development of chemoresistance is a major hurdle limiting treatment success. In this review, we summarize the current understanding of the genetic factors modulating chemoresistance to platinum chemotherapeutics and their association with clinical outcomes for NSCLC patients. We focus on candidate pathways responsible for drug influx and efflux, metabolism and detoxification, DNA damage repair, and other downstream cellular processes that modulate the effect of platinum-based therapy. We also discuss the application of pathway-based polygenic and genome-wide approaches in identifying genetic factors involved in NSCLC clinical outcomes. Overall, current studies have shown that the effects of each individual polymorphism on clinical outcomes are modest suggesting that a more comprehensive approach that incorporates polygenetic, phenotypic, epidemiologic and clinical variables will be necessary to predict prognosis for NSCLC patients receiving platinum-based chemotherapeutics.
carboplatin; chemotherapy; cisplatin; clinical outcomes; NSCLC
The magnitude of benefit is variable for advanced non-small cell lung cancer (NSCLC) patients receiving platinum-based chemotherapy. The purpose of this study is to determine whether genetic variations in the transforming growth factor-beta (TGF-β) pathway are associated with clinical outcomes in NSCLC patients receiving first-line platinum-based chemotherapy. Five hundred and ninety-eight advanced-stage NSCLC patients who received first-line platinum-based chemotherapy with or without radiotherapy were recruited at the MD Anderson Cancer Center between 1995 and 2007. DNA from blood was genotyped for 227 single nucleotide polymorphisms (SNPs) in 23 TGF-β pathway-related genes to evaluate their associations with overall survival. In individual SNP analysis, 22 variants were significantly associated with overall survival, of which the strongest associations were found for BMP2:rs235756 [hazard ratio (HR) = 1.45; 95% confidence interval (CI), 1.11–1.90] and SMAD3:rs4776342 (HR = 1.25; 95% CI, 1.06–1.47). Fifteen and 18 genetic loci displayed treatment-specific associations for chemotherapy and chemoradiation, respectively, identifying a majority of the cases who would be predicted to respond favorably to a specific treatment regimen. BMP2:rs235753 and a haplotype in SMAD3 were associated with overall survival for both treatment modalities. Cumulative effect analysis showed that multiple risk genotypes had a significant dose-dependent effect on overall survival (Ptrend = 2.44 x 10−15). Survival tree analysis identified subgroups of patients with dramatically different median survival times of 45.39 versus 13.55 months and 18.02 versus 5.89 months for high- and low- risk populations when treated with chemoradiation and chemotherapy, respectively. These results suggest that genetic variations in the TGF-β pathway are potential predictors of overall survival in NSCLC patients treated with platinum-based chemotherapy with or without radiation.
A germline microRNA binding site-disrupting variant, the KRAS-variant (rs61764370), is associated with an increased risk of developing several cancers. Because this variant is most strongly associated with ovarian cancer risk in patients from hereditary breast and ovarian families (HBOC), and with the risk of premenopausal triple negative breast cancer, we evaluated the association of the KRAS-variant with women with personal histories of both breast and ovarian cancer, referred to as double primary patients.
Germline DNA from double primary patients was tested for the KRAS-variant (n = 232). Confirmation of pathologic diagnoses, age of diagnoses, interval between ovarian cancer diagnosis and sample collection, additional cancer diagnoses, and family history were obtained when available. All patients were tested for deleterious BRCA mutations.
The KRAS-variant was significantly enriched in uninformative (BRCA negative) double primary patients, being found in 39% of patients accrued within two years of their ovarian cancer diagnosis. Furthermore, the KRAS-variant was found in 35% of uninformative double primary patients diagnosed with ovarian cancer post-menopausally, and was significantly associated with uninformative double primary patients with a positive family history. The KRAS-variant was also significantly enriched in uninformative patients who developed more then two primary cancers, being found in 48% of women with two breast primaries plus ovarian cancer or with triple primary cancers.
These findings further validate the importance of the KRAS-variant in breast and ovarian cancer risk, and support the association of this variant as a genetic marker for HBOC families previously considered uninformative.
Interindividual variation in genetic background may influence the response to chemotherapy and overall survival for patients with advanced-stage non–small cell lung cancer (NSCLC).
To identify genetic variants associated with poor overall survival in these patients, we conducted a genome-wide scan of 307 260 single-nucleotide polymorphisms (SNPs) in 327 advanced-stage NSCLC patients who received platinum-based chemotherapy with or without radiation at the University of Texas MD Anderson Cancer Center (the discovery population). A fast-track replication was performed for 315 patients from the Mayo Clinic followed by a second validation at the University of Pittsburgh in 420 patients enrolled in the Spanish Lung Cancer Group PLATAX clinical trial. A pooled analysis combining the Mayo Clinic and PLATAX populations or all three populations was also used to validate the results. We assessed the association of each SNP with overall survival by multivariable Cox proportional hazard regression analysis. All statistical tests were two-sided.
SNP rs1878022 in the chemokine-like receptor 1 (CMKLR1) was statistically significantly associated with poor overall survival in the MD Anderson discovery population (hazard ratio [HR] of death = 1.59, 95% confidence interval [CI] = 1.32 to 1.92, P = 1.42 × 10−6), in the PLATAX clinical trial (HR of death = 1.23, 95% CI = 1.00 to 1.51, P = .05), in the pooled Mayo Clinic and PLATAX validation (HR of death = 1.22, 95% CI = 1.06 to 1.40, P = .005), and in pooled analysis of all three populations (HR of death = 1.33, 95% CI = 1.19 to 1.48, P = 5.13 × 10−7). Carrying a variant genotype of rs10937823 was associated with decreased overall survival (HR of death = 1.82, 95% CI = 1.42 to 2.33, P = 1.73 × 10−6) in the pooled MD Anderson and Mayo Clinic populations but not in the PLATAX trial patient population (HR of death = 0.96, 95% CI = 0.69 to 1.35).
These results have the potential to contribute to the future development of personalized chemotherapy treatments for individual NSCLC patients.
Renal cell carcinoma is the eighth most common cancer in the United States and clear cell renal carcinoma is the most common type. Many signaling pathways are implicated in clear cell renal carcinoma development, including the inflammation pathway. However, less is known about how gene expression variation in this pathway influences clear cell renal carcinoma development and clinical outcomes.
Materials and Methods
Gene expression in tumor and adjacent normal tissues from 93 patients was detected using a genome-wide expression array. A panel of 661 inflammation related genes was then analyzed. Differential expression patterns between tumor and normal tissues were identified. Association with recurrence or survival was evaluated with genes showing significant association tested further in a validation set of 258 tumors using an independent platform (quantitative real-time polymerase chain reaction).
We identified 151 genes with at least a two-fold change in gene expression between adjacent normal tissue and tumor, of which most were up-regulated in tumors. A total of 20 genes significantly associated with recurrence and/or overall survival were selected for further validation. In the replication data set high expression of GADD45G was significantly associated with a 2.09-fold (95% CI 1.08 – 6.14, p = 0.034) increased risk of recurrence while high CARD9, NCF2 and CIITA expression was significantly associated with a 2.52-fold (95% CI 1.24 –5.12, p = 0.010), 2.26-fold (95% CI 1.12– 4.58, p = 0.023) and 2.11-fold (95% CI 1.05– 4.27, p = 0.037) increased risk of death, respectively.
Results suggest that inflammation gene expression may be significant prognostic biomarkers for the risk of recurrence (GADD45G) and death (CARD9, CIITA and NCF2) in patients with clear cell renal carcinoma.
kidney; carcinoma; renal cell; inflammation; gene expression; neoplasm recurrence; local
Mutagen sensitivity, a measurement of chromatid breaks induced by various mutagens in short-term cultures of peripheral blood lymphocytes, is an established risk factor for a number of cancers and is highly heritable. The purpose of this study is to identify genetic predictors of mutagen sensitivity. Therefore, we conducted a multi-stage genome-wide association study. The primary scan analyzed 539 437 autosomal SNPs in 673 healthy individuals, followed by validations in two independent sets of 575 and 259 healthy individuals, respectively. One SNP, rs8093763, on chromosome 18q21 showed significant association with bleomycin (BLM) sensitivity (combined P = 2.64 × 10−8). We observed significantly lower BLM-induced chromotid breaks for genotypes containing wild-type allele compared with the homozygous variant genotype in the discovery set (0.71 versus 0.90, P= 3.77 × 10−5) and in replication phase 1 (0.61 versus 0.84, P= 7.00 × 10−5). The result of replication phase 2 was not statistically significant (0.65 versus 0.68, P= 0.44). This SNP is approximately 64 kb from PMAIP1/Noxa, which is a radiation-inducible gene and exhibits higher expression in BLM-sensitive lymphoblastoid cell lines than insensitive cell lines upon BLM treatment. In conclusion, we identified a biologically plausible genetic variant on 18q21 near the PMAIP1/Noxa gene that is associated with BLM sensitivity.
Non-small cell lung cancer (NSCLC) is still the leading cause of cancer-related deaths. The effect of the PI3K/PTEN/AKT/mTOR signaling pathway on cancer treatment, including NSCLC, has been well documented. In this study, we analyzed associations between genetic variations within this pathway and clinical outcomes following platinum-based chemotherapy in 168 patients with stage IIIB (wet) or stage IV NSCLC. Sixteen tagging SNPs in five core genes (PIK3CA, PTEN, AKT1, AKT2, and FRAP1) of this pathway and identified SNPs associated with development of toxicity and disease progression. We observed significantly increased toxicity for patients with PIK3CA:rs2699887 (OR: 3.86, 95% CI: 1.08 – 13.82). In contrast, a SNP in PTEN was associated with significantly reduced risk for chemotherapeutic toxicity (OR: 0.44, 95% CI: 0.20 - 0.95). We identified three SNPs in AKT1 resulting in significantly decreased risks of distant progression in patients carrying at least one variant allele with HRs of 0.66 (95% CI: 0.45 - 0.97), 0.52 (95% CI: 0.35 - 0.77), and 0.62 (95% CI: 0.42 - 0.91) for rs3803304, rs2498804, and rs1130214, respectively. Furthermore, these same variants conferred nearly two-fold increased progression-free survival times. The current study provides evidence that genetic variations within the PI3K/PTEN/AKT/mTOR signaling pathway are associated with variation in clinical outcomes of NSCLC patients. With further validation, our findings may provide additional biomarkers for customized treatment of platinum-based chemotherapy for NSCLC.
lung cancer; chemotherapy; platinum-agents; AKT; clinical outcomes
Sonic hedgehog (Shh) pathway genetic variations may affect bladder cancer risk and clinical outcomes; therefore, we genotyped 177 SNPs in 11 Shh pathway genes in a study including 803 bladder cancer cases and 803 controls. We assessed SNP associations with cancer risk and clinical outcomes in 419 cases of non-muscle invasive bladder cancer (NMIBC) and 318 cases of muscle invasive and metastatic bladder cancer (MiMBC). Only 3 SNPs (GLI3 rs3823720, rs3735361, rs10951671) reached nominal significance in association with risk (P≤0.05), which became non-significant after adjusting for multiple comparisons. Nine SNPs reached a nominally significant individual association with recurrence of NMIBC in patients who received transurethral resection (TUR) only (P≤0.05), of which 2 (SHH rs1233560 and GLI2 rs11685068) were replicated independently in 356 TUR-only NMIBC patients with P-values of 1.0×10−3 (SHH rs1233560) and 1.3×10−3 (GLI2 rs11685068). Nine SNPs also reached a nominally significant individual association with clinical outcome of NMIBC patients who received Bacillus Calmette-Guérin (BCG; P≤0.05), of which 2, the independent GLI3 variants rs6463089 and rs3801192, remained significant after adjusting for multiple comparisons (P=2×10−4 and 9×10−4, respectively). The wild-type genotype of either of these SNPs was associated with a lower recurrence rate and longer recurrence-free survival (versus the variants). Although 3 SNPs (GLI2 rs735557, GLI2 rs4848632, and SHH rs208684) showed nominal significance in association with overall survival in MiMBC patients (P≤0.05), none remained significant after multiple-comparison adjustments. Germline genetic variations in the Shh pathway predicted clinical outcomes of TUR and BCG for NMIBC patients.
sonic hedgehog pathway; cancer risk; recurrence; BCG; non-muscle invasive bladder cancer
The transforming growth factor-β (TGF-β) signaling pathway is involved in a diverse array of cellular processes responsible for tumorigenesis. In this case-control study, we applied a pathway-based approach to evaluate single-nucleotide polymorphisms (SNPs) in the TGF-β signaling pathway as predictors of ovarian cancer risk. We systematically genotyped 218 SNPs from 21 genes in the TGF-β signaling pathway in 417 ovarian cancer cases and 417 matched control subjects. We analyzed the associations of these SNPs with ovarian cancer risk, performed haplotype analysis and identified potential cumulative effects of genetic variants. We also performed analysis to identify higher-order gene-gene interactions influencing ovarian cancer risk. Individual SNP analysis showed that the most significant SNP was SMAD6: rs4147407, with an adjusted odds ratio (OR) of 1.60 (95% confidence interval [CI], 1.14–2.24, P = 0.0066). Cumulative genotype analysis of 13 SNPs with significant main effects exhibited a clear dose-response trend of escalating risk with increasing number of unfavorable genotypes. In gene-based analysis, SMAD6 was identified as the most significant gene associated with ovarian cancer risk. Haplotype analysis further revealed that two haplotype blocks within SMAD6 were significantly associated with decreased ovarian cancer risk, as compared to the most common haplotype. Gene-gene interaction analysis further categorized the study population into subgroups with different ovarian cancer risk. Our findings suggest that genetic variants in the TGF-β signaling pathway are associated with ovarian cancer risk and may facilitate the identification of high-risk subgroups in the general population.
The phosphoinositide-3 kinase (PI3K)–AKT– mammalian target of rapamycin (mTOR) pathway is an important cellular pathway controlling cell growth, tumorigenesis, cell invasion and drug response. We hypothesized that genetic variations in the PI3K–AKT–mTOR pathway may affect the survival in muscle invasive and metastatic bladder cancer (MiM-BC) patients. We conducted a follow-up study of 319 MiM-BC patients to systematically evaluate 289 single-nucleotide polymorphisms (SNPs) of 20 genes in the PI3K–AKT–mTOR pathway as predicators of survival. In multivariate Cox regression, AKT2 rs3730050, PIK3R1 rs10515074 and RAPTOR rs9906827 were significantly associated with survival. In combined analysis, we found a cumulative effect of these three SNPs on survival. With the increasing number of unfavorable genotypes, there was a significant trend of higher risk of death in multivariate Cox regression (P for trend <0.001) and shorter median survival time in Kaplan–Meier estimates (P log rank <0.001). This is the first study to evaluate the role of germ line genetic variations in the PI3K–AKT–mTOR pathway genes as predictors of MiM-BC clinical outcomes. These findings warrant further replication in independent populations and may provide information on disease management and development of target therapies.
We conducted a multi-stage, genome-wide association study (GWAS) of bladder cancer with a primary scan of 589,299 single nucleotide polymorphisms (SNPs) in 3,532 cases and 5,120 controls of European descent (5 studies) followed by a replication strategy, which included 8,381 cases and 48,275 controls (16 studies). In a combined analysis, we identified three new regions associated with bladder cancer on chromosomes 22q13.1, 19q12 and 2q37.1; rs1014971, (P=8×10−12) maps to a non-genic region of chromosome 22q13.1; rs8102137 (P=2×10−11) on 19q12 maps to CCNE1; and rs11892031 (P=1×10−7) maps to the UGT1A cluster on 2q37.1. We confirmed four previous GWAS associations on chromosomes 3q28, 4p16.3, 8q24.21 and 8q24.3, validated previous candidate associations for the GSTM1 deletion (P=4×10−11) and a tag SNP for NAT2 acetylation status (P=4×10−11), as well as demonstrated smoking interactions with both regions. Our findings on common variants associated with bladder cancer risk should provide new insights into mechanisms of carcinogenesis.
Genetic variations in phosphoinositide-3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) pathway may affect critical cellular functions and increase an individual's cancer risk. We systematically evaluate 231 single-nucleotide polymorphisms (SNPs) in 19 genes in the PI3K-AKT-mTOR signaling pathway as predictors of bladder cancer risk. In individual SNP analysis, four SNPs in regulatory associated protein of mTOR (RAPTOR) remained significant after correcting for multiple testing: rs11653499 [odds ratio (OR): 1.79, 95% confidence interval (CI): 1.24–2.60, P = 0.002], rs7211818 (OR: 2.13, 95% CI: 1.35–3.36, P = 0.001), rs7212142 (OR: 1.57, 95% CI: 1.19–2.07, P = 0.002) and rs9674559 (OR: 2.05, 95% CI: 1.31–3.21, P = 0.002), among which rs7211818 and rs9674559 are within the same haplotype block. In haplotype analysis, compared with the most common haplotypes, haplotype containing the rs7212142 wild-type allele showed a protective effect of bladder cancer (OR: 0.83, 95% CI: 0.70–0.97). In contrast, the haplotype containing the rs7211818 variant allele showed a 1.32-fold elevated bladder cancer risk (95% CI: 1.09–1.60). In combined analysis of three independent significant RAPTOR SNPs (rs11653499, rs7211818 and rs7212142), a significant trend was observed for increased risk with an increase in the number of unfavorable genotypes (P for trend <0.001). Compared with the subjects without any of the unfavorable genotypes, those carrying all three unfavorable genotypes showed a 2.22-fold (95% CI: 1.33–3.71) increased bladder cancer risk. This is the first study to evaluate the role of germ line genetic variations in PI3K-AKT-mTOR pathway as cancer susceptibility factors that will help us identify high-risk individuals for bladder cancer.
Treatment of non-small cell lung cancer (NSCLC) with radiotherapy or chemoradiotherapy is often accompanied by the development of esophagitis and pneumonitis. Identifying patients who might be at increased risk for normal tissue toxicity would help in determination of the optimal radiation dose to avoid these events. We profiled 59 single nucleotide polymorphisms (SNPs) from 37 inflammation-related genes in 173 NSCLC patients with stage IIIA/IIIB (dry) disease who were treated with definitive radiation or chemoradiation. For esophagitis risk, nine SNPs were associated with a 1.5- to 4-fold increase in risk, including three PTGS2 (COX2) variants: rs20417 (HR:1.93, 95% CI:1.10–3.39), rs5275 (HR:1.58, 95% CI:1.09–2.27), and rs689470 (HR:3.38, 95% CI:1.09–10.49). Significantly increased risk of pneumonitis was observed for patients with genetic variation in the proinflammatory genes IL1A, IL8, TNF, TNFRSF1B, and MIF. In contrast, NOS3:rs1799983 displayed a protective effect with a 45% reduction in pneumonitis risk (HR:0.55, 95% CI:0.31–0.96). Pneumonitis risk was also modulated by polymorphisms in anti-inflammatory genes, including genetic variation in IL13. rs20541 and rs180925 each resulted in increased risk (HR:2.95, 95% CI:1.14–7.63 and HR:3.23, 95% CI:1.03–10.18, respectively). The cumulative effect of these SNPs on risk was dose-dependent, as evidenced by a significantly increased risk of either toxicity with an increasing number of risk genotypes (P<0.001). These results suggest that genetic variations among inflammation pathway genes may modulate the development of radiation-induced toxicity and, ultimately, help in identifying patients who are at an increased likelihood for such events.
The phosphoinositide-3-kinase (PI3K), phosphatase and tensin homolog (PTEN), v-akt murine thymoma viral oncogene homolog (AKT), and mammalian target of rapamycin (mTOR) signaling pathway has been implicated in resistance to several chemotherapeutic agents. In this retrospective study, we determined whether common genetic variations in this pathway are associated with clinical outcomes in esophageal cancer patients with adenocarcinoma or squamous cell carcinoma who have undergone chemoradiotherapy and surgery.
Patients and Methods
Sixteen tagging single nucleotide polymorphisms (SNPs) in PIK3CA, PTEN, AKT1, AKT2, and FRAP1 (encoding mTOR) were genotyped in these patients and analyzed for associations with response to therapy, survival, and recurrence.
We observed an increased recurrence risk with genetic variations in AKT1 and AKT2 (hazard ratio [HR], 2.21; 95% CI, 1.06 to 4.60; and HR, 3.30; 95% CI, 1.64 to 6.66, respectively). This effect was magnified with an increasing number of AKT adverse genotypes. In contrast, a predictable protective effect by PTEN genetic variants on recurrence was evident. Survival tree analysis identified higher-order interactions that resulted in variation in recurrence-free survival from 12 to 42 months, depending on the combination of SNPs. Genetic variations in AKT1, AKT2, and FRAP1 were associated with survival. Patients homozygous for either of the FRAP1 SNPs assayed had a more than three-fold increased risk of death. Two genes—AKT2 and FRAP1—were associated with a poor treatment response, while a better response was associated with heterozygosity for AKT1:rs3803304 (odds ratio, 0.50; 95% CI, 0.25 to 0.99).
These results suggest that common genetic variations in this pathway modulate clinical outcomes in patients who undergo chemoradiotherapy. With further validation, these results may be used to build a model of individualized therapy for the selection of the optimal chemotherapeutic regimen.
The proteasome is a multisubunit cellular organelle that functions as a nonlysosomal threonine protease. Proteasomes play a critical role in the degradation of proteins, regulating a variety of cellular processes, and they are also the target for antineoplastic proteasome inhibitors. Genetic variation in proteasome subunits could influence both proteasome function and response to drug therapy.
We resequenced genes encoding the three active proteasome β subunits using 240 DNA samples from four ethnic groups and the β5 subunit gene in 79 DNA samples from multiple myeloma patients who had been treated with the proteasome inhibitor bortezomib. Resequencing was followed by functional studies of polymorphisms identified in the coding region and 3′-flanking region (3′-FR) of PSMB5, the gene encoding the target for clinically useful proteasome inhibitors.
Resequencing of 240 DNA samples identified a series of novel ethnic-specific polymorphisms that are not represented in public databases.The PSMB5 3′-FR1042 G allele significantly increased transcription during reporter gene studies, observations confirmed by genotype-phenotype correlations between single nucleotide polymorphisms (SNP) in PSMB5 and mRNA expression in the 240 lymphoblastoid cell lines from which the resequenced DNA was obtained. Studies with patient DNA samples identified additional novel PSMB5 polymorphisms, including a SNP and an insertion in the 3′-FR. Reporter-gene studies indicated that these two novel polymorphisms might decrease transcription.
These results show that nonsynonymous coding SNPs in the PSMB5 gene did not show significant effects on proteasome activity, but SNPs did influence transcription. Future studies might focus on regulatory region polymorphisms.
Two cytidine analogues, gemcitabine (dFdC) and cytosine arabinoside (AraC), show significant therapeutic effect in a variety of cancers. However, response to these drugs varies widely. Evidence from tumor biopsy samples shows that expression levels for genes involved in the cytidine transport, metabolism and bioactivation pathway contribute to this variation in response. In the present study, we set out to test the hypothesis that variation in gene expression both within and outside of this “pathway” might influence sensitivity to gemcitabine and AraC. Specifically, Affymetrix U133 Plus 2.0 GeneChip and cytotoxicity assays were performed to obtain basal mRNA expression and IC50 values for both drugs in 197 ethnically-defined Human Variation Panel lymphoblastoid cell lines. Genes with a high degree of association with IC50 values were involved mainly in cell death, cancer, cell cycle, and nucleic acid metabolism pathways. We validated selected significant genes by performing real time quantitative RT-PCR and selected two representative candidates, NT5C3 (within the pathway) and FKBP5 (outside of the pathway), for functional validation. Those studies demonstrated that down regulation of NT5C3 and FKBP5 altered tumor cell sensitivity to both drugs. Our results suggest that cell-based model system studies, when combined with complementary functional characterization, may help to identify biomarkers for response to chemotherapy with these cytidine analogues.
cytidine analogues; gemcitabine; dFdC; cytosine arabinoside; AraC; lymphoblastoid cell lines; expression array; 5′-nucleotidase; cytosolic III nucleotidase; NT5C3; FK506 binding protein 5; FKBP5 and Ingenuity Pathway Analysis
Genetic networks for gene expression data are often built by graphical models, which in turn are built from pairwise correlations of gene expression levels. A key feature of building graphical models is evaluation of conditional independence of two traits, given other traits. When conditional independence can be assumed, the traits that are conditioned on are considered to “explain” the correlation of a pair of traits, allowing efficient building and interpretation of a network. Overlaying genetic polymorphisms, such as single nucleotide polymorphisms (SNPs), on quantitative measures of gene expression provides a much richer set of data to build a genetic network, because it is possible to evaluate whether sets of SNPs “explain” the correlation of gene expression levels. However, there is strong evidence that gene expression levels are controlled by multiple interacting genes, suggesting that it will be difficult to reduce the partial correlation completely to zero. Ignoring the fact that some set of SNPs can explain at least part of the correlation between gene expression levels, if not all, might miss important clues on the genetic control of gene expression. To enrich the assessment of the causes of correlation between gene expression levels, we develop methods to evaluate whether a set of covariates (e.g., SNPs, or even a set of quantitative expression transcripts), explains at least some of the correlation of gene expression levels. These methods can be used to assist the interpretation of regulation of gene expression and the construction of gene regulation networks.
Fisher's z-transformation; Taylor expansion; model selection; pathway; association; multiple regression; optimal linear composites
Catechol O-methyltransferase (COMT)-catalyzed methylation of catecholestrogens has been proposed to play a protective role in estrogen-induced genotoxic carcinogenesis. We have taken a comprehensive approach to test the hypothesis that genetic variation in COMT might influence breast cancer risk. Fifteen COMT SNPs selected on the basis of in-depth resequencing of the COMT gene were genotyped in 1482 DNA samples from a Mayo Clinic breast cancer case-control study. Two common SNPs in the distal promoter for membrane-bound (MB) COMT, rs2020917 and rs737865, were associated with breast cancer risk reduction in premenopausal women in the Mayo Clinic study, with allele-specific odds ratios of 0.70 (95% CI = 0.52–0.95) and 0.68 (95% CI = 0.51–0.92), respectively. These two SNPs were then subjected to functional genomic analysis and were genotyped in an additional 3683 DNA samples from two independent case-control studies (GENICA and GESBC). Functional genomic experiments showed that these SNPs could up-regulate transcription and that they altered DNA-protein binding patterns. Furthermore, substrate kinetic and exon array analyses suggested a role for MB-COMT in catecholestrogen inactivation. The GENICA results were similar to the Mayo case-control observations, with ORs of 0.85 (95% CI = 0.72–1.00) and 0.85 (95% CI = 0.72–1.01) for the two SNPs. No significant effect was observed in the GESBC study. These studies demonstrated that two SNPs in the COMT distal promoter were associated with breast cancer risk reduction in 2 of 3 case-control studies, compatible with the results of functional genomic experiments, suggesting a role for MB-COMT in breast cancer risk.
Catechol O-methyltransferase; COMT; MB-COMT; S-COMT; breast cancer risk; genetic polymorphism; SNPs; functional genomics
Glutathione S-transferase P1 (GSTP1) is of importance for cancer research because of its role in detoxifying carcinogens, activating antineoplastic prodrugs, metabolizing chemotherapeutic agents, and because of its involvement in cell cycle and apoptosis regulation. Two common GSTP1 genetic polymorphisms have been studied extensively. However, the full range of GSTP1 genetic variation has not been systematically characterized in the absence of disease pathology. We set out to identify common GSTP1 polymorphisms in four ethnic groups, followed by functional genomic studies. All exons, splice junctions, and the 5′-flanking region of GSTP1 were resequenced using 60 DNA samples each from four ethnic groups. The 35 single nucleotide polymorphisms (SNPs) identified included six nonsynonymous SNPs and 17 previously unreported polymorphisms. GSTP1 variant allozymes were then expressed in COS-1 cells, and five displayed significantly altered levels of enzyme activity, one to 22% of the wild type (WT) activity. Four variant allozymes had Km values that differed significantly from that of the WT, and five showed altered levels of immunoreactive protein as compared to WT, with a significant correlation (r=0.79, p<0.007) between levels of immunoreactive protein and enzyme activity in these samples. In the Mexican-American population, five linked SNPs were significantly associated with GSTP1 mRNA expression, one of which was found by EMSA to alter protein binding. These studies have identified functionally significant genetic variation, in addition to the two frequently studied GSTP1 nonsynonymous SNPs, that may influence GSTP1′s contribution to carcinogen and drug metabolism, and – possibly – disease pathogenesis and/or drug response.
Glutathione S-transferases; glutathione transferase; GST; GSTP1; gene resequencing; functional genomics; genetic polymorphisms; SNPs; variant allozymes; expression regulation
We propose a histopathological classification system for hippocampal cell loss in patients suffering from mesial temporal lobe epilepsies (MTLE). One hundred and seventy-eight surgically resected specimens were microscopically examined with respect to neuronal cell loss in hippocampal subfields CA1–CA4 and dentate gyrus. Five distinct patterns were recognized within a consecutive cohort of anatomically well-preserved surgical specimens. The first group comprised hippocampi with neuronal cell densities not significantly different from age matched autopsy controls [no mesial temporal sclerosis (no MTS); n = 34, 19%]. A classical pattern with severe cell loss in CA1 and moderate neuronal loss in all other subfields excluding CA2 was observed in 33 cases (19%), whereas the vast majority of cases showed extensive neuronal cell loss in all hippocampal subfields (n = 94, 53%). Due to considerable similarities of neuronal cell loss patterns and clinical histories, we designated these two groups as MTS type 1a and 1b, respectively. We further distinguished two atypical variants characterized either by severe neuronal loss restricted to sector CA1 (MTS type 2; n = 10, 6%) or to the hilar region (MTS type 3, n = 7, 4%). Correlation with clinical data pointed to an early age of initial precipitating injury (IPI < 3 years) as important predictor of hippocampal pathology, i.e. MTS type 1a and 1b. In MTS type 2, IPIs were documented at a later age (mean 6 years), whereas in MTS type 3 and normal appearing hippocampus (no MTS) the first event appeared beyond the age of 13 and 16 years, respectively. In addition, postsurgical outcome was significantly worse in atypical MTS, especially MTS type 3 with only 28% of patients having seizure relief after 1-year follow-up period, compared to successful seizure control in MTS types 1a and 1b (72 and 73%). Our classification system appears suitable for stratifying the clinically heterogeneous group of MTLE patients also with respect to postsurgical outcome studies.