X-ray cross-complementing group 1 and thymidylate synthase polymorphisms might predict response to chemoradiotherapy in rectal cancer patients.

PURPOSE: 5-Fluorouracil-based chemoradiotherapy before total mesorectal excision is currently the standard treatment of Stage II and III rectal cancer patients. We used known predictive pharmacogenetic biomarkers to identify the responders to preoperative chemoradiotherapy in our series. METHODS AND MATERIALS: A total of 93 Stage II-III rectal cancer patients were genotyped using peripheral blood samples. The genes analyzed were X-ray cross-complementing group 1 (XRCC1), ERCC1, MTHFR, EGFR, DPYD, and TYMS. The patients were treated with 225 mg/m(2)/d continuous infusion of 5-fluorouracil concomitantly with radiotherapy (50.4 Gy) followed by total mesorectal excision. The outcomes were measured by tumor regression grade (TRG) as a major response (TRG 1 and TRG 2) or as a poor response (TRG3, TRG4, and TRG5). RESULTS: The major histopathologic response rate was 47.3%. XRCC1 G/G carriers had a greater probability of response than G/A carriers (odds ratio, 4.18; 95% confidence interval, 1.62-10.74, p = .003) Patients with polymorphisms associated with high expression of thymidylate synthase (2R/3G, 3C/3G, and 3G/3G) showed a greater pathologic response rate compared with carriers of low expression (odds ratio, 2.65; 95% confidence interval, 1.10-6.39, p = .02) No significant differences were seen in the response according to EGFR, ERCC1, MTHFR_C677 and MTHFR_A1298 expression. CONCLUSIONS: XRCC1 G/G and thymidylate synthase (2R/3G, 3C/3G, and 3G/3G) are independent factors of a major response. Germline thymidylate synthase and XRCC1 polymorphisms might be useful as predictive markers of rectal tumor response to neoadjuvant chemoradiotherapy with 5-fluorouracil.

Evolutionary analyses of entire genomes do not support the association of mtDNA mutations with Ras/MAPK pathway syndromes.

BACKGROUND: There are several known autosomal genes responsible for Ras/MAPK pathway syndromes, including Noonan syndrome (NS) and related disorders (such as LEOPARD, neurofibromatosis type 1), although mutations of these genes do not explain all cases. Due to the important role played by the mitochondrion in the energetic metabolism of cardiac muscle, it was recently proposed that variation in the mitochondrial DNA (mtDNA) genome could be a risk factor in the Noonan phenotype and in hypertrophic cardiomyopathy (HCM), which is a common clinical feature in Ras/MAPK pathway syndromes. In order to test these hypotheses, we sequenced entire mtDNA genomes in the largest series of patients suffering from Ras/MAPK pathway syndromes analyzed to date (n = 45), most of them classified as NS patients (n = 42). METHODS/PRINCIPAL FINDINGS: The results indicate that the observed mtDNA lineages were mostly of European ancestry, reproducing in a nutshell the expected haplogroup (hg) patterns of a typical Iberian dataset (including hgs H, T, J, and U). Three new branches of the mtDNA phylogeny (H1j1, U5b1e, and L2a5) are described for the first time, but none of these are likely to be related to NS or Ras/MAPK pathway syndromes when observed under an evolutionary perspective. Patterns of variation in tRNA and protein genes, as well as redundant, private and heteroplasmic variants, in the mtDNA genomes of patients were as expected when compared with the patterns inferred from a worldwide mtDNA phylogeny based on more than 8700 entire genomes. Moreover, most of the mtDNA variants found in patients had already been reported in healthy individuals and constitute common polymorphisms in human population groups. CONCLUSIONS/SIGNIFICANCE: As a whole, the observed mtDNA genome variation in the NS patients was difficult to reconcile with previous findings that indicated a pathogenic role of mtDNA variants in NS.

Use of a comprehensive panel of biomarkers to predict response to a fluorouracil-oxaliplatin regimen in patients with metastatic colorectal cancer.

AIM: Polymorphisms in the metabolism, detoxification or DNA repair pathways have been proposed as potential predictors of response to 5-fluorouracil and oxaliplatin. We have studied the predictive value of a set of germline genetic polymorphisms in metastatic colorectal cancer patients treated with mFolfox-6. MATERIALS & METHODS: A total of 72 patients, comprising 50 men (69.4%) and 22 women (30.6%), were included after the signing of an informed consent form. Median age was 65.5 years (range: 32-80). All participants received mFolfox-6. DNA was extracted from peripheral blood samples and genotyped by direct sequencing, SnapShot(®) and multiplex PCR techniques. Eight polymorphisms within six genes were investigated: TS 5´-UTR (variable number tandem repeat + G/C), TS 3´-UTR (TS1494del6); MTHFR C677T and A1298C; GSTP1 I105V; ERCC1 C118T; XPD Lys751Gln and XRCC1 Arg399Gln. Association was evaluated by univariate analysis, and Cox regression and Kaplan-Meier assessed survival. The local ethics committee approved the pharmacogenetic study protocol and all subjects signed an informed consent before participating in the study. RESULTS: The sample was in Hardy-Weinberg equilibrium. Only XPD Lys751Gln was found to be significantly associated with a favorable progression-free survival (PFS). Median PFS for XPD Lys751Gln patients (n = 33) was 16 months (95% CI: 9.2-22.7), 10 months (95% CI: 6.1-13.9) for Gln/Gln (n = 11) and 8 months (95% CI: 5.8-10.2) for Lys/Lys (n = 28), p = 0.019. The increased risk of progression was: 1.93 (95% CI: 1.13-13.30; p = 0.017) for Lys/Lys and 2.1 (95% CI: 1.01-4.22; p = 0.047) for Gln/Gln. Patients with one or two Val alleles of GSTP1 tended to a lower risk of progression compared with Ile/Ile homozygotes, p = 0.067. When XPD Lys751Gln and GSTP1 were analyzed jointly, patients who carried one or two favorable genotypes, XPD Lys751Gln and Val, had a longer median PFS: 11 months (95% CI: 7.4-14.6) compared with six (95% CI: 4.6-7.4) with unfavorable genotypes, p < 0.001. CONCLUSION: In metastatic colorectal cancer patients treated with mFolfox-6, the combination of haplotype XPD Lys751Gln-GSTP1 105Val seems to predict the risk of progression.

Pharmacogenetic analysis in neoadjuvant chemoradiation for rectal cancer: high incidence of somatic mutations and their relation with response.

AIMS: The identification of predictive markers of response to chemoradiotherapy treatment remains a promising approach for patient management in order to obtain the best response with minor side effects. Initially, we investigated whether the analysis of several markers previously studied and others not yet evaluated could predict response to 5-fluorouracil- and capecitabine-based neoadjuvant treatment in locally advanced rectal cancer. METHODS & MATERIALS: We studied germline and tumoral samples of 65 stage II/III rectal patients. A panel of pharmacogenetic markers was genotyped in paired peripheral blood samples and rectal cancer tumors. RESULTS: Our results seem to confirm the previously described association of thymidylate synthase and the prediction of chemoradiotherapy response in rectal cancer. However, it failed to confirm the clinical utility proposed for XRCC1, ERCC1, ERCC2, MTHFR and EGFR polymorphisms in blood/germline samples. Subsequently, with the aim of improving prediction of individual response and assessing the role of studied polymorphisms in response to treatment, we determined if changes in tumor response to these markers could predict clinical outcome. We found a high degree of changes between germline and tumor samples, mainly somatic mutations without microsatellite instability, and a minor frequency of loss-of-heterozygosity events. In tumoral samples, XRCC1 appeared to be significantly associated (p = 0.006) with downstaging of the tumor (odds ratio: 7.93; 95% CI: 1.03-60.83), but the increasing of TYMS low-expression alleles contradict the previous results observed in germline samples. CONCLUSION: The detection of somatic mutations in rectal cancer tumors led us to re-evaluate the utility of the tests performed in blood samples for these polymorphisms in rectal cancer. Furthermore, studies aimed at assessing the influence of pharmacogenetic markers in treatment response performed in blood samples should take into account the particular pattern of hypermutability present in each tumor type. We hypothesize that different patterns of hypermutability present in each tumor type would be related to the different results in association studies related to response to the treatment.