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Colorectal cancer is a heterogeneous disease with multiple genomic changes that influence the clinical management of patients; thus, the search for new molecular targets remains necessary. The aim of this study was to identify genetic variants in tumor tissues from Mexican patients with colorectal cancer, using massive parallel sequencing. A total of 4813 genes were analyzed in tumoral DNA from colorectal cancer patients, using the TruSight One Sequencing panel. From these, 192 variants with clinical associations were found distributed in 168 different genes, of which 46 variants had not been previous reported in the literature or databases, although genes harboring those variants had already been described in colorectal cancer. Enrichment analysis of the affected genes was performed using Reactome software; pathway over-representation showed significance for disease, signal transduction, and immune system subsets in all patients, while exclusive subsets such as DNA repair, autophagy, and RNA metabolism were also found. Those characteristics, whether individual or shared, could give tumors specific capabilities for survival, aggressiveness, or response to treatment. Our results can be useful for future investigations targeting specific characteristics of tumors in colorectal cancer patients. The identification of exclusive or common pathways in colorectal cancer patients could be important for better diagnosis and personalized cancer treatment.

The present study aimed to analyze the methylation pattern of the MIR200 family in the colorectal tissues and peripheral blood of colorectal cancer (CRC) patients. Previous informed consent, 102 samples of colorectal tissues (tumor and adjacent normal tissues) and 40 peripheral blood samples were collected from CRC patients. Additionally, we included a reference group of 40 blood samples. DNA extraction was done for colorectal tissues and peripheral blood. For methylation-specific PCR, we used bisulfite-treated DNA and controls for methylated and unmethylated DNA were included to each assay. PCR fragments were separated by 6% polyacrylamide gel electrophoresis. Methylation-positive and methylation-negative results were confirmed by bisulfite genomic sequencing technique. We analyzed 102 colorectal tissues and 40 blood samples from 51 CRC patients. MIR200B/MIR200A/MIR429 methylation analysis discloses no differences among tissues (p>0.05). However, MIR200C/MIR141 methylation showed differences between colorectal tissues and peripheral blood of CRC patients (p

La variación somática intraindividual (VSI) se describe como la diferencia genética entre los tejidos de un mismo individuo. La VSI se incrementa conforme avanza la edad y se asocia con alteraciones neurológicas, hematológicas e inmunes y, de manera especial, con cáncer, aunque puede no manifestar un fenotipo definido.1Para analizar la posible VSI en pacientes mexicanos con cáncer colorrectal (CCR), Yang et al.2 estudiaron el polimorfismo rs669 (c.2998 A>G, p.Ile1000Val) del gen A2M que codifica para la proteína alfa-2 macroglobulina, una inhibidora de proteasas involucrada en la progresión y proliferación del tumor. Esta variante se localiza cerca de un sitio tioéster, necesario para la función inhibidora de la proteína.

The ZNF217 gene, a potential oncogene amplified and overexpressed in several cancers including colorectal cancer (CRC), acts as a transcription factor that activates or represses target genes. The polymorphisms rs16998248 (T>A) and rs35720349 (C>T) in coronary artery disease have been associated with reduced expression of ZNF217. In this study, we analyzed the 2 polymorphisms in Mexican patients with CRC. Genotyping of rs16998248 and rs35720349 sites was performed by polymerase chain reaction-restriction fragment length polymorphism in 203 Mexican Mestizos, 101 CRC patients, and 102 healthy blood donors. Although no statistical differences regarding genotype and allele frequencies of ZNF217 polymorphisms were observed (P > 0.05), linkage disequilibrium was significant in CRC patients (r(2) = 0.39, P < 0.0001), as a result of reduced AC haplotype frequency. Thus, the AC haplotype may protect against CRC.

We analyzed a possible association between RUNX3 gene polymorphisms and haplotypes in Mexican patients with colorectal cancer (CRC). Genomic DNA samples were obtained from the peripheral blood of 176 Mexican patients with CRC at diagnosis and from 195 individuals that formed the control group. The polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism. Association was estimated by odds ratio (OR). The haplotypes and linkage disequilibrium were established using the Arlequin v3.5 software. We found that the RUNX3 polymorphisms analyzed were in Hardy-Weinberg equilibrium. The RUNX3 rs2236852 AA genotype and A allele showed association with CRC (OR = 0.39, 95%CI = 0.21-0.73, P < 0.01; OR = 0.65, 95%CI = 0.49-0.87, P < 0.01, respectively), while the rs6672420, rs11249206, and rs760805 polymorphisms did not show significant association with CRC. The TA haplotype (SNPs rs760805 and rs2236852) showed an increased risk for CRC (OR = 2.52, 95%CI = 1.47-4.30, P < 0.001). In conclusion, we found that the AA genotype and A allele of rs2236852 polymorphism confer a decreased CRC risk, while the TA haplotype appears to increase the risk of CRC development in Mexican patients.

Colorectal cancer (CRC) is characterized by enhanced expression and activity of several metalloproteinases (MMPs), including MMP13 and MMP7, which play an important role in tumor invasion and metastasis. The objective of this study was to analyze the association of functional MMP7-181A/G and MMP13-77A/G promoter polymorphisms with susceptibility to CRC in a Mexican population. Genomic DNA samples were obtained from peripheral blood of 102 CRC patients and 125 blood donors who were included as the control group. Identification of polymorphisms was based on polymerase chain reaction-restriction fragment length polymorphism methodology. The association was estimated by the odds ratio (OR) test. The results showed that MMP7-181A/G and MMP13-77A/G variants were associated with CRC. For MMP7-181A/G, the AA (P=0.02, OR=3.38, 95% confidence interval (CI)=1.16-9.84) and AG (P=0.01, OR=3.4, 95%CI=1.17-9.83) genotypes were associated with an increased risk of CRC. For MMP13-77A/G, the AA and AG genotypes were associated with CRC (AA genotype: P=0.04, OR=3.2, 95%CI=1.004-10.2; AG genotype: P=0.01, OR=4.08, 95%CI=1.3-13.07). In conclusion, AA and AG genotype carriers for both polymorphisms are at a higher risk of developing CRC in this Mexican population.

DNA repair proteins maintain DNA integrity; polymorphisms in genes coding for these proteins can increase susceptibility to colorectal cancer (CRC) development. We analyzed a possible association of MLH1 -93GA and 655AG and XRCC1 Arg194Trp and Arg399Gln polymorphisms with CRC in Mexican patients. Genomic DNA samples were obtained from peripheral blood of 108 individuals with CRC (study group) at diagnosis and 120 blood donors (control group) from Western Mexico; both groups were mestizos. The polymorphisms were detected by PCR-RFLP. Association was estimated by calculating the odds ratio (OR). We found that the MLH1 and XRCC1 polymorphisms were in Hardy- Weinberg equilibrium. The MLH1 655AG polymorphism in the 655G allele was associated with a 2-fold increase risk for CRC (OR = 2.04 and 95% confidence interval (95%CI) = 1.12-3.69; P0.01), while the MLH1 -93GA polymorphism allele was associated with a protective effect (OR = 0.60, 95%CI = 0.40-0.89; P = 0.01 in the -93A allele and OR = 0.32, 95%CI = 0.13-0.79; P = 0.01 in the AA genotype). The XRCC1 Arg194Trp and Arg399Gln polymorphisms did not show any significant associations. In conclusion, we found that MLH1 -93GA and 655AG polymorphisms are associated with CRC in Mexican patients.

We examined the influence of the Arg194Trp, Arg280His, and Arg399Gln polymorphisms of XRCC1 (X-ray repair cross-complementing group 1) on the development of childhood acute lymphoblastic leukemia (ALL) in 120 ALL patients and 120 controls in Mexico. All of them were genotyped for these polymorphisms, using polymerase chain reaction. No significant differences in allele and genotype frequencies for any polymorphism were observed between patients and controls. Estimation of haplotypes showed the eight expected haplotypes (A-H), seven of which were found in both patients and controls; haplotype A (Arg-Arg-Arg) was the most common, whereas haplotypes F and G were absent in patients and controls, respectively. Haplotype B (Trp-Arg-Arg) was found to be associated with an increased risk of ALL (odds ratio (OR) = 1.95, 95% confidence interval (CI) = 1.13-3.37; P = 0.016), particularly in males (OR = 2.65, 95%CI = 1.25-5.63; P = 0.01). Individually, the 194Trp, 280His, and 399Gln alleles were not associated with significantly increased risk for ALL in these Mexican children.

We report a boy with Down syndrome and leukemia who acquired uniparental isodisomy of chromosome 7q as a secondary chromosomal change during recurrence of the disease. His karyotype before therapy was 46,XY,der(1)t(1;1)(p36;q32),−7,+21c[17]/46,idem,del(9)(p22)[10], whereas at recurrence it was 46,XY,der(1)t(1;1)(p36;q32,−7,der(7)(qter→p22∼pter::q10→qter),del(9)(p22),+21c[13]/47,XY,+21c[2]. By using polymerase chain reaction amplification of D7S493 and D7S527 markers, we identified the loss of the maternal chromosome 7 with a consequent paternal isodisomy in the clone with dup7q. This rearrangement could be implicated in the progression of the disease by causing (1) nullisomy for a gene or genes located on 7p22→pter, (2) functional double doses of exclusively paternal expressed genes, and (3) restoration of the effects produced by haploinsufficiency of biparental expressed genes.