RESUMO
Mitochondrial displacement loop (D-loop) is the hot spot for mitochondrial DNA (mtDNA) alterations which influence the generation of cellular reactive oxygen species. In the present study, we sequenced the entire mitochondrial D-loop region (1124 bp) of colorectal cancer (CRC) patients (n = 174) and controls (n = 170) of south Indian origin to identify significant mutations/polymorphisms. Our results showed 152 polymorphisms in the D-loop region of patients and/or controls. Polymorphisms were predominantly located in hypervariable region I (54.6%) than in II (45.4%) of D-loop region. The frequencies of 310'C' insertion (p = 0.0078), T16189C (p = 0.0097) variants and 310'C'ins/16189C haplotype (p = 0.0029) were significantly higher in cases than in controls. Furthermore, strong linkage disequilibrium was observed between nucleotide position 310 and 16189 in cases (D'=0.68) as compared with controls (D'=0.27). In conclusion, mitochondrial D-loop sequence alterations may constitute inherent risk factor for CRC.
Assuntos
Neoplasias Colorretais/genética , DNA Mitocondrial/genética , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA/métodos , População Branca/genética , DNA Mitocondrial/química , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Humanos , Índia , Desequilíbrio de Ligação , Masculino , Mitocôndrias/genéticaRESUMO
Mitochondrial displacement loop (D-loop) is a hot spot for mitochondrial DNA (mtDNA) alterations that effects cellular reactive oxygen species (ROS) generation. Manganese-superoxide dismutase (Mn-SOD) is a major antioxidant enzyme that protects cells from ROS-mediated damage. In the present study, we investigated the relationship between sequence alterations of mitochondrial D-loop and Mn-SOD expression in colorectal cancer (CRC). Genotyping of entire mitochondrial D-loop (1124 bp) was carried out on mtDNA of analogous tumor and normal tissues from 35 CRC patients of south Indian origin by PCR-sequencing analysis. Tumor-specific large-scale mtDNA deletions and Mn-SOD expression was analyzed by PCR and Western blot analysis, respectively. We identified 87 polymorphisms in the D-loop region of tumor and/or control tissues. Polymorphisms were predominantly located in hypervariable region I (67.9 %) than in II (32.1 %) of D-loop. Significantly increased mtDNA microsatellite instability (mtMSI) [310'C' insertion (P = 0.00001) and T16189C (P = 0.0007)] and elevated Mn-SOD expression was observed in tumor tissues compared with controls. Interestingly, mtMSI was significantly high in tumors with Mn-SOD overexpression. Tumor-specific large-scale mtDNA deletions were not observed in CRC tissues. In conclusion, mtMSI and Mn-SOD overexpression are a common event in CRC. The analysis of mtMSI and/or Mn-SOD expression might help to identify patients at high risk for disease outcome, thereby helping to refine therapeutic decisions in CRC.
Assuntos
Adenocarcinoma/enzimologia , Adenocarcinoma/genética , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/genética , DNA Mitocondrial/genética , Superóxido Dismutase/biossíntese , Adenocarcinoma/patologia , Adulto , Idoso , Western Blotting , Neoplasias Colorretais/patologia , Feminino , Genótipo , Humanos , Masculino , Instabilidade de Microssatélites , Pessoa de Meia-Idade , Reação em Cadeia da PolimeraseRESUMO
Cyclin D1 (CCND1) and E-cadherin (CDH1) are two important genes of the ß-catenin/LEF pathway that is involved in tumorigenesis of various cancers including colorectal cancer (CRC). However, studies of the association between genetic variants of these two genes and CRC have shown conflicting results. We conducted a genetic association study in South Indian population (cases, 103; controls, 107) to assess the association of CCND1 870G/A and CDH1 -160C/A single nucleotide polymorphisms (SNPs) with CRC risk. Genotyping of SNPs was performed by PCR sequencing analysis. Haplotype frequencies for multiple loci and the standardized disequilibrium coefficient (D') for pair-wise linkage disequilibrium (LD) were assessed by Haploview Software. In addition, to better understand the role of CCND1 and CDH1 in the pathophysiology of CRC, the expression pattern was evaluated in analogous tumor and adjacent normal tissues from 23 CRC patients by Western blot analysis. The frequencies of CCND1 870A/A (P = 0.045) genotype, CDH1 -160A allele (P = 0.042), and 870A/-160A haplotype (P = 0.002) were significantly higher in patients as compared with controls. Strong LD was observed between 870G/A and -160C/A SNPs in cases (D' = 0.76) as compared to controls (D' = 0.32). Furthermore, elevated CCND1 and diminished CDH1 expression was observed in tumor tissue as compared with analogous normal tissue of CRC patients. Interestingly, advanced-stage tumors showed wider expression alterations than in early-stage tumors. In conclusion, CCND1 870G/A and CDH1 -160C/A SNPs may modify the risk of CRC susceptibility in South Indian population. In addition, elevated CCND1 and diminished CDH1 expression appears to be useful prognostic markers for CRC.
Assuntos
Caderinas/genética , Neoplasias Colorretais/genética , Ciclina D1/genética , Predisposição Genética para Doença , Variação Genética , Adulto , Idoso , Alelos , Estudos de Casos e Controles , Neoplasias Colorretais/patologia , Feminino , Genótipo , Haplótipos , Humanos , Índia , Desequilíbrio de Ligação , Masculino , Pessoa de Meia-Idade , Invasividade Neoplásica , Estadiamento de Neoplasias , Polimorfismo de Nucleotídeo Único , Fatores de Risco , Análise de Sequência de DNARESUMO
BACKGROUND: Mitochondrial displacement loop (D-loop) is the hot spot for mitochondrial DNA (mtDNA) alterations which influence the generation of cellular reactive oxygen species (ROS). Association of D-loop alterations with breast cancer has been reported in few ethnic groups; however none of the reports were documented from Indian subcontinent. METHODOLOGY: We screened the entire mitochondrial D-loop region (1124 bp) of breast cancer patients (nâ=â213) and controls (nâ=â207) of south Indian origin by PCR-sequencing analysis. Haplotype frequencies for significant loci, the standardized disequilibrium coefficient (D') for pair-wise linkage disequilibrium (LD) were assessed by Haploview Software. PRINCIPAL FINDINGS: We identified 7 novel mutations and 170 reported polymorphisms in the D-loop region of patients and/or controls. Polymorphisms were predominantly located in hypervariable region I (60%) than in II (30%) of D-loop region. The frequencies of 310'C' insertion (Pâ=â0.018), T16189C (Pâ=â0.0019) variants and 310'C'ins/16189C (Pâ=â0.00019) haplotype were significantly higher in cases than in controls. Furthermore, strong LD was observed between nucleotide position 310 and 16189 in controls (D'â=â0.49) as compared to patients (D'â=â0.14). CONCLUSIONS: Mitochondrial D-loop alterations may constitute inherent risk factors for breast cancer development. The analysis of genetic alterations in the D-loop region might help to identify patients at high risk for bad progression, thereby helping to refine therapeutic decisions in breast cancer.
Assuntos
Neoplasias da Mama/genética , DNA Mitocondrial/genética , Sequências Reguladoras de Ácido Nucleico , Sequência de Bases , Estudos de Casos e Controles , Análise Mutacional de DNA , Feminino , Frequência do Gene , Estudos de Associação Genética , Haplótipos , Humanos , Índia , Desequilíbrio de Ligação , Mutagênese Insercional , Mutação Puntual , Polimorfismo de Nucleotídeo Único , Fatores de RiscoRESUMO
The objective of the present study was to investigate the association between TP53 gene single nucleotide polymorphisms (SNPs) and colorectal cancer (CRC) predisposition in south Indian population and to evaluate the role of TP53 expression in the pathophysiology of CRC. A genetic association study was conducted in 103 CRC cases and 107 controls of south Indian origin. We genotyped ten selected TP53 SNPs by polymerase chain reaction-sequencing analysis. Haplotype frequencies for multiple loci and the standardized disequilibrium coefficient (D') for pairwise linkage disequilibrium (LD) were assessed by Haploview Software. In addition, to better understand the role of TP53 in the pathophysiology of CRC, the expression pattern was evaluated in analogous tumor and normal tissues from 23 CRC patients by Western blot analysis. The frequencies of Pro72Pro (P = 0.0033) genotype and Ser47/Pro72 (P = 0.00171) haplotype were significantly higher in patients as compared to controls. Strong LD was observed between codon 47 and 72 in cases (D' = 0.32) as compared to controls (D' = 0.21). The polymorphism was not observe at the remaining eight SNPs loci analyzed. Furthermore, increased TP53 expression was observed in tumor tissue than in analogous normal tissue of CRC patients. Interestingly, advanced stage tumors showed more elevated TP53 expression compared to early stage tumors. In conclusion, the TP53 Pro72Pro genotype and Ser47/Pro72 haplotype has an increased risk for CRC predisposition in south Indian population. In addition, elevated TP53 expression appears to be useful prognostic marker for CRC.