Singh Pooja

Polymorphic variations in IL-1β, IL-6 and IL-10 genes, their circulating serum levels and breast cancer risk in Indian women.

BACKGROUND Cytokines are known as important regulators of the entire gamut of cancer from initiation, invasion and metastasis. This fact and plethora of gene polymorphism data prompted us to investigate cytokine gene polymorphisms in breast cancer (BC) patients. METHODS Selected polymorphisms in the IL-1β [-511 T>C (rs16944) and +3954 C>T (rs1143634)]; IL-6 [-174 G>C (rs1800795)]; IL-10 [-1082 A>G (rs1800896), -819 T>C (rs1800871) and -592 A>C (rs1800872)] genes were genotyped in 200 BC patients and 200 healthy volunteers in a case-control study using PCR-RFLP and direct DNA sequencing techniques. Peripheral cytokine levels were measured using ELISA. Allele and genotype data were analyzed for significance of differences between cases and controls using Chi-Square [χ(2)] test. Two sided P-values of less than 0.05 were considered to be statistically significant. RESULTS Peripheral level of all three cytokines did not show any significant difference between cases and controls. Allele and genotype frequency of IL-1β [-511 T>C (rs16944)] did not show any difference between cases and controls. On the other hand mutant allele and genotype at IL-1β [+3954 C>T (rs1143634)] associated with increased risk of BC. This was also true for pre-menopausal cases and for mutant genotype in post-menopausal cases. Mutant allele and genotypes at IL-6 [-174 G>C (rs1800795)] appeared to be protective in nature such that controls had a higher frequency of both mutant alleles and genotypes. None of the three SNPs in IL-10 gene associated with risk of BC, except significant association of mutant allele and genotypes of -1082 A>G (rs1800896) polymorphism with postmenopausal BC. CONCLUSIONS Mutant allele and genotype at IL-1β [+3954 C>T (rs1143634)] site associated with increased BC risk, while mutant allele and genotypes at IL-6 [-174 G>C (rs1800795)] polymorphism appeared to be protective. Also, there was significant association of mutant allele and genotypes of IL-10 [-1082 A>G (rs1800896)] with postmenopausal BC. None of the other polymorphisms investigated appear to affect BC risk.

Strong Impact of TGF-β1 Gene Polymorphisms on Breast Cancer Risk in Indian Women: A Case-Control and Population-Based Study

Introduction TGF-β1 is a multi-functional cytokine that plays an important role in breast carcinogenesis. Critical role of TGF-β1 signaling in breast cancer progression is well documented. Some TGF-β1 polymorphisms influence its expression; however, their impact on breast cancer risk is not clear. Methods We analyzed 1222 samples in a candidate gene-based genetic association study on two distantly located and ethnically divergent case-control groups of Indian women, followed by a population-based genetic epidemiology study analyzing these polymorphisms in other Indian populations. The c.29C>T (Pro10Leu, rs1982073 or rs1800470) and c.74G>C (Arg25Pro, rs1800471) polymorphisms in the TGF-β1 gene were analyzed using direct DNA sequencing, and peripheral level of TGF-β1 were measured by ELISA. Results c.29C>T substitution increased breast cancer risk, irrespective of ethnicity and menopausal status. On the other hand, c.74G>C substitution reduced breast cancer risk significantly in the north Indian group (p = 0.0005) and only in the pre-menopausal women. The protective effect of c.74G>C polymorphism may be ethnicity-specific, as no association was seen in south Indian group. The polymorphic status of c.29C>T was comparable among Indo-Europeans, Dravidians, and Tibeto-Burmans. Interestingly, we found that Tibeto-Burmans lack polymorphism at c.74G>C locus as true for the Chinese populations. However, the Brahmins of Nepal (Indo-Europeans) showed polymorphism in 2.08% of alleles. Mean TGF-β1 was significantly elevated in patients in comparison to controls (p<0.001). Conclusion c.29C>T and c.74G>C polymorphisms in the TGF-β1 gene significantly affect breast cancer risk, which correlates with elevated TGF-β1 level in the patients. The c.29C>T locus is polymorphic across ethnically different populations, but c.74G>C locus is monomorphic in Tibeto-Burmans and polymorphic in other Indian populations.

Longer (TA) n Repeat but Not A49T and V89L Polymorphisms in SRD5A2 Gene May Confer Prostate Cancer Risk in South Indian Men

Testosterone is converted to 5 alpha-dihydrotestosterone (DHT) by 5 alpha-reductase enzyme, which is encoded by the SRD5A2 gene. DHT is the main androgen responsible for prostate growth. We have analyzed the complete coding region of the SRD5A2 gene in 87 histologically confirmed prostate cancer (PC) patients, 40 benign prostatic hyperplasia (BPH) cases, and 96 control samples from southern parts of India. The study revealed the A49T site to be monomorphic, the V89L site to be highly polymorphic, and the (TA)(n) repeat site to be polymorphic with only 2 alleles in our populations. The distribution of V89L alleles between PC cases and controls was not significantly different; however, (TA)(9) alleles distributed differently between the 2 groups. BPH cases exhibited alleles similar to controls at all polymorphic sites. The sequencing of the whole coding region did not reveal any other known or novel polymorphism in this gene. Our study emphasizes that the (TA)(9) allele might confer certain PC risk but that A49T and V89L polymorphisms do not confer PC risk in South Indian men.

MTHFR 677C>T Polymorphism and the Risk of Breast Cancer: Evidence from an Original Study and Pooled Data for 28031 Cases and 31880 Controls

Background Methylenetetrahydrofolate reductase (MTHFR) acts at an important metabolic point in the regulation of cellular methylation reaction. It assists in the conversion of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. The latter aids in remethylation of homocysteine to de novo methionine that is required for DNA synthesis. The objective of this study was to examine the effect of MTHFR 677 C>T polymorphism on the risk of breast cancer in the Indian sub-continent. Methods and Results We genotyped 677 C>T locus in 1096 individuals that were classified into cases (N=588) and controls (N=508). Genotype data were analyzed using chi-square test. No significant difference was observed in the distribution of genotypes between cases and controls in north Indian (P = 0.932), south Indian (P = 0.865), and pooled data (P = 0.680). To develop a consensus regarding the impact of 677C>T polymorphism on breast cancer risk, we also conducted a meta-analysis on 28031 cases and 31880 controls that were pooled from sixty one studies. The overall summary estimate upon meta-analysis suggested no significant correlation between the 677C>T substitution and breast cancer in the dominant model (Fixed effect model: OR = 0.97, P=0.072, Random effects model: OR = 0.96, P = 0.084) or the recessive model (Fixed effect model: OR = 1.05, P = 0.089; Random effects model: OR= 1.08, P= 0.067). Conclusion 677 C>T substitution does not affect breast cancer risk in the Indo-European and Dravidian populations of India. Analysis on pooled data further ruled out association between the 677 C>T polymorphism and breast cancer. Therefore, 677 C>T substitution does not appear to influence the risk of breast cancer.

CAG repeat length polymorphism in the androgen receptor gene and breast cancer risk: data on Indian women and survey from the world

We analyzed the length of the CAG repeats of the androgen receptor gene in Indian women with breast cancer, and compared the data with that of other populations across the world in an attempt to find a potential pattern of association. The study was undertaken on 1,408 individuals comprising 747 breast cancer patients and 661 control individuals recruited from three southern states of India: Andhra Pradesh, Tamil Nadu, and Karnataka. The comparison revealed no difference in mean length of the repeat between cases and controls in any of the three groups or in the analysis of pooled data. No significant difference between pre- and post-menopausal cases in any of the three groups or in the analysis of pooled data was observed. Most of the studies to date support either positive association (longer repeats—increased disease risk) or no association, and only 2 out of 20 studies reported negative association (inverse correlation between repeat length and disease risk). Comparison of these data with those from other populations revealed several interesting facts. Particularly notable is that repeat length shows association with breast cancer risk in a population-specific manner with most of the studies on American and Canadian women showing positive association, whereas those on Australian and Israeli women showing no association. Only one study had been conducted on other populations including Asians/South Asians; this restricted us from finding any patterns of association in these populations.

A mitochondrial DNA variant 10398G>A in breast cancer among South Indians: An original study with meta-analysis

The m.10398G>A polymorphism in the MT-ND3 gene has been linked to the manifestation of several neurodegenerative disorders and cancers. Several research groups have analyzed the association between m.10398G>A polymorphism and breast cancer; however, the results do not follow a consensus. We have studied this polymorphism in three Dravidian populations from South India. Analysis on 716 cases and 724 controls found no association between m.10398G>A polymorphism and breast cancer [OR = 0.916 (0.743-1.128); P = 0.409]. Menopausal stratification also revealed no significant association in either pre-menopausal or post-menopausal breast cancer groups. In addition, we undertook a meta-analysis on 16 study groups, comprising a total of 7202 cases and 7490 controls. The pooled odds ratio suggested no significant association of m.10398G>A substitution with breast cancer [OR = 1.016 (0.85-1.22); P = 0.86]. In conclusion, there is no evidence of association between m.10398G>A polymorphism and breast cancer risk among South Indian women. Meta-analysis suggested no overall correlation between this polymorphism and breast cancer risk.

SRD5A2 Gene Polymorphisms Affect the Risk of Breast Cancer

Androgens in breast cancer have been studied alone and in correlation with estrogens as estrogen to testosterone ratio. 5-α-reductase is one of the important enzymes participating in androgen metabolism, which affects androgen activity by affecting conversion of testosterone to dihydrotestosterone. We hypothesized that polymorphisms in the SRD5A2 gene (encoding 5-α-reductase) may affect breast cancer risk by affecting total androgen activity. Complete coding region of the SRD5A2 gene was sequenced in a group of 628 patients and 244 control samples from three southern states (Tamil Nadu, Andhra Pradesh, and Karnataka) of India. We observed three common polymorphisms in this gene; namely, A49T, V89L, and (TA)n repeats. A49T locus was monomorphic in the study population, but V89L showed a strong correlation with breast cancer (P = 0.03, OR = 1.40, CI = 1.02-1.91). (TA)0/(TA)9 and (TA)9/(TA)9 genotypes were at a lower risk of breast cancer (P = 0.01, OR = 0.64, CI = 0.46-0.90). We conclude that SRD5A2 genotypes significantly affect breast cancer risk in the South Indian populations.

RAD51 135G>C substitution increases breast cancer risk in an ethnic-specific manner: a meta-analysis on 21236 cases and 19407 controls

RAD51 is a homolog of bacterial RecA protein, which plays an important role in preserving stability of the genome. RAD51 interacts with BRCA1 and BRCA2 for homologous recombination repair. A functional polymorphism (135G > C) in the RAD51 gene has been a subject of great interest, which is evidenced by at least 28 case-control studies and eight meta-analyses undertaken on this polymorphism till now. We undertook a meta-analysis on RAD51 135G > C data for 21236 cases and 19407 controls pooled from 28 studies on breast cancer in women. Pooled data analysis suggested a significant association of the substitution with breast cancer in the recessive model (GG + GC versus CC) and in the co-dominant models comparing GG versus CC and GC versus CC. Analysis of the results suggested that ‘CC’ genotype is a significant breast cancer risk factor in comparison to ‘GG’ and ‘GC’ genotypes. We also undertook pooled analyses on different ethnic groups and found that ‘CC’ was a strong risk factor in Caucasians, but not in East-Asians and populations of mixed ethnicity. In conclusion, the RAD51 135G > C substitution in the homozygous form (CC) increases the risk of breast cancer in an ethnic-specific manner.

c.29C>T polymorphism in the transforming growth factor-β1 (TGFB1) gene correlates with increased risk of urinary bladder cancer.

TGF-β1 is a pleiotropic cytokine, which plays a dual role in tumor development. In the early stages, it inhibits the growth of tumor while in the late stages of carcinoma, it promotes tumor growth. The purpose of this study was to analyze the distribution of the TGFB1 gene polymorphisms between cases and controls so as to assess their correlation with bladder cancer risk. This study included 237 cases of urinary bladder cancer and 290 age matched controls from the same ethnic background. Three polymorphisms in the TGFB1 gene, c.29C>T (rs-1800470), c.74G>C (rs-1800471) and +140A>G (rs-13447341), were analyzed by direct DNA sequencing. Statistical analyses revealed no significant differences in the demographical data, except that the frequencies of smokers and non-vegetarians were higher in the cases. Eighty percent of the bladder cancer patients had superficial transitional cell carcinoma, and 53.16% and 26.31% of the patients were in grade I and grade II, respectively. We found that c.29C>T substitution increased the risk of bladder cancer significantly and recessive model of analysis was the best fitted model (p=0.004; OR=1.72 95% CI 1.18-2.50). A significantly higher risk in the recessive form was also suggested by co-dominant analysis showing that the homozygous form (TT) was a significant risk factor in comparison to CC and CT genotypes. The other two polymorphisms, c.74G>C (p=0.18, OR=0.67 95% CI 0.37-1.21) and +140A>G (p=0.416, OR=0.77 95% CI 0.41-1.45) did not affect the risk of urinary bladder cancer. In conclusion, we found that the TGFB1 c.29C>T substitution increases the risk of bladder cancer significantly while c.74G>C and +140A>G polymorphisms do not affect the risk.

G708E Mutation in the Androgen Receptor Results in Complete Loss of Androgen Function

End-organ resistance to androgens, called androgen insensitivity syndrome (AIS), is a rare disorder. The most common cause of AIS is mutations(s) in the androgen receptor (AR) gene; however, a significant number of these mutations have not been functionally analyzed. In the present study, we analyzed a case of complete AIS for mutations in the AR gene. Sequencing of the entire coding region of the AR gene revealed a 2650G>A mutation (mRNA sequence reference) in exon 4 of the gene, resulting in replacement of glycine with glutamate at codon 708 in the ligand-binding domain of the AR protein. The mutation was absent in 200 normal male individuals analyzed to look at its occurrence in general population. In vitro androgen-binding and transactivation assays showed that the mutation resulted in approximately 65% loss of ligand binding and almost complete loss of transactivation function. Complete AIS in this individual was due to a G708E substitution in the AR protein.