Dhruva Kumar Mishra

Is reduced CAG repeat length in androgen receptor gene associated with risk of prostate cancer in Indian population

Shorter CAG repeats in androgen receptor (AR) gene have been found to be associated with an increased risk of prostate cancer (CaP). Ethnic variations in CAG repeat length may contribute to varying risks in different populations. To evaluate the prognostic significance of androgen receptor (AR) CAG repeats in Indian population for CaP, genomic DNA from 113 CaP, 57 benign prostate hyperplasia (BPH) patients and 133 normal healthy controls were examined by using a PCR‐based GeneScan analysis. The mean number of CAG repeat in CaP was significantly lower as compared to the healthy controls (20.26 vs 22.98; p = 0.016). The odds ratio for CaP was 2.96 (p < 0.01), when individuals with short CAG repeat (≤22) were compared with those having longer repeats (>22). A significant association was also observed between short CAG repeat and young age at diagnosis (OR 2.18; p = 0.04). The mean CAG repeat was not significantly different in BPH and healthy controls; however, BPH patients showed a tendency towards short CAG repeats. Thus, our results show that CAG repeat polymorphism in AR gene is significantly associated with CaP risk, suggesting that AR CAG polymorphism may act as a risk modifier to CaP in Indian population.

Association of Vitamin D Receptor Gene Polymorphism and Risk of Prostate Cancer in India

Introduction: Vitamin D plays an important role in the proliferation and differentiation of normal and malignant cells. In several studies polymorphism in the vitamin D receptor (VDR) gene has been reported to be associated with prostate cancer (CaP). The rationale of this study was to determine the association between the VDR (Fok-I) polymorphism and the risk of developing CaP. Materials and Methods: Polymorphism was detected by the polymerase chain reaction (PCR)-restriction fragment length polymorphism method in 128 CaP patients (age range 43–89 years) and 147 age-matched controls (age range 42–91 years). PCR products were designated as F or f allele according to the absence or presence of a restriction site. Results and Conclusions: The frequencies of the FF, Ff and ff genotypes were 60.9, 35.2 and 3.9% in CaP patients and 42.2, 46.9 and 10.9% in healthy controls, respectively. The genotype frequency distribution between CaP and the control group was statistically significant (p = 0.003). However, the distribution of genotypes was not significantly associated with the Gleason score. The present study thus demonstrates that the FF genotype (or F allele) of the VDR gene plays an important role in determining the risk of CaP and could be postulated as a good candidate genetic marker.

Is there an inter-relationship between prostate specific antigen, kallikrein-2 and androgen receptor gene polymorphisms with risk of prostate cancer in north Indian population?

Androgen receptor (AR) and kallikrein (KLK-2) regulates the PSA (prostate specific antigen) transcription and activation, respectively. We investigated the individual and combined risk of KLK-2, PSA and AR gene polymorphism in histologically confirmed CaP patients and healthy controls from north India. DNA was extracted from peripheral blood leucocytes pellet of 277 subjects. AR repeats analysis was done by PCR-Genscan method. PSA and KLK-2 were genotyped by PCR-RFLP method. Kruskal-Wallis test and logistic regression was applied for mean comparison and risk determination. A significant association for CaP risk was observed with short AR-CAG repeats (OR=3.36, p<0.001) and CC genotype of KLK-2 (OR=2.78, p=0.031), however, no association was found with PSA and AR-GGN repeat polymorphism. PSA/GG genotype was significantly associated with higher Gleason score (> or =7) of tumor (OR=6.23, p<0.01). No association was observed with other confounding variables such as PSA and age with any of these polymorphisms. Thus, we hypothesize that these polymorphisms may influence the etiology of CaP and may have the probability to become appropriate marker either independently or in combination. The combined information on serum PSA level, PSA (G/A), KLK-2 (C/T) genotypes and AR (CAG; GGN repeat) may assist in the deterrence of unnecessary biopsies.

POLYMORPHISMS IN THE VITAMIN D RECEPTOR AND THE ANDROGEN RECEPTOR GENE ASSOCIATED WITH THE RISK OF UROLITHIASIS

Transcriptional activity of the vitamin D receptor (VDR) gene is regulated by androgen receptor (AR) gene and both are associated with renal stone formation. We examined gene polymorphisms of VDR (PCR-RFLP) and AR (GeneScan analysis) in 125 stone formers and 150 controls from north India. Genotype Ff of Fok-I and Tt of Taq-I demonstrated significantly higher risk (P<0.001, OR=3.559 and P=0.019, 1.830 respectively). Variant f allele exhibited 1.7-folds higher risk. Ff of Fok-I and Aa of Apa-I gene polymorphism showed higher risk in males only. Mean CAG repeat was significantly higher in hypercalciuric patients as compared to normocalciuric (mean=21.62 ± 3.384 vs. 20.11 ± 3.182; P=0.034). Combined effects 1.8-folds higher risk in patients with Tt genotype of Taq-I and short CAG repeat. Thus, association of FokI and TaqI VDR gene polymorphisms suggest VDR as an important genetic marker for urolithiasis. Further, patients with combination of Tt of Taq-I and short CAG repeat were at higher risk for stone formation.

Nonprogressive juvenile-onset spinal muscular atrophy: A clinico-radiological and CAG repeat study of androgen receptor gene.

BACKGROUND Occurrence of nonprogressive juvenile-onset spinal muscular atrophy (SMA) predominantly in males suggests a possibility of X-linked disorder but there is no such report addressing this problem. AIMS To evaluate CAG repeat expansion of androgen receptor (AR) gene in patients with nonprogressive juvenile-onset SMA. SETTING Tertiary medical teaching institute. SUBJECTS AND METHODS Patients fulfilling the diagnostic criteria of nonprogressive juvenile-onset SMA were included. Detailed clinical evaluation and pedigree charting were done in all. Nerve conduction study, electromyography and cervical spinal MRI were carried out. From peripheral venous blood, DNA was separated and AR gene CAG repeat exon polymorphism was assayed using polymerase chain reaction (PCR) in conjugation with genotyping and Gene scan soft ware. Number of CAG repeats was compared with normal controls. RESULTS 25 patients with nonprogressive juvenile-onset SMA from 24 families were included and their mean age was 22.2 years. Age at the time of disease onset ranged between 15 and 30 years with a mean duration of illness 2.6 years. None of the patients had testicular atrophy or gynecomastia. C7-T1 myotomal wasting and weakness although was unilateral to begin with but became bilateral in 16 and 4 more patients had evidences of subclinical involvement of the other side as revealed by EMG. Spinal MRI revealed cord atrophy at C6-8 vertebral level in 16 patients. CAG repeat study of AR gene was carried out in 16 patients. The number of CAG repeats in patients ranged between 15 and 39 (median 21) which were within the normal range. CONCLUSION Abnormal CAG repeat expansion of AR gene is not found in patients with nonprogressive juvenile-onset SMA.