Biomedical subjects

A Sengupta

Publications and source records attributed to A Sengupta.

At least 19 recordsLinked to original sources

PubMed2006

Interplay between human papilloma virus infection and p53 gene alterations in head and neck squamous cell carcinoma of an Indian patient population.

AIM: To investigate the complex interplay between human papilloma virus (HPV) infection and p53 gene alteration in 92 head and neck squamous cell carcinoma (HNSCC) and 28 leukoplakia samples from eastern India. METHODS: DNA isolated from the patient samples was subjected to HPV detection, loss of heterozygosity (LOH) analysis of the chromosome 17p region harbouring p53, genotyping at the p53 codon 72 locus and sequencing of the entire p53 gene to identify somatic mutations. Codon 72 heterozygotes carrying the p53 mutation were further cloned and resequenced to identify the allele harbouring the mutation. RESULTS: HPV positivity in the HNSCC samples was 69%; 21% of the HNSCC were found to harbour p53 mutations in the coding region of the gene. The absence of the p53 mutation in HPV positive tumours was statistically significant compared to the HPV negative tumours (p = 0.01), but the same did not hold true for p53 LOH (p = 1.0). Among the germline p53 codon 72 heterozygotes, the Pro allele was preferentially lost (p = 0.02) while the Arg allele was mutated in the majority of cases. The risk of HPV mediated tumourigenesis increased with the increase in number of Arg alleles at the codon 72 locus. CONCLUSION: It is proposed that genetic and epigenetic alteration of p53 follow distinct pathways during the development of HNSCC from normal epithelium via dysplasia. The p53 mutation and HPV mediated p53 inactivation possibly constitute two independent pathways of tumourigenesis.

Adult↗

PubMed2006

Gene expression profiling reveals the profound upregulation of hypoxia-responsive genes in primary human astrocytes.

Oxygen is vital for the development and survival of mammals. In response to hypoxia, the brain initiates numerous adaptive responses at the organ level as well as at the molecular and cellular levels, including the alteration of gene expression. Astrocytes play critical roles in the proper functioning of the brain; thus the manner in which astrocytes respond to hypoxia is likely important in determining the outcome of brain hypoxia. Here, we used microarray gene expression profiling and data-analysis algorithms to identify and analyze hypoxia-responsive genes in primary human astrocytes. We also compared gene expression patterns in astrocytes with those in human HeLa cells and pulmonary artery endothelial cells (ECs). Remarkably, in astrocytes, five times as many genes were induced as suppressed, whereas in HeLa and pulmonary ECs, as many as or more genes were suppressed than induced. More genes encoding hypoxia-inducible functions, such as glycolytic enzymes and angiogenic growth factors, were strongly induced in astrocytes compared with HeLa cells. Furthermore, gene ontology and computational algorithms revealed that many target genes of the EGF and insulin signaling pathways and the transcriptional regulators Myc, Jun, and p53 were selectively altered by hypoxia in astrocytes. Indeed, Western blot analysis confirmed that two major signal transducers mediating insulin and EGF action, Akt and MEK1/2, were activated by hypoxia in astrocytes. These results provide a global view of the signaling and regulatory network mediating oxygen regulation in human astrocytes.

Algorithms↗

PubMed2005

Aromatic interactions in tryptophan-containing peptides: crystal structures of model tryptophan peptides and phenylalanine analogs.

The crystal structures of the peptides, Boc-Leu-Trp-Val-OMe (1), Ac-Leu-Trp-Val-OMe (2a and 2b), Boc-Leu-Phe-Val-OMe (3), Ac-Leu-Phe-Val-OMe (4), and Boc-Ala-Aib-Leu-Trp-Val-OMe (5) have been determined by X-ray diffraction in order to explore the nature of interactions between aromatic rings, specifically the indole side chain of Trp residues. Peptide 1 adopts a type I beta-turn conformation stabilized by an intramolecular 4-->1 hydrogen bond. Molecules of 1 pack into helical columns stabilized by two intermolecular hydrogen bonds, Leu(1)NH...O(2)Trp(2) and IndoleNH...O(1)Leu(1). The superhelical columns further pack into the tetragonal space group P4(3) by means of a continuous network of indole-indole interactions. Peptide 2 crystallizes in two polymorphic forms, P2(1) (2a) and P2(1)2(1)2(1) (2b). In both forms, the peptide backbone is extended, with antiparallel beta-sheet association being observed in crystals. Extended strand conformations and antiparallel beta-sheet formation are also observed in the Phe-containing analogs, Boc-Leu-Phe-Val-OMe (3) and Ac-Leu-Phe-Val-OMe (4). Peptide 5 forms a short stretch of 3(10)-helix. Analysis of aromatic-aromatic and aromatic-amide interactions in the structures of peptides, 1, 2a, 2b are reported along with the examples of 14 Trp-containing peptides from the Cambridge Crystallographic Database. The results suggest that there is no dramatic preference for a preferred orientation of two proximal indole rings. In Trp-containing peptides specific orientations of the indole ring, with respect to the preceding and succeeding peptide units, appear to be preferred in beta-turns and extended structures.

Crystallization↗

PubMed2005

Tryptophan-containing peptide helices: interactions involving the indole side chain.

Two designed peptide sequences containing Trp residues at positions i and i + 5 (Boc-Leu-Trp-Val-Ala-Aib-Leu-Trp-Val-OMe, 1) as well as i and i + 6 (Boc-Leu-Trp-Val-Aib-Ala-Aib-Leu-Trp-Val-OMe, 2) containing one and two centrally positioned Aib residues, respectively, for helix nucleation, have been shown to form stable helices in chloroform solutions. Structures derived from nuclear magnetic resonance (NMR) data reveal six and seven intramolecularly hydrogen-bonded NH groups in peptides 1 and 2, respectively. The helical conformation of octapeptide 1 has also been established in the solid state by X-ray diffraction. The crystal structure reveals an interesting packing motif in which helical columns are stabilized by side chain-backbone hydrogen bonding involving the indole Nepsilon1H of Trp(2) as donor, and an acceptor C=O group from Leu(6) of a neighboring molecule. Helical columns also associate laterally, and strong interactions are observed between the Trp(2) and Trp(7) residues on neighboring molecules. The edge-to-face aromatic interactions between the indoles suggest a potential C-H...pi interaction involving the Czeta3H of Trp(2). Concentration dependence of NMR chemical shifts provides evidence for peptide association in solution involving the Trp(2) Nepsilon1H protons, presumably in a manner similar to that observed in the crystal.

Crystallography, X-Ray↗

PubMed2004

Inhibition of DMBA/croton oil-induced two-stage mouse skin carcinogenesis by diphenylmethyl selenocyanate.

Selenium, an essential micronutrient, is associated with antioxidant functions, physiological defence mechanisms against different diseases including several types of cancers. Search for new selenium compounds with more chemopreventive activities and lesser toxicities are in progress. In the present study, the antioxidative roles of a synthetic organoselenium compound, diphenylmethyl selenocyanate, were evaluated against 7,12-dimethylbenz(a)anthracene (DMBA)/croton oil-induced two-stage mouse skin carcinogenesis model. The compound was administered orally in carcinogen-induced mice in two different non-toxic doses: 2 mg/kg body weight and 3 mg/kg body weight. Significant inhibition in the incidence of papilloma formation (58-80%) as well as in the cumulative number of papilloma per papilloma-bearing mouse were observed in the treated groups as compared with the carcinogen control group. The compound was also found to significantly upregulate different phase II detoxifying enzymes in liver cytosol such as glutathione-S-transferase (P<0.01), catalase (P<0.01) and superoxide dismutase (SOD) (P<0.01) when measured after 15 days and also after 12 weeks of first DMBA treatment. Lipid peroxidation measured as the thiobarbituric acid reactive substances in liver microsomes was significantly inhibited (P<0.05) in a dose-dependent manner by diphenylmethyl selenocyanate. Thus the compound exerts its chemopreventive activity by reducing papilloma formation during chemically induced carcinogenesis, which in turn, may be through modulating the level of lipid peroxidation and phase II detoxifying enzyme system at the doses evaluated.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2004

Comparative evaluation of cancer chemopreventive efficacy of alpha-tocopherol and quercetin in a murine model.

Chemopreventive efficacy and the mode of action of alpha-tocopherol and quercetin, both known to possess anti-oxidant properties, were evaluated during carcinogenesis in uterine cervix of mice by chronic exposure to methylcholanthrene. Oral administration of alpha-tocopherol and quercetin could reduce the genotoxic effect of the carcinogen as revealed by the micronucleus frequency in vaginal epithelial cells. Both could restrict the progression of dysplastic changes in cervix uteri leading to carcinoma in-situ but the influence of the quercetin was more pronounced. A decrease in lipid peroxides following ingestion of these agents suggests that their chemopreventive action is due to their protective role on DNA damage by free radicals. Increased glutathione and glutathione-s-transferase also indicate their involvement in detoxification. While alpha-tocopherol activated the PBL response towards mitogenic stimulation, quercetin had no such effect.

Animals↗

PubMed2003

Haplotype structure of TP53 locus in Indian population and possible association with head and neck cancer.

It has been proposed that a constellation of three TP53 polymorphisms (intron 3 16 bp duplication, codon 72 BstUI, and intron 6 Nci I RFLP at nt 13494) constitute a haplotype predictive of increased cancer risk. We have estimated the allele frequency of these polymorphisms in three endogamous Indian ethnic populations from three different geographic locations (viz. Iyer from south India, Brahmin from central India and Mahishya from eastern India), as well as in head and neck squamous cell carcinoma (HNSCC) patients, and in ethnically matched normal individuals from the eastern region of India. The genotype distributions and allele frequencies of the three polymorphisms in all but one population, as well as in patients, showed a good fit to Hardy-Weinberg equilibrium. Strong linkage disequilibria were observed between all loci in every population examined, except for the 16bp-Nci I haplotype in the Mahishya population. The Mahishya population differed significantly from the other two populations with respect to differences in allele frequency and haplotype frequency. Although there were no significant differences in genotypic frequency at any of the loci between HNSCC patients and the matched control population, the minor allele frequency of codon 72 and intron 3 16 bp polymorphisms showed significant variation. Variation in overall haplotype frequency between patients and normal individuals was significant (p = 0.036) when two rare haplotypes 2-1-2 and 1-2-1 were combined. The rare haplotype 2-1-2 was found to be modestly over represented in HNSCC patients as compared to normal individuals.

DNA↗

PubMed2003

Tomato and garlic can modulate azoxymethane-induced colon carcinogenesis in rats.

Tomato (Lycopersicon esculentum) and garlic (Allium cepa) are important constituents of the human diet. Compounds like diallyl sulfides, diallyl disulfides and quercetin, which are active components of garlic, have known anti-inflammatory, antimutagenic activities. Similarly, active components in tomato, such as kaempferol and chlorogenic acid, have antimutagenic activities and lycopene is the most active oxygen quencher with potential chemopreventive activities. In view of this, an endeavour was made to evaluate the anticarcinogenic effect, if any, of tomato and garlic consumption individually and in combination on azoxymethane-induced colonic precancerous lesion, the aberrant crypt foci in animal model. Sprague-Dawley rats (4-5 weeks old) were injected with azoxymethane (15 mg/kg b.w.) and orally administered with 2% (w/v) of tomato, garlic and a combination of both. After 12 weeks of first azoxymethane injection, colons were assessed for aberrant crypt foci and compared with the carcinogen control group. Lipid peroxidation level and glutathione-S-transferase (GST) activity were assessed in liver as well as in colon. Furthermore, in situ cell proliferation and apoptosis were estimated using the Brdu incorporation method and TUNEL method respectively. It was observed that aberrant crypt foci were reduced in all treated groups (by 32.11% in garlic, by 76.14% in tomato and by 55.96% in the combination group). Among treated groups, GST activity was found to be induced in both liver and colon, whereas considerable reduction in lipid peroxidation level was observed in liver as well as in colon with respect to the carcinogen control group. Significant reduction in Brdu labelling index and increase in apoptotic index in colon was noted in the treated groups. These results suggest that tomato and garlic suspensions have a protective effect on colon carcinogenesis, which is mediated by modulation of different biological pathways during carcinogenesis.

Animals↗

PubMed2003

Allelic imbalance at chromosome 11 in head and neck squamous cell carcinoma in an Indian patient population.

BACKGROUND: Genetic instability of chromosome 11 is a frequent event in many solid tumours, including head and neck squamous cell carcinoma (HNSCC). AIMS: To perform allelic imbalance analysis of cytogenetically mapped altered regions of human chromosome 11 in patients with HNSCC from eastern India. METHODS: Genomic alterations were investigated using highly polymorphic microsatellite markers in both HNSCC and leukoplakia tissues. RESULTS: Microsatellite markers D11S1758 from 11p13-15 and D11S925 from 11q23.3-24 had the highest frequency (38% and 32%, respectively) of loss of heterozygosity among all the markers analysed. Allelic loss at the marker D11S925 was seen in both leukoplakia and in all stages of HNSCC tumour tissues suggesting that it is an early event in HNSCC tumorigenesis. Microsatellite size alteration was also found to be high (> 20%) in several markers. In leukoplakia samples microsatellite instability was seen at a higher frequency than loss of the allele, indicating such alterations might initiate the process of tumorigenesis in HNSCC. CONCLUSIONS: The high rate of chromosomal alterations at 11q21-24 in HNSCC suggests the presence of a putative tumour suppressor gene in this region.

Adult↗

PubMed2003

The emergence of the menopause in India.

A total of 130 million Indian women are expected to live beyond the menopause into old age by 2015. The menopause is emerging as an issue owing to rapid globalization, urbanization, awareness and increased longevity in urban middle-aged Indian women, who are evolving as a homogeneous group. Improved economic conditions and education may cause the attitude of rural working women to be more positive towards the menopause. However, most remain oblivious of the short- and long-term implications of the morbid conditions associated with middle and old age, simply because of lack of awareness, and the unavailability or ever-increasing cost of the medical and social support systems. Evidence-based medicine is accessible to still only a few Indian women. Most menopausal women go untreated or use unproven alternative therapies.

Estrogen Replacement Therapy↗

PubMed2003

Tea can protect against aberrant crypt foci formation during azoxymethane induced rat colon carcinogenesis.

Tea shows many health promoting activities including chemopreventive action during carcinogenesis due to the presence of antioxidative polyphenolic constituents. The present experiment evaluated the anticarcinogenic role of black tea infusion on azoxymethane induced colonic preneoplastic lesions, the aberrant crypt foci in Sprague-Dawley rats. Rats were injected with azoxymethane (15 mg/kg b.w.) and received oral administration of 1% and 2% (w/v) tea infusions from first day of carcinogen application. This treatment was continued for twelve weeks and assessed for aberrant crypt foci and compared with untreated carcinogen control group. Levels of lipid peroxidation were determined in liver as well as in colon tissue. During initiation phase of carcinogenesis, glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities were also evaluated. Significant reduction in the number of aberrant crypt foci and levels of lipid peroxidation among the tea-treated groups were observed. Induction of GST and GPx activities was noted during the initiation phase of carcinogenesis. Results of the present study indicate that the protective effect of black tea infusions may be due to an outcome of antioxidative influence of tea components on azoxymethane induced carcinogenesis.

Administration, Oral↗

PubMed2003

Sequential deletions in both arms of chromosome 9 are associated with the development of head and neck squamous cell carcinoma in Indian patients.

In the deletion mapping of chromosome (chr) 9 in head and neck lesions of the Indian patient population by microsatellite markers, we have identified four discrete areas (D1-D4) with high loss of heterozygosities (LOHs) viz. 9p24-p23 (D1), 9p22-p21 (D2), 9q11-q13 (D3) and 9q22.3 (D4) regions. The deletions in D2 and D4 regions were suggested to be essential for the development of dysplastic lesions of head and neck, whereas the deletions in D1 and D3 regions were responsible for progression of the dysplastic lesions to early invasive head and neck squamous cell carcinoma (HNSCC). The microsatellite size alterations (MAs) were observed in the chromosomal 9pter-p23, 9p22-p21(D2), 9q13 and 9q21.1-q21.2 regions with gradual increase during progression of the tumor. Additional chromosomal alterations like loss of normal copy of chr.9 and biallelic alterations were also seen in our samples. There is a correlation between HPV infection with TNM stages, histopathological grades and LOHs at D1 and D4 regions. Whereas tobacco habit is associated with the occurrence of LOHs at D1 and LOHs / MAs at D2 region.

Adolescent↗

PubMed2003

Association of deletion in the chromosomal 8p21.3-23 region with the development of invasive head & neck squamous cell carcinoma in Indian patients.

BACKGROUND & OBJECTIVES: Deletions in chromosome 8 (chr.8) have been shown to be necessary for the development of head and neck squamous cell carcinoma (HNSCC). Attempts have been made in this study to detect the minimal deleted region in chr.8 associated with the development of HNSCC in Indian patients and to study the association of clinicopathological features with the progression of the disease. METHODS: The deletion mapping of chr.8 was done in samples from 10 primary dysplastic lesions and 43 invasive squamous cell carcinomas from the head and neck region of Indian patients to detect allelic alterations (deletion or size alteration) using 12 highly polymorphic microsatellite markers. The association of the highly deleted region was correlated with the tumour node metastasis (TNM) stages, nodal involvement, tobacco habit and human papilloma virus (HPV) infection of the samples. RESULTS: High frequency (49%) of loss of heterozygosity (LOH) was seen within 13.12 megabase (Mb) region of chromosomal 8p21.3-23 region in the HNSCC samples, whereas the dysplastic samples did not show any allelic alterations in this region. The highest frequency (17%) of microsatellite size alterations (MA) was observed in the chr.8p22 region. The loss of short arm or normal copy of chr.8 and rare bi-allelic alterations were seen in the stage II-IV tumours (939, 5184, 2772, 1319 and 598) irrespective of their primary sites. The highly deleted region did not show any significant association with any of the clinical parameters. However, HPV infection was significantly associated (P < 0.05) with the differentiation grades and overall allelic alterations (LOH/MA) of the samples. INTERPRETATION & CONCLUSION: Our data indicate that the 13.12 Mb deleted region in the chromosomal 8p21.3-23 region could harbour candidate tumour suppressor gene(s) (TSGs) associated with the progression anti invasion of HNSCC tumours in Indian patients.

Alleles↗

PubMed2002

Mapping of the candidate tumor suppressor genes' loci on human chromosome 3 in head and neck squamous cell carcinoma of an Indian patient population.

The candidate tumor suppressor genes' (TSG) loci on human chromosome 3 (chr.3) were mapped in six dysplastic lesions and 51 primary squamous cell carcinoma from head and neck region of an Indian patient population by using 20 highly polymorphic microsatellite markers. The two chromosomal regions 3p12-13 and 3p21.2-22 have shown the highest losses of heterozygosity (LOHs) of 34.6-38% and 37-46%, respectively with statistically significant clinical correlation's with tobacco habit, positive lymph node and tumor stages. In addition, high frequencies of microsatellite size alterations (MAs) of 16.2-28.5% and 23.8-28.2% were observed in the chromosomal 3p11-13 and 3p21.2-22 regions, respectively, with significant above-mentioned clinical correlation only in the 3p11-13 region. In the dysplastic lesions, the prevalence of LOHs compared to the MAs had indicated that LOHs might be the early events. Five tumors at stage-III/IV seemed to have lost an entire normal copy of chr.3. It was of particular note that 17% (10/57) of the samples showed rare bi-allelic alterations mainly in and around the high LOHs regions. Thus, (1) the gradual increase of LOHs/MAs during progression of the tumor, (2) high frequencies of MAs, (3) rare bi-allelic alterations in and around high LOHs regions and (4) loss of wild type chr.3 in the later stages of tumor development have suggested that such alterations might provide selective growth advantage to the tumors. Also, we propose from our data that the high LOHs regions (3p12-13 and 3p21.2-22) could harbour putative TSG(s), responsible for the development of head and neck squamous cell carcinoma.

Adult↗

PubMed2001

Microsatellite instability in squamous cell carcinoma of head and neck from the Indian patient population.

Genomic instability in simple repeated sequences has been observed in several human cancers. We have analyzed 50 squamous cell carcinomas of the head and neck (SCCHN) and 5 pre-malignant severe dysplastic tissues from Indian patient populations for microsatellite instability in 18 different loci spread over eight different chromosomes. Among the tumors analyzed, 45% exhibited instability at two or more loci, and 15% exhibited instability at 40% of the markers tested. Similar analysis of SCCHN tumors from other populations (British, American and French) showed much less frequency of instability. SCCHN tumors in the present study did not show any instability in the mononucleotide repeat sequences. There is also a clear distinction in the nature of the instability in these tumors in comparison with colorectal tumors. These results suggest that the underlying mechanism generating this type of instability is different from those reported for colorectal tumors.

Adult↗

PubMed2001

Cloning and tissue-specific gene expression studies with Dlxin-1, a newly identified transcriptional activator.

Dlxin-1, a unique member of the necdin/melanoma associated antigen gene (MAGE) family, is a novel protein that binds Dlxin-5 and regulates its transcriptional function. We have cloned the homology region between Dlxin-1 and necdin from mouse melanoma cells. Here we report the expression cloning, characterization, and detailed tissue-specific expression studies of Dlxin-1. A unique expression pattern of Dlxin-1 emerged from the work wherein strong expression of a 3.2-Kb transcript was observed in mouse brain and embryos. Amongst the representative established cell lines of different tumor categories studied the presence of transcript was detected only in sarcomas and neuroectodermal tumors. Characteristically, lymphomas, leukaemias, adenocarcinomas, and carcinomas did not express Dlxin-1. Also, we observed a growth suppression on ectopic expression of this cDNA possibly due to the close homology shared with necdin, a neuron-specific growth suppressor. The extensive homology of our Dlxin-1 clone to necdin makes it an attractive system to understand the importance of the necdin/MAGE family of molecules in cell cycle regulation.

3T3 Cells↗

PubMed2001

Distribution of MUC1 in the normal human oral cavity is localized to the ducts of minor salivary glands.

The change in expression of MUC1 from health to disease forms the basis of its use as a potential disease marker. Previous attempts at isolating MUC1 from normal, healthy human oral mucosa have, however, drawn conflicting conclusions as to its presence. Furthermore, when MUC1 was detected in the oral glycocalyx, it was not clear which cells were synthesising it. We examined human oral glycocalyx using pooled buccal smears from 50 normal individuals. Following isopycnic density centrifugation and membrane extraction with octyl glucoside and saponin, MUC1 was detected with the polyclonal antibody CT1. Immunohistochemistry using antibodies CT1 and BC2 was performed on sections from eight labial, seven palatal, four buccal, three retromolar pad, three dorsum of tongue and two ventral surface of tongue biopsies. In-situ hybridisation using MUC1 and cytoplasmic tail oligoprobes on sections from four palatal, seven labial and two retromolar pad biopsies was also carried out. MUC1 mRNA could only be detected in the minor salivary mucous glands. MUC1 has already been identified in the ducts of normal parotid and submandibular gland, and our findings demonstrate a similar distribution in minor salivary glands. We conclude that when present in the normal oral glycocalyx, the only oral source of MUC1 is from cell membranes of the minor salivary glands.

Antibodies↗

PubMed2001

An application of the thresholds of change model to the analysis of mental health data.

The threshold of change model (TCM) is a statistical technique for analyzing ordered stages of change variables. TCM focuses on the thresholds that separate the ordered stages, and the effects of explanatory variables are evaluated in terms of raising or lowering the thresholds. TCM also allows the explanatory variables to exert differential influence on each threshold. In this paper, we use TCM to analyze the data from a clinical trial that compared assertive community treatment (ACT) with standard case management (SCM) for patients with co-occurring severe mental illness and substance use disorder. Endpoint data (36-month follow up) were used for this analysis. The response variable is the recoded Substance Abuse Treatment Scale with three ordered levels (engagement/persuasion, active treatment, and recovery/relapse prevention), and hence two thresholds. The explanatory variables are gender and group (ACT vs. SCM). The results indicate that gender exerts constant and significant effects on both thresholds. The group effect is somewhat mixed: ACT lowers the first threshold (active treatment), but raises the second threshold (recovery/relapse prevention).

Adolescent↗