miR-125b promotes cell death by targeting spindle assembly checkpoint gene MAD1 and modulating mitotic progression.

The spindle assembly checkpoint (SAC) is a 'wait-anaphase' mechanism that has evolved in eukaryotic cells in response to the stochastic nature of chromosome-spindle attachments. In the recent past, different aspects of the SAC regulation have been described. However, the role of microRNAs in the SAC is vaguely understood. We report here that Mad1, a core SAC protein, is repressed by human miR-125b. Mad1 serves as an adaptor protein for Mad2 - which functions to inhibit anaphase entry till the chromosomal defects in metaphase are corrected. We show that exogenous expression of miR-125b, through downregulation of Mad1, delays cells at metaphase. As a result of this delay, cells proceed towards apoptotic death, which follows from elevated chromosomal abnormalities upon ectopic expression of miR-125b. Moreover, expressions of Mad1 and miR-125b are inversely correlated in a variety of cancer cell lines, as well as in primary head and neck tumour tissues. We conclude that increased expression of miR-125b inhibits cell proliferation by suppressing Mad1 and activating the SAC transiently. We hypothesize an optimum Mad1 level and thus, a properly scheduled SAC is maintained partly by miR-125b.

Association of FANCC and PTCH1 with the development of early dysplastic lesions of the head and neck.

BACKGROUND: Alteration of chromosome 9q22.3 region is an early and frequent event in head and neck squamous cell carcinoma (HNSCC). The aim of this study was to understand the association of candidate tumor suppressor genes PHF2, FANCC, PTCH1, and XPA located in this region in the development of HNSCC. METHODS: The alterations (deletion, promoter methylation, mutation, expression) of these genes were analyzed in 65 dysplastic head and neck lesions and 84 primary HNSCC samples. Clinicopathologic correlations were made with alterations of the genes. RESULTS: Overall alterations (deletion, promoter methylation) of FANCC and PTCH1 were high in mild dysplasia and comparable in subsequent stages of tumor progression. However, PHF2 alteration was low in mild dysplasia, but increased in moderate and severe dysplasias. Alterations (deletion, promoter methylation) of FANCC and PTCH1 showed association with each other. Two novel mutations in GLI binding sites of PTCH1 promoter and a novel microsatellite marker hmPTCH1 with four alleles at immediate upstream of the gene were identified. In a case-control study, the (CGG)7 allele of hmPTCH1 was found to be susceptible for HNSCC development. Concordance was seen in the expression (RNA, protein) of these genes with their molecular alterations. CONCLUSIONS: Alterations of FANCC and PTCH1 could be used as molecular marker for early diagnosis and prognosis of HNSCC.

BRCA1 protein expression and its correlation with ER/PR status in sporadic and familial breast cancer in Eastern Indian patients--a hospital based study.

BRCA1 gene expression in familial breast cancer is mainly focused on mutational analysis. However in sporadic cancers BRCA1 protein expression is the main area of interest because somatic inactivation of one allele of the gene is likely to occur during the oestrogen mediated proliferation at puberty and subsequent tumourigenic events take place in the same cell. Standard immunohistochemical analysis was used to assess BRCA1 and oestrogen/progesterone receptor (ER/PR) status in familial and sporadic breast cancer patients and correlation of BRCA1 protein expression with histopathological features ER/PR status was studied in these tumours. One hundred and seventy-seven sporadic tumours (group A) and 28 familial tumours (patients with history of breast cancer in first or second degree relative ie, group B) were studied. In group A, 61 tumours had absent/reduced BRCA 1 protein expression; 30 (49%) out of these were negative for ER/PR receptors. In group B, 18 patients had absent/reduced BRCA1 protein expression, and 10 (55.6%) out of these, were ER/PR negative. Overall in 2 groups, 82 tumours were of grade 1, 61 tumours of grade 2 and 62 tumours were of grade 3 differentiation. Test of proportion showed that percentage of ER/PR negativity is significantly higher than ER/PR positivity in sporadic as well as in familial tumours with absent/ reduced BRCA 1 protein expression (p < 0.05). Sporadic tumours with deranged BRCA1 protein expression like familial tumours have more unfavourable histopathological characteristics and are likely to be of higher grade and oestrogen receptor negative

Development and Validation of a Stability-indicating UV Spectroscopic Method for Candesartan in Bulk and Formulations.

A simple, specific, accurate and stability-indicating UV- Spectrophotometric method was developed for the estimation of candesartan cilexitil, using a Shimadzu, model 1700 spectrophotometer and a mobile phase composed of methanol: water in the ratio of 9:1 at wave length (λ(max)) 254 nm. Linearity was established for candesartan in the range of 10-90 µg/ml. The percentage recovery of was found to be in the range of 99.76-100.79%. The drug was subjected to acid, alkali and neutral hydrolysis, oxidation, dry heat, UV light and photolytic degradation. Validation experiments performed to demonstrate system suitability, specificity, precision, linearity, accuracy, interday assay, intraday assay, robustness, ruggedness, LOD, and LOQ. While estimating the commercial formulation there was no interference of excipients and other additives. Hence this method can be used for routine determination of candesartan cilexetil in bulk and their pharmaceutical dosage forms. The proposed method for stability study shows that there was appreciable degradation found in stress condition of candesartan.

MYC gene amplification reveals clinical association with head and neck squamous cell carcinoma in Indian patients.

BACKGROUND: Amplification of the MYC gene is reported to be associated with the development of head and neck squamous cell carcinoma (HNSCC). This study is focused to analyze the correlation between MYC gene amplification and various clinicopathological features and outcome in a cohort of 49 dysplastic and 187 primary head and neck lesions. METHODS: MYC gene amplification was assessed by differential polymerase chain reaction using primer sets from the MYC gene as target locus and DRD2 gene as the control locus. RESULT: The MYC gene amplification was detected in a total of 23.7% (56/236) head and neck lesions comprising 14.2% (7/49) dysplastic lesions and 26% (49/187) HNSCC samples. The clinicopathological association study between MYC gene amplification with the different clinical parameters like sex, tumor stage, tumor differentiation, lymph node status, tobacco habit and HPV 16/18 status determined significant association of MYC amplification with tumor progression (P = 0.009). Kaplan Meier analysis revealed MYC gene has no prognostic significance on survival in HNSCC. CONCLUSION: In conclusion, our results suggest that MYC gene amplification is associated with tumor progression in HNSCC.

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.

Human papillomavirus prevalence in postradiotherapy uterine cervical carcinoma patients: correlation with recurrence of the disease.

To understand the role of human papillomavirus (HPV) in recurrence of uterine cervical cancer (CA-CX) after radiotherapy, we have analyzed the HPV prevalence in the exfoliated cells of 56 patients and their corresponding plasma. HPV DNA was detected in exfoliated cells of 78% (44/56) patients (HPV-16, 68%; HPV-18, 14%; HPV-X [other than 16, 18], 11%; and mixed infection of HPV-16 and HPV-18 in three cases). HPV DNA in plasma was present in only 25% (11/44) of the HPV-positive exfoliated cells (positive predictive value, 100%; negative predictive value, 27%) with concordance in HPV types. The recurrence of the disease was significantly associated with the presence of HPV in the exfoliated cell (P= 0.01) and plasma (P= 0.007) as well as high viral load in the exfoliated cell (P= 0.0002). Kaplan-Meier disease-free estimates have also shown the significant association between HPV prevalence in plasma and recurrence of the disease (P= 0.045). Thus, it indicates that in postradiotherapy CA-CX patients, the high viral load in the exfoliated cell as well as HPV presence in the plasma samples could be used in early detection of the patients at increased risk for disease recurrence and progression.

Hepatitis B infection in Eastern Indian families: need for screening of adult siblings and mothers of adult index cases.

OBJECTIVES: India, with its 43 million hepatitis B virus (HBV) carriers and absence of any national immunization programme, adds a substantial number of HBV infections to the HBV carrier pool yearly. The aim of this study was to assess the spread of HBV infection in families with an infected member and to identify the family members with the highest risk of infection in our community. METHODS: A total of 937 serum samples from 215 HBV-infected cases and 722 members of their households were screened prospectively for markers of HBV by commercial enzyme-linked immunosorbent assay. RESULTS: Among family members, 140 (19.4%) were HBsAg positive and 272 (37.6%) were negative for HBsAg but positive for either anti HBc or anti HBs. There were 145 HBsAg-positive adults among the index cases whose 133 adult siblings, 59 spouses and 59 mothers participated in the study. Interestingly, 28.81% mothers and 28.57% adult siblings of these adult index cases were positive for HBsAg compared with only 8.75% of their spouses (P < 0.001). Only 15.2% of the HBsAg-positive women in the childbearing age group were found to be HBeAg positive. CONCLUSIONS: Our results suggest that intrafamilial childhood horizontal transmission is important for HBV transmission in our community, and highlight the need for screening of adult siblings and mothers of adult HBsAg carriers in addition to their spouses and children.

Association of specific genotype and haplotype of p53 gene with cervical cancer in India.

BACKGROUND: The predictive value of codon 72 arginine homozygosity at the p53 gene for human papilloma virus associated cervical cancer risk remains inconclusive. It has also been proposed that the inheritance of specific germline haplotypes based on three biallelic polymorphisms of p53 (intron 3 16 bp duplication, codon 72 Bst UI (Arg/Pro), and intron 6 Nci I restriction fragment length polymorphism at nucleotide 13494) is a better predictor of various cancer risks. AIMS: To determine the genotype and haplotype frequency of these three p53 polymorphisms in 61 patients with cervical squamous cell carcinoma and 94 ethnically matched controls from the eastern region of India and estimate the risk, if any, of specific genotypes and haplotypes. METHODS: Samples were genotyped by polymerase chain reaction followed by variant specific restriction enzyme digestion. Haplotypes were estimated by the maximum likelihood method using the expectation maximisation algorithm. RESULTS: Genotype distributions of the three polymorphisms in patients and controls showed a good fit to the Hardy-Weinberg equilibrium. The p53 codon 72 arginine homozygous genotype was significantly over represented in patients compared with controls. Those with the homozygous arginine genotype exhibited a 2.59 fold higher risk of developing squamous cell carcinoma of the uterine cervix. A significant risk was also seen with a combination of two haplotypes, 1-2-1 and 1-2-2. CONCLUSION: p53 codon 72 arginine homozygotes appear to be at greater risk of developing squamous cell carcinoma of the uterine cervix. The high risk haplotypes 1-2-1 and 1-2-2 also contain the arginine allele, further strengthening this conclusion.

Analysis of molecular alterations in chromosome 8 associated with the development of uterine cervical carcinoma of Indian patients.

OBJECTIVES: We have been done the detailed deletion mapping of chromosome (chr.) 8p21.3-23 to localize the candidate tumor suppressor gene(s) (TSGs) loci as well as studied the mechanism of activation of c-myc gene, located at chr.8q24.1, by analyzing the amplification/rearrangement/HPV integration within approximately 580 kb of c-myc locus in uterine cervical carcinoma (CaCx) of Indian patients. The association between the deletions in chr.8p21.3-23 and alterations in the c-myc locus has also been analyzed. METHODS: The deletion mapping of chr.8p21.3-23 was done by 15 microsatellite markers and the alterations in the c-myc locus were analyzed by Southern hybridization using the pal-1/c-myc/mlvi-4/HPV 16/18 probes in seven cervical intraepithelial neoplasia (CIN) and 55 primary uterine cervical carcinoma. The alterations in chr.8p/q have been correlated with the different clinicopathological parameters. RESULTS: Three discrete minimal deleted regions with high frequencies of loss of heterozygosity (LOH) (37-43%) were identified in the chr.8p23.1-23.2 (D1), 8p23.1 (D2), and 8p 21.3-22 (D3) regions within 0.41-4.62 Mb. The deletion in the D1 region was significantly associated with the deletion in the D2 region (P = 0.03), whereas the deletion in D2 was marginally associated with the deletion in the D3 region (P = 0.07). The alterations in the c-myc locus were seen in 43% of the samples. About 35% of the samples showed coalterations in both arms of chr.8. No significant association was observed with the alterations in chr.8p/q as well as with the different clinicopathological parameters. CONCLUSIONS: The deletions in chr.8p21.3-23 and the alterations in the c-myc locus are independently associated with the development of CaCx. The D1-D3 regions in chr.8p21.3-23 could harbor candidate TSGs associated with the development of this tumor. The c-myc gene was activated by amplification/rearrangement at the pal-1/c-myc/mlvi-4 loci as well as HPV integration in the pal-1 locus in this tumor.

Three discrete areas within the chromosomal 8p21.3-23 region are associated with the development of breast carcinoma of Indian patients.

Deletion in the 22.9 -Mb chromosomal (chr.) 8p21.3-23 region has been shown to be necessary for the development of breast carcinoma (CaBr). In this study, we have attempted to detect the minimal deleted region(s) in the chr.8p21.3-23 region in 62 primary breast lesions having 56 CaBr tumors and six other breast lesions of Indian patients using 15 microsatellite markers. The loss of heterozygosity (LOH) was observed for at least one marker in 96.4% (54/56) of the CaBr samples. Three discrete minimal deleted regions with high frequencies of LOH (39-65%) were identified in the chromosomal 8p23.1-23.2 (D1), 8p23.1 (D2) and 8p 21.3-22 (D3) regions within 2.03, 0.41, 2.47 Mb, respectively. No significant correlation was observed with the high deleted regions and the different clinicopathological parameters. Interestingly, 51.8% (29/56) CaBr samples showed either loss of chr.8p or interstitial deletions in this arm, indicating the importance of chr.8p in the development of CaBr. The pattern of allelic loss in the bilateral lesions had indicated that the lesions were clonal in origin and probably the deletion in the D3 region was the early event among the D1-D3 regions. Thus, our data have indicated that the D1-D3 regions could harbor candidate tumor suppressor gene(s) (TSGs) associated with the development of CaBr.

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.

Differential deletions of chromosome 3p are associated with the development of uterine cervical carcinoma in Indian patients.

BACKGROUND: Deletions in chromosome 3 occur frequently in uterine cervical carcinoma (CA-CX). The common consensus regions deleted during CA-CX development are not well defined, and have not been correlated with tumour progression. AIMS: To define specific regions of chromosome 3 deleted during development of CA-CX and to correlate these with clinicopathological data. METHODS: Deletion mapping of chromosome 3 was done in seven cervical intraepithelial neoplasia (CIN) and 43 primary CA-CX samples using 20 highly polymorphic microsatellite markers. RESULTS: Deletions of chromosome 3 were significantly associated with tumour progression. High frequencies (33-53%) of loss of heterozygosity (LOH) were found in 3p26.1, 3p22.3, 3p21.2, and 3p13, suggesting the location of putative tumour suppressor genes (TSGs) in these regions. Among these four regions, deletions in 3p21.2 were suggested to occur early during CA-CX development. A significant correlation was found between LOH at 3p26.1 and 3p22.3 with tumour progression from stage I/IIB to stage III/IV. No association was found with the highly deleted regions and human papillomavirus positivity, parity, or menopausal status. Microsatellite size alteration was seen in only seven of the samples. However, rare biallelic alterations were seen in and around the highly deleted regions. Loss of normal copy of chromosome 3 and interstitial alterations in chromosome 3p were seen in some samples. CONCLUSION: These four regions on chromosome 3p may be differentially deleted during specific stages of CA-CX development. The putative TSGs located in these regions may have a cumulative effect on tumour progression.

Alterations of the P16 gene in uterine cervical carcinoma from Indian patients.

In our analysis, alterations in the P16 tumor suppressor gene were seen in 33% (15/46) of sampled uterine cervical lesions. Among the alterations, mutations in P16 were detected in 15% (7/46) of the samples. One mutation occurred at intron 1/exon 2 splice junction. All the other mutations were in exon 2 with three of them as silent mutations. The promoter hypermethylation and homozygous deletion of P16 gene were detected in 6.5% (3/46) and 8.7% (4/46) of the samples respectively. Loss of heterozygosity and microsatellite size alterations at the P16 locus were seen in 17% (8/46) of the samples. HPV16/18 infection was detected in 76% (35/46) of the samples. But no association was found between P16 alterations and HPV infection. Thus, it seems that P16 inactivation may be associated with the development of some uterine cervical carcinoma.

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.

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.

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.

Prediction of retinoblastoma and osteosarcoma: linkage analysis of families by using polymorphic markers around RB1 locus.

PURPOSE: Linkage analysis at the retinoblastoma gene (RB1) locus is required for identification of individuals at risk of developing retinoblastoma and osteosarcoma. Identification of disease causing mutations is necessary for accurate risk prediction. However, the usefulness of direct mutation analysis is impeded by the size and complexity of the RB1 gene. The authors report an alternative polymerase chain reaction (PCR)-based method for genotyping the RB1 locus using polymorphic microsatellite markers for the prediction of risk of developing the disease. MATERIALS AND METHODS: For this purpose, we have used 2 intragenic microsatellite markers of the RB1 gene, D13S153 and RB1.20 VNTR, and 2 flanking markers D13S218 and D13S176. The segregations of the 4 polymorphic markers within and flanking the RB1 gene were analyzed in 3 families with osteosarcoma and 2 families with retinoblastoma. RESULTS AND CONCLUSION: Our results showed that linkage analysis of families by using the intragenic and flanking markers could be applied to detect carriers and for prenatal diagnosis in families with retinoblastoma and osteosarcoma. Moreover, this PCR-based genotyping is simpler and faster than other conventional methodologies.

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.

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.