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.

Isolation and characterization of nonhistone proteins associated with DNase-II hypersensitive sites of Sarcoma-180 chromatin.

Limited digestion (2 min) of Sarcoma-180 nuclei by DNase-II released two nonhistone proteins from the hypersensitive sites of chromatin. The apparent molecular weights of these two proteins were 34 and 21 kDa. These proteins showed a moderate but specific inhibition in in vitro cell free transcription assay with native chromatin as template as opposed to no effect on native DNA transcription.

Effect of anthracycline antibiotics on in vitro transcription of chromatin in a Sarcoma-180 whole cell extract.

A soluble extract capable of transcribing Sarcoma-180 chromatin and DNA in a cell-free transcription system was prepared from Sarcoma-180 mouse ascites tumour cells. Incorporation of [3H]UTP into trichloroacetic acid-precipitable fraction is (i) reduced by 50% on removing DNase I hypersensitive sites of chromatin and (ii) inhibited by DNA binding antitumour anthracyclines, suggesting that this cell-free assay represents true transcription of active genes of Sarcoma-180 chromatin. Preparation of this soluble extract from mouse ascites tumour cells thus presents a very convenient way of studying cell-free transcription of active genes of chromatin and effect of antitumour agents on chromatin transcription.