Impaired nucleotide excision repair pathway as a possible factor in pathogenesis of head and neck cancer.

Tobacco smoking is one of the major risk factors in pathogenesis of head and neck squamous cell carcinomas (HNSCC). Many of the chemical compounds present in tobacco are well-known carcinogens which form adducts with DNA. Cells remove these adducts mainly by the nucleotide excision repair pathway (NER). NER also eliminates a broad spectrum of pyrimidine dimers (CPD) and photo-products (6-4PP) induced by UV-radiation or DNA cross-links after cisplatin anti-cancer treatment. In this study DNA damage and repair was examined in peripheral blood lymphocytes obtained from 20 HNSCC patients and 20 healthy controls as well as HTB-43 larynx and SSC-25 tongue cancer cell lines. DNA repair kinetics in the examined cells after cisplatin or UV-radiation treatment were investigated using alkaline comet assay during 240min of post-treatment incubation. MTT assay was used to analyse cell viability and the Annexin V-FITC kit specific for kinase-3 was employed to determine apoptosis after treating the cells with UV-radiation at dose range from 0.5 to 60J/m(2). NER capability was assessed in vitro with cell extracts by the use of a bacterial plasmid irradiated with UV-light as a substrate for the repair. The results show that lymphocytes from HNSCC patients and HTB-43 or SSC-25 cancer cells were more sensitive to genotoxic treatment with UV-radiation and displayed impaired DNA repair. Also evidenced was a higher rate of apoptosis induction after UV-radiation treatment of lymphocytes from the HNSCC patients and the HTB-43 cancer cells than after treatment of those from healthy donors. Finally, our results showed that there was a significant decrease in NER capacity in HTB-43 or SSC-25 cancer cells as well as in peripheral blood lymphocytes of HNSCC patients compared to controls. In conclusion, we suggest that the impaired NER pathway might be a critical factor in pathogenesis of head and neck cancer.

Qualitative and quantitative studies in electron microscopy on influence of experimental ischemia of the vertebral arteries on the outer hair cells function in guinea pigs.

Histological studies were performed in 20 guinea pigs, both sexes, weighing 250-300 g and divided into two groups: I--control (anaesthetized animals without surgery), II--examined (in anaesthetized animals through an incision of the skin and muscles of the neck), the left or right vertebral artery was exposed and a vascular clip was inserted into the foramen of the transverse process of the 2-nd cervical vertebra. 50 days after this procedure, the guinea pigs were again anaesthetized by intraperitoneal injection of 35% solution of chloral hydrate, then vascular and cochlear perfusion with 3.6% solution of glutaraldehyde was performed. Simultaneously, by means of micropreparation, samples of cochlea were made for electron studies by means of electron microscope (Philips EM 300). In qualitative histopathologic examinations in guinea pigs of II group, the ischemia changes of the outer hair cells were greater in the side of irritation of the vertebral artery than at the opposite side. At the receptor side of these cells, under the membrane, there are multilamellar outgrowths in the shape of cisterns, partly expanded. The relative volume of external compartment of mitochondria in control group is as follows respectively: 0.15 +/- 0.0% at the right side and 0.15 +/- 0.08% at the left side, and in II group, respectively: 0.22 +/- 0.06% at the side of irritation and 0.19 +/- 0.07% at the opposite side. The obtained data in electron microscopy, both qualitative and quantitative pointed at ischemia changes of outer hair cells in guinea pigs after prolonged irritation of periarterial plexus of vertebral artery.