[Quantitative methylation-specific PCR for the diagnosis of lung cancer]. / Quantitative methylierungsspezifische PCR zur Lungenkarzinomdiagnostik.

Efficient, preferably early diagnosis of lung cancer represents a major challenge. Under this aspect the sensitivity of conventional histomorphology and cytomorphology procedures is unsatisfactory. This review highlights technical aspects, possibilities and drawbacks of the application of aberrant promoter methylation as a biomarker for lung cancer diagnostics using specimens of pulmonary exfoliative cytology.

[Molecular cytopathology of lung cancer--prevalence of genetic alterations and their role in the development of molecular biomarkers]. / Molekulare Zytopathologie bösartiger Lungentumoren--Prävalenz der genetischen Alterationen und ihre Bedeutung für die Entwicklung molekularer Biomarker.

Carcinogenesis of lung cancer proceeds via a complex process that involves multiple genetic abnormalities, which do not necessarily have a linear progression. Genetic alterations include aneuploidy, deletions and amplifications of chromosomal regions, loss of heterozygosity (LOH), microsatellite alterations, point mutations and aberrant promoter methylation. There is considerable effort to use these genetic alterations as molecular biomarkers for early cancer diagnosis applying different approaches. An ideal tumor marker should be highly sensitive, tumor specific, easily to handle and non-cost intensive. While previous studies used screening for mutations, LOH and microsatellite alterations, more recent strategies concentrate on multicolor fluorescence in situ hybridization (FISH) and aberrant promoter methylation. Since in general the genetic alterations are prone to be more extensive in tumor cells as compared to non-tumor cells, methods that provide quantitative data (e.g., methylation specific real-time PCR) are likely to improve specificity. Consequently, molecular biomarkers could constribute to a more accurate risk assessment in carcinogen exposed individuals and early molecular cytologic diagnosis of precancerous lesions and cancers of the lung.

DNA double-strand break repair in cell-free extracts from Ku80-deficient cells: implications for Ku serving as an alignment factor in non-homologous DNA end joining.

Non-homologous DNA end joining (NHEJ) is considered the major pathway of double-strand break (DSB) repair in mammalian cells and depends, among other things, on the DNA end-binding Ku70/80 hetero-dimer. To investigate the function of Ku in NHEJ we have compared the ability of cell-free extracts from wild-type CHO-K1 cells, Ku80-deficient xrs6 cells and Ku80-cDNA-complemented xrs6 cells (xrs6-Ku80) to rejoin different types of DSB in vitro. While the two Ku80-proficient extracts were highly efficient and accurate in rejoining all types of DNA ends, the xrs6 extract displayed strongly decreased NHEJ efficiency and accuracy. The lack of accuracy is most evident in non-homologous terminus configurations containing 3'-overhangs that abut a 5'-overhang or blunt end. While the sequences of the 3'-overhangs are mostly preserved by fill-in DNA synthesis in the Ku80-proficient extracts, they are always completely lost in the xrs6 extract so that, instead, small deletions displaying microhomology patches at their breakpoints arise. In summary, our results are consistent with previous results from Ku-deficient yeast strains and indicate that Ku may serve as an alignment factor that not only increases NHEJ efficiency but also accuracy. Furthermore, a secondary NHEJ activity is present in the absence of Ku which is error-prone and possibly assisted by base pairing interactions.