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We studied the response to UV irradiation in cells from four patients, from three apparently unrelated families, affected by trichothiodystrophy (TTD). They showed all the symptoms of this rare autosomal recessive disorder (brittle hair with reduced sulfur content, mental and physical retardation, ichthyosis, peculiar face) together with photosensitivity. We found a decreased rate of duplicative DNA synthesis in stimulated lymphocytes, reduced survival in fibroblasts, and very low levels of unscheduled DNA synthesis (UDS) in Go lymphocytes and fibroblasts after UV irradiation. Complementation studies showed that normal values of UDS are restored in heterokaryons obtained by fusion of TTD cells with normal and xeroderma pigmentosum (XP)-complementation group A-cells. In contrast the defect is not complemented by fusion with XP-complementation group D-fibroblasts.

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Available results highlight the lack of good level of evidence studies on the pure prognostic value of histological grade. In the present study, the prognostic relevance of histological grade and of its three components, tubule formation, nuclear pleomorphism and mitotic count, was analyzed in a series of 372 patients with node-negative breast cancer treated with locoregional therapy alone until early relapse. Histological grade was determined blindly by two observers and discordance between evaluations was resolved after joint review using a multihead microscope. No relation was observed between histological grade and any of its three components and disease-free survival. Conversely, a significant relation was observed between histological grade and distant metastasis-free survival (at 6 years, 94, 86 and 76% for grades 1, 2 and 3, respectively, P ¼ 0.013) as well as overall survival (98, 90 and 86%, P ¼ 0.001). A breakdown analysis as a function of the three components showed that neither tubule formation nor nuclear pleomorphism was associated with prognosis, and only mitotic count strongly influenced both distant metastasis-free survival (91, 82 and 74%, P ¼ 0.014) and overall survival (97, 87 and 85%, P ¼ 0.011). Histological grade suffers from a much higher subjectivity than any other microscopic evaluation of biomarkers as it is the sum of three different morphological features. Within the Italian Network for Quality Assessment of Tumor Biomarkers program we observed that histological grade is an independent prognostic variable, but also that this role is ascribable only to the number of mitotic figures. In conclusion, due to the ever smaller size of diagnosed breast cancers, resulting in less cancer tissue for biofunctional and molecular analysis, mitotic count evaluated under strict quality control conditions seems to be an accurate and feasible prognostic variable.

Stimulation of human lymphocytes with phytohemagglutinin is known to induce an increase in overall DNA polymerase activity (DNA nucleotidyltransferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7). Previous work [Pedrali Noy, G., Dalpra, L., Pedrini, A. M., Ciarrocchi, G., Giulotto, E., Nuzzo, F. & Falaschi, A. (1974) Nucleic Acids Res. 1, 1183] has shown that two subsequent waves of induction of DNA polymerase can be observed in this system; a first wave occurs in parallel with the increase in DNA replication rate; a second one occurs when the DNA synthesis rate is returned to minimal levels; the second peak is parallel to a maximum in DNA ligase and DNase levels.In the present work we have measured the levels of the DNA polymerases-a and -, in phytohemagglutinin-stimulated lymphocytes during a 12-day period; both enzymes are present at detectable levels at time zero; in correspondence to the peak of DNA synthesis rate (between the fourth and fifth day) a peak of DNA polymerase-a is observed, increasing by a factor of approximately 20-fold over the zero time value; subsequently, the level of DNA polymerase-a decreases in parallel with DNA synthesis rate. The DNA polymerase-ft is also increased in correspondence to the peak in DNA synthesis rate, but reaches its maximum at later times, between the eighth and tenth day of incubation.The capacity of stimulated lymphocytes to perform repair synthesis following UV damage was measured in the same cells used for the enzyme activity determinations; this capacity also shows two maxima: a first one correlated with the peak in DNA replication rate, and a second one correlated with the peak of DNA polymerase-fl.These data suggest a certain tendency to the specialization of functions in human cell DNA polymerases; the a-enzyme seems mainly correlated with DNA replication, whereas the a-enzyme seems more correlated with the ability of the cell to perform repair type synthesis.Human lymphocytes stimulated with phytohemagglutinin (PHA) represent a useful model system to obtain information on the role of the enzymes of DNA metabolism; the stimulated cells undergo dramatic variations in DNA replication rate (1), and any positively correlated variation of the level of a certain enzyme gives a strong inference for a function of that enzyme in DNA replication.Several authors have shown that overall DNA polymerase (DNA nucleotidyltransferase; deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7) levels increase markedly in parallel to DNA synthesis rate, and both parameters reach their maximum at the same time, between the second and fifth day of culture (2-6), in correspondence to the peak of mitoses. In human cells two main molecular species of DNA polymerase are known, defined as -a and -,3 (7-10); the a-enzyme is the most abundant one, has an s°20,w of 6.5 S and is inhibited by N-ethylmaleimide; the ,B-enzyme has an S020W of 3.4 S and is insensitive to N-ethylmaleimide. The molecular species of DNA polymerase which is mainl...