The xeroderma pigmentosum group D (XPD) helicase subunit of TFIIH functions in DNA repair and transcription initiation. Different mutations in XPD give rise to three ultraviolet-sensitive syndromes: the skin cancer-prone disorder xeroderma pigmentosum (XP), in which repair of ultraviolet damage is affected; and the severe neurodevelopmental conditions Cockayne syndrome (CS) and trichothiodystrophy (TTD). In the latter two, the basal transcription function of TFIIH is also presumed to be affected. Here we report four unusual TTD patients with fever-dependent reversible deterioration of TTD features such as brittle hair. Cells from these patients show an in vivo temperature-sensitive defect of transcription and DNA repair due to thermo-instability of TFIIH. Our findings reveal the clinical consequences of impaired basal transcription and mutations in very fundamental processes in humans, which previously were only known in lower organisms.

BackgroundRadiation is an effective anti-cancer therapy but leads to severe late radiation toxicity in 5%–10% of patients. Assuming that genetic susceptibility impacts this risk, we hypothesized that the cellular response of normal tissue to X-rays could discriminate patients with and without late radiation toxicity.Methods and FindingsProstate carcinoma patients without evidence of cancer 2 y after curative radiotherapy were recruited in the study. Blood samples of 21 patients with severe late complications from radiation and 17 patients without symptoms were collected. Stimulated peripheral lymphocytes were mock-irradiated or irradiated with 2-Gy X-rays. The 24-h radiation response was analyzed by gene expression profiling and used for classification. Classification was performed either on the expression of separate genes or, to augment the classification power, on gene sets consisting of genes grouped together based on function or cellular colocalization.X-ray irradiation altered the expression of radio-responsive genes in both groups. This response was variable across individuals, and the expression of the most significant radio-responsive genes was unlinked to radiation toxicity. The classifier based on the radiation response of separate genes correctly classified 63% of the patients. The classifier based on affected gene sets improved correct classification to 86%, although on the individual level only 21/38 (55%) patients were classified with high certainty. The majority of the discriminative genes and gene sets belonged to the ubiquitin, apoptosis, and stress signaling networks. The apoptotic response appeared more pronounced in patients that did not develop toxicity. In an independent set of 12 patients, the toxicity status of eight was predicted correctly by the gene set classifier.ConclusionsGene expression profiling succeeded to some extent in discriminating groups of patients with and without severe late radiotherapy toxicity. Moreover, the discriminative power was enhanced by assessment of functionally or structurally related gene sets. While prediction of individual response requires improvement, this study is a step forward in predicting susceptibility to late radiation toxicity.

The chicken anemia virus protein apoptin induces a p53-independent, Bcl-2-insensitive type of apoptosis in various human tumor cells. Here, we show that, in vitro, apoptin fails to induce programmed cell death in normal lymphoid, dermal, epidermal, endothelial, and smooth-muscle cells. However, when normal cells are transformed they become susceptible to apoptosis by apoptin. Long-term expression of apoptin in normal human fibroblasts revealed that apoptin has no toxic or transforming activity in these cells. In normal cells, apoptin was found predominantly in the cytoplasm, whereas in transformed and malignant cells it was located in the nucleus, suggesting that the localization of apoptin is related to its activity. These properties make apoptin a potential agent for the treatment of a large number of tumors, also those lacking p53 and͞or overexpressing Bcl-2.Apoptosis (or programmed cell death) is an active and programmed physiological process for eliminating superfluous, altered, or malignant cells (1). Apoptosis is characterized by shrinkage of cells, segmentation of the nucleus, condensation, and cleavage of DNA into domain-sized fragments in most cells followed by internucleosomal degradation. Finally, the apoptotic cells fragment into membrane-enclosed bodies, which are rapidly phagocytosed by neighboring cells (2-4).The apoptotic process can be initiated by a variety of regulatory stimuli (5, 6). Changes in cell-survival rate play an important role in human pathogenesis, e.g. in cancer development, which is caused by enhanced cell proliferation but also by decreased cell death (7-10). A variety of chemotherapeutic agents and radiation have been demonstrated to induce apoptosis in tumor cells, in many instances via the action of wild-type p53 (11-15). Most tumors, however, acquire a mutation in p53 during their development, often correlated with poor response to cancer therapy (16)(17)(18). In several leukemias a high expression level of the proto-oncogene Bcl-2 is associated with a strong resistance to various apoptosis-inducing chemotherapeutic agents (19)(20)(21)(22). Apoptin, a 14-kDa basic and proline-rich protein (23) derived from the chicken anemia virus, can induce apoptosis in chicken and human malignant cell lines (24,25). We have established that apoptosis induced by apoptin is p53-independent (26) and cannot be blocked by 28). Therefore, apoptin is a potential antitumor agent. To explore this possibility further, we have examined the in vitro apoptotic activity of apoptin in normal human cells versus transformed human cells. MATERIALS AND METHODSCell Culture. Human primary T cells were isolated from six normal blood donors by Ficol centrifugation and grown in RPMI medium 1640 containing 6% human serum and 0.8 g͞ml phytohemagglutinin. After 3 days, the medium was changed, and 300 units͞ml of interleukin-2 were added (29). Human umbilical-cord vascular endothelial cells (HUVEC) and smooth-muscle cells (HSMC) were isolated from umbilical cords as described (30). HUVEC were grown in M199 ...

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