Ladislav Andera

Bio: Ladislav Andera is an academic researcher from French Institute of Health and Medical Research. The author has contributed to research in topics: DNA repair & DNA damage. The author has an hindex of 1, co-authored 1 publications receiving 56 citations.

Transcription abnormalities potentiate apoptosis of normal human fibroblasts

Abstract: Apoptosis is a natural process by which damaged and potentially tumorigenic cells are removed Induction of apoptosis is important in chemotherapy aimed at eliminating cancer cells We address the mechanisms by which this process can be triggered in cells that are recalcitrant to cell death induced by DNA-damaging agents Normal human fibroblasts and lymphoblasts, and fibroblasts with defined genetic changes, were treated with DNA-damaging agents and inhibitors of transcription Western blotting was used to study the expression of some of the key factors involved in the response to DNA damage and the induction of apoptosis, namely, p53, p21WAF1,Cip1, Mdm2, Bax, and CD95 (Fas/APO1) Apoptosis was followed by various criteria, including DNA fragmentation, specific proteolysis, cell morphology, viability, and FACS scan for sub-G1 cells Normal human fibroblasts were more resistant than lymphoblasts to DNA damage-induced apoptosis The DNA-damaging agents mitomycin C and cisplatin induced rapid apoptosis of fibroblasts with defects in the repair of transcribed DNA, compared with wild-type cells or those with defects in overall genome repair Short-term treatment with inhibitors of RNA polymerase II transcription, actinomycin D, and α-amanitin induced rapid cell death of normal fibroblasts These results show that there is a link between defective transcription and apoptosis Treatments and genetic backgrounds that favored apoptosis were associated with efficient and prolonged induction of p53 and often altered or unbalanced expression of its downstream effectors p21WAF1,Cip1 and Mdm2, whereas there were no changes in Bax or CD95 (Fas/APO1) Transcription inhibitors increase p53 levels and are better inducers of apoptosis than DNA-damaging agents in some cell types Apoptosis might be triggered by blocked polymerases and/or faulty expression of downstream effectors

DNA damage and the balance between survival and death in cancer biology

Abstract: DNA is vulnerable to damage resulting from endogenous metabolites, environmental and dietary carcinogens, some anti-inflammatory drugs, and genotoxic cancer therapeutics. Cells respond to DNA damage by activating complex signalling networks that decide cell fate, promoting not only DNA repair and survival but also cell death. The decision between cell survival and death following DNA damage rests on factors that are involved in DNA damage recognition, and DNA repair and damage tolerance, as well as on factors involved in the activation of apoptosis, necrosis, autophagy and senescence. The pathways that dictate cell fate are entwined and have key roles in cancer initiation and progression. Furthermore, they determine the outcome of cancer therapy with genotoxic drugs. Understanding the molecular basis of these pathways is important not only for gaining insight into carcinogenesis, but also in promoting successful cancer therapy. In this Review, we describe key decision-making nodes in the complex interplay between cell survival and death following DNA damage.

Disruption of the nucleolus mediates stabilization of p53 in response to DNA damage and other stresses

Abstract: p53 protects against cancer through its capacity to induce cell cycle arrest or apoptosis under a large variety of cellular stresses. It is not known how such diversity of signals can be integrated by a single molecule. However, the literature reveals that a common denominator in all p53-inducing stresses is nucleolar disruption. We thus postulated that the impairment of nucleolar function might stabilize p53 by preventing its degradation. Using micropore irradiation, we demonstrate that large amounts of nuclear DNA damage fail to stabilize p53 unless the nucleolus is also disrupted. Forcing nucleolar disruption by anti-upstream binding factor (UBF) microinjection (in the absence of DNA damage) also causes p53 stabilization. We propose that the nucleolus is a stress sensor responsible for maintenance of low levels of p53, which are automatically elevated as soon as nucleolar function is impaired in response to stress. Our model integrates all known p53-inducing agents and also explains cell cycle-related variations in p53 levels which correlate with established phases of nucleolar assembly/disassembly through the cell cycle.

Inhibition of RNA polymerase II as a trigger for the p53 response

Abstract: The mechanisms by which the p53 response is triggered following exposure to DNA-damaging agents have not yet been clearly elucidated. We and others have previously suggested that blockage of RNA polymerase II may be the trigger for induction of the p53 response following exposure to ultraviolet light. Here we report on the correlation between inhibition of mRNA synthesis and the induction of p53, p21 WAF1 and apoptosis in diploid human fibroblasts treated with either UV light, cisplatin or the RNA synthesis inhibitors actinomycin D, DRB, H7 and a-amanitin. Exposure to ionizing radiation or the proteasome inhibitor LLnL, however, induced p53 and p21 WAF1 without aAecting mRNA synthesis. Importantly, induction of p53 by the RNA synthesis or proteasome inhibitors did not correlate with the induction of DNA strand breaks. Furthermore, cisplatin-induced accumulation of active p53 in repair-deficient XP-A cells occurred despite the lack of DNA strand break induction. Our results suggest that the induction of the p53 response by certain toxic agents is not triggered by DNA strand breaks but rather, may be linked to inhibition of mRNA synthesis either directly by the poisoning of RNA polymerase II or indirectly by the induction of elongation-blocking DNA lesions.

Transcription - guarding the genome by sensing DNA damage.

Abstract: Cells induce the expression of DNA-repair enzymes, activate cell-cycle checkpoints and, under some circumstances, undergo apoptosis in response to DNA-damaging agents. The mechanisms by which these cellular responses are triggered are not well understood, but there is recent evidence that the transcription machinery might be used in DNA-damage surveillance and in triggering DNA-damage responses to suppress mutagenesis. Transcription might also act as a DNA-damage dosimeter where the severity of blockage determines whether or not to induce cell death. Could transcription therefore be a potential therapeutic target for anticancer strategies?

Vitamin E succinate is a potent novel antineoplastic agent with high selectivity and cooperativity with tumor necrosis factor-related apoptosis-inducing ligand (Apo2 ligand) in vivo.

Abstract: Alpha-tocopheryl succinate (alpha-TOS), a redox-inactive analogue of vitamin E, is a strong inducer of apoptosis, whereas alpha-tocopherol (alpha-TOH) lacks apoptogenic activity (J. Neuzil et al., FASEB J., 15: 403-415, 2001). Here we investigated the possible antineoplastic activities of alpha-TOH and alpha-TOS and further explored the potential of alpha-TOS as an antitumor agent. Using nude mice with colon cancer xenografts, we found that alpha-TOH exerted modest antitumor activity and acted by inhibiting tumor cell proliferation. In contrast, alpha-TOS showed a more profound antitumor effect, at both the level of inhibition of proliferation and induction of tumor cell apoptosis. alpha-TOS was nontoxic to normal cells and tissues, triggered apoptosis in p53(-/-) and p21(Waf1/Cip1(-/-)) cancer cells, and exerted a cooperative proapoptotic activity with tumor necrosis factor-related apoptosis-inducing ligand (Apo2 ligand) due to differences in proapoptotic signaling. Finally, alpha-TOS cooperated with tumor necrosis factor-related apoptosis-inducing ligand in suppression of tumor growth in vivo. Vitamin E succinate is thus a potent and highly specific anticancer agent and/or adjuvant of considerable therapeutic potential.