Male breast cancer: diagnosis stages, treatment and survival in a country with limited resources (Burkina Faso).

BACKGROUND: Male breast cancer is a rare and less known disease. Therapeutic modalities affect survival. In Burkina Faso, male breast cancers are diagnosed in everyday practice, but the prognosis at short-, middle-, and long-term remains unknown. The objective of this study is to study the diagnosis stages, therapeutic modalities, and 5-year survival in male breast cancer at the General Surgery Unit of Yalgado Ouedraogo University Hospital from 1990 to 2009. METHODS: A cohort longitudinal study concerning cases of breast cancer diagnosed in man. Survival was assessed using the Kaplan-Meier method and survival curves were compared through the LogRank test. RESULTS: Fifty-one cases of male breast cancer were followed-up, i.e., 2.6% of all breast cancers. Stages III and IV represented 88% of cases. Eleven patients (21.6%) were at metastatic stage. Patients were operated in 60.8% of cases. The surgery included axillary dissection in 25 (80.6%) out of 31 cases. Lumpectomy was performed on 6.5% of patients (2 cases). Fifteen (29.4%) and 11 (21.6%) patients underwent chemotherapy and hormonal therapy, respectively. The FAC protocol was mostly used. Radiation therapy was possible in two cases. The median deadline for follow-up was 14.8 months. A local recurrence was noticed in 3.2% of cases. The overall 5-year survival rate was 49.9%. The median survival was over 5 years for stages I and II. It was 54 down to 36 months for stages III and IV. CONCLUSION: Diagnosis is late. The lack of immunohistochemistry makes it difficult to define the proportion of their hormonal dependence. Surgery is the basic treatment. Five-year survival is slow and the median survival depends on the diagnosis stage. It can be improved through awareness-raising campaigns and the conduct of individual screening.

What histone code for DNA repair?

Chromatin structure plays a key role in most processes involving DNA metabolism. Chromatin modifications implicated in transcriptional regulation are relatively well characterized and are thought to be the result of a code on the histone proteins (histone code). This code, involving phosphorylation, ubiquitylation, sumoylation, acetylation and methylation, is believed to regulate chromatin accessibility either by disrupting chromatin contacts or by recruiting non-histone proteins to chromatin. Recent evidences suggest that such mechanisms are also involved in DNA damage detection and DNA repair. One of the most well-characterized modifications is caused by the formation of DNA double strand breaks (DSBs), resulting in phosphorylation of histone H2AX (the so-called gamma-H2AX) on the chromatin surrounding the DNA lesion. It is generally believed that histone H2AX phosphorylation is required for the concentration and stabilization of DNA repair proteins to the damaged chromatin. The phosphorylation of this histone seems to play a role in both non-homologous end-joining (NHEJ) and homologous recombination (HR) repair pathways. However, the choice of the repair pathway might depend on or induce additional post-translational modifications affecting other histone proteins necessary to the completion of the entire DNA repair process. Interestingly, even in the absence of DSBs, histone modifications occur. Indeed, following UV-exposure, histone acetylation takes place and is believed to facilitate the nucleotide excision repair (NER) process by promoting chromatin accessibility to the repair factors. This review focuses on recent data characterizing the function of histone modification in various repair processes and discusses if the combination of such modifications can be the trademark of a specific DNA repair pathway.

Low cytotoxicity of ecteinascidin 743 in yeast lacking the major endonucleolytic enzymes of base and nucleotide excision repair pathways.

Ecteinascidin 743 (ET-743) is a promising antitumoral drug for the treatment of soft tissues sarcomas, becoming a good candidate for clinical trials. However, the molecular mechanism of how ET-743 induces cells death is poorly understood. The chemical structure of ET-743 suggests that it can form cytotoxic cross-links with proteins and DNA. Experiments with Escherichia coli and mammalian cells indicate that the nucleotide excision repair (NER) pathway promotes ET-743 cytotoxicity. We therefore analyzed cytotoxicity and tolerance to ET-743 in the yeast Saccharomyces cerevisiae, defective for NER and/or base excision repair (BER), either in single mutants or in combination with mutant alleles of genes encoding proteins involved in DNA translesion synthesis (TLS) and homologous recombination (HR). Treatment of haploid and diploid S. cerevisiae strains with ET-743 led to induced mutagenesis, mitotic gene conversion, and crossing-over. The results indicated that yeast strains lacking endonucleases of the NER and BER pathways are especially resistant for ET-743. The mutagenesis data points to a weak mutagenic activity of ET-743 in both WT and strains lacking BER/NER endonuclease, and that a mutant blocked in both BER and TLS totally lacks induced mutagenesis. The diploid strain shows an increase in the frequencies of crossing-over and mitotic recombination. These data lead us to propose a model for ET-743 action in eukaryotic cells, where the presence of BER and NER endonucleases results in cell death. However, ET-743 damage can be tolerated in BER and/or NER mutants by TLS (error-prone) or in combination with HR (error-free).

Influence of irofulven, a transcription-coupled repair-specific antitumor agent, on RNA polymerase activity, stability and dynamics in living mammalian cells.

Transcription-coupled repair (TCR) plays a key role in the repair of DNA lesions induced by bulky adducts and is initiated when the elongating RNA polymerase II (Pol II) stalls at DNA lesions. This is accompanied by alterations in Pol II activity and stability. We have previously shown that the monofunctional adducts formed by irofulven (6-hydroxymethylacylfulvene) are exclusively recognized by TCR, without involvement of global genome repair (GGR), making irofulven a unique tool to characterize TCR-associated processes in vivo. Here, we characterize the influence of irofulven on Pol II activity, stability and mobility in living mammalian cells. Our results demonstrate that irofulven induces specific inhibition of nucleoplasmic RNA synthesis, an important decrease of Pol II mobility, coupled to the accumulation of initiating polymerase and a time-dependent loss of the engaged enzyme, associated with its polyubiquitylation. Both proteasome-mediated degradation of the stalled polymerase and new protein synthesis are necessary to allow Pol II recycling into preinitiating complexes. Together, our findings provide novel insights into the subsequent fate of the stalled RNA polymerase II and demonstrate the essential role of the recycling process for transcriptional reinitiation and viability of mammalian cells.

Replication and homologous recombination repair regulate DNA double-strand break formation by the antitumor alkylator ecteinascidin 743.

Adducts induced by the antitumor alkylator ecteinascidin 743 (ET-743, Yondelis, trabectedin) represent a unique challenge to the DNA repair machinery because no pathway examined to date is able to remove the ET adducts, whereas cells deficient in nucleotide excision repair show increased resistance. We here describe the processing of the initial ET adducts into cytotoxic lesions and characterize the influence of cellular repair pathways on this process. Our findings show that exposure of proliferating mammalian cells to pharmacologically relevant concentrations of ET-743 is accompanied by rapid formation of DNA double-strand breaks (DSBs), as shown by the neutral comet assay and induction of focalized phosphorylated H2AX. The ET adducts are stable and can be converted into DSBs hours after the drug has been removed. Loss of homologous recombination repair has no influence on the initial levels of DSBs but is associated with the persistence of unrepaired DSBs after ET-743 is removed, resulting in extensive chromosomal abnormalities and pronounced sensitivity to the drug. In comparison, loss of nonhomologous end-joining had only modest effect on the sensitivity. The identification of DSB formation as a key step in the processing of ET-743 lesions represents a novel mechanism of action for the drug that is in agreement with its unusual potency. Because loss of repair proteins is common in human tumors, expression levels of selected repair factors may be useful in identifying patients particularly likely to benefit, or not, from treatment with ET-743.

Avaliação de compostos com atividade antioxidante em células da levedura Saccharomyces cerevisiae / Evaluation of compounds with antioxidant activity in Saccharomyces cerevisiae yeast cells

Antioxidantes são compostos que atuam inibindo e/ou diminuindo os efeitos desencadeados pelos radicais livres e compostos oxidantes. Diferentes métodos têm sido desenvolvidos para obter a diferenciação, seja qualitativa ou quantitativa, da capacidade antioxidante de compostos, tanto através de testes sem a utilização de células (testes químicos) ou utilizando culturas celulares (testes biológicos). Os testes químicos são mais rápidos e simples de serem executados. No entanto, não são representativos das condições celulares do homem. Ensaios microbianos `in vivo' utilizando-se, principalmente, células eucarióticas da levedura Saccharomyces cerevisiae têm se mostrado muito adequados para determinação da capacidade antioxidante de diferentes compostos, fornecendo resultados rápidos, reprodutíveis e passíveis de serem correlacionados ao observado no homem. O objetivo deste trabalho foi avaliar a capacidade antioxidante do ácido L-ascórbico, vitamina E (alfa-tocoferol) e dos flavonóides hesperidina, naringina, naringenina, quercetina, rutina e sakuranetina, utilizando como modelo de sistema biológico a levedura S. cerevisiae. Para realização dos testes, as células foram tratadas com o agente estressor apomorfina em presença e ausência das amostras. Os resultados mostraram que a rutina, hesperidina, sakuranetina, quercetina e naringina foram os compostos com maior atividade antioxidante, seguidos da naringenina e vitamina E. O ácido L-ascórbico e a mistura de ácido L-ascórbico e vitamina E não mostraram atividade antioxidante frente aos danos gerados pela apomorfina nas concentrações ensaiadas.

Avaliação do estresse oxidativo e contaminação por chumbo em praticantes de tiro esportivo / Oxidative stress evaluation and lead contamination in marksmen

O chumbo, metal utilizado na fabricação de munições, pode depletar a glutationa e gerar espécies reativas de oxigênio capazes de desencadear reações de peroxidação lipídica. Neste trabalho, avaliou-se uma possível correlação entre chumbo e estresse oxidativo em praticantes de tiro esportivo nas modalidades ao ar livre, indoor e não-atiradores. A concentração de chumbo sangüínea foi determinada por absorção atômica, a peroxidação lipídica pela concentração dos produtos de reação com o ácido tiobarbitúrico (TBARS) e a capacidade antioxidante total foi avaliada utilizando-se o kit Total Antioxidant Status (RANDOXÒ). Os resultados mostraram que 12,5 por cento dos atiradores ao ar livre e 20,8 por cento indoor apresentaram valores sangüíneos de chumbo acima dos considerados normais para grupos não-expostos. Os valores de TBARS mostraram-se significativamente maiores nos praticantes de tiro. A capacidade antioxidante total medida no soro dos indivíduos dos três grupos amostrados não se mostrou alterada