RESUMO
Apoptosis is a major mechanism of treatment-induced T-cell depletion in leukemia and autoimmune diseases. While 'classical' apoptosis is considered to depend on caspase activation, caspase-independent death is increasingly recognized as an alternative pathway. Although the DNA-damaging drug cyclophosphamide (CY) is widely used for therapy of hematological malignancies and autoimmune disorders, the molecular mechanism of apoptosis induction remains largely unknown. Here, we report that treatment of Jurkat, cytotoxic, and primary leukemic T cells with an activated analog of CY, 4-hydroperoxy-cyclophosphamide (4-OOH-CY), induces caspase activation and typical features of apoptosis, although cell death was not prevented by caspase inhibition. Also depletion of murine thymocytes and splenocytes after CY treatment in vivo was not inhibited by Z-Val-Ala-DL-Asp-fluoromethylketone (Z-VAD.fmk). Caspase-8 and receptor-induced protein (RIP) were dispensable for 4-OOH-CY-mediated apoptosis, while overexpression of Bcl-2 was partially protective. 4-OOH-CY treatment induced reactive oxygen species production, upregulation of Bax, and nuclear relocation of the mitochondrial factors apoptosis-inducing factor (AIF) and endonuclease G (EndoG). The antioxidant N-acetyl-L-cysteine substantially inhibited conformational changes of Bax, loss of mitochondrial membrane potential, nuclear relocation of mitochondrial factors, and apoptosis induction in 4-OOH-CY-treated T cells. These results strongly indicate that oxidative damage-induced nuclear translocation of AIF and EndoG in 4-OOH-CY-treated T cells might represent an alternative death pathway in the absence of caspase activity.
Assuntos
Fator de Indução de Apoptose/metabolismo , Apoptose , Núcleo Celular/metabolismo , Ciclofosfamida/análogos & derivados , Endodesoxirribonucleases/metabolismo , Estresse Oxidativo , Linfócitos T/efeitos dos fármacos , Acetilcisteína/farmacologia , Transporte Ativo do Núcleo Celular , Animais , Caspases/metabolismo , Células Cultivadas , Ciclofosfamida/farmacologia , Sequestradores de Radicais Livres/farmacologia , Humanos , Imunossupressores/farmacologia , Células Jurkat , Camundongos , Camundongos Endogâmicos BALB C , Mitocôndrias/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Linfócitos T/fisiologia , Linfócitos T Citotóxicos/efeitos dos fármacos , Linfócitos T Citotóxicos/fisiologia , Proteína Supressora de Tumor p53/antagonistas & inibidoresRESUMO
A 58-year-old woman presented with respiratory problems 6 months after she had had a squamous cell carcinoma in the oral cavity resected. We found on computed tomography a large lesion in the cardiac muscle. There were no abnormalities in the electrocardiogram. The patient died 7 days later and necropsy confirmed a solitary metastasis in the myocardium that originated from a squamous cell carcinoma of the mouth.
Assuntos
Carcinoma de Células Escamosas/secundário , Neoplasias Cardíacas/secundário , Neoplasias Bucais/patologia , Evolução Fatal , Feminino , Humanos , Pessoa de Meia-IdadeRESUMO
By hybridizing total human DNA with probes derived from the extrachromosomal circular DNA fraction of cultured cells, we detected a human multisequence family, called chAB4, previously unknown. Approximately 50 copies of this sequence are located in the haploid human genome. The repetition units of chAB4 are 35 kb long and the units are tandemly arranged. DNA sequence analysis of parts of the chAB4 unit revealed no direct evidence for a possible function of the family, but possibly chAB4 harbors a gene. Family members are located on human chromosomes 1, 3, and 9 and on the short arms of chromosomes 13-15, 21, and 22. Therefore, in addition to the rDNA, chAB4 is the second class of clustered repetitive sequences with a relatively long repetition unit localized on the short arms of all acrocentric chromosomes. Some evolutionary aspects arising from the structure of chAB4, the established parts of its DNA sequences, and the chromosomal localization of this new multisequence family are discussed.