RESUMO
An involvement of components of DNA-break repair (DBR) complex including DNA-dependent protein kinase (DNA-PK) and poly-ADP-ribose polymerase 1 (PARP-1) in transcription regulation in response to distinct cellular signalling has been revealed by different laboratories. Here, we explored the involvement of DNA-PK and PARP-1 in the heat shock induced transcription of Hsp70A1A. We find that inhibition of both the catalytic subunit of DNA-PK (DNA-PKc), and Ku70, a regulatory subunit of DNA-PK holo-enzyme compromises transcription of Hsp70A1A under heat shock treatment. In immunoprecipitation based experiments we find that Ku70 or DNA-PK holoenzyme associates with NFκB. This NFκB associated complex also carries PARP-1. Downregulation of both NFκB and PARP-1 compromises Hsp70A1A transcription induced by heat shock treatment. Alteration of three bases by site directed mutagenesis within the consensus κB sequence motif identified on the promoter affected inducibility of Hsp70A1A transcription by heat shock treatment. These results suggest that NFκB engaged with the κB motif on the promoter cooperates in Hsp70A1A activation under heat shock in human cells as part of a DBR complex including DNA-PK and PARP-1.
Assuntos
Reparo do DNA/genética , DNA Topoisomerases Tipo II/genética , Proteína Quinase Ativada por DNA/genética , Proteínas de Ligação a DNA/genética , Proteínas de Choque Térmico HSP70/genética , Subunidade p50 de NF-kappa B/genética , Poli(ADP-Ribose) Polimerase-1/genética , Fator de Transcrição RelA/genética , Domínio Catalítico/genética , Linhagem Celular Tumoral , Quebras de DNA , Proteína Quinase Ativada por DNA/metabolismo , Proteínas de Choque Térmico HSP70/biossíntese , Células HeLa , Humanos , Autoantígeno Ku/antagonistas & inibidores , Poli(ADP-Ribose) Polimerase-1/metabolismo , Regiões Promotoras Genéticas/genética , Interferência de RNA , RNA Interferente Pequeno/genética , Transcrição Gênica/genética , Regulação para Cima/genéticaRESUMO
AIM: Head and neck cancer is one of the most commonly occurring malignancies in the world. In India, the most commonly occurring head and neck cancers are those of the oral cavity and the pharynx. The majority of these cancers present with stage III/IV disease. Surgery and radiation therapy are the main treatment modalities. Concomitant chemoradiation is being investigated with the goal of improved local control that translates into improved survival. In this background, we have started this prospective randomized trial to ascertain the dose, schedule and sequence of therapy and to note whether Vinorelbine as radiosensitizer is equally effective as Cisplatin, comparing compliance, local control and toxicity. PATIENTS AND METHODS: Forty patients of advanced head and neck cancer were randomized into two arms. Arm A received weekly injection Cisplatin 40mg/m(2) along with radiation. Arm B received weekly injection of Vinorelbine 6mg/m(2) along with radiation. Radiotherapy was delivered at a dose of 6,600-7,000 Gy in conventional fractionation in a telecobalt machine. RESULTS: The complete response (CR) rate was higher in arm B (90%) than in arm A (70%). Major toxicities included neutropenia, anemia, mucositis and nausea. CONCLUSION: Concomitant chemoradiation with Vinorelbine produced more CR than chemoradiation with Cisplatin in advanced head and neck cancer. Toxicities were more in the Cisplatin arm, but they were manageable. Although a majority of the study was performed using Cisplatin as the radiosensitizer, Vinorelbine can be recommended as radiosensitizer in advanced head and neck malignancy.
