Association of anti-apoptotic Mcl-1L isoform expression with radioresistance of oral squamous carcinoma cells

• Published in: Radiation oncology (London, England) England), 2012-08, Vol.7 (1), p.135-135, Article 135
• Main Authors: Palve, Vinayak C, Teni, Tanuja R
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Apoptosis; Apoptosis - radiation effects; bcl-2-Associated X Protein - genetics; bcl-2-Associated X Protein - metabolism; bcl-X Protein - genetics; bcl-X Protein - metabolism; Biotechnology; Blotting, Western; Cancer; Carcinoma, Squamous Cell - genetics; Carcinoma, Squamous Cell - pathology; Carcinoma, Squamous Cell - radiotherapy; Cell culture; Cell Proliferation - radiation effects; Cobalt Radioisotopes - adverse effects; Deoxyribonucleic acid; DNA; Flow Cytometry; Fluorescent Antibody Technique; Humans; Mouth Neoplasms - genetics; Mouth Neoplasms - pathology; Mouth Neoplasms - radiotherapy; Myeloid Cell Leukemia Sequence 1 Protein; Oral cancer; Protein Isoforms; Proteins; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Proto-Oncogene Proteins c-bcl-2 - physiology; Radiation therapy; Radiation Tolerance - physiology; Radiation, Ionizing; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Small Interfering - genetics; Studies; Tumor Cells, Cultured; Tumor Stem Cell Assay; Tumors
• ISSN: 1748-717X; 1748-717X
• DOI: 10.1186/1748-717X-7-135

Oral cancer is a common cancer and a major health problem in the Indian subcontinent. At our laboratory Mcl-1, an anti-apoptotic member of the Bcl-2 family has been demonstrated to be overexpressed in oral cancers and to predict outcome in oral cancer patients treated with definitive radiotherapy. To study the role of Mcl-1 isoforms in radiation response of oral squamous carcinoma cells (OSCC), we investigated in the present study, the association of Mcl-1 isoform expression with radiosensitivity of OSCC, using siRNA strategy. The time course expression of Mcl-1 splice variants (Mcl-1L, Mcl-1S & Mcl-1ES) was studied by RT-PCR, western blotting & immunofluorescence, post-irradiation in oral cell lines [immortalized FBM (radiosensitive) and tongue cancer AW8507 & AW13516 (radioresistant)]of relatively differing radiosensitivities. The effect of Mcl-1L knockdown alone or in combination with ionizing radiation (IR) on cell proliferation, apoptosis & clonogenic survival, was investigated in AW8507 & AW13516 cells. Further the expression of Mcl-1L protein was assessed in radioresistant sublines generated by fractionated ionizing radiation (FIR). Three to six fold higher expression of anti-apoptotic Mcl-1L versus pro-apoptotic Mcl-1S was observed at mRNA & protein levels in all cell lines, post-irradiation. Sustained high levels of Mcl-1L, downregulation of pro-apoptotic Bax & Bak and a significant (P