Madhura G Kelkar1,2, Bhushan Thakur3,2, Abhishek Derle1, Sushmita Chatterjee1, Pritha Ray3,2, Abhijit De4,5. 1. Molecular Functional Imaging Lab, Tata Memorial Centre, ACTREC, Sector 22, Kharghar, Navi Mumbai, 410210, India. 2. Homi Bhabha National Institute, Anushakti Nagar, Mumbai, India. 3. Imaging Cell Signaling and Therapeutics Lab, Tata Memorial Centre, ACTREC, Navi Mumbai, India. 4. Molecular Functional Imaging Lab, Tata Memorial Centre, ACTREC, Sector 22, Kharghar, Navi Mumbai, 410210, India. ade@actrec.gov.in. 5. Homi Bhabha National Institute, Anushakti Nagar, Mumbai, India. ade@actrec.gov.in.
Abstract
PURPOSE: Aberrant expression of human sodium iodide symporter (NIS) in breast cancer (BC) is well documented but the transcription factors (TF) regulating its aberrant expression is poorly known. We identify the presence of three p53 binding sites on the human NIS promoter sequence by conducting genome-wide TF analysis, and further investigate their regulatory role. METHODS: The differences in transcription and translation were measured by real-time PCR, luciferase reporter assay, site-directed mutagenesis, in vivo optical imaging, and chromatin immunoprecipitation. The relation of NIS and p53 in clinical samples was judged by TCGA data analysis and immunohistochemistry. RESULTS: Overexpression of wild-type p53 as a transgene or pharmacological activation by doxorubicin drug treatment shows significant suppression of NIS transcription in multiple BC cell types which also results in lowered NIS protein content and cellular iodide intake. NIS repression by activated p53 is further confirmed by non-invasive bioluminescence imaging in live cell and orthotropic tumor model. Abrogation of p53-binding sites by directional mutagenesis confirms reversal of transcriptional activity in wild-type p53-positive BC cells. We also observe direct binding of p53 to these sites on the human NIS promoter. Importantly, TCGA data analysis of NIS and p53 co-expression registers an inverse relationship between the two candidates. CONCLUSION: Our data for the first time highlight the role of p53 as a negative regulator of functional NIS expression in BC, where the latter is a potential targeted radioiodine therapy candidate. Thus, the study provides an important insight into prospective clinical application of this approach that may significantly impact the patient with mutant versus wild-type p53 profile.
PURPOSE: Aberrant expression of humansodium iodide symporter (NIS) in breast cancer (BC) is well documented but the transcription factors (TF) regulating its aberrant expression is poorly known. We identify the presence of three p53 binding sites on the humanNIS promoter sequence by conducting genome-wide TF analysis, and further investigate their regulatory role. METHODS: The differences in transcription and translation were measured by real-time PCR, luciferase reporter assay, site-directed mutagenesis, in vivo optical imaging, and chromatin immunoprecipitation. The relation of NIS and p53 in clinical samples was judged by TCGA data analysis and immunohistochemistry. RESULTS: Overexpression of wild-type p53 as a transgene or pharmacological activation by doxorubicin drug treatment shows significant suppression of NIS transcription in multiple BC cell types which also results in lowered NIS protein content and cellular iodide intake. NIS repression by activated p53 is further confirmed by non-invasive bioluminescence imaging in live cell and orthotropic tumor model. Abrogation of p53-binding sites by directional mutagenesis confirms reversal of transcriptional activity in wild-type p53-positive BC cells. We also observe direct binding of p53 to these sites on the humanNIS promoter. Importantly, TCGA data analysis of NIS and p53 co-expression registers an inverse relationship between the two candidates. CONCLUSION: Our data for the first time highlight the role of p53 as a negative regulator of functional NIS expression in BC, where the latter is a potential targeted radioiodine therapy candidate. Thus, the study provides an important insight into prospective clinical application of this approach that may significantly impact the patient with mutant versus wild-type p53 profile.