Decreased Selenium-binding Protein 1 in Esophageal Adenocarcinoma Results from Posttranscriptional and Epigenetic Regulation and Affects Chemosensitivity

Purpose: The chemopreventive effects of selenium have been extensively examined, but its role in cancer development or as a chemotherapeutic agent has only recently been explored. Because selenium-binding protein 1 (SELENBP1, SBP1, hSP56) has been shown to bind selenium covalently and selenium deficiency has been associated with esophageal adenocarcinoma (EAC), we examined its role in EAC development and its potential effect on chemosensitivity in the presence of selenium.

Experimental Design: SELENBP1 expression level and copy number variation were determined by oligonucleotide microarrays, real-time reverse transcription-PCR, tissue microarrays, immunoblotting, and single-nucleotide polymorphism arrays. Bisulfite sequencing and sequence analysis of reverse transcription-PCR-amplified products explored epigenetic and posttranscriptional regulation of SELENBP1 expression, respectively. WST-1 cell proliferation assays, senescence-associated beta-galactosidase staining, immunoblotting, and flow cytometry were done to evaluate the biological significance of SELENBP1 overexpression in selenium-supplemented EAC cells.

Results: SELENBP1 expression decreased significantly in Barrett's esophagus to adenocarcinoma progression. Both epigenetic and posttranscriptional mechanisms seemed to modulate SELENBP1 expression. Stable overexpression of SELENBP1 in methylseleninic acid-supplemented Flo-1 cells resulted in enhanced apoptosis, increased cellular senescence, and enhanced cisplatin cytotoxicity. Although inorganic sodium selenite similarly enhanced cisplatin cytotoxicity, these two forms of selenium elicited different cellular responses.

Conclusions: SELENBP1 expression may be an important predictor of response to chemoprevention or chemosensitization with certain forms of selenium in esophageal tissues. AACR.