Glycobiomarker, Fucosylated Short-Form Secretogranin III Levels Are Increased in Serum of Patients with Small Cell Lung Carcinoma

Secretogranin III (SgIII) is a member of the chromogranin/secretogranin family of neuroendocrine secretory proteins. Granins are expressed in endocrine and neuroendocrine cells and subsequently processed into bioactive hormones. Although granin-derived peptide expression is correlated with neuroendocrine carcinomas, little is known about SgIII. We previously identified SgIII by a comparative glycoproteomics approach for elucidation of glycobiomarker candidates in lung carcinoma. Here, we examined the expression, secretion, and glycosylation of SgIII to identify novel biomarkers of small cell lung carcinoma (SCLC). In comparative immunohistochemical analysis and secretion profiling, SgIII was observed in all types of lung cancer. However, low-molecular-weight SgIII (short-form SgIII) was specifically found in SCLC culture medium. Glycoproteomics analysis showed that a fucosylated glycan was attached to the first of three potential N-glycosylation sites and an unfucosylated glycan was detected on the second...