Stathmin 1, a marker of PI3K pathway activation and regulator of microtubule dynamics, is expressed in early pelvic serous carcinomas

BackgroundMost high-grade pelvic serous carcinomas (HGPSCs) arise from fallopian tube epithelium (FTE). To date, few markers have been shown to characterize FTE transformation. Stathmin 1 (STMN1) is a candidate oncogene whose activity is influenced by p53, p27Kip1 (p27), and PI3K/Akt pathway activation. As a microtubule destabilizing protein, STMN1 regulates cytoskeletal dynamics, cell cycle progression, mitosis, and cell migration. This study examines the expression of STMN1 and its negative regulator p27 along the morphologic continuum from normal FTE to invasive carcinoma.MethodsSTMN1 and p27 expression were examined by immunohistochemistry (IHC) in benign (n = 12) and malignant (n = 13) fallopian tubes containing normal epithelium, morphologically benign putative precursor lesions (“p53 signatures”), potential transitional precursor lesions (“proliferative p53 signatures”), tubal intraepithelial carcinoma (TIC), and/or invasive serous carcinoma. STMN1 expression was further assessed in 131 late-stage HGPSCs diagnosed as primary ovarian and in 6 ovarian cancer cell lines by IHC and Western blot, respectively.ResultsSTMN1 expression was absent in benign FTE and infrequently detected in p53 signatures. However, it was weakly expressed in proliferative p53 signatures and robustly induced upon progression to TIC and invasive carcinoma, typically accompanied by decreased p27 levels. STMN1 was expressed in > 80% of high-grade serous ovarian carcinomas and cell lines.ConclusionsSTMN1 is a novel marker of early serous carcinoma that may play a role in FTE tumor initiation. Our data are consistent with a model by which STMN1 overexpression, resulting from loss of p27-mediated regulation, may potentiate aberrant cell proliferation, migration, and/or loss of polarity during early tumorigenesis.

Research highlights
► STMN1 is strongly expressed in early serous carcinomas of the fallopian tube.
► STMN1 expression inversely correlates with that of its negative regulator p27Kip1.
► STMN1 may play a key role in high-grade pelvic serous tumor initiation.