Aurora-A kinase is differentially expressed in the nucleus and cytoplasm in normal Müllerian epithelium and benign, borderline and malignant serous ovarian neoplasms.

BACKGROUND: Aurora-A kinase is important for cellular proliferation and is implicated in the tumorigenesis of several malignancies, including of the ovary. Information regarding the expression patterns of Aurora-A in normal Müllerian epithelium as well as benign, borderline and malignant epithelial ovarian neoplasms is limited. METHODS: We investigated Aurora-A expression by immunohistochemistry in 15 benign, 19 borderline and 17 malignant ovarian serous tumors, and 16 benign, 8 borderline, and 2 malignant ovarian mucinous tumors. Twelve fimbriae from seven patients served as normal Müllerian epithelium controls. We also examined Aurora-A protein expression by western blot in normal fimbriae and tumor specimens. RESULTS: All normal fimbriae (n = 12) showed nuclear but not cytoplasmic Aurora-A immunoreactivity by immunohistochemistry. Benign ovarian tumors also showed strong nuclear Aurora-A immunoreactivity. Forty-eight percent (13/27) of borderline tumors demonstrated nuclear Aurora-A immunoreactivity, while the remainder (52%, 14/27) lacked Aurora-A staining. Nuclear Aurora-A immunoreactivity was absent in all malignant serous tumors, however, 47% (8/17) demonstrated perinuclear cytoplasmic staining. These results were statistically significant when tumor class (benign/borderline/malignant) was compared to immunoreactivity localization or intensity (Fisher Exact Test, p < 0.01). Western blot analysis confirmed the greater nuclear Aurora-A expression in control Müllerian epithelium compared to borderline and malignant tumors. CONCLUSION: Aurora-A kinase is differentially expressed across normal Müllerian epithelium, benign and borderline serous and mucinous ovarian epithelial neoplasms and malignant serous ovarian tumors., with nuclear expression of unphosphorylated Aurora-A being present in normal and benign neoplastic epithelium, and lost in malignant serous neoplasms. Further studies of the possible biological and clinical implications of the loss of nuclear Aurora-A expression in ovarian tumors, and its role in ovarian carcinogenesis are warranted.

The selective Aurora-A kinase inhibitor MLN8237 (alisertib) potently inhibits proliferation of glioblastoma neurosphere tumor stem-like cells and potentiates the effects of temozolomide and ionizing radiation.

The selective Aurora-A kinase inhibitor MLN8237 is in clinical trials for hematologic malignancies, ovarian cancer and other solid tumors. We previously showed that MLN8237 is potently antiproliferative toward standard monolayer-cultured glioblastoma cells. We have now investigated the effect of MLN8237 with and without temozolomide or ionizing radiation on the proliferation of glioblastoma tumor stem-like cells (neurospheres) using soft agar colony formation assays and normal human astrocytes by MTT assay. Western blotting was utilized to compare MLN8237 IC50s to cellular Aurora-A and phosphoThr(288)Aurora-A levels. MLN8237 was more potently antiproliferative to neurosphere cells than to standard monolayer glioma cells, and was non-toxic to normal human astrocytes. Western blot analysis revealed that MLN8237 treatment inhibits phosphoThr(288)Aurora-A levels providing proof of drug target-hit in glioblastoma cells. Furthermore, phosphoThr(288)Aurora-A levels partially predicted the antiproliferative efficacy of MLN8237. We also found that Aurora-A inhibition by MLN8237 was synergistic with temozolomide and potentiated the effects of ionizing radiation on colony formation in neurosphere glioblastoma tumor stem-like cells. These results further support the potential of Aurora-A inhibitors as primary chemotherapy agents or biologic response modifiers in glioblastoma patients.