American Association for Cancer Research
00085472can130013-sup-107140_1_supp_1960195_mm58b1.ppt (154.5 kB)

Figure S4 from Hbo1 Is a Cyclin E/CDK2 Substrate That Enriches Breast Cancer Stem-like Cells

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posted on 2023-03-30, 21:42 authored by MyLinh T. Duong, Said Akli, Sira Macalou, Anna Biernacka, Bisrat G. Debeb, Min Yi, Kelly K. Hunt, Khandan Keyomarsi

Figure S4: Cyclin E/CDK2 phosphorylation of Hbo1 does not affect the HAT activity of Hbo1.



Expression of cyclin E proteolytic cleavage products, low-molecular weight cyclin E (LMW-E), is associated with poor clinical outcome in patients with breast cancer and it enhances tumorigenecity in mouse models. Here we report that LMW-E expression in human mammary epithelial cells induces an epithelial-to-mesenchymal transition phenotype, increases the CD44hi/CD24lo population, enhances mammosphere formation, and upregulates aldehyde dehydrogenase expression and activity. We also report that breast tumors expressing LMW-E have a higher proportion of CD44hi/CD24lo tumor cells as compared with tumors expressing only full-length cyclin E. In order to explore how LMW-E enriches cancer stem cells in breast tumors, we conducted a protein microarray analysis that identified the histone acetyltransferase (HAT) Hbo1 as a novel cyclin E/CDK2 substrate. The LMW-E/CDK2 complex phosphorylated Hbo1 at T88 without affecting its HAT activity. When coexpressed with LMW-E/CDK2, wild-type Hbo1 promoted enrichment of cancer stem-like cells (CSC), whereas the T88 Hbo1 mutant reversed the CSC phenotype. Finally, doxorubicin and salinomycin (a CSC-selective cytotoxic agent) synergized to kill cells expressing LMW-E, but not full-length cyclin E. Collectively, our results suggest that the heightened oncogenecity of LMW-E relates to its ability to promote CSC properties, supporting the design of therapeutic strategies to target this unique function. Cancer Res; 73(17); 5556–68. ©2013 AACR.