(A) Quantification of MTB/TAN primary tumor cell lines expressing pk1, Cerk or G198D- Cerk withdrawn from doxycycline 72 hr then stained for Ki67. (B) Quantification of MTB/TAN primary tumor cell lines expressing MLP, a control scrambled shRNA, shCerk1 or shCerk2 withdrawn from doxycycline 72 hr then stained for Ki67. (C) Western blot of MTB/TAN primary tumor cell lines expressing empty vector, a control scrambled shRNA, or shCerk1 withdrawn from doxycycline 48 hr, blotted for cleaved PARP, quantified in (D), and cleaved caspase-3, quantified in (E).
ARTICLE ABSTRACT
Recurrent breast cancer is typically an incurable disease and, as such, is disproportionately responsible for deaths from this disease. Recurrent breast cancers arise from the pool of disseminated tumor cells (DTC) that survive adjuvant or neoadjuvant therapy, and patients with detectable DTCs following therapy are at substantially increased risk for recurrence. Consequently, the identification of pathways that contribute to the survival of breast cancer cells following therapy could aid in the development of more effective therapies that decrease the burden of residual disease and thereby reduce the risk of breast cancer recurrence. We now report that ceramide kinase (Cerk) is required for mammary tumor recurrence following HER2/neu pathway inhibition and is spontaneously upregulated during tumor recurrence in multiple genetically engineered mouse models for breast cancer. We find that Cerk is rapidly upregulated in tumor cells following HER2/neu downregulation or treatment with Adriamycin and that Cerk is required for tumor cell survival following HER2/neu downregulation. Consistent with our observations in mouse models, analysis of gene expression profiles from more than 2,200 patients revealed that elevated CERK expression is associated with an increased risk of recurrence in women with breast cancer. In addition, although CERK expression is associated with aggressive subtypes of breast cancer, including those that are estrogen receptor–negative, HER2+, basal-like, or high grade, its association with poor clinical outcome is independent of these clinicopathologic variables. Together, our findings identify a functional role for Cerk in breast cancer recurrence and suggest the clinical utility of agents targeted against this prosurvival pathway. Cancer Res; 74(21); 6352–63. ©2014 AACR.
