Therapeutic response to CDK4/6 inhibition in breast cancer defined by ex vivo analyses of human tumors

Jeffry L. Dean, A. Kathleen McClendon, Theresa E. Hickey, Lisa M. Butler, Wayne D. Tilley, Agnieszka K. Witkiewicz, Erik S. Knudsen

Research output: Contribution to journalArticle

131 Scopus citations

Abstract

To model the heterogeneity of breast cancer as observed in the clinic, we employed an ex vivo model of breast tumor tissue. This methodology maintained the histological integrity of the tumor tissue in unselected breast cancers, and importantly, the explants retained key molecular markers that are currently used to guide breast cancer treatment (e.g., ER and Her2 status). The primary tumors displayed the expected wide range of positivity for the proliferation marker Ki67, and a strong positive correlation between the Ki67 indices of the primary and corresponding explanted tumor tissues was observed. Collectively, these findings indicate that multiple facets of tumor pathophysiology are recapitulated in this ex vivo model. To interrogate the potential of this preclinical model to inform determinants of therapeutic response, we investigated the cytostatic response to the CDK4/6 inhibitor, PD-0332991. This inhibitor was highly effective at suppressing proliferation in approximately 85% of cases, irrespective of ER or HER2 status. However, 15% of cases were completely resistant to PD-0332991. Marker analyses in both the primary tumor tissue and the corresponding explant revealed that cases resistant to CDK4/6 inhibition lacked the RB-tumor suppressor. These studies provide important insights into the spectrum of breast tumors that could be treated with CDK4/6 inhibitors, and defines functional determinants of response analogous to those identified through neoadjuvant studies.

Original languageEnglish (US)
Pages (from-to)2756-2761
Number of pages6
JournalCell Cycle
Volume11
Issue number14
DOIs
StatePublished - Jul 15 2012

Keywords

  • Breast cancer
  • Cell cycle
  • ER
  • Ex vivo
  • PD0332991

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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  • Cite this

    Dean, J. L., McClendon, A. K., Hickey, T. E., Butler, L. M., Tilley, W. D., Witkiewicz, A. K., & Knudsen, E. S. (2012). Therapeutic response to CDK4/6 inhibition in breast cancer defined by ex vivo analyses of human tumors. Cell Cycle, 11(14), 2756-2761. https://doi.org/10.4161/cc.21195