Targeting the HOX/PBX dimer in breast cancer
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The HOX genes are a family of closely related transcription factors that help to define the identity of cells and tissues during embryonic development and which are also frequently deregulated in a number of malignancies, including breast cancer. While relatively little is known about the roles that individual HOX genes play in cancer, it is however clear that these roles can be both contradictory, with some members acting as oncogenes and some as tumor suppressors, and also redundant, with several genes essentially having the same function. Here, we have attempted to address this complexity using the HXR9 peptide to target the interaction between HOX proteins and PBX, a second transcription factor that serves as a common co-factor for many HOX proteins. We show that HXR9 causes apoptosis in a number of breast cancer-derived cell lines and that sensitivity to HXR9 is directly related to the averaged expression of HOX genes HOXB1 through to HOXB9, providing a potential biomarker to predict the sensitivity of breast tumors to HXR9 or its derivatives. Measuring the expression of HOX genes HOXB1–HOXB9 in primary tumors revealed that a subset of tumors show highly elevated expression indicating that these might be potentially very sensitive to killing by HXR9. Furthermore, we show that while HXR9 blocks the oncogenic activity of HOX genes, it does not affect the known tumor-suppressor properties of a subset of HOX genes in breast cancer.
KeywordsBreast cancer SKBR3 MCF7 HXR9 HOX PBX
The authors would like to thank the Guy’s and St Thomas’ (GST) Breast Tissue and Data Bank, London, UK for providing the patient samples used in this study, and the patients who agreed to contribute to this data bank. The study was in part supported by a grant from the Breast Cancer Campaign to RM. The experiments carried out comply with the laws of the United Kingdom.
Conflict of interest
All authors declare no conflict of interest.