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The class I HDAC inhibitor Romidepsin targets inflammatory breast cancer tumor emboli and synergizes with paclitaxel to inhibit metastasis
Fredika M. Robertson, Khoi Chu, Kimberly M. Boley, Zaiming Ye, Hui Liu, Moishia C. Wright, Ricardo Moraes, XueJun Zhang, Tessa L. Green, Sanford H. Barsky, Carla Heise and Massimo Cristofanilli

Inflammatory breast cancer (IBC) is the most metastatic variant of locally advanced breast cancer. IBC has distinctive characteristics including invasion of tumor emboli into the skin and rapid disease progression. Given our previous studies suggesting that HDAC inhibitors have promise in targeting IBC, the present study revealed that the class I HDAC inhibitor Romidepsin (FK-288, Istodax®; Celgene Corporation, Summit, NJ) potently induced destruction of IBC tumor emboli and lymphatic vascular architecture. associated with inhibition of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1α, (HIF1α) proteins in the Mary-X pre-clinical model of IBC. Romidepsin treatment induced clinically relevant biomarkers in including induction of acetylated Histone 3 (Ac-H3) proteins, apoptosis, and increased p21WAF1/CIP1. Romidepsin, alone and synergistically when combined with Paclitaxel, effectively eliminated both primary tumors and metastatic lesions at multiple sites formed by the SUM149 IBC cell line. This is the first report of the ability of an HDAC inhibitor to eradicate IBC tumor emboli, to destroy the integrity of lymphatic vessel architecture and to target metastasis. Furthermore, Romidepsin, in combination with a taxane, warrants evaluation as a therapeutic strategy that may effectively target the skin involvement and rapid metastasis that are hallmarks of IBC.

Keywords: inflammatory breast cancer; Mary-X; HDAC inhibitors; Romidepsin; HIF1α, tumor emboli; Paclitaxel

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