Targeting HSP90 dimerization via the C-terminus is effective in imatinib resistant CML and lacks heat shock response.

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Targeting HSP90 dimerization via the C-terminus is effective in imatinib resistant CML and lacks heat shock response.

Blood. 2018 May 03;:

Authors: Bhatia S, Diedrich D, Frieg B, Ahlert H, Stein S, Bopp B, Lang F, Zang T, Kröger T, Ernst T, Kögler G, Krieg A, Lüdeke S, Kunkel H, Rodrigues Moita AJ, Kassack MU, Marquardt V, Opitz FV, Oldenburg M, Remke M, Babor F, Grez M, Hochhaus A, Borkhardt A, Groth G, Nagel-Steger L, Jose J, Kurz T, Gohlke H, Hansen FK, Hauer J

Abstract
Heat shock protein 90 (HSP90) stabilizes many client proteins including BCR-ABL1 oncoprotein. BCR-ABL1 is the hallmark of CML in which treatment-free remission (TFR) is limited with clinical and economic consequences. Thus, there is an urgent need for novel therapeutics, which synergize with current treatment approaches. Several inhibitors targeting the N-terminal domain (NTD) of HSP90 are under investigation; however, side effects such as induction of heat shock response (HSR) and toxicity have so far precluded their FDA approval. We have developed a novel inhibitor (referred to as aminoxyrone) of HSP90 function by targeting HSP90 dimerization via the C-terminal domain (CTD). This was achieved by structure-based molecular design, chemical synthesis, and functional pre-clinical in vitro and in vivo validation using CML cell lines and patient-derived CML cells. Aminoxyrone (AX) is a promising potential candidate, which induces apoptosis in leukemic stem cells (LSCs) fraction (CD34+CD38-) as well as the leukemic bulk (CD34+CD38+) of primary CML and in TKI-resistant cells. Furthermore, BCR-ABL1 oncoprotein and related pro-oncogenic cellular responses are downregulated and targeting HSP90 C-terminus by AX does not induce HSR in vitro and in vivo. We also probed the potential of AX in other therapy refractory leukemia such as BCR-ABL1+ BCP-ALL, FLT3-ITD+ AML and Ph-like BCP-ALL. Therefore, AX is the first peptidometic C-terminal HSP90 inhibitor with the potential to increase TFR in TKI sensitive and refractory CML patients and also offers a novel therapeutic option for patients with other therapy-refractory leukemia, due to its low toxicity profile and lack of HSR.

PMID: 29724897 [PubMed - as supplied by publisher]

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