Identification of heat shock protein 32 (Hsp32) as a novel survival factor

Department of Internal Medicine I, Division of Hematology & Hemostaseology, Graduate School of Medical Sciences, Kumamoto University, Japan.
Blood (Impact Factor: 10.45). 08/2007; 110(2):661-9. DOI: 10.1182/blood-2006-10-054411
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Systemic mastocytosis (SM) is a myeloid neoplasm characterized by increased survival and accumulation of neoplastic mast cells (MCs). In most patients, the D816V-mutated variant of KIT is detectable. We report here that heat shock protein 32 (Hsp32), also known as heme oxygenase-1 (HO-1), is a novel KIT-inducible survival factor in neoplastic MCs. As assessed by reverse transcription-polymerase chain reaction (RT-PCR), immunocytochemistry, and Western blotting, the KIT D816V(+) MC line HMC-1.2 as well as highly enriched primary neoplastic MCs were found to express Hsp32 mRNA and the Hsp32 protein. Moreover, KIT D816V and stem cell factor (SCF)-activated wild-type KIT were found to induce Hsp32 promoter activity, expression of Hsp32 mRNA, and expression of the Hsp32 protein in Ba/F3 cells. Correspondingly, the KIT D816V-targeting drug PKC412 decreased the expression of Hsp32 as well as proliferation/survival in neoplastic MCs. The inhibitory effects of PKC412 on the survival of HMC-1.2 cells were counteracted by the HO-1 inductor hemin or lentiviral-transduced HO-1. Moreover, 2 Hsp32-targeting drugs, pegylated zinc protoporphyrin (PEG-ZnPP) and styrene maleic acid copolymer micelle-encapsulated ZnPP (SMA-ZnPP), were found to inhibit proliferation and to induce apoptosis in neoplastic MCs. Furthermore, both drugs were found to cooperate with PKC412 in producing growth inhibition. Together, these data show that Hsp32 is an important survival factor and interesting new therapeutic target in neoplastic MCs.

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Available from: Anja Vales, Feb 09, 2015
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    • "This contrasts with a previous study using immunohistochemistry which indicated that hsp32 was up-regulated in prostate cancer tissue (Maines and Abrahamsson 1996). However, because it was observed to be widely expressed it could act as a pro-survival protein, as it may in mastocytosis (Kondo et al. 2007). Up-regulation of hsp32 expression has been shown to result in increased proliferation of melanoma cell lines and, compared with wild type cell lines, to significantly reduce survival time in mice (Was et al. 2006). "
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