title: Inhibition of heat shock protein 90 sensitizes melanoma cells to thermosensitive ferromagnetic particle-mediated hyperthermia with low Curie temperature.
abstract: Heat shock protein (Hsp) 90 is a key regulator of a variety of oncogene products and cell-signaling molecules, and the therapeutic benefit of its inhibition in combination with radiation or chemotherapy has been investigated. In addition, hyperthermia has been used for many years to treat various malignant tumors. We previously described a system in which hyperthermia was induced using thermosensitive ferromagnetic particles (FMP) with a Curie temperature (Tc = 43 degrees C) low enough to mediate automatic temperature control, and demonstrated its antitumor effect in a mouse melanoma model. In the present study, we examined the antitumor effects of combining a Hsp90 inhibitor (geldanamycin; GA) with FMP-mediated hyperthermia. In cultured B16 melanoma cells, GA exerted an antitumor effect by increasing the cells' susceptibility to hyperthermia and reducing expression of Akt. In an in vivo study, melanoma cells were subcutaneously injected into the backs of C57BL/6 mice. FMP were then injected into the resultant tumors, and the mice were divided into four groups: group I, no treatment (control); group II, one hyperthermia treatment; group III, GA alone; and group IV, GA with hyperthermia. When exposed to a magnetic field, the temperature of tissues containing FMP increased and stabilized at the Tc. In group IV, complete regression of tumors was observed in five of nine mice (56%), whereas no tumor regression was seen in groups I-III. Our findings suggest that inhibition of Hsp90 with hyperthermia increases its antitumor effect. Thus, the combination of FMP-mediated, self-regulating hyperthermia with Hsp90 inhibition has important implications for the treatment of cancer.
authors.affiliation: Department of Surgery, Akita University, Hondo, Akita City, Japan.
authors.forename: Aki
authors.initials: A
authors.lastname: Ito
authors.forename: Hajime
authors.initials: H
authors.lastname: Saito
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mitobe
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Minamiya
authors.forename: Naoko
authors.initials: N
authors.lastname: Takahashi
authors.forename: Kiyotomi
authors.initials: K
authors.lastname: Maruyama
authors.forename: Satoru
authors.initials: S
authors.lastname: Motoyama
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Katayose
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage; D016227:Benzoquinones / Q000008:administration & dosage; D015153:Blotting, Western; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D005260:Female; D005290:Ferric Compounds / Q000627:therapeutic use*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006979:Hyperthermia, Induced / Q000379:methods*; D020287:In Situ Nick-End Labeling; D047029:Lactams, Macrocyclic / Q000008:administration & dosage; D008546:Melanoma, Experimental / Q000378:metabolism / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012878:Skin Neoplasms / Q000628:therapy*
chemical_list: D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; D005290:Ferric Compounds; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; C001215:ferrite; D051057:Proto-Oncogene Proteins c-akt; C001277:geldanamycin