title: Shikonin, dually functions as a proteasome inhibitor and a necroptosis inducer in multiple myeloma cells.
abstract: Shikonin (SHK), a natural small agent (MW 288.3), reportedly induces cell death in various tumor cells. We have found that SHK also exerts potent cytocidal effects on human multiple myeloma (MM) cells, but its anticancer mechanism in MM cells remains to be elucidated. SHK at 2.5-5 µM induced apoptosis in seven MM cell lines, including the bortezomib-resistant cell line KMS11/BTZ. The IC50 value of SHK against KMS11/BTZ was comparable to that of a parental cell line KMS11 (1.1 and 1.56 µM, respectively). SHK induces accumulation of ubiquitinated proteins and activates XBP-1 in MM cells, suggesting that SHK functions as a proteasome inhibitor, eventually inducing ER stress-associated apoptosis. SHK increases levels of HSP70/72, which protects cells from apoptosis, and exerts greater cytocidal effects in combination with the HSP70/72 inhibitor VER-155008. At higher concentrations (10-20 µM), SHK induced cell death, which was completely inhibited by a necroptosis inhibitor, necrostatin-1 (Nec-1), while the cytocidal activity was unaffected by Z-VAD-FMK, strongly suggesting that cell death is induced by SHK at high concentrations through necroptosis. The present data show for the first time that SHK induces cell death in MM cells. SHK efficiently induces apoptosis and combination of heat shock protein inhibitor with low dose SHK enhances apoptosis, while high dose SHK induces necroptosis in MM cells. These findings together support the use of SHK as a potential therapeutic agent for MM.
authors.affiliation: Department of Hematology, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Wada
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.
authors.forename: Yawara
authors.initials: Y
authors.lastname: Kawano
authors.affiliation: Department of Hematology, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Shiho
authors.initials: S
authors.lastname: Fujiwara
authors.affiliation: Department of Hematology, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kikukawa
authors.affiliation: Department of Hematology, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Okuno
authors.affiliation: Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Tasaki
authors.affiliation: Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Mitsuharu
authors.initials: M
authors.lastname: Ueda
authors.affiliation: Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ando
authors.affiliation: Department of Anatomy, Graduate School of Health Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yoshinaga
authors.affiliation: Department of Hematology and Oncology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Ri
authors.affiliation: Department of Hematology and Oncology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Iida
authors.affiliation: Research Functions Unit, Kyowa Hakko Kirin Co., Ltd., Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakashima
authors.affiliation: Translational Oncology, Kyowa Hakko Kirin California Inc., La Jolla, CA, USA.
authors.forename: Yukimasa
authors.initials: Y
authors.lastname: Shiotsu
authors.affiliation: Department of Hematology, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Mitsuya
authors.affiliation: Department of Hematology, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hata
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000473:pathology*; D009285:Naphthoquinones / Q000008:administration & dosage / Q000494:pharmacology*; D009336:Necrosis / Q000473:pathology; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D011684:Purine Nucleosides / Q000494:pharmacology; D011719:Pyrazines / Q000494:pharmacology; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000235:genetics; D000071717:X-Box Binding Protein 1
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D004268:DNA-Binding Proteins; D007093:Imidazoles; D007211:Indoles; D009285:Naphthoquinones; D061988:Proteasome Inhibitors; D011684:Purine Nucleosides; D011719:Pyrazines; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; C550733:VER 155008; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C507699:necrostatin-1; C016101:shikonin; D000069286:Bortezomib