title: Protective role of humanin on bortezomib-induced bone growth impairment in anticancer treatment.
abstract: BACKGROUND
  Bortezomib is a proteasome inhibitor currently studied in clinical trials of childhood cancers. So far, no side effects on bone growth have been reported in treated children. However, bortezomib was recently found to induce apoptosis in growth plate chondrocytes and impair linear bone growth in treated mice. We hypothesize that [Gly(14)]-humanin (HNG), a 24-amino acid synthetic antiapoptotic peptide, can prevent bortezomib-induced bone growth impairment.
  
  
  METHODS
  Mice with human neuroblastoma or medulloblastoma tumor xenografts (9-13 animals/group) received one 2-week cycle (2 injections/week) of bortezomib (0.8 mg/kg or 1.0mg/kg), or HNG (1 µg/mouse), or the combination of HNG/bortezomib, or vehicle. Cultures of human growth plate cartilage, chondrogenic- and cancer cell lines, and immunohistochemistry for detection of proapoptotic proteins were also used. Statistical significance was evaluated by two-sided Mann-Whitney U test or by parametric or nonparametric analysis of variance.
  
  
  RESULTS
  Bortezomib efficiently blocked the proteasome and induced pronounced impairment of linear bone growth from day 0 to day 13 (0.09 mm/day, 95% confidence interval [CI] = 0.07 to 0.11 mm/day; vs 0.19 mm/day, 95% CI = 0.15 to 0.23 mm/day in vehicle; P < .001), an effect significantly prevented by the addition of HNG (0.15 mm growth/day, 95% CI = 0.14 to 0.16 mm/day; P < .001 vs bortezomib only; P = 0.03 vs vehicle). Bortezomib was highly toxic when added to cultures of human growth plate cartilage, with markedly increased apoptosis compared with control (P < .001). However, when combining with HNG, bortezomib-induced apoptosis was entirely prevented, as was Bax and PARP activation. Bortezomib delayed tumor growth, and HNG did not interfere with the anticancer effect when studied in human tumor xenografts or cell lines.
  
  
  CONCLUSIONS
  HNG prevents bortezomib-induced bone growth impairment without interfering with bortezomib's desired anticancer effects.
authors.affiliation: Affiliations of authors: Pediatric Endocrinology Unit (EE, LS) and Childhood Cancer Research Unit (MW, LSP, JIJ, SE, PK), Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Eriksson
authors.forename: Malin
authors.initials: M
authors.lastname: Wickström
authors.forename: Lova Segerström
authors.initials: LS
authors.lastname: Perup
authors.forename: John I
authors.initials: JI
authors.lastname: Johnsen
authors.forename: Staffan
authors.initials: S
authors.lastname: Eksborg
authors.forename: Per
authors.initials: P
authors.lastname: Kogner
authors.forename: Lars
authors.initials: L
authors.lastname: Sävendahl
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000009:adverse effects*; D017209:Apoptosis / Q000187:drug effects*; D001846:Bone Development / Q000187:drug effects*; D001897:Boronic Acids / Q000008:administration & dosage / Q000009:adverse effects*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D019902:Chondrocytes / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005269:Femur / Q000187:drug effects; D006132:Growth Plate / Q000187:drug effects; D064593:Heterografts; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008527:Medulloblastoma / Q000188:drug therapy*; D008682:Metatarsal Bones / Q000187:drug effects; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma / Q000188:drug therapy*; D061988:Proteasome Inhibitors / Q000008:administration & dosage / Q000009:adverse effects*; D011719:Pyrazines / Q000008:administration & dosage / Q000009:adverse effects*; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D047908:Intracellular Signaling Peptides and Proteins; D061988:Proteasome Inhibitors; D011719:Pyrazines; C427211:humanin; D000069286:Bortezomib