title: DNA fragmentation and caspase-independent programmed cell death by modulated electrohyperthermia.
abstract: OBJECTIVE
  The electric field and the concomitant heat (electrohyperthermia) can synergistically induce cell death in tumor tissue, due to elevated glycolysis, ion concentration, and permittivity in malignant compared with nonmalignant tissues. Here we studied the mechanism and time course of tumor destruction caused by electrohyperthermia.
  
  
  METHODS
  Bilateral implants of HT29 colorectal cancer in the femoral regions of Balb/c (nu/nu) mice were treated with a single 30-min shot of modulated, 13.56-MHz, radiofrequency-generated electrohyperthermia (mEHT). Tumors at 0, 1, 4, 8, 14, 24, 48, and 72 h posttreatment were studied for morphology, DNA fragmentation, and cell death response-related protein expression using tissue microarrays, immunohistochemistry, Western immunoblots, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays.
  
  
  RESULTS
  Modulated EHT treatment induced significant tumor destruction in HT29 xenografts with a peak of a sevenfold increase compared with the untreated controls. The significant treatment-related elevation of DNA fragmentation--detected with TUNEL assay--and apoptotic bodies between 24 and 72 h posttreatment was proof of a programmed cell death response. This was associated with significant mitochondrial accumulation of bax and mitochondrial-to-cytoplasmic release of cytochrome c proteins between 8 and 14 h. Cleaved caspase-3 levels were low and mainly localized to inflammatory cells. The substantial cytoplasmic-to-nuclear translocation of apoptosis-inducing factor (AIF) and its 57-kDa activated fragment detected between 14 and 24 h after treatment indicated AIF as an effector for DNA fragmentation.
  
  
  CONCLUSIONS
  Modulated EHT treatment can induce programmed cell death-related tumor destruction in HT29 colorectal adenocarcinoma xenografts, which dominantly follows a caspase-independent subroutine.
authors.affiliation: 1st Department of Pathology and Experimental Cancer Research MTA-SE Tumor Progression Research Group, Semmelweis University, Ulloi ut 26, 1085, Budapest, Hungary.
authors.forename: N
authors.initials: N
authors.lastname: Meggyeshazi
authors.forename: G
authors.initials: G
authors.lastname: Andocs
authors.forename: L
authors.initials: L
authors.lastname: Balogh
authors.forename: P
authors.initials: P
authors.lastname: Balla
authors.forename: G
authors.initials: G
authors.lastname: Kiszner
authors.forename: I
authors.initials: I
authors.lastname: Teleki
authors.forename: A
authors.initials: A
authors.lastname: Jeney
authors.forename: T
authors.initials: T
authors.lastname: Krenacs
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology*; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects*; D053143:Caspase 2 / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000473:pathology*; D045304:Cytochromes c / Q000235:genetics; D053938:DNA Fragmentation / Q000528:radiation effects*; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D019073:HT29 Cells; D064593:Heterografts; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D020287:In Situ Nick-End Labeling; D055909:Magnetic Field Therapy / Q000295:instrumentation*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008928:Mitochondria / Q000528:radiation effects; D009368:Neoplasm Transplantation; D051381:Rats; D051028:bcl-2-Associated X Protein / Q000235:genetics
chemical_list: C494827:Bax protein, mouse; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D053143:Caspase 2