title: Exposure to carbon dioxide and helium reduces in vitro proliferation of pediatric tumor cells.
abstract: BACKGROUND
  Minimally invasive techniques are increasingly applied to children with malignant tumors. We showed previously that CO(2) used for pneumoperitoneum modulates the function of macrophages and polymorphonuclear cells via direct effects and via acidification. Numerous in vitro and small animal model studies also confirmed an alteration of the behavior of several types of adult tumor cells by CO(2). The impact of CO(2) and other gases used for pneumoperitoneum on the behavior of various pediatric tumors has not yet been determined.
  
  
  METHODS
  Cell lines of neuroblastoma (IMR 32, SK-N-SH, Sy5y), lymphoma (Daudi), hepatoblastoma (Huh 6), hepatocellular carcinoma (Hep G2), and rhabdomyosarcoma (Te 671) were incubated for 2 h. Incubation was performed with 100% CO(2), 100% helium, and 5% CO(2) as control. Cell proliferation was determined by the MTT-assay [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] by actively growing cells to produce a blue formazan product. The MTT-assay was performed before, directly after incubation, and daily for 4 days. Vitality of the cells was determined by trypan blue. The extracellular pH during incubation was measured during gas exposition every 10 min using Bayer Rapid Lab 855.
  
  
  RESULTS
  CO(2) for 2 h significantly decreased the proliferation of neuroblastoma, lymphoma, hepatoblastoma, and hepatocellular carcinoma cells. This decrease persisted over 4 days in neuroblastoma, lymphoma, and hepatocellular carcinoma cells. The CO(2) had no impact on hepatoblastoma and rhabdomyosarcoma cells. Helium had a similar effect on neuroblastoma cells. After 4 days, a significant decrease of cell activity was found in two neuroblastoma cell lines and in hepatoblastoma cells. Helium had no effect on lymphoma and hepatocellular carcinoma cells. The extracellular pH was 6.2 during incubation with CO(2), and 7.6 during incubation with helium.
  
  
  CONCLUSIONS
  CO(2) and helium may affect the proliferation of some pediatric tumor cell lines in vitro. However, some of these effects and the impact on the extracellular pH are differential. The role of pH modulation, hypoxia and direct effects of gases remain to be investigated before a general recommendation on the use of minimally invasive techniques in pediatric oncology can be given.
authors.affiliation: Department of Pediatric Surgery, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Annika I
authors.initials: AI
authors.lastname: Schmidt
authors.forename: Marc
authors.initials: M
authors.lastname: Reismann
authors.forename: Joachim F
authors.initials: JF
authors.lastname: Kübler
authors.forename: Gertrud
authors.initials: G
authors.lastname: Vieten
authors.forename: Cathérine
authors.initials: C
authors.lastname: Bangen
authors.forename: Akihiro
authors.initials: A
authors.lastname: Shimotakahara
authors.forename: Sylvia
authors.initials: S
authors.lastname: Glüer
authors.forename: Rainer
authors.initials: R
authors.lastname: Nustede
authors.forename: Benno M
authors.initials: BM
authors.lastname: Ure
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D045744:Cell Line, Tumor / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D002648:Child; D006371:Helium / Q000494:pharmacology*; D018197:Hepatoblastoma / Q000473:pathology; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D008223:Lymphoma / Q000473:pathology; D019060:Minimally Invasive Surgical Procedures; D009369:Neoplasms / Q000473:pathology* / Q000601:surgery*; D009447:Neuroblastoma / Q000473:pathology; D011028:Pneumoperitoneum, Artificial; D012208:Rhabdomyosarcoma / Q000473:pathology; D018709:Statistics, Nonparametric
chemical_list: D002245:Carbon Dioxide; D006371:Helium