title: The phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor NVP-BEZ235 is effective in inhibiting regrowth of tumour cells after cytotoxic therapy.
abstract: OBJECTIVE
  Regrowth of tumour cells between cycles of chemotherapy is a significant clinical problem. Treatment strategies where antiproliferative agents are used to inhibit tumour regrowth between chemotherapy cycles are attractive, but such strategies are difficult to test using conventional monolayer culture systems.
  
  
  METHODS
  We used the in vitro tumour spheroid model to study regrowth of 3-D colon carcinoma tissue after cytotoxic therapy. Colon carcinoma cells with wild-type or mutant phosphatidyl inositol 3-kinase catalytic subunit (PI3KCA) or KRAS alleles were allowed to form multicellular spheroids and the effects of different pharmacological compounds were studied after sectioning and staining for relevant markers of cell proliferation and apoptosis.
  
  
  RESULTS
  Studies using colon cancer cells with gene disruptions suggested that the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway was essential for proliferation in 3-D culture. The dual PI3K-mTOR inhibitor NVP-BEZ235, currently in clinical trials, was found to inhibit phosphorylation of the mTOR target 4EBP1 in 3-D cultured cells. The ability of NVP-BEZ235 to inhibit tumour cell proliferation and to induce apoptosis was markedly more pronounced in 3-D cultures compared to monolayer cultures. It was subsequently found that NVP-BEZ235 was effective in inhibiting regrowth of 3-D cultured cells after treatment with two cytotoxic inhibitors of the ubiquitin-proteasome system (UPS), methyl-13-hydroxy-15-oxokaurenoate (MHOK) and bortezomib (Velcade®).
  
  
  CONCLUSIONS
  The dual PI3K-mTOR inhibitor NVP-BEZ235 was found to reduce cell proliferation and to induce apoptosis in 3-D cultured colon carcinoma cells, NVP-BEZ235 is a promising candidate for use in sequential treatment modalities together with cytotoxic drugs to reduce the cell mass of solid tumours.
authors.affiliation: Department of Oncology & Pathology, Karolinska Institute, 171 76 Stockholm, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Hernlund
authors.forename: Maria Hägg
authors.initials: MH
authors.lastname: Olofsson
authors.forename: Walid
authors.initials: W
authors.lastname: Fayad
authors.forename: Mårten
authors.initials: M
authors.lastname: Fryknäs
authors.forename: Karolina
authors.initials: K
authors.lastname: Lesiak-Mieczkowska
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Zhang
authors.forename: Slavica
authors.initials: S
authors.lastname: Brnjic
authors.forename: Vivien
authors.initials: V
authors.lastname: Schmidt
authors.forename: Padraig
authors.initials: P
authors.lastname: D'Arcy
authors.forename: Tobias
authors.initials: T
authors.lastname: Sjöblom
authors.forename: Angelo
authors.initials: A
authors.lastname: De Milito
authors.forename: Rolf
authors.initials: R
authors.lastname: Larsson
authors.forename: Stig
authors.initials: S
authors.lastname: Linder
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007150:Immunohistochemistry; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011804:Quinolines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011804:Quinolines; C531198:dactolisib