title: Effect of temozolomide on the viability of musculoskeletal sarcoma cells.
abstract: Musculoskeletal sarcomas (MSS) are a heterogeneous group of malignancies with relatively high mortality rates. The prognosis for patients with MSS is poor, with few drugs inducing measurable activity. Alkylating agents, namely ifosfamide and dacarbazine, which act nonspecifically on proliferating cells, are the typical therapy prescribed for advanced MSS. A novel alkylating agent, temozolomide (TMZ), has several advantages over existing alkylating agents. TMZ induces the formation of O6-methylguanine in DNA, thereby inducing mismatches during DNA replication and the subsequent activation of apoptotic pathways. However, due to conflicting data in the literature, the mechanism of TMZ action has remained elusive. Therefore, the present study aimed to evaluate apoptosis in MSS cells treated with TMZ, and to evaluate the correlation between TMZ action and survival pathways, including the phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK)1/2 mitogen activated protein kinase (MAPK) pathways. Cell proliferation was evaluated by performing an XTT (sodium 3'-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis (4-methoxy-6-nitro) benzene sulfonic acid hydrate) assay. Apoptotic morphological changes, for example chromatin condensation, were evaluated by fluorescence confocal microscopy. The expression of the apoptosis-associated proteins caspase-3, poly adenosine diphosphate ribose polymerase (PARP), Akt and ERK1/2, was determined by western blotting. The results of the present study indicated that, in certain MSS cells, the IC50value was lower than that in TMZ-sensitive U-87 MG cells. Furthermore, TMZ treatment was associated with apoptotic morphological changes and the expression levels of pro-apoptotic cleaved caspase-3 and PARP were also increased in TMZ-treated MSS cells. In addition, the results indicated that PI3K/Akt and ERK1/2 MAPK were constitutively phosphorylated in MSS cells, and phosphorylation of PI3K/Akt was suppressed in certain cells, and maintained in other cells, by TMZ. These observations emphasized the plasticity of MSS cells, and suggested that this plasticity may contribute to the variance in cell sensitivity to TMZ and TMZ-resistance in MSS.
authors.affiliation: School of Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata 851-8510, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Kusabe
authors.affiliation: Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata 851-8510, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kawashima
authors.affiliation: Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata 851-8510, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ogose
authors.affiliation: Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata 851-8510, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Department of Orthopedic Surgery, Niigata Cancer Center Hospital, Niigata 951-8566, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ariizumi
authors.affiliation: Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata 851-8510, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hotta
authors.affiliation: Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata 851-8510, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Endo
keywords: apoptosis; musculoskeletal sarcoma; phosphoinositide 3-kinase/Akt; temozolomide