Enhancement of SPHK1 in vitro by carbon ion irradiation in oral squamous cell carcinoma.
OBJECTIVE
The purpose of this study was to assess the gene expression changes in oral squamous cell carcinoma (OSCC) cells after carbon ion irradiation.


METHODS
Three OSCC cell lines (HSC2, Ca9-22, and HSC3) were irradiated with accelerated carbon ion beams or X-rays using three different doses. The cellular sensitivities were determined by clonogenic survival assay. To identify genes the expression of which is influenced by carbon ion irradiation in a dose-dependent manner, we performed Affymetrix GeneChip analysis with HG-U133 plus 2.0 arrays containing 54,675 probe sets. The identified genes were analyzed using the Ingenuity Pathway Analysis Tool to investigate the functional network and gene ontology. Changes in mRNA expression in the genes were assessed by real-time reverse transcriptase-polymerase chain reaction.


RESULTS
We identified 98 genes with expression levels that were altered significantly at least twofold in each of the three carbon-irradiated OSCC cell lines at all dose points compared with nonirradiated control cells. Among these, SPHK1, the expression of which was significantly upregulated by carbon ion irradiation, was modulated little by X-rays. The function of SPHK1 related to cellular growth and proliferation had the highest p value (p = 9.25e-7 to 2.19e-2). Real-time reverse transcriptase-polymerase chain reaction analysis showed significantly elevated SPHK1 expression levels after carbon ion irradiation (p < 0.05), consistent with microarray data. Clonogenic survival assay indicated that carbon ion irradiation could induce cell death in Ca9-22 cells more effectively than X-rays.


CONCLUSIONS
Our findings suggest that SPHK1 helps to elucidate the molecular mechanisms and processes underlying the biologic response to carbon ion beams in OSCC.
Higo
Morihiro
M
Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Uzawa
Katsuhiro
K
Kawata
Tetsuya
T
Kato
Yoshikuni
Y
Kouzu
Yukinao
Y
Yamamoto
Nobuharu
N
Shibahara
Takahiko
T
Mizoe
Jun-Etsu
JE
Ito
Hisao
H
Tsujii
Hirohiko
H
Tanzawa
Hideki
H
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism / Q000528:radiation effects*; D002244:Carbon / Q000627:therapeutic use*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000532:radiotherapy; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects; D015870:Gene Expression / Q000528:radiation effects; D020869:Gene Expression Profiling / Q000379:methods; D063193:Heavy Ion Radiotherapy; D006801:Humans; D018499:Linear Energy Transfer; D046228:Microarray Analysis / Q000379:methods*; D009062:Mouth Neoplasms / Q000235:genetics / Q000532:radiotherapy; D009693:Nucleic Acid Hybridization / Q000379:methods; D012334:RNA, Neoplasm / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; D012334:RNA, Neoplasm; C466999:SPHKAP protein, human; D002244:Carbon