GLUT1 gene is a potential hypoxic marker in colorectal cancer patients.
BACKGROUND
Tumor hypoxia is an important factor related to tumor resistance to radiotherapy and chemotherapy. This study investigated molecules synthesized in colorectal cancer cells during hypoxia to explore the possibility of developing molecular probes capable of detecting cell death and/or the efficiency of radiotherapy and chemotherapy.


METHODS
At first, we incubated two human colorectal adenocarcinoma cell lines SW480 (UICC stage II) and SW620 (UICC stage III) cells in hypoxic (< or =2% O2, 93% N2, and 5% CO2) and normoxic conditions (20% O2, 75% N2, and 5% CO2) for 24 h and 48 h. The relative expression ratio of GLUT1 mRNA in hypoxic conditions was analyzed by RT-PCR. Ten cancerous tissues collected from human colorectal cancer patients were examined. HIF-1alpha and HIF-2alpha levels were measured to indicate the degree of hypoxia, and gene expression under hypoxic conditions was determined. As a comparison, HIF-1alpha, HIF-2alpha, and GLUT1 levels were measured in the peripheral blood of 100 CRC patients.


RESULTS
Hypoxia-induced lactate was found to be elevated 3.24- to 3.36-fold in SW480 cells, and 3.06- to 3.17-fold in SW620 cells. The increased relative expression ratio of GLUT1 mRNA, under hypoxic conditions was higher in SW620 cells (1.39- to 1.72-fold elevation) than in SW480 cells (1.24- to 1.66-fold elevation). HIF-1alpha and HIF-2alpha levels were elevated and GLUT1 genes were significantly overexpressed in CRC tissue specimens. The elevated ratio of GLUT1 was higher in stage III and IV CRC tissue specimens than in the stage I and II (2.97-4.73 versus 1.44-2.11). GLUT1 mRNA was also increased in the peripheral blood of stage II and III CRC patients as compared to stage I patients, suggesting that GLUT1 may serve as a hypoxic indicator in CRC patients.


CONCLUSIONS
In conclusion, this study demonstrated that GLUT1 has the potential to be employed as a molecular marker to indicate the degree of hypoxia experienced by tumors circulating in the blood of cancer patients.
Chung
Fu-Yen
FY
Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan, Republic of China. fuyenchung@gmail.com
Huang
Ming-Yii
MY
Yeh
Ching-Sheng
CS
Chang
Hui-Jen
HJ
Cheng
Tian-Lu
TL
Yen
Li-Chen
LC
Wang
Jaw-Yuan
JY
Lin
Shiu-Ru
SR
D000328:Adult; D000368:Aged; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D051272:Glucose Transporter Type 1 / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008875:Middle Aged; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors
C497396:ARNT protein, human; D014408:Biomarkers, Tumor; D051272:Glucose Transporter Type 1; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator