Cancer cells exhibit increased uptake and utilization of glucose in order to survive and continue their accelerated growth. Glucose uptake into mammalian cells is catalysed by members of the GLUT/SLC2A family of glucose/polyol transporters (Joost et al. 2002). Evidence suggests that facilitative glucose transporters (GLUTs) are implicated in the metabolic alteration of tumours (Burstein et al. 1998). Since the intermediary metabolism of prostate cells has been implicated in the pathogenesis of prostate adenocarcinoma and the progression from benign to malignant, metastatic prostate cancer (Costello & Franklin, 2000), we examined the expression of all the known members of the GLUT/SLC2A family in benign, weakly metastatic and strongly metastatic human prostate cancer cell lines.
Three prostate cell lines were used: an SV40 immortalized cell line derived from normal prostatic epithelial cells (PNT2) and two metastatic cell lines derived from prostatic carcinomas (DU145 and PC3). Cells were grown in RPMI 1640 supplemented with 2 mM L-glutamine, 10 % FCS, 100 µg ml-1 penicillin, 0.1 mg ml-1 streptomycin. Total RNA was isolated from each cell line and single stranded cDNA libraries constructed using Superscript II. Human specific oligonucleotide primers were designed to amplify PCR products corresponding to GLUTs 1-12 (except GLUT7) and the proton-myoinositol symporter HMIT1. β-Actin was also used as a positive control in all PCR experiments. PCR experiments were carried out at least three separate times for all known members of the GLUT/SLC2A family (repeated nine times for GLUT4 and GLUT9) for 35 cycles and the amplification products separated on 1 % agarose gels.
Transcripts of GLUT9 were not detected in the benign PNT2 cell line but were expressed in the metastatic DU145 and PC3 cell lines. GLUT5 was only detected in the PC3 cell line. All other GLUTs were detected in all cell lines examined except for GLUT4 which was detected in PC3 cells in three out of nine PCR experiments. HMIT1 was expressed in all three cell lines.
This study demonstrates, that strongly metastatic prostate cancer cell lines express additional GLUT isoforms not present in their benign counterparts (i.e. GLUT5 and GLUT9). This combination may confer the metastatic cells with a metabolic advantage that may encourage aberrant growth and promote metastasis.
The University of Liverpool Research Development Fund supported this study.