mTOR Signal and Hypoxia-Inducible Factor-1α Regulate CD133 Expression in Cancer Cells

Abstract

The underlying mechanism regulating the expression of the cancer stem cell/tumor-initiating cell marker CD133/prominin-1 in cancer cells remains largely unclear, although knowledge of this mechanism would likely provide important biological information regarding cancer stem cells. Here, we found that the inhibition of mTOR signaling up-regulated CD133 expression at both the mRNA and protein levels in a CD133-overexpressing cancer cell line. This effect was canceled by a rapamycin-competitor, tacrolimus, and was not modified by conventional cytotoxic drugs. We hypothesized that hypoxia-inducible factor-1A (HIF-1A), a downstream molecule in the mTOR signaling pathway, might regulate CD133 expression; we therefore investigated the relation between CD133 and HIF-1A. Hypoxic conditions up-regulated HIF-1A expression and inversely down-regulated CD133 expression at both the mRNA and protein levels. Similarly, the HIF-1A activator deferoxamine mesylate dose-dependently down-regulated CD133 expression, consistent with the effects of hypoxic conditions. Finally, the correlations between CD133 and the expressions of HIF-1A and HIF-1B were examined using clinical gastric cancer samples. A strong inverse correlation (r = À0.68) was observed between CD133 and HIF-1A, but not between CD133 and HIF-1B. In conclusion, these results indicate that HIF-1A down-regulates CD133 expression and suggest that mTOR signaling is involved in the expression of CD133 in cancer cells. Our findings provide a novel insight into the regulatory mechanisms of CD133 expression via mTOR signaling and HIF-1A in cancer cells and might lead to insights into the involvement of the mTOR signal and oxygen-sensitive intracellular pathways in the maintenance of stemness in cancer stem cells. [Cancer Res 2009;69(18):7160-4]

FGF3/FGF4 amplification and multiple lung metastases in responders to sorafenib in hepatocellular carcinoma

“…Real-time reverse-transcription PCR (RT-PCR) was performed as described. 11 In brief, complementary DNA was prepared from the total RNA obtained from each surgical frozen section using a GeneAmp RNA-PCR kit (Applied Biosystems). Real-time RT-PCR amplification was performed using a Thermal Cycler Dice (TaKaRa, Otsu, Japan) in accordance with the manufacturer's instructions under the following conditions: 95 C for 5 minutes, followed by 50 cycles of 95 C for 10 seconds and 60 C for 30 seconds.…”

“…Western blot analysis was performed as described. 11 The following antibodies were used: monoclonal FGF3 (R&D Systems, Minneapolis, MN), FGF4 and FGFR2 antibodies (Santa Cruz Biotechnology, Santa Cruz, CA), and phosphorylated FGFR and horseradish peroxidase-conjugated secondary antibodies (Cell Signaling Technology, Beverly, MA). NIH-3T3 cells were exposed to the indicated concentrations of sorafenib for 2 hours and were then stimulated with FGF4-conditioned medium for 20 minutes.…”

Expression changes in arrestin β 1 and genetic variation in catechol-O-methyltransferase are biomarkers for the response to morphine treatment in cancer patients

“…The methods used in this section have been previously described (12). GAPD was used to normalize the expression levels in the subsequent quantitative analyses.…”

Identification of Novel HIF1A Target Genes That Regulate Tumor Progression and Metastasis

“…We found 94 genes differentially regulated by HIF-1α in both settings (Chapter 5). Many of these genes, including Vegf, Egln3 (PHD3), Aldoc and Pdk1 were known HIF-1α target genes and are involved in cancer cell migration and invasion, tumor initiation and growth, and metastasis [61,154] [ 72,116]. One of the genes we found to be the most differentially up-regulated in WT cells and tumors is the enzyme creatine kinase brain isoform (Ckb).…”

“…Interestingly, in gliomas, the TIC population was enriched via cell sorting based on the expression of a single cell surface marker, CD133 (PROM1). PROM1, a transmembrane protein without a known ligand, is a known hypoxia-responsive protein regulated by HIF-1 [116,117]. Several studies have shown that the population of breast tumor cells with the ability to self-renew is enriched with the ability to initiate tumorigenesis in vivo [118][119][120][121].…”