Expression of hypoxia-inducible genes in tumor cells

Abstract

Tumor tissue oxygenation impacts on proliferation of cancer cells and their sensitivity towards radio- and chemotherapy. Under low oxygen, mammalian cells show an adaptive response that leads to the induction of a number of genes with well-defined roles in oxygen supply and energy maintenance, e.g. genes encoding enzymes of the glycolytic pathway. The hypoxia-inducible factor 1 (HIF-1), a transcription factor consisting of the two proteins HIF-1alpha and HIF-1beta, plays a major role in the pleiotropic response observed under low oxygen. We have determined, by Northern analysis, the mRNA levels of HIF-1alpha and of two glycolytic enzymes known to be transcriptionally activated by HIF-1, namely phosphoglycerate kinase 1 (PGK 1) and pyruvate kinase M2 (PKM2), in different hepatoma cell lines and in mouse and human tissues. Hypoxic treatment of various mouse and human hepatoma cell lines led to the expected increase in the amount of PGK1 and PKM2 mRNA, while HIF-1alpha mRNA levels were not significantly elevated. Analysis of mouse liver tumors demonstrated no tumor-specific increases in HIF-1alpha or PGK1 mRNA levels. In five of eight human colorectal cancers investigated, PGK1 and PKM2 mRNA levels were increased in comparison to the corresponding normal tissues, while HIF-1alpha mRNA levels were not significantly changed. The majority of the colorectal cancers demonstrated p53 immunoreactivity, presumably due to mutation of the gene; there was, however, no correlation between the p53 staining pattern and mRNA expression levels of glycolytic enzymes.

The TWIST1 oncogene is a direct target of hypoxia-inducible factor-2α

“…To study the relationship between TWIST1 and hypoxia, we investigated the expression of TWIST1 mRNA in human cell lines after exposure to hypoxia using a TWIST1-specific TaqMan assay. In cervix carcinoma cells (HeLa), prostate cancer cells (PC3) and colon cancer cells (HCT116), TWIST1 expression was induced four-to eightfold after 24 h of hypoxia (Figures 3a-c) concurrent with PGK1 induction, a validated HIF target (Kress et al, 1998). In contrast, we could not detect significant TWIST1 induction in human embryonic kidney cells (HEK293T) (Figure 3d).…”

Aberrant expression of RAB1A in human tongue cancer

“…Tsutsumi et al (1988) isolated and sequenced two overlapping clones covering the entire coding sequence of PKM2. Kress et al (1998) indicated that mRNA level of PKM2 is increased in human colorectal cancers in comparison to the corresponding normal tissues.…”

Faecal tumour M2 pyruvate kinase: a new, sensitive screening tool for colorectal cancer

“…The upregulation of the M2-PK isoenzyme can be caused by mutations in the ras gene and upregulation of HIF-1 (Kress et al, 1998;Mazurek et al, 2001). HIF-1 is stabilised by p53 mutations (Kress et al, 1998;Ravi et al, 2000).…”

“…HIF-1 is stabilised by p53 mutations (Kress et al, 1998;Ravi et al, 2000). Indeed, mutations in the ras oncogene and p53 antioncogene are detectable in 40 -60% of colorectal cancers (Bos, 1989;Kinzler and Vogelstein, 1996;Dong et al, 2001;Rengucci et al, 2001;Nishikawa et al, 2002;Smith et al, 2002).…”

“…The tetramer : dimer ratio of M2-PK can be quantified by gel permeation, isoelectric focusing or by ELISA (Cerwenka et al, 1999;Schulze, 2000;Mazurek et al, 1997Mazurek et al, , 2001Mazurek and Eigenbrodt, 2003). The upregulation of the M2-PK protein is under the control of HIF-1 and ras, which are both consistently altered in gastrointestinal tumours (Kress et al, 1998;Mazurek et al, 2001;Nishikawa et al, 2002;Mazurek and Eigenbrodt, 2003). The tetramer : dimer ratio of M2-PK is under the control of several oncoproteins, such as pp60 vÀsrc kinase, HPV-16 E7 and A-Raf ( Figure 1B) (Eigenbrodt et al, 1998b;Zwerschke et al, 1999;Le Mellay et al, 2002).…”