Increased expression of HIF-1A and its implication in the hypoxia pathway in primary advanced uterine cervical carcinoma

Abstract

Abstract. The development of cervical cancer exhibits some unique differences compared to other solid tumors. Normal cervical stratified epithelia have characteristics of hypoxic tissue. Lack of oxygen (hypoxia) induces the HIF-1 (hypoxiainducible factor-1) transcription factor, which is a heterodimer composed of a constitutively expressed β subunit and a hypoxia-inducible α-subunit. HIF-1A targets the transcription of over 70 genes involved in many aspects of cancer biology. In well-oxygenated environments, the HIF-1A subunit is hydroxylated, recognized and marked for proteosomal destruction by an E3 ubiquitin ligase, the von Hippel-Lindau protein (pVHL) complex. Under hypoxic stress, proline hydroxylase (PHD) activity is diminished, and stabilized HIF-1A is involved in the activation of the tissue response to hypoxia. Here, we examined the HIF-1A and VHL transcript levels and HIF-1A protein levels in cancerous tissue (n=30) and non-cancerous, normal uterine cervical tissue (n=30). We also compared the methylation status of HIF-1A and of the VHL promoter regions in cancerous and normal tissue samples. Significantly higher levels of HIF-1A and VHL transcripts (p<0.0001 and p= 0.0042, respectively) and of HIF-1A protein (p= 0.0037) were detected in cancerous tissue compared to normal samples. We did not observe DNA methylation in the HIF-1A and VHL promoter region in either control or cancerous tissue samples. VHL has a functional hypoxia response element (HRE) in the promoter region, and the induction of this HRE acts within a negative feedback loop to limit the hypoxic HIF-1A response. Our findings may suggest that HIF-1A could promote its own degradation by the induction of VHL gene expression (Spearman correlation coefficient, 0.515; p=0.003). Our study shows for the first time that this increase in VHL expression could be HIF-1A-dependent and serves within a negative feedback pathway during hypoxia to regulate the cell-specific oxygen threshold for HIF-1A activation.

Prognostic Potential of DNA Methylation and Transcript Levels of HIF1A and EPAS1 in Colorectal Cancer

“…To evaluate the statistically significant difference in the ratio of cancerous EPAS1 mRNA level to histopathologically unchanged tissue EPAS1 mRNA level between the three DNA methylation ranges (0%-1% methylation, 1%-10% methylation, and 10%-100% methylation), the nonparametric Kruskal-Wallis test was used. HIF1A mRNA levels were increased in cancerous compared with noncancerous tissue (8,11,12,33,34). However, other studies reported a constant HIF1A mRNA level in tumor cells and suggested mainly posttranslational regulation of HIF1A expression (35)(36)(37), which is consistent with our observations.…”

“…Data about DNA methylation of the HIF1A promoter region are ambiguous. The absence of DNA methylation of the HIF1A promoter was observed in advanced uterine cervical carcinoma and datasets available at ENCODE project, whereas DNA hypermethylation was observed in an immature hematopoietic cell line HMC-1 and normal colon tissues isolated from 20 patients with colorectal cancer (14,34,45). In our studies, DNA methylation of the HIF1A promoter was undetected in a group of 120 patients.…”

Transcriptional analysis of CXCR4, DNMT3A, DNMT3B and DNMT1 gene expression in primary advanced uterine cervical carcinoma

“…We also did not observe changes in the DNA methylation pattern in the CXCR4 promoter region in either control or cancer tissue samples (data not shown). In our previous report we found significantly increased HIF-1A transcript and protein levels in tumor tissue samples compared to their normal, non-cancer counterpart (29). A statistically significant association was found between HIF-1A (31,32).…”

Biomarkers Expression in Cervical Cancer and High Grade Squamous Intraepithelial Lesions

“…HIF1 influences the expression of a diverse set of genes associated with tumor progression, e.g. eritropoyetin (Epo), transferrin, endothelin-1, iNOS, Glut-1 transporter, VEGF and inflammatory molecules as well as pro-and antiapoptotic genes [16][17][18]. Cancer cervix hypoxia has been described to be independent of clinical size, grade and FIGO stage [19,20] and is nowadays considered a powerful independent prognostic factor for the outcome of the disease [11,21].…”