Hypoxia-Inducible Erythropoietin Signaling in Squamous Dysplasia and Squamous Cell Carcinoma of the Uterine Cervix and Its Potential Role in Cervical Carcinogenesis and Tumor Progression

Abstract

Tissue hypoxia is a characteristic property of cervical cancers that makes tumors resistant to chemo- and radiation therapy. Erythropoietin (Epo) is a hypoxia-inducible stimulator of erythropoiesis. Acting via its receptor (EpoR), Epo up-regulates bcl-2 and inhibits apoptosis of erythroid cells and rescues neurons from hypoxic damage. In addition to human papillomavirus infection, increased bcl-2 expression and decreased apoptosis are thought to play a role in the progression of cervical neoplasia. Using reverse transcriptase-polymerase chain reaction and Western blotting we showed that HeLa and SiHa cervical carcinoma cells and human cervical carcinomas express EpoR, and that hypoxia enhances EpoR expression. Exogenous Epo stimulated tyrosine phosphorylation and inhibited the cytotoxic effect of cisplatin in HeLa cervical carcinoma cells. Using immunohistochemistry, we examined the expression of Epo, EpoR, p16, hypoxia-inducible factor (HIF)-1alpha, and bcl-2 in benign and dysplastic cervical squamous epithelia and invasive squamous cell carcinomas (ISCCs). EpoR expression in benign epithelia was confined to the basal cell layers, whereas in dysplasias it increasingly appeared in more superficial cell layers and showed a significant correlation with severity of dysplasia. Diffuse EpoR expression was found in all ISCCs. Expression of Epo and HIF-1alpha was increased in dysplasias compared to benign epithelia. Focal Epo and HIF-1alpha expression was seen near necrotic areas in ISCCs, and showed correlation in their spatial distribution. Significant correlation was found between expression of EpoR, and p16 and bcl-2 in benign and dysplastic squamous epithelia. Our results suggest that increased expression of Epo and EpoR may play a significant role in cervical carcinogenesis and tumor progression. Hypoxia-inducible Epo signaling may play a significant role in the aggressive behavior and treatment resistance of hypoxic cervical cancers.

Prognostic significance of erythropoietin expression in human endometrial carcinoma

“…The spatial distribution of increased Epo immunoreactivity was quite similar to that of HIF-1␣, the expression of which was also confined to tumor regions adjacent to necrotic areas, which are believed to be among the most hypoxic sites. 20 The patterns of Epo and HIF-1␣ expression were similar to those observed in cervical squamous cell carcinomas 12 and were consistent with the known regulation of Epo expression by HIF-1. 2 In contrast, EpoR expression was uniform and homogenous, although increased expression was present in tumor cells adjacent to necrotic areas.…”

“…6,12 For Epo in cytoplasm, EpoR in cytoplasm and/or the cell membrane, and ER, PR, and HIF-1␣, nuclear immunoreactivity was considered to indicate positivity. The percentage of weakly, moderately, and strongly staining cells was determined, and a staining score was calculated as follows: score (maximum, 300) ϭ 1 ϫ the percentage of weakly staining cells ϩ 2 ϫ the percentage of moderately staining cells ϩ 3 ϫ the percentage of strongly staining cells.…”

“…8 Previous studies have shown that cultured human breast and cervical carcinoma cells, as well as other carcinoma cells, express high levels of EPO/Epo and EPOR/EpoR mRNA and protein. 5,12 Exposure of the tumor cells to recombinant human Epo (rHuEpo) stimulated tyrosine phosphorylation and DNA synthesis and proliferation, suggesting that Epo signaling is biologically active in malignant cells. 5,12 EpoR expression also has been found in tumors of the female genital tract, including ovarian and endometrial carcinomas.…”

“…5,12 Exposure of the tumor cells to recombinant human Epo (rHuEpo) stimulated tyrosine phosphorylation and DNA synthesis and proliferation, suggesting that Epo signaling is biologically active in malignant cells. 5,12 EpoR expression also has been found in tumors of the female genital tract, including ovarian and endometrial carcinomas. 13 Endometrial adenocarcinoma is the most common malignancy of the female genital tract and the fourth most common malignancy among women in the United States.…”

Hypoxia-associated markers in gastric carcinogenesis and HIF-2α in gastric and gastro-oesophageal cancer prognosis

“…Researchers have hypothesised that hypoxia plays a primary role in the carcinogenesis process. Studies have shown progressively increased HIF-1a expression in breast (Bos et al, 2001), skin (Costa et al, 2001) and cervical (Acs et al, 2003) cancer development. More recently, we have shown increased expression of HIF-1a in gastric cancer development (Griffiths et al, 2007b) and in adenocarcinoma vs dysplasia in the Barrett's oesophageal cancer sequence (Griffiths et al, 2007a).…”