Purpose: Expression of erythropoietin (Epo) and its receptor (Epo-R) has been shown in various normal and neoplastic nonhematopoietic tissues. This study, in non-small cell lung carcinoma, was designed to investigate the previously unreported expression of Epo and Epo-R as well as hypoxia-inducible factor-1alpha (HIF-1alpha), which is known to control Epo expression.
Experimental design: Samples from lung squamous cell carcinomas (n = 17) and adenocarcinomas (n = 12) were obtained from patients undergoing curative surgery. mRNA transcripts of Epo, Epo-R, soluble Epo-R (sEpo-R), HIF-1alpha, and factor inhibiting HIF-1 (FIH-1) were evaluated by reverse transcription-PCR, whereas localization of Epo, Epo-R, and HIF-1alpha was assessed by immunohistochemistry.
Results: Epo, Epo-R, sEpo-R, HIF-1alpha, and FIH-1 transcripts were detected by reverse transcription-PCR in all samples tested, but with heterogeneous levels of expression for Epo, Epo-R, and sEpo-R. Coordinated levels of mRNA were observed for HIF-1alpha and FIH-1.Epo was detected in carcinomatous cells by immunohistochemistry in 50% of samples and Epo-R was detected in 96% of samples. Co-expression of Epo and Epo-R was observed on contiguous sections from 50% of tumors. HIF-1alpha was immunolocalized in 80% of non-small cell lung carcinomas.
Conclusion: Epo-R was expressed in almost all samples and Epo was expressed in one half of samples on immunohistochemistry and in 100% of samples by mRNA detection, suggesting a potential paracrine and/or autocrine role of endogenous Epo in non-small cell lung carcinoma. The detection of stabilized HIF-1alpha suggests a possible role in Epo expression. Moreover, in the light of these results, the potential interactions between therapeutic recombinant Epo and the putative neoplastic Epo/Epo-R signaling pathways must be considered.