Hypoxic Gene Signature of Primary and Metastatic Melanoma Cell Lines: Focusing on HIF-1β and NDRG-1

Abstract

Background: Hypoxia is an important microenvironmental factorsignificantly affecting tumor proliferation and progression. Theimportance of hypoxia is, however, not well known in oncogenesis ofmalignant melanoma.Aims: To evaluate the difference of hypoxic gene expressionsignatures in primary melanoma cell lines and metastatic melanomacell lines and to find the expression changes of hypoxia-related genesin primary melanoma cell lines at experimental hypoxic conditionsStudy Design: Cell study.Methods: The mRNA expression levels of hypoxia-related genes inprimary melanoma cell lines and metastatic melanoma cell lines and atexperimental hypoxic conditions in primary melanoma cell lines wereevaluated by using real-time polymerase chain reaction. Dependingon the experimental data, we focused on two genes/proteins,the hypoxia-inducible factor-1 beta and the N-myc downstreamregulated gene-1. The expression levels of the two proteins wereinvestigated by immunohistochemistry methods in 16 primary andmetastatic melanomas, 10 intradermal nevi, and a commercial tissuearray comprised of 208 cores including 192 primary and metastaticmalignant melanomas.Results: The real-time polymerase chain reaction study showedthat hypoxic gene expression signature was different betweenmetastatic melanoma cell lines and primary melanoma cell lines.Hypoxic experimental conditions significantly affected the hypoxicgene expression signature. In immunohistochemical study, N-mycdownstream regulated gene-1 expression was found to be lowerin primary cutaneous melanoma compared to in intradermal nevi(p=0.001). In contrast, the cytoplasmic expression of hypoxiainducible factor-1 beta was higher in primary cutaneous melanomathan in intradermal nevi (p=0.001). We also detected medium/strongsignificant correlations between the two proteins studied in the studygroups.Conclusion: Hypoxic response consists of closely related proteins inmore complex pathways. These findings will shed light on hypoxicprocesses in melanoma and unlock a Pandora’s box for developmentof new therapeutic strategies.