Limitations of the reporter green fluorescent protein under simulated tumor conditions

This paper reports a detailed analysis of the effect of low oxygen conditio ns (hypoxia) on the reporter green fluorescent protein (GFP). It questions the feasibility of using GFP fur gene expression studies under tumor condit ions. Hypoxia is a characteristic of both experimental and clinical tumors. Several important factors are pointed out which need to be considered when using GFP as reporter gene. GFP fluorescence is the final product of a lon g and complex pathway involving transcription, translation, and posttransla tional modifications. All of these steps may be affected by the availabilit y of oxygen. We show specifically that cellular GFPfluorescence decreased w ith reduced oxygenation, anoxia virtually eliminated fluorescence and prote in levels, and fluorescence recovery after anoxia required 5-10 h of reoxyg enation, In conclusion, GFP appears to be a good marker gene to study locat ion or movement of proteins or cells but should he used with great caution as a reporter of gene expression under tumor renditions.