In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: VEGF / VPF and FVIIIRAg immunohistochemistry and endothelial specific lectin ( UEA1 ) binding studies , indicate that the elevation of VEGF protein expression initially occurred in both blood vessels and non - endothelial cells .
### Output Text:
VEGF / VPF and FVIIIRAg immunohistochemistry and endothelial specific lectin ( UEA1 ) binding studies , indicate that the elevation of VEGF protein expression initially occurred in both blood vessels and non - endothelial cells . 