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

### Input Text: In Drosophila cells , cotransfected VHL represses Sp1 - mediated activation but not basal activity of the VEGF promoter .
### Output Text:
In Drosophila cells , cotransfected VHL represses Sp1 - mediated activation but not basal activity of the VEGF promoter . 