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: The mechanism of action is postulated as mitomycin C - induced endothelial cell damage .
### Output Text:
The mechanism of action is postulated as <span class="chemical">mitomycin C</span> - induced endothelial cell damage . 