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: CY caused hemorrhagic cystitis in 40 % of rats , but it did not cause this complication when combined with 5 - FU and MTX .
### Output Text:
<span class="chemical">CY</span> caused hemorrhagic cystitis in 40 % of rats , but it did not cause this complication when combined with <span class="chemical">5 - FU</span> and <span class="chemical">MTX</span> . 