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: Our studies indicate that nephrotoxicity of MTX + 5 - FU + CY administered jointly is lower than in monotherapy .
### Output Text:
Our studies indicate that nephrotoxicity of <span class="chemical">MTX</span> + <span class="chemical">5 - FU</span> + <span class="chemical">CY</span> administered jointly is lower than in monotherapy . 