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: Comparison of the two biopsies showed that temsirolimus inhibited tumor cell proliferation through cell cycle arrest , but did not induce any change in the number of apoptotic tumor cells .
### Output Text:
Comparison of the two biopsies showed that <span class="chemical">temsirolimus</span> inhibited tumor cell proliferation through cell cycle arrest , but did not induce any change in the number of apoptotic tumor cells . 