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: Activation of poly ( ADP - ribose ) polymerase contributes to development of doxorubicin - induced heart failure .
### Output Text:
Activation of <span class="chemical">poly ( ADP - ribose )</span> polymerase contributes to development of <span class="chemical">doxorubicin</span> - induced heart failure . 