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: In DOX B1R ( - / - ) mice , cardiac dysfunction was improved compared to DOX control mice , which was associated with normalization of the bax / bcl - 2 ratio and interleukin 6 , as well as AKT activation state .
### Output Text:
In <span class="chemical">DOX</span> B1R ( - / - ) mice , cardiac dysfunction was improved compared to <span class="chemical">DOX</span> control mice , which was associated with normalization of the bax / bcl - 2 ratio and interleukin 6 , as well as AKT activation state . 