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: Such abnormalities were not observed in the mitochondria of liver tissue ; and 3 ) among the three genes of COX enzyme examined , only COXII gene expression was suppressed by ADR treatment , mainly after 8 weeks in both heart and liver .
### Output Text:
Such abnormalities were not observed in the mitochondria of liver tissue ; and 3 ) among the three genes of COX enzyme examined , only COXII gene expression was suppressed by <span class="chemical">ADR</span> treatment , mainly after 8 weeks in both heart and liver . 