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: Although there was a discrepancy between the amount of cTnI and cTnT after DOX , probably due to heterogeneity in cross - reactivities of mAbs to various cTnI and cTnT forms , it is likely that cTnT in rats after DOX indicates cell damage determined by the magnitude of injury induced and that cTnT should be a useful marker for the prediction of experimentally induced cardiotoxicity and possibly for cardioprotective experiments .
### Output Text:
Although there was a discrepancy between the amount of cTnI and cTnT after <span class="chemical">DOX</span> , probably due to heterogeneity in cross - reactivities of mAbs to various cTnI and cTnT forms , it is likely that cTnT in rats after <span class="chemical">DOX</span> indicates cell damage determined by the magnitude of injury induced and that cTnT should be a useful marker for the prediction of experimentally induced cardiotoxicity and possibly for cardioprotective experiments . 