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: Briefly , cells were differentiated for 72 h with 100 nM PMA to obtain a macrophage - like phenotype in the presence or absence of 1 nM 17beta - estradiol ( E2 ) , 100 nM progesterone or vehicle ( 0 . 01 % ethanol ) .
### Output Text:
Briefly , cells were differentiated for 72 h with 100 nM PMA to obtain a macrophage - like phenotype in the presence or absence of 1 nM <span class="chemical">17beta - estradiol</span> ( <span class="chemical">E2</span> ) , 100 nM <span class="chemical">progesterone</span> or vehicle ( 0 . 01 % <span class="chemical">ethanol</span> ) . 