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: Immunoprecipitation / Western blotting showed that Smad3 was activated by AGEs but was inhibited by SIS3 in MMECs and in STZ - induced diabetic nephropathy .
### Output Text:
Immunoprecipitation / Western blotting showed that Smad3 was activated by AGEs but was inhibited by SIS3 in MMECs and in <span class="chemical">STZ</span> - induced diabetic nephropathy . 