In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: Overexpression of ATM cDNA in A - T cells enhanced the survival of these cells in response to radiation exposure , decreased radiation - induced chromosome aberrations , reduced radio - resistant DNA synthesis , and partially corrected defective cell cycle checkpoints and induction of stress - activated protein kinase .
### Output Text:
Overexpression of ATM cDNA in <span class="disease">A - T</span> cells enhanced the survival of these cells in response to radiation exposure , decreased radiation - induced chromosome aberrations , reduced radio - resistant DNA synthesis , and partially corrected defective cell cycle checkpoints and induction of stress - activated protein kinase . 