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: As a regulated secretory protein , BRCA1 appears to function by a mechanism not previously described for tumour suppressor gene products . .
### Output Text:
As a regulated secretory protein , BRCA1 appears to function by a mechanism not previously described for <span class="disease">tumour</span> suppressor gene products . . 