18892
Experimental models including yeast and mammalian cell cultures suggest three general mechanisms of camptothecin resistance : i ) reduced cellular accumulation of drugs , ii ) alteration in the structure / expression of topoisomerase I , and iii ) alterations in the cellular response to camptothecin - DNA - ternary complex formation .
 Chemical: camptothecin; Chemical: camptothecin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: camptothecin; Chemical: camptothecin