molecular drivers present in a tumor biol.

[dao2812]

Thus, there has been rapid expansion of prognostic mRNA expression based assays to classify breast tumors (Loi et al., 2007; Paik et al., 2004; Parker et al., 2009; van 't Veer et al., 2002). However, currently available prognostic signatures fail to link changes in gene expression to the "molecular drivers" present in a given tumor

Как перевести drivers в данном случае? Стимулы, причины, основы?
Но для указанного не подходит присутсвующие в опухоли.