2.

肿瘤细胞耐药的典型分子机制。常见耐药的主要途径有：（1）由于细胞表面受体或转运体缺失导致药物不能进入细胞内；（2）药物靶点改变；（3）药物的改变或失活；（4）药物代谢途径改变；（5）损伤DNA修复增加；（6）药物被主动运输到细胞外。

The molecular mechanisms of drug resistance in tumor cells. The main pathways of drug resistance: (1) The drug can not get into the cell due to lost of cell surface receptors or transporters; (2) Mutations in drug target; (3) Changes or inactivation of the drug; (4) Changes in the drug metabolism pathway; (5) Increased repair of damaged DNA; (6) Drug is exported by active transportation.