engleski

What we can learn about adenovirus biology from infection of cancer cells resistant to chemotherapeutics?

Human adenovirus serotype 5 (Ad5) offers great promise in cancer gene therapy where a transient high-level expression of therapeutic gene products is required. Cancer cells exhibit extremely variable Ad5 vector uptake. The success of Ad5-mediated tumor gene therapy depends on (i) the efficient adenovirus entry through CAR and integrins, (ii) the efficient release of adenovirus from the endosome, (iii) the efficient translocation of adenovirus to the cell nucleus, and (iv) the efficient expression of the therapeutic transgene from a given promoter. Development of drug-resistance is a major obstacle for the successful treatment of cancer patients. It is expected that gene therapy will be more frequently used in patients previously subjected to chemotherapy and/or whose tumors have developed resistance to chemotherapeutics. In our laboratory, several cell clones derived from human laryngeal carcinoma HEp2 cell line resistant to chemotherapeutics have been isolated: cell clones CA3ST and CK2 are resistant to cisplatin and cell clone VK2 is resistant to vincristine. In all three cell clones approximately 5-fold increased Ad5-mediated transgene expression, as compared to the parental cells HEp2, has been demonstrated and the causes investigated. In the cell clone CA3ST the increased expression of CAR and integrin αvβ3 have been observed and both of them are responsible for the increased Ad5-mediated transgene expression. In addition, the causative relationship between integrin αvβ3 expression and cisplatin resistance was confirmed by isolation of the stable HEp2-derived integrin αvβ3 transfectants. The increased expression of integrin αvβ3 in HEp2 cells confers resistance to several antitumor drugs (cisplatin, mitomycin C and doxorubicin) due to the increased total glutathione content that enables more efficient elimination of the druginduced reactive oxidative species. In the second cell clone VK2, that is resistant to vincristine, the activity of frequently used promoters used for transgene expression in Ad5 vectors was analysed. The dramatic increase of RSV promoter activity was found in VK2, as compared to the HEp2 cells, and this activity was even higher than the activity of promoter CMV. Finally, in the third HEp2-derived cell clone CK2 resistant to cisplatin the RhoB downregulation was found to be responsible for the cisplatin resistance. The cause of the increased Ad5-mediated transgene expression in CK2 cells, as compared to HEp2, was shown to be the decreased RhoB expression. We showed that the down-regulation of RhoB significantly increased Ad5-mediated transgene expression in HEp2 and CK2 cells, without changing the amount of the attached or internalized Ad5wt in either cell line. It was proposed that RhoB plays an important role in Ad5 post-internalization events, and more particularly in Ad5 intracellular trafficking. According to our results, obtained in three HEp2-derived cell clones resistant to different chemotherapeutics, the resistant cells could be better targets than the initial tumor due to the variety of mechanisms. The investigation of Ad5 infection in cancer cells resistant to chemotherapeutics, as compared to parental cancer cells, can identify new molecules implicated into Ad5 infection. It remains to be determined whether changes in such molecules could be used for a prediction of the efficacy of Ad5-mediated tumor gene therapy in patients bearing tumors resistant to chemotherapeutic drugs.

tumor; drug resistance; adenovirus

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