Entwicklung apoptose-induzierender und immunmodulierender, replikations-selektiver Adenovirus-Vektoren für die Therapie von malignen Tumoren

Zusammenfassung der Projektergebnisse

Adenovirus (Ad) serotype 5 based vectors have been developed as therapeutics for cancer in the recent decade and are the most frequently used viral gene vectors in clinical trials. In this project (1) basic interactions between Ads and the host were investigated (basic virology) and (2) strategies were tested to utilize Ads as tools to induce immune responses against tumors (cancer immunotherapy). Basic virology: Since Ad serotype 5 uses a cellular receptor (CAR) that is commonly not expressed at high levels on cancer cells, the receptor usage of other Ad serotypes was investigated. It was shown that specific Ad serotypes (Ad3, 7, 11,14) use a cellular receptor that is overexpressed on cancer cells. This receptor was termed "receptor X" and current studies aim to identify this receptor. Based on usage of this receptor and the alternative receptor CD46 a revised grouping system of species B adenoviruses was proposed. It was also shown that cellular heparan sulfate proteoglycans act as coreceptors for specific Ad serotypes. Additionally, the toxicity of specific Ads upon systemic administration was evaluated in mice. Overall, these studies contributed to better understand Ad-host interaction and to identify Ad serotypes that might be more efficient tools for cancer therapy than the commonly used Ad5-based vectors. Cancer immunotherapy: The interaction between Ad-vectors, host immune system and the tumor was studied in syngeneic immune-competent breast and cervical cancer models in vivo. In short, it was shown that Ad-replication and expression of specific adjuvants via Ads (e.g. sgp96, lacZ) can increase the immunotherapeutic potential of Ads. Surprisingly, it was found that also the Ad-vector itself has a therapeutic effect via induction of Ad-specific T cells that eliminate Ad-infected cancer cells. Another unexpected finding was that pre-existing anti-Ad immunity can increase the immunotherapeutic potential of Ads. The studies also showed that tumor-site located immune tolerance mechanisms (in particular tumor-infiltrating Tregs) limit the therapeutic success of immunotherapy, and strategies to overcome these mechanisms were developed, in particular tumor-site located expression of anti-CTLA-4 antibody and systemic administration of low-dose cyclophosphamide. Overall, these studies indicate a potential of Ads as immunotherapeutics for cancer, in particular when intratumorally applied and combined with strategies that counteract intratumoral immune tolerance.

Projektbezogene Publikationen (Auswahl)

• A new group B adenovirus receptor is expressed at high levels on human stem and tumor cells. J Virol. 80(24): 12109-20, 2006
  Tuve S, Wang H, Ware C, Liu Y, Gaggar A, Bernt K, Shayakhmetov D, Li Z, Strauss R, Stone D, Lieber A
  
• Effect of adenovirus-mediated heat shock protein expression and oncolysis in combination with low-dose cyclophosphamide treatment on antitumor immune responses. Cancer Res. 66(2):960-969, 2006
  Tuve S, Di Paolo NC, Ni S, Hellstrom KE, Hellstrom I, Lieber A
  
• Evaluation of adenovirus vectors containing serotype 35 fibers for vaccination. Mol Ther. 13(4):756-765, 2006
  DiPaolo N, Ni S, Gaggar A, Strauss R, Tuve S, Li ZY, Stone D, Shayakhmetov DS, Kiviat N, Toure P, Sow S, Horvart B, Lieber A
  
• Combination of tumor site-located CTL-associated antigen-4 blockade and systemic regulatory T-cell depletion induces tumor-destructive immune responses. CancerRes. 67(12).5929-39,2007
  Tuve S, Chen BM, Liu Y, Cheng TL, Toure P, Sow PS, Feng Q, Kiviat N, Strauss R, Ni S, Li ZY, Roffler SR, Lieber A
  
• Comparison of adenoviruses from species B, C, E, and F after intravenous delivery. Mol Ther. 15(12):2146-53, 2007
  Stone D, Liu Y, Li ZY, Tuve S, Strauss R, Lieber A
  
• Identification of CD46 binding sites within the adenovirus serotype 35 fiber knob. J Virol. 81(23): 12785-92, 2007
  Wang H, Liaw YC, Stone D, Kalyuzhniy O, Amiraslanov I, Tuve S, Verlinde CL, Shayakhmetov D, Stehle T, Roffler S, Lieber A
  
• In vitro and in vivo properties of adenovirus vectors with increased affinity to CD46. J Virol, 82(21):10567-10579, 2008
  Wang H, Liu Y, Li Z, Tuve S, Stone D, Kalyushniy O, Shayakhmetov D, Verlinde CL, Stehle T, McVey J, Baker A, Peng KW, Roffler S, Lieber A
  
• Role of cellular heparan sulfate proteoglycans in infection of human adenovirus serotype 3 and 35. PloS Pathog., 4(10):e1000189,2008
  Tuve S, Wang H, Jacobs JD, Yumul RC, Smith DF, Lieber A