Leila Rostamizadeh
1 
, Ommoleila Molavi
2,3* , Mohsen Rashid
1, Fatemeh Ramazani
1, Behzad Baradaran
4, Afsaneh Lavasanaifar
5, Raymond Lai
61 Department of Molecular Medicine, Faculty of Advanced Medical Science, Tabriz University of Medical Sciences, Tabriz, Iran
2 Biotechnology Research Centre, Tabriz University of Medical Sciences, Tabriz, Iran
3 Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
4 Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
5 Faculty of Pharmacy and Pharmaceutical Science, University of Alberta, Edmonton, Canada
6 Department of Laboratory Medicine & Pathology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Canada
Abstract
Immunotherapy is considered a promising approach for cancer treatment. An important strategy for cancer immunotherapy is the use of cancer vaccines, which have been widely used for cancer treatment. Despite the great potential of cancer vaccines for cancer treatment, their therapeutic effects in clinical settings have been limited. The main reason behind the lack of significant therapeutic outcomes for cancer vaccines is believed to be the immunosuppressive tumor microenvironment (TME). The TME counteracts the therapeutic effects of immunotherapy and provides a favorable environment for tumor growth and progression. Therefore, overcoming the immunosuppressive TME can potentially augment the therapeutic effects of cancer immunotherapy in general and therapeutic cancer vaccines in particular. Among the strategies developed for overcoming immunosuppression in TME, the use of toll-like receptor (TLR) agonists has been suggested as a promising approach to reverse immunosuppression. In this paper, we will review the application of the four most widely studied TLR agonists including agonists of TLR3, 4, 7, and 9 in cancer immunotherapy.