Antitumor immune response elicited by M2 TAM-specific DDS <i>via</i> C-type lectin CD209b using cholesteryl pullulan nanogel as a protein drug carrier

Many cancer patients develop resistance to immunotherapy, highlighting the urgent need for novel therapeutic strategies. Various factors contribute to tumor resistance to immunotherapy, among which tumor-associated macrophages (TAMs) are critical regulators of tumor sensitivity. Therefore, combining cancer immunotherapies with drug delivery systems (DDSs) targeting TAMs has become an intriguing treatment strategy. However, the target molecules used in DDSs are limited to a few receptors expressed on TAMs. Therefore, the identification of novel target molecules for TAM-specific DDS is urgently needed. The current study evaluated the ability of a cholesteryl pullulan (CHP) nanogel to target TAMs <i>via</i> mDC-SIGN (CD209b). This nanogel encapsulated the cytotoxic protein drug Pseudomonas exotoxin A and was injected into a tumor-bearing mouse model. This treatment significantly reduced the abundance of CD209b-positive M2 TAMs and enhanced antitumor immune responses. Ultimately, tumor growth was suppressed, even in a low-immunogenic tumor model. Hence, CD209b is an effective target molecule for M2 TAM-specific DDSs that can be used to develop novel cancer therapies.