Macrophage cell-derived exosomes/staphylococcal enterotoxin B against fibrosarcoma tumor.

Targeted immune therapies are a modern approach to harness the immunity to treat cancer patients. Exosomes (EXOs) are nano-vesicles used for drug delivery in cancer treatment. We aimed to assess the effectiveness of novel designed EXO structures for immunotherapy alone and in combination with other components in animal models. EXO derived from untreated macrophage (EXO), WEHI-164 cell lysate treated EXO (EXO), HSP70 enriched WEHI-164 cell lysate treated EXO (EXO), Naloxone (NLX) treated EXO (EXO), Propranolol (PRP) treated EXO (EXO) and staphylococcal enterotoxin B (SEB) anchored to three kinds of EXOs designated as EXO/SEB, EXO/SEB, EXO/SEB were purified from J774 cell line. To determine the therapeutic effect of these novel constructed nano-vesicles, the animals were immunized with different types of EXOs at weekly intervals for three consecutive weeks and in the fourth week the WEHI-164 tumor cells were injected. Finally, the splenocyte proliferation was examined by MTT assay and tumor growth was also determined in each group. We observed that EXO was more effective than EXO and EXO to decrease the number of tumor cells and to stimulate immune responses in animal models (P < 0.05). In SEB-anchored EXO group, EXO/SEB has the potency to stimulate immune responses more efficiently than EXO/SEB and EXO/SEB and the tumor was not palpable until 28th day which may refer to synergistic effect of HSP70 and SEB on immunity. In EXO treated mice proliferative response decreased significantly compared to control group (P > 0.05) and the tumor number was constant within a period of 28 days and EXO may delay the occurrence of the fibrosarcoma tumor; After development of fibrosarcoma the number of tumors diminished over the studied period of time. Our results demonstrate that HSP70 enriched EXO is an effective immunoadjuvant in cancer immunotherapy and causes tumor regression in animal model.