Myeloid and plasmacytoid dendritic cell combined vaccines loaded with heat-treated tumor cell lysates enhance antitumor activity in murine lung cancer

The present study aimed to investigate the efficacy of a myeloid dendritic cell (mDCs) and plasmacytoid (p)DC combined vaccine loaded with heat-treated cancer cell lysates against lung cancer cells. The mDCs and pDCs were selected using magnetic bead sorting. Antigen loading was performed by adding heat-treated Lewis lung cancer cell lysates to mDC, pDC or mDC+pDC (1:1). Surface expression of CD80, CD86, CD40 and major histocompatibility complex (MHC)-II molecules were determined using flow cytometry, and the secretion of cytokines IL-12, IL-6 and TNF-α were assessed using ELISA assays. The effect of the mDC and pDC vaccine on cytotoxic T lymphocytes (CTLs) against tumor cells was investigated. Tumor-bearing nude mice were intravenously injected with the mDC and pDC combined vaccine. Tumor tissues were collected for hematoxylin and eosin and TUNEL staining. Loading with tumor cell lysate significantly upregulated the surface expression of costimulatory molecules MHC-II on DCs and enhanced secretions of IL-6, IL-12 and TNF-α by DCs. In addition, the tumor cell lysate-loaded mDC and pDC combined vaccine significantly promoted lymphocyte proliferation and enhanced CTL-mediated cytotoxicity against Lewis lung cancer cells compared with mDC or pDC treatment alone. Furthermore, intravenous injection of the mDC and pDC combined vaccine into tumor-bearing nude mice significantly inhibited subcutaneous tumor growth and induced necrosis and apoptosis within the tumor tissue. Overall, the pDC and mDC combination vaccine loaded with heat-treated Lewis lung cancer cell lysate had a synergistic effect on the induction of T lymphocyte proliferation and antitumor efficacy, which may be associated with the upregulation of co-stimulatory molecules and cytokine secretions.