Abstract:
Many in vivo and in vitro studies have demonstrated the crucial role of dendritic cells (DC) in activating T-lymphocytes. In this study, we aimed to investigate the therapeutic roles of DC in breast cancer using in vitro and in vivo models. We also compared the therapeutic efficacy between cryopreserved and freshly generated DC using the same approaches. Human DC were generated from peripheral blood mobilised CD34+ human haematopoietic stem cells (HSC) using appropriate cytokines cocktail. The resulting DC were characterised based on morphology, phenotype and functional properties such as their ability to induce tumour-specific cytotoxic T-lymphocytes (CTL) against human breast cancer cell lines in vitro.
Murine DC were generated from bone marrow (BM) cells harvested from female BALB/c mice and were similarly characterised. The mouse DC were found to be CD11C+CD11b+CD4-CD8- i.e. double negative dendritic cells (DNDC). An animal model using murine breast cancer cells was established for in vivo studies. The cryopreserved and freshly generated DNDC showed similar morphology and phenotype. These DC were pulsed with tumour lysate and injected into experimental animals with established tumours. Both cryopreserved and freshly generated DC were able inhibit the growth of established tumours in a similar manner. The mean time for tumour volume to reach 500 mm3 was significantly delayed (P<0.05) in mice treated with either freshly generated (33.9 days) or cryopreserved (35 days) BM-DC as compared to control mice (25.7 days). In another model, mice were vaccinated with tumour lysate-pulsed dendritic cells (TPDC) prior to the induction of breast cancer. Tumour growth in vaccinated mice were found to be significantly (P<0.05) slower as compared to control untreated mice. The mean time for tumour volume of control and DC-vaccinated mice group to reach the 500 mm3 was 24.3 days and 48.2 days respectively.
Tumour lysate-pulsed DNDC (TPDC) and unpulsed DNDC produced no IFN- even in the presence of IL-12 or both IL-12 and IL-2. T-lymphocytes cultured with TPDC produced higher IFN- and lower IL-4 and IL-10 level, indicating that a Th1 immune response was elicited by DNDC.
Our data show that DC generated from CD34+ HSC are capable of eliciting immune response towards human breast cancer in vitro. Murine bone-marrow-derived DNDC were shown to have different functional properties from previously described DNDC isolated from mouse spleen. These findings offer new insights into the functional properties of DNDC from different sources. We also showed that cryopreserved and freshly generated murine DC share similar therapeutic efficacy and causes an initial retardation in tumour growth shortly after they are administered.
