It has been hypothesized that ITADT may be unable to induce efficient antitumour effects because injected DC residing GS-1101 manufacturer within the tumour cannot efficiently migrate to the lymph nodes [36]. However, in this study, we hypothesized that

this characteristic of the intratumourally delivered DC may enhance the antitumour effect of ITADT through the efficient mobilization of host-derived APC and the subsequently enhanced TAA-specific CD8+ T-cell responses. In our experiments, although small numbers of i.t.-injected DC were detected in the draining lymph nodes on day 1 of ITADT, the frequency of the injected DC in the draining lymph nodes was not correlated with the antitumour effects observed, but the survival

time of the injected DC within the tumour was correlated. These findings support our hypothesis regarding the antitumour effects of ITADT. We believe that skin-derived or blood-derived tumour-associated APC may be crucial for successful ITADT, and the longer the activated DC reside within the tumour, the more efficiently host-derived APC may mobilize to the tumour, engulf TAA, migrate into the lymph nodes and finally prime TAA-specific CD8+ T cells. This is not the case for SCDT, where endogenous DC in the lymph nodes participate in the amplification of the T-cell response [37], because the injected DC rapidly migrate into the draining lymph nodes [9]. However, it is likely that DC–tumour cell hybrids also Selleck 3-deazaneplanocin A may reside at the injected site. Such cells are large and cannot migrate

into lymph node, resulting in the efficient mobilization of host-derived APC [38, 39]. In DC-based immunotherapy, Avelestat (AZD9668) allogeneic DC are considered an important source of DC for some patients, especially paediatric cancer patients. However, previously reported preclinical data have been negative about the efficacy of allogeneic DC in immunotherapy in which SCDT using peptide- or tumour lysate-pulsed fully allogeneic or semi-allogeneic DC were used [14, 22–24]. Alloreactive T-cell response to the alloantigens expressed by the injected DC themselves had been expected to provide the injected DC with additional danger signals via costimulatory-related molecules (such as CD40-CD40L signalling [40–42]) or bystander production of T-cell growth factors, resulting in enhanced priming of T-cell responses [21]. However, this positive effect of alloantigens in MHC-disparate donor–recipient combinations might only be obtainable in DC-based immunotherapy with DC–tumour hybrids, where fully allogeneic or semi-allogeneic DC–tumour cell fusions show enhanced antitumour effects compared with syngeneic DC–tumour cell hybrids [21, 38].