1. ¹Breast Cancer Biology Group, King's College London School of Medicine, Guy's Hospital, London SE1 9RT, UK
2. ²Faculty of Technology, Universitaet Bielefeld, Universitaetsstrasse 25, Bielefeld 33501, Germany

Correspondence: Dr J Burchell, E-mail: joy.burchell@kcl.ac.uk

³Current address: Centenary Institute of Cancer Medicine and Cell Biology, University of Sydney, New South Wales 2042, Australia.

⁴Current address: Theagenion Cancer Hospital, Al. Symeonidi 2, Thessaloniki 54007, Greece.

⁵Current address: Medigene AG, Lochhamer Strasse 9, 81737 Munich, Germany.

Received 9 November 2007; Revised 19 December 2007; Accepted 7 January 2008; Published online 5 February 2008.

Abstract

Dendritic cells (DCs) 'pulsed' with an appropriate antigen may elicit an antitumour immune response in mouse models. However, while attempting to develop a DC immunotherapy protocol for the treatment of breast cancer based on the tumour-associated MUC1 glycoforms, we found that unpulsed DCs can affect tumour growth. Protection from RMA-MUC1 tumour challenge was achieved in C57Bl/6 MUC1 transgenic mice by immunising with syngeneic DCs pulsed with a MUC1 peptide. However, unpulsed DCs gave a similar level of protection, making it impossible to evaluate the effect of immunisation of mice with DCs pulsed with the specific peptide. Balb/C mice could also be protected from tumour challenge by immunisation with unpulsed DCs prior to challenge with murine mammary tumour cells (410.4) or these cells transfected with MUC1 (E3). Protection was achieved with as few as three injections of 50 000 naïve DCs per mouse per week, was not dependent on injection route, and was not specific to cell lines expressing human MUC1. However, the use of Rag2-knockout mice demonstrated that the adaptive immune response was required for tumour rejection. Injection of unpulsed DCs into mice bearing the E3 tumour slowed tumour growth. In vitro, production of IFN- and IL-4 was increased in splenic cells isolated from mice immunised with DCs. Depleting CD4 T cells in vitro partially decreased cytokine production by splenocytes, but CD8 depletion had no effect. This paper shows that naïve syngeneic DCs may induce an antitumour immune response and has implications for DC immunotherapy preclinical and clinical trials.