strategies of immunotherapy both as a preventative treatment and a means to modify tumor growth. Gene transfer prior to surgery as neoadjuvant therapy has ...
CANCER-APOPTOSIS AND SUICIDE cells. In a wide range of solid tumours, over-expression of CD137L has been shown to produce tumour immunity. This was at least partly due to the stimulation of CD8+ CTL. Costimulation by other known interactions was not unconditionally necessary. Antitumour effects were even increased when immunotherapy with Interleukin-12 was additionally employed, either systemically or locally. Yet, there is rare data on the effect of CD137L immunotherapy in hematological malignancies. Here, we present data obtained in a murine plasmocytoma model to evaluate the effect of CD137L and IL-12, either as mono- or combination therapy. Methods CD137L and IL-12 cDNA were cloned into a mammalian expression vector (pCDNA3.1) bearing a neomycin selection marker, respectively. Electroporation was used to transfect the murine plasmocytoma cell line MPC11. Positive cell clones were cultured in G418 containing media. CD137L expression was determined by FACS analysis. IL-12 secretion was detected with ELISA. A lethal tumour dose (2.5 x 105 cells) was subcutaneously inoculated in Balb/c mice (n=8). Either IL-12 secreting cells, CD137L expressing cells, or a mixture was administered, respectively. Tumour volume and diameter were frequently determined. Tumour specimens were obtained for histological examination. Surviving animals were challenged with an additional lethal dose of wildtype tumour cells. Results 2/8 (25%) animals receiving IL-12 secreting tumour cells died. In 6/8 (75%) animals treated with CD137L expressing tumour cells, a transient tumour nodule formed: Regression was observed in all animals. In the combination therapy group, 1/8 (12.5%) animals developed tumour, here also regression was observed. All animals survived. Rechallenge of wildtype tumour was rejected by all animals in the CD137L group and remaining animals in the IL-12 group. On the contrary, 2/8 (25%) animals in the combination therapy group died. Histological analysis is currently performed and will be presented at the meeting. Conclusion As in a variety of solid tumours, CD137L is capable of inducing an efficient and long-lasting anti-tumour immunity in the Murine Plasmocytoma Model MPC11. Transient tumour growth was observed, suggesting a delayed local tumor rejection. Examination of tumor specimens may reveal anti-tumor effector mechanisms induced by CD137L expressing tumour cells. Differences compared to tumors induced by IL-12 secreting cells may explain less effective IL-12 mono- and CD137L/IL-12 combination immunotherapy.
285. Anti-Tumor Immune Responses Following Neoadjuvant Immunotherapy with a Recombinant Adenovirus Expressing HSP72 to Rodent Tumors James A. Krewet,1 Si-Yi Chen,2 Maulik R. Shah.1 1 Medical Genetics, Saint Louis University, Saint Louis, MO; 2 Molecular and Human Genetics, Baylor College of Medicine, Houston, TX. Gene modification of tumor cells is commonly utilized in various strategies of immunotherapy both as a preventative treatment and a means to modify tumor growth. Gene transfer prior to surgery as neoadjuvant therapy has not been studied systematically. We addressed if direct intra-tumoral injection of a recombinant adenovirus expressing the immunomodulatory molecule heat shock protein 72 (ADHSP72) administered prior to surgery could result in sustainable anti-tumor immune responses capable of affecting tumor progression and survival in a number of different murine and rat tumor models. Using intradermal murine models of melanoma (B16), colorectal carcinoma (CT26), prostate cancer (TrampC2) and a rat model of glioblastoma (9L), tumors were treated with vehicle or GFP expressing adenovirus (ADGFP) or ADHSP72. Tumors were surgically excised after 72 hours. Approximately 25S112
50% of animals in the ADHSP72 treatment group but not in control groups showed sustained resistance to subsequent tumor challenge. Tumor resistance was associated with development of anti-tumor cellular immune responses. Efficacy of ADHSP72 as neoadjuvant therapy was dependent on the size of the initial tumor with greater likelihood of immune response generation and tumor resistance associated with smaller tumor size at initial treatment. ADHSP72 neoadjuvant therapy resulted in prolonged survival of animals upon re-challenge with autologous tumor cells compared to ADGFP or vehicle control groups. To study the effects on tumor progression of distant metastases, a single tumor focus of animals with multifocal intradermal tumors was treated. ADHSP72 diminished progression of the secondary tumor focus and prolonged survival but only when the secondary tumor focus was
