Abstract 5618: Arming the melanoma sentinel lymph node against tumor spread: The effects of local administration of combined low-dose CpG-B PF-3512676 and GM-CSF

Abstract

Abstract The sentinel lymph node (SLN) procedure has proven a useful prognostic tool for the assessment of melanoma relapse and mortality risk, but is also of great value for the assessment of immunological interventions. Since early melanoma development is accompanied by a suppressed immune state of the SLN, there is a strong rationale for therapeutic immune modulation of the SLN in order to strengthen local as well as systemic cell-mediated anti-tumor immunity. Previous Phase II studies showed promising immunostimulatory effects on the melanoma SLN of Granulocyte/Macrophage-Colony Stimulating Factor (GM-CSF) and the CpG-B oligodeoxynucleotide PF-3512676. The present 3-arm Phase II study was designed to determine the effects of combined low-dose GM-CSF+CpG-B administration. Stage I-III melanoma patients (n=28) were randomized to receive i.d. injections around the primary tumor excision site of saline, CpG-B alone (1 mg), or CpG-B combined with GM-CSF (100 μg), 7 and 2 days prior to surgical excision of the SLN. Flowcytometric DC analyses revealed significantly increased maturation of all identifiable cDC and pDC SLN subsets upon administration of CpG-B with or without GM-CSF, but remarkably, the combination resulted in significantly higher levels of co-stimulatory molecules on both cDC and pDC. In addition, a significant CpG-related increase in frequencies of CD1a−CD11chiCD14+/− cDC subsets was observed in the SLN, possibly resulting from DC and/or monocyte mobilisation from blood. Indeed, increased activation of pro-inflammatory 6-sulfo LacNac+slanDC, monocytes, and pDC was observed in peripheral blood upon administration of CpG-B alone, and additionally of CD1c+ cDC when combined with GM-CSF. In the case of slanDC this activation was accompanied by significantly reduced frequencies. Peripheral blood rates of CD14+DRlo myeloid suppressors remained unchanged after saline or combined CpG and GM-CSF administration, but significantly decreased after administration of CpG-B alone. T cell analyses revealed a CpG-related increase in CTLA-4 and FoxP3 levels on Tregs in SLN, without changes in their actual rates. Nevertheless, higher intracellular Th1 cytokine levels were detected in ex vivo expanded T cells of CpG-administered patients than of patients receiving saline or CpG-B+GM-CSF. In keeping with this, also higher frequencies were found in SLN of MAA-specific CD8+ T cells in low dose CpG-B administered patients (n=4) than in saline controls (n=5), as determined by tetramer binding and cytokine release. We conclude that the imunomodulatory effects observed in melanoma SLN upon local administration of combined low-dose GM-CSF and CpG-B are mostly attributable to CpG-B and that they are consistent with the induction of protective cell-mediated anti-tumor immunity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5618.