Local Administration of PF-3512676 CpG-B Instigates Tumor-Specific CD8+ T-Cell Reactivity in Melanoma Patients

Abstract

Purpose: Impaired immune effector functions in the melanoma sentinel lymph node (SLN) may allow for early metastatic events. Local administration of PF-3512676 (formerly known as CpG 7909) has shown immunostimulatory effects of both dendritic cell and T-cell subsets in the melanoma SLN. Here, we set out to ascertain whether these PF-3512676-induced immunostimulatory effects translate into higher frequencies of melanoma-specific CD8 + Tcells. Experimental Design: Twenty-four stage I to III melanoma patients were randomized to preoperative local administration of either PF-3512676 or saline. CD8 + T cells from SLN and peripheral blood were tested for reactivity by IFN-g ELISPOT assay against several HLA-A1/A2/ A3-restricted epitopes derived from various melanoma-associated antigens (MAA) in 21 of 24 enrolled patients. Frequencies of natural killer (NK) cells and frequencies and maturation state of dendritic cell subsets in the SLN were determined by flow cytometry. Results: Melanoma-specific CD8 + T-cell response rates against >1MAA epitope in the SLN were 0 of 11 for the saline group versus 5 of 10 for the PF-3512676-administered group (P = 0.012).Of these 5 responding patients, 4 also had a measurable response to >1 MAA epitope in the blood. Increased frequencies in the SLN of both MAA-specific CD8 + T cells and NK cells correlated to CpG-induced plasmacytoid dendritic cell maturation. Conclusions: These data show an increase in melanoma-specific CD8 + T-cell frequencies as well as an increased effector NK cell rate after a single dose of PF-3512676 and thus support the utility of local PF-3512676 administration as adjuvant treatment in early-stage melanoma to try and halt metastatic spread.

Skin Inflammation Is Not Sufficient to Break Tolerance Induced against a Novel Antigen

“…Furthermore, neither treatment with polyI:polyC nor with Imiquimod could break established tolerance in K5-Ova/K5-CreER mice (data not shown). This was surprising because we and others have previously shown that Imiquimod and CpG are potent immune stimulators capable of inducing efficient immune responses against melanoma in the skin (45)(46)(47)(48). We speculated that this lack of immune stimulation was due to weak cross-presentation, as indicated by the poor Ag presentation in skin draining LN of TXtreated 26K5-Ova/K5-CreER mice in vitro.…”

Plasmacytoid Dendritic Cells Support Melanoma Progression by Promoting Th2 and Regulatory Immunity through OX40L and ICOSL

“…The intact ability of melanoma-infiltrating pDCs to respond to TLRL stimulation is consistent with the potent antitumor responses following imiquimod (TLR7-L) therapy in patients with melanoma (46)(47)(48) or after CpG (TLR9-L; refs. 14, 15) treatment, both of which involved the recruitment and activation of pDCs (16,17,(46)(47)(48). Despite the role of pDCs on tumor progression under steady state conditions, remobilization of pDCs using TLR agonists represents a promising means to achieve melanoma tumor control by reversing the functional hijack of pDCs.…”

“…Indeed, pDCs play a pivotal role in antitumor immunity through their ability to process and cross-present tumor antigens to T cells (8), and subsequently induce adaptive immune responses (9). In the context of melanoma, pDCs have been shown to prime functional immune responses (9)(10)(11), display direct cytotoxic activity towards tumor cells through TRAIL expression (12) or lysozyme secretion (13), or once activated, potentially achieve melanoma tumor control through efficient priming of antitumor responses (14)(15)(16)(17). Infiltration of tumors by pDCs has been found in many types of cancers, yet associated with poor prognosis, especially in ovarian (18) and breast cancer (19).…”

Characterization of four conventional dendritic cell subsets in human skin-draining lymph nodes in relation to T-cell activation

“…16,17 We have used this methodology to study the in vivo effects of immune modulators such as the CpG-B TLR9-ligand PF-3512676 and GM-CSF on DC and T-cell subsets in the SLN. [18][19][20][21] In the context of 3 separate clinical phase 2 trials, we have collected a sizeable number of SLNs from untreated or saline placeboadministered melanoma patients, from which phenotypic DC data were obtained through multiparameter flow cytometric analysis and of which viable cells were cryopreserved for further functional analysis. From these, we have selected tumor-negative SLNs from Stage I-II melanoma patients, which were removed 1-2 months after excision of the primary melanoma, to perform an in-depth analysis of cDC subsets in steadystate skin-draining LNs.…”