Tumor antigen-specific CD8 T cells infiltrating the tumor express high levels of PD-1 and are functionally impaired. Blood. 2009;114:1537-1544. [PMID: 19423728 DOI: 10.1182/blood-2008-12-195792]

Depleting syndecan-4+ T lymphocytes using toxin-bearing dendritic cell-associated heparan sulfate proteoglycan-dependent integrin ligand: a new opportunity for treating activated T cell-driven disease

Because syndecan-4 (SD-4) is expressed by some (but not all) T cells following activation and serves as the exclusive ligand of dendritic cell-associated heparan sulfate proteoglycan-dependent integrin ligand (DC-HIL), we envisioned the DC-HIL/SD-4 pathway to be a therapeutic target for conditions mediated by selectively activated T cells. We conjugated soluble DC-HIL receptor with the toxin saporin (SAP; DC-HIL-SAP) and showed it to bind activated (but not resting) T cells and become internalized by and deplete SD-4(+) T cells. In hapten-sensitized mice, DC-HIL-SAP injected i.v. prior to hapten challenge led to markedly suppressed contact hypersensitivity responses that lasted 3 wk and were restricted to the hapten to which the mice were originally sensitized. Such suppression was not observed when DC-HIL-SAP was applied during sensitization. Moreover, the same infusion of DC-HIL-SAP produced almost complete disappearance of SD-4(+) cells in haptenated skin and a 40% reduction of such cells within draining lymph nodes. Our results provide a strong rationale for exploring use of toxin-conjugated DC-HIL to treat activated T cell-driven disease in humans.

Chemotherapy rescues tumor-driven aberrant CD4+ T-cell differentiation and restores an activated polyfunctional helper phenotype

The functional development of tumor-specific CD4(+) T cells has a critical impact on the outcome of antitumor immune responses. Adoptive immunotherapy involving tumor-specific CD4(+) T cells has shown encouraging clinical benefits in some cancer patients. To mount an effective antitumor immunity, it is desirable to elicit activated type 1 T helper cells. Here, we report that type 1 T helper cell-like effector cells that arose in tumor-bearing hosts progressively expressed programmed death 1 during tumor growth. The programmed death 1(hi) effector cells displayed a dysfunctional phenotype, characterized by selective down-regulation of interleukin-7 receptor, heightened apoptosis, and poor antitumor efficacy. This tumor-driven aberrant T-cell response could be prevented by a single dose of the widely used chemotherapy agent cyclophosphamide. We show that chemotherapy conditioned the host environment, creating a transient window for optimal effector differentiation for adoptively transferred CD4(+) T cells. This robust effector differentiation, which was antigen-driven and mechanistically dependent on an intact host response to type I interferon, gave rise to activated polyfunctional T helper cells with high interleukin-7 receptor, rapid clonal expansion, and potent antitumor activity against established B-cell lymphomas. We hypothesize that prevention of tumor-induced effector cell dysfunction is a major mechanism contributing to the efficacy of combined chemoimmunotherapy.

Immunobiology of cancer therapies targeting CD137 and B7-H1/PD-1 cosignal pathways

Cancer immunotherapy is finally entering a new era with manipulation of cosignaling pathways as a therapeutic approach, for which the principle was proved nearly two decades ago. In addition to CTLA-4, CD137 and B7-H1/PD-1 pathways are two new targets in the stage. CD137 pathway is costimulatory and its agonistic antibody delivers potent signal to drive T cell growth and activation. On the other hand, blockade of B7-H1/PD-1 pathway with antagonistic antibody has shown to protect ongoing T cell responses from impairment by immune evasion mechanism in cancer microenvironment. With these tools in hand, a mechanism-based design of combined immunotherapy with high efficacy is becoming a reality.

Blocking PD-1 in cancer immunotherapy

The PD-1 pathway is emerging as an important tumor-evasion mechanism. In this issue of Blood, 3 independent groups report that PD-1 is highly expressed by tumor-specific cytotoxic T lymphocytes in hematologic and nonhematologic malignancies, and is associated with impaired T-cell function.

Galectin-9 increases Tim-3+ dendritic cells and CD8+ T cells and enhances antitumor immunity via galectin-9-Tim-3 interactions

A Tim-3 ligand, galectin-9 (Gal-9), modulates various functions of innate and adaptive immune responses. In this study, we demonstrate that Gal-9 prolongs the survival of Meth-A tumor-bearing mice in a dose- and time-dependent manner. Although Gal-9 did not prolong the survival of tumor-bearing nude mice, transfer of naive spleen cells restored a prolonged Gal-9-induced survival in nude mice, indicating possible involvement of T cell-mediated immune responses in Gal-9-mediated antitumor activity. Gal-9 administration increased the number of IFN-gamma-producing Tim-3(+) CD8(+) T cells with enhanced granzyme B and perforin expression, although it induced CD4(+) T cell apoptosis. It simultaneously increased the number of Tim-3(+)CD86(+) mature dendritic cells (DCs) in vivo and in vitro. Coculture of CD8(+) T cells with DCs from Gal-9-treated mice increased the number of IFN-gamma producing cells and IFN-gamma production. Depletion of Tim-3(+) DCs from DCs of Gal-9-treated tumor-bearing mice decreased the number of IFN-gamma-producing CD8(+) T cells. Such DC activity was significantly abrogated by Tim-3-Ig, suggesting that Gal-9 potentiates CD8(+) T cell-mediated antitumor immunity via Gal-9-Tim-3 interactions between DCs and CD8(+) T cells.