In this age of promise of new therapies for cancer, immunotherapy is emerging as an exciting treatment option for patients.Vaccines and cytokines are being tested extensively in clinical trials, and strategies using monoclonal antibodies and cell transfer are mediating dramatic regression of tumors in patients with certain malignancies. However, although initially advocated as being more specific for cancer and having fewer side effects than conventional therapies, it is becoming increasingly clear that many immunotherapies can lead to immune reactions against normal tissues. Immunotoxicities resulting from treatment can range from relatively minor conditions, such as skin depigmentation, to severe toxicities against crucial organ systems, such as liver, bowel, and lung. Treatment-related toxicity has correlated with better responses in some cases, and it is probable that serious adverse events from immunemediated reactions will increase in frequency and severity as immunotherapeutic approaches become more effective. This review introduces immunotherapeutic approaches to cancer treatment, provides details of toxicities arising from therapy, and discusses future potential ways to avoid or circumvent these side effects. (Blood. 2011;118(3):499-509)

Toll-like receptor (TLR) agonists can trigger broad inflammatory responses that elicit rapid innate immunity and promote the activities of lymphocytes, which can potentially enhance adoptive immunotherapy in the tumor-bearing setting. In the present study, we found that Polyinosinic:Polycytidylic Acid [Poly(I:C)] and CpG oligodeoxynucleotide 1826 [CpG], agonists for TLR 3 and 9, respectively, potently activated adoptively transferred T cells against a murine model of established melanoma. Intratumoral injection of Poly(I:C) and CpG, combined with systemic transfer of activated pmel-1 T cells, specific for gp10025–33, led to enhanced survival and eradication of 9-day established subcutaneous B16F10 melanomas in a proportion of mice. A series of survival studies in knockout mice supported a key mechanistic pathway, whereby TLR agonists acted via host cells to enhance IFN-γ production by adoptively transferred T cells. IFN-γ, in turn, enhanced the immunogenicity of the B16F10 melanoma line, leading to increased killing by adoptively transferred T cells. Thus, this combination approach counteracted tumor escape from immunotherapy via downregulation of immunogenicity. In conclusion, TLR agonists may represent advanced adjuvants within the setting of adoptive T-cell immunotherapy of cancer and hold promise as a safe means of enhancing this approach within the clinic.

Oncolytic viruses are known to stimulate the antitumor immune response by specifically replicating in tumor cells. This is believed to be an important aspect of the durable responses observed in some patients and the field is rapidly moving toward immunotherapy. As a further means to engage the immune system, we engineered a virus, vesicular stomatitis virus (VSV), to encode the proinflammatory cytokine interferon-γ. We used the 4T1 mammary adenocarcinoma as well as other murine tumor models to characterize immune responses in tumor-bearing animals generated by treatment with our viruses. The interferon-γ-encoding virus demonstrated greater activation of dendritic cells and drove a more profound secretion of proinflammatory cytokines compared to the parental virus. From a therapeutic point of view, the interferon-γ virus slowed tumor growth, minimized lung tumors, and prolonged survival in several murine tumor models. The improved efficacy was lost in immunocompromized animals; hence the mechanism appears to be T-cell-mediated. Taken together, these results demonstrate the ability of oncolytic viruses to act as immune stimulators to drive antitumor immunity as well as their potential for targeted gene therapy.

BackgroundCombination immunotherapies can be effective against subcutaneous tumors in mice but the effect against orthotopic malignant disease is less well characterized. In particular, a combination of three agonist antibodies, termed Tri-mAb, consisting of anti-DR5, anti-CD40 and anti-CD137 has previously been demonstrated to eradicate a large proportion of subcutaneous renal cell carcinoma (Renca) tumors (75% long-term survival), but the effect against orthotopic disease is not known.PurposeTo determine the relative response of orthotopic tumors, we inoculated Renca into the kidney followed by treatment with Tri-mAb.ResultsWe found that orthotopic tumors responded much less to treatment (~13% survival), but a significant improvement in survival was achieved through the addition of IL-2 to the treatment regimen (55% survival). All three agonist antibodies and high dose IL-2, 100,000 IU for up to six doses, were required. CD8+ T cells were also required for optimal anti-tumor responses. Coadministration of IL-2 led to enhanced T cell activity as demonstrated by an increased frequency of IFN-gamma-producing T cells in tumor-draining lymph nodes, which may have contributed to the observed improvement of therapy against kidney tumors.ImplicationsResponses of subcutaneous tumors to immunotherapy do not necessarily reflect how orthotopic tumors respond. The use of combination immunotherapy stimulating multiple facets of immunity and including cytokine support for T cells can induce effective anti-tumor responses against orthotopic and metastatic tumors.