PD-L1-Independent Mechanisms Control the Resistance of Melanoma to CD4 T Cell Adoptive Immunotherapy.

Immunotherapy is becoming the standard of care for melanoma. However, resistance to therapy is a major problem. Previously, we showed that tumor-specific, cytotoxic CD4 T cells from tyrosinase-related protein 1 transgenic mice could overcome secondary resistance to recurring melanoma when anti-programmed cell death 1 ligand (PD-L1) checkpoint blockade was combined with either anti-lymphocyte-activated gene 3 (LAG-3) Abs or depletion of tumor-specific regulatory T (T) cells.

A role for pre-mNK cells in tumor progression.

The innate and adaptive immune systems have evolved together to fight infection and cancerous tissues. The innate immune system emerges first with the adaptive immune system following, both ostensibly being bridged by dendritic cells (DC). Recently cells have emerged that possess characteristics of both innate and adaptive immune cell qualities, termed interferon-producing killer dendritic cells (IKDCs).

Depletion of B220NK1.1 cells enhances the rejection of established melanoma by tumor-specific CD4 T cells.

Five-year survival rates for patients diagnosed with metastatic melanoma are less than 5%. Adoptive cell transfer (ACT) has achieved an objective response of 50% by Response Evaluation Criteria in Solid Tumors (RECIST) in this patient population. For ACT to be maximally effective, the host must first be lymphodepleted.

Restoring immune function of tumor-specific CD4+ T cells during recurrence of melanoma.

Recurrent solid malignancies are often refractory to standard therapies. Although adoptive T cell transfer may benefit select individuals, the majority of patients succumb to their disease. To address this important clinical dilemma, we developed a mouse melanoma model in which initial regression of advanced disease was followed by tumor recurrence.

Naive tumor-specific CD4(+) T cells differentiated in vivo eradicate established melanoma.

In vitro differentiated CD8(+) T cells have been the primary focus of immunotherapy of cancer with little focus on CD4(+) T cells. Immunotherapy involving in vitro differentiated T cells given after lymphodepleting regimens significantly augments antitumor immunity in animals and human patients with cancer. However, the mechanisms by which lymphopenia augments adoptive cell therapy and the means of properly differentiating T cells in vitro are still emerging.

CD4+CD25+ T regulatory cells, immunotherapy of cancer, and interleukin-2.

CD4+CD25+ T regulatory (Treg) cells control immunologic tolerance to self-antigens and play a role in suppressing antitumor immune responses, but the mechanism of suppression in vivo remains uncertain. Recently, signaling through the high-affinity interleukin-2 (IL-2) receptor has been shown to be critical for Treg cell differentiation and survival in vivo. Mice deficient in IL-2 or its receptor (CD25 or CD122) or deficient in downstream signaling molecules, including JAK-3 and STAT-5, do not develop a stable population of Treg cells and subsequently acquire lymphoproliferative disease and autoimmunity.

Do CD4+ CD25+ immunoregulatory T cells hinder tumor immunotherapy?

After years of banishment from mainstream immunology, the notion that one subset of T cells can exert regulatory effects on other T lymphocytes is back in fashion. Recent work in knockout and transgenic mice has begun to bring molecular definition to our understanding of immunoregulatory CD4+CD25+ T cells (Treg/Th3/Tr1). The identification of the glucocorticoid-induced tumor necrosis factor receptor family-related gene (GITR, also known as TNFRSF18) expressed on T regulatory cells might afford new therapeutic opportunities.