Activation of CD1d-restricted natural killer T cells can inhibit cancer cell proliferation during chemotherapy by promoting the immune responses in murine mesothelioma

Abstract

We studied the impact of natural killer T (NKT) cell activation by alpha-galactocysylceramide (α-GalCer, α-GC) on cancer cell repopulation during chemotherapy in murine mesothelioma. The number of NKT cells was found to be increased during the development of murine mesothelioma. NKT cells specifically recognize α-GC through CD1d resulting in their activation and expansion. Tumor-bearing mice were treated with chemotherapy once weekly, and α-GC was followed after each cycle of chemotherapy. Anti-tumor effect was evaluated on wild-type (WT) and CD1d knockout (CD1dKO) mice. Cancer cell proliferation and apoptosis were evaluated by Ki67 and TUNEL immunohistochemistry. CD4(+) and CD8(+) T cell proportion and activation in tumor, spleen, draining lymph node and peripheral blood were determined by flow cytometry, and gene expression of activated T cell-related cytokines was quantified by reverse transcription PCR. NKT cells were identified by CD1d-α-GC-tetramer staining. In WT mice, tumor growth delay was achieved by cisplatin (Cis), and this effect was improved in combination with α-GC, but α-GC alone had little effect. Cancer cell proliferation during chemotherapy was significantly inhibited by α-GC, while cancer cell death was significantly upregulated. α-GC following chemotherapy resulted in NKT cell expansion and an increase of interferon-γ production in the draining lymph node, blood and spleen. Gene expression of immune-associated cytokines was upregulated. Strikingly, the percentage of inducible T cell co-stimulator(+)CD4 T cells, Th17/Tc17 cells increased in splenocytes. In CD1d KO mice, however, Cis alone was less effective and Cis + α-GC provided no additional benefit over Cis alone. α-GC alone had minimal effect in both mice. NKT activation between cycles of chemotherapy could improve the outcome of mesothelioma treatment.

Natural Killer T-cell Immunotherapy in Combination with Chemotherapy-Induced Immunogenic Cell Death Targets Metastatic Breast Cancer

“…Few studies have examined NKT-cell activation in combination with chemotherapy. In a mouse model of mesothelioma, a-GalCer treatment improved cisplatin-mediated protection (31). Similarly, a-GalCer plus 5-fluorouracil enhanced protection from MC38 colorectal cancer metastasis over a-GalCer or 5-fluorouracil treatments alone (32).…”

“…Tumor cells treated with chemotherapeutics exhibit increased susceptibility to killing by NKT cells in vitro (15,30). Similarly, NKT-cell activation in combination with either cisplatin (31) or 5-fluorouracil (32) exhibited promising results in murine models of mesothelioma and colorectal cancer metastasis, respectively. However, as neither of these agents induces ICD (22), the potential for combining ICD-inducing chemotherapies with NKT-cell activation remains undefined.…”

Radio-immunotherapy and chemo-immunotherapy as a novel treatment paradigm in malignant pleural mesothelioma

“…Immune modulation approaches are becoming promising strategies to inhibit cancer cell repopulation during courses of chemotherapy (41,42). As previously demonstrated, CD4 + CD25 + Tregs can promote tumor growth.…”

“…α-GC alone had minimal effect in both mice. In conclusion, NKT activation between cycles of chemotherapy could improve the outcome of mesothelioma treatment (42).…”

“…Nevertheless, cell killing induced by cyclophosphamide combined with cisplatin was due to cytotoxicity rather than specific immune response. Treg depletion between cycles of chemotherapy could improve the outcome of mesothelioma (41,42). Cancer immunotherapy has shown promising results when combined with chemotherapy.…”