Bortezomib augments lymphocyte stimulatory cytokine signaling in the tumor microenvironment to sustain CD8+T cell antitumor function

Abstract

Tumor-induced immune tolerance poses a major challenge for therapeutic interventions aimed to manage cancer. We explored approaches to overcome T-cell suppression in murine breast and kidney adenocarcinomas, and lung fibrosarcoma expressing immunogenic antigens. We observed that treatment with a reversible proteasome inhibitor bortezomib (1 mg/kg body weight) in tumor-bearing mice significantly enhanced the expression of lymphocyte-stimulatory cytokines IL-2, IL-12, and IL-15. Notably, bortezomib administration reduced pulmonary nodules of mammary adenocarcinoma 4T1.2 expressing hemagglutinin (HA) model antigen (4T1HA) in mice. Neutralization of IL-12 and IL-15 cytokines with a regimen of blocking antibodies pre- and post-adoptive transfer of low-avidity HA518-526-specific CD8+T-cells following intravenous injection of 4T1HA cells increased the number of pulmonary tumor nodules. This neutralization effect was counteracted by the tumor metastasis-suppressing action of bortezomib treatments. In bortezomib-treated 4T1HA tumor-bearing mice, CD4+T-cells showed increased IL-2 production, CD11c+ dendritic cells showed increased IL-12 and IL-15 production, and HA-specific activated CD8+T-cells showed enhanced expression of IFNγ, granzyme-B and transcription factor eomesodermin. We also noted a trend of increased expression of IL-2, IL-12 and IL-15 receptors as well as increased phosphorylation of STAT5 in tumor-infiltrating CD8+T-cells following bortezomib treatment. Furthermore, bortezomib-treated CD8+T-cells showed increased phosphorylation of mitogen-activated protein kinase p38, and Akt, which was abrogated by phosphatidylinositide 3-kinase (PI3K) inhibitor. These data support the therapeutic potential of bortezomib in conjunction with other immunotherapies to augment the strength of convergent signals from CD8+T-cell signaling molecules including TCR, cytokine receptors and downstream PI3K/Akt/STAT5 pathways to sustain CD8+T-cell effector function in the tumor microenvironment.

Enhanced Dendritic Cell Development Through Long-Term Proteasome Inhibition

“…of MM. Coupled to previous observations that BTZ treatment can break detrimental clusters between leukemic tumor cells and immuno-compromised DC [10], induces immunogenic cell death [8,55] and promotes effector molecule expression and effector functions of CD8 + tumor-reactive T cells and NK cells [18,[56][57][58], our finding of enhanced functional human DC development and maturation argues in favour of applying BTZ in combination with immunotherapy for cancer treatment.…”

“…As such, these studies point to the potential utility of BTZ as an immune-regulatory therapeutic agent for the treatment of chronic inflammatory and autoimmune disorders [35]. However, these data are in striking contrast with recent reports of the in vivo effects of BTZ on DC development and maturation [17,18]. Chang et al, showed increased DC maturation and tumor infiltration upon BTZ treatment, resulting in effective antitumor T cell-mediated immunity [17].…”

“…Chang et al, showed increased DC maturation and tumor infiltration upon BTZ treatment, resulting in effective antitumor T cell-mediated immunity [17]. Pellom et al, showed increased IL-12 and IL-15 production by CD11c+ DC and enhanced tumor reactivity upon BTZ treatment in a 4T1 breast cancer mouse model cell line [18]. These apparently contradictory results may be due to differential effects on inflammatory vs. steady-state DC differentiation as well as on short-term (<7 days) vs. more long-term (>21 days) effects of BTZ exposure.…”

“…Similarly, in a 4T1 mammary carcinoma mouse model, BTZ treatment increased IL-12 and IL-15 production by CD11c + DC as well as IL-2 production by CD4 + T cells and granzyme-B and interferon-γ production by tumor-antigen specific CD8 + effector T cells, resulting in reduced metastatic spread. This reduction in metastatic spread was dependent on IL-12 and IL-15, since neutralization of these cytokines could negate the beneficial effects of BTZ therapy in this model [18]. Thus far, studies have concentrated on short-term exposure (5-7 days) to the drug.…”

Bortezomib improves adoptive carbonic anhydrase�IX‑specific chimeric antigen receptor‑modified NK92 cell therapy in mouse models of human renal cell carcinoma

“…Bortezomib also affected cytokine production in the tumor microenvironment, thereby polarizing the cytokine milieu in favor of antitumor immunity. Therefore, it is possible that bortezomib enhances the antitumor immunity of immune effector cells by overcoming tumor-induced suppression of numerous immune regulatory networks (62). However, in the present study, whether bortezomib enhanced the antitumor efficacy of CAIX-CAR-NK92 cells by these mechanisms requires further evaluation.…”