Recent Progress in the Synergistic Combination of Nanoparticle-Mediated Hyperthermia and Immunotherapy for Treatment of Cancer

Abstract

Immunotherapy has demonstrated great clinical success in certain cancers, driven primarily by immune checkpoint blockade and adoptive cell therapies. Immunotherapy can elicit strong, durable responses in some patients, but others do not respond, and to date immunotherapy has demonstrated success in only a limited number of cancers. To address this limitation, combinatorial approaches with chemo- and radiotherapy have been applied in the clinic. Extensive preclinical evidence suggests that hyperthermia therapy (HT) has considerable potential to augment immunotherapy with minimal toxicity. This progress report will provide a brief overview of immunotherapy and HT approaches and highlight recent progress in the application of nanoparticle (NP)-based HT in combination with immunotherapy. NPs allow for tumor-specific targeting of deep tissue tumors while potentially providing more even heating. NP-based HT increases tumor immunogenicity and tumor permeability, which improves immune cell infiltration and creates an environment more responsive to immunotherapy, particularly in solid tumors.

Keywords: cancer; immunotherapy; magnetic hyperthermia therapy; nanoparticles; photothermal therapy.

Figure 1.

Immune-regulation in the TME is dictated by checkpoints located on immune cell membranes. The check point receptors on T cells interact with their ligands on the surface of APCs or tumor cells, and provide either stimulatory (green) or inhibitory (red) signals between the two cells. Checkpoint blockade-based immunotherapy acts by blocking the inhibitory axes. APC, antigen-presenting cell; Treg, regulatory T cell; TAM, tumor-associated macrophage; NK, natural killer.

Figure 2.

The synergistic effects of mild NP-based HT and immunotherapy in tumors. a) Systemically administered NPs localize to the primary tumor and metastatic cells. b) The NPs release siRNA against PD-L1 (siPD-L1), which inhibits translation of PD-L1 via the RNA-silencing complex (RISC). Irradiation with an external AMF or NIR light initiates an HT induced immune response that increases the release of exosomes containing TSAs, and expression of HSPs and MHC receptors. Exosome released TSAs and HSP-TSA complexes activate APCs which release NK cell activating IFN-α, and are trafficked to the lymph nodes where they activate T cells. c) Activated T cells traffic to the primary and metastatic tumors, initiating TCR mediated killing of tumor cells. Gene silencing by siPD-L1 creates a positive feedback loop which allows an uninhibited immune response, resulting in primary tumor cell cytotoxicity, abscopal effects, and immune memory.

Figure 3.

Combined photothermal ablation and adoptive transfer of CAR T cells promotes T cell infiltration, mediates tumor hypoxia, and inhibits the growth of the human melanoma. a) Schematic illustration showing the effects of the mild heating of the tumor that causes enhanced infiltration and activation of adoptive transfer CAR.CSPG4⁺ T cells. b) In vivo Bioluminescence quantification of CAR.CSPG4⁺ T cells detected in the tumor with or without photothermal ablation. Data are presented as mean ± s.e.m. (n = 3). c) Representative hypoxia and HIF1-α immunofluorescence staining of the tumors after photothermal therapy (Scale bar: 50 μm). d) Average tumor growth kinetics in different groups. Day 0 indicates the day in which treatment was initiated. Data are presented as mean ± s.e.m. (n = 6). e) Murine IL-6 levels detected in the tumors 7 days after the indicated treatments. Data are presented as mean ± s.e.m. (n = 8). f,g) Human IL-2 and IFN-γ levels detected in the tumor 7 days after the indicated treatments. Data are presented as mean ± s.e.m. (n = 7). Statistical significance was calculated via one-way ANOVA with a Tukey post hoc test. P value: *P < 0.05, **P < 0.01, and ***P < 0.001. Adapted with permission.^[198] 2019, Wiley.

Figure 4.

In vivo immunostimulatory and anti-tumor effects of MINPS-based PTT. a) Schematic illustration of the synthetic process for the MINPs (CpG@PLGA-PLL-mPEG/SPIO). b) DC maturation levels in the primary tumor (1st) cells collected on day 3 after the aforementioned treatments by flow cytometry. *p<0.05, **p<0.001: MINPs + magnetic field (MF) + Laser compared to control groups. c) The secretion levels of TNF-α and IL-6 by ELISA assay in the sera from the mice on day 3 after the aforementioned treatments on the primary tumors (1st), respectively. *p<0.05, **p<0.001: TNF-α level in group of MINPs + MF + Laser compared to control group. #p<0.05, ##p<0.001: IL-6 level in group of MINPs + MF + Laser compared to control group. d) Immunofluorescence images of effector CD8+ T cells and IFN-γ in the distant tumors (2nd) on day 7 after different treatments on the primary tumors (1st). The tumor specimens were sectioned and immunostained with anti-CD8-FITC (green) and anti-IFN-γ-Cy3 (red), respectively. e) Growth curves of the primary tumors (1st) and f) the distant tumors (2nd) on mice in different groups after the aforementioned treatments. **p<0.001 compared to control group. L = NIR light. Adapted with permission.^[209] 2019, Elsevier.

Figure 5.

GOP@aPD1-based PTT delivers aPD1 to tumors and sensitizes tumors to PD-1 blockade immunotherapy for the treatment of melanoma. a) The compositions of GOP@aPD1 NPs (left). After laser irradiation, GOP@aPD1 NPs dissociate, releasing aPD1 and iron oxide nanoparticles (right). (b-d) Cytokine levels in sera from mice isolated at 24, 72 and 168 h after different treatments (control, PTT and GOP@aPD1- based PTT). The data are shown as the mean ± SD, n=3 per group. e) The relative tumor growth curves during the various treatments over the 14-day study period (mean ± SD, n=5, **p < .01). f) Survival curves of the treated and control mice (*p < .05). g) Representative CLSM images of the residual tumors in G1 (upper) or G8 (median; under) showed CD3+ T cell, CD4+ T cell and CD8+ T cell infiltration after immunofluorescence staining. G1 = Saline control, G2 = Free anti-PD-1, G3 = PTT only, G4 = Free anti-PD-1 + PTT, G5 = iron oxide loaded NP + PTT, G6 = anti-PE-1 loaded NP + PTT, G7 = iron oxide and anti-PD-1 loaded NP, G8 = iron oxide and anti-PD-1 loaded NP + PTT. Adapted with permission.^[173] 2019, Elsevier.