BACKGROUND: Therapy-induced senescent cancer and stromal cells secrete cytokines and growth factors to promote tumor progression. Therefore, senescent cells may be novel targets for tumor treatment. Near-infrared photoimmunotherapy (NIR-PIT) is a highly tumor-selective therapy that employs conjugates of a molecular-targeting antibody and photoabsorber. Thus, NIR-PIT has the potential to be applied as a novel senolytic therapy. This study aims to investigate the efficacy of NIR-PIT treatment on senescent cancer and stromal cells.
METHODS: Two cancer cell lines (human lung adenocarcinoma A549 cells and human pancreatic cancer MIA PaCa-2 cells) and two normal cell lines (mouse fibroblast transfected with human epidermal growth factor receptor 2 [HER2] cells and human fibroblast WI38 cells) were used. The cytotoxicity of NIR-PIT was evaluated using anti-epidermal growth factor receptor (EGFR) antibody panitumumab and anti-HER2 antibody transtuzumab.
RESULTS: Cellular senescence was induced in A549 and MIA PaCa-2 cells by 10 Gy γ-irradiation. The up-regulation of cellular senescence markers and characteristic morphological changes in senescent cells, including enlargement, flattening, and multinucleation, were observed in cancer cells after 5 days of γ-irradiation. Then, NIR-PIT targeting EGFR was performed on these senescent cancer cells. The NIR-PIT induced morphological changes, including bleb formation, swelling, and the inflow of extracellular fluid, and induced a significant decrease in cellular viability. These results suggested that NIR-PIT may induce cytotoxicity using the same mechanism in senescent cancer cells. In addition, similar morphological changes were also induced in radiation-induced senescent 3T3-HER2 fibroblasts by NIR-PIT targeting human epidermal growth factor receptor 2.
CONCLUSIONS: NIR-PIT eliminates both senescent cancer and stromal cells in vitro suggesting it may be a novel strategy for tumor treatment.

Near-infrared photoimmunotherapy (NIR-PIT) is a new type of cancer therapy that employs antibody-IRDye700DX conjugates (AbPCs) and near-infrared (NIR) light at a wavelength of 689 nm, the excitation wavelength of IR700. Administered intravenously, injected AbPCs bind specifically to cells expressing the target antigen, whereupon NIR light exposure causes rapid, selective killing. This process induces an anticancer T cell response, leading to sustained anticancer host immune response. Programmed cell death ligand-1 (PD-L1) is a major inhibitory immune checkpoint molecule expressed in various cancers. In this study, we first assessed the efficacy of PD-L1-targeted NIR-PIT (αPD-L1-PIT) in immune-competent tumor mouse models. αPD-L1-PIT showed a significant therapeutic effect on the tumor models with high PD-L1 expression. Furthermore, αPD-L1-PIT induced an abscopal effect on distant tumors and long-term immunological memory. In contrast, αPD-L1-PIT was not as effective for tumor models with low PD-L1 expression. To improve the efficacy of PD-L1-targeted NIR-PIT, PEGylated interferon-gamma (IFNγ) was administered with αPD-L1-PIT. The combination therapy improved the treatment efficacy by increasing PD-L1 expression leading to more efficient cell killing by αPD-L1-PIT. Furthermore, the PEGylated IFNγ led to a CD8+ T cell-dominant tumor microenvironment (TME) with an enhanced anticancer T cell response after αPD-L1-PIT. As a result, even so-called cold tumors exhibited complete responses after αPD-L1-PIT. Thus, combination therapy of PEGylated IFNγ and PD-L1-targeted NIR-PIT has the potential to be an important future strategy for cancer immunotherapy.

BACKGROUND: Near-infrared photoimmunotherapy (NIR-PIT) for head and neck cancer is a recently developed therapy. However, there is limited data on patients receiving NIR-PIT in real clinical settings.
METHODS: Seven NIR-PIT sessions were administered to five patients with head and neck squamous cell carcinoma (HNSCC). Serum damage-associated molecular patterns (DAMPs) (HMGB1 and Hsp70 levels), and cytokine and chemokine production, were compared before and after NIR-PIT.
RESULTS: The serum concentration of HMGB1 increased after NIR-PIT (p = 0.031, Wilcoxon test) in all patients except one who did not achieve a clinical response. Chemokines MIP-1α (CCL3) and MIP-1β (CCL4) increased significantly 1-3 days after treatment (CCL3, p = 0.0036; CCL4, p = 0.0016, Wilcoxon test). A low pre-treatment neutrophil-to-lymphocyte ratio (NLR) was associated with a better response to therapy and survival.
CONCLUSIONS: The release of DAMPs, and cytokine/chemokine production, were detected in the patients\' peripheral blood. The baseline NLR may predict patient outcomes in response to NIR-PIT.

Ideal cancer treatments specifically target and eradicate tumor cells without affecting healthy cells. Therefore, antibody-based therapies that specifically target cancer antigens can be considered ideal cancer therapies. Antibodies linked with small-molecule drugs (i.e., antibody-drug conjugates [ADCs]) are widely used in clinics as antibody-based therapeutics. However, because tumors express antigens heterogeneously, greater target specificity and stable binding of noncleavable linkers in ADCs limit their antitumor effects. To overcome this problem, strategies, including decreasing the binding strength, conjugating more drugs, and targeting tumor stroma, have been applied, albeit with limited success. Thus, further technological advancements are required to remotely control the ADCs. Here, we described a drug that is photo-releasable from an ADC created via simple double conjugation and its antitumor effects both on target and nontarget tumor cells. Specifically, noncleavable T-DM1 was conjugated with IR700DX to produce T-DM1-IR700. Although T-DM1-IR700 itself is noncleavable, with NIR-light irradiation, it can release DM1-derivatives which elicited antitumor effect in vitro mixed culture and in vivo mixed tumor model which are mimicking heterogeneous tumor-antigen expression same as real clinical tumors. This cytotoxic photo-bystander effect occurred in various types mixed cultures in vitro, and changing antibodies also exerted photo-bystander effects, suggesting that this technology can be used for targeting various specific cancer antigens. These findings can potentially aid the development of strategies to address challenges associated with tumor expression of heterogeneous antigen.