Abstract
Simple SummaryWhile photodynamic therapy (PDT) has emerged as an attractive treatment for certain cancer types, it still lacks cancer specificity, which limits therapeutic efficacy and damages normal tissues. The present study aimed to evaluate the targeting potential of a novel minibody that recognizes a cell surface receptor expressed on various cancer cell lines. The engineered minibody-photosensitizer conjugate (MS5-IR700) killed target cells in both cell monolayer and tumor spheroid cultures. Additionally, the conjugate induced immunogenic cell death. Hence, the developed minibody could be used as a photosensitizer carrier for -cancer cell-targeted PDT.Photodynamic therapy (PDT) is a treatment strategy that utilizes photosensitizers (PSs) and light of a specific wavelength to kill cancer cells. However, limited tumor specificity is still a drawback for the clinical application of PDT. To increase the therapeutic efficacy and specificity of PDT, a novel human minibody (MS5) that recognizes a cell surface receptor expressed on various cancer cells was labeled with the hydrophilic phthalocyanine PS IR700 to generate an MS5-IR700 conjugate that is activated by near-infrared (NIR) light. The phototoxicity of the conjugate was mainly tested against the PC3 prostate cancer cell line. The MS5-IR700 conjugate killed PC3 cells after NIR light irradiation as compared to untreated cells or cells treated with IR700 alone. Time-course analysis of cell viability revealed a high percentage of cell death during the first hour in PC3 cells exposed to the MS5-IR700 conjugate and NIR light irradiation. After irradiation, the MS5-IR700 conjugate-treated PC3 cells displayed cellular swelling, round shape, and rupture of the cell and nuclear membranes. In a co-culture model, the MS5-IR700 conjugate killed MS5-positive Ramos lymphoma cells specifically, while leaving MS5-negative cells unaffected. In line with the data obtained with the monolayer cultures, the MS5-IR700 conjugate also killed PC3 cancer cell spheroids. The treatment induced relocation of heat shock protein 70 and calreticulin to the cell surface, implying the induction of immunogenic cell death. Overall, the data suggest that the developed MS5-IR700 conjugate is a promising therapeutic agent that warrants further preclinical studies.
Highlights
Photodynamic therapy (PDT) is a two-stage strategy involving the administration of a photosensitizer (PS) followed by exposure to light [1,2,3,4,5]
The MS5 minibody recognizes a receptor overexpressed on the surface of cancer cells including prostate cancer, breast cancer, lung cancer, head and neck cancer, and various lymphomas derived from different stages of B cell differentiation [20]
Under non-reducing conditions (NR), the MS5-IR700 conjugate was visualized as a major single band of 110 kDa, it would form disulfide bond-containing dimers under physiological conditions (Figure 1B)
Summary
Photodynamic therapy (PDT) is a two-stage strategy involving the administration of a photosensitizer (PS) followed by exposure to light [1,2,3,4,5]. In the presence of tissue oxygen, the PS activated by light of a specific wavelength can stimulate the production of reactive oxygen species (ROS), leading to cell death by apoptosis or necrosis. PDT is used in the clinical treatment of several cancers, including skin, esophageal non-small cell, and oral cancers [3,5,6]. The light activation of PSs enables a certain level of selectivity and prevents damage to healthy tissue surrounding the tumor, photosensitive reactions are regularly seen in normal tissues, such as the skin and eyes that are exposed to daylight [7]. The major remaining challenge is to identify a ligand that can navigate PSs to tumor sites
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