title: Anticancer drug released from near IR-activated prodrug overcomes spatiotemporal limits of singlet oxygen.
abstract: Photodynamic therapy (PDT) is a cancer treatment modality where photosensitizer (PS) is activated by visible and near IR light to produce singlet oxygen ((1)O2). However, (1)O2 has a short lifetime (<40 ns) and cannot diffuse (<20 nm) beyond the cell diameter (e.g., ∼ 1800 nm). Thus, (1)O2 damage is both spatially and temporally limited and does not produce bystander effect. In a heterogeneous tumor, cells escaping (1)O2 damage can regrow after PDT treatment. To overcome these limitations, we developed a prodrug concept (PS-L-D) composed of a photosensitizer (PS), an anti-cancer drug (D), and an (1)O2-cleavable linker (L). Upon illumination of the prodrug, (1)O2 is generated, which damages the tumor and also releases anticancer drug. The locally released drug could cause spatially broader and temporally sustained damage, killing the surviving cancer cells after the PDT damage. In our previous report, we presented the superior activity of our prodrug of CA4 (combretastatin A-4), Pc-(L-CA4)2, compared to its non-cleavable analog, Pc-(NCL-CA4)2, that produced only PDT effects. Here, we provide clear evidence demonstrating that the released anticancer drug, CA4, indeed damages the surviving cancer cells over and beyond the spatial and temporal limits of (1)O2. In the limited light illumination experiment, cells in the entire well were killed due to the effect of released anti-cancer drug, whereas only a partial damage was observed in the pseudo-prodrug treated wells. A time-dependent cell survival study showed more cell death in the prodrug-treated cells due to the sustained damage by the released CA4. Cell cycle analysis and microscopic imaging data demonstrated the typical damage patterns by CA4 in the prodrug treated cells. A time-dependent histological study showed that prodrug-treated tumors lacked mitotic bodies, and the prodrug caused broader and sustained tumor size reduction compared to those seen in the tumors treated with the pseudo-prodrug. This data consistently support that the released CA4 overcomes the spatiotemporal limitations of (1)O2, providing far superior antitumor effect.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, United States.
authors.forename: Pallavi
authors.initials: P
authors.lastname: Rajaputra
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, United States.
authors.forename: Moses
authors.initials: M
authors.lastname: Bio
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, United States.
authors.forename: Gregory
authors.initials: G
authors.lastname: Nkepang
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, United States.
authors.forename: Pritam
authors.initials: P
authors.lastname: Thapa
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, United States.
authors.forename: Sukyung
authors.initials: S
authors.lastname: Woo
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, United States; Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, United States. Electronic address: youngjae-you@ouhsc.edu.
authors.forename: Youngjae
authors.initials: Y
authors.lastname: You
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D005260:Female; D006801:Humans; D007259:Infrared Rays; D061986:MCF-7 Cells; D015394:Molecular Structure; D011355:Prodrugs / Q000737:chemistry / Q000494:pharmacology*; D026082:Singlet Oxygen / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D011355:Prodrugs; D026082:Singlet Oxygen
keywords: Bystander effect; Combretastatin A-4; Light-activatable prodrug; Photodynamic therapy; Singlet oxygen; Spatiotemporal limits