Diane Shin1, Lina Nguyen2, Mai T Le2, David Ju2, Jimmy N Le2, Kristian Berg3, Henry Hirschberg2. 1. Beckman Laser Institute and Medical Clinic, University of California, Irvine 1002 Health Sciences Rd, Irvine, CA 92617, USA. Electronic address: diane.shin77@gmail.com. 2. Beckman Laser Institute and Medical Clinic, University of California, Irvine 1002 Health Sciences Rd, Irvine, CA 92617, USA. 3. Dept. of Radiation Biology, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, N-0310, Oslo, Norway.
Abstract
BACKGROUND: Photodynamic therapy (PDT), if given over extended time periods (i.e. hours or days) and at very low irradiance in the μW/cm2 range, has been shown to be more effective than acute PDT (aPDT) administered over minutes. This has led to the concept of metronomic PDT (mPDT), which consists of ultra-low irradiance light illumination for extended periods of time along with either continuous or repetitive delivery of photosensitizer. Since the drug activating technology photochemical internalization (PCI) is based on PDT it seemed reasonable to expect that ultra-low irradiance, if administered over an extended period of time, could nevertheless result in effective metronomic PCI (mPCI) comparable to or more effective than that obtained with relatively high and short irradiance i.e. acute PCI (aPCI). METHODS: Tumor spheroids consisting of F98 cells were used as in-vitro tumor models. The amphiphilic photosensitizer Al phthalocyanine disulfonate (AlPcS2a) was used for all PCI experiments. Light treatment was administered from a diode laser at λ=670 nm at various irradiance exposures of 2 mW/cm2 for aPCI and 0.05 - 0.2 mW/cm2 for mPCI with durations ranging from 3 to 12 min for aPCI and 120 min for mPCI. RESULTS: AlPcS2a fluorescence was seen throughout the cytosol following short or long light treatment, corresponding to aPCI and mPCI respectively. Spheroid growth was significantly inhibited or completely suppressed at a mPCI radiance of 0.05 or 0.72 J/cm2 respectively, with all bleomycin (BLM) concentrations used, compared to either BLM alone or aPCI at radiant exposure at these levels. The effects of BLM-aPCI and mPCI were comparable at radiance levels of 0.96 and 1.44 J/cm2. CONCLUSIONS: Results show that mPCI could effectively cause significant spheroid growth inhibition with the delivery of extremely low light irradiance rates delivered over an extended period of time. These findings suggest that effective implementation of mPCI can deliver adequate drug efficacy at depths necessary to reach infiltrating glioma cells in the surgical resection cavity wall.
BACKGROUND: Photodynamic therapy (PDT), if given over extended time periods (i.e. hours or days) and at very low irradiance in the μW/cm2 range, has been shown to be more effective than acute PDT (aPDT) administered over minutes. This has led to the concept of metronomic PDT (mPDT), which consists of ultra-low irradiance light illumination for extended periods of time along with either continuous or repetitive delivery of photosensitizer. Since the drug activating technology photochemical internalization (PCI) is based on PDT it seemed reasonable to expect that ultra-low irradiance, if administered over an extended period of time, could nevertheless result in effective metronomic PCI (mPCI) comparable to or more effective than that obtained with relatively high and short irradiance i.e. acute PCI (aPCI). METHODS:Tumor spheroids consisting of F98 cells were used as in-vitro tumor models. The amphiphilic photosensitizer Al phthalocyanine disulfonate (AlPcS2a) was used for all PCI experiments. Light treatment was administered from a diode laser at λ=670 nm at various irradiance exposures of 2 mW/cm2 for aPCI and 0.05 - 0.2 mW/cm2 for mPCI with durations ranging from 3 to 12 min for aPCI and 120 min for mPCI. RESULTS:AlPcS2a fluorescence was seen throughout the cytosol following short or long light treatment, corresponding to aPCI and mPCI respectively. Spheroid growth was significantly inhibited or completely suppressed at a mPCI radiance of 0.05 or 0.72 J/cm2 respectively, with all bleomycin (BLM) concentrations used, compared to either BLM alone or aPCI at radiant exposure at these levels. The effects of BLM-aPCI and mPCI were comparable at radiance levels of 0.96 and 1.44 J/cm2. CONCLUSIONS: Results show that mPCI could effectively cause significant spheroid growth inhibition with the delivery of extremely low light irradiance rates delivered over an extended period of time. These findings suggest that effective implementation of mPCI can deliver adequate drug efficacy at depths necessary to reach infiltrating glioma cells in the surgical resection cavity wall.
Authors: K Berg; P K Selbo; L Prasmickaite; T E Tjelle; K Sandvig; J Moan; G Gaudernack; O Fodstad; S Kjølsrud; H Anholt; G H Rodal; S K Rodal; A Høgset Journal: Cancer Res Date: 1999-03-15 Impact factor: 12.701
Authors: Henry Hirschberg; Dag R Sørensen; Even Angell-Petersen; Qian Peng; Bruce Tromberg; Chung-Ho Sun; Signe Spetalen; Steen Madsen Journal: J Environ Pathol Toxicol Oncol Date: 2006 Impact factor: 3.567