Abstract 3313: Evaluation of silicon phthalocyanine 4 photodynamic therapy in human cervical cancer cells
Authors: Gadzinski Jill A. , Philips Brian , Basse Per , Guo Jianxia , Sen Gupta Anirban , Bailey Lisa , Comerci John T. , Eiseman Julie L. 
Published: August 2015

Introduction: Cervical cancer is the second most common cancer in women worldwide. In the US there will be approximately 12,360 new cases and 4,040 deaths in 2014. Treatment of locally advanced disease with concomitant- chemoradiation is suboptimal and leaves 40% of patients with residual disease. There are limitations on the total radiation dose that can be administered. There has been little progress examining novel therapeutic modalities for locally advanced cervical cancer. Photodynamic therapy (PDT) is a potential adjuvant to standard treatment. PDT requires a light source, a photosensitizer and oxygen to generate reactive oxygen species that kill cells. Silicon phthalocyanine 4 (Pc 4) is a second generation photosensitizer that has been evaluated in clinical trials. In this study we evaluated the effectiveness of in vitro Pc 4 PDT in human cervical cancer cells.

Methods: CaSki and ME180, human metastatic cervical cancer cell lines expressing epidermal growth factor receptor (EGRF), were obtained from ATCC. Cells (104 cells/100 μL) were grown as monolayers in 96 well plates in RPMI 1640 medium without phenol red containing 100 IU Penicillin and 100 μg/ ml Streptomycin at 37°C, 5% CO2, 95% humidity. Cell growth was measured using a Methylthiazol Tetrazolium (MTT) assay. Pc 4 cellular uptake was determined at 0.3 μM Pc 4 by fluorescence back calculated against Pc 4 standard curves (excitation 350 nm, emission 670 nm) and expressed as % Pc 4. For the Pc 4 PDT experiments, concentrations of Pc 4 from 0.001 to 10 μM were added starting 24 hours after cells were plated. Forty-eight hours after Pc 4 addition, cells were irradiated with a diode laser at 667 nm at a fluence of 2.5 J/cm2. A control plate was shielded from the laser. Twenty-four hours after PDT, cell viability was assessed via MTT assay. Percent inhibition was calculated from observed data and the IC50 was calculated from the Hill equation using ADAPT 5. Confocal imaging was performed to determine the intracellular distribution of Pc 4; mitochondria and lysosomes were imaged using MitoTracker® (Cell Signaling) and LysoTracker® (Life Technologies), respectively.

Results: ME180 cells have a doubling time of approximately 21 hours, while CaSki cells double in approximately 48 hours. Pc 4 is taken up by each cell line and the majority of uptake occurs by approximately 6 hours. Pc 4 was not toxic to the cells at concentration below 10 μM. Following Pc 4 PDT, the IC50s for CaSki and ME180 cells were, respectively, 0.413 μM (%CV 11.9) and 0.088 μM (%CV 119,000). Pc 4 distributed throughout the cells, overlapping with both the mitochondrial and lysosomal markers, as well being present within the cytoplasm.

Conclusion: Pc4 PDT is effective for the treatment of human cervical cancer cells. Additional studies will evaluate Pc 4 PDT using EGFR targeted, Pc 4 loaded nanoparticles as well as cervical cancer spheroids.

Support: P30-CA47904, CTSI BaCCoR Pilot Program

Citation Format: Jill A. Gadzinski, Brian Philips, Per Basse, Jianxia Guo, Anirban Sen Gupta, Lisa Bailey, John T. Comerci, Julie L. Eiseman. Evaluation of silicon phthalocyanine 4 photodynamic therapy in human cervical cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3313. doi:10.1158/1538-7445.AM2015-3313