Dr. Christine M. Yow Profile

Dr. Christine M. Yow

Associate Professor at Hong Kong Polytechnic Univ

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Proceedings Article | 13 July 2009 Paper

Modulation of COX2 and hTERT expression by photodynamic therapy in human colon cancer cells

Christine Li Miu Yow, Ellie Shihng Chu

Proceedings Volume 7380, 738065 (2009) https://doi.org/10.1117/12.823084

KEYWORDS: Photodynamic therapy, Colorectal cancer, Cancer, Tumors, Cell death, Proteins, Colon, Modulation, Flow cytometry, Oncology

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Photodynamic therapy (PDT) was employed as a cancer therapy with photosensitizer (PS)-loaded cancer cells, eradicated by the reactive oxygen species after light activation. Cyclo-oxygenase 2 (COX2) is an enzyme expressed in 80% of colon adenocarcinoma and is one of the targets for effective cancer treatment. There is also uprising evidence that the human telomerase reverse transcriptase (hTERT), a catalytic component of telomerase, is reported as a promising indicator for monitoring cancer treatment. In this study, NPe6 mediated PDT on COX2 induced apoptosis in HT-29 was investigated. The cell cycle changes was analysed by flow cytometry and the hTERT expression at pre and post PDT was evaluated at transcription level by Taqman real time PCR. NPe6-PDT in HT-29 cells demonstrated anti-proliferating effect in a drug and light dose dependent manner. LD₅₀ was achieved at 16μg/mL and 2J/cm² at 4 hour-post treatment with a significant down-regulation of COX2 expression at LD₃₀ and LD₅₀ by immunohistochemical staining (IHC) (p<0.05, One-Way ANOVA). Membrane blebbing was detected in over 60% of cells. 35.2% of treated cells arrested in S-phase at LD₅₀ after 24 hours by flow cytometry. A 0.25- and 0.6-fold down-regulation of hTERT mRNA expression was achieved at LD₃₀ and LD₅₀ respectively by TaqMan real-time PCR. To summarize, NPe6 mediated PDT down-regulated COX2 expression and triggered cell apoptosis. The hTERT can serve as an indicative marker for monitoring NPe6-PDT cancer treatment efficacy.

Proceedings Article | 18 January 2008 Paper

mTHPC-photodynamic therapy induced apoptosis in nasopharyngeal carcinoma cells

Christine Yow, Albert Leung, Zheng Huang

Proceedings Volume 6826, 68261P (2008) https://doi.org/10.1117/12.756807

KEYWORDS: Photodynamic therapy, Cell death, Proteins, Microscopy, Cancer, Microscopes, Luminescence, Sodium, Synthetic aperture radar, Modulation

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In this study, the early apoptotic events of mTHPC-medicated photodynamic therapy (PDT) was explored in two human nasopharyngeal carcinoma (NPC) cell lines - NPC/HK1 cells and NPC/CNE2 cells. Cells (5 x 10³) were incubated with mTHPC (0.8 μg/ml) in chamber slides for 20 h and subjected to light irradiation at 2 J/cm² (LD₈₀). Morphologic changes of treated cells were examined at 0- 4 h after the light irradiation by a light microscopy. The early stage of apoptosis was detected by fluorescein-conjugated Annexin V (Annexin V-FITC) assay. Mitochondrial membrane damage and cytochrome c release were determined by flowcytometric analysis. The Bcl-2 expression was measured by Western blot analysis. One hour after mTHPC-mediated PDT, membrane blebbing and cell shrinkage appeared in both HK1 and CNE2 cells. Annexin V-FITC assay showed that a considerable number of HK1 and CNE2 cells became apoptotic at 1 h after PDT. Flowcytometric analysis showed that the cytochrome c was released at 1 h after PDT. The Bcl-2 expression also declined significantly in both cell lines compared to the control groups. mTHPC-mediated PDT can effectively induce apoptotic responses in NPC cells which might be modulated by mitochondrial damage and Bcl-2 inhibition.

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