Wing-Ping Fong

Publications of Wing-Ping Fong

• In vitro and in vivo anticarcinogenic effects of RNase MC2, a ribonuclease isolated from dietary bitter gourd, toward human liver cancer cells.

  Authors: Evandro Fei Fang, Chris Zhi Yi Zhang, Lin Zhang, Wing Ping Fong, Tzi Bun Ng

  The international journal of biochemistry & cell biology. 04/2012;

  Hepatocellular carcinoma (HCC) constitutes a predominant part of primary liver cancer which ranks as the fifth most common cancer as well as the third most common cause of cancer mortality. In viewHepatocellular carcinoma (HCC) constitutes a predominant part of primary liver cancer which ranks as the fifth most common cancer as well as the third most common cause of cancer mortality. In view of the poor prognosis of unresectable liver cancers, it is of pivotal importance to develop novel chemotherapeutical regimens. RNase MC2 is a 14-kDa ribonuclease isolated from dietary bitter gourd (Momordica charantia) that manifested antitumor potential against breast cancers. In this study, we investigated the potential application of RNase MC2 on Hep G2 cells. We showed that RNase MC2 inhibited cell proliferation and induced cell apoptosis in both in vitro and in vivo studies. RNase MC2 treatment caused cell cycle arrest predominantly at the S-phase and apoptosis, which is associated with the activation of both caspase-8 and caspase-9 regulated caspase pathways. Our further investigation disclosed that RNase MC2 down-regulated the anti-apoptotic protein Bcl-2 and increased the expression of pro-apoptotic protein Bak. Moreover, the phosphorylation of ERK and JNK was involved in the apoptosis process. Importantly, RNase MC2 significantly suppressed the growth of Hep G2 xenograft-bearing nude mice by inducing apoptosis. This notion is supported by data indicating an increased number of caspase-3- and PARP-positive cells, and TUNEL-positive cells in RNase MC2-treated tumor tissues. In summary, we have revealed the antitumor potential of RNase MC2 toward Hep G2 cells. Considering that bitter gourd is a common dietary component in many countries, this study may help to prompt the clinical application of RNase MC2.

• A phthalocyanine-Peptide conjugate with high in vitro photodynamic activity and enhanced in vivo tumor-retention property.

  Authors: Mei-Rong Ke, Sin-Lui Yeung, Wing-Ping Fong, Dennis K P Ng, Pui-Chi Lo

  Chemistry (Weinheim an der Bergstrasse, Germany). 02/2012; 18(14):4225-33.

  A novel zinc(II) phthalocyanine conjugated with a short peptide with a nuclear localization sequence, Gly-Gly-Pro-Lys-Lys-Lys-Arg-Lys-Val, was synthesized by click chemistry and a standard FmocA novel zinc(II) phthalocyanine conjugated with a short peptide with a nuclear localization sequence, Gly-Gly-Pro-Lys-Lys-Lys-Arg-Lys-Val, was synthesized by click chemistry and a standard Fmoc solid-phase peptide synthesis protocol. The conjugate was purified by HPLC and characterized with UV/Vis and high-resolution mass spectroscopic methods. Both this compound and its non-peptide-conjugated analogue are essentially non-aggregated in N,N-dimethylformamide and can generate singlet oxygen effectively with quantum yields (Φ(Δ) ) of 0.84 and 0.81, respectively, relative to unsubstituted zinc(II) phthalocyanine (Φ(Δ) =0.56). Conjugation of the peptide sequence, however, can enhance the cellular uptake, efficiency in generating intracellular reactive oxygen species, and photocytotoxicity of the phthalocyanine-based photosensitizer against HT29 human colorectal carcinoma cells. The IC(50) value of the conjugate is as low as 0.21 μM. In addition, the conjugate shows an enhanced tumor-retention property in tumor-bearing nude mice. After 72 h post-injection, the dye concentration in the tumor was significantly higher than that in other organs. The results suggest that this phthalocyanine-peptide conjugate is a highly promising photosensitizer for photodynamic therapy.

• RNase MC2: a new Momordica charantia ribonuclease that induces apoptosis in breast cancer cells associated with activation of MAPKs and induction of caspase pathways.

  Authors: Evandro Fei Fang, Chris Zhi Yi Zhang, Wing Ping Fong, Tzi Bun Ng

  Apoptosis : an international journal on programmed cell death. 12/2011;

  Ribonucleases (RNases) are ubiquitously distributed nucleases that cleave RNA into smaller pieces. They are promising drugs for different cancers based on their concrete antitumor activities in vitroRibonucleases (RNases) are ubiquitously distributed nucleases that cleave RNA into smaller pieces. They are promising drugs for different cancers based on their concrete antitumor activities in vitro and in vivo. Here we report for the first time purification and characterization of a 14-kDa RNase, designated as RNase MC2, in the seeds of bitter gourd (Momordica charantia). RNase MC2 manifested potent RNA-cleavage activity toward baker's yeast tRNA, tumor cell rRNA, and an absolute specificity for uridine. RNase MC2 demonstrated both cytostatic and cytotoxic activities against MCF-7 breast cancer cells. Treatment of MCF-7 cells with RNase MC2 caused nuclear damage (karyorrhexis, chromatin condensation, and DNA fragmentation), ultimately resulting in early/late apoptosis. Further molecular studies unveiled that RNase MC2 induced differential activation of MAPKs (p38, JNK and ERK) and Akt. On the other hand, RNase MC2 exposure activated caspase-8, caspase-9, caspase-7, increased the production of Bak and cleaved PARP, which in turn contributed to the apoptotic response. In conclusion, RNase MC2 is a potential agent which can be exploited in the worldwide fight against breast cancer.

• Photodynamic Therapy of Pheophorbide a Inhibits the Proliferation of Human Breast Tumour via Both Caspase-dependent and -independent Apoptotic Pathways in In Vitro and In Vivo Models.

  Authors: Sandy Wan-Heng Hoi, Hoi Ming Wong, Judy Yuet-Wa Chan, Grace Gar Lee Yue, Gary Man-Kit Tse, Bonita Ka-Bo Law, Wing Ping Fong, Kwok Pui Fung

  Phytotherapy research : PTR. 11/2011;

  Breast cancer is conventionally treated by surgery and radiotherapy, with adjuvant chemotherapy and hormonotherapy as supplementary treatments. However, such treatments are associated with adverseBreast cancer is conventionally treated by surgery and radiotherapy, with adjuvant chemotherapy and hormonotherapy as supplementary treatments. However, such treatments are associated with adverse side effects and drug resistance. In this study, Pheophorbide a (Pa), a photosensitizer isolated from Scutelleria barbata, was analysed for its antiproliferative effect on human breast tumour cells. The IC (inhibitory concentration)(50) of the combined treatment of Pa and photodynamic therapy (Pa-PDT) on human breast tumour MCF-7 cells was 0.5 µm. Mechanistic studies in MCF-7 cells demonstrated that Pa was localized in the mitochondria, and reactive oxygen species were found to be released after Pa-PDT. Apoptosis was the major mechanism responsible for the tumour cell death, and mitochondrial membrane depolarization and cytochrome c release highlighted the role of mitochondria in the apoptotic mechanism. Up-regulation of tumour suppressor protein p53, cleavage of caspase-9 and poly (ADP-ribose) polymerase suggested that the caspase-dependent pathway was induced, while the release of apoptosis-inducing factors demonstrated that the apoptosis was also mediated by the caspase-independent mechanism. In vivo study using the mouse xenograft model showed a significant inhibition of MCF-7 tumour growth by Pa-PDT. Together, the results of this study provide a basis for understanding and developing Pa-PDT as a cure for breast cancer. Copyright © 2011 John Wiley & Sons, Ltd.

• Momordica Charantia lectin, a type II ribosome inactivating protein, exhibits antitumor activity toward human nasopharyngeal carcinoma cells in vitro and in vivo.

  Authors: Evandro Fei Fang, Chris Zhi Yi Zhang, Tzi Bun Ng, Jack Ho Wong, Wen Liang Pan, Xiu Juan Ye, Yau Sang Chan, Wing Ping Fong

  Cancer prevention research (Philadelphia, Pa.). 09/2011; 5(1):109-21.

  The incidence of nasopharyngeal carcinoma (NPC) remains high in endemic regions, including southern China, northern Africa, and North America. One of the promising therapeutic approaches on NPC isThe incidence of nasopharyngeal carcinoma (NPC) remains high in endemic regions, including southern China, northern Africa, and North America. One of the promising therapeutic approaches on NPC is drug screening from natural products, such as components from traditional Chinese medicine. In this study, the antitumor activity of Momordica charantia lectin (MCL), a type II ribosome inactivating protein from bitter gourd, on NPC was investigated. MCL evinced potent cytotoxicity toward NPC CNE-1 (IC(50) = 6.9) and CNE-2 (IC(50) = 7.4) cells but minimally affected normal NP 69 cells. Further investigation disclosed that MCL induced apoptosis, DNA fragmentation, G(1)-phase arrest, and mitochondrial injury in both types of NPC cells. The reduction of cyclin D1 and phosphoretinoblastoma (Rb) protein expression contributed to arrest at G(1)-phase of the cell cycle. These events were associated with regulation of mitogen-activated protein kinases (MAPK; including p38 MAPK, JNK, and ERK) phosphorylation and promoted downstream nitric oxide (NO) production. Concurrent administration of the p38 MAPK inhibitor SB-203580 significantly diminished NO production and lethality of MCL toward NPC cells. Further studies revealed that MCL increased cytochrome c release into the cytosol, activated caspases-8, -9, and -3, and enhanced production of cleaved PARP, subsequently leading to DNA fragmentation and apoptosis. Finally, an intraperitoneal injection of MCL (1.0 mg/kg/d) led to an average of 45% remission of NPC xenograft tumors subcutaneously inoculated in nude mice. This is the first article that unveils the potential of a type II RIP, MCL, for prevention and therapy of NPC.

• Unsymmetrical β-cyclodextrin-conjugated silicon(IV) phthalocyanines as highly potent photosensitisers for photodynamic therapy.

  Authors: Janet T F Lau, Pui-Chi Lo, Yee-Man Tsang, Wing-Ping Fong, Dennis K P Ng

  Chemical communications (Cambridge, England). 09/2011; 47(34):9657-9.

  A series of unsymmetrical silicon(IV) phthalocyanines with a permethylated β-cyclodextrin unit and a sugar or a diamino moiety as the axial substituents have been prepared. These compounds are highlyA series of unsymmetrical silicon(IV) phthalocyanines with a permethylated β-cyclodextrin unit and a sugar or a diamino moiety as the axial substituents have been prepared. These compounds are highly photocytotoxic with IC(50) values as low as 21 nM, which is ca. sevenfold lower than those of the symmetrical bis(cyclodextrin) analogue.

• Facile synthesis of pegylated zinc(II) phthalocyanines via transesterification and their in vitro photodynamic activities.

  Authors: Ming Bai, Pui-Chi Lo, Jing Ye, Chi Wu, Wing-Ping Fong, Dennis K P Ng

  Organic & biomolecular chemistry. 08/2011; 9(20):7028-32.

  Treatment of 4,5-bis[4-(methoxycarbonyl)phenoxy]phthalonitrile and 4,5-bis[3,5-bis(methoxycarbonyl)phenoxy]phthalonitrile with an excess of 1,3-diiminoisoindoline in the presence of Zn(OAc)(2)·2H(2)OTreatment of 4,5-bis[4-(methoxycarbonyl)phenoxy]phthalonitrile and 4,5-bis[3,5-bis(methoxycarbonyl)phenoxy]phthalonitrile with an excess of 1,3-diiminoisoindoline in the presence of Zn(OAc)(2)·2H(2)O and 1,8-diazabicyclo[5.4.0]undec-7-ene in triethylene glycol monomethyl ether or polyethylene glycol monomethyl ether (with an average molecular weight of 550) led to "3 + 1" mixed cyclisation and transesterification in one pot, affording the corresponding di-β-substituted zinc(II) phthalocyanines in 7-23% yield. As shown by absorption spectroscopy, these compounds were essentially non-aggregated in N,N-dimethylformamide and could generate singlet oxygen effectively. The singlet oxygen quantum yields (Φ(Δ) = 0.53-0.57) were comparable with that of the unsubstituted zinc(II) phthalocyanine (Φ(Δ) = 0.56). These compounds in Cremophor EL emulsions also exhibited photocytotoxicity against HT29 human colorectal adenocarcinoma and HepG2 human hepatocarcinoma cells with IC(50) values in the range of 0.25-3.72 μM. The analogue with four triethylene glycol chains was the most potent photosensitiser and localised preferentially in the mitochondria of HT29 cells. The bis(polyethylene glycol)-counterpart could form surfactant-free nanoparticles both in water and in the culture medium. The hydrodynamic radii, as determined by dynamic laser light scattering, ranged from 6.3 to 79.8 nm depending on the preparation methods and conditions. The photocytotoxicity of these nanoparticles (IC(50) = 0.43-0.56 μM) was comparable with that of the Cremophor EL-formulated system (IC(50) = 0.34 μM).

• Preparation and photodynamic activities of silicon(IV) phthalocyanines substituted with permethylated β-cyclodextrins.

  Authors: Janet T F Lau, Pui-Chi Lo, Wing-Ping Fong, Dennis K P Ng

  Chemistry (Weinheim an der Bergstrasse, Germany). 06/2011; 17(27):7569-77.

  A series of silicon(IV) phthalocyanines linked to two permethylated β-cyclodextrin moieties through different spacers at the axial positions have been synthesized and characterized. The effects ofA series of silicon(IV) phthalocyanines linked to two permethylated β-cyclodextrin moieties through different spacers at the axial positions have been synthesized and characterized. The effects of these spacers on the photophysical properties and in vitro photodynamic activities have also been examined. Having two bulky hydrophilic substituents, all of these compounds are soluble and essentially nonaggregated in DMF and even in aqueous media. The fluorescence and singlet oxygen quantum yields in DMF are lower for the analogue with the shortest separation between the amino group in the spacer and the phthalocyanine ring. The fluorescence quantum yield of this compound increases in water probably due to protonation of the amino group, which inhibits the reductive quenching process. This series of compounds also exhibit photocytotoxicity toward HT29 human colon adenocarcinoma and HepG2 human hepatocarcinoma cells with IC(50) values in the range of 0.04-1.32 μM. The analogue with an α,ω-aminohydroxypentyl linker shows the highest potency, which can be ascribed to its high cellular uptake and high efficiency in generating intracellular reactive oxygen species. This compound also shows preferential localization in the lysosome, induces cell death mainly through apoptosis, and inhibits the growth of tumor in vivo. The results suggest that it is a promising photosensitizer for photodynamic therapy.

• Preparation of unsymmetrical distyryl BODIPY derivatives and effects of the styryl substituents on their in vitro photodynamic properties.

  Authors: Hui He, Pui-Chi Lo, Sin-Lui Yeung, Wing-Ping Fong, Dennis K P Ng

  Chemical communications (Cambridge, England). 03/2011; 47(16):4748-50.

  A series of unsymmetrical distyryl BODIPYs have been prepared which function as highly potent photosensitisers with in vitro IC(50) values as low as 15 nM. Their cellular uptake, subcellularA series of unsymmetrical distyryl BODIPYs have been prepared which function as highly potent photosensitisers with in vitro IC(50) values as low as 15 nM. Their cellular uptake, subcellular localisation and photocytotoxicity depend greatly on the styryl substituents.

• Synthesis and in vitro photodynamic activities of pegylated distyryl boron dipyrromethene derivatives.

  Authors: Hui He, Pui-Chi Lo, Sin-Lui Yeung, Wing-Ping Fong, Dennis K P Ng

  Journal of medicinal chemistry. 03/2011; 54(8):3097-102.

  A series of pegylated distyryl boron dipyrromethenes have been prepared and characterized. Their in vitro photodynamic activities in Tween 80 emulsions have also been investigated against HT29 humanA series of pegylated distyryl boron dipyrromethenes have been prepared and characterized. Their in vitro photodynamic activities in Tween 80 emulsions have also been investigated against HT29 human colorectal carcinoma cells. The derivative having five triethylene glycol chains (compound 8) exhibits the highest photocytotoxicity with an IC(50) as low as 7 nM. It is also localized preferentially in the endoplasmic reticulum of the cells and can induce predominately apoptosis upon illumination.

• Metergoline-induced cell death in Candida krusei.

  Authors: Kai Kang, Kin-Sing Wong, Wing-Ping Fong, Paul Wai-Kei Tsang

  Fungal biology. 03/2011; 115(3):302-9.

  Metergoline possesses potent antifungal activity against Candida krusei, a notorious yeast species that is inherently resistant to the common antifungal agents. In an attempt to elucidate the actionMetergoline possesses potent antifungal activity against Candida krusei, a notorious yeast species that is inherently resistant to the common antifungal agents. In an attempt to elucidate the action mechanisms of metergoline, the present study was designed to investigate its effects on a number of classical markers of apoptosis in C. krusei. The results showed that transient exposure (2h) to metergoline led to a massive intracellular accumulation of reactive oxygen species (ROS) and depolarization of mitochondrial membrane potential in a concentration-dependent fashion. Analyses of the treated fungal cells after prolonged incubation (12h) with metergoline by flow cytometry and fluorescence microscopy clearly demonstrated phosphatidylserine externalization, the presence of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling-positive cells and fungal cells undergoing necrosis. Taken together, our data provide evidence that metergoline elicited cell death process in C. krusei through elevation of the intracellular ROS level and perturbation of mitochondrial homeostasis, followed by damage of nucleus and eventual cell demise.

• Antifungal activity of baicalein against Candida krusei does not involve apoptosis.

  Authors: Kai Kang, Wing-Ping Fong, Paul Wai-Kei Tsang

  Mycopathologia. 12/2010; 170(6):391-6.

  The present study was designed to evaluate the antifungal activity of baicalein against Candida krusei isolates. Using a broth microdilution assay, baicalein exhibited potent in vitro antifungalThe present study was designed to evaluate the antifungal activity of baicalein against Candida krusei isolates. Using a broth microdilution assay, baicalein exhibited potent in vitro antifungal activity against C. krusei isolates with a minimum inhibitory concentration of 2.7 μg/ml. Flow cytometric study indicated that baicalein depolarized mitochondrial membrane potential in a concentration-dependent manner. However, mechanistic analyses showed that the intracellular reactive oxygen species (ROS) level was virtually unchanged, and massive DNA fragmentation was not observed in C. krusei isolates after baicalein treatment even at a concentration which was apoptotic in C. albicans. Taken together, we conclude that the antifungal activity of baicalein in C. krusei isolates occurs through perturbation in mitochondrial homeostasis without causing elevation of the intracellular ROS level and does not involve apoptosis.

• Phthalocyanine-polyamine conjugates as highly efficient photosensitizers for photodynamic therapy.

  Authors: Xiong-Jie Jiang, Sin-Lui Yeung, Pui-Chi Lo, Wing-Ping Fong, Dennis K P Ng

  Journal of medicinal chemistry. 12/2010; 54(1):320-30.

  A series of silicon(IV) phthalocyanines substituted axially with different polyamine moieties have been prepared. Their fluorescence quantum yields (Φ(F) = 0.03-0.08) in N,N-dimethylformamide are lowA series of silicon(IV) phthalocyanines substituted axially with different polyamine moieties have been prepared. Their fluorescence quantum yields (Φ(F) = 0.03-0.08) in N,N-dimethylformamide are low because of reductive quenching by the amino moieties. The values are significantly increased in aqueous media (Φ(F) = 0.12-0.21) as a result of protonation of the amino substituents. All the compounds are highly photocytotoxic against human colon adenocarcinoma HT29 cells and Chinese hamster ovary cells with IC(50) values as low as 1.1 nM. Flow cytometric studies of two selected compounds (2 and 5) against HT29 cells have shown that they induce apoptosis extensively. As shown by confocal microscopy, these two compounds also show high affinity toward the lysosomes, but not the mitochondria, of the cells. Their in vivo photodynamic activity has also been investigated using HT29 tumor bearing nude mice. Both of them can effectively inhibit the growth of the tumor without causing apparent injury to the liver of the mice.

• Human antiquitin: structural and functional studies.

  Authors: Chi-Lung Chan, Judy W Y Wong, Chun-Pong Wong, Michel K L Chan, Wing-Ping Fong

  Chemico-biological interactions. 12/2010; 191(1-3):165-70.

  Antiquitin (ALDH7) is a member of the aldehyde dehydrogenase superfamily which oxidizes various aldehydes to form the corresponding carboxylic acids. Human antiquitin (ALDH7A1) is believed to play aAntiquitin (ALDH7) is a member of the aldehyde dehydrogenase superfamily which oxidizes various aldehydes to form the corresponding carboxylic acids. Human antiquitin (ALDH7A1) is believed to play a role in detoxification, osmoregulation and more specifically, in lysine metabolism in which alpha-aminoadipic semialdehyde is identified as the specific, physiological substrate of the enzyme. In the present study, the structural basis for the substrate specificity was studied by site-directed mutagenesis. Kinetic analysis on wild-type human antiquitin and its mutants E121A and R301A demonstrated the importance of Glu121 and Arg301 in the binding as well as the turnover of alpha-aminoadipic semialdehyde. On the functional aspect, in addition to the already diversified physiological functions of antiquitin, the recent demonstration of its presence in the nucleus suggests that it may also play a role in cell growth and cell cycle progression. In this investigation, the expression level of antiquitin was monitored in synchronized WRL68 and HEK293 cell culture systems. It was found that the protein was up-regulated during G(1)-S phase transition. Immunofluorescence staining of the synchronized cells demonstrated an increased expression and accumulation of antiquitin in the nucleus during the G(1)-S phase transition. Knockdown of antiquitin using shRNA transfection also resulted in changes in the levels of several key cell cycle-regulating proteins.

• Photodynamic activity of a glucoconjugated silicon(IV) phthalocyanine on human colon adenocarcinoma.

  Authors: Crystal M H Chan, Pui-Chi Lo, Sin-Lui Yeung, Dennis K P Ng, Wing-Ping Fong

  Cancer biology & therapy. 07/2010; 10(2):126-34.

  Photodynamic therapy (PDT) involves the use of a non-toxic photosensitizer which exhibits a killing effect upon activation by light. In the past few years, we have synthesized a number of novelPhotodynamic therapy (PDT) involves the use of a non-toxic photosensitizer which exhibits a killing effect upon activation by light. In the past few years, we have synthesized a number of novel second generation photosensitizers with superior properties, most of them are phthalocyanines. Among them, the glucoconjugated silicon(IV) phthalocyanine (SiPcGlu) shows potent phototoxicity against human colorectal adenocarcinoma HT29 cells. In the present study, its action mechanism was investigated. The initiation of apoptosis by SiPcGlu-PDT, subsequent to reactive oxygen species production, was shown by the results of TUNEL assay, annexin V and propidium iodide staining and DNA ladder pattern analysis. Confocal microscopy revealed the presence of SiPcGlu in lysosome, mitochondria and endoplasmic reticulum. SiPcGlu-PDT did not cause any damage to the lysosomal membrane; whereas in the mitochondria, it caused membrane depolarization and the release of cytochrome c into the cytosol, which subsequently brought about caspase-3 activation. In the endoplasmic reticulum, the treatment led to Ca(2+) release and an increase in the expression level of the chaperone protein GRP78. These observations suggest that SiPcGlu-PDT triggered the apoptotic pathways in both mitochondria and endoplasmic reticulum, but not the lysosome. A preliminary study of the photodynamic activity of SiPcGlu in the in vivo animal model was also carried out. It retarded tumor growth in HT29 tumor-bearing nude mice while causing no apparent toxicity to the animal.

• A pH-responsive fluorescence probe and photosensitiser based on a tetraamino silicon(IV) phthalocyanine.

  Authors: Xiong-Jie Jiang, Pui-Chi Lo, Sin-Lui Yeung, Wing-Ping Fong, Dennis K P Ng

  Chemical communications (Cambridge, England). 05/2010; 46(18):3188-90.

  A novel tetraamino silicon(iv) phthalocyanine has been prepared, of which the fluorescence emission and reactive oxygen species generation efficiency are greatly enhanced at lower pH in the range ofA novel tetraamino silicon(iv) phthalocyanine has been prepared, of which the fluorescence emission and reactive oxygen species generation efficiency are greatly enhanced at lower pH in the range of ca. 5-7, making it a promising pH-controlled and tumour-selective fluorescence probe and photosensitiser for photodynamic therapy.

• Pheophorbide a-Mediated Photodynamic Therapy Triggers HLA Class I-Restricted Antigen Presentation in Human Hepatocellular Carcinoma.

  Authors: Patrick Ming-Kuen Tang, Ngoc-Ha Bui-Xuan, Chun-Kwok Wong, Wing-Ping Fong, Kwok-Pui Fung

  Translational oncology. 04/2010; 3(2):114-22.

  The immunomodulatory effects of photodynamic therapy (PDT) have been reported in several photosensitizers. Pheophorbide a (Pa), a chlorophyll derivative, shows antitumor effects on a number of humanThe immunomodulatory effects of photodynamic therapy (PDT) have been reported in several photosensitizers. Pheophorbide a (Pa), a chlorophyll derivative, shows antitumor effects on a number of human cancers in a PDT approach (Pa-PDT); however, the potential effect of Pa-PDT on the anticancer immunity has never been studied. In the present work, the underlying action mechanism of Pa-PDT was systemically investigated with a human hepatoma cell line HepG2. We found that Pa-PDT significantly inhibited the growth of HepG2 cells with a half maximal inhibitory concentration/endoplasmic reticulum of 0.35 microM at 24 hours by the induction of apoptosis, as shown by externalization of phosphatidylserine, release of mitochondrial cytochrome c, and activation of the caspases cascade in the treated cells. Interestingly, using two-dimensional polyacrylamide gel electrophoresis analysis, a 57-kDa disulfide-isomerase-like ER resident protein (ERp57) that belongs to the HLA class I-restricted antigen-processing machinery was found to be mediated during the Pa-PDT treatment. This activation of antigen presentation was confirmed by Western blot analysis and immunostaining. Furthermore, a cross-presentation of antigen with HLA class I proteins and 70-kDa heat shock protein was found in Pa-PDT-treated cells, as shown by the confocal microscopic observation and immunoprecipitation assay. Nevertheless, the immunogenicity of HepG2 cells was increased by Pa-PDT treatment that triggered phagocytic capture by human macrophages. Our findings provide the first evidence that Pa-PDT can trigger both apoptosis and cancer immunity in the tumor host.

• Novel antifungal activity of purpurin against Candida species in vitro.

  Authors: Kai Kang, Wing-Ping Fong, Paul Wai-Kei Tsang

  Medical mycology : official publication of the International Society for Human and Animal Mycology. 04/2010; 48(7):904-11.

  The antifungal activity of purpurin (1,2,4-trihydroxy-9,10-anthraquinone), a natural red anthraquinone pigment in madder root (Rubia tinctorum L.), was evaluated by a broth microdilution assayThe antifungal activity of purpurin (1,2,4-trihydroxy-9,10-anthraquinone), a natural red anthraquinone pigment in madder root (Rubia tinctorum L.), was evaluated by a broth microdilution assay against a total of 24 Candida isolates representing six species. The minimum inhibitory concentration (MIC) range of purpurin was 1.28-5.12 μg/ml. Mechanistic studies using the rhodamine 6G extrusion assay indicated that purpurin inhibited the energy-dependent efflux pumps of the Candida isolates in a dose-dependent manner. Furthermore, purpurin demonstrated a dose-dependent depolarization of mitochondrial membrane potential, one of the biochemical checkpoints regulating cell death in eukaryotic cells, suggesting a possible linkage between purpurin antifungal mechanism and Candida apoptosis.

• Phthalocyanine-polyamine conjugates as pH-controlled photosensitizers for photodynamic therapy.

  Authors: Xiong-Jie Jiang, Pui-Chi Lo, Yee-Man Tsang, Sin-Lui Yeung, Wing-Ping Fong, Dennis K P Ng

  Chemistry (Weinheim an der Bergstrasse, Germany). 03/2010; 16(16):4777-83.

  A series of aryl hydroxyamines prepared by reductive amination were treated with silicon(IV) phthalocyanine dichloride in the presence of pyridine to give the diaxially substitutedA series of aryl hydroxyamines prepared by reductive amination were treated with silicon(IV) phthalocyanine dichloride in the presence of pyridine to give the diaxially substituted phthalocyanine-polyamine conjugates 1-5. The electronic absorption, fluorescence emission, and efficiency at generating reactive oxygen species of these compounds were all sensitive to the pH environment. Under acidic conditions, the fluorescence quantum yields and the singlet oxygen quantum yields of these compounds were greatly enhanced in DMF as a result of protonation of the amino moieties, which inhibited the photoinduced electron-transfer deactivation pathway. The Q band was diminished and broadened, and the fluorescence intensity decreased as the pH increased in citrate buffer solutions. The rate of superoxide radical formation was also reduced in a higher pH environment. Compound 3, containing a terminal 4-chlorophenyl group at the axial substituent, showed the most desirable pH-responsive properties, which makes it a promising tumor-selective fluorescence probe and photosensitizer for photodynamic therapy. All of the phthalocyanines 1-5 were highly photocytotoxic against HT29 and HepG2 cells with IC(50) values as low as 0.03 microM. Compound 3 was highly selective toward lysosomes, but not mitochondria of HT29 cells.

• Preparation and in vitro photodynamic activity of amphiphilic zinc(II) phthalocyanines substituted with 2-(dimethylamino)ethylthio moieties and their N-alkylated derivatives.

  Authors: Wubiao Duan, Pui-Chi Lo, Lei Duan, Wing-Ping Fong, Dennis K P Ng

  Bioorganic & medicinal chemistry. 02/2010; 18(7):2672-7.

  Treatment of 4,5-dichlorophthalonitrile with 2-(dimethylamino)ethanethiol hydrochloride and K(2)CO(3) afforded 4,5-bis[2-(dimethylamino)ethylthio]phthalonitrile or a heterocycle-fused phthalonitrileTreatment of 4,5-dichlorophthalonitrile with 2-(dimethylamino)ethanethiol hydrochloride and K(2)CO(3) afforded 4,5-bis[2-(dimethylamino)ethylthio]phthalonitrile or a heterocycle-fused phthalonitrile depending on the reaction temperature. The latter has been spectroscopically and structurally characterized. Both compounds underwent mixed cyclization with 3equiv of unsubstituted phthalonitrile in the presence of Zn(OAc)(2).2H(2)O and 1,8-diazabicyclo[5.4.0]undec-7-ene to give the corresponding 2,3-disubstituted zinc(II) phthalocyanines. N-methylation or pentylation of the bis[2-(dimethylamino)ethylthio] substituted analogue resulted in the formation of the respective dicationic phthalocyanines. For comparison, the octa-substituted analogues were also prepared by base and zinc-promoted self-cyclization of 4,5-bis[2-(dimethylamino)ethylthio]phthalonitrile followed by N-methylation. The spectroscopic and basic photophysical properties of these di- and octa-substituted phthalocyanines were examined in N,N-dimethylformamide. All of them remained essentially non-aggregated, showed moderate fluorescence emission, and could generate singlet oxygen, except the heterocycle-fused analogue, of which the singlet excited state was reductively quenched by the amino substituent. The photocytotoxicity of these compounds was also evaluated against HepG2 human hepatocarcinoma cells and HT29 and T84 human colon adenocarcinoma cells. The disubstituted amphiphilic phthalocyanines are particularly potent with IC(50) values down to 0.08microM. Fluorescence microscopic studies revealed that the non-ionic derivative has selective affinity to the mitochondria of HT29 cells, while its di-N-methylated analogue shows preferential localization in the cell membrane.