Research Progress on Nasopharyngeal Carcinoma (NPC) 2013

  1. Preclinical testing of anti-cancer targeted drug against heat shock protein-90 in nasopharyngeal cancer (NPC) cell lines
Active cytotoxic agents for treating NPC patients include cisplatinum, carboplatin, 5-fluorouracil (5-FU), gemcitabine, methotrexate, anthracycline, bleomycin and ifosfamide. For years, the combination of cisplatinum and 5-FU is considered as the standard first-line chemotherapy regimen for NPC. However, despite the high activity of the first line chemotherapeutic drugs, therapeutic options for second line treatment were limited. There remains an unmet clinical need for new therapeutic approaches in treating advanced / metastatic NPC. Heat shock protein, HSP90 is a chaperone protein involving in the maturation of many cellular proteins. For instance, several oncogenic proteins such as EGFR, VEGF, c-met, Her-2 and AKT are the client proteins of HSP90. Targeting multiple client proteins by HSP90 inhibitor might offer a therapeutic advantage over drug with only a single molecular target. For this reason, we are performing a preclinical testing of an anti-cancer targeted drug, AUY922 which is an inhibitor for the heat shock protein, HSP90. In this study, both in vivo and in vitro models have been employed. Nude mice bearing subcutaneous NPC C666 and HONE1 tumor xenografts are treated by AUY922 in parallel with conventional drugs such as cisplatinum and 5-FU through intraperitoneal injection. Tumor sizes of the xenograft were periodically measure every three days. The results showed that AUY922 resulted in inhibition of tumor growth in a dose dependent manner. 50% growth inhibition drug concentration (GI-50) was also defined in C666 and HONE1 NPC cell lines. Preliminary flow cytometry analysis showed drug induced death caused by both apoptosis and necrosis. Epstein-Barr virus (EBV) is an oncogenic virus strongly associated with NPC whereas kinase pathway is the underneath mechanism by which the drug exert its therapeutic effects. Western blotting is therefore employed to examine if there is any change of EBV viral lytic and latent cycle antigens on drug treatment and the molecules under phosphorylation by the kinase pathway. More molecular analysis in the signaling pathway of the drug mechanism will be performed. This project is lasting for 1 year and was started from January, 2013 and will finish at the end of January, 2014.
  1. Characterization of carcinogen detoxification enzymes by tissue immunohistochemical staining
Using gene chip technology, we have discovered a series of xenobiotic detoxification enzyme genes which were either substantially increased or decreased in gene expression in nasopharyngeal cancer tissues as compared with normal tissues. The importance of these enzymes lies in the fact that they can detoxify a variety of carcinogens and facilitate their excretion. This results in protecting the normal epithelium of the gastrointestinal tract from carcinogen insults and thus could have cancer prevention effect. We further characterize these detoxification enzymes in normal and tumor tissues from nasopharyngeal cancer patients and lung cancer patients by immunohistochemical staining. Preliminary results showed that normal mucosal epithelium in nasopharynx and lung contains high levels of phase I and phase II detoxification enzymes from the cytochrome P450 (CYP) and glutathione-S-transferase (GST) families. There was, however, a lack or weak enzyme expression in the tumor tissues from NPC or lung cancer. We hypothesize that a lack of these enzymes occasionally in some epithelial cells in the nasopharyngeal mucosa will result in a lack of protection for carcinogen insults thus gradually resulting in the tumor development as NPC in the enzyme negative cells giving rise to NPC and lung cancer.
  1. Development of gene transfectant cell lines carrying carcinogen detoxification enzyme genes
By gene transfection technique, we have successfully derived a number of transfectant cell lines containing CYP and GST genes from detoxification enzyme gene negative immortalized nasopharyngeal cell lines. After transfection and selection process, these transfectant cell lines were tested for transcript expression of detoxification enzyme genes by RT-PCR. All cell lines have substantial enhancement of detoxification enzyme gene expression after transfection. At present, these transfectant cell lines are planned in carcinogen challenge experiments to see if they can protect the molecular and genetic damages induced by the carcinogens.
  1. Regulating agents for detoxification enzyme in immortalized NP cell lines
Different compounds extracted from vegetables and fruits can regulate the expression and activity of carcinogen detoxification enzymes and could exert their anti-cancer effect by this detoxification enzyme induction effect. In this part of the study, purified isothiocyanates, polyphenols or anti-oxidants are tested for their ability in immortalized NP cell lines to induce or suppress detoxification enzymes. Preliminary results showed that a number of isothiocyanates and flavonoids can substantially induce a high level of RNA expression of phase II GST enzymes but down-regulate phase I CYP enzymes. Such results will path the way to carcinogen challenge experiments to see if induction of these enzymes by these agents can protect mucosal epithelial cell lines from genetic damages imposed by a variety of carcinogens.

IIB Research project funding support

Annual funding support is obtained from Center for NPC Research through NPC Area of Excellence Grant enabling various projects in the area of NPC to be successfully carried out in the Unit in QEH.

IIC Publications arising from the above research projects

Three postgraduate students studying for UK Edinburgh Napier University Master of Biomedical Science Degree Course were recruited in our department to study the inducing effects of detoxification enzyme expression by purified agents found in vegetables and fruits. They have completed the research projects and the following Master theses reporting their findings have passed the assessment of the University Degree Assessment Committee:-

1. Cheng Miu-Chi, Maggie.  The effects of Anti-Oxidant and Polyphenolic Compounds in the expression of xenobiotic detoxification enzymes in nasopharyngeal and gastrointestinal cell lines. Edinburgh Napier University U.K. Master of Biomedical Science Thesis, 2013.
2. Lee Pui Han Ewina.  The effect of Indole-3-Carbinol and Isothiocyanate in the expression of xenobiotic detoxification enzymes in nasopharyngeal cell lines. Edinburgh Napier University U.K. Master of Biomedical Science Thesis, 2013.
3. Won, Wai Yuk.  Regulation of expression of xenobiotic detoxification enzymes in nasopharyngeal cell lines by flavonoids and their analogues. Edinburgh Napier University U.K. Master of Biomedical Science Thesis, 2013.

An abstract reporting the tissue expression of detoxification enzymes in nasopharyngeal and nasopharyngeal cancer biopsy tissues was accepted in the Hong Kong International Cancer Congress (November, 2013).

4. Yuen-Ping Leung, Roger K.C. Ngan, Dora L.W. Kwong, Victor W. L. Tang, Loretta Tse, Victor W.S. Ma, Timothy T.C. Yip.  The expression of carcinogen detoxification enzymes in nasopharynx & nasopharyngeal cancer. Proceedings of the Hong Kong International Cancer Congress 2013 (Abstract).