AbstractsBiology & Animal Science

Lung cancer has accounted for the most deaths from cancer (19.2% of all cancer deaths) in registered cancer cases in New Zealand. At present lung cancer treatment is inadequate, as patients treated with the front-line drugs, such as gemcitabine, rapidly develop drug resistance by decreasing cellular accumulation and/or avoiding apoptosis. Fucoxanthin (FUX), extracted from edible seaweed such as Undaria pinnatifida, has recently been reported to inhibit membrane drug efflux transporters (ABC transporters) and induce apoptosis in various cancer cell lines. Previous studies in AUT have defined FUX extracted from New Zealand Undaria pinnitifida with anti-cancer properties by using in vitro cell models. FUX has been reported to have few adverse effects in some animal models. We hypothesize that FUX may be a safe sensitizer to reverse gemcitabine resistance in lung cancer cells by increasing cellular accumulation of gemcitabine. The primary objective of this study was to assess the potential effects of FUX to reverse gemcitabine resistance in human lung cancer cell lines. The secondary objective of current study is to investigate the mechanisms of FUX actions if FUX may potentiate gemcitabine sensitivity. The third objective of this study is to evaluate the effects of FUX on modifying gemcitabine toxicity in two typical normal human cell lines. Several types of human cell lines were used in this study including a lung carcinoma cell line A549, and two typical normal human cell lines embryonic kidney cell HEK293 and adult dermal fibroblasts (HDFa). Anti-proliferative effects were determined by 48-hr and 72-hr MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays. As a single agent, either gemcitabine or FUX showed concentration-dependant inhibition of lung cancer proliferation in 72-hr MTT assays, with IC50 values of 9nM and 13μM, respectively. FUX increases gemcitabine sensitivity in an NSCLC cell line, A549 cell in a time and concentration dependant manner. Indeed, the 72-hr IC50 value for gemcitabine was only 3.9nM in the presence of 8μM FUX, which was decreased by 59% when comparing with control (P< 0.05). More importantly, FUX has no apparent effects on gemcitabine toxicity in two typical cell lines representing normal human tissues. It would be expected that FUX may represent a unique sensitizer, which may turn a less effective anti-cancer drug into an exceptional one. To elucidate the mechanisms of action of FUX, it is necessary to carry out a mechanistic study to investigate if FUX changes the intracellular gemcitabine accumulation in A549 cells. To determine gemcitabine in A549 cellular homogenates, an HPLC method has been developed and validated. In this study, while gemcitabine cannot be separated sufficiently from the cellular interferences using a conventional C18 column, aphenyl-hexyl column was found to be efficient to achieve better separation for quantitation of gemcitabine. This is because that separation using the phenyl column is conducted via the π electron, which in this case…