| Summary: | 碩士 === 中華醫事科技大學 === 醫學檢驗生物技術系碩士班 === 103 === Drug resistance remains a major clinical challenge for cancer treatment. P-glycoprotein is responsible for decreased drug accumulation in multidrug-resistant cells and often mediates the development of resistance to anticancer drugs, such as doxorubicin. Lobeline, a piperidine alkaloid, which is produced by Lobelia inflata (family Lobeliaceae) and several other Lobelia species, stimulates chemoreceptors in carotid and aortic bodies, and then exerts reflection of respiratory center. In 2008, Ma et al have mentioned that lobeline could sensitize resistant tumor cells at non-toxic concentration by increasing the accumulation of doxorubicin. Here, we aim to investigate whether lobeline could sensitize doxorubicin resistant cancer cells.
The human doxorubicin resistant uterine sarcoma cells (MES-SA/Dx5 cells) were doxorubicin induced P-gp over-expressed MDR sublines of human uterine carcinoma MES-SA cells respectively. The MES-SA/Dx5 cells expressing high levels of P-gp were treated with different doxorubicin concentrations in the presence or absence of lobeline. Cell suppression was evaluated by MTT. We performed colony formation assay to evaluate tumorigenicity. To study the effects of lobeline, we used real-time PCR, and western blot to determine the expression of MDR1 in MES-SA or MES-SA/Dx5 treated with lobeline, respectively. Rhodamine 123 accumulation assay has been used to evaluate the function of P-glycoprotein after treatment of lobeline.
Our results showed that lobeline had low toxicity in MES-SA and MES-SA/Dx5, evaluated by MTT assay. But lobeline had significant suppression effect in MES-SA/Dx5 treated with doxorubicin, compared to MES-SA. MTT assay showed that after treatment with 10 and 20 µM doxorubicin for 24 h, the survival rates of MES-SA/Dx5 cells were 77.91 ± 3.4% and 73.4 ± 7%, while treated in combination with 50 µM lobeline, the cell survival rates were 64.96 ± 11% and 57.83 ± 7.2 %, respectively (P < 0.05). When we treated MES-SA/Dx5 with lobeline at 50 µM, the suppression of MDR1 mRNA was about 39% on the third day after treatment. The P-gp expression was suppressed 49.92%. Lobeline increased intracellular rhodamine 123 accumulation by 1.3 folds in MES-SA/Dx5 cells, when treated with 50μM, compared with the control. Besides, lobeline also slightly suppressed the intracellular calcium concentration, compared with verapamil.
The major drawbacks associated with doxorubicin therapy are the dose-limiting toxicity and development of drug resistance, which warrants innovative strategies that can ensure the optimal use of this frontline chemotherapeutic agent in clinic. The results showed lobeline might have the potential to treat the drug resistant cancer cells combined with anticancer drug. We will use xenograft animal model to clarify the efficacy of lobeline in future, the confirmation of the synergistic effect of doxorubicin and lobeline in this clinically relevant model signifies the therapeutic potential of the synergism.
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