Investigate the Molecular Mechanism of Nitroglycerin to Enhance Chemotherapeutic Drug Cisplatin and Pemetrexed-Induced Cytotoxicity via Down-Regulation of Thymidylate Synthase Expression in Human Non-Small Cell Lung Cancer Cells = 探討硝酸甘油藉由降低胸腺嘧啶合成酶表現進而增加化療藥物順鉑與愛寧達毒殺人類非小細胞肺癌細胞的分子機轉

Lung cancer is one of the leading causes of cancer-related deaths in Taiwan and worldwide, of which more than 85% are non-small cell lung cancer (NSCLC), mainly because of the lack of effective systemic treatment and rapid development of resistance to chemotherapy. The current first-line therapeutic option for patients with advanced NSCLC includes chemotherapy with a platinum-containing compound such as cisplatin or carboplatin in combination with a second- or third-generation cytotoxic agent. The multitargeted antifolate pemetrexed (Alimta) is approved as a single agent in second-line treatment of patients with locally advanced or metastatic NSCLC after earlier chemotherapy. Nitroglycerin (NTG), nitric oxide-donating drug, may decrease hypoxia and increase tumor blood flow and consequently drug delivery. Thymidylate synthase (TS) is an essential enzyme for the de novo synthesis of dTMP; studies show that cisplatin or pemetrexed-resistant carcinomas exhibit high levels of TS expression. Our study illustrates for the first time that nitroglycerin down-regulated TS expression and AKT activation in NSCLC cells. Compared to a single agent alone, nitroglycerin combined with cisplatin resulted in cytotoxicity and cell growth inhibition synergistically in NSCLC cells. In this study, we will plan to explore how nitroglycerin to down-regulate the AKT activation and TS expression in chemotherapeutic drug (cisplatin and pemetrexed)-exposed NSCLC cells. Moreover, we have established pemetrexed-resistant A549 lung cancer sublines. All three pemetrexed-resistant A549 sublines expressed more TS than the parental cells. Therefore, we will use these pemetrexed-resistant A549 sublines to understand the physiological effect of nitroglycerin -mediated TS down-regulation to enhance pemetrexed sensitivity. Examine the role of TS in nitroglycerin and pemetrexed-mediated anti-tumor activity in animal model. The final goal of this project is to understand the how the nitroglycerin to modulate TS expression, and its role in synergistic cytotoxic effects in chemotherapeutic drug (cisplatin and pemetrexed)-treated NSCLC cell lines. We elucidate that these observations may provide strong evidence for an experimental rationale to use nitroglycerin as part of combined therapy with chemotherapeutic agents in a variety of clinical settings for NSCLC, including reducing the dosage of chemotherapeutic agents and side effects in NSCLC cancer patients.