Nitroglycerin may increase response to docetaxel and cisplatin in murine syngraft solid cancer models via reduction of HIF-1α, P-gp, and phosphorylated Akt and via increase in activated p53 in tumor tissues.
Authors: Hiroyasu Yasuda, Katsutoshi Nakayama, Masanori Asada, Tomohiro Kaneta, Takahiko Sasaki, Motoki Yoshida, Kazuhiro Yanagihara, Mutsuo Yamaya, Yukimasa Hatachi, Akiko Fukuhara, Masanori Fukushima
Journal: Cancer Research (2008)

2045   [ Introduction ] Nitroglycerin (GTN), a nitric oxide (NO) donor, has been reported to increase response to anticancer drugs in non-small cell lung cancer. However, the precise mechanism of nitroglycerin on improvement of chemosensitivity in solid cancers remains unclear.  [ Experimental Design ] Lewis lung carcinoma (LLC) cells and colon-26 cells were subcutaneously inoculated to six-week-old C57BL6 mice and Balb/c mice, respectively. When transplanted tumors grew to approximately 100 mm 3  in tumor volume, animals were randomized to ten groups {(1) control, (2) 0.02 mg/kg GTN, (3) 0.2 mg/kg GTN, (4) 50 mg/kg diltiazem (DTZ), (5) 10 mg/kg verapamil, (6) anticancer drug, 7.0 mg/kg docetaxel or 3.5 mg/kg cisplatin, (7) :(2)+(6), (8) :(3)+(6), (9) :(4)+(6), and (10) :(5)+(6)}. Pretreatment, one of five from (1) to (5) was performed four times a week (D1, D2, D4, and D5) and docetaxel or cisplatin solution dissolved in PBS was further administered into the mice 60 minutes after pretreatment twice a week (D2 and D5). The experiments were performed for two weeks. In groups (1), (2), (3), and (4), mRNA and proteins of intratumor hypoxia-inducible factor-1α (HIF-1α), p53, activated p53, P-glycoprotein (P-gp), vascular endothelial growth factor (VEGF), Akt, phosphorylated Akt, and β-actin were measured. In groups (1), (2), and (3), the influence of nitroglycerin on intratumor hypoxic area was assessed by [F18]FRP170, 1-(2-fluoro-1-[hydroxyl- methyl]ethoxy)-methyl-2-nitroimidazole, a new PET tracer for imaging hypoxia. Intratumor microvascular density (IMD) was rated by immunohistochemical study using von Willebrand factor in groups (1) and (2). Antitumor activity of natural killer (NK) cells in groups (1) and (2) was measured with the  51 Cr releasing method. In the experiment using cisplatin, Intratumor cisplatin concentrations were measured in groups (6), (7), and (8).  [ Results ] The tumor growth curves of group (8) were lowest in both the experiments using docetaxel and cisplatin. GTN and DTZ did not change HIF-1α mRNA, but reduced VEGF and mdr-1 mRNA 1 hr after injections. GTN and DTZ significantly reduced HIF-1α and phosphorylated Akt 1 hr after injection and also reduced VEGF and P-gp after 24 hrs after injection in tumor tissues. GTN significantly increased intratumor activated p53 protein, but DTZ did not. GTN did not increase either IMD or NK cell antitumor activity. GTN significantly decreased the distribution of hypoxic area in dose-dependent manner. However, GTN did not increase intratumor cisplatin concentration.  [ Conclusions ] GTN may increase response to docetaxel and cisplatin in murine syngraft solid cancer models made of LLC cells and colon-26 cells  via reduction of HIF-1α, phosphorylated Akt, and P-gp and via an increase in activated p53 in tumor tissues.