Summary: | 碩士 === 弘光科技大學 === 生物科技研究所 === 105 === Esophageal cancer is the sixth leading cause of cancer deaths worldwide with a mortality rate of 87.8%. There is currently no effective treatment for esophageal cancer due to a lack of appropriate medications and drug resistance and side effects resulting from chemotherapy drugs; thus, there is an urgent need for the development of new medications. Rutaecarpine (RTP) is a type of quinazolinocarboline and an important alkaloid from the Chinese medicinal herb Evodia rutaecarpa. Many studies have shown that RTP has cardiovascular protective, anti-inflammatory, anti-proliferative. However, no research has been conducted on the ability of RTP to induce apoptosis in esophageal cancer cells and its mechanism remains unclear. Therefore, this study investigated the issue using cells and xenograft models.
In the cell model, CE81T/VGH human esophageal squamous-cell carcinoma cells were treated with various concentrations of RTP (5, 10, and 20 μM). Cisplatin (cis-diamminedichloroplatinum (II), CDDP), a chemotherapy drug, was treated as the positive control group. The cell cycle and cell apoptosis were analyzed. The expression of proteins p53, Bax (Bcl-2-associated X), and Bcl-2 (B-cell lymphoma 2) was identified using Western blot. In the animal model, a xenograft test was conducted on nude mice (BALB/cAnN) treated with low dose RTP (25 mg/kg body weight /twice weekly/p.o), high dose RTP (75 mg/kg body weight/twice weekly/p.o), or CDDP (5 mg/kg body weight/twice weekly/i.p). The animals were sacrificed and analyzed after six weeks.
The cell model results indicated that RTP significantly inhibited the proliferation of esophageal squamous-cell carcinoma cells and induced apoptosis, which was dose- and time-dependent (P<0.05). Further investigation showed that RTP significantly increased p53 protein expression, induced Bax, and inhibited Bcl-2 expression (P<0.05). It is supposed that RTP can induce the apoptosis of esophageal squamous-cell carcinoma cells by increasing the expression of p53 and Bax proteins and inhibiting Bcl-2 protein.
The animal model results indicated that tumor tissue volume and weight were significantly reduced in the groups with high dosage RTP and CDDP treatments (P<0.05). The expression of p53 and Bax was significantly increased and the expression of Bcl-2 was reduced in the groups treated with low dosage RTP, high dosage RTP, and CDDP (P<0.05). These results are similar to those in the cell experiment. Further analysis showed that low and high dosage RTP and CDDP treatment increased the expression of caspase-9 and caspase-3 proteins (P<0.05). Moreover, RTP significantly inhibited the expression of proliferating cell nuclear antigen (PCNA) in tumor tissue (P<0.05). As such, these findings confirmed the results obtained in the cell experiment.
Furthermore, this study also analyzed the concentrations of blood urea nitrogen (BUN) and creatinine (Cre) in blood serum, red blood cells, hemoglobin, hematocrit, and mean corpuscular hemoglobin to examine whether RTP had nephrotoxicity and haematological toxicity. The results indicated that there were no significant differences between the control group and the groups treated with high and low dosage RTP (P>0.05), whereas in the group treated with CDDP, BUN and Cre concentrations significantly increased (P<0.05). With regard to the blood test, there were no significant differences between the control group and the groups treated with high and low dosage RTP (P>0.05). This shows that the RTP dosages used in this study did not cause nephrotoxicity or haematological toxicity. However, its inhibiting effect on esophageal squamous-cell carcinoma cells was similar to that of CDDP.
Taken together results showed that RTP increases p53 and Bax proteins, inhibits Bcl-2 protein, and activates caspase-9 and caspase-3 proteins, inducing the apoptosis of esophageal squamous-cell carcinoma cells and inhibiting tumor growth. These findings suggest that the RTP increases the expression of protein p53 and induces apoptosis via an intrinsic pathway. However, further research is needed to determine its exact mechanism.
|