YSY01-A, as a novel proteasome inhibitor, has shown remarkable proliferation inhibitory effect on certain types of tumor cells. However, few studies have reported its effect on non-small cell lung cancer （NSCLC）, and its underlying mechanism remains unknown. In our present study, we aimed to figure out the inhibitory effects as well as the mechanism of proteasome inhibitor YSY01-A against A549 cells both individually and in combination with cisplatin. A549 cell proliferation inhibition was assessed by SRB assay. Its related protein expression levels were determined by western blot assay. Moreover, the change of intracellular cisplatin accumulation was examined by ICP-MS assay. The results suggested that YSY01-A significantly （P〈0.001） inhibited the proliferation of A549 cells （IC50 was 36.2 nM for 72 h） in a concentration-dependent and time-dependent manner. Compared with the negative control group, YSY01-A （60 nM, 48 h） down-regulated PI3K/Akt pathway in A549 cells by increasing the expression level of PTEN （P〈0.01）, and decreasing the expression level of PI3K （P〈0.001） and p-Akt/Akt （P〈0.001）. When combined with cisplatin, YSY01-A of different concentrations （5, 10, 20 nM） could significantly increase the inhibition effects on A549 cells compared with the cisplatin alone treatment, showing a synergistic effect. At the same time, YSY01-A could remarkably block the cisplatin-induced down-regulation of hCTR1 in a concentration-dependent manner and increase cisplatin uptake from 2.01 to 2.47 fold （P〈0.001）. In conclusion, compound YSY01-A could significantly inhibit proliferation of NSCLC A549 cells, showing a strong synergistic effect when combined with cisplatin. Down-regulation of PI3K/Akt pathway might be the mechanism of inhibitory effect of YSY0 l-A, and the combination with cisplatin might increase the expression of CTR1 and intracellular cisplatin accumulation.
Compound SLXM-2, a derivative of cyclophosphamide （CTX）, has shown potent growth-inhibitory effect on tumor cells with low toxicity in previous studies. However, the mechanism of its anti-tumor effect, especially on DNA damage, remains largely unclear. This study investigated the effect of SLXM-2 on the survival time of mice transplanted with the ascitie fluid-type hepatocarcinoma 22 （H22）. We also evaluated the correlation between DNA damaging effect of SLXM-2 and its anti-tumor effect, and to probe the possible molecular mechanism for its effect on H22 cells. The results suggested that SLXM-2 significantly （P〈0.05） prolonged the survival time of mice bearing the ascitic fluid-type H22. Furthermore, SLXM-2 induced DNA damage in a dose-dependent manner in H22 cells. Further investigation revealed that SLXM-2 significantly （P〈0.05） up-regulated the expression levels of a series of DNA damage-related proteins, such as γH2AX （Ser139）, p-Chkl （Ser296）, p-Chk2 （Thr68）, p-p53 （Ser15）, p-p53 （Ser20） and p21, and down-regulated the expression of p-ATR （Ser428） and p-ATM （Ser1981）. In conclusion, SLXM-2 showed a remarkable anti-tumor activity on ascitic fluid-type H22 cells, and its molecular mechanism is related to its DNA damaging effect.
