Synergism between rViscumin and cisplatin is not dependent on ERCC-1 expression

Phytohemagglutinin from Phaseolus vulgaris enhances the lung cancer cell chemotherapy sensitivity by changing cell membrane permeability

Chemotherapy is still a prevalent strategy for clinical lung cancer treatment. However, the inevitable emerged drug resistance has become a great hurdle to therapeutic effect. Studies have demonstrated that the primary cause of drug resistance is a decrease in the chemotherapeutic medicine concentration. Several lectins have been confirmed to be effective as chemotherapy adjuvants, enhancing the anti-tumor effects of chemotherapy drugs. Here, we combined phytohemagglutinin (PHA), which has been reported possess anti-tumor effects, with chemotherapy drugs Cisplatin (DDP) and Adriamycin (ADM) on lung cancer cells to detect the sensitivities of PHA as a chemotherapy adjuvant. Our results demonstrated that the PHA significantly enhanced the sensitivity of lung cancer cells to DDP and ADM, and Western blot showed that PHA combined with DDP or ADM enhance cytotoxic effects by inhibiting autophagy and promoting apoptosis. More importantly, we found PHA enhanced the chemotherapeutic drugs cytotoxicity by changing the cell membrane to increase the intracellular chemotherapeutic drugs concentration. Besides, the combination of PHA and ADM increased the ADM concentration in the multidrug-resistant strain A549-R cells and achieved the drug sensitization effect. Our results suggest that PHA combined with chemotherapy can be applied in the treatment of lung cancer cells and lung cancer multidrug-resistant strains, and provide a novel strategy for clinical tumor chemotherapy and a new idea to solve the problem of drug resistance in clinical lung cancer.

Cytotoxic effect of mistletoe (Viscum album L.) extract on Jurkat cells and its interaction with doxorubicin

Mistletoe preparations are frequently used by cancer patients because of their ability to stimulate the immunity and to improve the quality of life. Moreover mistletoe and its active substances (especially lectins) possess cytotoxic effect on various cancer cell lines. However, only little is known about its interaction with anticancer drugs. Therefore the cytotoxic and apoptosis-inducing effects of aqueous mistletoe extract (VA) and its interaction with doxorubicin (DOXO) were investigated in Jurkat cells. The results show that VA extract as well as DOXO exert cytotoxic effects on Jurkat cells in a dose-dependent manner. Cytotoxicity of DOXO was much stronger (LC(50) = 11.68 ng/mL) than that of VA extract (LC(50) = 35.67 microg/mL). Their combination led to synergism only at those concentrations that were highly cytotoxic alone. Both substances (alone and in combination) induced DNA fragmentation in Jurkat cells. In conclusion, an aqueous extract prepared from mistletoe tops exerted cytotoxic and apoptosis-inducing effects on Jurkat cells alone as well as in combination with DOXO.

Excision repair cross-complementation group 1 (ERCC1) in platinum-based treatment of non-small cell lung cancer with special emphasis on carboplatin: a review of current literature

BACKGROUND

Patients diagnosed with advanced non-small cell lung cancer have a dismal prognosis and are often relative resistant to chemotherapy. A need for markers has emerged based on tumour biology in order to predict which patients will respond to treatment. Excision repair cross-complementation group 1 (ERCC1) has shown potential as a predictive marker in patients with NSCLC treated with cisplatin-based chemotherapy. Carboplatin has gained widespread use in the treatment of advanced NSCLC and its mechanisms of action are likely similar to that of cisplatin.

MATERIALS AND METHODS

A literature review on ERCC1 was conducted as predictor in NSCLC patients receiving platinum-based treatment with emphasis on carboplatin. English language publications from January 1996 to February 2008 were eligible and data on methodology and outcome were recorded.

RESULTS

Eight preclinical articles, 25 clinical articles and 1 clinical abstract were identified. Laboratory methods were mainly RT-PCR (reverse transcriptase polymerase chain reaction) or immunohistochemistry (IHC) for expression of ERCC1. Preclinical studies pointed towards similar mechanisms of chemotherapy-resistance among platinum compounds. A statistically significant benefit in outcome was found among NSCLC patients, who received adjuvant treatment, and had low-ERCC1 expression. Advanced NSCLC patients treated with cisplatin showed improved response rates (RR) but no difference in other endpoints. Studies on advanced NSCLC patients treated with carboplatin were sparse, heterogeneous and small thus reporting varying results.

CONCLUSION

The literature on advanced NSCLC patients treated with carboplatin or cisplatin are dominated by small and heterogeneous patient populations and yielded different results. No firm conclusions can be drawn on carboplatin based on the current literature. Research on the development of a reliable methodology is warranted followed by validation in large, prospective, randomized trials as ERCC1 may possibly play an important role as tumour marker in tailored chemotherapy for NSCLC.

Regulation of DNA repair gene expression in human cancer cell lines

Although most advanced cancers are incurable, the majority of testicular germ cell tumors can be cured using cisplatin-based combination chemotherapy. The nucleotide excision repair (NER) pathway removes most DNA adducts produced by cisplatin, and the low levels of NER in testis tumor cells may explain why these cancers are curable. Three NER proteins: ERCC1, XPF, and XPA, are present at low levels in testis tumor cell lines, and addition of these proteins to protein extracts of testis tumor cells increases their in vitro DNA repair capacity to normal levels. The aim of this study was to identify the mechanism responsible for the low levels of these DNA repair proteins. The levels of the mRNA transcripts for ERCC1, XPF, and XPA were measured in a panel of 14 different human cancer cell lines, using real-time PCR. Three ERCC1 splice variants were identified and quantitated. Three alternative transcription start points (TSPs) were identified for ERCC1 but none were testis-specific. The significantly lower levels of ERCC1, XPF, and XPA protein in testis tumor cell lines cannot be explained solely by differences in transcriptional efficiency or mRNA stability. For ERCC1, post-transcriptional control by alternative splicing does not account for the testis-specific low levels of protein expression. Pulse-chase experiments showed that the half-life of ERCC1 protein in a testis tumor cell line was not significantly different to that in a prostate cancer cell line. Taken together, these results suggest that constitutive levels of these DNA repair proteins are controlled at the level of translation.

IGrowth inhibition of human hepatocarcinoma cells induced by Chinese herbs Huqi San and its principal drug mistletoe extracts

AIM: To probe the effect of Chinese herbs, Huqi San (HQS) and its principal drug mistletoe extracts on the growth of human hepatocar-cinoma cell line SMMC-7721 and the levels of intracellular reactive oxygen species (ROS).

METHODS: The proliferation of SMMC-7721 cells inhibited by HQS (0.3125, 0.625, 1.25 g/L), mistletoe polysaccharides (0.625, 1.25, 2.5, 5 g/L) and total alkaloid of mistletoe (3, 6, 12 g/L) at 48, 72 and 96 h were observed by MTT assay. The cell cycle and apoptosis rate of SMMC-7721 cells were examined by flow cytometry. The fluorescent intensity of ROS was observed by laser scanning confocal microscopy.

RESULTS: Both HQS and mistletoe extracts inhibited the proliferation of SMMC-7721 cells in a time- and dose-dependence manner, and the numeric value of absorbance in high-dose group decreased markedly as compared with that in the control group (HQS 72 h: 1.022 ± 0.13 vs 1.207 ± 0.04, P < 0.01; 96 h: 1.235 ± 0.20 vs 1.602 ± 0.05, P < 0.01; mistletoe polysaccharides 48 h: 0.570 ± 0.03 vs 0.744 ± 0.01, P < 0.01; 72 h: 0.803 ± 0.04 vs 1.207 ± 0.04, P < 0.01; 96 h: 0.860 ± 0.13 vs 1.602 ± 0.05, P < 0.01; total alkaloid of mistletoe 72 h: 0.919 ± 0.14 vs 1.233 ± 0.04, P < 0.01; 96 h: 0.701 ± 0.07 vs 1.819 ± 0.04, P < 0.01), expect that at 48 h in HQS and total alkaloid of mistletoe group. After treatment with the drugs for 72 h, the cell populations in the group of mistletoe polysaccharides and total alkaloid of mistletoe increased in G1 phase (81.0%, 86.9% vs 70.0%, P < 0.01) and decreased in G2 and S phase (13.1%, 5.7% vs 16.4%, P < 0.01; 5.9%, 7.4% vs 13.5%, P < 0.01), in comparison with those in the controls. In the group of HQS, the proportion of S-phase cells decreased (1.5% vs 13.5%, P < 0.01) while that of G2-phase ones increased (28.2% vs 16.4%, P < 0.01). However, there was no obvious change in the numbers of G1-phase cells. In addition, all of the three drugs enhanced the apoptosis of SMMC-7721 cells (HQS: 14.8% vs 6.0%, P < 0.01; mistletoe polysaccharides: 11.7% vs 6.0%, P < 0.01; total alkaloid of mistletoe: 6.7% vs 6.0%, P < 0.05). Confocal microscopy showed that the fluorescent intensity declined suddenly and then maintained at a low level almost without fluctuating when the three kinds of drugs were added. However, after the fluorescent intensity was stabile at a baseline, it increased instantly as the total alkaloid of mistletoe was added. Thereafter, it decreased rapidly and maintained at a low level for a period of time. But this phenomenon was not observed when the cells were treated with HQS and mistletoe polysaccharides.

CONCLUSION: HQS, mistletoe polysaccharides and total alkaloid of mistletoe can inhibit the proliferation and promote the apoptosis of SMMC-7721 cells.

Alaternin and emodin with hydroxyl radical inhibitory and/or scavenging activities and hepatoprotective activity on tacrine-induced cytotoxicity in HepG2 cells

The antioxidative and hepatoprotective potentials of two anthraquinones, alaternin (2-hydroxyemodin) and emodin, to scavenge and/or inhibit hydroxyl radicals generated by the Fenton reaction and to protect tacrine-induced cytotoxicity in human liver derived HepG2 cells were evaluated, respectively. The inhibitory activity on hydroxyl radical generated in a cell-free chemical system (FeSO4/H2O2) was investigated by a fluorescence spectrophotometer using a highly fluorescent probe, 2',7'-dichlorofluorescein. The hydroxyl radical scavenging activity was determined by electron spin resonance spectroscopy using 5,5-dimethy-1-pyrroline-N-oxide as hydroxyl radicals trapping agents. Tacrine-induced HepG2 cell toxicity was determined by a 3-[4,5-dimethylthiazole-2yl]-2,5-diphenyltertrazolium bromide assay. Although the scavenging activity of alaternin on hydroxyl radical was similar to that of emodin in dose-dependent patterns, the inhibitory activity exhibited by the former on hydroxyl radical generation was stronger than that of the latter, with IC50 values of 3.05 +/- 0.26 microM and 13.29 +/- 3.20 microM, respectively. In addition, the two anthraquinones, alaternin and emodin showed their hepatoprotective activities on tacrine-induced cytotoxicity, and the EC50 values were 4.02 microM and 2.37 microM, respectively. Silymarin, an antihepatotoxic agent used as a positive control exhibited the EC50 value of 2.00 microM. These results demonstrated that both alaternin and emodin had the simultaneous antioxidant and hepatoprotective activities.