Topoisomerase inhibitor upregulates MICA/B expression in breast cancer cells through ATM/ATR and NF-κB pathway / 北京大学学报(医学版)

OBJECTIVE@#To investigate the effects of chemotherapeutic agents widely used in clinical practice on major histocompatibility complex class I-related chain A and B (MICA/B) expression in breast cancer cells, and to explore the molecular mechanisms involved.@*METHODS@#We examined MICA/B mRNA and surface protein expressions in breast cancer cells treated with chemotherapeutic agents by real-time RT-PCR and flow cytometry respectively. The blocking effects of ataxia telangiectasia mutated and Rad3-related kinase (ATM/ATR) inhibitor caffeine and nuclear factor κB (NF-κB) inhibitor pynolidine dithiocarbamate (PDTC) on etoposide-upregulated MICA/B mRNA and surface protein expressions were investigated. Electrophoretic mobility shift assay (EMSA) was taken to investigate whether etoposide enhanced the binding of NF-κB to MICA/B gene promoter.@*RESULTS@#Three topoisomerase inhibitors etoposide, camptothecin and doxorubicine upregulated MICA and MICB mRNA expressions in breast cancer cell MCF-7. Comparing to no-drug-treated cells, MICA mRNA levels increased to (1.68±0.17), (2.54±0.25) and (3.42±0.15) fold, and levels of MICB mRNA increased to (1.82±0.24), (1.56±0.05) and (5.84±0.57) fold respectively in cancer cells treated by etoposide at the concentrations of 5, 20 and 100 μmol/L (P<0.05). MICA and MICB mRNA levels also increased significantly when MCF-7 cells were incubated with camptothecin or doxorubicine at the specific concentrations (P<0.05). MICB mRNA expression also increased slightly in another breast cancer cell SK-BR-3 treated by topoisomerase II inhibitors etoposide and camptothecin (P<0.05). Furthermore, etoposide and camptothecin upregulated MICA/B surface protein expression in MCF-7 cells (P<0.05), and the upregulation was found in both living and apoptotic cells. Our study showed that etoposide induced-MICA/B expression in MCF-7 was inhibited by caffeine at different concentrations. When cancer cells were treated by caffeine with 1, 5 and 10 mmol/L, MICA mRNA levels decreased from (3.75±0.25) to (0.89±0.05), (0.81±0.02) and (0.48±0.04) fold respectively (P<0.001), and MICB mRNA levels decreased from (6.85±0.35) to (1.36±0.13), (0.76±0.06) and (0.56±0.03) fold (P<0.05), while MICA/B protein levels decreased from (3.42±0.05) to (1.32±0.03), (1.21±0.06) and (1.14±0.03) fold (P<0.001), indicating that etoposide-induced MICA/B expression was inhibited by ATM/ATR inhibitor. Similarly, NF-κB inhibitor PDTC also inhibited MICA/B mRNA and protein expressions induced by etoposide significantly when MCF-7 cells were incubated with PDTC at the concentrations of 10, 50 and 100 μmol/L (P<0.05), indicating that NF-κB was also involved in this process. EMSA showed that the binding of NF-κB to MICA/B promoter enhanced in MCF-7 cells after etoposide treatment.@*CONCLUSION@#Topoisomerase inhibitor increased MICA/B mRNA and protein expressions in breast cancer cells, indicating that chemotherapeutic agents might increase the recognizing and killing ability of immunocytes to breast cancer cells. ATM/ATR and NF-κB pathways might be involved in it.

Metformin synergistically enhances antiproliferative effects of cisplatin and etoposide in NCI-H460 human lung cancer cells / Metformina sinergicamente potencializa os efeitos antiproliferativos de cisplatina e etoposideo em linhagem de celulas de cancer humano de pulmao NCI-H460

OBJECTIVE: To test the effectiveness of combining conventional antineoplastic drugs (cisplatin and etoposide) with metformin in the treatment of non-small cell lung cancer in the NCI-H460 cell line, in order to develop new therapeutic options with high efficacy and low toxicity. METHODS: We used the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and calculated the combination index for the drugs studied. RESULTS: We found that the use of metformin as monotherapy reduced the metabolic viability of the cell line studied. Combining metformin with cisplatin or etoposide produced a synergistic effect and was more effective than was the use of cisplatin or etoposide as monotherapy. CONCLUSIONS: Metformin, due to its independent effects on liver kinase B1, had antiproliferative effects on the NCI-H460 cell line. When metformin was combined with cisplatin or etoposide, the cell death rate was even higher. .

OBJETIVO: Testar a eficácia da combinação terapêutica de antineoplásicos convencionais (cisplatina e etoposídeo) com metformina em linhagem celular NCI-H460 de câncer de pulmão não pequenas células, a fim de desenvolver novas possibilidades terapêuticas com eficácia superior e reduzida toxicidade. MÉTODOS: Foi utilizado o ensaio de brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazólio (MTT) e calculado o índice de combinação dos fármacos estudados. RESULTADOS: Observamos que o uso de metformina em monoterapia reduziu a viabilidade celular metabólica da linhagem de células estudada. O uso de metformina em combinação com cisplatina ou etoposídeo foi sinérgico e superior à monoterapia com cisplatina ou etoposídeo. CONCLUSÕES: A metformina, devido às suas ações independentes em liver kinase B1, apresentou atividade antiproliferativa na linhagem NCI-H460 e, em combinação com cisplatina ou etoposídeo, ampliou a taxa de morte celular. .

Apoptosis is the most efficient death-pathway in tumor cells after topoisomerase II inhibition

To compare the efficiency of apoptosis and other modes of cell death in killing tumor cells after the induction of DNA damage by topoisomerase inhibitors like etoposide. This study was carried out in the Tumor Biology Department, National Cancer Institute, Cairo University, Cairo, Egypt, from September 2005 to August 2007. The breast cancer MCF7, the cervix carcinoma, human cervical adenocarcinoma [Hela], and the brain tumor U251 cell lines were exposed to etoposide. Apoptosis was detected using the flow cytometry and the DNA ladder formation methods. Cell viability was determined by a colorimetric assay, and the residual DNA double-strand breaks [dsb] were measured by gel electrophoresis. The Hela cells were the most, the MCF7's were moderately, whereas the U251's were the least sensitive to etoposide. Apoptosis was detected only in Hela cells whereas the other 2 cell lines showed a very low level of apoptosis [only 3% increase above the control cells]. At equitoxic drug concentrations [namely IC50], the Hela cells showed the lowest amount of non-repaired DNA dsb, and the MCF7's showed the highest amount, whereas the U251 cells showed a moderate amount. These results indicate that although other modes of cell death exist, apoptosis is the most efficient and requires lower drug concentrations and fewer numbers of non-repaired dsb to give the same killing effect. Clinically, this means that tumors that can execute apoptosis may require lower doses of topoisomerase inhibitors than those that lost the ability to exercise apoptosis

Etoposide-induced Smad6 expression is required for the G1 to S phase transition of the cell cycle in CMT-93 mouse intestinal epithelial cells

The inhibitory Smad6 and Smad7 are responsible for cross-talk between TGF-beta/bone morphogenic protein (BMP) signaling and other cellular signaling pathways, as well as negative feedback on their own signaling functions. Although inhibitory Smads are induced by various stimuli, little is known about the stimuli that increase Smad6 transcription, in contrast to Smad7. Here we demonstrate that etoposide, which induces double strand breaks during DNA replication, significantly up-regulates the transcription of the Smad6 gene in CMT-93 mouse intestinal cells by increasing specific DNA binding proteins. In addition, endogenous inhibition of the Smad6 gene by RNAi interference led to transient accumulation of G1 phase cells and reduction in incorporation of bromodeoxyuridine (BrdU). These findings strongly suggest that Smad6 plays a distinct role in the signaling of etoposide-induced DNA damage.

Distinct Patterns of Cleavage and Translocation of Cell Cycle Control Proteins in CD95-induced and p53-induced apoptosis

Apoptotic cell death induced by p53 occurs at a late G1 cell cycle checkpoint termed the restriction(R)point, and it has been proposed that p53-induced apoptosis causes upregulation of CD95. However, as cells with defective in CD95 signaling pathway are still sensitive to p53-induced apoptosis, CD95 cannot be the sole factor resulting in apoptosis. In addition, unlike p53-induced apoptosis, the relationship between CD95-mediated apoptosis and the cell cycle is not clearly understood. It would there-fore be worth investigating whether CD95-mediated cell death is pertinent with p53-induced apoptosis in view of cell cycle related molecules. In this report, biochemical analysis showed that etoposide-induced apoptosis caused the induction and the nuclear translocation of effector molecules involved in G1 cell cycle checkpoint. However, there was no such translocation in the case of CD95-mediated death. Thus, although both types of apoptosis involved caspase activation, the cell cycle related proteins responded differently. This argues against the idea that p53-induced apoptosis occurs through the induction of CD95/CD95L expression.

Sox-4 is a positive regulator of Hep3B and HepG2 cells' apoptosis induced by prostaglandin (PG)A2 and 12-PGJ2

We reported earlier that expression of Sox-4 was found to be elevated during prostaglandin (PG) A2 and delta(12)-PGJ(12) induced apoptosis in human hepatocarcinoma Hep3B cells. In this study, the role of Sox-4 was examined using human Hep3B and HepG2 cell lines. Sox-4 induction by several apoptotic inducer such as A23187 (Ca(2+) ionophore) and etoposide (topoisomerase II inhibitor) and Sox-4 transfection into the cells were able to induce apoptosis as observed by the cellular DNA fragmentation. Antisense oligonucleotide of Sox-4 inhibited the induction of Sox-4 expression and blocked the formation of DNA fragmentation by PGA(2) and delta(12)-PGJ(12) in Hep3B and HepG2 cells. Sox-4-induced apoptosis was accompanied with caspase-1 activation indicating that caspase cascade was involved in this apoptotic pathway. These results indicate that Sox-4 is involved in Hep3B and HepG2 cells apoptosis as an important apoptotic mediator.

The Levels of MDM2 Protein Are Decreased by a Proteasome-Mediated Proteolysis Prior to Caspase-3-Dependent pRb and PARP Cleavages

MDM2 is a substrate of caspase-3 in p53-mediated apoptosis. In addition, MDM2 mediates its own ubiquitination in a RING finger-dependent manner. Thus, we investigated whether MDM2 is degraded through a ubiquitin-dependent proteasome pathway in the absence of p53. When HL-60 cells, p53 null, were treated with etoposide, MDM2 was markedly decreased prior to caspase-3-dependent retinoblastoma tumor suppressor protein (pRb) and poly (ADP- ribose) polymerase (PARP) cleavages. Moreover, down-regulation of MDM2 level was not coupled with its mRNA down-regulation. However, the level of MDM2 was partially restored by proteasome inhibitors such as LLnL and lactacystin, even in the presence of etoposide. Our results suggest that, in the p53 null status, MDM2 protein level is decreased by proteasome-mediated proteolysis prior to caspase-3-dependent PARP and pRb cleavages.

Early results evaluating the efficacy and toxicity of adriamycin, vincristine and etoposide Ave in the management of childhood hodgkin's disease

This study aimed to evaluate efficacy and toxicity of adriamycin, vincristine and etoposide in the management of childhood Hodgkin's disease as a salvage and first line therapy as well as limiting the use of involved field radiotherapy to partial responders to avoid unnecessary complications of radiotherapy children. Thirty-six patients with Hodgkin's disease were included in this study, twenty- four had no previous treatment and twelve were previously treated with either C-MOPP or Chl-VPP [five of them had refractory disease and the remaining seven attained a complete remission but relapsed later]. All patients were treated with adriamycin 30 mg/m2, vincristine 1.4 mg/m2 and etoposide 100 mg/m2 D1 and D15 repeated every 28 days for six cycles. Partial responders [PR] were subjected to a field radiation treatment after three cycles of chemotherapy [20 Gy/ten treatments/two weeks]. At the end of the six cycles of chemotherapy, all patients were in a complete remission [CR]. All the previously untreated patients were in a complete remission after a median follow up of 15.5 months. The relapse free survival in previously treated patients was 58.3% after a median follow up of 14 months. The relapse free survival for the whole group was 86.7% after a median follow up of 15 months

Etoposide y displatino (EP) en el tratamiento de tumores germinales de testículo / Etoposide and cisplatin (EP) in the treatment o germinal testicular tumors: factors which affect tumoral reaction to treatment

Entre 1986 y 1990 se estudió un grupo de 51 enfermos con tumores germinales del testículo, tratados con etoposide y cisplatino, con el propósito de conocer la reacción tumoral a este esquema de tratamiento y establecer que factores clínicos e histopatológicos influyen en ella