Tyrosine kinase inhibitor emodin suppresses growth of HER-2/neu-overexpressing breast cancer cells in athymic mice and sensitizes these cells to the inhibitory effect of paclitaxel.
Overexpression of the HER-2/neu proto-oncogene, which encodes the tyrosine kinase receptor p185neu, has been observed in tumors from breast cancer patients. We demonstrated previously that emodin, a tyrosine kinase inhibitor, suppresses tyrosine kinase activity in HER-2/neu-overexpressing breast cancer cells and preferentially represses transformation phenotypes of these cells in vitro. In the present study, we examined whether emodin can inhibit the growth of HER-2/neu-overexpressing tumors in mice and whether emodin can sensitize these tumors to paclitaxel, a commonly used chemotherapeutic agent for breast cancer patients. We found that emodin significantly inhibited tumor growth and prolonged survival in mice bearing HER-2/neu-overexpressing human breast cancer cells. Furthermore, the combination of emodin and paclitaxel synergistically inhibited the anchorage-dependent and -independent growth of HER-2/neu-overexpressing breast cancer cells in vitro and synergistically inhibited tumor growth and prolonged survival in athymic mice bearing s.c. xenografts of human tumor cells expressing high levels of p185neu. Both immunohistochemical staining and Western blot analysis showed that emodin decreases tyrosine phosphorylation of HER-2/neu in tumor tissue. Taken together, our results suggest that the tyrosine kinase activity of HER-2/neu is required for tumor growth and chemoresistance and that tyrosine kinase inhibitors such as emodin can inhibit the growth of HER-2/neu-overexpressing tumors in mice and also sensitize these tumors to paclitaxel. The results may have important implications in chemotherapy for HER-2/neu-overexpressing breast tumors. (+info)
CLIP-170 highlights growing microtubule ends in vivo.
A chimera with the green fluorescent protein (GFP) has been constructed to visualize the dynamic properties of the endosome-microtubule linker protein CLIP170 (GFP-CLIP170). GFP-CLIP170 binds in stretches along a subset of microtubule ends. These fluorescent stretches appear to move with the growing tips of microtubules at 0.15-0.4 microm/s, comparable to microtubule elongation in vivo. Analysis of speckles along dynamic GFP-CLIP170 stretches suggests that CLIP170 treadmills on growing microtubule ends, rather than being continuously transported toward these ends. Drugs affecting microtubule dynamics rapidly inhibit movement of GFP-CLIP170 dashes. We propose that GFP-CLIP170 highlights growing microtubule ends by specifically recognizing the structure of a segment of newly polymerized tubulin. (+info)
The topoisomerase-related function gene TRF4 affects cellular sensitivity to the antitumor agent camptothecin.
Camptothecin is an antitumor agent that kills cells by converting DNA topoisomerase I into a DNA-damaging poison. Although camptothecin derivatives are now being used to treat tumors in a variety of clinical protocols, the cellular factors that influence sensitivity to the drug are only beginning to be understood. We report here that two genes required for sister chromatid cohesion, TRF4 and MCD1/SCC1, are also required to repair camptothecin-mediated damage to DNA. The hypersensitivity to camptothecin in the trf4 mutant does not result from elevated expression of DNA topoisomerase I. We show that Trf4 is a nuclear protein whose expression is cell cycle-regulated at a post-transcriptional level. Suppression of camptothecin hypersensitivity in the trf4 mutant by gene overexpression resulted in the isolation of three genes: another member of the TRF4 gene family, TRF5, and two genes that may influence higher order chromosome structure, ZDS1 and ZDS2. We have isolated and sequenced two human TRF4 family members, hTRF4-1 and hTRF4-2. The hTRF4-1 gene maps to chromosome 5p15, a region of frequent copy number alteration in several tumor types. The evolutionary conservation of TRF4 suggests that it may also influence mammalian cell sensitivity to camptothecin. (+info)
Fractionated administration of irinotecan and cisplatin for treatment of lung cancer: a phase I study.
A combination chemotherapy of irinotecan (CPT-11) and cisplatin (CDDP) has been reported to be active for lung cancer. In the previous trial, however, diarrhoea and leucopenia became the major obstacle for sufficient dose escalation of CPT-11 to improve the treatment outcome. We conducted a phase I study to investigate whether the fractionated administration of CDDP and CPT-11 at escalated dose was feasible and could improve the treatment outcome. Twenty-four previously untreated patients with unresectable non-small-cell lung cancer (NSCLC) or extensive disease of small-cell lung cancer (SCLC) were eligible. Both CDDP and CPT-11 were given on days 1 and 8, and repeated every 4 weeks. The dose of CDDP was fixed at 60 mg m(-2) and given by 1-h infusion before CPT-11 administration. The starting dose of CPT-11 was 40 mg m(-2), and the dose was escalated by an increase of 10 mg m(-2). The maximally tolerated dose of CPT-11 was determined as 60 mg m(-2) because grade 4 haematological or grade 3 or 4 non-haematological toxicities developed in six patients out of 11 patients evaluated. Diarrhoea became a dose-limiting toxicity. The objective response rates were 76% for NSCLC and 100% for SCLC. The recommended dose of CPT-11 and CDDP in a phase II study will be 50 mg m(-2) and 60 mg m(-2) respectively. (+info)
A novel taxane with improved tolerability and therapeutic activity in a panel of human tumor xenografts.
Clinically available taxanes represent one of the most promising class of antitumor agents, despite several problems with their solubility and toxicity. In an attempt to improve the pharmacological profile of taxanes, a new series of analogues was synthesized from 14beta-hydroxy-10-deacetylbaccatin III and tested in a panel of human tumor cell lines. On the basis of the pattern of cytotoxicity and lack of cross-resistance in tumor cell lines expressing the typical multidrug-resistant phenotype, a compound (IDN5109) was selected for preclinical development. A comparative efficacy study of IDN5109 and paclitaxel was performed using a large panel of human tumor xenografts, characterized by intrinsic (seven tumors) or acquired (four tumors) resistance to cisplatin or doxorubicin, including four ovarian, one breast, one cervical, three lung, one colon, and one prostatic carcinoma. Drugs were delivered i.v. according to the same schedule (four times every 4th day). IDN5109 achieved a very high level of activity (percentage tumor weight inhibition >70%; log10 cell kill >1) in all but one of the tested tumors. Compared to paclitaxel, IDN5109 exhibited a significantly superior activity in six tumors (including the four tumors that were resistant to paclitaxel) and a comparable activity against the other five paclitaxel-responsive tumors. Additional advantages of IDN5109 over paclitaxel were also suggested by its toxicity profile. IDN5109 was not only less toxic (maximal tolerated doses were 90 and 54 mg/kg for IDN5109 and paclitaxel, respectively), but it also appeared to be endowed with a reduced neurotoxic potential and an improved profile of tolerability compared to the parent drug. Furthermore, the best antitumor efficacy was often already reached with doses lower than the maximal tolerated dose, suggesting an improved therapeutic index for the new drug. In conclusion, the results support the preclinical interest of IDN5109 in terms of the toxicity profile and of the efficacy with particular reference to the ability to overcome multiple mechanisms of drug resistance. (+info)
Enhanced antitumor activity of 6-hydroxymethylacylfulvene in combination with irinotecan and 5-fluorouracil in the HT29 human colon tumor xenograft model.
6-Hydroxymethylacylfulvene (MGI-114) is a semisynthetic analogue of the toxin illudin S, a product of the Omphalotus mushroom. MGI-114 induces cytotoxicity in a variety of solid tumors in vivo, including the refractory HT29 human colon cancer xenograft. In this study, the potential application of MGI-114 in the treatment of colon cancer was further explored by evaluating the activity of MGI-114 in combination with irinotecan (CPT-11) and 5-fluorouracil (5FU). Groups of 9 nude mice bearing HT29 xenografts were treated with either single agent MGI-114, CPT-11, or 5FU, or MGI-114 in combination with CPT-11 or 5FU. MGI-114 was administered at doses of 3.5 and 7 mg/kg i.p. daily on days 1 through 5, and CPT-11 and 5FU were administered at doses of 50 and 100 mg/kg i.p. on days 1, 12, and 19. In the single agent studies, MGI-114, CPT-11, and 5FU all resulted in decreased final tumor weights compared with vehicle-treated controls (P<0.05), but only MGI-114 at 7 mg/kg produced partial responses. When MGI-114 at 3.5 mg/kg was combined with CPT-11, significant decrements in final tumor weights occurred compared with monotherapy with the same doses of MGI-114 and CPT-11 (P< or =0.001). Also, administration of the low-dose combination (MGI-114 at 35 mg/kg and CPT-11 at 50 mg/kg) resulted in final tumor weights similar to those achieved after administration of high-dose MGI-114 as a single agent. Moreover, the combination of MGI-114 and CPT-11 produced partial responses in nearly all of the animals, with some animals achieving complete responses. The outcome with the combination of MGI-114 and 5FU was less striking, with fewer partial responses and no complete responses. These results suggest enhanced activity when MGI-114 is combined with CPT-11, and clinical trials to further evaluate this combination regimen are planned. (+info)
Cyclosporine inhibited calcium-mediated apoptosis of HL-60 cells.
AIM: To study the effects of cyclosporine (Cyc) on apoptosis of HL-60 cells. METHODS: Apoptotic cells induced by harringtonine (Har), camptothecin (Cam), or calcimycin (Cal), thapsigargin (Tha) were identified with DNA electrophoresis, morphology, and flow cytometry. Relative [Ca2+]i alteration of apoptotic HL-60 cells were determined with flow cytometry. RESULTS: Cal 1 mg.L-1 or Tha 0.5 mg.L-1 induced apoptosis of HL-60 cells. This effect was inhibited by nontoxic concentration of Cyc 1 mg.L-1. Cyc did not inhibit Har- or Cam-induced apoptosis of HL-60 cells. Both Cal and Tha increased intracellular calcium, whereas Har or Cam did not. CONCLUSION: Cyc inhibited apoptosis only induced by calcium increasement in HL-60 cells. The mechanism of apoptosis induced by Cal or Tha was different from that by Har or Cam. (+info)
Quercetin induced apoptosis in human leukemia HL-60 cells.
AIM: To examine whether quercetin (Que) might induce apoptosis in human leukemia HL-60 cells. METHODS: DNA fragmentation was visualized by agarose gel electrophoresis. Inhibition of proliferation was measured with a colorimetric MTT-assay. The DNA degradation was determined using flow cytometry, and the microscopic changes were observed by an electron microscope. RESULTS: Que 15-120 mumol.L-1 elicited typical apoptosis morphological changes including condensed chromatin, nuclear fragmentation, and reduction in volume. DNA fragmentation and DNA degradation in a concentration-dependent manner in HL-60 cells. Que inhibited HL-60 cell proliferation. The values of IC50 and 95% confidence limits were 43 (30-61) mumol.L-1 after 48-h treatment with Que. CONCLUSION: Que induced apoptosis in HL-60 cells. (+info)