Cancer Letters

Published by Elsevier BV

Print ISSN: 0304-3835


Therapeutic effect of 1 M tegafur-0.4 M 5-chloro-2, 4-dihydroxypridine-1 M potassium oxonate (S-1) on head and neck squamous carcinoma cells
  • Article

November 2000


25 Reads


Shunsuke Yanoma


Hiromi Mizuno




Mamoru Tsukuda
1 M Tegafur (FT)-0.4 M 5-chloro-2,4-dihydroxypridine (CHDP)-1 M potassium oxonate (Oxo) (S-1), was developed as a new oral antineoplastic agent based on biochemical modulation of fluorouracil (5-FU) by CHDP and Oxo. The antitumor effect of S-1 on human head and neck squamous carcinoma cells was evaluated in xenografts and a metastasis model, in comparison with combined drug of 1 M FT and 4 M uracil (UFT). Mice treatment with S-1 showed a significant higher concentration of 5-FU in the tumor and the serum than UFT treated mice. S-1 showed higher tumor growth inhibition and metastasis inhibition than UFT. The mice in which metastasis was inhibited lived more than twice as long as the control mice. These results suggest that S-1 will have a higher clinical therapeutic effect against advanced squamous cell carcinoma of the head and neck in humans.

Isolation of a 18 000-Da molecular weight form of parathyroid hormone-related protein from the rat Walker carcinosarcoma 256

November 1992


20 Reads

The hypercalcaemic Walker carcinosarcoma 256 is a rat model for humoral hypercalcaemia of malignancy (HHM). Tumour products such as parathyroid hormone-related proteins (PTHRP) and various growth factors appear to be responsible for this syndrome. Recently, PTHRP immunoreactivity has been detected in the conditioned medium of Walker tumour cells. The present report describes the isolation of a 18,000-Da molecular weight form of PTHRP from Walker tumour homogenates, by using a relatively simple immunoaffinity purification method. Our results suggest that this PTHRP form is similar to that purified from other HHM-related tumours.

0004 DNA hypermethylation in breast cancer and its association with clinicopathological features

July 2006


43 Reads

Aberrant hypermethylation of gene promoter regions is one of the mechanisms for inactivation of tumour suppressor genes in breast cancer. We investigated whether hypermethylation identifies breast cancers with distinctive clinical and pathological features. We evaluated the methylation of RARbeta2, CDH1, ER, BRCA1, CCND2, p16 and TWIST in 193 breast carcinomas. Methylation frequencies ranged from 11% for CCND2 to 84% for ER. Tumours with frequent methylation (4-6 genes) were more often poorly differentiated compared to those with infrequent methylation (0-2 genes; P=0.004). Tumours with ER and CDH1 methylation were associated with significantly lower hormone receptor levels, younger age at diagnosis and the presence of mutant p53. Our data suggests that gene methylation may be linked to various pathological features of breast cancer, however, this requires confirmation in larger studies.

Fig. 1. RT-PCR analysis of mdr1 gene expression. 1, PCR marker; 2, KB cells; 3, KB cells; 4, KBr cells. The DNA fragments of the PCR marker are 1543, 994, 695, 515, 377 and 237 base pairs. The KB cell line was used as a positive control for mdr1 gene expression.
Erratum to “Bcl-2 plays a key role instead of mdr1 in the resistance to hexadecylphosphocholine in human epidermoid tumor cell line KB” [Cancer Lett. 142 (1999) 183–188]☆☆PII of original article: S0304-3835(99)00146-9
  • Article
  • Full-text available

September 1999


28 Reads

We induced tolerance to hexadecylphosphocholine (HePC) in the human epidermoid tumor cell line, KB. After 70 weeks of adaptation, the IC50 of HePC in the resistant cells KBr was 32-fold higher than in parental KB cells, and they were 30-fold more resistant to another ether lipid analogue, ET-18-OCH3. The KBr cells also showed cross-resistance to vincristine and colchicine while remaining sensitive to other chemotherapy agents. RT-PCR assays showed that expression of the multidrug resistance gene (MDR1) was positive in KBr cells, whereas the expression of GST-pi (glutathione S-transferase pi) and MRP (multidrug resistance protein) was undetectable in KBr cells. Both an immunocytochemistry test and Western blot analysis indicated that the expression of bcl-2 in KBr cells was strongly positive, while it was only mildly expressed in KB cells. Verapamil could not reverse the resistance of KBr to HePC although it is a well-known reversing agent against MDR1. Our results suggest that bcl-2 instead of MDR1 plays a major role in the resistance of KBr cells.

AG490 Influences UCN-01-Induced Cytotoxicity in Glioma Cells in a p53-Dependent Fashion, Correlating with Effects on BAX Cleavage and BAD Phosphorylation

December 2007


19 Reads

We determined the cytotoxicity of AG490 as a single agent and in combination with 7-hydroxystaurosporine (UCN-01) in a panel of malignant human glioma cell lines. Because p53 has important roles in cell cycle checkpoints, it has been anticipated that modulation of checkpoint pathways should sensitize p53 defective cells while sparing the normal cells. Cell proliferation was determined from dose-response curves. AG490 was effective as a cytotoxic agent alone regardless of p53 status. Combining the Chk1 inhibitor UCN-01 dramatically enhanced the response to AG490 in p53-mutated or deleted glioma cells. An opposite effect was noted in p53-wild type cells, in which UCN-01 and AG490 had antagonistic effects on cell proliferation and viability. We found that AG490 enhanced BAD phosphorylation in p53 wild type glioma cells, which appeared to protect against UCN-01-induced cytotoxicity, whereas AG490 enhanced UCN-01-induced cytotoxicity in p53 defective cell lines by suppression of BAD phosphorylation and induction of BAX and PARP cleavage. These observations highlight the potential for genotype-dependent factors to strongly influence response to signaling-targeted therapies in malignant gliomas and the importance of considering such factors in correlative response analyses for these agents.

Ovarian tumor growth regression using a combination of vascular targeting agents anginex or topomimetic 0118 and the chemotherapeutic irofulven

August 2008


83 Reads

Combination of chemotherapeutic agents and angiogenesis inhibitors is now commonly employed in the clinic to treat cancer. Here, we used angiostatic agents anginex and 0118, in combination with the chemotherapeutic irofulven, to treat human ovarian tumor xenografts in mice. General linear mixed models were used to statistically analyze tumor growth curves. Overall, combination of a low, non-toxic dose of irofulven with either angiogenesis inhibitor was more effective at inhibiting tumor growth than any of the single agent therapies. For example, the anginex/irofulven and 0118/irofulven combinations inhibited tumor growth relative to controls by 92% (p<0.0001) and 96% (p<0.0001), respectively, with the 0118/irofulven combinations yielding 100% complete responses. This study suggests that combination therapy of 0118 or anginex and irofulven may be highly effective in the clinical setting.

Induction of cytotoxic T cell response against HCA661 positive cancer cells through activation with novel HLA-A*0201 restricted epitopes

November 2007


28 Reads

HCA661 is a cancer-testis (CT) antigen frequently expressed in human hepatocellular carcinoma (HCC). To search for immunogenic peptides of HCA661, bioinformatics analysis and CD8(+) T cell IFN-gamma ELISPOT assay were employed, and two HLA-A *0201 restricted peptides, H110 and H246, were identified. These two HCA661 peptides are naturally processed in dendritic cells (DCs) and when used for DCs loading, they are sufficient to prime autologous CD8(+) T cells to elicit cytotoxic response against HCA661(+) human cancer cells. The HCA661 peptides, H110 and H246, are hence attractive candidates for human cancer immunotherapy.

Identification of an HLA-A*0201 restricted Bcl2-derived epitope expressed on tumors

July 2007


22 Reads

A large number of human tumor-associated antigen-derived peptides have been identified that are recognized by CTLs in a MHC-I restricted fashion. The apoptosis inhibitory protein Bcl2 is overexpressed in many human cancers as part of their neoplastic phenotype. Since inhibition or loss of Bcl2 expression might impair tumor growth and survival, this protein may serve as a rational target for vaccine-induced CTL responses. By Western blot technique, we screened a panel of established human tumor cell lines for proteins involved in the apoptotic process. Two of eight tumor cell lines, a B lymphoma (Loukes) and a colon carcinoma (CCL220) cell line showed increased Bcl2 protein expression whereas the majority of tumor cell lines expressed proapoptotic proteins. Neither fibroblasts nor peripheral blood mononuclear cells showed Bcl2 expression. An HLA-A*0201 restricted CTL epitope was deduced in silica from the amino acid sequence of the Bcl2 protein and its binding affinity for HLA-A*0201 was confirmed using a biochemical binding assay. We here demonstrate that the 9-mer peptide Bcl2(85-93) induces specific CTL reactivity in immunized C57-A2K(b) or -A2D(b) tg mice. These Bcl2(85-93) specific CTLs react with and lyse Bcl2-expressing human colon carcinoma CCL220 cells which have been transfected with a chimeric HLA-A*0201/H2-K(b) DNA construct similar to that expressed in the transgenic mice. Based on these observations, we suggest that Bcl2(85-93) may be a target for immune therapy.

Novel Hsp90 inhibitor FW-04-806 displays potent antitumor effects in HER2-positive breast cancer cells as a single agent or in combination with lapatinib

November 2014


59 Reads

Human epidermal growth factor receptor 2 (HER2), a member of the HER family of tyrosine kinases and a binding partner of Heat shock protein 90 (Hsp90), is found amplifies in approximately 25% breast cancers. Treatment of HER2+ breast cancers has been greatly improved in recent years, but the accompanying upregulation of HER3 induced by HER2 blockade has subdued the therapeutic effect. FW-04-806, a novel Hsp90 N-terminal inhibitor that disassociates the Hsp90/Cdc37/client complex and degrades Hsp90 clients, was studied alone or in combination with the EGFR/HER2 tyrosine kinase inhibitor lapatinib in HER2+ breast cancer cells. We found that FW-04-806 alone or with laptinib inhibits cell proliferation, induces cell apoptosis and reduces the total and activated HER3 levels in these cells, while lapatinib has been reported to increase HER3 expression followed HER2 inhibition. The combination of FW-04-806 and lapatinib showed synergistic reduction of HER2 expression and the downstream PI3K/Akt and Ras/MEK/ERK pathways, enhanced suppression of Akt-mediated FOXO3a inactivation and augmented antitumor efficacy on SKBR3 xenografts with a favorable toxicity profile, suggesting its viability as a combination therapy for clinical studies in HER2+ breast cancer patients. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Rhodamine 123 efflux modulation in the presence of low or high serum from CD56+ hematopoietic cells or CD34+ leukemic blasts by B9309-068, a newly designed pyridine derivative

August 1998


8 Reads

The newly designed pyridine derivative B9309-068 and a series of structurally different compounds were tested for their ability to modulate rhodamine 123 (RHO) efflux from CD56+ hematopoietic cells in the presence of either 10% fetal calf serum or undiluted human AB serum. Furthermore, efflux modulation was investigated on CD34+ blast populations obtained from four patients with relapsed state AML. Target cells were specified throughout by labeling with peridinine chlorophyll protein (PerCP)-conjugated monoclonal antibodies, allowing clear differentiation from RHO emission spectrum by flow cytometry. In the presence of low serum each compound efficiently modulated RHO efflux without significant differences in the range of final concentrations (1.0-3.0 microM). At 0.1 microM, however, RHO efflux was differentially modulated following the series GF120918 approximately B9309-068 > PSC 833 > DNIG approximately DVER. With CD56+ cells in the presence of undiluted human AB serum at a final modulator concentration of 0.1 microM, all chemosensitizers tested were found to be inefficient. At final concentrations of 0.3 microM or higher, distinct RHO efflux modulation was found with the following efficacies: B9309-068 approximately GF120918 > PSC 833 > DVER approximately DNIG. The efficacies seen in undiluted human AB serum at 3.0 microM were comparable to those seen on CD56+ cells at final modulator concentrations of 0.1 microM in low serum. Our results identify the pyridine derivative B9309-068 as a promising compound for modulating P-glycoprotein-mediated drug resistance under conditions resembling the clinical setting. Nonetheless, modulation potencies of a series of structurally very different chemosensitizers was revealed to be substantially diminished at high serum concentrations in vitro.

Combination Of Azd2281 (Olaparib) And Gx15-070 (Obatoclax) Results In Synergistic Antitumor Activities In Preclinical Models Of Pancreatic Cancer.

February 2014


71 Reads

In this study, we explored the antitumor activities of the PARP inhibitor AZD2281 (Olaparib) and the pan-Bcl-2 inhibitor GX15-070 (Obatoclax) in six pancreatic cancer cell lines. While both agents were able to cause growth arrest and limited apoptosis, the combination of the two was able to synergistically cause growth arrest and non-apoptotic cell death. Furthermore, in an in vivo xenograft model, the combination caused substantially increased tumor necrosis compared to either treatment alone. Our results support further investigation of the combination of Bcl-2 and PARP inhibitors for the treatment of pancreatic cancer.

The BH3-mimetic GX15-070 induces autophagy, potentiates the cytotoxicity of carboplatin and 5-fluorouracil in esophageal carcinoma cells

February 2010


39 Reads

Despite improvements in both surgical techniques and radio- and chemo-therapy regimens, the prognosis of esophageal cancer is poor. In pursuit of novel effective strategy, this study examined the effect of the BH3-mimetic GX15-070 on esophageal carcinoma cells. We discovered that GX15-070 inhibited the growth of esophageal cancer cells. There was synergism between GX15-070 and carboplatin or 5-fluorouracil. GX15-070 induced autophagy in esophagus cancer cell line EC9706 and osteosarcoma cancer cell line U2OS. 3-methyladenine and chloroquine, inhibitors of autophagy with distinct mechanisms, potentiated the cytotoxicity of GX15-070. In conclusion, GX15-070 inhibits growth of esophageal cancer cells.

BO-0742, a derivative of AHMA and N-mustard, has selective toxicity to drug sensitive and drug resistant leukemia cells and solid tumors

April 2009


30 Reads

This is a preclinical study of BO-0742, a derivative of 3-(9-acridinylamino)-5-hydroxymethyl-aniline (AHMA) and N-mustard, as an anti-cancer agent. MTS assays revealed a broad spectrum of anti-cancer activities in vitro, with the greatest cytotoxicity against leukemia and neuroblastoma including those with drug resistant characteristics, and a good therapeutic index with leukemia being 10-40 times more sensitive to BO-0742 than hematopoietic progenitors. Administration of BO-0742 at an optimal dose schedule based on its pharmacokinetics significantly suppressed the growth of xenografts of human breast and ovarian cancers in mice. Thus, BO-0742 is a potent anti-cancer agent worthy of further clinical development.

Mortalin sensitizes human cancer cells to MKT-077-induced senescence

August 2007


105 Reads

Mortalin is a chaperone protein that functions in many cellular processes such as mitochondrial biogenesis, intracellular trafficking, cell proliferation and signaling. Its upregulation in many human cancers makes it a candidate target for therapeutic intervention by small molecule drugs. In continuation to our earlier studies showing mortalin as a cellular target of MKT-077, a mitochondrion-seeking delocalized cationic dye that causes selective death of cancer cells, in this work, we report that MKT-077 binds to the nucleotide-binding domain of mortalin, causes tertiary structural changes in the protein, inactivates its chaperone function, and induces senescence in human tumor cell lines. Interestingly, in tumor cells with elevated level of mortalin expression, fairly low drug doses were sufficient to induce senescence. Guided by molecular screening for mortalin in tumor cells, our results led to the idea that working at low doses of the drug could be an alternative senescence-inducing cancer therapeutic strategy that could, in theory, avoid renal toxicities responsible for the abortion of MKT-077 clinical trials. Our work may likely translate to a re-appraisal of the therapeutic benefits of low doses of several classes of anti-tumor drugs, even of those that had been discontinued due to adverse effects.

GDC-0941 sensitizes breast cancer to ABT-737 in vitro and in vivo through promoting the degradation of Mcl-1

June 2011


25 Reads

The present study showed that GDC-0941 potently sensitized breast cancer to ABT-737 in vitro and in vivo. ABT-737 exhibited limited lethality in breast cancer cells; however, when combined with GDC-0941, it displayed strong synergistic cytotoxicity and enhanced caspase-mediated apoptosis. GDC-0941 promoted proteasomal degradation of Mcl-1, of which the overexpression has been validated to confer ABT-737 resistance, thereby enhanced the anticancer efficacy of ABT-737. Furthermore, the combination of GDC-0941 and ABT-737 exerted increased anti-tumor efficacy on MDA-MB-231 xenograft models. Overall, our data described unprecedentedly the promising therapeutic potential and underlying mechanisms of combining GDC-0941 with ABT-737 in treating breast cancer.

Biliary excretion of platinum in rats after administration of cisplatin and aqua(1,1-bis(aminomethyl)-cyclohexane)sulfatoplatinum(II) (Spiroplatin, TNO-6)

September 1985


37 Reads

Three groups of 6 rats were treated with cisplatin (3 mg/kg, bolus and 3-h infusion) and spiroplatin (3 mg/kg, bolus) by infusion in the right external jugular vein. The mean amounts of platinum +/- c.v. excreted in the bile during the first 6 h after the start of administration were 0.32 +/- 0.19% and 0.39 +/- 0.29% of the dose after bolus injection and 3-h infusion of cisplatin, respectively, and 3.77 +/- 3.32% of the dose after spiroplatin. The values were not significantly different between the 2 cisplatin administration modes (P greater than 0.05), but were between the spiroplatin and cisplatin bolus groups (Wilcoxon two-sided rank test, P less than 0.01). These data are related to pharmacokinetic parameters in man.

Inhibition of breast cancer cell growth and induction of cell death by 1,1-bis(3′-indolyl)methane (DIM) and 5,5′-dibromoDIM

June 2006


128 Reads

1,1-Bis(3'-indolyl)methane (DIM) and the 5,5'-dibromo ring substituted DIM (5,5'-diBrDIM) inhibited growth of MCF-7 and MDA-MB-231 breast cancer cells, and IC50 values were 10-20 and 1-5 microM, respectively, in both cell lines. DIM and 5,5'-diBrDIM did not induce p21 or p27 protein levels or alter expression of Sp1 or Sp3 proteins in either cell line. In contrast, 10 microM 5,5'-diBrDIM downregulated cyclin D1 protein in MCF-7 and MDA-MB-231 cells 12 and 24 h after treatment. DIM (20 microM) also decreased cyclin D1 in MCF-7 (24 h) and MDA-MB-231 (12 h), and the DIM/5,5'-diBrDIM-induced degradation of cyclin D1 was blocked by the proteasome inhibitor MG132. Both DIM and 5,5'-diBrDIM induced apoptosis in MCF-7 cells and this was accompanied by decreased Bcl-2, release of mitochondrial cytochrome c, and decreased mitochondrial membrane potential as determined by the red/green fluorescence of JC-1. DIM and 5,5'-diBrDIM induced extensive necrosis in MDA-MB-231 cells; however, this was accompanied by decreased mitochondrial membrane potential primarily in cells treated with 5,5'-diBrDIM but not DIM. Thus, DIM and 5,5'-diBrDIM induce cell death in MCF-7 and MDA-MB-231 cells by overlapping and different pathways, and the ring-substituted DIM represents a novel class of uncharged mitochondrial poisons that inhibit breast cancer cell and tumor growth.

Effects of N-nitrosodiethanolamine and 1,1-diethanolhydrazine in Syrian golden hamsters

February 1978


10 Reads

N-Nitrosodiethanolamine (NDEA) and 1,1-diethanolhydrazine (DEH) were synthesized and injected subcutaneously weekly in male and female Syrian golden hamsters. The total NDEA dose per hamster was approx. 15 g/kg body wt. applied in either 7 or 27 subdoses. DEH was administered in 78 applications to two groups yielding total doses of 1.1 g and 273 mg/kg body wt. Under these conditions, DEH did not show a specific demonstrable carcinogenic effect. However, within 78 weeks after the first application, 39 out of 56 hamsters treated with NDEA developed tumors. Primarily, neoplasms of the nasal cavity and tracheal tumors were observed, as well as a few hepatocellular adenomas and sarcomas at the injection site. These findings and those of the earlier study on carcinogenicity of NDEA in rats raise concern as to the safety for human consumption or industrial use of products with the potential for forming NDEA.

Tumor-promoting activities of hydroquinone and 1,1-dimethylhydrazine after initiation of newborn mice with 1-methyl-1-nitrosourea

September 1999


19 Reads

To clarify the suitability of a newborn-mouse carcinogenesis assay to detect tumor-promoting activities of carcinogens, the non-genotoxic hydroquinone (HQ) and genotoxic 1,1-dimethylhydrazine (UDMH) were administered to mice during the promotion stage after treatment with 1-methyl-1-nitrosourea (MNU) (20 mg/kg body wt, single intraperitoneal injection) at day 9 after birth. Initiated males and females thus received either HQ at 0.8% in basal diet, or UDMH, at 20 mg/kg body wt once weekly by subcutaneous injection, from day 14 until the end of the experiment at 30 weeks of age. Uninitiated newborn mice, given an injection of the vehicle (0.01 M citrate buffer (pH 5.5), 20 mg/kg body wt), also received HQ or UDMH in the same way. Histopathologically, focal proliferative lesions were found in the livers of male mice and in the lungs of both male and female mice in the MNU-treated groups. HQ significantly increased the incidence and multiplicity of altered hepatocellular foci, the combined incidence of hepatocellular adenomas and carcinomas in males and the incidence and multiplicity of lung adenomas and the combined incidence of lung adenomas and carcinomas in female mice. In addition, four out of eleven MNU + HQ-treated male mice developed lung carcinomas, showing a significant elevation in multiplicity. UDMH also exhibited a tendency to increase the incidence and multiplicity of lung adenomas in female mice. Thus tumor-promoting effects of HQ or UDMH were apparently exerted in the target organs and the MNU-initiated two-stage newborn-mouse carcinogenesis assay may be useful for detection of genotoxic or non-genotoxic carcinogenicity.

Influence of hydrolysis products of aqua(1,1-bis(aminomethyl)cyclohexane)sulfatoplatinum(II) on toxicity in rats

December 1984


32 Reads

Aqueous solutions of the cisplatin analog aqua(1,1-bis(aminomethyl)-cyclohexane)sulfatoplatinum(II) (TNO-6, spiroplatin) principally contain hydrolyzed and oligomerized molecules. Sodium sulfate reduces the hydrolysis of the sulfato ligand. We investigated the influence of the equilibrium state on nephrotoxicity of spiroplatin in rats receiving 3 doses of 3 mg/kg with an interval of 8 days. Rats (n = 6) treated with spiroplatin solubilized in isoosmotic sodium sulfate (impaired hydrolysis) showed less toxicity as measured by proteinuria, platinum excretion and body weight, than the group treated with spiroplatin solubilized in 5% glucose. This result indicates that the presence of hydrolysis products plays a role in the toxicity of spiroplatin.

Induction of malignant peripheral nerve sheath tumors in European hamsters with 1,1-dimethylhydrazine (UDMH)

July 1987


49 Reads

A rate of up to 43% of malignant peripheral nerve sheath tumors (PNST) was induced in European hamsters (EH) after weekly s.c. administration of 1,1-dimethylhydrazine (UDMH). The overall neoplastic response in the treated EH was also elevated as compared to the untreated controls. Histologically, the malignant PNST were neurofibrosarcomas and melanotic as well as unpigmented schwannomas. The occurrence of melanotic schwannomas is briefly discussed with regard to the histogenesis of this rare tumor type.

The carcinogenic effect of 1,1-diethyl-3-methyl-3-nitrosourea in Syrian golden hamsters

July 1984


11 Reads

1,1-Diethyl-3-methyl-3-nitrosourea (Et2MNU) was subcutaneously injected in Syrian golden hamsters once weekly for 52 weeks. The animals developed mainly papillomas and squamous cell carcinomas of the nasal cavity and forestomach and hemangioendotheliomas of the spleen. Although survival time and tumour latency showed dose-dependency, tumour incidence did not.

Quantification of tumour cell—endothelial cell attachment by 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine (DiI)

February 1997


20 Reads

Tumour cell attachment to the endothelial cell lining of the circulatory system is of utmost importance in the process of cancer spread. We describe here a method of quantifying tumour cell attachment to an endothelial cell layer in vitro, using the fluorescent carbocyanine dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiI). We show that by incubation of human tumour cells with this fluorochrome, a high degree of fluorescent label can be incorporated into the cells without cytotoxic effects. These labelled tumour cells can then be used in subsequent attachment assays involving confluent human endothelial cell layers and subsequently quantified by using a fluorescent plate reader. Monitoring of this assay by fluorescent microscopy showed no transfer of the dye between tumour and attached endothelial cells. The labelled cells remained fluorescent for more than 3 days with no observable cytotoxicity. We suggest that DiI is of use in an assay system such as this to determine the effects of various factors on tumour cell-endothelial cell attachment.

A comparative study of dimethylhydrazine regioisomers and the methylazoxymethanol metabolite of 1,1- and 1,2-dimethylhydrazine in relation to transformation in human fibroblasts

January 1986


9 Reads

Comparative analysis of the cytotoxicity, transformation efficiency, induction of alkali labile sites (ALS) and DNA methylation in human foreskin fibroblasts was carried out with two dimethylhydrazine (DMH) regioisomers (1,1-DMH and 1,2-DMH) and the acetate (A) derivative of the metabolite methylazoxymethanol (MAM) of 1,2-DMH. Effective ED50 cytotoxic doses for MAMA, 1,1-DMH and 1,2-DMH were 0.056, 6.83 and 6.30 mM, respectively. MAMA and 1,1-DMH were more effective transformers than 1,2-DMH. However, methylation of purines accounted for less than 1% of the total radiolabel associated with DNA for all 3 agents. 1,2-DMH, 1,1-DMH and MAMA induced O6MeGua/N7MeGua ratio of 0.04, 0.32 and 0.18, respectively. Only MAMA induced measurable alkali labile lesions at transforming doses. These results suggest that other mechanisms may play a role in the initiation of transformation events by hydrazine analogues.

Inhibition of intercellular communication between liver cells by the liver tumor promoter 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane

March 1981


7 Reads

A dose dependent inhibition of intercellular communication (metabolic cooperation) between primary cultures of rat liver hepatocytes and an established adult rat liver epithelial cell 6-thioguanine resistant strain by the liver tumor promoter 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) is demonstrated. This in vitro assay is proposed to evaluate the tumor promoting activity of oncogenic agents shown to be non-genotoxic in the liver culture systems.

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