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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many fragile sites in the human genome occur at or near chromosomal breakpoints reportedly involved in translocations of DNA material in neoplastic cells. This fact has led some investigators to postulate that fragile sites have a pathogenic role in human neoplasia. To learn whether caffeine-induced fragile sites relate to breakpoints found in the neoplastic cells of an individual patient, we studied lymphocytes from the peripheral blood of 32 patients in remission from malignant disease. Lymphocytes were cultured in medium containing either 5-Fluoro-2'-deoxyuridine (FdU) or FdU plus caffeine, and G-banded metaphases were examined for nonrandom breaks. Analyses of completely G-banded malignant cell chromosomes from 31 of the 32 patients were available for comparison. In only once case, a 5-year-old child with acute lymphoblastic leukemia, did a caffeine-induced fragile site (1q44) coincide with a breakpoint in the neoplastic cells [dup(1)(q21-->q44)]. Our findings suggest that chromosomal abnormalities in childhood malignancies cannot generally be explained by the presence of FdU- or FdU plus caffeine-induced fragile sites.
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PMID:Relationship between chemical-induced fragile sites and chromosomal breakpoints in malignant cells in children. 149 41

We have established in vivo cisplatin-resistant mouse leukemia cell lines, L-1210/DDP and P388/DDP, in order to elucidate the mechanism of acquired resistance to cisplatin. Resistance indices were 22 and 14, respectively, when the cells were exposed to cisplatin for 48 h. Uptake of cisplatin by both resistant lines was significantly reduced, compared with values for the respective parent lines (17% for L-1210/DDP and 27% for P388/DDP, at 100 microM for 1 h). While glutathione contents in the resistant cells were 1.7-1.9 times higher than those in the sensitive ones, their reduction by preincubation with buthionine sulfoximine did not influence the sensitivity of the cells to cisplatin. In addition, the resistant lines did not show lower sensitivity to CdCl2 than the respective sensitive ones, suggesting that intracellular SH groups might contribute little to the mechanism of cisplatin resistance in these cells. Postincubation with DNA repair inhibitors, caffeine and aphidicolon, did not selectively enhance the sensitivity of the resistant cells to cisplatin. These results suggested that reduced drug uptake would be a primary mechanism of cisplatin resistance in L-1210/DDP and P388/DDP. Cross-resistance patterns to platinum complexes were quite different between L-1210/DDP and P388/DDP. Colon 26/DDP, another cisplatin-resistant mouse tumor showed a different pattern from those observed with L-1210/DDP and P388/DDP. In the development of new platinum complexes we should use plural resistant lines for examining cross-resistance patterns to candidate platinum complexes.
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PMID:Characterization of acquired resistance to cis-diamminedichloroplatinum(II) in mouse leukemia cell lines. 155 3

The glycoprotein hormone common alpha-subunit can be induced in HeLa and other nontrophoblastic tumor cell lines by sodium butyrate. This report demonstrates that production of alpha-subunit can be further modulated by theophylline, especially in conjunction with butyrate. This synergism was not observed with other phosphodiesterase inhibitors such as xanthine, caffeine, theobromine, or methylisobutylxanthine. Induction by a combination of the short chain fatty acid plus the methylxanthine results from a decrease in the lag time after effector addition as well as a change in the rate of subunit accumulation. The increase in alpha-subunit is correlated with an increase in the levels of alpha-subunit mRNA, suggesting that induction is manifest at a pretranslational stage. The production of alpha-subunit was only marginally affected in cultures treated with 8-Br-cAMP or forskolin. Intracellular levels of cAMP were increased approximately threefold by methylisobutylxanthine, twofold by theophylline, fourfold by forskolin, and about 50% by butyrate, yet significant induction was achieved only by butyrate and theophylline. Taken together, these data suggest that the synergism between butyrate and theophylline is not mediated by cAMP.
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PMID:Enhancement by theophylline of the butyrate-mediated induction of choriogonadotropin alpha-subunit in HeLa cells. I. Lack of correlation with cAMP. 169 36

Pentoxifylline, a methylxanthine that is used to treat veno-occlusive disease, can increase perfusion in undervascularized tissues. Addition of high concentrations, like caffeine, causes progression through radiation or drug induced G2 phase blocks, thereby limiting time for repair of DNA breaks and crosslinks. We have examined the potential of pentoxifylline to augment the effects of antitumor alkylating agents in vitro and in vivo. In MCF-7 human breast cancer cells in vitro, pentoxifylline (2 mM) present for 24 h was only slightly cytotoxic (approximately 10% cell kill at 2 mM), but when present prior to and during AA it increased the cytotoxicity of CDDP by 2 logs at 250 microM. With L-PAM in vitro, pentoxifylline was much less effective and only at a concentration of 250 microM L-PAM did 2 mM pentoxifylline increase cytotoxicity (approximately 0.3 logs). In the FSaIIC murine fibrosarcoma system, 100 mg/kg of pentoxifylline i.p. immediately prior to the alkylating agent or 50 mg/kg x 5 of pentoxifylline over 24 h with the alkylating agent given immediately after the third dose increased the tumor cell kill achieved by CDDP, carboplatin, cyclophosphamide, and thiotepa. The increase in tumor cell killing was modest (2.9-fold). Pentoxifylline in the multiple dose regimen (50 mg/kg x 5 over 24 h) was more effective than in the single dose (100 mg/kg) protocol. In the EMT6 mouse mammary adenocarcinoma, pentoxifylline (100 mg/kg daily x 5) improved the tumor growth delay produced by CDDP (3.3 mg/kg alternate days x 3), carboplatin (25 mg/kg daily x 5), cyclophosphamide (100 mg/kg alternate days x 3) and thiotepa 5 mg/kg (daily x 5). Only with cyclophosphamide, however, did the interaction appear to be large, as a 2.4-fold increase was observed.
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PMID:Efficacy of pentoxifylline as a modulator of alkylating agent activity in vitro and in vivo. 174 13

Conventional chemotherapy for unresectable or metastatic adenocarcinoma of the pancreas has had little effect on palliation or survival. Almost all studies of systemic therapy have involved empiric use of a variety of Phase II or conventional agents alone or in combination. On the basis of recent studies using a human tumor pancreatic cancer (PC) xenograft in nude mice, a Phase I clinical trial of cisplatin, high-dose cytosine arabinoside (Ara-C), and caffeine (CAC) was performed in patients with advanced incurable PC. A tolerable dose and schedule of the three agents were developed. Seven of 18 patients with measurable disease in this Phase I trial had partial responses to CAC. A Phase III comparison of CAC versus standard treatment using streptozotocin, mitomycin, and 5-fluorouracil (SMF) was performed. Eighty-two patients with advanced PC were entered into this random assignment trial. The two treatment arms were well balanced for the usual prognostic factors. Although the acute (e.g., nausea and vomiting) toxicities of CAC were greater than those of SMF, both groups of patients tolerated treatment resonably well. Ninety percent of patients were evaluable for response. Two patients (5.5%) on the CAC treatment arm (95% confidence interval [CI], 0% to 15%) and four patients (10.2%) on the SMF treatment arm (95% CI, 1% to 22%) had objective responses (partial response in measurable disease or improvement in evaluable disease). No complete remissions were observed. The 95% confidence limits of response for CAC and SMF overlapped. The median duration of survival for all patients on the SMF treatment arm was 10 months, although it was 5 months on the CAC treatment arm (P = 0.008). In this Phase III comparison, CAC was not superior to conventional therapy with SMF in terms of response and was inferior for survival. Neither regimen is effective treatment for advanced PC.
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PMID:A phase III comparison trial of streptozotocin, mitomycin, and 5-fluorouracil with cisplatin, cytosine arabinoside, and caffeine in patients with advanced pancreatic carcinoma. 183 42

Aqueous, caffeine free and tannin fractions of commercial tea and tannic acid were tested for mutagenicity in Ames test. Tea fractions of tannic acid were non mutagenic in strains TA 100, TA 98, TA 1535 and TA 1538 of Salmonella typhimurium with or without metabolic activation (rat-S9 mix) at different doses tested. In strain TA 98 the above tea fractions and tannic acid inhibited the S9 mix mediated mutagenicity of tobacco in a dose dependent manner. The different tea fractions at 60 degrees C, did not increase the tumor incidence in Swiss mice by gavage feeding. They also failed to produce tumors when injected subcutaneously. Caffeine free tea extract decreased the tobacco induced liver tumors but had no effect on lung tumors. The same fraction was ineffective in hexachlorocyclohexane induced liver tumors in Swiss mice.
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PMID:Mutagenicity and carcinogenicity of tea, Camellia sinensis. 191 36

The treatment of ovarian carcinoma includes maximum surgical removal of the tumor tissue followed by irradiation or chemotherapy. In this study, the effects of caffeine on cell cycle traverse have been studied over a 168-hr period after X irradiation in BG-1 cells, an ovarian carcinoma cell line. The results were obtained with dual-parameter flow cytometric measurements of DNA and nuclear protein, using propidium iodide and fluorescein isothiocyanate. After radiation alone, a dose-related arrest of cells in G2 phase and cell kill were observed. Irradiating BG-1 cells with 5 Gy produced an accumulation of the cells in G2 at 24-72 hr postirradiation. When G2 was divided into low nuclear protein (G2A) and high nuclear protein (G2B) compartments, there was a G2A peak accumulation at 24 hr and a G2B peak accumulation at 48-72 hr. The addition of 1 mM caffeine to the culture media, starting immediately postirradiation, prevented G2 arrest, promoting a rapid traverse of cells through G2A to G2B to G1, which was associated with diminished survival.
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PMID:Cell kinetic perturbations after irradiation and caffeine in the BG-1 ovarian carcinoma cell line. 195 84

The effect of caffeine upon the radiosensitivities of three human tumor lines was examined and correlated with its action upon the radiation-induced S-phase and G2-phase blocks. Caffeine was found to reduce at least partially the S-phase and G2-phase blocks in all the cell lines examined but potentiated cytotoxicity in only one of the three tumor lines. That reductions have been demonstrated to occur in the absence of increased cell killing provides supporting evidence for the hypothesis that reductions may not be causal in those cases when potentiation of radiation-induced cytotoxicity is observed in the presence of caffeine.
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PMID:Reduction of radiation-induced cell cycle blocks by caffeine does not necessarily lead to increased cell killing. 200 Apr 49

Using flow cytometry we found that proliferation of Ehrlich ascites carcinoma (EAC) cells has been reversibly arrested in the second half of the G2 period at the plateau phase of tumor growth in vivo. The ratio of G2/G1 cells increased from 0.3 at 6 days post tumor inoculation to 2.5 at 16 days when up to 25-35% of EAC cells are in G2. It was shown that when ascites fluid removal was followed by transferral in culture, G2-blocked cells synchronously entered the G1 phase via mitosis. In the presence of ascites fluid in the culture medium, EAC cells progressed through G1 and S phases but accumulated in G2. Fetal bovine serum, beta-mercaptoethanol, and caffeine failed to release cells from the G2 block when added to ascites fluid in culture. It is concluded that neither nutrient depletion nor a lack of growth factors is responsible for the G2 arrest of EAC cells. We suggest that ascites fluid contains a factor(s) which potently interrupts the G2 phase of the cell cycle.
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PMID:Reversible G2 block in the cell cycle of Ehrlich ascites carcinoma cells. 205 71

While many advances have been made in the chemotherapy of gynecologic cancers, treatment failures remain a major clinical problem. A growing understanding of the mechanisms of tumor cell resistance to antineoplastic drugs provides a framework for the development of chemotherapy regimens containing agents capable of modulating tumor response. Using a short-term ATP bioluminescence assay we studied the ability of two methylxanthines (caffeine, pentoxifylline) and an inhibitor of ADP-ribosyl transferase (3-aminobenzamide) to enhance cisplatin cytotoxicity in gynecologic cancer cell lines. Our findings of significantly enhanced cisplatin-induced cytotoxicity with two different analysis techniques confirms the effectiveness of these agents. These results may have future clinical significance.
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PMID:Chemical enhancement of cisplatin cytotoxicity in a human ovarian and cervical cancer cell line. 212 26


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