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Biomedical subjects

Y M Rustum

Publications and source records attributed to Y M Rustum.

At least 91 records · Page 5Linked to original sources
PubMed1994

Schedule-dependent efficacy of idarubicin (Ida) and doxorubicin (Dox).

Schedule dependency of idarubicin (Ida) and doxorubicin (Dox) toxicity was investigated in vitro using the K562 human leukemia cell line. For Dox, repeated exposure to the IC30 (d x 3) resulted in comparable survival as single exposure to the total accumulative dose (20%). For Ida, repeated exposure to the IC30 (d x 3) decreased survival to 5%, while single exposure to the total accumulative dose reduced survival only to 20%. Total cellular accumulation of Dox was independent of schedule of exposure, while for Ida, repeated exposure resulted in a significantly higher drug accumulation compared to the single exposure to the accumulative dose. The data indicate that the schedule-dependent differences in cytotoxicity for the two compounds can be accounted for almost exclusively by an increased cellular uptake and retention of Ida with repeated drug exposure.

Cell Division↗
PubMed1993

Antitumor activity of the weekly intravenous push schedule of 5-fluoro-2'-deoxyuridine +/- N-phosphonacetyl-L-aspartate in mice bearing advanced colon carcinoma 26.

We have investigated the effects of N-(phosphonacetyl)-L-aspartate (PALA) administered i.v. as a single dose (100 mg/kg) on the antitumor activity of 5-fluoro-2'-deoxyuridine (FdUrd) and 5-fluorouracil (FUra), on the pharmacokinetic parameters of FdUrd and FUra, and on the tumor pyrimidine ribonucleotide triphosphate pools in mice bearing advanced colon carcinoma 26 and leukemia 1210. The antitumor activity was evaluated with PALA administered i.v. 24 h prior to the maximum tolerated dose of FUra and FdUrd administered by: (a) 4 days of continuous infusion (schedule 1, c.i. days 1-4); (b) daily for 4 days by i.v. push (schedule 2, i.v. days 1-4); and (c) weekly for 3 weeks (schedule 3, i.v. weekly for 3 weeks). The maximum tolerated doses of FdUrd were 20, 150, and 400 mg/kg/day and for FUra were 25, 50, and 80 mg/kg/day for schedule 1, 2, and 3, respectively. At the maximum tolerated doses, the antitumor activity in mice bearing advanced colon carcinoma can be summarized as follows: (a) FdUrd is significantly more active than FUra; (b) for both drugs the weekly for 3 weeks i.v. push schedule is superior to the c.i. or i.v. push daily for 4 days schedules; (c) pretreatment with PALA enhances the antitumor activity of FdUrd and FUra and resulted in 95 and 13% complete responses, respectively; (d) long-term survivors with FUra could only be achieved in the presence of PALA; in mice bearing leukemia 1210 cells, FdUrd or FUra with or without PALA exhibited no significant antitumor activity when PALA was administered in a single dose 24 h prior to fluoropyrimidine treatment; and (e) in C-26 and L1210, PALA reduced the pools of CTP and UTP equally, to about 10% of controls with significant difference in their rates of recovery.

Animals↗
PubMed1993

Isolation and characterization of a human ileocecal carcinoma cell line (HCT-8) subclone resistant to fluorodeoxyuridine.

A 5-fluoro-2'-deoxyuridine (FdUrd)-resistant subclone (Fd9XR) of HCT-8 (human ileocecal carcinoma) cells was established by two schedules of drug exposure. Initially, cells were exposed to short-term (3 hr) 100 nM FdUrd repeatedly (9 cycles over 8 months), and cells were then exposed to 10 nM FdUrd continuously. During this latter stage, a colony (Fd9XR) with fast growth rate was isolated, expanded, and characterized with respect to mechanisms of resistance to FdUrd and cross-resistance to other chemotherapeutic agents. Fd9XR cells were 1000-fold resistant to FdURD, but 3-fold more sensitive to 5-fluorouracil (FUra) than HCT-8 cells. After a 3-hr treatment with FdUrd, Fd9XR cells accumulated 6630-, 69-, and 3.7-fold less fluorodeoxyuridylate (FdUMP), fluorouridine triphosphate (FUTP) and acid-insoluble materials, respectively, than HCT-8 cells. However, when FUra was substituted for FdUrd, Fd9XR cells accumulated 9.2-, 3.1-, and 2.3-fold more FdUMP, FUTP and acid-insoluble materials, respectively, than HCT-8 cells. Fd9XR and HCT-8 were similar in their growth rates, combined pools of 5,10-methylenetetrahydrofolates (5,10-CH2H4PteGlun) and tetrahydrofolates (H4PTeGlun), thymidine phosphorylase (TP) activity, and level and activity of thymidylate synthase (TS). In contrast, thymidine kinase (TK) activity of Fd9XR was 0.23 and 0.35% of that of HCT-8, for thymidine (dThd) and FdUrd as substrates, respectively. Furthermore, Fd9XR cells exhibited greater sensitivity to the antifolate TS inhibitor ICI D1694 and to methotrexate (MTX) than HCT-8 cells. In addition, dThd alone and in combination with hypoxanthine did not offer any protection against the cytotoxic effect of ICI D1694 in Fd9XR cells. These results indicate that in Fd9XR cells (1) TK deficiency is the primary mechanism of resistance to FdUrd; (2) the greater sensitivity to FUra was associated with higher pools of FdUMP and FUTP with a subsequently higher level of incorporation into cellular RNA; and (3) antifolate compounds, e.g. ICI D1694 and MTX, could be useful agents in the treatment of FdUrd-resistant tumors associated with decreased TK activity and decreased capacity of utilizing dThd.

Antimetabolites, Antineoplastic↗
PubMed1993

Growth slow-down and growth arrest of human colon carcinoma cells HCT-8 in vitro after exposure to 5-fluoro-2'-deoxyuridine.

Cellular heterogeneity in drug response denotes a mixed response among individual cells in a drug treated population. Individual cell responses may be more complex than 'cell kill' and 'no response'. In this study we employed a colony formation assay and high-resolution image analysis to detect the various responses such as immediate and delayed cessation of growth, growth delay and growth slow-down, at the level of the individual colony. The evaluation was carried out using a human ileocaecal adenocarcinoma cell line (HCT-8) and the anti-tumour agent 5-fluoro-2'-deoxyuridine (FdUrd). In the presence of a drug concentration which, in standard monolayer assays, inhibits the growth to about 50% (IC50) only about 20% of the colonies ceased to grow and the remaining colonies grew at a growth rate of about 70% of control. At an FdUrd concentration which, in standard monolayer assays, reduced growth by > 90% (> IC90), about 50% of the cells grew, with growth rates of about 30% of control. The slowing of growth, most prominent at lower drug concentrations, should be considered in determining mechanisms of drug action at the individual cell level. In clinical situations in which high drug doses are precluded by toxicity to normal tissues, growth slow-down may play a significant role in tumour response.

Cell Division↗
PubMed1993

Long-term outcome of patients with acute myelogenous leukemia: the role of maintenance therapy, consolidation therapy and the predictive value of two in vitro assays.

Three successive strategies used to treat acute myelogenous leukemia (AML) patients who entered complete remission are compared with respect to their long term efficacy (> 5 years). Additionally, the ability of two in vitro assays to identify patients who would be long term remitters was assessed. With respect to the proportion of patients in long term remission, 5 years of maintenance therapy, intensive consolidation therapy plus 3 years of additional therapy, and 4 courses of consolidation therapy produced equivalent results with 18 to 22% of patients in remission at 7 years. Patients whose leukemia cells retained high levels of cytosine arabinoside triphosphate (araCTP) and who received maintenance therapy were less likely to experience early relapse than comparably treated patients whose leukemia cells failed to retain araCTP. The failure of leukemia cells to clone in vitro was also associated with a lower early relapse rate for patients who received maintenance therapy. Neither the ability of leukemia cells to retain araCTP nor their ability to clone in vitro were of prognostic significance for patients treated with 4 courses of intensive consolidation therapy.

Arabinofuranosylcytosine Triphosphate↗
PubMed1993

In vivo reversal of doxorubicin resistance by a new tiapamil analog Ro11-2933.

The effectiveness of a calcium antagonist analog Ro11-2933 to modulate doxorubicin (DOX) response in DOX-sensitive (WT) and -resistant (DOXr, 200-fold) cell lines was investigated and compared to verapamil (VP) in vitro and in vivo in rats bearing mammary carcinoma using equivalent nontoxic doses. In vitro exposure to a nontoxic concentration of Ro11-2933 (2 microM) normalizes the DOX accumulation defect observed in DOXr cells, increases DOX-induced DNA single-strand breaks and effectively sensitizes DOXr cells to DOX. Ten microM VP was required to obtain an effect equivalent to that seen with 2 microM Ro11-2933. Intravenous administration of DOX at 5 mg/kg to the rat bearing the DOXr tumors has no significant therapeutic effect on tumor growth (P > .5), whereas it was found effective in inhibiting the growth of WT tumors (P < .05). Ro11-2933 or VP administered alone has no significant effect on tumor growth as compared to a saline-treated group (P > .1). Combination of Ro11-2933 with DOX effectively inhibits DOXr tumor growth as compared to DOX alone. Combination of DOX with VP was found less effective than Ro11-2933 and the results were not statistically significant from DOX treatment alone (P > .5). Our data demonstrate that Ro11-2933 is well tolerated after i.v. administration and an effective modulator of DOX resistance in a solid tumor model.

Animals↗
PubMed1993

Effect of doxorubicin, daunorubicin, and idarubicin on the growth rate of human leukemia cells (K562) studied with image analysis.

The effects of doxorubicin, daunorubicin, and idarubicin on the growth of K562 cells were investigated by monitoring the formation of individual colonies in semi-solid culture employing an automated image analysis system. Drug effects were evaluated using short-term exposure (2 h) at clinically achievable drug plasma concentrations. Following drug exposure, heterogeneity in growth patterns was observed which was categorized into three distinct types; (1) continuous growth at a decreased growth rate; (2) limited growth; (3) no growth. In addition to a concentration-dependent decrease of the growth fraction, a reduction of the growth rate of the continuously growing colonies was observed. At equitoxic drug concentrations, comparable changes in growth rate were observed for each of the three anthracyclines studied. It is demonstrated that the fraction of cells which escape drug-induced growth arrest with therapeutically achievable drug concentrations display a significant decrease in growth rate.

Cell Division↗
PubMed1993

Characterization of tumor cell heterogeneity of a murine leukemia cell line (L1210) in response to arabinosylcytosine: quantitation using a computerized image analysis system.

Cytosine arabinoside (Ara-C) is one of the most effective drugs in inducing remission in acute nonlymphocytic leukemia (ANLL) patients. However, the high recurrence rate indicates that a subpopulation of leukemic cells escapes drug effect. This cellular heterogeneity in drug response may play a major role in chemotherapeutic outcome. We have recently developed the individual colony-formation assay (ICFA) to study drug effects on the kinetics of proliferation of individual cells and their progeny. Thus parameters of proliferation are calculated for individual colonies. Three categories of drug responses were defined, including immediate growth cessation, delayed growth cessation (growth stops several days after drug exposure) and growth slowdown (logarithmic growth at a reduced rate compared to control). In the experiments included in this report, murine leukemia (L1210) cells were exposed to various concentrations of Ara-C for 1, 6 or 24 hours, and their responses quantified. Regardless of the Ara-C concentration or exposure time, subpopulations of cells were observed in each of the three response categories: immediate or delayed arrest or growth slowdown. As expected, the fraction of cells exhibiting immediate growth cessation generally increased with increasing drug dose and was markedly increased with longer exposure time. Delayed arrest was most prevalent at intermediate drug concentrations at all exposure times. If exposure was limited to 1 hour, at least 30% of cells continued to grow, although at a reduced rate (71% control rate after exposure to 1 mM Ara-C). This limited effect was paralleled by saturation of Ara-C triphosphate (Ara-CTP) formation. Six-hour exposure left at least 6.4% of cells growing, with an average rate of 45% of control. Under these conditions, no saturation in Ara-CTP formation was observed. Even 24-hour exposure to 5 microM Ara-C left 4.8% of colonies growing, at 42% of control rate. Thus a subpopulation of cells continued to grow even after 24-hour exposure to a relatively high concentration of Ara-C. Surviving, but slowly growing, cells may represent a previously unrecognized population that may contribute to therapeutic failure.

Animals↗
PubMed1992

Time dependence of DNA lesions and growth inhibition by ICI D1694, a new quinazoline antifolate thymidylate synthase inhibitor.

DNA single-strand breaks and associated growth inhibition induced by the thymidylate synthase inhibitor N-(5-[N-(3,4-dihydro-2-methyl-4-oxoquinazoline-6-ylmethyl)-N -methylamino]-2 - thenoyl)-L-glutamic acid (ICI D1694) were quantitated using the human ileocecal adenocarcinoma cell line, HCT-8. The effects of different concentrations and schedules of [6R,S]-5-formyltetrahydrofolate ([6RS]LV) and 2'-deoxy-thymidine (dThd) on drug growth inhibition and DNA damage were also evaluated. The drug concentrations for 50% inhibition of cell growth in culture following 2-h and 72-h exposures were 0.073 and 0.003 microM, respectively. After a 2-h drug exposure, the occurrence of DNA single-strand breaks (SSBs) was time dependent. It was detectable at 8 h and reached a maximum at about 24 h, 34 +/- 3 (SD) and 305 +/- 34 rad equivalents with 0.1 microM (50% inhibition concentration) and 1.0 microM (90% inhibition concentration) ICI D1694, respectively. A significant level of DNA SSBs (101 +/- 13 rad equivalents) was still detectable at 72 h after the 2-h treatment with 1 microM ICI D1694. No significant level of DNA SSBs was detected when cells were exposed simultaneously to ICI D1694 and 20 microM [6RS]LV. Complete rescue of drug-induced DNA SSBs could be achieved when cells were exposed to 10 microM dThd starting no later than 4 h after drug treatment. The growth inhibition of ICI D1694 was abrogated by [6RS]LV in a concentration-dependent manner. Complete protection was achieved when cells were exposed simultaneously to 1 microM ICI D1694 and 5 microMs [6RS]LV or to 3 microMs dThd immediately after drug treatment. The results demonstrate that: (a) the growth inhibition of ICI D1694 is a function of time and schedule; (b) the growth inhibition is accompanied by extensive DNA single-strand breaks and slow repair; (c) at 1 microM ICI D1694, 3 microMs dThd and 5 microMs [6RS]LV can completely rescue cells from drug effects when dThd is added up to 4 h following drug treatment or when [6RS]LV is given in combination with the drug; (d) interference of [6RS]LV with ICI D1694 action may be occurring at the level of drug uptake and at intracellular targets, while dThd interferes with the drug action at intracellular targets.

Cell Division↗
PubMed1992

Growth of human renal cortical tissue on collagen gel.

A model system for 3-dimensional "native-state" culture of tissues on collagen gels (Proc. Natl. Acad. Sci. USA 86:2013-2017; 1989) has been applied in this study to histologically normal human renal cortical tissue from 11 patients undergoing nephrectomy for renal cell carcinoma elsewhere in the kidney. Microbial contamination occurred in 12/90 cultures, the rest (78) were studied by visual inspection, histology, immunohistochemical analysis for pankeratin (epithelial cell origin), vimentin (mesenchymal cell origin), and p-glycoprotein (associated with proximal tubules), transmission electron microscopy (EM), incorporation of tritiated thymidine (3HTdR). In the first 10 days, explants showed 3HTdR-labeled cells in tubule structures. The surrounding gel was invaded by cells forming tubule structures, sometimes with basement membrane. Some of these cells showed labeling by 3HTdR and immunostaining positive for pankeratin and p-glycoprotein. EM showed well-polarized epithelial cells in tubule structures with tight junctions, interdigitating lateral processes, and microvilli characteristic of proximal and distal convoluted tubules. 3HTdR-labeled cells in tubule structures were observed even 2 mo. after Passage 1, 6 mo. after the initial explantation. Tubule growth was most active and fibroblast proliferation was negligible from 2 to 4 wk postexplantation. The proliferation of tubulelike cells and formation of tubulelike structures in this system represents an opportunity to study human renal cortical tissue in vitro, under conditions more closely resembling in vivo circumstances than are present in other in vitro systems suitable for long-term study. This model has potential use for in vitro toxicology studies and studies of renal physiology.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

1-Beta-arabinofuranosylcytosine in therapy of leukemia: preclinical and clinical overview.

Although the mechanisms of therapeutic efficacy of cytosine arabinoside (Ara-C) are multifactorial, the pharmacodynamic basis for its cytotoxicity and therapeutic efficacy lies in its intracellular metabolism and the retention of the active metabolite, Ara-C triphosphate (Ara-CTP), which is a competitive inhibitor of DNA polymerase. Additional determinants of tumor cell sensitivity include Ara-CMP incorporation into cellular DNA, the size of the competing normal metabolite, deoxycytidine/5'-triphosphate pool, and the heterogeneity in growth kinetics of tumor cells, S-phase vs cells in other phases of the cell cycle. With high-dose Ara-C, substantial amounts of Ara-CTP are formed in phases of the cell cycle. The presence of high intracellular concentration with prolonged retention of Ara-CTP could lead to the inhibition of cell growth of the cells entering S-phase as a consequence of inhibition of DNA-polymerase and/or incorporation into cellular DNA, resulting in a chain termination. Pharmacokinetically, Ara-C is rapidly eliminated from plasma. In mice, pharmacokinetic parameters of Ara-C are not sufficient predictors for the observed differences in their in vivo antitumor activity. Although these mice were bearing different tumor types (L1210 Ara-C sensitive or P-388 relatively more resistant), the observed differences in tumor response were achieved under identical plasma Ara-C concentrations and area under the concentration time curve. The observed antitumor activity in L1210 cells is primarily associated with higher Ara-CTP pools and retention (T1/2 > 4 hr) in tumor cells as compared with normal bone marrow cells. In the least responsive tumor (P-388), although Ara-CTP pools were sufficiently high, retention of the drug in tumor cells and in normal cells is poor with a T1/2 < 2 hr. Thus, unlike mice bearing leukemia L1210 cells, alteration of the mode and dose of administration of Ara-C in mice bearing P-388 could only result in increased host toxicity with no therapeutic gain. Similarly in patients with acute nonlymphocyte leukemia (ANLL), there is no significant correlation between plasma Ara-C concentration and the intracellular concentrations or retentions of Ara-CTP. In some patients the highest Ara-CTP pools in leukemic myeloblast cells are achieved at a lower level of plasma Ara-C and decrease further with the increase of plasma Ara-C. Thus, in the in vivo model system and in ANLL patients with no prior chemotherapy, Ara-CTP retention is a critical factor associated with response to this agent, in particular its direct association with duration of complete response.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Chemotherapeutic strategies in metastatic colorectal cancer: an overview of current clinical trials.

5-Fluorouracil (5-FU) is still the mainstay of chemotherapy in patients with metastatic colorectal cancer. A prolonged infusion of 5-FU is more active than any other schedule of 5-FU used to date. Cisplatin does not improve treatment results compared with 5-FU alone and is not recommended outside clinical trials. Biomodulation of 5-FU is a major step forward in the treatment of colorectal cancer patients and as the standard chemotherapy for advanced colorectal cancer. Two schedules of folinic acid daily for 5-day (low and high doses) and weekly high dose in combination with daily or weekly 5-FU are the most widely used schedules. Although the response rates to either schedule are comparable, the profile of toxicity is different, being stomatitis for the daily schedule and diarrhea for the weekly schedule as the dose-limiting toxicity. Modulation of 5-FU by methotrexate is time dependent. An interval of 24 hours between methotrexate and 5-FU is necessary for effective modulation. Other modulators, like interferon and N-phosphonoactyl-L-aspartate (PALA), are promising treatment options currently under investigation in randomized trials. The data from phase II and III trials using modulation of 5-FU by folinic acid, PALA, or methotrexate, or using continuous infusion 5-FU indicate that all of these strategies are active. Randomized trials are currently underway to further investigate these therapeutic approaches and whether a specific modulation offers more therapeutic advantages.

Antimetabolites, Antineoplastic↗
PubMed1992

Comparison of an immunoperoxidase "sandwich" staining method and western blot detection of P-glycoprotein in human cell lines and sarcomas.

The applicability of a multilayer immunoperoxidase "sandwich" method (IpS) developed by Chan14 for the amplified detection of P-glycoprotein (Pgp) was investigated. The authors examined 15 formalin-fixed cell lines, as well as formalin-fixed, paraffin-embedded sections from single biopsies of 46 sarcomas. The cell lines included sensitive and multidrug resistant sublines (KB, A2780, MCF-7, HeLa) with various relative degrees of resistance to doxorubicin (Dox). The sarcoma biopsy specimens were selected on the basis of the results obtained in Western blot (WB) detection of Pgp (22 positive and 24 negative by WB) using C219 and C494 monoclonal antibodies to Pgp. The IpS method employed C219. The least resistant cell line in which Pgp could be detected by IpS was fivefold resistant to doxorubicin, whereas Pgp was detected by WB in cells greater than twofold resistant. Cell lines having greater than fivefold resistance to Dox were positive by both IpS and WB analyses. The less resistant cell lines contained more nonreactive cells whereas the highly resistant cell lines showed more homogeneous strong membrane reactions. Among the six cell lines determined to be Pgp negative by WB analysis, no false positive immunostaining by IpS existed. One of 22 WB positive and 7 of 24 WB-negative sarcoma biopsy specimens were positive by IpS methods. Reaction varied and was always focal (a minimum of 3-5 cells, ranging up to 3-4 high power fields) indicating pronounced heterogeneous distribution of Pgp. Thus, WB can detect low average (overall) levels of Pgp in tumor samples but such low concentrations of PgP at the single cell are not detectable by IpS methods. However, IpS can discern among many Pgp-negative cells small subpopulations of immunoreactive cells, which are not detected by WB analysis due to Pgp dilution by the membrane protein of numerous Pgp negative cells. IpS and WB used together as complementary methods can provide more complete information about Pgp distribution and content, particularly in the case of heterogeneous human tumors. The IpS method is more suitable for less drastically treated (not embedded) cell line specimens than for paraffin-embedded (routine) sections. Some modification of the present IpS protocol seems necessary to increase its sensitivity and reduce the disparity with WB results.

ATP Binding Cassette Transporter, Subfamily B, Mem↗