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D Grabowski

Publications and source records attributed to D Grabowski.

33 records · Page 2Linked to original sources
PubMed1989

Progressive resistance to doxorubicin in mouse leukemia L1210 cells with multidrug resistance phenotype: reductions in drug-induced topoisomerase II-mediated DNA cleavage.

Cells selected for resistance to doxorubicin (DOX) express the multidrug resistance (MDR) phenotype, and resistance has been suggested to be due primarily to enhanced cellular efflux of drug. A progressively DOX-resistant (10- and 40-fold) L1210 mouse leukemia model system, which does not exhibit enhanced DOX efflux as a primary mechanism of resistance, was found to display the MDR phenotype, based on overexpression of P-glycoprotein in western blots and cross-resistance to vinca alkaloids. Cross-resistance to another topoisomerase II inhibitor, etoposide (VP-16), was similar to that of DOX (10- and 40-fold), whereas resistance to N-[4-(9-acridinylamino)-3-methoxyphenyl]methanesulfonamide (m-AMSA) was 5-fold lower. In contrast, no cross-resistance to camptothecin, an inhibitor of topoisomerase I, was observed. Topoisomerase II decatenation activity in nuclear extracts from 10- and 40-fold DOX-resistant cells was 2- and 4-fold lower, respectively, when compared to sensitive cells. In these cells, however, marked reductions in m-AMSA- and VP-16-induced topoisomerase II mediated DNA cleavage were found to exceed decreases in the catalytic activity of the enzyme. Results from this study demonstrated that, in progressively DOX-resistant L1210 mouse leukemia cells with the MDR phenotype, a better relation existed between the degree of resistance and reduced VP-16- and m-AMSA-induced topoisomerase II mediated DNA cleavage, than between increases in P-glycoprotein and concomitant reduction in DOX accumulation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1988

Differential effect of the calmodulin inhibitor trifluoperazine in modulating cellular accumulation, retention and cytotoxicity of doxorubicin in progressively doxorubicin-resistant L1210 mouse leukemia cells. Lack of correlation between cellular doxorubicin levels and expression of resistance.

Calmodulin inhibitors are effective in enhancing cytotoxic effects of doxorubicin (DOX) in DOX-resistant cells, possibly by enhancing cellular levels of drug. In the present study, L1210 mouse leukemia cells adapted to grow in vitro, in the presence of 0.025 to 0.25 microgram/ml DOX, and identified as L1210/DOX0.025, L1210/DOX0.05, L1210/DOX0.1, and L1210/DOX0.25 were approximately 5-, 10-, 20-, and 40-fold DOX resistant, respectively, compared to parent-sensitive cells (L1210/S). Using a soft agar colony assay and 3-hr drug exposure, the IC50 concentration of DOX in the progressively DOX-resistant (5- to 40-fold) L1210 cells ranged from 0.25 to 2.0 micrograms/ml and from 0.08 to 0.25 microgram/ml in the absence and presence of a non-cytotoxic concentration of 5 microM trifluoperazine (TFP) respectively. Further, based on the observed in vitro cytotoxic response, the IC50 concentration of DOX in the presence of 5 microM TFP was 2.5-, 4-, 6.7- and 8-fold lower than DOX without 5 microM TFP in the L1210/DOX0.025, L1210/DOX0.05, L1210/DOX0.1, and L1210/DOX0.25 resistant sublines respectively. In contrast, the IC50 of DOX in L1210/S cells was approximately 0.05 microgram/ml with or without 5 microM TFP. Cellular accumulation of DOX was 15-50% lower in the progressively resistant L1210 sublines compared to similarly treated L1210/S cells. However, in the presence of 5 microM TFP, cellular accumulation of DOX in the L1210/DOX0.05 and L1210/DOX0.1 but not L1210/DOX0.25 was comparable to the L1210/S cells. Cellular retention of DOX in the absence or presence of 5 microM TFP was comparable in similarly treated L1210/S, L1210/DOX0.05 and L1210/DOX0.1 cells, and a 2-fold reduction in the retention of DOX in the absence versus the presence of 5 microM TFP was apparent only in L1210/DOX0.25 cells. At the IC50 of DOX in the presence of 5 microM TFP, although cellular accumulation of DOX was concentration dependent over the range of 1-20 microM TFP, enhancement in cytotoxicity of DOX was dose dependent at 1-5 microM TFP but not 5-20 microM TFP. In cells treated for 3 hr at the IC50 concentration of DOX alone or DOX plus 5 microM TFP, cellular accumulation of DOX was 7- to 14-fold and 2.5- to 3.5-fold higher, respectively, in resistant than in sensitive cells. Additionally, following treatment for 3 hr at the IC50 dose of DOX in the absence or presence of 5 microM TFP, drug retention at 3 hr was 4- to 6-fold and 1.5-fold higher, respectively, in the resistant versus sensitive cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Modulation in vitro and in vivo of cytotoxicity but not cellular levels of doxorubicin by the calmodulin inhibitor trifluoperazine is dependent on the level of resistance.

The role of the calmodulin inhibitor trifluoperazine (TFP) in modulating the cellular levels and cytotoxicity in vitro and antitumour effects in vivo of doxorubicin (DOX), was evaluated in progressively DOX-resistant (5- to 40-fold) sublines of B16-BL6 mouse melanoma. In parental-sensitive B16-BL6 cells treated for 3 h, the IC50 of DOX was 0.1 microgram ml-1, and a less than 2-fold enhancement in DOX cell kill in the presence of a noncytotoxic concentration of 5 microM TFP was observed. However, in the DOX-resistant sublines, the IC50 was 0.7 to 5.0 micrograms ml-1 DOX in the absence of 5 microM TFP and 0.3 to 0.7 microgram ml-1 DOX in the presence of 5 microM TFP. The 2- to 7.5-fold decrease in the IC50 of DOX in the presence of 5 microM TFP, was dependent on the level of DOX-resistance in the various sublines. Compared to parental-sensitive cells, a 2-fold decrease in DOX-accumulation was evident only in the 40-fold DOX-resistant subline. Further, maximal enhancement (50%) of cellular DOX accumulation in the presence of 5 microM TFP was observed only in the 40-fold resistant cells treated with 5.0 micrograms ml-1 DOX. Retention of DOX in the 40-fold resistant subline was only 20% lower than similarly treated sensitive cells, and the inclusion of TFP increased DOX retention less than 10-15%. Antitumour studies in mice with experimental pulmonary metastases revealed that although DOX and DOX plus TFP had similar antitumour activity with the parental sensitive B16-BL6 cells, the combination of DOX plus TFP was significantly more effective than DOX alone with the DOX-resistant sublines. No overt toxicity was observed in normal mice treated with doses of TFP, DOX or DOX plus TFP used for in vivo chemotherapy studies. Results from this study suggest that gross cellular DOX levels do not appear to correlate with the magnitude of resistance, and the effects of TFP in modulating DOX resistance is possibly due to mechanisms other than mere alterations in cellular drug accumulation and/or retention.

Animals↗
PubMed1987

Characterization in vitro and in vivo of progressively adriamycin-resistant B16-BL6 mouse melanoma cells.

Adriamycin (ADR)-resistant sublines of B16-BL6 mouse melanoma selected by exposure to increasing concentrations of ADR were characterized in vitro for growth properties and in vivo for tumorigenicity and pulmonary metastases. The progressively resistant sublines adapted to grow in the presence of 0.025, 0.05, 0.1, and 0.25 microgram/ml ADR in monolayer culture were found to be 5-, 10-, 20-, and 40-fold ADR-resistant, respectively, compared to the parental sensitive cells, using a soft-agar colony assay and continuous ADR treatment for 7 days. The doubling time in monolayer culture of the parent sensitive and progressively ADR-resistant sublines of B16-BL6 melanoma cells was approximately 16-18 h. Although the colony-forming efficiency in soft agar of parental sensitive cells was only 0.5-4%, the 5-, 10-, 20-, and 40-fold ADR-resistant sublines had colony-forming efficiencies of 15, 20, 30, and 77%, respectively. Tumorigenicity in C57BL/6 mice of progressively ADR-resistant sublines was similar to parental sensitive cells following s.c. and i.p. implantation of 10(5)-10(6) tumor cells. Experimental pulmonary metastases were significantly lower in ADR-resistant sublines with progressive resistance. Additionally, unlike the parental sensitive and 5-fold ADR-resistant B16-BL6 cells, the 10-, 20-, and 40-fold ADR-resistant sublines were spontaneously nonmetastatic. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunochemical detection of P-glycoprotein revealed the presence of a Mr 170,000 plasma membrane glycoprotein in the 40-fold ADR-resistant subline and its counterpart maintained for 1 year in ADR-free medium. Results from this study suggest that progressively ADR-resistant B16-BL6 mouse melanoma cells selected in vitro demonstrate a marked increase in colony formation in soft agar and a decrease in the ability to produce pulmonary metastases, without alterations in tumorigenicity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1986

Factors governing the modulation of vinca-alkaloid resistance in doxorubicin-resistant cells by the calmodulin inhibitor trifluoperazine.

Calmodulin inhibitors enhance the cytotoxic effects of doxorubicin (DOX) in DOX-resistant (P388/DOX) P388 mouse leukemia cells by augmenting cellular accumulation and retention of drug. In P388/DOX cells which are cross-resistant to vinblastine (VLB) and vincristine (VCR), cell kill following treatment with VLB and VCR alone was evident only after 12 hr of treatment. Additionally, the 2- to 10-fold increase in cytotoxicity of the vinca alkaloids in the presence of 2 and 4 microM trifluoperazine (TFP) was observed only in P388/DOX cells treated for 12 hr, but not for 3 or 6 hr. However, in DOX-sensitive (P388/S) P388 mouse leukemia cells, cytotoxic effects of VCR but not VLB were apparent after treatment for 3 hr, and cell kill with VLB and VCR was enhanced 2- to 20-fold in the presence of 2 and 4 microM TFP following treatment for 12 hr. Cellular accumulation of [3H]VLB in P388/DOX cells was 12-fold lower than in similarly treated P388/S cells and, in the presence of 2 and 4 microM TFP, cellular VLB levels were enhanced 1.3- to 2.0-fold in P388/S cells and 2- to 8-fold in P388/DOX cells. The effect of TFP in increasing cellular retention of [3H]VLB was more apparent with P388/DOX cells, and retention of [3H]VLB in the presence of 4 microM TFP was enhanced less than 1.5-fold and greater than 4-fold in P388/S and P388/DOX cells respectively. Results from this study and our earlier observations with DOX and TFP in P388/DOX cells demonstrate that: (1) TFP potentiates the cytotoxicity of VLB and VCR in P388/S and P388/DOX cells by augmenting drug accumulation and retention; (2) enhanced cell kill in the presence of TFP with P388/DOX cells is apparent at 1 hr for DOX vs 12 hr for VLB and VCR; and (3) in P388/S cells, TFP has a more striking effect on the cellular accumulation, retention and cytotoxicity of VLB and VCR rather than DOX.

Animals↗
PubMed1986

Modulation of adriamycin and N-trifluoroacetyladriamycin-14-valerate induced effects on cell cycle traverse and cytotoxicity in P388 mouse leukemia cells by caffeine and the calmodulin inhibitor trifluoperazine.

1,3,7-Trimethylxanthine "caffeine" (CAF) is reported to induce a differential effect on the cytotoxicity of the DNA intercalators actinomycin-D versus Adriamycin (ADR). In the present study the effect of caffeine and/or trifluoperazine in modulating cell cycle traverse, drug accumulation, and cytotoxicity of anthracyclines was evaluated. The survival in soft agar of P388 mouse leukemia cells treated with ADR (0.05-0.25 micrograms/ml) alone for 1 h was 1.2- to 3-fold lower when the cells were incubated for 24 h in drug-free medium versus medium supplemented with 2 mM CAF. In contrast, for P388 cells treated with ADR in the presence of 2 mM CAF for 1 h and subsequently incubated for 24 h in the absence or presence of 2 mM CAF, cell killed based on colony formation in soft agar was 2- to 20-fold lower than in ADR-treated cells never exposed to 2 mM CAF. In cells treated continuously for 24 h with ADR (0.01-0.05 micrograms/ml) or the DNA nonbinding ADR analogue N-trifluoro-acetyladriamycin-14-valerate (AD32) (0.05 and 0.1 micrograms/ml) the survival in soft agar was 3- to 20-fold higher in the presence versus the absence of 2 mM CAF. The decreased cytotoxicity in cells treated with ADR or AD32 in the presence of CAF was accompanied by a significant reduction in the accumulation of cells in G2. However, in cells treated with ADR or AD32 in the presence of 2 mM CAF plus 5 microM trifluoperazine the decreased G2 accumulation was not accompanied by a reduction in anthracycline cytotoxicity. The modulation by CAF of ADR and AD32 cytotoxicity did not correlate with decreased cellular ADR and AD32 accumulation. Results from this study indicate that CAF markedly reduces the cytotoxicity of ADR or AD32 and trifluoperazine circumvents the effects of CAF.

Animals↗
PubMed1985

Calmodulin inhibitor trifluoperazine selectively enhances cytotoxic effects of strong vs weak DNA binding antitumor drugs in doxorubicin-resistant P388 mouse leukemia cells.

Doxorubicin-resistant P388 mouse leukemia cells are cross-resistant to anthracycline and non-anthracycline DNA intercalators as well as to natural and semisynthetic anthracyclines which bind weakly or not at all to DNA. In the presence of a non-lethal concentration of 5 microM trifluoperazine cytotoxic effects of the strong DNA binding drugs actinomycin-D, mitoxantrone and m-AMSA were enhanced less than 2 fold in doxorubicin-sensitive cells and up to 50 fold in doxorubicin-resistant cells. Additionally, trifluoperazine induced a greater than 2-fold enhancement in the cytotoxic effects (but not accumulation and retention) of the strong DNA binder N,N-dimethyladriamycin-14-valerate only in doxorubicin resistant cells. In contrast, cell kill, drug accumulation and retention in P388/S and P388/DOX cells treated with the weak DNA binders N-benzyl-adriamycin-14-valerate and 7(R)-O-methylnogarol, and DNA-nonbinding N,N-dibenzyldaunorubicin was similar with or without trifluoperazine treatment. The study demonstrates that the calmodulin inhibitor trifluoperazine induces a specific and marked enhancement in the cytotoxic effects of strong vs weak DNA binding antitumor drugs in doxorubicin-resistant cells.

Aminoacridines↗
PubMed1985

Analysis of heterogeneity in daunorubicin uptake by human leukemia cells using laser flow cytometry.

Heterogeneity in daunorubicin uptake by leukemic blast cells obtained from the bone marrow of 16 patients with acute leukemia (10 acute nonlymphocytic leukemia and 6 acute lymphocytic leukemia) was determined by laser flow cytometry following drug treatment in vitro for 1 hr. Fluorescence profiles of cellular anthracycline levels in the various samples indicated a marked heterogeneity in daunorubicin uptake and the range of detectable drug fluorescent cells was 34%-99%. A retrospective analysis of disease outcome in these patients who were treated with a daunorubicin or doxorubicin containing induction regimen indicated the following: (a) 8 of 11 patients who entered complete remission had greater than 80% of leukemic blast cells accumulating detectable amounts of daunorubicin; and (b) 3 of 4 patients who did not respond to chemotherapy had less than 40% of the leukemic blast cells accumulating detectable amounts of daunorubicin. These results suggest that laser flow cytometry may be useful in determining qualitative and quantitative differences in daunorubicin levels in heterogeneous tumor cell populations.

Adolescent↗
PubMed1984

Correlation between potency of calmodulin inhibitors and effects on cellular levels and cytotoxic activity of doxorubicin (adriamycin) in resistant P388 mouse leukemia cells.

The relationship between potency of phenothiazine and naphthalene-sulfonamide calmodulin inhibitors and their effects on cellular levels and cytotoxic activity of doxorubicin was evaluated using the doxorubicin-sensitive and greater than 100-fold doxorubicin-resistant P388 mouse leukemia model system. In cytotoxicity studies using cell counts based on proliferation following a 24-hr drug exposure and in survival based on colony formation in soft-agar after a 2-hr drug exposure, the calmodulin inhibitors significantly enhanced the cytotoxic effects of doxorubicin in the resistant but not parent-sensitive P388 cells. However, survival in soft-agar (based on colony formation) following long-term drug exposure (approximately 120 hr) revealed that the cytotoxic effects of doxorubicin were significantly increased by the calmodulin inhibitors in both sensitive and resistant P388 cells. Laser flow cytometry studies on single-cell doxorubicin levels indicated that treatment with doxorubicin in the presence of trifluoperazine had no effect on drug levels in sensitive cells but significantly enhanced cellular accumulation and retention of doxorubicin in resistant cells. Furthermore, unlike treatment with doxorubicin alone, in the presence of trifluoperazine, heterogeneity in cellular drug levels in the resistant P388 cells was not observed. Among the various calmodulin inhibitors effective in enhancing cellular levels and cytotoxic effects of doxorubicin in the resistant P388 cells, chlorpromazine was approximately two-fold less potent than trifluoperazine or prochlorperazine and only N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide but not N-(4-aminobutyl)-2-naphthalenesulfonamide was active.

Agar↗
PubMed1984

Differential effect of the calmodulin inhibitor trifluoperazine on cellular accumulation, retention, and cytotoxicity of anthracyclines in doxorubicin (adriamycin)-resistant P388 mouse leukemia cells.

Calmodulin inhibitors enhance cytotoxic effects of doxorubicin (DOX) in DOX-resistant (P388/DOX) P388 mouse leukemia cells by increasing cellular accumulation and retention of drug. In P388/DOX cells treated for 3 hr, cytotoxic effects (based on colony formation in soft agar) of daunorubicin (DAU) in the presence of trifluoperazine (TFP) were DAU concentration-dependent and enhanced 2- to 100-fold. Additionally, in the presence of TFP, on a molar basis, equitoxic doses of DAU were 4-fold lower than DOX for P388/DOX cells. However, in P388/DOX cells treated for 3 hr with other anthracyclines, except for a slight enhancement in the cytotoxic effects of aclacinomycin A (ACM) with TFP, colony formation in soft agar of cells treated with N-trifluoroacetyladriamycin-14-valerate (AD32) and N-trifluoroacetyladriamycin were similar in the absence and presence of TFP. In DOX-sensitive (P388/S) P388 mouse leukemia cells treated for 3 hr, some enhancement in the cytotoxic effects due to TFP were observed with DAU and DOX but not with ACM, AD32, or N-trifluoroacetyladriamycin. Although accumulation of ACM and AD32 in P388/S and P388/DOX cells was similar and unaffected by TFP, the retention of ACM but not AD32 was enhanced 1.5-fold only in TFP-treated P388/DOX cells. In contrast, DAU accumulation in P388/S cells was 4-fold higher than in similarly treated P388/DOX cells, and the 2- and 4-fold increase due to TFP in the accumulation and retention, respectively, of DAU in P388/DOX cells was not observed in P388/S cells. Results from this study indicate that in P388/DOX cells, the calmodulin inhibitor TFP is more effective with DAU than DOX, significantly less effective with ACM, and ineffective with AD32 and N-trifluoroacetyladriamycin.

Animals↗
PubMed1983

Enhancement of sensitivity to adriamycin in resistant P388 leukemia by the calmodulin inhibitor trifluoperazine.

Resistance to the cytotoxic effects of daunomycin and Adriamycin (ADR) in sublines of Ehrlich ascites and P388 mouse tumors has been demonstrated to be due to reduced cellular accumulation and retention of drug. In this study, the effect of the calmodulin inhibitor trifluoperazine on the cellular accumulation, retention, and cytotoxic effects of ADR in ADR-sensitive (P388/S) and ADR-resistant (P388/R) P388 mouse leukemia cells was determined. In cells treated in suspension culture for 24 hr or for 1 hr followed by plating in soft agar, a noncytotoxic concentration of 4 microM trifluoperazine, enhanced the sensitivity to ADR 2- to 6-fold in P388/R but not in P388/S cells. A marked enhancement in cellular retention rather than accumulation of ADR in only P388/R cells was obtained with trifluoperazine treatment. This study suggests the possible novel use of phenothiazines to improve drug sensitivity of tumors resistant to ADR treatment.

Animals↗