Aquilur Rahman

Modulation of doxorubicin resistance in multidrug-resistant cells by liposomes.

In this study, we have confirmed the ability of liposome‐encapsulated doxorubicin to modulate drug resistance, as previously observed in CH LZ cells (Thierry et al., Cancer Commun. 1, 311‐316, 1989), in two human multidrug‐resistant (MDR) cell lines, the breast cancer MCF‐7/ADR cell line, and the ovarian carcinoma SKVLB cell line. This effect was specific to MDR cells, as liposomally encapsulated doxorubicin did not enhance cell sensitivity to the drug in the parental cell lines. Cytotoxicity assays demonstrated that empty liposomes in the presence of free doxorubicin (Dox) reversed resistance to the drug at a level that may be higher than that observed when liposome‐encapsulated Dox is used. This effect seems to be due to the high affinity of Dox for cardiolipin, one of the liposome components, which leads to the association of the drug and the cardiolipincontaining liposomes in the culture medium before entry into the cells. Neither pretreatment of empty liposomes before drug treatment nor combined incubation of vincristine and empty liposomes alter MDR in CH LZ cells, suggesting that the drug must be encapsulated or complexed to the liposomes to overcome MDR. Because MDR in CH LZ cells does not seem to be related to GSH level, MDR modulation by liposome‐encapsulated Dox apparently may not be effected by altering the GSH function. These results suggest that the enhancement of sensitivity of MDR cells using Dox encapsulated in liposomes or complexed with liposomes may be explained by an increase in cell drug incorporation and by an intracellular drug redistribution. Fluorescence confocal microscopy study indicated that Dox is transported and distributed mainly in intracytoplasmic vesicles in SKVLB and MCF‐7/ADR cells, whereas in parental cells the drug is located mainly in the nucleus. In addition, presentation of Dox in liposomes modifies the drug distribution pattern in MDR cells by partially shifting the drug to nuclear compartments. Thus, liposome‐associated Dox may bypass the vesicular drug transport in MDR cells, resulting in the enhancement of the drug biological activity.—Thierry, A. R., Vigé, D., Coughlin, S. S., Belli, J. A., Dritschilo, A., Rahman, A. Modulation of doxorubicin resistance in multidrug‐resistant cells by liposomes. FASEB J. 7: 572‐579; 1993.

An improved method of encapsulation of doxorubicin in liposomes: pharmacological, toxicological and therapeutic evaluation.

We describe here an improved method of encapsulating doxorubicin in liposomes using phosphatidylcholine, cholesterol and synthetic tetramyristoyl cardiolipin. With this new composition of lipids the entrapment of doxorubicin was found to be > 90%. Cytotoxicity studies using vincristine-resistant HL-60/VCR leukaemia cells showed that liposome-encapsulated doxorubicin reverses multidrug resistance 5-fold compared with conventional doxorubicin and at levels equivalent to that obtained using liposomes with natural cardiolipin. In normal mice, liposome-encapsulated doxorubicin was much less toxic than the conventional drug. A dose of 25 mg kg-1 i.v. of conventional doxorubicin produced 100% mortality in mice by day 14, whereas liposomal doxorubicin exhibited only 10% mortality by day 60. Liposomal doxorubicin demonstrated enhanced anti-tumour activity against murine ascitic L1210 leukaemia compared with conventional doxorubicin. At a dose of 15 mg kg-1, liposomal doxorubicin increased the median life span with 12 of 18 long-term (60 days) survivors compared with only 3 of 18 with conventional drug. Mice injected i.v. with liposomal doxorubicin had plasma levels 44-fold higher than conventional doxorubicin, producing significantly higher (P < 0.02) area under the plasma concentration curve. An altered tissue distribution was also observed with liposomal doxorubicin; cardiac tissue demonstrating at least 2-fold lower levels with liposomal doxorubicin probably accounting for its lower toxicity. This altered pharmacokinetics of liposome-encapsulated doxorubicin, providing enhanced therapeutic advantage and the ability to modulate multidrug resistance, could be useful in a clinical setting.

Sensitization of multidrug-resistant colon cancer cells to doxorubicin encapsulated in liposomes

SummaryThe effectiveness of liposome-encapsulated doxorubicin in overcoming multidrug resistance was studied in various human colon cancer cells. Colon-cancer cell lines SW403, HT29, SW620, and SW620/R overexpressed P-glycoprotein as determined by immunoflow cytometry, thereby confirming the presence of the multidrug-resistant phenotype. Important differences were observed in the cytotoxicity of free doxorubicin as represented by IC50 values of 0.168, 0.058, 0.023, and 9.83 μm for SW403, HT29, SW620, and SW620/R, respectively. Liposomally encapsulated doxorubicin provided an IC50 that was 1.4 times lower than that of the free drug in the doxorubicin-resistant SW 620/R cell line, whereas no difference was evident in the sensitive parental SW620 cells. In addition, liposomeencapsulated doxorubicin exhibited 1.31- and 2.33-fold cytotoxicity to HT-29 and SW403 cells, respectively. The ittracellular drug accumulation in SW620/R cells was enhanced by liposomally encapsulated doxorubicin, whereas it was reduced in all other cell lines as compared with that of free drug. The colon-cancer cell lines demonstrated different degrees of doxorubicin-induced DNA strand breakage that correlated with their sensitivities to drug-induced cytotoxicity. However, no difference was observed between DNA breakage caused by the free drug and that induced by liposome-encapsulated doxorubicin in any of the cell lines. The results suggest that the enhanced cytotoxicity of liposomal doxorubicin to colon cancer cells was due to some secondary non-DNA target. However, liposomally encapsulated doxorubicin appears to be effective in diminishing the multidrug-resistant phenotype and may have clinical applications.

Antitumor and toxicity evaluation of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes

SummaryThe antitumor activity of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes was evaluated in P388 ascitic leukemia, disseminated Gross leukemia, and advanced mammary carcinoma. In P388 leukemia, free drug and drug entrapped in liposomes demonstrated equivalent antitumor activity at doses of 2.2 and 4.4 mg/kg, demonstrating 52% and 69% ILS (increase in life-span), respectively. Free doxorubicin at a dose of 10 mg/kg was superior, producing a 185% ILS against 82% with liposomal doxorubicin. With an increase in administered dose the antitumor response with liposomal doxorubicin was much more pronounced; at doses of 20 and 25 mg/kg the ILS was in excess of 376%, with five of ten mice surviving tumor-free. In Gross leukemia, the optimum dose of free doxorubicin, 10 mg/kg, brought about 186% T/C (median survival in treated mice over that in controls, x100), whereas with liposomal doxorubicin the optimum dose was 16.9 mg/kg, which yielded 214% T/C. In advanced mammary carcinoma, the maximum tumor regression with free doxorubicin was at a dose of 7.5 mg/kg, with two of six mice dying of toxicity. Liposomal doxorubicin caused maximum tumor regression at 10.8 mg/kg dose with no toxic deaths. Doxorubicin entrapped in cardiolipin liposomes was much less toxic than free drug at high doses in normal mice.

Combination with liposome-entrapped, ends-modified raf antisense oligonucleotide (LErafAON) improves the anti-tumor efficacies of cisplatin, epirubicin, mitoxantrone, docetaxel and gemcitabine.

Raf-1 protein serine/threonine kinase plays an important role in cell proliferation and cell survival. We have previously described a novel cationic liposome-entrapped formulation of raf antisense oligodeoxyribonucleotide (LErafAON) and its use as a radiosensitizer. The aim of this study was to examine the effect of combination of LErafAON and a chemotherapeutic agent on growth of human prostate (PC-3) and pancreatic tumor xenografts in athymic mice (Aspc-1 and Colo 357). In PC-3 tumor-bearing mice, administration of a combination of LErafAON (i.v., 25 mg/kg/dose, ×10/16) and cisplatin (i.v., 11.0 mg/kg/dose, ×3), epirubicin (EPI) (i.v., 9.0 mg/kg/dose, ×3) or mitoxantrone (MTO) (i.v., 2.5 mg/kg/dose, ×3) led to enhanced tumor growth inhibition as compared with single agents (LErafAON+cisplatin versus cisplatin, p<0.0002, n=8; LErafAON+EPI versus EPI, p<0.0001, n=6; LErafAON+MTO versus MTO, p<0.05, n=5). In prostate or pancreatic tumor-bearing mice, combination of LErafAON (i.v., 25 mg/kg/dose, ×10/13) with docetaxel (Taxotere) (i.v., 5, 7.5 or 10 mg/kg/dose, ×2/4) led to tumor regression or enhanced growth inhibition as compared with single agents (PC-3: LErafAON+Taxotere versus Taxotere, p<0.02, n=7; Aspc-1: LErafAON+Taxotere versus Taxotere, p<0.03, n=5; Colo 357: LErafAON+Taxotere versus Taxotere, p<0.04, n=7). Combination of LErafAON (i.v., 25 mg/kg/dose, ×10/13) with gemcitabine (i.v., 75 mg/kg/dose, ×4/6) also caused a significant tumor growth inhibition in the two pancreatic carcinoma models studied (Aspc-1: LErafAON+gemcitabine versus gemcitabine, p<0.0001, n=7; Colo 357: LErafAON+gemcitabine versus gemcitabine, p<0.002, n =5). LErafAON treatment (i.v., 25 mg/kg/dose, ×10) caused inhibition of Raf-1 protein expression in these tumor tissues (around 25–60%, n=4–7). Interestingly, Taxotere treatment per se also led to decreased steady state level of Raf-1 protein in PC-3 and Aspc-1 tumor tissues (i.v., 10 mg/kg/dose, ×1 or 7.5 mg/kg/dose, ×2; around 25–80%, n=2/6). Present studies demonstrate enhanced tumor growth inhibition or regression in response to a combination of a chemotherapeutic drug and LErafAON. These data provide a proof-of-principle for the clinical use of LErafAON in combination with chemotherapy for cancer treatment.

BRCC2, a novel BH3-like domain-containing protein, induces apoptosis in a caspase-dependent manner.

We report here the structure-functional characterization of a novel intronless gene, BRCC2, located on human chromosome 11q24.1. BRCC2 open reading frame (327 bp) codes for an ∼12-kDa protein (108 amino acids (aa)) localized predominantly in the cytosol and to a lesser extent in the mitochondria. Ectopic expression of BRCC2 cDNA also was found in both the cytosol and mitochondria. Exogenous expression of BRCC2 caused apoptotic cell death in three different cell lines as evidenced by enhanced chromatin condensation, DNA fragmentation, or an enhanced number of cells in the sub-G1 phase. In human prostate cancer cells (PC-3), BRCC2-induced DNA fragmentation was blocked efficiently by coexpression of the anti-apoptotic molecule, Bcl-XL. Transient transfection of BRCC2 cDNA into PC-3 cells in the presence of a broad-range caspase inhibitor, Z-VAD-fmk (100 μM, 24 h), abrogated DNA fragmentation. Consistently, BRCC2 expression correlated with the activation of caspase-3 and caspase-9. An N-terminal deletion mutant of BRCC2 (10.2 kDa, Δ1-16 aa) lacking a BH3-like domain (5-12 aa, LPIEGQEI) or BRCC2 containing a mutant BH3-like domain (leucine 5→glutamate) failed to induce apoptosis, whereas a C-terminal deletion mutant (6.8 kDa, Δ62-108 aa) retained the apoptotic activity comparable to the full-length BRCC2. Finally, the treatment of HeLa cells with doxorubicin or hydrogen peroxide (H2O2) led to an increase in the mitochondrial (heavy membrane) level of endogenous BRCC2 (doxorubicin (100 ng/ml), 5 h, ∼2-fold; H2O2 (200 μM), 2 h, ∼2-fold). These findings demonstrate that BRCC2 functions as a proapoptotic molecule and suggest that BRCC2 induces a caspase-dependent mitochondrial pathway of cell death.

Modulation of multidrug resistance in Chinese hamster cells by liposome-encapsulated doxorubicin.

A Chinese hamster cell line (LZ), selected for multidrug resistance (MDR), exhibits a 3,000-fold resistance to doxorubicin, compared to parental V-79 cells. These drug resistant cells have amplified MDR genes, overexpress P-glycoprotein, and in the presence of doxorubicin show reduced intracellular drug accumulation. Using liposome-encapsulated doxorubicin (Rahman et al. Cancer Res. 45:796-803; 1985), we observed partial reversal of the resistance of LZ cells to this drug and a higher intracellular drug accumulation, compared to free drug. Parental V-79 cells, however, did not exhibit differences in survival or in drug accumulation when treated with encapsulated or free doxorubicin. Comparison of the effect of liposome-encapsulated doxorubicin with that of verapamil in reversing drug resistance showed that the liposomal preparation was as effective as verapamil used at its maximum clinically relevant concentration (1.5 microM). These results suggest that the use of liposomes as carriers of anticancer drugs may offer a strategy for overcoming MDR in tumor cells.

Will Hemoperfusion Be Useful for Cancer Chemotherapeutic Drug Removal

One of the major problems in clinical cancer chemotherapy is the inability to safely administer full therapeutic doses of specific drugs in the face of dysfunction of an organ system controlling that drugs metabolism and excretion. Should efficient drug removal from blood be possible following full therapeutic doses and after tumor exposure, then theoretically, even in the presence of organ dysfunction, anticancer drug toxicity may be reduced or avoided. Preliminary experiments in our laboratory have shown that adriamycin may be efficiently removed by activated charcoal from aqueous and protein solutions and blood in vivo, and that daunorubicin is removed in vitro to the same extent. However, although methotrexate is removed efficiently in vitro and extracted 50% in vivo by charcoal hemoperfusion, its overall pharmacokinetics do not appear to be altered in comparison with the alteration in pharmacokinetics of adriamycin achieved with charcoal hemoperfusion. Computer modeling has suggested that efficient adriamycin removal is achievable, and that clinical studies are warranted. For methotrexate removal, however, previous clinical studies and our own data suggest that charcoal hemoperfusion has little utility unless a highly specific sorbent for methotrexate removal can be developed.

Comparative immunotoxicity of free doxorubicin and doxorubicin encapsulated in cardiolipin liposomes

SummaryThe immunologic and pharmacologic effects of free doxorubicin and of doxorubicin entrapped in liposomes were compared in mice at a dose of 20 mg/kg. Liposomes for encapsulation of doxorubicin were prepared by using 39.35 μmol drug, 19.65 μmol cardiolipin, 100 μmol phosphatidylcholine, 68.4 μmol cholesterol, and 38.9 μmol stearylamine. Pharmacologic disposition studies after a dose of 20 mg/kg demonstrated 7- to 10-fold higher drug concentrations in the spleen at all time points following administration of doxorubicin entrapped in cardiolipin lipsosomes than after the free drug. The levels in liver were 4- to 5-fold higher with liposomal drug, whereas the cardiac uptake with liposomal doxorubicin was significantly lower than with free drug. Mice were sacrificed on days 1, 8, 15, and 22 after drug administration and spleen cells were isolated for studies of sensitization to alloantigens for cell-mediated cytolysis and of proliferation in response to mitogens. Mice treated with free doxorubicin demonstrated a decrease of more than 50 fold (compared with saline control) in allospecific cytotoxic activity on day 15; normal levels were recovered by day 22. The animals treated with doxorubicin encapsulated in liposomes showed a similar but not more pronounced fall to low levels. The total lytic activity per spleen after free drug or drug encapsulated in liposomes was markedly reduced at day 8, but this activity was fully recovered by day 15 in animals receiving liposomal doxorubicin; in those receiving free drug it had not recovered fully even at day 22. The proliferative response to concanavalin A was affected by the two forms of doxorubicin in a pattern very similar to the cytotoxic response. The proliferative response to lipopolysaccharide was markedly depressed by doxorubicin delivered in either form, and the kinetics were not altered by the mode of administration. The concentration of doxorubicin in spleen was markedly increased with liposomal delivery, but did not result in greater toxicity than that of free durg according to the immunologic parameters evaluated.

Phase I study and clinical pharmacology of 6-diazo-5-oxo-L-norleucine (DON)

The toxicity of the glutamine antagonist 6-diazo-5-oxo-L-norleucine (DON) administered as a 24 hour infusion has been evaluated. Studies of the clinical pharmacology of the drug have also been performed in 3 patients. The limiting toxicity of the drug was acute nausea, vomiting and diarrhea that was dose dependent in its severity and duration. The maximum tolerated dose was 600 mg/m2 over 24 hours. The other major toxicity was thrombocytopenia that was maximal 7–10 days after the completion of the infusion. The drug does not exhibit renal, hepatic or central nervous system toxicity. DON achieves steady state levels during these infusions and is eliminated by first order kinetics when the infusion is completed (t1/2α = 1.81 h). The principal route of excretion is renal. A starting dose of 400 mg/m2 would be acceptable for Phase II studies of this drug administered on this schedule.