Anthracycline Efficacy in vitro: Cytotoxicity of Liposomal/Nonliposomal Daunorubicin and Doxorubicin for Multiple Tumor Cell Types

Abstract

Anthracyclines, including daunorubicin (DnR) and doxorubicin (DoX), have shown clinical chemotherapeutic utility, albeit in association with cumulative dose-associated cardiotoxicities. Despite structural similarity, however, DnR and DoX treatments have been directed toward leukemias and solid tumor types, respectively. Due to a paucity of in vitro data regarding differential use of DnR or DoX, we assessed the cytotoxicity of these compounds against solid and hematological tumor cell types. In addition, we examined liposomal formulations of DnR (L-DnR) and DoX (PEG-DoX), which, in contrast to DnR or DoX, demonstrate antineoplastic activity with reduced cardiotoxicity in vivo. Accordingly, cytotoxicity testing (with [methyl/-(3)H]thymidine incorporation) of DnR, DoX, L-DnR, and PEG-DoX on a range of different human tumor cell lines (e.g., breast, lung, ovarian, prostate, melanoma, lymphoma, and leukemia tumor cell types) was performed. Our data indicate comparable activity for DnR, DoX, or L-DnR in all tumor cell types examined [e.g., SK-BR-3 (breast adenocarcinoma) cells: IC50 values = 5.9, 9.1, and 4.7 ng/mL for DnR, DoX, and L-DnR respectively]. In addition, several solid tumor cell types were more responsive to DnR than DoX [e.g., DU-145 (prostate carcinoma) cells: IC50 values = 10.4 and 41.2 ng/mL for DnR and DoX, respectively; p >. 001]. Interestingly, PEG-DoX was substantively less effective for all tumor cells (IC50 values were about 100-10,000 times greater for PEG-DoX than for DnR, DoX, or L-DnR; p >. 001, all cases). Reduced PEG-DoX activity in vitro may be related to polyethylene glycol (PEG) moieties present on the liposomal exterior of PEG-DoX, which are not present on L-DnR. Nonetheless, taken together, these data suggest that DnR and DoX demonstrate comparable efficacy in vitro and that specific liposomal encapsulation (L-DnR) does not mitigate DnR efficacy in vitro.

A phase I dose-escalating study of DaunoXome, liposomal daunorubicin, in metastatic breast cancer

“…For example idarubicin, esorubicin and carcinomycin had inferior response rates to doxorubicin and/or epirubicin (Rozencweig et al, 1984;Bonfante et al, 1986;Lopez et al, 1989). However, in vitro studies indicate that daunorubicin has equivalent cytotoxicity to doxorubicin in breast adenocarcinoma lines (Wiles et al, 1997). Furthermore, a preliminary report presented by Hupperets et al (1996) indicated that DaunoXome 100 mg m 2 every 21 days for up to 24 weeks had encouraging single agent anti-tumour activity in metastatic breast cancer with objective tumour responses in three and stable disease in seven out of 11 treated patients (Anonymous, 1996).…”

Cellular Uptake of Liposomal Daunorubicin and the Induction of Apoptosis

“…These ndings may re ect the physical properties of L PEG -DoX, in which a hydrophilic coating of PEG shields the liposome from interactions with soluble molecules and the cell surface (Cabanes et al 1998;Gabizon and Martin 1997;Goren et al 1996;Horowitz, Barenholz, and Gabizon 1992;Papahadjopoulos, Allen, and Gabizon 1991). Reduced in vitro cytotoxic activity of L PEG -DoX, compared with that of DoX, has been reported for a variety of tumor cell lines (Wiles et al 1997) and may be related to reduced release of DoX from the aqueous interior of the liposomes, or it may re ect reduced cellular contact with DoX associated with the liposome bilayer. Bearing in mind evidence that DoX has the capability of inducing cytotoxicity without internalization, the steric barrier effect produced by PEG may hinder DoX/cell interactions, resulting in the inability of L PEG -DoX to initiate early apoptosis.…”

Tat peptide and hexadecylphosphocholine introduction into pegylated liposomal doxorubicin: An in vitro and in vivo study on drug cellular delivery, release, biodistribution and antitumor activity

“…3). Dox fluorescence in liposome is self-quenched, which retrieves on releasing Dox from liposomes and dilution in media (Wiles et al, 1997). An immediate burst release occurred in 100 Tat-liposomes, which was not detected in the case of naïve liposomes.…”

“…Leakage stability of the liposomes was monitored in RPMI 1640 media containing 30% fetal calf serum (FCS) based on self-quenching of liposomal Dox and dequenching upon Dox release (Wiles et al, 1997). The FCS used in this experiment was not decomplemented by heating at 60 o C. Liposomes were added to the media (1; 9 v/v) and incubated at 37 o C, from which samples …”