Induction of apoptosis using 2′,2′difluorodeoxycytidine (gemcitabine) in combination with antimetabolites or anthracyclines on malignant lymphatic and myeloid cells. Antagonism or synergism depends on incubation schedule and origin of neoplastic cells

Abstract

Induction of apoptosis in vitro using gemcitabine (dFdC) in combination with cladribine (2-CdA) and other cytotoxic drugs on malignant mononuclear cells (MNCs) of patients with acute myeloid leukemia (AML, n=20) and chronic lymphocytic leukemia (CLL, n =20) in myeloid (HL60, HEL) and lymphatic cell lines (HUT78, JURKAT) was investigated using different incubation conditions (simultaneous and consecutive). Furthermore, the influence of dFdC on the level of intracellular metabolites of 2-CdA was studied using high-performance liquid chromatography (HPLC). Apoptosis was evaluated using flow cytometry with 7-aminoactinomycin D. In MNCs of patients with CLL, dFdC + 2-CdA showed an antagonistic effect when applied simultaneously. This antagonism was reduced by consecutive application. The combination of dFdC with doxorubicin was synergistic, independent of incubation schedule. In blasts from newly diagnosed patients with de novo AML, all drug combinations (dFdC+2-CdA, doxorubicin, or cytosine arabinoside) were antagonistic by simultaneous incubation. Reduced antagonism or even synergism was shown (P<0.001) by consecutive incubation. The simultaneous combination of dFdC with 2-CdA in all tested cell lines resulted in a competitive inhibition on the rate of apoptosis. By changing the incubation period to a consecutive schedule, the antagonism was diminished or synergism of apoptosis was measured (P< 0.001). Using similar incubation conditions, these experiments were supported by HPLC measurement of intracellular metabolites of 2-CdA influenced by dFdC application. In conclusion, we demonstrated that the efficacy of dFdC in vitro in combination with other cytotoxic drugs depends on the incubation condition and on the origin of neoplastic cells (lymphatic vs myeloid). The data suggest that simultaneous combination therapy with purine and pyrimidine analogues may not improve the clinical efficacy of one or the other drug administered alone.

Combined effects of a third-generation bisphosphonate, zoledronic acid with other anticancer agents against murine osteosarcoma

“…The fraction affected (Fa) (i.e. Fa of 0.25 is equivalent to 75% viable cells) and the combination index (CI) were calculated with CalcuSyn (Chow et al, 2000). This method enables quantification of synergism (CIo1) and antagonism (CI41) at different dose and effect levels.…”

Phase I/II trial of doxorubicin and fixed dose-rate infusion gemcitabine in advanced soft tissue sarcomas: a GEIS study

“…In those studies, only gemcitabine was given on day 1, whereas on day 8 gemcitabine preceded TXT, a sequence that was synergistic in an osteosarcoma and a breast cancer cell line (Leu et al, 2004); however, in lung cancer cell lines, the opposite sequence was more effective (Zoli et al, 1999). Similarly, in vitro studies have shown that the effects of a combination of DXR and gemcitabine depend both on the sequence of administration and on the particular cell line studied (Chow et al, 2000;Zoli et al, 2004). The administration of gemcitabine followed by DXR, or the delivery of DXR on day 8, would perhaps offer a better therapeutic index than the present schedule, which cannot be recommended for further study.…”

Pegylated liposomal doxorubicin and gemcitabine in the front-line treatment of recurrent/metastatic breast cancer: a multicentre phase II study

“…Moreover, the different mechanisms of action of the two drugs, which have been shown to synergise in in vitro and in vivo models (Chow et al, 2000;Gallo et al, 2006), as well as the nonoverlapping toxicity profiles, further strengthened the rationale for their combination. Indeed, combined administration of PLD/GEM has been successfully investigated in ovarian cancer (Ferrandina et al, 2005), as well as in recurrent/metastatic breast cancer patients; in particular, in the latter subset of patients, an overall response rate between 26 and 52% (median duration of response ¼ 5.5-7 months), with an acceptable toxicity profile, has been reported in three phase II studies (Rivera et al, 2003;Fabi et al, 2006;UlrichPur et al, 2007).…”