Altered catalytic activity of and DNA cleavage by DNA topoisomerase II from human leukemic cells selected for resistance to VM-26

Abstract

The simultaneous development of resistance to the cytotoxic effects of several classes of natural product anticancer drugs, after exposure to only one of these agents, is referred to as multiple drug resistance (MDR). At least two distinct mechanisms for MDR have been postulated: that associated with P-glycoprotein and that thought to be due to an alteration in DNA topoisomerase II activity (at-MDR). We describe studies with two sublines of human leukemic CCRF-CEM cells approximately 50-fold resistant (CEM/VM-1) and approximately 140-fold resistant (CEM/VM-1-5) to VM-26, a drug known to interfere with DNA topoisomerase II activity. Each of these lines is cross-resistant to other drugs known to affect topoisomerase II but not cross-resistant to vinblastine, an inhibitor of mitotic spindle formation. We found little difference in the amount of immunoreactive DNA topoisomerase II in 1.0 M NaCl nuclear extracts of the two resistant and parental cell lines. However, topoisomerase II in nuclear extracts of the resistant sublines is altered in both catalytic activity (unknotting) of and DNA cleavage by this enzyme. Also, the rate at which catenation occurs is 20-30-fold slower with the CEM/VM-1-5 preparations. The effect of VM-26 on both strand passing and DNA cleavage is inversely related to the degree of primary resistance of each cell line. Our data support the hypothesis that at-MDR is due to an alteration in topoisomerase II or in a factor modulating its activity.

Immunohistochemical detection of DNA topoisomerase IIα, P-glycoprotein and multidrug resistance protein (MRP) in small-cell and non-small-cell lung cancer

“…In non-malignant cells, MRP was often seen in superficial bronchial epithelium, however, in contrast to P-gp, MRP was also commonly observed in macrophages and scattered lymphocytes (Figure 4), in agreement with a study using mRNA in situ hybridization (Thomas et al, 1994). In SCLC, after treatment, an increase in the proportion of positive cells was observed in four (Cole et al, 1992;Borst et al, 1993), or changes in their drug target topo-IIa, namely at-MDR (Pommier et al, 1986;Danks et al, 1988). The latter, which was first described in a SCLC cell line by de Jong et al (1990), usually exists as a down-regulation of enzyme amount, but can also be due to mutations leading to a decreased drug sensitivity.…”

“…Despite initial response rates of 70-80%, patients with SCLC usually relapse with a clinically drug-resistant tumour, and the 2-year survival is only approximately 5% (Hansen, 1992). Extensive experimental research has documented the existence of several cellular resistance mechanisms towards topo-LI poisons such as etoposide, namely either a reduction and/or mutation in the enzyme itself, called the altered topoisomerase 11 multidrug resistance phenotype (at-MDR) (Pommier et al, 1986;Danks et al, 1988), or two well-characterized drug efflux pumps, P-glycoprotein (P-gp) (Borst et al, 1993) and MRP (Cole et al, 1992), both of which have been shown in transfection studies to be sufficient to confer resistance. The aim of the present study was to study the expression of these three factors, topo-IIa, P-gp and MRP, in the different histological types of lung cancer and in addition to investigate whether changes in their incidence occurred in SCLC after treatment with etoposide or teniposide.…”

Resistance to the new anti-cancer phospholipid ilmofosine (BM 41 440)

“…The resistance pattern to vinblastine and colchicine also reflect the expression of the wild-type and mutant MDR] gene. In atypical multidrug-resistant CEMNVM-1 cells, the resistance is associated with an altered topoisomerase II gene (Danks et al, 1988). A Meth A subline resistant to ilmofosine (MR) was obtained from the parental sensitive cells (MS) as described (Herrmann, 1985).…”

“…CEM/VLBCoO, CCRF/VCR1000 and CCRF-ADR5000 cells exhibit modest cross-resistance to ilmofosine (Table 1). In CEMIVM-1 cells, multidrug resistance is not due to expression of MDRI but is associated with an alteration in the topoisomerase II gene (Danks et al, 1988 Gly/Val mutation in position 185 (HeLa-MDRI-V185) are multidrug resistant and exhibit cross-resistance to ilmofosine, indicating that expression of the MDRJ gene is sufficient to cause cross-resistance to ilmofosine (Table 1). The extent of resistance to ilmofosine in MCF-7/ADR is similar to that to doxorubicin (resistance factor 7.13 and 8.7 respectively); in the other resistant cell lines tested, the resistance to ilmofosine is considerably lower than to vinblastine and doxorubicin (Table 1).…”

Comparison of the cytotoxic activity of melphalan with L-prolyl-m-L-sarcolysyl-L-p-fluorophenylalanine in human tumour cell lines and primary cultures of tumour cells from patients

“…expresses an atypical MDR. which is proposed to be topoisomerase LI (topoll) associated (Danks et al 1987(Danks et al . 1988.…”