Combination of a MDR1-targeted replicative adenovirus and chemotherapy for the therapy of pretreated ovarian cancer

Abstract

Purpose: Targeted oncolytic adenoviruses capable of replication selectively in cancer cells are an appealing approach for the treatment of various cancer types refractory to conventional therapies. The aim of this study was to evaluate the effect of Ad5/3MDR1E1, a multidrug resistance gene 1 (MDR1)-targeted fiber-modified replication-competent adenovirus for the therapy of platinum-pretreated ovarian cancer in combination with cytostatic agents.

Methods: MDR1-specific tumor cell killing of Ad5/3MDR1E1 was systematically evaluated in chemotherapy naïve and pretreated ovarian cancer cells in vitro. Combinations of Ad5/3MDR1E1 and cytostatic agents were studied in vivo and in vitro. An in vivo hepatotoxicity model was used to evaluate liver toxicity.

Results: We demonstrate efficient oncolysis of Ad5/3MDR1E1 in chemotherapy-resistant ovarian cancer cells as well as therapeutic efficacy in an orthotopic mouse model. Further, combining Ad5/3MDR1E1 with paclitaxel resulted in greater therapeutic benefit than either agent alone.

Conclusion: These preclinical data suggest that a fiber-modified adenovirus vector under the control of the MDR1 promoter represents a promising treatment strategy for platinum-pretreated ovarian cancer as a single agent or in combination with conventional anticancer drugs.

Fig. 1

Ad5/3MDR1E1 and Ad5/3MDR1E1Δ24 kill chemotherapy-resistant tumor cells specifically. Chemotherapy naïve SKOV-3 cells (a) and ADR-pretreated SKOV-3 150 cells (b) were infected with Ad5/3MDR1E1, Ad5/3MDR1E1Δ24, Ad5/3Δ24, Ad5wt and Ad5/3CMVluc (E1-deleted control virus). Oncolysis was evaluated by crystal violet staining

Fig. 2

Immunohistochemical staining of viral E1A in a co-culture of fibroblasts and chemotherapy-resistant Skov-3 90 ADR cells after infection with Ad5/3MDR1E1 at an MOI of 1. Immunohistochemical analysis displays strong immunoreactivity for Skov-3 90 ADR cells. Binding of antibodies was visualized by a peroxidase catalyzed color reaction using 3′,3′-diaminobenzidine tetrahydrochloride. For counter staining, Mayer′s haemalaun was used. a 2 days after infection, b 3 days after infection, c 5 days after infection, d negative control (red arrows = Skov-3 90 ADR cells, blue arrows = fibroblasts, magnificationX = 200)

Fig. 3

Combination of Ad5/3MDR1E1 and paclitaxel in vitro. Viability of cisplatin-pretreated SKOV-3 cells after infection with (a) Ad5/3CMVluc (E1-deleted control virus) or (b) Ad5/3MDR1E1 in combination with paclitaxel. Cells were infected at indicated doses of virus with paclitaxel, and viability was measured with MTS assay. Combination of Ad5/3MDR1E1 and paclitaxel resulted in significant synergy. The OD₄₅₀ values of uninfected cells were set as 100%. Data were presented as means ± SD of triplicate experiments

Fig. 4

Antitumor efficacy of combination of Ad5/3MDR1E1 and cytostatic agents in an orthotopic mouse model of peritoneally disseminated platinum-pretreated ovarian cancer. Cisplatin-pretreated SKOV3.ip1 cells were injected intraperitoneally (i.p.) into SCID mice, and advanced carcinomatosis was allowed to develop for 10 days. Mice were injected i.p. with Ad5MDRLuc (negative control), Ad5/3MDR1E1 only, Paclitaxel only, Ad5/3MDR1E1 + Paclitaxel and Ad5/3MDR1E1 + Paclitaxel + Bevacizumab, respectively

Fig. 5

Evaluation of liver toxicity in the mouse. Female C57BL/6 mice were treated i.p. with 5 × 10¹⁰ vp of Ad5MDRLuc (negative control), Ad5/3MDR1E1 + Paclitaxel and Ad5/3MDR1E1 + Paclitaxel + Bevacizumab (a–c). After 96 h, the livers were harvested and fixed in 10% buffered formalin. A series of paraffin-embedded sections were taken and stained with H&E under standard conditions. Histopathology was scored in a blinded manner by an experienced pathologist