MDM2 antagonist nutlin-3a reverses mitoxantrone resistance by inhibiting breast cancer resistance protein mediated drug transport

Abstract

Breast cancer resistance protein (BCRP; ABCG2), a clinical marker for identifying the side population (SP) cancer stem cell subgroup, affects intestinal absorption, brain penetration, hepatobiliary excretion, and multidrug resistance of many anti-cancer drugs. Nutlin-3a is currently under pre-clinical investigation in a variety of solid tumor and leukemia models as a p53 reactivation agent, and has been recently demonstrated to also have p53 independent actions in cancer cells. In the present study, we first report that nutlin-3a can inhibit the efflux function of BCRP. We observed that although the nutlin-3a IC50 did not differ between BCRP over-expressing and vector control cells, nutlin-3a treatment significantly potentiated the cells to treatment with the BCRP substrate mitoxantrone. Combination index calculations suggested synergism between nutlin-3a and mitoxantrone in cell lines over-expressing BCRP. Upon further investigation, it was confirmed that nutlin-3a increased the intracellular accumulation of BCRP substrates such as mitoxantrone and Hoechst 33342 in cells expressing functional BCRP without altering the expression level or localization of BCRP. Interestingly, nutlin-3b, considered virtually “inactive” in disrupting the MDM2/p53 interaction, reversed Hoechst 33342 efflux with the same potency as nutlin-3a. Intracellular accumulation and bi-directional transport studies using MDCKII cells suggested that nutlin-3a is not a substrate of BCRP. Additionally, an ATPase assay using Sf9 insect cell membranes over-expressing wild-type BCRP indicated that nutlin-3a inhibits BCRP ATPase activity in a dose-dependent fashion. In conclusion, our studies demonstrate that nutlin-3a inhibits BCRP efflux function, which consequently reverses BCRP-related drug resistance.

Ovarian cancer: Current status and strategies for improving therapeutic outcomes

“…67 Upregulated BRCP is known to protect cancer cells from topotecan 66,68 and mitoxantrone. 67,68 The mechanism of normal epithelial cells changes to drug resistant cancerous cells is by activating epithelial-mesenchymal transition (EMT). 34 Beginning of their transformation malignant epithelial cells go through angiogenesis and massive propagation.…”

Effects of the MDM-2 inhibitor Nutlin-3a on PDAC cells containing and lacking WT-TP53 on sensitivity to chemotherapy, signal transduction inhibitors and nutraceuticals

“…Recently, we have summarized MDM2 and related MDM4 proteins and their inhibitors and some of the mechanisms of resistance to these inhibitors (McCubrey et al, 2017). The potential for inhibitors such as nutlin-3a and other MDM2 inhibitors either alone or in combination with chemotherapeutic drugs to suppress the growth of tumor cells containing WT-TP53 or mutant TP53 has been discussed (Ambrosini et al, 2007;Zhang et al, 2011;Conradt et al, 2013).…”

Resistance acquisition to MDM2 inhibitors

“…Notably, nutlin-3 also exerted anticancer effects in cells that did not express functional p53 through mechanisms that involve p73 and E2F1 activation [7,34,35] and induction of differentiation [33]. Off-target effects of nutlin-3 include interference with ABC (ATP-binding cassette) transporters and anti-apoptotic Bcl-2 family members [26,36,37].…”