Cancer Resistance to Type II Topoisomerase Inhibitors

Pilati, Pierluigi; Nitti, Donato; Mocellin, Simone

doi:10.2174/092986712802002473

Cited by 27 publications

(25 citation statements)

References 75 publications

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“…Intrinsic and acquired chemoresistance to these drugs continues to be a major complication in cancer treatment. Although many resistance mechanisms have been defined (Vassetzky et al, 1995;Pilati et al, 2012;Ganapathi and Ganapathi, 2013), acquired resistance to TOP2a inhibitors is frequently associated with decreased TOP2a/170 nuclear levels (Mirski et al, 1993(Mirski et al, , 2000Harker et al, 1995;Mirski and Cole, 1995;Wessel et al, 1997;Yu et al, 1997;Burgess et al, 2008). In addition, our laboratory previously demonstrated reduction in TOP2a/170 levels in etoposide-resistant K/VP.5 compared with parental K562 cells (Ritke et al, 1994a;Kanagasabai et al, 2017) due in part to changes in TOP2a/170 mRNA stability (Ritke and Yalowich, 1993).…”

Section: Discussionmentioning

confidence: 99%

The Novel C-terminal Truncated 90-kDa Isoform of Topoisomerase IIα (TOP2α/90) Is a Determinant of Etoposide Resistance in K562 Leukemia Cells via Heterodimerization with the TOP2α/170 Isoform

et al. 2018

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DNA topoisomerase II (170 kDa, TOP2/170) is essential in proliferating cells by resolving DNA topological entanglements during chromosome condensation, replication, and segregation. We previously characterized a C-terminally truncated isoform (TOP2/90), detectable in human leukemia K562 cells but more abundantly expressed in a clonal subline, K/VP.5, with acquired resistance to the anticancer agent etoposide. TOP2/90 (786 aa) is the translation product of a TOP2 mRNA that retains a processed intron 19. TOP2/90 lacks the active-site tyrosine-805 required to generate double-strand DNA breaks as well as nuclear localization signals present in the TOP2/170 isoform (1531 aa). Here, we found that TOP2/90, like TOP2/170, was detectable in the nucleus and cytoplasm of K562 and K/VP.5 cells. Coimmunoprecipitation of endogenous TOP2/90 and TOP2/170 demonstrated heterodimerization of these isoforms. Forced expression of TOP2/90 in K562 cells suppressed, whereas siRNA-mediated knockdown of TOP2/90 in K/VP.5 cells enhanced, etoposide-mediated DNA strand breaks compared with similarly treated cells transfected with empty vector or control siRNAs, respectively. In addition, forced expression of TOP2/90 in K562 cells inhibited etoposide cytotoxicity assessed by clonogenic assays. qPCR and immunoassays demonstrated TOP2/90 mRNA and protein expression in normal human tissues/cells and in leukemia cells from patients. Together, results strongly suggest that TOP2/90 expression decreases drug-induced TOP2-DNA covalent complexes and is a determinant of chemoresistance through a dominant-negative effect related to heterodimerization with TOP2/170. Alternative processing of TOP2 pre-mRNA, and subsequent synthesis of TOP2/90, may be an important mechanism regulating the formation and/or stability of cytotoxic TOP2/170-DNA covalent complexes in response to TOP2-targeting agents.

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Section: Discussionmentioning

confidence: 99%

The Novel C-terminal Truncated 90-kDa Isoform of Topoisomerase IIα (TOP2α/90) Is a Determinant of Etoposide Resistance in K562 Leukemia Cells via Heterodimerization with the TOP2α/170 Isoform

et al. 2018

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“…The efficacy of TOP2a inhibitors is limited by intrinsic and acquired chemoresistance (Chen and Liu, 1994;Pilati et al, 2012;Ganapathi and Ganapathi, 2013). Tumor cell lines resistant to TOP2a inhibitors have been selected whose acquired resistance is attributed, in part, to a reduction of TOP2a/170 enzyme levels associated with alternative spliced TOP2a mRNAs that encode novel C-terminal truncated forms of TOP2a/170 (Harker et al, 1995;Mirski and Cole, 1995;Mo and Beck, 1997;Yu et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Alternative RNA Processing of Topoisomerase IIα in Etoposide-Resistant Human Leukemia K562 Cells: Intron Retention Results in a Novel C-Terminal Truncated 90-kDa Isoform

Kanagasabai

Serdar

Karmahapatra

et al. 2016

J Pharmacol Exp Ther

125

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DNA topoisomerase IIα (TOP2α) is a prominent target for anticancer drugs whose clinical efficacy is often limited by chemoresistance. Using antibody specific for the N-terminal of TOP2α, immunoassays indicated the existence of two TOP2α isoforms, 170 and 90 kDa, present in K562 leukemia cells and in an acquired etoposide (VP-16)-resistant clone (K/VP.5). TOP2α/90 expression was dramatically increased in etoposide-resistant K/VP.5 compared with parental K562 cells. We hypothesized that TOP2α/90 was the translation product of novel alternatively processed pre-mRNA, confirmed by 3'-rapid amplification of cDNA ends, polymerase chain reaction, and sequencing. TOP2α/90 mRNA includes retained intron 19, which harbors an in-frame stop codon, and two consensus poly(A) sites. The processed transcript is polyadenylated. TOP2α/90 mRNA encodes a 90,076-Da translation product missing the C-terminal 770 amino acids of TOP2α/170, replaced by 25 unique amino acids through translation of the exon 19/intron 19 read-through. Immunoassays, utilizing antisera raised against these unique amino acids, confirmed that TOP2α/90 is expressed in both cell types, with overexpression in K/VP.5 cells. Immunodetection of complex of enzyme-to-DNA and single-cell gel electrophoresis (Comet) assays demonstrated that K562 cells transfected with a TOP2α/90 expression plasmid exhibited reduced etoposide-mediated TOP2α-DNA covalent complexes and decreased etoposide-induced DNA damage, respectively, compared with similarly treated K562 cells transfected with empty vector. Because TOP2α/90 lacks the active site tyrosine (Tyr) of full-length TOP2α, these results strongly suggest that TOP2α/90 exhibits dominant-negative properties. Further studies are underway to characterize the mechanism(s) by which TOP2α/90 plays a role in acquired resistance to etoposide and other TOP2α targeting agents.

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“…Although this class of inhibitors are among the most effective and most commonly used anticancer drugs, the emergence of drug resistance often hampers their clinical efficacy for the treatment of cancers. 37 – 39 …”

Section: Main Subjectmentioning

confidence: 99%

Dual Inhibitors Against Topoisomerases and Histone Deacetylases

Seo

2015

J Cancer Prev

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Topoisomerases and histone deacetylases (HDACs) are considered as important therapeutic targets for a wide range of cancers, due to their association with the initiation, proliferation and survival of cancer cells. Topoisomerases are involved in the cleavage and religation processes of DNA, while HDACs regulate a dynamic epigenetic modification of the lysine amino acid on various proteins. Extensive studies have been undertaken to discover small molecule inhibitor of each protein and thereby, several drugs have been transpired from this effort and successfully approved for clinical use. However, the inherent heterogeneity and multiple genetic abnormalities of cancers challenge the clinical application of these single targeted drugs. In order to overcome the limitations of a single target approach, a novel approach, simultaneously targeting topoisomerases and HDACs with a single molecule has been recently employed and attracted much attention of medicinal chemists in drug discovery. This review highlights the current studies on the discovery of dual inhibitors against topoisomerases and HDACs, provides their pharmacological aspects and advantages, and discusses the challenges and promise of the dual inhibitors.

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Cancer Resistance to Type II Topoisomerase Inhibitors

Cited by 27 publications

References 75 publications

The Novel C-terminal Truncated 90-kDa Isoform of Topoisomerase IIα (TOP2α/90) Is a Determinant of Etoposide Resistance in K562 Leukemia Cells via Heterodimerization with the TOP2α/170 Isoform

The Novel C-terminal Truncated 90-kDa Isoform of Topoisomerase IIα (TOP2α/90) Is a Determinant of Etoposide Resistance in K562 Leukemia Cells via Heterodimerization with the TOP2α/170 Isoform

Alternative RNA Processing of Topoisomerase IIα in Etoposide-Resistant Human Leukemia K562 Cells: Intron Retention Results in a Novel C-Terminal Truncated 90-kDa Isoform

Dual Inhibitors Against Topoisomerases and Histone Deacetylases

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