Decreased transcription-coupled nucleotide excision repair capacity is associated with increased p53- and MLH1-independent apoptosis in response to cisplatin

Lawton J Stubbert,Bruce C Mckay,Jennifer M Smith

doi:10.1186/1471-2407-10-207

Lawton J Stubbert, Bruce C Mckay + Show 1 more

Open Access

https://doi.org/10.1186/1471-2407-10-207

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Journal: BMC Cancer	Publication Date: May 14, 2010
Citations: 113	License type: cc-by

Affiliation: Ottawa Hospital, University of Ottawa

Abstract

BackgroundOne of the most commonly used classes of anti-cancer drugs presently in clinical practice is the platinum-based drugs, including cisplatin. The efficacy of cisplatin therapy is often limited by the emergence of resistant tumours following treatment. Cisplatin resistance is multi-factorial but can be associated with increased DNA repair capacity, mutations in p53 or loss of DNA mismatch repair capacity.MethodsRNA interference (RNAi) was used to reduce the transcription-coupled nucleotide excision repair (TC-NER) capacity of several prostate and colorectal carcinoma cell lines with specific defects in p53 and/or DNA mismatch repair. The effect of small inhibitory RNAs designed to target the CSB (Cockayne syndrome group B) transcript on TC-NER and the sensitivity of cells to cisplatin-induced apoptosis was determined.ResultsThese prostate and colon cancer cell lines were initially TC-NER proficient and RNAi against CSB significantly reduced their DNA repair capacity. Decreased TC-NER capacity was associated with an increase in the sensitivity of tumour cells to cisplatin-induced apoptosis, even in p53 null and DNA mismatch repair-deficient cell lines.ConclusionThe present work indicates that CSB and TC-NER play a prominent role in determining the sensitivity of tumour cells to cisplatin even in the absence of p53 and DNA mismatch repair. These results further suggest that CSB represents a potential target for cancer therapy that may be important to overcome resistance to cisplatin in the clinic.

Highlights

One of the most commonly used classes of anti-cancer drugs presently in clinical practice is the platinum-based drugs, including cisplatin
RNA interference against CSB increased the sensitivity of prostate cancer cells to cisplatin-induced apoptosis Prostate cancer cells (DU145 and PC-3 cells) were transfected with control or anti-CSB siRNAs and CSB protein levels were assessed by immunoblot analysis (Figure 1A)
A single UV-induced dimer in the template strand of an active gene is sufficient to block its expression [34,35,36]. This principal forms the fundamental basis of host cell reactivation (HCR) assay that is commonly used to measure the repair of transcription-blocking DNA lesions [31,36,37,38]

Summary

Introduction

One of the most commonly used classes of anti-cancer drugs presently in clinical practice is the platinum-based drugs, including cisplatin. The effectiveness of cisplatin is dependent on its interaction with DNA This drug forms a variety of DNA adducts but more than 99% of these are intrastrand DNA adducts, most often between adjacent purines, with only a very small number of interstrand-crosslinks and monoadducts [2]. These intrastrand lesions are repaired by the nucleotide excision repair (NER) pathway so the response of tumours to cisplatin and other platinumbased drugs may be affected by nucleotide excision repair capacity of the tumour cells [1]. Global-genomic nucleotide excision repair (GGNER) is responsible for the removal of the vast majority of UV and cisplatin-lesions throughout the genome whereas transcription-coupled nucleotide excision repair (TC-NER) is responsible for the selective removal of only those lesions that are present in the template strand of expressed genes [3,5,10,11,12]

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