Hypersensitivity to cisplatin after hRev3 mRNA knockdown in head and neck squamous cell carcinoma cells

Abstract

Abstract. Resistance to platinum-based chemotherapy frequently poses a significant problem in the treatment of head and neck squamous cell carcinomas (HNSCCs). In this study, we isolated cisplatin-resistant UM-SCC-23 CDDP/R cells from a UM-SCC-23 head and neck squamous cell carcinoma cell line. The UM-SCC-23 CDDP/R cells were approximately 3.5-fold more resistant to cisplatin than the UM-SCC-23 cells. Translesion DNA synthesis (TLS) is one of the major pathways involved in post-replication repair. To ascertain whether TLS is involved in cisplatin resistance in human cancer cells, we analyzed expression of the Rev3 gene, which encodes the catalytic subunit of DNA polymerase ζ (Polζ), using quantitative PCR. Expression of hRev3 mRNA in the UM-SCC-23 CDDP/R cells was approximately 1.4-fold higher than in the UM-SCC-23 cells. In both types of cells, expression of hRev3 mRNA was suppressed using siRNAs. Cisplatin sensitivity after hRev3 mRNA knockdown increased approximately 2-fold in UM-SCC-23 cells and approximately 3-fold in UM-SCC-23 CDDP/R cells. This study suggests that hRev3 knockdown with siRNAs increases sensitivity to cisplatin. Inhibition of the hRev3 gene may therefore prove to be a novel clinical strategy for reducing resistance to platinumbased chemotherapy in HNSCC. IntroductionCisplatin-based chemotherapy is widely used in the management of locally-advanced head and neck squamous cell carcinoma (HNSCC). However, recurrence often occurs following primary treatment, and treatment of recurrent tumors frequently fails due to resistance to therapeutic agents, including cisplatin (1). Although, to date, there have been many studies concerning the mechanisms of chemoresistance, effective strategies against chemoresistance in HNSCC (2-4) have yet to be devised.The major cytotoxic effect of cisplatin is through the formation of DNA damage, such as DNA-interstrand crosslinks (4). After exposure to cisplatin, cells show one of two reactions: the induction of apoptosis through signal transduction, trigged by DNA damage and resulting in cell death, or the repair of DNA damage for cell survival (5).Translesion DNA synthesis (TLS) and homologous recombination (HR) are the two major pathways involved in post replication repair (6). A number of TLS polymerases have been identified in Saccharomyces cerevisiae and mammals (7).Candidates for translesion synthesis past bulky DNA adducts in vivo include members of the DNA polymerase X (polymerase ß, polymerase μ, polymerase λ), polymerase B (polymerase ζ) and polymerase Y (Rev1, polymerase η, polymerase τ, polymerase κ) families. Of these, DNA polymerase η exhibits the highest translesion activity for the cisplatin adduct, followed by polymerase μ and polymerase ζ (8).The Rev3 and Rev7 genes encode the catalytic subunit of DNA polymerase ζ (Polζ) (7). Inactivation of the Rev3 gene sensitized chicken cells to cisplatin and to various DNA damaging agents, such as UV, methyl methanesulfonate and ionizing radiation. hRev3 antisense-expressing human fibroblasts demonstrated hyp...

Expression of DNA Translesion Synthesis Polymerase η in Head and Neck Squamous Cell Cancer Predicts Resistance to Gemcitabine and Cisplatin-Based Chemotherapy

“…reported that Pol η mRNA levels in non-small cell lung cancer (NSCLC) cell lines were significantly induced by cisplatin [19]. A previous cellular study has shown that the downregulation of DNA lesion bypass polymerase ζ (Pol ζ) in the head and neck squamous carcinoma cells sensitizes cells to cisplatin, and inhibition of hRev3 gene expression was suggested to be a potential clinical strategy to reducing resistance against cisplatin in HNSCC [56]. In this study, we observed that the expression level of Pol η level increased in 6 cases (6/9) of the 9 patients who were resistant to platinum or gemcitabine based chemotherapy, which has not been reported before.…”

Eukaryotic DNA polymerase ζ

“…Testing of Pol ζ expression and its activity in patients may provide important diagnostic information and guide to a personalized therapeutic approach in cancer therapy. In support of this, downregulation of REV3L expression significantly enhanced the sensitivity of human cancer cells to cisplatin therapy [58,62]. Therefore, Pol ζ represents a promising target for the treatment of chemotherapy-resistant tumors.…”

Human Pol ζ purified with accessory subunits is active in translesion DNA synthesis and complements Pol η in cisplatin bypass

“…Pol ζ and Pol η Synergistically Bypass an Intrastrand Cisplatin CrossLink. Human Pol ζ has been implicated in resistance to platinumbased chemotherapies (20)(21)(22), and knockdown of REV3L sensitizes malignant cells to cisplatin treatment (21,43). We compared the catalytic activity and accuracy of Pol ζ4 in synthesizing DNA in the presence or absence of a 1,2-intrastrand d(GpG)-cisplatin cross-link (abbreviated as Pt-GG hereafter).…”