A comparison of response to cisplatin, radiation and combined treatment for cells deficient in recombination repair pathways

ArticleinAnticancer research 25(1A):53-8 · January 2005with17 Reads
Source: PubMed
Abstract
The responses of cells with mutated DNA repair pathways were compared for cisplatin, radiation and combination treatments. The knockout of the nonhomologous endjoining (NHEJ) pathway resulted in increased radiation sensitivity, but no change in cisplatin response in the mouse cells and increased radiosensitivity but decreased cisplatin sensitivity in chicken cells. The mutation of the homologous recombination repair (HR) pathway through XRCC3 in CHO cells resulted in increased radiation and cisplatin sensitivity and to a lesser extent for the Rad54 knockout in the DT40 chicken cells. The combination treatments of cisplatin and radiation showed that inhibition of the HR repair pathway resulted in super additive effects while the inhibition of the NHEJ pathway in DT40 had no effect. In mouse cells the knockout of the NHEJ pathway resulted in reduced super additivity compared to the parental cell lines. These data show that radiation, cisplatin and combination treatment damage is affected differently by the various DNA repair pathways, which could have a range of effects on combination treatments in tumour cells expressing different levels of DNA repair in the various repair pathways.
    • "Supporting our data are several studies which suggest a clear role for CDDP impairing DNA DSB repair. For instance, a deficiency in repair of CDDP lesions on DNA augments CDDP radiosensiti- zation [17,28,29]. Additionally, treatment of NHEJ-deficient cells with CDDP-IR show increased toxicity, but no longer show a synergistic interaction, highlighting the importance of NHEJ catalyzed DSB repair to the cooperative cytotoxicity of CDDP-IR co-treatment [17,28]. "
    [Show abstract] [Hide abstract] ABSTRACT: Non-small cell lung cancers (NSCLC) are commonly treated with a platinum-based chemotherapy such as cisplatin (CDDP) in combination with ionizing radiation (IR). Although clinical trials have demonstrated that the combination of CDDP and IR appear to be synergistic in terms of therapeutic efficacy, the mechanism of synergism remains largely uncharacterized. We investigated the role of the DNA damage response (DDR) in CDDP radiosensitization using two NSCLC cell lines. Using clonogenic survival assays, we determined that the cooperative cytotoxicity of CDDP and IR treatment is sequence dependent, requiring administration of CDDP prior to IR (CDDP-IR). We identified and interrogated the unique time and agent-dependent activation of the DDR in NSCLC cells treated with cisplatin-IR combination therapy. Compared to treatment with CDDP or IR alone, CDDP-IR combination treatment led to persistence of γH2Ax foci, a marker of DNA double-strand breaks (DSB), for up to 24 h after treatment. Interestingly, pharmacologic inhibition of DDR sensor kinases revealed the persistence of γ-H2Ax foci in CDDP-IR treated cells is independent of kinase activation. Taken together, our data suggest that delayed repair of DSBs in NSCLC cells treated with CDDP-IR contributes to CDDP radiosensitization and that alterations of the DDR pathways by inhibition of specific DDR kinases can augment CDDP-IR cytotoxicity by a complementary mechanism.
    Full-text · Article · Mar 2016
    • "Although it is clear that platinum drugs and radiation in CRT modalities increase tumor cell killing, improve locoregional control of tumors, and enhance patient survival [4, 5], the optimum schedule of the combination and the underlying mechanisms of their synergistic action have not been yet defined [6, 7]. Since DNA is the common target of both radiation and platinum chemotherapeutic agents, most studies have focused on the structural and functional alteration of DNA resulting from the combination [8, 9]. One possible mechanism responsible for the observed synergy is enhancement in immediate (secondary) species induced by primary radiation in the vicinity of the binding site of the platinum compounds (Pt compounds) to DNA [10, 11]. "
    [Show abstract] [Hide abstract] ABSTRACT: Dry films of platinum chemotherapeutic drugs covalently bound to plasmid DNA (Pt-DNA) represent a useful experimental model to investigate direct effects of radiation on DNA in close proximity to platinum chemotherapeutic agents, a situation of considerable relevance to understand the mechanisms underlying concomitant chemoradiation therapy. In the present paper we determine the optimum conditions for preparation of Pt-DNA films for use in irradiation experiments. Incubation conditions for DNA platination reactions have a substantial effect on the structure of Pt-DNA in the films. The quantity of Pt bound to DNA as a function of incubation time and temperature is measured by inductively coupled plasma mass spectroscopy. Our experiments indicate that chemical instability and damage to DNA in Pt-DNA samples increase when DNA platination occurs at 37(°)C for 24 hours, the condition which has been extensively used for in vitro studies. Platination of DNA for the formation of Pt-DNA films is optimal at room temperature for reaction times less than 2 hours. By increasing the concentration of Pt compounds relative to DNA and thus accelerating the rate of their mutual binding, it is possible to prepare Pt-DNA samples containing known concentrations of Pt while reducing DNA degradation caused by more lengthy procedures.
    Full-text · Article · Jan 2012
    • "Hence, cellular repair can reduce the effectiveness of chemotherapeutic agents [19]. Similarly, cells with down regulated or deficient repair display increased sensitivity to many DNA-damaging agents [20][21][22]. Conversely, a wide body of literature exists which shows that a loss of repair, especially mismatch repair (MMR), can also result in resistance to a range of agents including busulfan, cisplatin and etoposide, by impairing the ability of the cell to detect the DNA damage and activate apoptosis [23]. It is therefore important to understand the mechanisms involved in damage recognition and repair as this may lead to the design of more effective drugs and may also dictate which tumour types can be most effectively treated with anthracycline adduct therapy. "
    [Show abstract] [Hide abstract] ABSTRACT: Doxorubicin, a widely used anthracycline anticancer agent, acts as a topoisomerase II poison but can also form formaldehyde-mediated DNA adducts. This has led to the development of doxorubicin derivatives such as doxoform, which can readily form adducts with DNA. This work aimed to determine which DNA repair pathways are involved in the recognition and possible repair of anthracycline-DNA adducts. Cell lines lacking functional proteins involved in each of the five main repair pathways, mismatch repair (MMR), base excision repair (BER), nucleotide excision repair (NER), homologous recombination (HR) and non-homologous end-joining (NHEJ) were examined for sensitivity to various anthracycline adduct-forming treatments. The treatments used were doxorubicin, barminomycin (a model adduct-forming anthracycline) and doxoform (a doxorubicin-formaldehyde conjugate). Cells with deficiencies in MMR, BER and NHEJ were equally sensitive to adduct-forming treatments compared to wild type cells and therefore these pathways are unlikely to play a role in the repair of these adducts. Some cells with deficiencies in the NER pathway (specifically, those lacking functional XPB, XPD and XPG), displayed tolerance to adducts induced by both barminomycin and doxoform and also exhibited a decreased level of apoptosis in response to adduct-forming treatments. Conversely, two HR deficient cell lines were shown to be more sensitive to barminomycin and doxoform than HR proficient cells, indicating that this pathway is also involved in the repair response to anthracycline-DNA adducts. These results suggest an unusual damage response pathway to anthracycline adducts involving both NER and HR that could be used to optimise cancer therapy for tumours with either high levels of NER or defective HR. Tumours with either of these characteristics would be predicted to respond particularly well to anthracycline-DNA adduct-forming treatments.
    Article · Mar 2008
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