TXNL1-XRCC1 pathway regulates cisplatin-induced cell death and contributes to resistance in human gastric cancer

Cisplatin is a cytotoxic platinum compound that triggers DNA crosslinking induced cell death, and is one of the reference drugs used in the treatment of several types of human cancers including gastric cancer. However, intrinsic or acquired drug resistance to cisplatin is very common, and leading to treatment failure. We have recently shown that reduced expression of base excision repair protein XRCC1 (X-ray repair cross complementing group1) in gastric cancerous tissues correlates with a significant survival benefit from adjuvant first-line platinum-based chemotherapy. In this study, we demonstrated the role of XRCC1 in repair of cisplatin-induced DNA lesions and acquired cisplatin resistance in gastric cancer by using cisplatin-sensitive gastric cancer cell lines BGC823 and the cisplatin-resistant gastric cancer cell lines BGC823/cis-diamminedichloridoplatinum(II) (DDP). Our results indicated that the protein expression of XRCC1 was significantly increased in cisplatin-resistant cells and independently contributed to cisplatin resistance. Irinotecan, another chemotherapeutic agent to induce DNA damaging used to treat patients with advanced gastric cancer that progressed on cisplatin, was found to inhibit the expression of XRCC1 effectively, and leading to an increase in the sensitivity of resistant cells to cisplatin. Our proteomic studies further identified a cofactor of 26S proteasome, the thioredoxin-like protein 1 (TXNL1) that downregulated XRCC1 in BGC823/DDP cells via the ubiquitin-proteasome pathway. In conclusion, the TXNL1-XRCC1 is a novel regulatory pathway that has an independent role in cisplatin resistance, indicating a putative drug target for reversing cisplatin resistance in gastric cancer.     

DNA damage responsive miR-33b-3p promoted lung cancer cells survival and cisplatin resistance by targeting p21WAF1/CIP1

Cisplatin is the most potent and widespread used chemotherapy drug for lung cancer treatment. However, the development of resistance to cisplatin is a major obstacle in clinical therapy. The principal mechanism of cisplatin is the induction of DNA damage, thus the capability of DNA damage response (DDR) is a key factor that influences the cisplatin sensitivity of cancer cells. Recent advances have demonstrated that miRNAs (microRNAs) exerted critical roles in DNA damage response; nonetheless, the association between DNA damage responsive miRNAs and cisplatin resistance and its underlying molecular mechanism still require further investigation. The present study has attempted to identify differentially expressed miRNAs in cisplatin induced DNA damage response in lung cancer cells, and probe into the effects of the misexpressed miRNAs on cisplatin sensitivity. Deep sequencing showed that miR-33b-3p was dramatically down-regulated in cisplatin-induced DNA damage response in A549 cells; and ectopic expression of miR-33b-3p endowed the lung cancer cells with enhanced survival and decreased γH2A.X expression level under cisplatin treatment. Consistently, silencing of miR-33b-3p in the cisplatin-resistant A549/DDP cells evidently sensitized the cells to cisplatin. Furthermore, we identified CDKN1A (p21) as a functional target of miR-33b-3p, a critical regulator of G1/S checkpoint, which potentially mediated the protection effects of miR-33b-3p against cisplatin. In aggregate, our results suggested that miR-33b-3p modulated the cisplatin sensitivity of cancer cells might probably through impairing the DNA damage response. And the knowledge of the drug resistance conferred by miR-33b-3p has great clinical implications for improving the efficacy of chemotherapies for treating lung cancers.     

Mechanism of tumor resistance to cisplatin mediated by the copper transporter ATP7B

The Wilson disease protein (ATP7B) is a copper-transporting ATPase that is responsible for regulating copper homeostasis in human tissues. ATP7B is associated with cancer resistance to cisplatin, one of the most widely used anticancer drugs. This minireview discusses the possible mechanisms of tumor resistance to cisplatin mediated by ATP7B. Cisplatin binds to the N-terminal cytosolic domain of ATP7B, which contains multiple copper-binding sites. Active platinum efflux catalyzed by ATP7B is unlikely to significantly contribute to cisplatin resistance in vivo. Transient platinum sequestration in the metal-binding domain followed by transfer to an acceptor protein or a low molecular weight compound is proposed as an alternative mechanism of cisplatin detoxification in the cell.     

NSC109268 potentiates cisplatin-induced cell death in a p53-independent manner

Background

Ovarian cancer is the leading cause of death among gynecological cancers. Cisplatin is one of the most effective anticancer drugs used in the treatment of ovarian cancer. Development of resistance to cisplatin limits its therapeutic use. Most of the anticancer drugs, including cisplatin, are believed to kill cancer cells by inducing apoptosis and a defect in apoptotic signaling can contribute to drug resistance. The tumor suppressor protein p53 plays a critical role in DNA damage-induced apoptosis. During a yeast-based drug screening, NSC109268 was identified to enhance cellular sensitivity to cisplatin. The objective of the present study is to determine if p53 is responsible for cisplatin sensitization by NSC109268.

Results

NSC109268 enhanced sensitivity of ovarian cancer 2008 cells and its cisplatin resistant counterpart 2008/C13* cells which express wild-type p53. The potentiation of cisplatin sensitivity by NSC109268 was greater in 2008/C13* cells compared to 2008 cells. Cisplatin caused a concentration-dependent increase in p53 in 2008 and 2008/C13* cells, and the induction of p53 correlated with cisplatin-induced apoptosis as determined by the cleavage of PARP. NSC109268 alone had no effect on p53 but it enhanced p53 level in response to cisplatin. Knockdown of p53 by siRNA, however, did not attenuate cell death in response to cisplatin or combination of NSC109268 and cisplatin.

Conclusions

These results demonstrate that NSC109268 enhances sensitivity of ovarian cancer 2008 cells to cisplatin independent of p53.     

Synergistic cytotoxic action of cisplatin and withaferin A on ovarian cancer cell lines

Cisplatin derivatives are used as the mainline treatment of ovarian cancer, despite their severe side effects and development of resistance. We developed a novel combination therapy by combining cisplatin with withaferin A. Treatment of ovarian cancer cell lines with combination therapy acted synergistically to induce cell death, thus required a lower dose of cisplatin to achieve the same therapeutic effect. WFA and cisplatin combination induced cell death through the generation of reactive oxygen species (ROS) for WFA, while DNA damage for cisplatin, suggesting that cisplatin binds directly to DNA to form adducts while WFA indirectly damages DNA through ROS generation. Our results for the first time suggest that combining low dose of cisplatin with suboptimal dose of WFA can serve as a potential combination therapy for the treatment of ovarian cancer with the potential to minimize/eliminate the side effects associated with high doses of cisplatin.     

DNA compaction by mononuclear platinum cancer drug cisplatin and the trisplatinum anticancer agent BBR3464: Differences and similarities

Cisplatin, a mononuclear platinum compound, which is known as a cancer drug for long time, can exhibit considerable side effects and is also not effective in many types of cancer. Therefore, the alternative platinum anticancer agents that can act at a much lower dose limit compared to the dose relevant for cisplatin treatment have been searched for. BBR3464, a trinuclear platinum compound, is found to exhibit cytotoxic effects at 10 to 1000 times lower dose limit, even in cisplatin-resistant cancer cells. The primary cellular target for cisplatin and BBR3464 is thought to be DNA. Herein, we report the nature of DNA structural changes that are induced by cisplatin and BBR3464, considering the same DNA sequence and similar sample deposition methods for comparison purpose. We have applied high-resolution atomic force microscopy (AFM) in order to obtain an idea about the molecular basis of BBR3464's effectiveness at the lower dose limit. We show from the molecularly resolved AFM images that both the compounds can compact the whole dsDNA molecules, though the degree of compaction in case of BBR3464 treatment is significantly higher. Furthermore, local compaction in terms of loop structure formation could be induced by both BBR3464 and cisplatin, though BBR3464 generated microloops and macroloops both, whereas cisplatin could generate primarily the microloops. It is a significant observation that BBR3464 could induce relatively drastic DNA structural changes in terms of loop formation as well as overall DNA compaction at a molar ratio, which is 50 times less than that applied for cisplatin treatment. Implications of such structural changes in cytotoxic effects of the platinum anticancer agents will be mentioned.     

Cell-cycle inhibition and apoptosis induced by curcumin and cisplatin or oxaliplatin in human ovarian carcinoma cells

Alteration of appropriate cell‐cycle progression and of closely related apoptotic process is a basic feature of tumour cells, and development of new tumour‐targeted agents focus on apoptosis, either during cell‐cycle arrest or following premature cell‐cycle checkpoint exit. Increasingly, epidemiological and experimental studies suggest that curcumin protects against cancer, not only because of its well‐known antioxidant properties, but also because it modulates intracellular signalling, which is related to cell proliferation and apoptosis. Cisplatin and oxaliplatin are first‐line drugs in treatment of many types of epithelial cancer and their combination with other cytostatics are under investigation to limit their side effects and resistance to them. Objectives: The aim of this study was to evaluate effects of a combined treatment using curcumin with cisplatin or with oxaliplatin, in a human ovarian cancer cell line (2008) and in its cisplatin‐resistant variant (C13). Results: Curcumin per se caused concentration‐dependent (0.1–100 µm ) and time‐persistent (24–72 h) reduction in cell proliferation, as well as altered cell cycle parameters and induced apoptosis, in both cell lines. When carcinoma cells were simultaneously exposed to curcumin and to cisplatin or oxaliplatin (at concentrations lower than IC₅₀) cell viability was reduced more than with single‐drug treatment. Moreover, dose and time related effects of curcumin, when combined with platinum drugs, were linked to consistent reduction in cell cycling and increased apoptosis, in comparison with single‐drug treatment. These effects were significant both in wild type and in cisplatin‐resistant cells, indicating that curcumin was also able to increase sensitivity of resistant ovarian cancer cells to cisplatin. Conclusions: The data suggests that curcumin is an interesting natural compound capable of limiting cell proliferation and possibly increasing clinical impact of platinum drugs, in ovarian cancer patients.     

New metal complexes as potential therapeutics

The many activities of metal ions in biology have stimulated the development of metal-based therapeutics. Cisplatin, as one of the leading metal-based drugs, is widely used in treatment of cancer, being especially effective against genitourinary tumors such as testicular. Significant side effects and drug resistance, however, have limited its clinical applications. Biological carriers conjugated to cisplatin analogs have improved specificity for tumor tissue, thereby reducing side effects and drug resistance. Platinum complexes with distinctively different DNA binding modes from that of cisplatin also exhibit promising pharmacological properties. Ruthenium and gold complexes with antitumor activity have also evolved. Other metal-based chemotherapeutic compounds have been investigated for potential medicinal applications, including superoxide dismutase mimics and metal-based NO donors/scavengers. These compounds have the potential to modulate the biological properties of superoxide anion and nitric oxide.     

Contributions of the Epidermal Growth Factor Receptor to Acquisition of Platinum Resistance in Ovarian Cancer Cells

Acquisition of platinum resistance following first line platinum/taxane therapy is commonly observed in ovarian cancer patients and prevents clinical effectiveness. There are few options to prevent platinum resistance; however, demethylating agents have been shown to resensitize patients to platinum therapy thereby demonstrating that DNA methylation is a critical contributor to the development of platinum resistance. We previously reported the Epidermal Growth Factor Receptor (EGFR) is a novel regulator of DNA methyltransferase (DNMT) activity and DNA methylation. Others have shown that EGFR activation is linked to cisplatin treatment and platinum resistance. We hypothesized that cisplatin induced activation of the EGFR mediates changes in DNA methylation associated with the development of platinum resistance. To investigate this, we evaluated EGFR signaling and DNMT activity after acute cisplatin exposure. We also developed an in vitro model of platinum resistance to examine the effects of EGFR inhibition on acquisition of cisplatin resistance. Acute cisplatin treatment activates the EGFR and downstream signaling pathways, and induces an EGFR mediated increase in DNMT activity. Cisplatin resistant cells also showed increased DNMT activity and global methylation. EGFR inhibition during repeated cisplatin treatments generated cells that were more sensitive to cisplatin and did not develop increases in DNA methylation or DNMT activity compared to controls. These findings suggest that activation of EGFR during platinum treatment contributes to the development of platinum resistance. Furthermore, EGFR inhibition may be an effective strategy at attenuating the development of platinum resistance thereby enhancing the effectiveness of chemotherapeutic treatment in ovarian cancer.     

Mechanisms of resistance to cisplatin

The use of cisplatin in cancer chemotherapy is limited by acquired or intrinsic resistance of cells to the drug. Cisplatin enters the cells and its chloride ligands are replaced by water, forming aquated species that react with nucleophilic sites in cellular macromolecules. The presence of the cisplatin adducts in DNA is thought to trigger cell cycle arrest and apoptosis. Knowledge of the mechanism of action of cisplatin has improved our understanding of resistance. Decreased intracellular concentration due to decreased drug uptake, increased reflux or increased inactivation by sulfhydryl molecules such as glutathione can cause resistance to cisplatin. Increased excision of the adducts from DNA by repair pathways or increased lesion bypass can also result in resistance. Finally, altered expression of regulatory proteins involved in signal transduction pathways that control the apoptotic pathway can also affect sensitivity to the drug. An improved understanding of the mechanisms of resistance operative in vivo has identified targets for intervention and may increase the utility of cisplatin for the treatment of cancer.     

Cisplatin resistance: Preclinical findings and clinical implications

Cisplatin is used for the treatment of many types of solid cancers. While testicular cancers respond remarkably well to cisplatin, the therapeutic efficacy of cisplatin for other solid cancers is limited because of intrinsic or acquired drug resistance. Our understanding about the mechanisms underlying cisplatin resistance has largely arisen from studies carried out with cancer cell lines in vitro. The process of cisplatin resistance appears to be multifactorial and includes changes in drug transport leading to decreased drug accumulation, increased drug detoxification, changes in DNA repair and damage bypass and/or alterations in the apoptotic cell death pathways. Translation of these preclinical findings to the clinic is emerging, but still scarce. The present review describes and discusses the clinical relevance of in vitro models by comparing the preclinical findings to data obtained in clinical studies.     

The mechanism of cisplatin-resistance in ovarian cancer

Cisplatin and its analogues have been most frequently used for treatment of human cancer including ovarian cancer. Most advanced ovarian cancer which was fatal before introduction of cisplatin have become to be treated for cure by combination chemotherapy containing cisplatin and its analogues. Thus, combination chemotherapy containing cisplatin and carboplatin have become a standard chemotherapy for treatment of ovarian cancer. Initially, platinum-based combination chemotherapy is associated with a 60-70% clinical response rate. However, the overall 5-year survival rate for advanced ovarian cancer patients is still around 20-30%. This low survival rate is due to the fact that some primary tumors and most recurrent tumors develop drug resistance that leads to treatment failure. Thus, overcoming drug resistance is the key to successful treatment of ovarian cancer. The mechanism of cisplatin-resistance in ovarian cancer is multifactorial, and accumulation of multiple genetic changes may lead to the drug-resistant phenotype. In this review, we report several genetic factors conferring cisplatin-resistance which have been elucidated in our laboratory.     

Mitochondria as a critical target of the chemotheraputic agent cisplatin in head and neck cancer

Cisplatin is among the most important chemotherapeutic agents ever developed. It is a critical component of therapeutic regimens in a broad range of malignancies. However, more than a generation after its clinical introduction, the exact mechanism of cisplatin action on tumor cells is not fully defined. The preponderance of research over the last three decades has focused on cisplatin interactions with nuclear DNA which are felt to lead to apoptotic cell death in sensitive cells. However, recent data have shown that cisplatin may have important direct interactions with mitochondria which can induce apoptosis and may account for a significant portion of the clinical activity associated with this drug. These direct interactions between cisplatin and mitochondria may have critical implications for our understanding of this class of drugs and the development of new therapeutic agents.     

Synthesis and in vitro characterization of platinum(II) anticancer coordinates using FTIR spectroscopy and NCI COMPARE: A fast method for new compound discovery

Platinum-based drugs have been used for several decades to treat various cancers successfully. Cisplatin is the original compound in this class; it cross-links DNA, resulting in cell cycle arrest and cell death via apoptosis. Cisplatin is effective against several tumor types but exhibits toxic side effects; in addition, tumors often develop resistance. An original in vitro approach is proposed to determine whether platinum-based research compounds are good candidates for further study by comparing them to marketed drugs using FTIR spectroscopy and the COMPARE analysis from the NCI. Both methods can produce fingerprints and highlight differences between the compounds, classifying the candidates and revealing promising derivatives.     

Interaction of cisplatin with planar model membranes - dose dependent change in electrical characteristics

The drug cisplatin has broad antineoplastic activity against advanced testicular and ovarian cancers, epithelial malignancies, cancers of the head, neck, bladder, oesophagus and lungs. Peripheral neurotoxicity, ototoxicity and nephrotoxicity are its major side effects. The nonspecific action of this drug on the lipid bilayer architecture of membranes has been studied by following the effects produced on the electrical characteristics of model planar bilayer lipid membranes (BLM). The results confirm that the drug has a strong surface interaction with the zwitterionic polar head groups of the amphipathic phospholipids constituting the BLM. The permeability characteristics of cisplatin through the hydrophobic core are limited. Cisplatin does not fluidise the membrane sufficiently to cause its breakdown but creates small ion conducting defects on the membrane bilayer resulting in a marginal increase in ion conductivity. These results indicate that cisplatin exhibits a non-specific action on the lipid bilayer component of the membrane which might be partly responsible for its neurotoxic side effects.