DNA damage induced by cis- and carboplatin as indicator for in vitro sensitivity of ovarian carcinoma cells

DNA damage levels in peripheral blood mononuclear cells before and after first cycle of chemotherapy have comparable prognostic values in germ cell tumor patients

Background

Germ cell tumors (GCTs) represent the most frequent solid malignancy in young men. This malignancy is highly curable by cisplatin (CDDP)-based chemotherapy. However, there is a proportion of patients having a poor prognosis due to refractory disease or its relapse. No reliable biomarkers being able to timely and accurately stratify poor prognosis GCT patients are currently available. Previously, we have shown that chemotherapy-naïve GCT patients with higher DNA damage levels in peripheral blood mononuclear cells (PBMCs) have significantly worse prognosis compared to patients with lower DNA damage levels.

Methods

DNA damage levels in PBMCs of both chemotherapy-naïve and first cycle chemotherapy-treated GCT patients have been assessed by standard alkaline comet assay and its styrene oxide (SO)-modified version. These levels were correlated with clinico-pathological characteristics.

Results

We re-confirm prognostic value of DNA damage level in chemotherapy-naïve GCT patients and reveal that this prognosticator is equally effective in GCT patients after first cycle of CDDP-based chemotherapy. Furthermore, we demonstrate that SO-modified comet assay is comparably sensitive as standard alkaline comet assay in case of patients who underwent first cycle of CDDP-based chemotherapy, although it appears more suitable to detect DNA cross-links.

Conclusion

We propose that DNA damage levels in PBMCs before and after first cycle of CCDP-based chemotherapy are comparable independent prognosticators for progression-free and overall survivals in GCT patients. Therefore, their clinical use is highly advised to stratify GCT patients to identify those who are most at risk of developing disease recurrence or relapse, allowing tailoring therapeutic interventions to poor prognosis individuals, and optimizing their care management and treatment regimen.

Adult Laryngeal Pleomorphic Rhabdomyosarcoma: A Rare Entity

Rhabdomyosarcoma (RMS) is a rare and aggressive cancerous tumor that arises from embryonal mesenchymal cells with skeletal muscle differentiation, and it is exceedingly rare that occurs specifically in the larynx. To date, only 22 instances of laryngeal pleomorphic RMSs have been documented in adults. Consequently, there is limited information available to assist healthcare professionals in effectively handling RMS in the larynx of adult patients. Here, we present an uncommon occurrence involving a 45-year-old man who experienced progressive hoarseness and received a diagnosis of pleomorphic RMS affecting the larynx. Pleomorphic RMS had been pathologically diagnosed after a vertical hemilaryngectomy. Following the surgical intervention, the patient underwent chemotherapy and radiation therapy. As of now, there have been no indications of tumor recurrence.

Dysfunctional activity of classical DNA end-joining renders acquired resistance to carboplatin in human ovarian cancer cells

Ovarian cancer is the deadliest gynecological malignancy worldwide. Although chemotherapy is required as the most standard treatment strategy for ovarian cancer, the survival rates are very low, largely because of high incidence of recurrence due to resistance to conventional surgery and genotoxic chemotherapies. Carboplatin-resistant ovarian cancer cells were generated by continuous treatment over six months. Carboplatin-resistance induced morphological alterations and promoted the rates of proliferation and migration of SKOV3 compared to the parental cells. Interestingly, carboplatin-resistant SKOV3 showed the high levels of γH2AX foci formed at the basal level, and the levels of γH2AX foci remained even after the recovery time, suggesting that the DNA damage response and repair machinery were severely attenuated by carboplatin-resistance. Surprisingly, the expression levels of XRCC4, a critical factor in non-homologous end joining (NHEJ) DNA repair, were significantly decreased in carboplatin-resistant SKOV3 compared with those in non-resistant controls. Furthermore, restoration of NHEJ in carboplatin-resistant SKOV3 by suppression of ABCB1 and/or AR re-sensitized carboplatin-resistant cells to genotoxic stress and reduced their proliferation ability. Our findings suggest that attenuation of the NHEJ DNA repair machinery mediated by resistance to genotoxic stress might be a critical cause of chemoresistance in patients with ovarian cancer.

The Affinity of Carboplatin to B-Vitamins and Nucleobases

Platinum compounds have found wide application in the treatment of various types of cancer and carboplatin is one of the main platinum-based drugs used as antitumor agents. The anticancer activity of carboplatin arises from interacting with DNA and inducing programmed cell death. However, such interactions may occur with other chemical compounds, such as vitamins containing aromatic rings with lone-pair orbitals, which reduces the anti-cancer effect of carboplatin. The most important aspect of the conducted research was related to the evaluation of carboplatin affinity to vitamins from the B group and the potential impact of such interactions on the reduction of therapeutic capabilities of carboplatin in anticancer therapy. Realized computations, including estimation of Gibbs Free Energies, allowed for the identification of the most reactive molecule, namely vitamin B6 (pyridoxal phosphate). In this case, the computational estimations indicating carboplatin reactivity were confirmed by spectrophotometric measurements.

Investigating the effects of bark extract and volatile oil of Pinus eldarica against cisplatin-induced genotoxicity on HUVECs cell line

Cisplatin is used for treating multiple types of cancers. Alongside its therapeutic effects, there are side effects, including cytotoxicity and genotoxicity for healthy cells, which are mainly related to radical oxygen species (ROS) production by the drug. These side effects could troublesome the treatment process. Previous studies have suggested that members of Pinaceae family are rich sources of antioxidant components. This article investigates the antioxidant activity (AA) of Pinus eldarica (Pinaceae) along with its cyto/genoprotective effects following cisplatin exposure on human umbilical vein endothelial cells (HUVECs) cell line. Pinus eldarica's hydroalcoholic bark extract (PEHABE) and P. eldarica's needle volatile oil (PENVO) were prepared using maceration and hydrodistillation methods, respectively. PENVO was analysed via gas chromatograph-mass spectrometry, and the total phenolic content of PEHBAE was measured by folin-ciocalteu reagent. AA of both PEHABE and PENVO were determined using DPPH assay. Moreover, MTT test was used to determine the cytoprotective effects of both agents. Comet and micronucleus (MN) tests were also performed to investigate the genoprotective effect of P. eldarica. Germacrene D (35.72%) was the main component of PENVO. PEHABE showed higher AA compared with PENVO, with the highest AA observed at 25 and 250 μg/ml, respectively. Both PENVO and PEHABE were cytoprotective, with the latter having mitogenic effects on cells at 75, 100, and 200 μg/ml concentrations (P < 0.01 and P < 0.001). Also, both PEHABE and PENVO showed genoprotective effects against cisplatin in comet assay (P < 0.001). As PEHABE's concentrations were increased, a reduced number of MN formation was observed after cisplatin's exposure (P < 0.001). In conclusion, PEHABE had higher AA compared with PENVO, and both agents had cyto/genoprotective effects on HUVECs.

Adult laryngeal Embryonal Rhabdomyosarcoma: a case report and literature review

Background

Laryngeal rhabdomyosarcomas (RMSs) mainly occurred in children, while were extremely rare in adults. Consequently, less information was available to guide clinicians to manage adult RMSs in larynx.

Case presentation

A 42-year-old man presented with a 2-year history of gradually worsening hoarseness. Then, he underwent a surgery with suspension laryngoscope with initially being diagnosed as vocal cord cyst. Unexpectedly, the lesion was proved to be embryonal rhabdomyosarcoma (ERMS), pathologically. Next, he underwent chemoradiotherapy, while the tumor relapsed 18 months after the last treatment. Subsequently, a vertical hemilaryngectomy and a right selective neck dissection was performed, and the chemotherapy according to the anticancer drug sensitivity in vitro was arranged. Until the last check-up 18 months after chemotherapy, the patient did not display clinical or radiological signs of local recurrence and metastases.

Conclusions

Misdiagnosis and missed diagnosis of laryngeal RMSs might appear when tumors presented as smooth protuberance. We reported the first case of laryngeal RMSs in an adult with the multidisciplinary strategy based on the chemosensitivity assay in vitro. Furthermore, a systematic review of the literature was also discussed, highlighting the initial diagnostic pitfalls and subsequent management problems that may occur with this uncommon tumor.

Genome-wide single-nucleotide resolution of oxaliplatin-DNA adduct repair in drug-sensitive and -resistant colorectal cancer cell lines

Platinum-based chemotherapies, including oxaliplatin, are a mainstay in the management of solid tumors and induce cell death by forming intrastrand dinucleotide DNA adducts. Despite their common use, they are highly toxic, and approximately half of cancer patients have tumors that are either intrinsically resistant or develop resistance. Previous studies suggest that this resistance is mediated by variations in DNA repair levels or net drug influx. Here, we aimed to better define the roles of nucleotide excision repair and DNA damage in platinum chemotherapy resistance by profiling DNA damage and repair efficiency in seven oxaliplatin-sensitive and three oxaliplatin-resistant colorectal cancer cell lines. We assayed DNA repair indirectly as toxicity and directly measured bulky adduct formation and removal from the genome by slot blot and repair capacity in an excision assay, and used excision repair sequencing (XR-seq) to map repair events genome-wide at single-nucleotide resolution. Using this combinatorial approach and proxies for oxaliplatin-DNA damage, we observed no significant differences in repair efficiency that could explain the relative sensitivities and chemotherapy resistances of these cell lines. In contrast, the levels of oxaliplatin-induced DNA damage were significantly lower in the resistant cells, indicating that decreased damage formation, rather than increased damage repair, is a major determinant of oxaliplatin resistance in these cell lines. XR-seq-based analysis of gene expression revealed up-regulation of membrane transport pathways in the resistant cells, and these pathways may contribute to resistance. In conclusion, additional research is needed to characterize the factors mitigating cellular DNA damage formation by platinum compounds.

Circulating non‑coding RNA‑biomarker potential in neoadjuvant chemotherapy of triple negative breast cancer?

Due to the positive association between neoadjuvant chemotherapy (NACT) and the promising early response rates of patients with triple negative breast cancer (TNBC), including probabilities of pathological complete response, NACT is increasingly used in TNBC management. Liquid biopsy-based biomarkers with the power to diagnose the early response to NACT may support established monitoring tools, which are to a certain extent imprecise and costly. Simple serum- or urine-based analyses of non-coding RNA (ncRNA) expression may allow for fast, minimally-invasive testing and timely adjustment of the therapy regimen. The present study investigated breast cancer-related ncRNAs [microRNA (miR)-7, -9, -15a, -17, -18a, -19b, -21, -30b, -222 and -320c, PIWI-interacting RNA-36743 and GlyCCC2] in triple positive BT-474 cells and three TNBC cell lines (BT-20, HS-578T and MDA-MB-231) treated with various chemotherapeutic agents using reverse transcription-quantitative PCR. Intracellular and secreted microvesicular ncRNA expression levels were analysed using a multivariable statistical regression analysis. Chemotherapy-driven effects were investigated by analysing cell cycle determinants at the mRNA and protein levels. Serum and urine specimens from 8 patients with TNBC were compared with 10 healthy females using two-sample t-tests. Samples from the patients with TNBC were compared at two time points. Chemotherapeutic treatments induced distinct changes in ncRNA expression in TNBC cell lines and the BT-474 cell line in intra- and extracellular compartments. Serum and urine-based ncRNA expression analysis was able to discriminate between patients with TNBC and controls. Time point comparisons in the urine samples of patients with TNBC revealed a general rise in the level of ncRNA. Serum data suggested a potential association between piR-36743, miR-17, -19b and -30b expression levels and an NACT-driven complete clinical response. The present study highlighted the potential of ncRNAs as liquid biopsy-based biomarkers in TNBC chemotherapy treatment. The ncRNAs tested in the present study have been previously investigated for their involvement in BC or TNBC chemotherapy responses; however, these previous studies were restricted to patient tissue or in vitro models. The data from the present study offer novel insight into ncRNA expression in liquid samples from patients with TNBC, and the study serves as an initial step in the evaluation of ncRNAs as diagnostic biomarkers in the monitoring of TNBC therapy.

Genotoxic Effects of Tributyltin and Triphenyltin Isothiocyanates, Cognate RXR Ligands: Comparison in Human Breast Carcinoma MCF 7 and MDA-MB-231 Cells

The cytotoxicity of two recently synthesized triorganotin isothiocyanate derivatives, nuclear retinoid X receptor ligands, was tested and compared in estrogen-receptor-positive MCF 7 and -negative MDA-MB-231 human breast carcinoma cell lines. A 48 h MTT assay indicated that tributyltin isothiocyanate (TBT-ITC) is more cytotoxic than triphenyltin isothiocyanate (TPT-ITC) in MCF 7 cells, and the same trend was observed in the MDA-MB-231 cell line. A comet assay revealed the presence of both crosslinks and increasing DNA damage levels after the 17 h treatment with both derivatives. Differences in cytotoxicity of TBT-ITC and TPT-ITC detected by FDA staining correspond to the MTT data, communicating more pronounced effects in MCF 7 than in the MDA-MB-231 cell line. Both derivatives were found to cause apoptosis, as shown by the mitochondrial membrane potential (MMP) depolarization and caspase-3/7 activation. The onset of caspase activation correlated with MMP dissipation and the total cytotoxicity more than with the amount of active caspases. In conclusion, our data suggest that the DNA damage induced by TBT-ITC and TPT-ITC treatment could underlie their cytotoxicity in the cell lines studied.

Evaluation for Synergistic Effects by Combinations of Photodynamic Therapy (PDT) with Temoporfin (mTHPC) and Pt(II) Complexes Carboplatin, Cisplatin or Oxaliplatin in a Set of Five Human Cancer Cell Lines

The platinum(II) complexes carboplatin (CBDCA), cisplatin (CDDP) and oxaliplatin (1-OHP) are used as anticancer drugs in a large number of tumour chemotherapy regimens. Many attempts have been made to combine Pt(II)-based chemotherapy with alternative treatment strategies. One such alternative anticancer approach is known as photodynamic therapy (PDT), where a non-toxic photosensitizer (PS) produces oxidative stress via the formation of reactive oxygen species (ROS) after local illumination of the affected tissue. A very promising PS is 5,10,15,20-tetra(m-hydroxyphenyl)chlorin (mTHPC, Temoporfin), which is approved for the treatment of head and neck cancer in Europe. In the present study, a combination of mTHPC-mediated PDT and either CBDCA, CDDP, or 1-OHP was applied to five human cancer cell lines from different tumour origins. Cytotoxicity was determined by the MTT assay and synergistic effects on cytotoxicity were evaluated by calculation of Combination Indices (CI). Synergy was identified in some of the combinations, for example, with 1-OHP in three of the tested cell lines but antagonism was also observed for a number of combinations in certain cell lines. In cases of synergy, elevated ROS levels were observed after combination but apoptosis induction was not necessarily increased compared to a treatment with a single compound. Cell cycle analysis revealed a formation of apoptotic subG1 populations and S phase as well as G2/M phase arrests after combination. In conclusion, pre-treatment with mTHPC-PDT has the potential to sensitize some types of tumour cells towards Pt(II) complexes, in particular 1-OHP but synergy is highly dependent on the type of cancer.

Carboplatin-induced hematotoxicity among patients with non-small cell lung cancer: Analysis on clinical adverse events and drug-gene interactions

In order to clarify the risk of hematotoxicity of carboplatin, we inspected 19901 case reports of non-small cell lung cancer patients that were submitted to the FDA Adverse Event Reporting System (FAERS) between January 2004 and December 2015. These comprised 3907 cases which were treated with carboplatin and 15994 cases which were treated with other therapies in the absence of carboplatin. By comparison, carboplatin cases were significantly more likely to report anemia (OR = 2.27, 95% CI 1.85-2.78, P = 5.04×10⁻¹⁵), neutropenia (OR = 2.27, 95% CI 1.76-2.92, P = 2.39×10⁻¹⁰), and thrombocytopenia (OR = 2.38, 95% CI 1.84-3.08, P = 5.60×10⁻¹¹). We further explored published evidences and found 205 human genes interacting with carboplatin. Functional analysis corroborated that these genes were significantly enriched in the biochemical pathway of hematopoietic cell lineage (adjusted P = 6.02×10⁻¹¹). This indicated that carboplatin could profoundly affect the development of blood cells. Given the early awareness of the hematologic risks, great caution should be exercised in prescribing carboplatin to non-small cell lung cancer patients. And functional enrichment analysis on carboplatin-related genes warranted subsequent research with regard to the underlying toxicological mechanisms.

A diagnostic microdosing approach to investigate platinum sensitivity in non-small cell lung cancer

The platinum-based drugs cisplatin, carboplatin and oxaliplatin are often used for chemotherapy, but drug resistance is common. The prediction of resistance to these drugs via genomics is a challenging problem since hundreds of genes are involved. A possible alternative is to use mass spectrometry to determine the propensity for cells to form drug-DNA adducts-the pharmacodynamic drug-target complex for this class of drugs. The feasibility of predictive diagnostic microdosing was assessed in non-small cell lung cancer (NSCLC) cell culture and a pilot clinical trial. Accelerator mass spectrometry (AMS) was used to quantify [14 C]carboplatin-DNA monoadduct levels in the cell lines induced by microdoses and therapeutic doses of carboplatin, followed by correlation with carboplatin IC50 values for each cell line. The adduct levels in cell culture experiments were linearly proportional to dose (R2  = 0.95, p < 0.0001) and correlated with IC50 across all cell lines for microdose and therapeutically relevant carboplatin concentrations (p = 0.02 and p = 0.01, respectively). A pilot microdosing clinical trial was conducted to define protocols and gather preliminary data. Plasma pharmacokinetics (PK) and [14 C]carboplatin-DNA adducts in white blood cells and tumor tissues from six NSCLC patients were quantified via AMS. The blood plasma half-life of [14 C]carboplatin administered as a microdose was consistent with the known PK of therapeutic dosing. The optimal [14 C]carboplatin formulation for the microdose was 107 dpm/kg of body weight and 1% of the therapeutic dose for the total mass of carboplatin. No microdose-associated toxicity was observed in the patients. Additional accruals are required to significantly correlate adduct levels with response.

DNA Adducts from Anticancer Drugs as Candidate Predictive Markers for Precision Medicine

Biomarker-driven drug selection plays a central role in cancer drug discovery and development, and in diagnostic strategies to improve the use of traditional chemotherapeutic drugs. DNA-modifying anticancer drugs are still used as first line medication, but drawbacks such as resistance and side effects remain an issue. Monitoring the formation and level of DNA modifications induced by anticancer drugs is a potential strategy for stratifying patients and predicting drug efficacy. In this perspective, preclinical and clinical data concerning the relationship between drug-induced DNA adducts and biological response for platinum drugs and combination therapies, nitrogen mustards and half-mustards, hypoxia-activated drugs, reductase-activated drugs, and minor groove binding agents are presented and discussed. Aspects including measurement strategies, identification of adducts, and biological factors that influence the predictive relationship between DNA modification and biological response are addressed. A positive correlation between DNA adduct levels and response was observed for the majority of the studies, demonstrating the high potential of using DNA adducts from anticancer drugs as mechanism-based biomarkers of susceptibility, especially as bioanalysis approaches with higher sensitivity and throughput emerge.

Platinum anti-cancer drugs: Free radical mechanism of Pt-DNA adduct formation and anti-neoplastic effect

The literature on the anti-neoplastic effects of Pt drugs provides substantial evidence that free radical may be involved in the formation of Pt-DNA adducts and other cytotoxic effects. The conditions specific to cancerous tumours are more conducive to free radical mechanisms than the commonly accepted hydrolysis nucleophilic-electrophilic mechanism of Pt-DNA adduct formation. Molecular orbital studies of the adiabatic attachment of hydrated electrons to Pt drugs reveal that there is a significant lengthening of the Pt-X bond (where X is Cl, O in cisplatin, carboplatin and some pyrophosphate-Pt drugs but not oxaliplatin) in the anion radical species. This observation is consistent with a dissociative electron transfer (DET) mechanism for the formation of Pt-DNA adducts. A DET reaction mechanism is proposed for the reaction of Pt drugs with guanine which involves a quasi-inner sphere 2 electron transfer process involving a transient intermediate 5 co-ordinated activated anion radical species {R2Pt---Cl(G)(Cl)•}*(-) (where R is an ammine group, and G is guanine) and the complex has an elongated Pt---Cl (or Pt---O) bond. A DET mechanism is also proposed when Pt drugs are activated by reaction with free radicals such as HO•, CO3•(-), O2•(-) but do not react with DNA bases to form adducts, but form Pt-protein adducts with proteins such ezrin, FAS, DR5, TNFR1 etc. The DET mechanism may not occur with oxaliplatin.

Human mesenchymal stem cells are resistant to cytotoxic and genotoxic effects of cisplatin in vitro

Mesenchymal stem cells (MSCs) are known for their important properties involving multilineage differentiation potential., trophic factor secretion and localization along various organs and tissues. On the dark side, MSCs play a distinguished role in tumor microenvironments by differentiating into tumor-associated fibroblasts or supporting tumor growth via distinct mechanisms. Cisplatin (CIS) is a drug widely applied in the treatment of a large number of cancers and is known for its cytotoxic and genotoxic effects, both in vitro and in vivo. Here we assessed the effects of CIS on MSCs and the ovarian cancer cell line OVCAR-3, by MTT and comet assays. Our results demonstrated the resistance of MSCs to cell death and DNA damage induction by CIS, which was not observed when OVCAR-3 cells were exposed to this drug.

HNF1β drives glutathione (GSH) synthesis underlying intrinsic carboplatin resistance of ovarian clear cell carcinoma (OCCC)

Chemoresistance to platinum-based antineoplastic agents is a consistent feature among ovarian carcinomas; however, whereas high-grade serous carcinoma (OSC) acquires resistance during chemotherapy, ovarian clear cell carcinoma (OCCC) is intrinsically resistant. The main objective of this study was to explore, in vitro and in vivo, if hepatocyte nuclear factor 1β (HNF1β) and glutaminolysis contribute for the resistance of OCCC to carboplatin through the intrinsically increased GSH bioavailability. To disclose the role of HNF1β, experiments were also performed in an OSC cell line, which does not express HNF1β. Metabolic profiles, GSH quantification, HNF1β, and γ-glutamylcysteine ligase catalytic subunit (GCLC) and modifier subunit (GCLM) expression, cell cycle, and death were assessed in ES2 cell line (OCCC) and OVCAR3 cell line (OSC); HNF1β knockdown was performed in ES2 and murine model of subcutaneous and peritoneal OCCC tumors was established to test buthionine sulphoxamine (BSO), as a sensitizer to carboplatin. Glutaminolysis is activated in ES2 and OVCAR3, though ES2 exclusively synthesizes amino acids and GSH. ES2 cells are more resistant to carboplatin than OVCAR3 and the abrogation of GSH production by BSO sensitizes ES2 to carboplatin. HNF1β regulates the expression of GCLC, but not GCLM, and consequently GSH production in ES2. In vivo, BSO prior to carboplatin reduces dramatically subcutaneous tumor size and GSH levels, as well as peritoneal dissemination. Our study discloses HNF1β as the mediator of intrinsic OCCC chemoresistance and sheds a light to re-explore a cancer adjuvant therapeutic approach using BSO to overcome the lack of efficient therapy in OCCC.

Phase I Trial of Carboplatin and Gemcitabine Chemotherapy and Stereotactic Ablative Radiosurgery for the Palliative Treatment of Persistent or Recurrent Gynecologic Cancer

Background

We conducted a phase I trial to determine the safety of systemic chemotherapy prior to abdominopelvic robotic stereotactic ablative radiotherapy (SABR) in women with persistent or recurrent gynecologic cancers.

Methods

Patients were assigned to dose-finding cohorts of day 1 carboplatin (AUC 2 or 4) and gemcitabine (600 or 800 mg/m²) followed by day 2 to day 4 Cyberknife SABR (8 Gy × three consecutive daily doses). Toxicities were graded prospectively by common terminology criteria for adverse events, version 4.0. SABR target and best overall treatment responses were recorded according to response evaluation criteria in solid tumors, version 1.1.

Findings

The maximum tolerated dose of chemotherapy preceding SABR was carboplatin AUC 4 and gemcitabine 600 mg/m². One patient experienced manageable, dose-limiting grade 4 neutropenia, grade 4 hypokalemia, and grade 3 nausea attributed to study treatment. One patient had a late grade 3 rectovaginal fistula 16 months after trial therapy. Among 28 SABR targets, 22 (79%) showed a partial response and 6 (21%) remained stable.

Interpretation

Systemic chemotherapy may be given safely prior to abdominopelvic robotic SABR with further investigation warranted.

Aberrant DNA damage response pathways may predict the outcome of platinum chemotherapy in ovarian cancer

Ovarian carcinoma (OC) is the most lethal gynecological malignancy. Despite the advances in the treatment of OC with combinatorial regimens, including surgery and platinum-based chemotherapy, patients generally exhibit poor prognosis due to high chemotherapy resistance. Herein, we tested the hypothesis that DNA damage response (DDR) pathways are involved in resistance of OC patients to platinum chemotherapy. Selected DDR signals were evaluated in two human ovarian carcinoma cell lines, one sensitive (A2780) and one resistant (A2780/C30) to platinum treatment as well as in peripheral blood mononuclear cells (PBMCs) from OC patients, sensitive (n = 7) or resistant (n = 4) to subsequent chemotherapy. PBMCs from healthy volunteers (n = 9) were studied in parallel. DNA damage was evaluated by immunofluorescence γH2AX staining and comet assay. Higher levels of intrinsic DNA damage were found in A2780 than in A2780/C30 cells. Moreover, the intrinsic DNA damage levels were significantly higher in OC patients relative to healthy volunteers, as well as in platinum-sensitive patients relative to platinum-resistant ones (all P<0.05). Following carboplatin treatment, A2780 cells showed lower DNA repair efficiency than A2780/C30 cells. Also, following carboplatin treatment of PBMCs ex vivo, the DNA repair efficiency was significantly higher in healthy volunteers than in platinum-resistant patients and lowest in platinum-sensitive ones (t_1/2 for loss of γH2AX foci: 2.7±0.5h, 8.8±1.9h and 15.4±3.2h, respectively; using comet assay, t_1/2 of platinum-induced damage repair: 4.8±1.4h, 12.9±1.9h and 21.4±2.6h, respectively; all P<0.03). Additionally, the carboplatin-induced apoptosis rate was higher in A2780 than in A2780/C30 cells. In PBMCs, apoptosis rates were inversely correlated with DNA repair efficiencies of these cells, being significantly higher in platinum-sensitive than in platinum-resistant patients and lowest in healthy volunteers (all P<0.05). We conclude that perturbations of DNA repair pathways as measured in PBMCs from OC patients correlate with the drug sensitivity of these cells and reflect the individualized response to platinum-based chemotherapy.

Gallium phosphinoarylbisthiolato complexes counteract drug resistance of cancer cells

In cancer therapy the platinum-based drugs are used frequently with a good clinical outcome, but besides unwanted side effects which occur, the tumour cells subjected to treatment are prone to develop tolerance or even multidrug resistance (MDR). Metal compounds with a central atom other than platinum are efficient in targeting the chemoresistant cells, therefore the biological outcome of two recently synthesized gallium phosphinoarylbisthiolato complexes was studied, having the formula [X][Ga{PPh(2-SC6H4)2-κ(3)S,S',P}{PPh(2-SC6H4)2-κ(2)S,S'}] where [X] is either the NEt3H (1) or PPh4 (2) cation. Compounds 1 and 2 display in vitro cytotoxicity against both platinum-sensitive and platinum-resistant cell lines (A2780 and A2780cis). Morphological and ultrastructural evidence points toward their capacity to impair tumour cells survival. This behaviour is based on malignant cells capacity to selectively intake gallium, and to bind to the cellular DNA. They are able to cause massive DNA damage in treated cancer cells, focusing on 7-methylguanine and 8-oxoguanine sites and oxidizing the pyrimidine bases; this leads to early apoptosis of a significant percent of treated cells. The intrinsic and extrinsic apoptotic pathways are influenced through the modulation of gene expression following the treatment with complexes 1 and 2, which accompanies the negative regulation of P-glycoprotein 1 (Pgp-1), an important cellular ABC-type transporter from the multidrug resistance (MDR) family. The studied Ga(III) compounds demonstrated the capacity to counteract the chemoresistance mechanisms in the tumours defiant to standard drug action. Compound 2 shows a good anticancer potential and it could represent an alternative to platinum-based drugs especially in the situation of standard treatment failure.

Prediction of individual response to anticancer therapy: historical and future perspectives

Since the introduction of chemotherapy for cancer treatment in the early 20th century considerable efforts have been made to maximize drug efficiency and at the same time minimize side effects. As there is a great interpatient variability in response to chemotherapy, the development of predictive biomarkers is an ambitious aim for the rapidly growing research area of personalized molecular medicine. The individual prediction of response will improve treatment and thus increase survival and life quality of patients. In the past, cell cultures were used as in vitro models to predict in vivo response to chemotherapy. Several in vitro chemosensitivity assays served as tools to measure miscellaneous endpoints such as DNA damage, apoptosis and cytotoxicity or growth inhibition. Twenty years ago, the development of high-throughput technologies, e.g. cDNA microarrays enabled a more detailed analysis of drug responses. Thousands of genes were screened and expression levels were correlated to drug responses. In addition, mutation analysis became more and more important for the prediction of therapeutic success. Today, as research enters the area of -omics technologies, identification of signaling pathways is a tool to understand molecular mechanism underlying drug resistance. Combining new tissue models, e.g. 3D organoid cultures with modern technologies for biomarker discovery will offer new opportunities to identify new drug targets and in parallel predict individual responses to anticancer therapy. In this review, we present different currently used chemosensitivity assays including 2D and 3D cell culture models and several -omics approaches for the discovery of predictive biomarkers. Furthermore, we discuss the potential of these assays and biomarkers to predict the clinical outcome of individual patients and future perspectives.

DNA crosslinks, DNA damage and repair in peripheral blood lymphocytes of non-small cell lung cancer patients treated with platinum derivatives

Lung cancer is the leading cause of cancer-related mortality in the world. Chemotherapy has been the mainstay of treatment for advanced non-small cell lung cancer (NSCLC) and platinum-based derivatives have been shown to improve overall survival. The aim of the present study was to investigate the DNA damage [single strand breaks (SSBs) and DNA crosslinks] and DNA repair in peripheral blood lymphocytes in patients with NSCLC treated with platinum derivatives using modified comet assay. Twenty patients in the final (4th) stage of NSCLC and 10 age-corresponding healthy controls participated in the study. Alkaline comet assay was performed according to the appropriate protocol. The DNA base excision repair (BER) activity of the controls was significantly higher compared to that of cancer patients, and the activity of DNA nucleotide excision repair (NER) was almost at the same level both in controls and patients. We observed changes in the amount of SSBs and DNA crosslinks during the course of chemotherapy. We found a significantly higher level of SSBs immediately after administration of chemotherapy. Similarly, we found the highest incidence of DNA crosslinks immediately or 1 day after chemotherapy (compared to measurement before chemotherapy). Moreover, we compared the levels of DNA repair in patients who survived chemotherapy with those in patients who died in the course of chemotherapy: the activity of BER was higher in the case of surviving patients, while the levels of NER were essentially the same. The data arising from the present study confirm the findings of other studies dealing with DNA damage and repair in cancer patients treated with chemotherapy. Moreover, our results indicated that despite the fact that cisplatin-DNA adducts are removed by the NER pathway, BER may also play a role in the clinical status of patients and their survival.

Oxaliplatin induces different cellular and molecular chemoresistance patterns in colorectal cancer cell lines of identical origins

Background

Cancer cells frequently adopt cellular and molecular alterations and acquire resistance to cytostatic drugs. Chemotherapy with oxaliplatin is among the leading treatments for colorectal cancer with a response rate of 50%, inducing intrastrand cross-links on the DNA. Despite of this drug’s efficiency, resistance develops in nearly all metastatic patients. Chemoresistance being of crucial importance for the drug’s clinical efficiency this study aimed to contribute to the identification and description of some cellular and molecular alterations induced by prolonged oxaliplatin therapy. Resistance to oxaliplatin was induced in Colo320 (Colo320R) and HT-29 (HT-29R) colorectal adenocarcinoma cell lines by exposing the cells to increasing concentrations of the drug. Alterations in morphology, cytotoxicity, DNA cross-links formation and gene expression profiles were assessed in the parental and resistant variants with microscopy, MTT, alkaline comet and pangenomic microarray assays, respectively.

Results

Morphology analysis revealed epithelial-to-mesenchymal transition in the resistant vs parental cells suggesting alterations of the cells’ adhesion complexes, through which they acquire increased invasiveness and adherence. Cytotoxicity measurements demonstrated resistance to oxaliplatin in both cell lines; Colo320 being more sensitive than HT-29 to this drug (P < 0.001). The treatment with oxaliplatin caused major DNA cross-links in both parental cell lines; in Colo320R small amounts of DNA cross-links were still detectable, while in HT-29R not. We identified 441 differentially expressed genes in Colo320R and 613 in HT-29R as compared to their parental counterparts (at least 1.5 -fold up- or down- regulation, p < 0.05). More disrupted functions and pathways were detected in HT-29R cell line than in Colo320R, involving genes responsible for apoptosis inhibition, cellular proliferation and epithelial-to-mesenchymal transition. Several upstream regulators were detected as activated in HT-29R cell line, but not in Colo320R.

Conclusions

Our findings revealed a more resistant phenotype in HT-29R as compared to Colo320R and different cellular and molecular chemoresistance patterns induced by prolonged treatment with oxaliplatin in cell lines with identical origins (colorectal adenocarcinomas).

The hepatoprotective potential of Spirulina and vitamin C supplemention in cisplatin toxicity

Spirulina platensis is a microalgae with potent dietary phyto-antioxidant, anti-inflammatory and anti-carcinogenic properties. We investigated the mechanism of cisplatin induced hepatotoxicity and whether this natural antioxidant provided protection against cisplatin hepatotoxicity. The study was carried out in a mice model where the animals were segregated into different groups according to their treatments, e.g. control group with no treatment, cisplatin treated, cisplatin + Spirulina treated, cisplatin + vitamin C treated and cisplatin + Spirulina + vitamin C treated. The liver marker enzymes were found to be elevated following cisplatin treatment, signifying hepatotoxicity. The supplementation of Spirulina and vitamin C could effectively bring down the levels of these enzymes. Light microscopy also showed that cisplatin treatment induced liver injury and that histopathological abnormalities were prevented by Spirulina and vitamin C supplementation. This protective effect was further substantiated by the estimation of antioxidant levels and extent of lipid peroxidation in the Spirulina, vitamin C and Spirulina + vitamin C supplemented groups as compared to cisplatin alone.

Enhanced sensitivity to cisplatin and gemcitabine in Brca1-deficient murine mammary epithelial cells

Background

Breast cancers due to germline mutations or altered expression of the BRCA1 gene associate with an aggressive clinical course and frequently exhibit a "triple-negative" phenotype, i.e. lack of expression of the estrogen and progesterone hormone receptors and lack of overexpression of the HER2/NEU oncogene, thereby rendering them relatively insensitive to hormonal manipulation and targeted HER2 therapy, respectively. BRCA1 plays a role in multiple DNA repair pathways, and thus, when mutated, results in sensitivity to certain DNA damaging drugs.

Results

Here, we used a Brca1 murine mammary epithelial cell (MMEC) model to examine the effect of loss of Brca1 on cellular sensitivity to various chemotherapy drugs. To explore novel therapeutic strategies, we included DNA damaging and non-DNA damaging drugs whose mechanisms are dependent and independent of DNA repair, respectively, and drugs that are used in standard and non-standard lines of therapy for breast cancer. To understand the cellular mechanism, we also determined the role that DNA repair plays in sensitivity to these drugs. We found that cisplatin and gemcitabine had the greatest specific therapeutic benefit to Brca1-deficient MMECs, and that when used in combination produced a synergistic effect. This sensitivity may be attributed in part to defective NER, which is one of the DNA repair pathways normally responsible for repairing DNA adducts produced by cisplatin and is shown in this study to be defective in Brca1-deficient MMECs. Brca1-deficient MMECs were not differentially sensitive to the standard breast cancer chemotherapy drugs doxorubicin, docetaxel or 5-FU.

Conclusions

Both cisplatin and gemcitabine should be explored in clinical trials for first line regimens for BRCA1-associated and triple-negative breast cancer.

Genotoxicity of platinum in embryos of zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis)

The metal platinum is inter alia used for industrial and medical purposes. Due to its application in automobile catalytic converters and as an anti-cancer drug, Pt enters the aquatic environment via road runoff and hospital sewage and raises concerns about its environmental impact and toxicity to organisms. Therefore, the genotoxicity of Pt at 0, 0.1, 1, 10, 50, 100 and 200μg/l PtCl(2) was tested on two freshwater organisms, zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis) using the single cell gel electrophoresis, also called comet assay. PtCl(2) did not show any genotoxicity for D. rerio at the tested concentrations, whereas significantly elevated DNA damage was observed in M. cornuarietis at 1μg/l PtCl(2) and beyond. The results of the study suggest a high sensitivity of M. cornuarietis concerning the genotoxic impact of PtCl(2).

A microdosing approach for characterizing formation and repair of carboplatin-DNA monoadducts and chemoresistance

Formation and repair of platinum (Pt)-induced DNA adducts is a critical step in Pt drug-mediated cytotoxicity. Measurement of Pt-DNA adduct kinetics in tumors may be useful for better understanding chemoresistance and therapeutic response. However, this concept has yet to be rigorously tested because of technical challenges in measuring the adducts at low concentrations and consistent access to sufficient tumor biopsy material. Ultrasensitive accelerator mass spectrometry was used to detect [(14)C]carboplatin-DNA monoadducts at the attomole level, which are the precursors to Pt-DNA crosslink formation, in six cancer cell lines as a proof-of-concept. The most resistant cells had the lowest monoadduct levels at all time points over 24 hr. [(14)C]Carboplatin "microdoses" (1/100th the pharmacologically effective concentration) had nearly identical adduct formation and repair kinetics compared to therapeutically relevant doses, suggesting that the microdosing approach can potentially be used to determine the pharmacological effects of therapeutic treatment. Some of the possible chemoresistance mechanisms were also studied, such as drug uptake/efflux, intracellular inactivation and DNA repair in selected cell lines. Intracellular inactivation and efficient DNA repair each contributed significantly to the suppression of DNA monoadduct formation in the most resistant cell line compared to the most sensitive cell line studied (p < 0.001). Nucleotide excision repair (NER)-deficient and -proficient cells showed substantial differences in carboplatin monoadduct concentrations over 24 hr that likely contributed to chemoresistance. The data support the utility of carboplatin microdosing as a translatable approach for defining carboplatin-DNA monoadduct formation and repair, possibly by NER, which may be useful for characterizing chemoresistance in vivo.