Synergistic chemosensitivity of triple-negative breast cancer cell lines to poly(ADP-Ribose) polymerase inhibition, gemcitabine, and cisplatin

Poly (ADP-ribose) polymerase inhibitors in cancer therapy

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPis) have emerged as critical agents for cancer therapy. By inhibiting the catalytic activity of PARP enzymes and trapping them in the DNA, PARPis disrupt DNA repair, ultimately leading to cell death, particularly in cancer cells with homologous recombination repair deficiencies, such as those harboring BRCA mutations. This review delves into the mechanisms of action of PARPis in anticancer treatments, including the inhibition of DNA repair, synthetic lethality, and replication stress. Furthermore, the clinical applications of PARPis in various cancers and their adverse effects as well as their combinations with other therapies and the mechanisms underlying resistance are summarized. This review provides comprehensive insights into the role and mechanisms of PARP and PARPis in DNA repair, with a particular focus on the potential of PARPi-based therapies in precision medicine for cancer treatment.

Prediction of small molecule drug-miRNA associations based on GNNs and CNNs

MicroRNAs (miRNAs) play a crucial role in various biological processes and human diseases, and are considered as therapeutic targets for small molecules (SMs). Due to the time-consuming and expensive biological experiments required to validate SM-miRNA associations, there is an urgent need to develop new computational models to predict novel SM-miRNA associations. The rapid development of end-to-end deep learning models and the introduction of ensemble learning ideas provide us with new solutions. Based on the idea of ensemble learning, we integrate graph neural networks (GNNs) and convolutional neural networks (CNNs) to propose a miRNA and small molecule association prediction model (GCNNMMA). Firstly, we use GNNs to effectively learn the molecular structure graph data of small molecule drugs, while using CNNs to learn the sequence data of miRNAs. Secondly, since the black-box effect of deep learning models makes them difficult to analyze and interpret, we introduce attention mechanisms to address this issue. Finally, the neural attention mechanism allows the CNNs model to learn the sequence data of miRNAs to determine the weight of sub-sequences in miRNAs, and then predict the association between miRNAs and small molecule drugs. To evaluate the effectiveness of GCNNMMA, we implement two different cross-validation (CV) methods based on two different datasets. Experimental results show that the cross-validation results of GCNNMMA on both datasets are better than those of other comparison models. In a case study, Fluorouracil was found to be associated with five different miRNAs in the top 10 predicted associations, and published experimental literature confirmed that Fluorouracil is a metabolic inhibitor used to treat liver cancer, breast cancer, and other tumors. Therefore, GCNNMMA is an effective tool for mining the relationship between small molecule drugs and miRNAs relevant to diseases.

BRCA1-methylated triple negative breast cancers previously exposed to neoadjuvant chemotherapy form RAD51 foci and respond poorly to olaparib

Background

About 15% of Triple-Negative-Breast-Cancer (TNBC) present silencing of the BRCA1 promoter methylation and are assumed to be Homologous Recombination Deficient (HRD). BRCA1-methylated (BRCA1-Me) TNBC could, thus, be eligible to treatment based on PARP-inhibitors or Platinum salts. However, their actual HRD status is discussed, as these tumors are suspected to develop resistance after chemotherapy exposure.

Methods

We interrogated the sensitivity to olaparib vs. carboplatin of 8 TNBC Patient-Derived Xenografts (PDX) models. Four PDX corresponded to BRCA1-Me, of which 3 were previously exposed to NeoAdjuvant-Chemotherapy (NACT). The remaining PDX models corresponded to two BRCA1-mutated (BRCA1-Mut) and two BRCA1-wild type PDX that were respectively included as positive and negative controls. The HRD status of our PDX models was assessed using both genomic signatures and the functional BRCA1 and RAD51 nuclear foci formation assay. To assess HR restoration associated with olaparib resistance, we studied pairs of BRCA1 deficient cell lines and their resistant subclones.

Results

The 3 BRCA1-Me PDX that had been exposed to NACT responded poorly to olaparib, likewise BRCA1-WT PDX. Contrastingly, 3 treatment-naïve BRCA1-deficient PDX (1 BRCA1-Me and 2 BRCA1-mutated) responded to olaparib. Noticeably, the three olaparib-responsive PDX scored negative for BRCA1- and RAD51-foci, whereas all non-responsive PDX models, including the 3 NACT-exposed BRCA1-Me PDX, scored positive for RAD51-foci. This suggested HRD in olaparib responsive PDX, while non-responsive models were HR proficient. These results were consistent with observations in cell lines showing a significant increase of RAD51-foci in olaparib-resistant subclones compared with sensitive parental cells, suggesting HR restoration in these models.

Conclusion

Our results thus support the notion that the actual HRD status of BRCA1-Me TNBC, especially if previously exposed to chemotherapy, may be questioned and should be verified using the BRCA1- and RAD51-foci assay.

Theranostics for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with poor prognosis. Current endocrine therapy or anti HER-2 therapy is not available for these patients. Chemotherapeutic treatment response varies among patients due to the disease heterogeneity. To overcome these challenges, theranostics for treating TNBC have been widely investigated. Anticancer material conjugated nanoparticles with target-binding ligand and tracer agents enable simultaneous drug delivery and visualization of the lesion with minimal off-target toxicity. In this review, we summarize recently FDA-approved targeted therapies for TNBC, such as poly-ADP-ribose polymerase (PARP) inhibitors, check point inhibitors, and antibody-drug conjugates. Particularly, novel theranostic approaches including lipid-based, polymer-based, and carbon-based nanocarriers are discussed, which can provide basic overview of nano-therapeutic modalities in TNBC diagnosis and treatment.

Molecular intrinsic subtypes, genomic, and immune landscapes of BRCA-proficient but HRD-high ER-positive/HER2-negative early breast cancers

Purpose

The vast majority of research studies that have described the links between DNA damage repair or homologous recombination deficiency (HRD) score, and tumor biology, have concerned either triple negative breast cancers or cancers with mutation of BRCA 1/2. We hypothesized that ER + /HER2- early breast tumors without BRCA 1/2 mutation could have high HRD score and aimed to describe their genomic, transcriptomic, and immune landscapes.

Patients and methods

In this study, we reported BRCA 1/2 mutational status, HRD score, and mutational signature 3 (S3) expression, in all early breast cancer (eBC) subtypes from the TCGA database, with a particular focus in ER + /HER2-. In this subtype, bioinformatics analyses of tumor transcriptomic, immune profile, and mutational landscape were performed, according to HRD status. Overall survival (OS), progression free-interval (PFI), and variables associated with outcome were also evaluated.

Results

Among the 928 tumor samples analyzed, 46 harbored BRCA 1/2 mutations, and 606 were ER + /HER2- (of which 24 were BRCA 1/2 mutated). We found a subset of BRCA-proficient ER + /HER2— eBC, with high HRD score. These tumors displayed significantly different immune, mutational, and tumor molecular signatures landscapes, compared to BRCA-mutated and BRCA-proficient HRD-low tumors. Outcome did not significantly differ between these 3 groups, but biological factors associated with survival are not the same across the 3 entities.

Conclusion

This study highlights possible novel biological differences among ER + /HER2- breast cancer related to HRD status. Our results could have important implications for translational research and/or the design of future clinical trials, but require prospective clinical evaluation.

Current landscape of personalized clinical treatments for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly malignant subtype of breast cancer (BC) with vicious behaviors. TNBC is usually associated with relatively poor clinical outcomes, earlier recurrence, and high propensity for visceral metastases than other BC types. TNBC has been increasingly recognized to constitute a very molecular heterogeneous subtype, which may offer additional therapeutic opportunities due to newly discovered cancer-causing drivers and targets. At present, there are multiple novel targeted therapeutic drugs in preclinical researches, clinical trial designs, and clinical practices, such as platinum drugs, poly ADP-ribose polymerase (PARP) inhibitors, immunocheckpoint inhibitors, androgen receptor inhibitors as well as PI3K/AKT/mTOR targeted inhibitors. These personalized, single, or combinational therapies based on molecular heterogeneity are currently showing positive results. The scope of this review is to highlight the latest knowledge about these potential TNBC therapeutic drugs, which will provide comprehensive insights into the personalized therapeutic strategies and options for combating TNBC.

Promotion of tumor progression induced by continuous low-dose administration of antineoplastic agent gemcitabine or gemcitabine combined with cisplatin

BACKGROUND AND OBJECTIVES

There are indications that certain antineoplastic agents at low dosages may exhibit abnormal pharmacological actions, such as promoting tumor growth. However, the phenomenon still needs to be further confirmed, and its underlying mechanisms have not yet been fully elucidated.

METHODS

Gemcitabine (GEM) and cisplatin (CDDP) were employed as representative antineoplastic agents to observe effects of continuous low-dose chemotherapy with GEM or GEM combined with CDDP (GEM+CDDP) on tumor formation and growthin xenograft tumor models in vivo. Tumor and endothelial cell functions, apoptosis, cell cycle analysis, as well as bone marrow derived cells (BMDCs) mobilization, were evaluated with transwell, MTT or flow cytometry analysis in vitro, respectively. Histological methods were employed to assess angiogenesis in tumor tissues.

RESULTS

The results showed that tumor formation and growth were both significantly promoted by GEM or GEM+CDDP at as low as half of the metronomic dosages, which were accompanied by enhancements of angiogenesis in tumor tissues and the release of proangiogenic BMDCs in the circulating blood. Additionally, GEM or GEM+CDDP at low concentrations dramatically facilitated the proliferation, migration, and invasion of tumor cells in vitro. Cell-cycle arrest, activation of associated apoptotic proteins, and inhibition of apoptosis were also observed in tumor cells.

CONCLUSIONS

These findings indicate that, the continuous low-dose administration of GEM and GEM+CDDP can promote tumorigenesis and tumor progression in vivo by inhibiting apoptosis, mobilizing BMDCs, and promoting angiogenesis in certain dose ranges. These findings urge further investigations to avoid the potential risks in current empiric continuous low-dose chemotherapy regimens with antineoplastic agents.

MAJOR FINDING

This study observes a previously neglected pharmacological phenomenon and investigates its mechanism of that the continuous low-dose administration of some antineoplastic agents in certain dose ranges can promote tumorigenesis and tumor progression in vitro and in vivo, through stimulation of tumor cell functions directly as well as enhancement of tumor angiogenesis by BMDCs recruitment indirectly. The results alert to a potential risk in current empirically based continuous low-dose chemotherapy regimens such as metronomic chemotherapy.

New Roles of Poly(ADP-Ribose) Polymerase Inhibitors in the Treatment of Breast Cancer

ABSTRACT

Since the proof of concept of synthetic lethality between poly(ADP-ribose) polymerase inhibition and loss of BRCA1/2 homologous recombination (HR) function in preclinical models and early phase clinical trials, poly(ADP-ribose) polymerase inhibitors (PARPi) are increasing part of standard-of-care treatment for advanced breast cancers with BRCA gene mutations. The field has also recently seen benefits for PARPi in early breast cancer in those with germline BRCA1 and BRCA2 pathogenic mutations, and signals that synthetic lethal affects may occur in tumors with deficiencies in HR caused by germline, somatic, or epigenetic dysregulation of a number of HR genes. Despite the evidence of the synthetic lethal effects of PARPi, they are not always effective in HR defective cancers, and as they become part of standard of care in breast cancer, the study of prevalence of distinct mechanisms of resistance to PARPi and cross-resistance with other DNA-damaging agents such as platinum in breast cancer will be important and may inform therapy choices.

Impact of homologous recombination status and responses with veliparib combined with first-line chemotherapy in ovarian cancer in the Phase 3 VELIA/GOG-3005 study

OBJECTIVE

In the Phase 3 VELIA trial (NCT02470585), PARP inhibitor (PARPi) veliparib was combined with first-line chemotherapy and continued as maintenance for patients with ovarian carcinoma enrolled regardless of chemotherapy response or biomarker status. Here, we report exploratory analyses of the impact of homologous recombination deficient (HRD) or proficient (HRP) status on progression-free survival (PFS) and objective response rates during chemotherapy.

METHODS

Women with Stage III-IV ovarian carcinoma were randomized to veliparib-throughout, veliparib-combination-only, or placebo. Stratification factors included timing of surgery and germline BRCA mutation status. HRD status was dichotomized at genomic instability score 33. During combination therapy, CA-125 levels were measured at baseline and each cycle; radiographic responses were assessed every 9 weeks.

RESULTS

Of 1140 patients randomized, 742 had BRCA wild type (BRCAwt) tumors (HRP, n = 373; HRD/BRCAwt, n = 329). PFS hazard ratios between veliparib-throughout versus control were similar in both BRCAwt populations (HRD/BRCAwt: 22.9 vs 19.8 months; hazard ratio 0.76; 95% confidence interval [CI] 0.53-1.09; HRP: 15.0 vs 11.5 months; hazard ratio 0.765; 95% CI 0.56-1.04). By Cycle 3, the proportion with ≥90% CA-125 reduction from baseline was higher in those receiving veliparib (pooled arms) versus control (34% vs 23%; P = 0.0004); particularly in BRCAwt and HRP subgroups. Complete response rates among patients with measurable disease after surgery were 24% with veliparib (pooled arms) and 18% with control.

CONCLUSIONS

These results potentially broaden opportunities for PARPi utilization among patients who would not qualify for frontline PARPi maintenance based on other trials.

Targeting DNA repair pathway in cancer: Mechanisms and clinical application

Over the last decades, the growing understanding on DNA damage response (DDR) pathways has broadened the therapeutic landscape in oncology. It is becoming increasingly clear that the genomic instability of cells resulted from deficient DNA damage response contributes to the occurrence of cancer. One the other hand, these defects could also be exploited as a therapeutic opportunity, which is preferentially more deleterious in tumor cells than in normal cells. An expanding repertoire of DDR-targeting agents has rapidly expanded to inhibitors of multiple members involved in DDR pathways, including PARP, ATM, ATR, CHK1, WEE1, and DNA-PK. In this review, we sought to summarize the complex network of DNA repair machinery in cancer cells and discuss the underlying mechanism for the application of DDR inhibitors in cancer. With the past preclinical evidence and ongoing clinical trials, we also provide an overview of the history and current landscape of DDR inhibitors in cancer treatment, with special focus on the combination of DDR-targeted therapies with other cancer treatment strategies.

The p53 family member p73 in the regulation of cell stress response

During oncogenesis, cells become unrestrictedly proliferative thereby altering the tissue homeostasis and resulting in subsequent hyperplasia. This process is paralleled by resumption of cell cycle, aberrant DNA repair and blunting the apoptotic program in response to DNA damage. In most human cancers these processes are associated with malfunctioning of tumor suppressor p53. Intriguingly, in some cases two other members of the p53 family of proteins, transcription factors p63 and p73, can compensate for loss of p53. Although both p63 and p73 can bind the same DNA sequences as p53 and their transcriptionally active isoforms are able to regulate the expression of p53-dependent genes, the strongest overlap with p53 functions was detected for p73. Surprisingly, unlike p53, the p73 is rarely lost or mutated in cancers. On the contrary, its inactive isoforms are often overexpressed in cancer. In this review, we discuss several lines of evidence that cancer cells develop various mechanisms to repress p73-mediated cell death. Moreover, p73 isoforms may promote cancer growth by enhancing an anti-oxidative response, the Warburg effect and by repressing senescence. Thus, we speculate that the role of p73 in tumorigenesis can be ambivalent and hence, requires new therapeutic strategies that would specifically repress the oncogenic functions of p73, while keeping its tumor suppressive properties intact.

Differential whole-genome doubling and homologous recombination deficiencies across breast cancer subtypes from the Taiwanese population

Whole-genome doubling (WGD) is an early macro-evolutionary event in tumorigenesis, involving the doubling of an entire chromosome complement. However, its impact on breast cancer subtypes remains unclear. Here, we performed a comprehensive and quantitative analysis of WGD and its influence on breast cancer subtypes in patients from Taiwan and consequently highlight the genomic association between WGD and homologous recombination deficiency (HRD). A higher manifestation of WGD was reported in triple-negative breast cancer, conferring high chromosomal instability (CIN), while HER2 + tumors exhibited early WGD events, with widely varied CIN levels, compared to luminal-type tumors. An association of higher activity of de novo indel signature 2 with WGD and HRD in Taiwanese breast cancer patients was reported. A control test between WGD and pseudo non-WGD samples was further employed to support this finding. The study provides a better comprehension of tumorigenesis in breast cancer subtypes, thus assisting in personalized treatment.

Wu, Hsieh et al. analyze Taiwanese breast cancer patient samples using whole-exome sequencing to examine the heterogeneity and homogeneity in the timing and dependencies of somatic aberrations across disease subtypes. The authors focus on somatic alterations and related features that correlate with whole genome doubling, including homologous recombination deficiencies.

Anticancer activity of RAPTA-EA1 in triple-negative BRCA1 proficient breast cancer cells: single and combined treatment with the PARP inhibitor olaparib

RAPTA-EA1 is a promising glutathione transferase (GSTP-1) inhibitor that has previously been shown to inhibit the growth of various breast cancer cells. We studied the anticancer activity of RAPTA-EA1 on triple-negative BRCA1 competent breast cancer MDA-MB-231 cells. MDA-MB-231 cells are significantly more sensitive to RAPTA-EA1 than MCF-7 cells. Treatment reveals a higher degree of cytotoxicity than cisplatin against both cell lines. Ruthenium accumulation in MDA-MB-231 cells is mainly in the nuclear fraction (43%), followed by the cytoplasm (30%), and the mitochondria (27%). RAPTA-EA1 blocks cell growth at the G2/M phase, leading to nuclear condensation and cell death. The compound slightly inhibits DNA replication of the 3,426-bp fragment of the BRCA1 exon 11 of the cells, with approximately 0.6 lesion per the BRCA1 fragment. The expression of BRCA1 mRNA and its protein in the Ru-treated cells is curtailed by 50–80% compared to the untreated controls. Growth inhibition of the triple-negative BRCA1 wild-type MDA-MB-231 and the sporadic BRCA1 wild-type MCF-7 cells by olaparib (a poly [ADP-ribose] polymerase (PARP) inhibitor) is dose-dependent, with MDA-MB-231 cells being two-fold less susceptible to the drug than MCF-7 cells. Combining olaparib with RAPTA-EA1 results in a combination index (CI) of 0.78 (almost additive) in MDA-MB-231 cells and 0.24 (potent synergy) in the MCF-7 cells. The PARP inhibitor alone differently regulates the expression of BRCA1 mRNA in both cell lines, whereas the olaparib-RAPTA-EA1 combination induces overexpression of BRCA1 mRNA in these cells. However, the expression level of the BRCA1 protein is dramatically reduced after treatment with the combined inhibitors, compared with the untreated controls. This observation highlights the cellular responses of triple-negative BRCA1 proficient breast cancer MDA-MB-231 cells to RAPTA-EA1 through BRCA1 inhibition and provides insights into alternative treatments for breast cancer.

Poly (ADP-Ribose) Polymerase Inhibitor, ABT888, Improved Cisplatin Effect in Human Oral Cell Carcinoma

Cisplatin is one of the chemotherapeutic drugs used for the management of oral carcinoma, in which combined therapies are estimated to exert superior therapeutic efficacy compared with monotherapy. It is known that poly(ADP-ribosyl)ation is implicated in a multiplicity of cellular activities, such as DNA repair and cell death. Based on these, PARP inhibitors are used for the treatment of cancers; however, the capacity of PARP inhibitors associated to anti-cancer drugs have not been completely assessed in oral carcinoma. Here, we evaluated the effects of PARPi veliparib (ABT888) in combination with cisplatin on the survival of three human oral cancer cell lines HSC-2, Ca9-22 and CAL27 and we observed the effects of ABT888 alone or in combination with cisplatin on apoptosis and DNA damage repair mechanism. The results obtained showed that ABT888 induces a cytotoxicity effect on cell viability increasing the apoptotic pathway as well as DNA strand break; moreover, our results displayed the effects with cisplatin in a dose-dependent manner. Therefore, our results indicate PARP inhibitors as adjuvants for therapeutic strategy of oral cancer.

p66ShcA potentiates the cytotoxic response of triple-negative breast cancers to PARP inhibitors

Triple-negative breast cancers (TNBCs) lack effective targeted therapies, and cytotoxic chemotherapies remain the standard of care for this subtype. Owing to their increased genomic instability, poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) are being tested against TNBCs. In particular, clinical trials are now interrogating the efficacy of PARPi combined with chemotherapies. Intriguingly, while response rates are low, cohort of patients do respond to PARPi in combination with chemotherapies. Moreover, recent studies suggest that an increase in levels of ROS may sensitize cells to PARPi. This represents a therapeutic opportunity, as several chemotherapies, including doxorubicin, function in part by producing ROS. We previously demonstrated that the p66ShcA adaptor protein is variably expressed in TNBCs. We now show that, in response to therapy-induced stress, p66ShcA stimulated ROS production, which, in turn, potentiated the synergy of PARPi in combination with doxorubicin in TNBCs. This p66ShcA-induced sensitivity relied on the accumulation of oxidative damage in TNBCs, rather than genomic instability, to potentiate cell death. These findings suggest that increasing the expression of p66ShcA protein levels in TNBCs represents a rational approach to bolster the synergy between PARPi and doxorubicin.

The cancer-testis gene, MEIOB, sensitizes triple-negative breast cancer to PARP1 inhibitors by inducing homologous recombination deficiency

Objective

The newly defined cancer-testis (CT) gene, MEIOB, was previously found to play key roles in DNA double-strand break (DSB) repair. In this study, we aimed to investigate the effects and mechanisms of MEIOB in the carcinogenesis of triple-negative breast cancers (TNBCs).

Methods

The Cancer Genome Atlas database was used to quantify the expression of MEIOB. Cox regression analysis was used to evaluate the association between MEIOB expression and the prognosis of human TNBC. The effects of MEIOB on cell proliferation and migration in TNBCs were also assessed in vitro. Patient-derived xenograft (PDX) models were used to assess the sensitivity of breast cancers with active MEIOB to PARP1 inhibitors.

Results

We confirmed MEIOB as a CT gene whose expression was restricted to the testes and breast tumors, especially TNBCs. Its activation was significantly associated with poor survival in breast cancer patients [overall, hazard ratio (HR) = 1.90 (1.16-2.06); TNBCs: HR = 7.05 (1.16-41.80)]. In addition, we found that MEIOB was oncogenic and significantly promoted the proliferation of TNBC cells. Further analysis showed that MEIOB participated in DSB repair in TNBCs. However, in contrast to its function in meiosis, it mediated homologous recombination deficiency (HRD) through the activation of polyADP-ribose polymerase (PARP)1 by interacting with YBX1. Furthermore, activated MEIOB was shown to confer sensitivity to PARP inhibitors, which was confirmed in PDX models.

Conclusions

MEIOB played an oncogenic role in TNBC through its involvement in HRD. In addition, dysregulation of MEIOB sensitized TNBC cells to PARP inhibitors, so MEIOB may be a therapeutic target of PARP1 inhibitors in TNBC.

Combining PARP Inhibition with Platinum, Ruthenium or Gold Complexes for Cancer Therapy

Platinum drugs are heavily used first-line chemotherapeutic agents for many solid tumours and have stimulated substantial interest in the biological activity of DNA-binding metal complexes. These complexes generate DNA lesions which trigger the activation of DNA damage response (DDR) pathways that are essential to maintain genomic integrity. Cancer cells exploit this intrinsic DNA repair network to counteract many types of chemotherapies. Now, advances in the molecular biology of cancer has paved the way for the combination of DDR inhibitors such as poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) and agents that induce high levels of DNA replication stress or single-strand break damage for synergistic cancer cell killing. In this review, we summarise early-stage, preclinical and clinical findings exploring platinum and emerging ruthenium anti-cancer complexes alongside PARPi in combination therapy for cancer and also describe emerging work on the ability of ruthenium and gold complexes to directly inhibit PARP activity.

A Preclinical Trial and Molecularly Annotated Patient Cohort Identify Predictive Biomarkers in Homologous Recombination–deficient Pancreatic Cancer

Purpose:

Pancreatic ductal adenocarcinoma (PDAC) arising in patients with a germline BRCA1 or BRCA2 (gBRCA) mutation may be sensitive to platinum and PARP inhibitors (PARPi). However, treatment stratification based on gBRCA mutational status alone is associated with heterogeneous responses.

Experimental Design:

We performed a seven-arm preclinical trial consisting of 471 mice, representing 12 unique PDAC patient-derived xenografts, of which nine were gBRCA mutated. From 179 patients whose PDAC was whole-genome and transcriptome sequenced, we identified 21 cases with homologous recombination deficiency (HRD), and investigated prognostic biomarkers.

Results:

We found that biallelic inactivation of BRCA1/BRCA2 is associated with genomic hallmarks of HRD and required for cisplatin and talazoparib (PARPi) sensitivity. However, HRD genomic hallmarks persisted in xenografts despite the emergence of therapy resistance, indicating the presence of a genomic scar. We identified tumor polyploidy and a low Ki67 index as predictors of poor cisplatin and talazoparib response. In patients with HRD PDAC, tumor polyploidy and a basal-like transcriptomic subtype were independent predictors of shorter survival. To facilitate clinical assignment of transcriptomic subtype, we developed a novel pragmatic two-marker assay (GATA6:KRT17).

Conclusions:

In summary, we propose a predictive and prognostic model of gBRCA-mutated PDAC on the basis of HRD genomic hallmarks, Ki67 index, tumor ploidy, and transcriptomic subtype.

Neo-adjuvant therapy for triple-negative breast cancer: Insights from a network meta-analysis

BACKGROUND

The best regimen of neo-adjuvant therapy for triple-negative breast cancer (TNBC) is unknown. Recent studies have shown promising data that adding carboplatin or pembrolizumab improves the rate of pathologic complete response (pCR) in TNBC. Therefore, we performed a network meta-analysis to define the overall, most effective, neo-adjuvant systemic therapy for TNBC.

METHODS

We searched for studies comparing different neo-adjuvant regimens in patients with TNBC. We performed a network meta-analysis comparing the regimens using the random-effects model. We focused on anthracycline, bevacizumab, pembrolizumab, and platinum salts (Pl). All study regimens contained a taxane. We analyzed the rate of pCR (ypT0/is, N0), and the incidence of febrile neutropenia, grade 3-grade 4 thrombocytopenia, nausea/vomiting, and diarrhea.

RESULTS

We identified a total of 13 randomized control trials for this analysis. We compared ten different classes of regimens. We found that regimens containing Pl were significantly superior to non-PI-containing regimens for the rate of pCR. Similarly, pembrolizumab-containing regimens were associated with significantly higher pCR rates. Regimens containing bevacizumab significantly increased the rate of pCR as well. However, it was equivocal as to whether the addition of Pl to pembrolizumab-containing regimen increases pCR rates. Adding anthracycline into the regimen did not show an improved rate of pCR. In the safety analysis, regimens containing Pl were associated with a significantly higher incidence of febrile neutropenia and grade 3-grade 4 thrombocytopenia. The regimen containing anthracycline plus bevacizumab plus Pl was associated with a higher risk of gastrointestinal adverse events.

CONCLUSIONS

For TNBC, regimens containing bevacizumab, pembrolizumab, or Pl are most effective in terms of pCR rates, though it is unclear whether combining all these medications has the greatest efficacy. Additionally, the benefit of using anthracycline in the neo-adjuvant therapy regimen for TNBC is not apparent, which may warrant a further head-to-head comparison.

Cisplatin given at three divided doses for three consecutive days in metastatic breast cancer: an alternative schedule for one full dose with comparable efficacy but less CINV and hypomagnesaemia

PURPOSE

Cisplatin, an effective medication for metastatic breast cancer (MBC), is recommended to be applied at the dose of 75 mg/m² on day 1 every 3 weeks. However, the 75 mg/m² schedule is often associated with a variety of side effects (such as vomiting and kidney toxicity), and time-consuming hydration treatment is usually needed. Divided dose (25 mg/m² on day 1-3) without hydration is an alternative. This study aimed to compare the efficacy and toxicity profiles between these two dosage regimens.

METHODS

Patients with MBC treated with cisplatin-based regimens in Fudan University Shanghai Cancer Center between December 2008 and June 2019 were retrospectively analyzed. Objective response rate (ORR), progression-free survival (PFS), and toxicity profiles were analyzed.

RESULTS

227 patients receiving a 1-day schedule and 256 patients receiving a 3-day schedule were included. Median PFS was 6.68 (5.66-7.70) months for patients in the 1-day schedule group and 6.70 (5.89-7.52) months for patients in the 3-day schedule group. There was no statistically significant difference in PFS between the two treatment groups (hazard ratio, 0.942; 95% CI 0.759 to 1.170; P = 0.589). The ORRs were comparable between the two groups. ORRs were 44.9% in 1-day schedule group and 44.5% in 3-day schedule group, respectively (P = 0.929). Compared with patients in the 3-day schedule group, patients in the 1-day schedule group experienced higher rates of chemotherapy-induced nausea and vomiting (CINV) (139 [61.2%] vs. 132 [51.6%], P = 0.033). The risk of hypomagnesaemia was also significantly higher (43.2% vs. 28.3%, P = 0.016) among patients receiving 1-day schedule (without magnesium supplementation). No other differences in adverse events were observed between the two groups.

CONCLUSIONS

Cisplatin given at three divided doses with no hydration in MBC is a less toxic (less CINV and hypomagnesaemia) schedule with comparable efficacy. Thus, it may be a good alternative for one full-dose (75 mg/m²) schedule.

Predictive Biomarkers for Adjuvant Capecitabine Benefit in Early-Stage Triple-Negative Breast Cancer in the FinXX Clinical Trial

PURPOSE

Recent studies have demonstrated a benefit of adjuvant capecitabine in early breast cancer, particularly in patients with triple-negative breast cancer (TNBC). However, TNBC is heterogeneous and more precise predictive biomarkers are needed.

EXPERIMENTAL DESIGN

Tumor tissues collected from TNBC patients in the FinXX trial, randomized to adjuvant anthracycline-taxane-based chemotherapy with or without capecitabine, were analyzed using a 770-gene panel targeting multiple biological mechanisms and additional 30-custom genes related to capecitabine metabolism. Hypothesis-generating exploratory analyses were performed to assess biomarker expression in relation to treatment effect using the Cox regression model and interaction tests adjusted for multiplicity.

RESULTS

One hundred eleven TNBC samples were evaluable (57 without capecitabine and 54 with capecitabine). The median follow-up was 10.2 years. Multivariate analysis showed significant improvement in recurrence-free survival (RFS) favoring capecitabine in four biologically important genes and metagenes, including cytotoxic cells [hazard ratio (HR) = 0.38; 95% confidence intervals (CI), 0.16-0.86, P-interaction = 0.01], endothelial (HR = 0.67; 95% CI, 0.20-2.22, P-interaction = 0.02), mast cells (HR = 0.78; 95% CI, 0.49-1.27, P-interaction = 0.04), and PDL2 (HR = 0.31; 95% CI, 0.12-0.81, P-interaction = 0.03). Furthermore, we identified 38 single genes that were significantly associated with capecitabine benefit, and these were dominated by immune response pathway and enzymes involved in activating capecitabine to fluorouracil, including TYMP. However, these results were not significant when adjusted for multiple testing.

CONCLUSIONS

Genes and metagenes related to antitumor immunity, immune response, and capecitabine activation could identify TNBC patients who are more likely to benefit from adjuvant capecitabine. Given the reduced power to observe significant findings when correcting for multiplicity, our findings provide the basis for future hypothesis-testing validation studies on larger clinical trials.

A Small Compound KJ-28d Enhances the Sensitivity of Non-Small Cell Lung Cancer to Radio- and Chemotherapy

We previously reported on a poly (ADP-ribose) polymerase (PARP) 1/2 inhibitor N-(3-(hydroxycarbamoyl)phenyl)carboxamide (designated KJ-28d), which increased the death of human ovarian cancer BRCA1-deficient SNU-251 cells. In the present study, we further investigated the antitumor activities of KJ-28d in BRCA-proficient non-small cell lung cancer (NSCLC) cells to expand the use of PARP inhibitors. KJ-28d significantly inhibited the growth of NSCLC cells in vitro and in vivo, and induced DNA damage and reactive oxygen species in A549 and H1299 cells. Combined treatment with KJ-28d and ionizing radiation led to increased DNA damage responses in A549 and H1299 cells compared to KJ-28d or ionizing radiation alone, resulting in apoptotic cell death. Moreover, the combination of KJ-28d plus a DNA-damaging therapeutic agent (carboplatin, cisplatin, paclitaxel, or doxorubicin) synergistically inhibited cell proliferation, compared to either drug alone. Taken together, the findings demonstrate the potential of KJ-28d as an effective anti-cancer therapeutic agent for BRCA-deficient and -proficient cancer cells. KJ-28d might have potential as an adjuvant when used in combination with radiotherapy or DNA-damaging agents, pending further investigations.

Role of the YAP-1 Transcriptional Target cIAP2 in the Differential Susceptibility to Chemotherapy of Non-Small-Cell Lung Cancer (NSCLC) Patients with Tumor RASSF1A Gene Methylation from the Phase 3 IFCT-0002 Trial

RASSF1 gene methylation predicts longer disease-free survival (DFS) and overall survival (OS) in patients with early-stage non-small-cell lung cancer treated using paclitaxel-based neo-adjuvant chemotherapy compared to patients receiving a gemcitabine-based regimen, according to the randomized Phase 3 IFCT (Intergroupe Francophone de Cancérologie Thoracique)-0002 trial. To better understand these results, this study used four human bronchial epithelial cell (HBEC) models (HBEC-3, HBEC-3-RasV12, A549, and H1299) and modulated the expression of RASSF1A or YAP-1. Wound-healing, invasion, proliferation and apoptosis assays were then carried out and the expression of YAP-1 transcriptional targets was quantified using a quantitative polymerase chain reaction. This study reports herein that gemcitabine synergizes with RASSF1A, silencing to increase the IAP-2 expression, which in turn not only interferes with cell proliferation but also promotes cell migration. This contributes to the aggressive behavior of RASSF1A-depleted cells, as confirmed by a combined knockdown of IAP-2 and RASSF1A. Conversely, paclitaxel does not increase the IAP-2 expression but limits the invasiveness of RASSF1A-depleted cells, presumably by rescuing microtubule stabilization. Overall, these data provide a functional insight that supports the prognostic value of RASSF1 gene methylation on survival of early-stage lung cancer patients receiving perioperative paclitaxel-based treatment compared to gemcitabine-based treatment, identifying IAP-2 as a novel biomarker indicative of YAP-1-mediated modulation of chemo-sensitivity in lung cancer.

Validation of the DNA Damage Immune Response Signature in Patients With Triple-Negative Breast Cancer From the SWOG 9313c Trial

PURPOSE

To independently validate two biomarkers, a 44-gene DNA damage immune response (DDIR) signature and stromal tumor-infiltrating lymphocytes (sTILs), as prognostic markers in patients with triple-negative breast cancer (TNBC) treated with adjuvant doxorubicin (A) and cyclophosphamide (C) in SWOG 9313.

METHODS

Four hundred twenty-five centrally determined patient cases with TNBC from S9313 were identified. DDIR signature was performed on RNA isolated from formalin-fixed paraffin-embedded tumor tissue, and samples were classified as DDIR negative or positive using predefined cutoffs. Evaluation of sTILs was performed as described previously. Markers were tested for prognostic value for disease-free survival (DFS) and overall survival (OS) using Cox regression models adjusted for treatment assignment, nodal status, and tumor size.

RESULTS

Among 425 patients with TNBC, 33% were node positive. DDIR was tested successfully in 90% of patients (381 of 425), 62% of which were DDIR signature positive. DDIR signature positivity was associated with improved DFS (hazard ratio [HR], 0.67; 95% CI, 0.48 to 0.92; P = .015) and OS (HR, 0.61; 95% CI, 0.43 to 0.89; P = .010). sTILs density assessment was available in 99% of patients and was associated with improved DFS (HR, 0.70; 95% CI, 0.51 to 0.96; P = .026 for sTILs density ≥ 20% v < 20%) and OS (HR, 0.59; 95% CI, 0.41 to 0.85; P = .004 for sTILs density ≥ 20% v < 20%). DDIR signature score and sTILs density were moderately correlated (r = 0.60), which precluded statistical significance for DFS in a joint model. Three-year DFS and OS in a subgroup of patients with DDIR positivity and T1c/T2N0 disease were 88% and 94%, respectively.

CONCLUSION

The prognostic role of sTILs and DDIR in early-stage TNBC was confirmed. DDIR signature conferred improved prognosis in two thirds of patients with TNBC treated with adjuvant AC. DDIR signature has the potential to stratify outcome and to identify patients with less projected benefit after AC chemotherapy.

Defective base excision repair in the response to DNA damaging agents in triple negative breast cancer

DNA repair defects have been increasingly focused on as therapeutic targets. In hormone-positive breast cancer, XRCC1-deficient tumors have been identified and proposed as targets for combination therapies that damage DNA and inhibit DNA repair pathways. XRCC1 is a scaffold protein that functions in base excision repair (BER) by mediating essential interactions between DNA glycosylases, AP endonuclease, poly(ADP-ribose) polymerase 1, DNA polymerase β (POL β), and DNA ligases. Loss of XRCC1 confers BER defects and hypersensitivity to DNA damaging agents. BER defects have not been evaluated in triple negative breast cancers (TNBC), for which new therapeutic targets and therapies are needed. To evaluate the potential of XRCC1 as an indicator of BER defects in TNBC, we examined XRCC1 expression in the TCGA database and its expression and localization in TNBC cell lines. The TCGA database revealed high XRCC1 expression in TNBC tumors and TNBC cell lines show variable, but mostly high expression of XRCC1. XRCC1 localized outside of the nucleus in some TNBC cell lines, altering their ability to repair base lesions and single-strand breaks. Subcellular localization of POL β also varied and did not correlate with XRCC1 localization. Basal levels of DNA damage correlated with observed changes in XRCC1 expression, localization, and measure repair capacity. The results confirmed that XRCC1 expression changes indicate DNA repair capacity changes but emphasize that basal DNA damage levels along with protein localization are better indicators of DNA repair defects. Given the observed over-expression of XRCC1 in TNBC preclinical models and tumors, XRCC1 expression levels should be assessed when evaluating treatment responses of TNBC preclinical model cells.

Phase 1 study of veliparib (ABT-888), a poly (ADP-ribose) polymerase inhibitor, with carboplatin and paclitaxel in advanced solid malignancies

PURPOSE

Veliparib is an oral inhibitor of poly (ADP-ribose) polymerase (PARP)-1 and -2. PARP-1 expression may be increased in cancer, and this increase confers resistance to cytotoxic agents. We aimed to determine the recommended phase 2 dose (RP2D), maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics (PK) of veliparib combined with paclitaxel and carboplatin.

METHODS

Eligibility criteria included patients with advanced solid tumors treated with ≤ 3 prior regimens. Paclitaxel and carboplatin were administered on day 3 of a 21-day cycle. Veliparib was given PO BID days 1-7, except for cycle 1 in the first 46 patients to serve as control for toxicity and PK. A standard "3 + 3" design started veliparib at 10 mg BID, paclitaxel at 150 mg/m², and carboplatin AUC 6. The pharmacokinetic (PK) disposition of veliparib, paclitaxel, and carboplatin was determined by LC-MS/MS and AAS during cycles 1 and 2.

RESULTS

Seventy-three patients were enrolled. Toxicities were as expected with carboplatin/paclitaxel chemotherapy, including neutropenia, thrombocytopenia, and peripheral neuropathy. DLTs were seen in two of seven evaluable patients at the maximum administered dose (MAD): veliparib 120 mg BID, paclitaxel 200 mg/m², and carboplatin AUC 6 (febrile neutropenia, hyponatremia). The MTD and RP2D were determined to be veliparib 100 mg BID, paclitaxel 200 mg/m², and carboplatin AUC 6. Median number of cycles of the three-agent combination was 4 (1-16). We observed 22 partial and 5 complete responses. Veliparib did not affect paclitaxel or carboplatin PK disposition.

CONCLUSION

Veliparib, paclitaxel, and carboplatin were well tolerated and demonstrated promising antitumor activity.

Poly-ADP-ribose polymerases (PARPs) as a therapeutic target in the treatment of selected cancers

Introduction: The implementation of poly-ADP-ribose polymerase (PARP) inhibitors for therapy has created potential treatments for a wide spectrum of malignancies involving DNA damage repair gene abnormalities. PARPs are a group of enzymes that are responsible for detecting and repairing DNA damage and therefore play a key role in maintaining cell function and integrity. PARP inhibitors are drugs that target DNA repair deficiencies. Inhibiting PARP activity in cancer cells causes cell death. Areas covered: This review summarizes the role of PARP inhibitors in the treatment of cancer. We performed a systematic literature search in February 2019 in the electronic databases PubMed and EMBASE. Our search terms were the following: PARP, PARP inhibitors, PARPi, Poly ADP ribose polymerase, cancer treatment. We discuss PARP inhibitors currently being investigated in cancer clinical trials, their safety profiles, clinical resistance, combined therapeutic approaches and future challenges. Expert Opinion: The future could bring novel PARP inhibitors with greater DNA trapping potential, better safety profiles and improved combined therapies involving hormonal, chemo-, radio- or immunotherapies. Progress may afford wider indications for PARP inhibitors in the treatment of cancer and the utilization for cancer prevention in high-risk mutation carriers. Research efforts should focus on identifying novel drugs that target DNA repair deficiencies.

PARP-1 inhibitor modulate β-catenin signaling to enhance cisplatin sensitivity in cancer cervix

Cisplatin is a keystone for treatment of both recurring and locally advanced cervical cancer. However toxic side effects and acquired resistance limits its efficacy. Enhanced DNA repair is one of the mechanisms through which cancer cells acquire cisplatin resistance. Inhibitors of PARP, which is a DNA damage repair enzyme, have been approved for use in BRCA mutated cancers like breast and ovary cancer. However little is known about the therapeutic efficacy of PARP inhibitors in cervical cancer, either as a single agent or in combination with cisplatin. We hypothesized that PARP-1 inhibition might improve the sensitivity of cervical cancer cells to cisplatin by diminishing DNA repair. To ascertain this, we determined effect of PARP-1 inhibition on cisplatin cytotoxicity in HeLa and SiHa cell lines. Combination of cisplatin with PJ34, a phenanthridinone-derived PARP-1 inhibitor, augmented cisplatin toxicity in vitro by decreasing cell proliferation, enhancing cell cycle block and cell death, and decreasing invasion and metastasis, when compared with either of the single agent alone. We further show that PARP-1 inhibition inhibited β-catenin signaling and its downstream components such as c-Myc, cyclin D1 and MMPs indicating a possible link between single strand base damage repair and WNT signaling. In conclusion, PARP-1 inhibition might augment cisplatin cytotoxicity in cervical cancer cells by modulating β-catenin signaling pathway. Combining PARP-1 inhibitors with cisplatin might be a promising approach to overcome cisplatin resistance and to achieve a better therapeutic effect.

DNA Double Strand Break Repair - Related Synthetic Lethality

Cancer is a heterogeneous disease with a high degree of diversity between and within tumors. Our limited knowledge of their biology results in ineffective treatment. However, personalized approach may represent a milestone in the field of anticancer therapy. It can increase specificity of treatment against tumor initiating cancer stem cells (CSCs) and cancer progenitor cells (CPCs) with minimal effect on normal cells and tissues. Cancerous cells carry multiple genetic and epigenetic aberrations which may disrupt pathways essential for cell survival. Discovery of synthetic lethality has led a new hope of creating effective and personalized antitumor treatment. Synthetic lethality occurs when simultaneous inactivation of two genes or their products causes cell death whereas individual inactivation of either gene is not lethal. The effectiveness of numerous anti-tumor therapies depends on induction of DNA damage therefore tumor cells expressing abnormalities in genes whose products are crucial for DNA repair pathways are promising targets for synthetic lethality. Here, we discuss mechanistic aspects of synthetic lethality in the context of deficiencies in DNA double strand break repair pathways. In addition, we review clinical trials utilizing synthetic lethality interactions and discuss the mechanisms of resistance.

Prospect for Application of PARP Inhibitor in Patients with HER2 Negative Breast Cancer

Human epidermal growth factor receptor (HER2) negative metastatic breast cancer (BC) accounts for 73% of BC. The molecular analysis of this disease is essential for potential options for targeted therapy. Several promising clinical strategies are being evaluated which includes endocrine therapy, modified chemotherapy, angiogenesis inhibitors, immune checkpoint inhibitors, and anti-androgens. New therapeutic approaches are being developed that target BC patients with germline mutations in either BRCA1, BRCA2 as well as BRCAness, a condition in which tumors have molecular similarity to BRCA-mutated tumors. Poly (ADP-ribose) polymerase inhibitors (PARPi) which are effective therapy in germline BRCA1 and BRCA2 mutations, are also observed to be effective in somatic mutations. Germline mutations in the homologous recombination pathway genes could also contribute to PARPi sensitivity. PARPi act as chemo- and radio-sensitizers by limiting the DNA-damage response and potentiating the activity of chemo- and radio-therapy when used alone or in combination with chemotherapy. Apart from PARPi as monotherapy, additional researches are ongoing in combination with cytotoxic chemotherapeutics and targeted agents in HER2 negative BC. This review aims at the most recent developments in the targeted therapy, summarizes the recent clinical trials outcomes, along with the overview of ongoing clinical trials in HER2 negative patients with BRCA1/2 mutations and sporadic tumors with BRCAness.

CIB1 depletion with docetaxel or TRAIL enhances triple-negative breast cancer cell death

Background

Patients diagnosed with triple negative breast cancer (TNBC) have limited treatment options and often suffer from resistance and toxicity due to chemotherapy. We previously found that depleting calcium and integrin-binding protein 1 (CIB1) induces cell death selectively in TNBC cells, while sparing normal cells. Therefore, we asked whether CIB1 depletion further enhances tumor-specific killing when combined with either the commonly used chemotherapeutic, docetaxel, or the cell death-inducing ligand, TRAIL.

Methods

We targeted CIB1 by RNA interference in MDA-MB-436, MDA-MB-231, MDA-MB-468, docetaxel-resistant MDA-MB-436 TNBC cells and ME16C normal breast epithelial cells alone or combination with docetaxel or TRAIL. Cell death was quantified via trypan blue exclusion using flow cytometry and cell death mechanisms were analyzed by Western blotting. Cell surface levels of TRAIL receptors were measured by flow cytometry analysis.

Results

CIB1 depletion combined with docetaxel significantly enhanced tumor-specific cell death relative to each treatment alone. The enhanced cell death strongly correlated with caspase-8 activation, a hallmark of death receptor-mediated apoptosis. The death receptor TRAIL-R2 was upregulated in response to CIB1 depletion, which sensitized TNBC cells to the ligand TRAIL, resulting in a synergistic increase in cell death. In addition to death receptor-mediated apoptosis, both combination treatments activated a non-apoptotic mechanism, called paraptosis. Interestingly, these combination treatments also induced nearly complete death of docetaxel-resistant MDA-MB-436 cells, again via apoptosis and paraptosis. In contrast, neither combination treatment induced cell death in normal ME16C cells.

Conclusion

Novel combinations of CIB1 depletion with docetaxel or TRAIL selectively enhance naive and docetaxel-resistant TNBC cell death while sparing normal cell. Therefore, combination therapies that target CIB1 could prove to be a safe and durable strategy for treatment of TNBC and potentially other cancers.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0740-2) contains supplementary material, which is available to authorized users.

Recent advances in breast cancer research impacting clinical diagnostic practice

During the last decade, the genomics revolution has driven critical advances in molecular oncology and pathology, and a deeper appreciation of heterogeneity that is beginning to reshape our thinking around diagnostic classification. Recent developments have seen existing classification systems modified and improved where possible, gene-based diagnostics implemented and tumour-immune interactions modulated. We present a detailed discussion of this progress, including advances in the understanding of breast tumour classification, e.g. mixed ductal-lobular tumours and the spectrum of triple-negative breast cancer. The latest information on clinical trials and the implementation of gene-based diagnostics, including MammaPrint and Oncotype Dx and others, is synthesised, and emerging targeted therapies, as well as the burgeoning immuno-oncology field, and their relevance in breast cancer, are discussed. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Overexpression of PARP is an independent prognostic marker for poor survival in Middle Eastern breast cancer and its inhibition can be enhanced with embelin co-treatment

Patients with aggressive breast cancer (BC) subtypes usually don’t have favorable prognosis despite the improvement in treatment modalities. These cancers still remain a major cause of morbidity and mortality in females. This has fostered a major effort to discover actionable molecular targets to treat these patients. Poly ADP ribose polymerase (PARP) is one of these molecular targets that are under comprehensive investigation for treatment of such tumors. However, its role in the pathogenesis of BC from Middle Eastern ethnicity has not yet been explored. Therefore, we examined the expression of PARP protein in a large cohort of over 1000 Middle Eastern BC cases by immunohistochemistry. Correlation with clinico-pathological parameters were performed. Nuclear PARP overexpression was observed in 44.7% of all BC cases and was significantly associated with aggressive clinico-pathological markers. Interestingly, nuclear PARP overexpression was an independent predictor of poor prognosis. PARP overexpression was also directly associated with XIAP overexpression, with PARP and XIAP co-expression in 15.8% (159/1008) of our cases. We showed that combined inhibition of PARP by olaparib and XIAP by embelin significantly and synergistically inhibited cell growth and induced apoptosis in BC cell lines. Finally, co-treatment of olaparib and embelin regressed BC xenograft tumor growth in nude mice. Our results revealed the role of PARP in Middle Eastern BC pathogenesis and prognosis. Furthermore, our data support the potential clinical development of combined inhibition of PARP and XIAP, which eventually could extend the utility of olaparib beyond BRCA deficient cancer.

Basal biomarkers nestin and INPP4B predict gemcitabine benefit in metastatic breast cancer: Samples from the phase III SBG0102 clinical trial

In a formal prospective-retrospective analysis of the phase III SBG0102 clinical trial randomizing metastatic breast cancer patients to gemcitabine-docetaxel or to single agent docetaxel, patients with basal-like tumors by PAM50 gene expression had significantly better overall survival in the gemcitabine arm. By immunohistochemistry (IHC), triple negative status was not predictive, but more specific biomarkers have since become available defining basal-like by nestin positivity or loss of inositol-polyphosphate-4-phosphate (INPP4B). Here, we evaluate their capacity to identify which patients benefit from gemcitabine in the metastatic setting. Nestin and INPP4B staining and interpretation followed published methods. A prespecified statistical plan evaluated the primary hypothesis that patients with basal-like breast cancer, defined as "nestin+ or INPP4B-", would have superior overall survival on gemcitabine-docetaxel when compared to docetaxel. Interaction tests, Kaplan-Meier curves and forest plots were used to assess prognostic and predictive capacities of biomarkers relative to treatment. Among 239 cases evaluable for our study, 36 (15%) had been classified as basal-like by PAM50. "Nestin+ or INPP4B-" was observed in 41 (17%) of the total cases and was significantly associated with PAM50 basal-like subtype. Within an estimated median follow-up of 13 years, patients assigned as IHC basal "nestin+ or INPP4B-" had significantly better overall survival on gemcitabine-docetaxel versus docetaxel monotherapy (HR = 0.31, 95%CI: 0.16-0.60), whereas no differences were observed for other patients (HR = 0.99), p-interaction < 0.01. In the metastatic setting, women with IHC basal breast cancers defined as "nestin+ or INPP4B-" have superior overall survival when randomized to gemcitabine-containing chemotherapy compared to docetaxel alone. These findings need to be validated using larger prospective-retrospective phase III clinical trials series.

miR-3178 inhibits cell proliferation and metastasis by targeting Notch1 in triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a poorer outcome than other subtypes of breast cancer, and the discovery of dysregulated microRNA (miRNA) and their role in tumor progression has provided a new avenue for elucidating the mechanism involved in TNBC. In this study, we identified that miR-3178 was significantly reduced in TNBC, and the low miR-3178 expression correlated with poor overall survival in TNBC but not in non-TNBC. The ectopic overexpression of miR-3178 suppressed TNBC cell proliferation, invasion, and migration by inhibiting the epithelial-to-mesenchymal (EMT) transition. Notch1 was validated as the direct target gene of miR-3178, which was confirmed by the dual-luciferase reporter assay. miR-3178 decreased the expression of Notch1 and restoration of Notch1 expression attenuated the inhibitory effects of miR-3178 on cell proliferation, metastasis, and the EMT in TNBC. miR-3178 inhibited cell proliferation and metastasis by targeting Notch1 in TNBC, and the restoration of miR-3178 might be a potential therapeutic strategy for TNBC.

PARP inhibitors synergize with gemcitabine by potentiating DNA damage in non-small-cell lung cancer

Poly (ADP-ribose) polymerase (PARP) inhibitors have demonstrated great promise in the treatment of patients with deficiencies in homologous recombination (HR) DNA repair, such as those with loss of BRCA1 or BRCA2 function. However, emerging studies suggest that PARP inhibition can also target HR-competent cancers, such as non-small-cell lung cancer (NSCLC), and that the therapeutic effect of PARP inhibition may be improved by combination with chemotherapy agents. In our study, it was found that PARP inhibitors talazoparib (BMN-673) and olaparib (AZD-2281) both had synergistic activity with the common first-line chemotherapeutic gemcitabine in a panel of lung cancer cell lines. Furthermore, the combination demonstrated significant in vivo antitumor activity in an H23 xenograft model of NSCLC compared to either agent as monotherapy. This synergism occurred without loss of HR repair efficiency. Instead, the combination induced synergistic single-strand DNA breaks, leading to accumulation of toxic double-strand DNA lesions in vitro and in vivo. Our study elucidates the underlying mechanisms of synergistic activity of PARP inhibitors and gemcitabine, providing a strong motivation to pursue this combination as an improved therapeutic regimen.

5-aminoisoquinoline improves renal function and fibrosis during recovery phase of cisplatin-induced acute kidney injury in rats

The aim of the present study is to analyze the effects of 5-aminoisoquinoline (5-AIQ), a poly(ADP-ribose) polymerase-1 (PARP1) inhibitor, over renal dysfunction and fibrosis during recovery phase of cisplatin (CisPt)-induced acute kidney injury (AKI) in rats. Male Wistar rats were distributed in three groups (n=8 each group): control, CisPt, and CisPt + 5-AIQ. Control and CisPt groups received a subcutaneous injection of either saline or 7 mg/kg CisPt, respectively. CisPt + 5-AIQ group received two intraperitoneal injections of 10 mg/kg 5-AIQ 2 h before and 24 h after CisPt treatment. Thirteen days after the treatment, rats were housed in metabolic cages and 24-h urine collection was made. At day 14, CisPt-treated rats showed increased diuresis, N-acetyl-β-d-glucosaminidase (NAG) excretion, glucosuria and sodium fractional excretion (NaFE), and decreased creatinine clearance (CrCl). 5-AIQ significantly increased CrCl and decreased NAG excretion, glucosuria, and NaFE. In plasma, CisPt increased sodium, urea, and creatinine concentrations, while 5-AIQ treatment decreased these variables to the levels of control group. 5-AIQ completely prevented the body weight loss evoked by CisPt treatment. CisPt also induced an increased renal expression of PAR polymer, α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), and collagen-IV. These variables were decreased in CisPt + 5-AIQ group. Tubular lesions and renal fibrosis were also decreased by 5-AIQ treatment. We conclude that inhibition of PARP1 with 5-AIQ can attenuate long-term nephrotoxic effects associated with the CisPt treatment, preventing renal dysfunction and body weight decrease and ameliorating tubular lesions and collagen deposition.

Update on PARP Inhibitors in Breast Cancer

OPINION STATEMENT

The single agent activity of PARP inhibitors (PARPi) in germline BRCA mutated (gBRCAm) breast and ovarian cancer suggests untapped potential for this new class of drug in breast cancer. The US Food and Drug Administration has approved three PARPi (olaparib, rucaparib, and niraparib) so far to treat certain ovarian cancers, including those with gBRCAm and olaparib for treatment of gBRCAm breast cancers. Several PARPi are now under clinical development for breast cancer in the various treatment settings. Recently, two phase III trials of olaparib (OlympiaD) and talazoparib (EMBRACA) demonstrated 3-month progression-free survival improvement with PARPi compared to physician's choice single agent chemotherapy in metastatic gBRCAm breast cancer. To date, PARPi seems less efficacious in metastatic breast cancer patients than those with BRCA mutated platinum-sensitive recurrent ovarian cancer, perhaps reflecting the biologic heterogeneity and low somatic BRCA mutation rate in breast cancer. The use of PARPi is gradually evolving, including combination strategies with chemotherapy, targeted agents, radiotherapy, or immunotherapy in women with and without gBRCAm. The role of predictive biomarkers, including molecular signatures and homologous recombination repair deficiency scores based on loss of heterozygosity and other structural genomic aberrations, will be crucial to identify a subgroup of patients who may have benefit from PARPi. An improved understanding of the mechanisms underlying PARPi clinical resistance will also be important to enable the development of new approaches to increase efficacy. This is a field rich in opportunity, and the coming years should see a better understanding of which breast cancer patients we should treat with PARPi and where these agents should come in over the course of treatment.

Double-barreled gun: Combination of PARP inhibitor with conventional chemotherapy

DNA repair pathways are evolutionarily conserved molecular mechanisms that maintain the integrity of genomic DNA. In cancer therapies, the integrity and activity of DNA repair pathways predict therapy resistance and disease outcome. Members of the poly (ADP-ribose) polymerase (PARP) family initiate and organize the biologic process of DNA repair, which counteracts many types of chemotherapies. Since the first development in approximately 3 decades ago, PARP inhibitors have greatly changed the concept of cancer therapy, leading to encouraging improvements in tumor suppression and disease outcomes. Here we summaries both pre-clinical and clinical findings of PARP inhibitors applications, particularly for combination therapies.

Poly (ADP-ribose) polymerase inhibitor, an effective radiosensitizer in lung and pancreatic cancers

The development of stereotactic body radiation therapy (SBRT) has revolutionized radiation therapy for lung cancers and is an emerging treatment option for pancreatic cancers. However, there are many questions on how to optimize its use in chemoradiotherapy. The most relevant addition to radiotherapy regimens are inhibitors of DNA repair and DNA damage response pathways. One such class of agents are inhibitors of poly (ADP-ribose) polymerase (PARP). In this study we examined the effects of the PARP inhibitor LT626 in combination with ionizing radiation in lung and pancreatic cancers. Our study demonstrated that combination treatment with LT626 and radiation effectively inhibited growth in lung and pancreatic cancer cell lines, better than individual treatment alone. Combination treatment also increased expression of γH2AX and 53BP1 foci and upregulated expression of phosphorylated ATM, ATR and their respective kinases. Using in vivo lung cancer xenograft models we demonstrated that LT626 functioned as an effective radiosensitizer during fractionated radiation treatment, leading to significant decrease in tumor burden and doubling the median survival compared to control group. Overall our in vitro and in vivo studies showed that PARP inhibitor LT626 acted synergistically with radiation in lung and pancreatic cancers.

Preclinical evaluation of the PARP inhibitor BMN-673 for the treatment of ovarian clear cell cancer

Purpose

To determine if models of ovarian clear cell carcinomas (OCCCs) harbouring defects in homologous recombination (HR) DNA repair of double strand breaks (DSBs) are sensitive to cisplatin and/or PARP inhibition.

Experimental Design

The HR status of 12 OCCC cell lines was determined using RAD51/γH2AX foci formation assays. Sensitivity to cisplatin and the PARP inhibitor BMN-673 was correlated with HR status. BRCA1, BRCA2, MRE11 and PTEN loss of expression was investigated as a potential determinant of BMN-673 sensitivity. A tissue microarray containing 50 consecutive primary OCCC was assessed for PTEN expression using immunohistochemistry.

Results

A subset of OCCC cells displayed reduced RAD51 foci formation in the presence of DNA DSBs, suggestive of HR defects. HR-defective OCCC cells, with the exception of KOC-7c, had higher sensitivity to cisplatin/ BMN-673 than HR-competent OCCC cell lines (Log10 SF50 –9.4 (SD +/− 0.29) vs –8.1 (SD +/− 0.35), mean difference 1.3, p < 0.01). Of the cell lines studied, two, TOV-21G and KOC-7c, showed loss of PTEN expression. In primary OCCCs, loss of PTEN expression was observed in 10% (5/49) of cases.

Conclusions

A subset of OCCC cells are sensitive to PARP inhibition in vitro, which can be predicted by HR defects as defined by γH2AX/RAD51 foci formation. These results provide a rationale for the testing of HR deficiency and PARP inhibitors as a targeted therapy in a subset of OCCCs.

Large intergenic non-coding RNA-ROR reverses gemcitabine-induced autophagy and apoptosis in breast cancer cells

The purpose of this study was to elucidate the potential role of long intergenic non-protein coding RNA, regulator of reprogramming (linc-ROR) in gemcitabine (Gem)-induced autophagy and apoptosis in breast cancer cells. MDA-MB-231 cells were treated with short hairpin RNA (shRNA) to knockdown Linc-ROR expression in the presence of Gem. Gem treatment alone decreased cell survival and increased both apoptosis and autophagy. Gem treatment also increased the expression of LC3-II, Beclin 1, NOTCH1 and Bcl-2, but decreased expression of p62 and p53. Untreated MDA-MB-231 cell lines strongly expressed linc-ROR, but linc-ROR knockdown decreased cell viability and expression of p62 and p53 while increasing apoptosis. Linc-ROR knockdown also increased LC3-II/β-actin, Beclin 1, NOTCH1, and Bcl-2 expression, as well as the number of autophagic vesicles in MDA-MB-231 cells. Linc-ROR negatively regulated miR-34a expression by inhibiting histone H3 acetylation in the miR-34a promoter. We conclude that linc-ROR suppresses Gem-induced autophagy and apoptosis in breast cancer cells by silencing miR-34a expression.

Neoadjuvant treatments in triple-negative breast cancer patients: where we are now and where we are going

Triple-negative breast cancer (TNBC) remains the poorest-prognosis breast cancer (BC) subtype. Gene expression profiling has identified at least six different triple-negative subtypes with different biology and sensitivity to therapies. The heterogeneous nature of TN tumors may justify the difficulty in treating this BC subtype. Several targeted agents have been investigated in clinical trials without demonstrating a clear survival benefit. Therefore, systemic chemotherapy remains the cornerstone of current clinical practice. Improving the knowledge of tumor biology is mandatory for patient management. In stages II and III, neoadjuvant systemic treatment is an effective option of care. The achievement of a pathological complete response represents an optimal surrogate for survival outcome as well as a test for tumor drug sensitivity. In this review, we provide a brief description of the main predictive biomarkers for tumor response to systemic treatment. Moreover, we review the treatment strategies investigated for TNBCs in neoadjuvant settings focusing on experimental drugs such as immunotherapy and poly [ADP-ribose] polymerase inhibitors that hold promise in the treatment of this aggressive disease. Therefore, the management of TNBC represents an urgent, current, unmet need in daily clinical practice. A key recommendation is to design biology-driven clinical trials wherein TNBC patients may be treated on the basis of tumor molecular profile.

Analogs of the novel phytohormone, strigolactone, trigger apoptosis and synergize with PARP inhibitors by inducing DNA damage and inhibiting DNA repair

Strigolactones are a novel class of plant hormones produced in roots that regulate shoot and root development. We previously reported that strigolactone analogs (SLs) induce G2/M cell cycle arrest and apoptosis in a variety of human cancer cells and inhibit tumor growth of human breast cancer xenografts in mice. SLs had no significant influences on non-transformed cells. Here we report for the first time that SLs induce DNA damage in the form of DNA double-strand breaks (DSBs) and activate the DNA damage response signaling by inducing phosphorylation of ATM, ATR and DNA-PKcs and co-localization of the DNA damage signaling protein, 53BP1, with γH2AX nuclear foci. We further report that in addition to DSBs induction, SLs simultaneously impair DSBs repair, mostly homology-directed repair (HDR) and to a lesser extent non-homologous end joining (NHEJ). In response to SLs, RAD51, the homologous DSB repair protein, is ubiquitinated and targeted for proteasomal degradation and it fails to co-localize with γH2AX foci. Interestingly, SLs synergize with DNA damaging agents-based therapeutics. The combination of PARP inhibitors and SLs showed an especially potent synergy, but only in BRCA1-proficient cells. No synergy was observed between SLs and PARP inhibitors in BRCA1-deficient cells, supporting a role for SLs in HDR impairment. Together, our data suggest that SLs increase genome instability and cell death by a unique mechanism of inducing DNA damage and inhibiting DNA repair.

Triple negative breast cancer in Asia: An insider's view

While tremendous improvement has been made for the treatment of breast cancers, the treatment of triple negative breast cancer (TNBC) still remains a challenge due to its aggressive characteristics and limited treatment options. Most of the studies on TNBC were conducted in Western population and TNBC is reported to be more frequent in the African women. This review encapsulates the studies conducted on TNBC patients in Asian population and elucidates the similarities and differences between these two regions. The current treatment of TNBC includes surgery, radiotherapy and chemotherapy. In addition to the current chemotherapies, which mainly include cytotoxic agents, such as taxanes and anthracyclines, many clinical trials are investigating the potential use of other chemotherapy drugs, targeted therapeutics and combinational therapies to treat TNBC. Moreover, this review also integrates the studies involving novel markers, which will help us to dissect the pathologic process of TNBC and in turn facilitate the development of better treatment strategies to combat TNBC.