Emerging therapeutic modalities of PARP inhibitors in breast cancer

Maintained complete response to talazoparib in a BRCA-2 mutated metastatic luminal breast cancer: case report and review of literature

PARP inhibitors are progressively becoming a part of our therapeutic arsenal against BRCA-defective tumors, because of their capacity to induce synthetic lethality in cells with a deficiency in the homologous recombination repair system. Olaparib and talazoparib have been approved for metastatic breast cancer in carriers of germline BRCA mutations, which are found in approximately 6% of patients with breast cancer. We report the case of a patient with metastatic breast cancer, carrier of a germline mutation in BRCA2, with a complete response to first-line treatment with talazoparib, maintained after 6 years. To the best of our knowledge, this is the longest response reported with a PARP inhibitor in a BRCA-mutated tumor. We have made a review of literature, regarding the rationale for PARP inhibitors in carriers of BRCA mutations and their clinical relevance in the management of advanced breast cancer, as well as their emerging role in early stage disease, alone and in combination with other systemic therapies.

Synthesis, biological evaluation, and molecular modeling studies of new benzoxazole derivatives as PARP-2 inhibitors targeting breast cancer

Many benzoxazole-based and similar scaffolds were reported to have wide-range of anticancer activities. In this study, four series of benzoxazole derivatives were designed by combining benzoxazole scaffold with different amines via a reversed phenyl amide linker to produce the compounds of series A, B and C. A fourth new hybrid of benzoxazole with 1,2,3 triazole ring (series D) was also designed. The designed compounds were synthesized and screened for their anti-breast cancer activity against MDA-MB-231 and MCF-7 cell lines using MTT assay. The most potent cytotoxic compounds; 11–14, 21, 22, 25–27 were further evaluated for their in vitro PARP-2 enzyme inhibition. Compounds 12 and 27 proved to be the most active PARP-2 inhibitors with IC₅₀ values of 0.07 and 0.057 µM, respectively. Compounds 12 and 27 caused cell cycle arrest in mutant MCF-7 cell line at G2/M and G1/S phase, respectively and they possessed significant apoptosis-promoting activity. Docking results of compounds 12 and 27 into PARP-2 pocket demonstrated binding interactions comparable to those of olaparib. Their predicted pharmacokinetic parameters and oral bioavailability appeared to be appropriate. Collectively, it could be concluded that compounds 12 and 27 are promising anti-breast cancer agents that act as PARP-2 inhibitors with potent apoptotic activity.

Molecular perspective on targeted therapy in breast cancer: a review of current status

Breast cancer is categorized at the molecular level according to the status of certain hormone and growth factor receptors, and this classification forms the basis of current diagnosis and treatment. The development of resistance to treatment and recurrence of the disease have led researchers to develop new therapies. In recent years, most of the research in the field of oncology has focused on the development of targeted therapies, which are treatment methods developed directly against molecular abnormalities. Promising advances have been made in clinical trials investigating the effect of these new treatment modalities and their combinations with existing therapeutic treatments in the treatment of breast cancer. Monoclonal antibodies, tyrosine kinase inhibitors, antibody–drug conjugates, PI3K/Akt/mTOR pathway inhibitors, cyclin-dependent kinase 4/6 inhibitors, anti-angiogenic drugs, PARP inhibitors are among the targeted therapies used in breast cancer treatment. In this review, we aim to present a molecular view of recently approved target agents used in breast cancer.

Expanding the Use of PARP Inhibitors as Monotherapy and in Combination in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, and is known to be associated with a poor prognosis and limited therapeutic options. Poly (ADP-ribose) polymerase inhibitors (PARPi) are targeted therapeutics that have demonstrated efficacy as monotherapy in metastatic BRCA-mutant (BRCAMUT) TNBC patients. Improved efficacy of PARPi has been demonstrated in BRCAMUT breast cancer patients who have either received fewer lines of chemotherapy or in chemotherapy-naïve patients in the metastatic, adjuvant, and neoadjuvant settings. Moreover, recent trials in smaller cohorts have identified anti-tumor activity of PARPi in TNBC patients, regardless of BRCA-mutation status. While there have been concerns regarding the efficacy and toxicity of the use of PARPi in combination with chemotherapy, these challenges can be mitigated with careful attention to PARPi dosing strategies. To better identify a patient subpopulation that will best respond to PARPi, several genomic biomarkers of homologous recombination deficiency have been tested. However, gene expression signatures associated with PARPi response can integrate different pathways in addition to homologous recombination deficiency and can be implemented in the clinic more readily. Taken together, PARPi have great potential for use in TNBC patients beyond BRCAMUT status, both as a single-agent and in combination.

A self-amplified nanocatalytic system for achieving "1 + 1 + 1 > 3" chemodynamic therapy on triple negative breast cancer

BACKGROUND

Chemodynamic therapy (CDT), employing Fenton or Fenton-like catalysts to convert hydrogen peroxide (H₂O₂) into toxic hydroxyl radicals (·OH) to kill cancer cells, holds great promise in tumor therapy due to its high selectivity. However, the therapeutic effect is significantly limited by insufficient intracellular H₂O₂ level in tumor cells. Fortunately, β-Lapachone (Lapa) that can exert H₂O₂-supplementing functionality under the catalysis of nicotinamide adenine dinucleotide (phosphate) NAD(P)H: quinone oxidoreductase-1 (NQO1) enzyme offers a new idea to solve this problem. However, extensive DNA damage caused by high levels of reactive oxygen species can trigger the "hyperactivation" of poly(ADP-ribose) polymerase (PARP), which results in the severe interruption of H₂O₂ supply and further the reduced efficacy of CDT. Herein, we report a self-amplified nanocatalytic system (ZIF67/Ola/Lapa) to co-deliver the PARP inhibitor Olaparib (Ola) and NQO1-bioactivatable drug Lapa for sustainable H₂O₂ production and augmented CDT ("1 + 1 + 1 > 3").

RESULTS

The effective inhibition of PARP by Ola can synergize Lapa to enhance H₂O₂ formation due to the continuous NQO1 redox cycling. In turn, the high levels of H₂O₂ further react with Co²⁺ to produce the highly toxic ·OH by Fenton-like reaction, dramatically improving CDT. Both in vitro and in vivo studies demonstrate the excellent antitumor activity of ZIF67/Ola/Lapa in NQO1 overexpressed MDA-MB-231 tumor cells. Importantly, the nanocomposite presents minimal systemic toxicity in normal tissues due to the low NQO1 expression.

CONCLUSIONS

This design of nanocatalytic system offers a new paradigm for combing PARP inhibitor, NQO1-bioactivatable drug and Fenton-reagents to obtain sustained H₂O₂ generation for tumor-specific self-amplified CDT.

Targeting Different Pathways Using Novel Combination Therapy in Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer accounting for 15-20% of cases and is defined by the lack of hormonal receptors viz., estrogen receptor (ER), progesterone receptor (PR) and expression of human epidermal growth receptor 2 (HER2). Treatment of TNBC is more challenging than other subtypes of breast cancer due to the lack of markers for the molecularly targeted therapies (ER, PR, and HER-2/ Neu), the conventional chemotherapeutic agents are still the mainstay of the therapeutic protocols of its patients. Despite, TNBC being more chemo-responsive than other subtypes, unfortunately, the initial good response to the chemotherapy eventually turns into a refractory drug-resistance. Using a monotherapy for the treatment of cancer, especially high-grade tumors like TNBC, is mostly worthless due to the inherent genetic instability of tumor cells to develop intrinsic and acquired resistance. Thus, a cocktail of two or more drugs with different mechanisms of action is more effective and could successfully control the disease. Furthermore, combination therapy reveals more, or at least the same, effectiveness with lower doses of every single agent and decreases the likelihood of chemoresistance. Herein, we shed light on the novel combinatorial approaches targeting PARP, EGFR, PI3K pathway, AR, and wnt signaling, HDAC, MEK pathway for efficient treatment of high-grade tumors like TNBC and decreasing the onset of resistance.

Poly Lactic-Co-Glycolic Acid- (PLGA-) Loaded Nanoformulation of Cisplatin as a Therapeutic Approach for Breast Cancers

Despite recent advancements in cisplatin (cis-diamminedichloroplatinum II) and other platinum-based chemotherapeutic drugs for treating solid tumors, their uses are limited by either in terms of toxicity and/or acquired drug resistance. These side effects have a dangerous problem with higher dose for severe patients. To overcome the low therapeutic ratio of the free drug, a polymeric nanoparticle drug delivery system has been explored promoting delivery of cisplatin to tumors. Recently, the applications of nanoparticles (NPs) have been underlined for encouraging the effects of chemotherapeutic drugs in cancerous cells. The intention of this project is to assess the potential of poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) for enhancing the effects of anticancer drug cisplatin. For the purpose, we have synthesized PLGA-cisplatin nanoparticles for increasing its bioavailability and studied the comparative cytotoxicity of free cisplatin and PLGA-cisplatin against MCF-7 cancer cell lines and HEK-293 normal cell lines. We have also analyzed the hallmarks of PLGA-cisplatin-induced apoptosis. The outcomes of this study may provide the possibility of delivery of anticancer drug to their specific site, which could minimize toxicity and optimize the drug efficacy.

BKM120 sensitizes BRCA-proficient triple negative breast cancer cells to olaparib through regulating FOXM1 and Exo1 expression

Poly (ADP-ribose) polymerase (PARP) inhibitors offer a significant clinical benefit for triple-negative breast cancers (TNBCs) with BRCA1/2 mutation. However, the narrow clinical indication limits the development of PARP inhibitors. Phosphoinositide 3-kinase (PI3K) inhibition sensitizes BRCA-proficient TNBC to PARP inhibition, which broadens the indication of PARP inhibitors. Previously researches have reported that PI3K inhibition induced the defect of homologous recombination (HR) mediated repair by downregulating the expression of BRCA1/2 and Rad51. However, the mechanism for their synergistic effects in the treatment of TNBC is still unclear. Herein, we focused on DNA damage, DNA single-strand breaks (SSBs) repair and DNA double-strand breaks (DSBs) repair three aspects to investigate the mechanism of dual PI3K and PARP inhibition in DNA damage response. We found that dual PI3K and PARP inhibition with BKM120 and olaparib significantly reduced the proliferation of BRCA-proficient TNBC cell lines MDA-MB-231 and MDA231-LM2. BKM120 increased cellular ROS to cause DNA oxidative damage. Olaparib resulted in concomitant gain of PARP1, forkhead box M1 (FOXM1) and Exonuclease 1 (Exo1) while inhibited the activity of PARP. BKM120 downregulated the expression of PARP1 and PARP2 to assist olaparib in blocking PARP mediated repair of DNA SSBs. Meanwhile, BKM120 inhibited the expression of BRAC1/2 and Rad51/52 to block HR mediated repair through the PI3K/Akt/NFκB/c-Myc signaling pathway and PI3K/Akt/ FOXM1/Exo1 signaling pathway. BKM120 induced HR deficiency expanded the application of olaparib to HR proficient TNBCs. Our findings proved that PI3K inhibition impaired the repair of both DNA SSBs and DNA DSBs. FOXM1 and Exo1 are novel therapeutic targets that serves important roles in DNA damage response.

Targeting RECQL5 Functions, by a Small Molecule, Selectively Kills Breast Cancer in Vitro and in Vivo

Clinical and preclinical data reveal that RECQL5 protein overexpression in breast cancer was strongly correlated with poor prognosis, survival, and therapeutic resistance. In the current investigation, we report design, synthesis, and specificity of a small molecule, 4a, which can preferentially kill RECQL5-expressing breast cancers but not RECQL5 knockout. Our stringent analysis showed that compound 4a specifically sensitizes RECQL5-expressing cancers, while it did not have any effect on other members of DNA RECQL-helicases. Integrated approaches of organic synthesis, biochemical, in silico molecular simulation, knockouts, functional mutation, and rescue experiments showed that 4a potently inhibits RECQL5-helicase activity and stabilizes RECQL5-RAD51 physical interaction, leading to impaired HRR and preferential killing of RECQL5-expressing breast cancer. Moreover, 4a treatment led to the efficient sensitization of cisplatin-resistant breast cancers but not normal mammary epithelial cells. Pharmacologically, compound 4a was orally effective in reducing the growth of RECQL5-expressing breast tumors (human xenograft) in NUDE-mice with no appreciable toxicity to the vital organs.

Sustained, local delivery of the PARP inhibitor talazoparib prevents the development of mammary gland hyperplasia in Brca1-deficient mice

Mutations in BRCA genes are the leading cause of hereditary breast cancer. Current options to prevent cancer in these high-risk patients, such as anti-estrogen drugs and radical mastectomy, are limited by lack of efficacy, undesirable toxicities, or physical and emotional challenges. We have previously shown that PARP inhibitors can significantly delay tumor development in BRCA1-deficient mice. Here, we fabricated the PARP inhibitor talazoparib (TLZ) into spacer implants (InCeT-TLZ) for localized and sustained delivery. We hypothesized that this novel formulation will provide an effective chemopreventive strategy with minimal toxicity. TLZ was released gradually over 30 days as implants degraded. InCeT-TLZ significantly decreased proliferation and increased DNA damage in the mammary glands of BRCA1-deficient mice. Notably, the number of mice that developed hyperplasia in the mammary glands was significantly lower with InCeT-TLZ treatment compared to the control group. Meanwhile, InCeT-TLZ was also better tolerated than oral TLZ, without loss of body weight or anemia. This study provides proof of concept for a novel and safe chemopreventive strategy using localized delivery of a PARP inhibitor for high-risk individuals. Future studies will directly evaluate the effects of InCeT-TLZ for preventing tumor development.

Triple negative breast cancer in the era of miRNA

The objective of this review is to elucidate the role of miRNAs in triple negative breast cancer (TNBC). To achieve our goal, we searched databases such as PubMed, ScienceDirect, Springer, Web of Science and Scopus. We retrieved up to 1233 articles, based a rigorous selection criterion, only 197 articles were extensively reviewed. We selected articles only addressing TNBC, but not other types of breast cancer, with the employed approach being miRNA analysis and/or profiling. Our extensive review resulted in grouping of miRNAs into categories in which specific members of miRNAs have roles in specific mechanism in TNBC i.e., carcinogenesis, invasion, metastasis, apoptosis, diagnosis, prognosis, and treatment. TNBC is an aggressive subtype of breast cancer; therefore, different approaches for accurate diagnosis, prognosis and treatment are needed. In this review we summarize the up-to-date miRNA profiling, prognostic, and therapeutic findings that add to the route of controlling TNBC.

Synthesis of Some Benzimidazole-derived Molecules and their Effects on PARP-1 Activity and MDA-MB-231, MDA-MB-436, MDA-MB-468 Breast Cancer Cell Viability

Background:

Poly (ADP-ribosyl) polymerase-1 (PARP-1) inhibitors are compounds that are used to treat cancers, which are defective in DNA-repair and DNA Damage-Response (DDR) pathways.

Objective:

In this study, a series of potential PARP-1 inhibitor substituted (piperazine-1-carbonyl)phenyl)-1Hbenzo[ d]imidazole-4-carboxamide compounds were synthesised and tested for their PARP-1 inhibitory and anticancer activities.

Methods:

Compounds were tested by cell-free colorimetric PARP-1 activity and MTT assay in MDA-MB-231, MDA-MB-436, MDA-MB-468 breast cancer, and L929 fibroblast cell lines.

Results:

Our results showed that compound 6a inhibited viability in MDA-MB-231 and MDA-MB-468 cells whereas 8a inhibited viability in MDA-MB-468 cells. Compound 6b significantly inhibited cell viability in tested cancer cells. However, 6b exhibited toxicity in L929 cells, whereas 6a and 8a were found to be non-toxic for L929 cells. Compounds 6a, 6b and 8a exhibited significant inhibition of PARP-1 activity.

Conclusion:

These three compounds exhibited PARP-1 inhibitory activities and anticancer effects on breast cancer cells, and further research will enlighten the underlying mechanisms of their effects.

Poly (ADP-ribose) Polymerase Inhibition in Patients with Breast Cancer and BRCA 1 and 2 Mutations

The poly-(ADP-ribose) polymerase (PARP) inhibitors olaparib and talazoparib, have recently been approved for use in patients with metastatic breast cancer (BC) and germline BRCA 1 or 2 mutations due to improved progression-free survival compared to chemotherapy. An increasing number of clinical trials are evaluating the role of PARP inhibitors (PARPi) in BC, alone and in combination with other therapies (including immunotherapy), as well as in earlier stages of the disease. This review describes the unique mechanism of action of these drugs and puts into clinical context the results of pivotal clinical trials. We also discuss the future development of PARPi in BC, their potential combination with other strategies, including chemotherapy and immune-checkpoint inhibitors, and the impact of these treatments in current genetic counselling.

The Premature Senescence in Breast Cancer Treatment Strategy

Cellular senescence is a permanent blockade of cell proliferation. In response to therapy-induced stress, cancer cells undergo apoptosis or premature senescence. In apoptosis-resistant cancer cells or at lower doses of anticancer drugs, therapy-induced stress leads to premature senescence. The role of this senescence in cancer treatment is discussable. First of all, the senescent cells lose the ability to proliferate, migrate, and invade. In addition, the senescent cells secrete a set of proteins (inflammatory cytokines, chemokines, growth factors) known as the senescence-associated secretory phenotype (SASP), which influences non-senescent normal cells and non-senescent cancer cells in the tumor microenvironment and triggers tumor promotion and recurrence. Recently, many studies have examined senescence induction through breast cancer therapy and potentially using this phenomenon to treat this cancer. This review summarizes the recent in vitro, in vivo, and clinical studies investigating senescence in breast cancer treatments. Senescence inductors, senolytics, as well as their action mechanism are discussed herein. Potential SASP-modulating treatment strategies are also described.

PARP goes the weasel! Emerging role of PARP inhibitors in acute leukemias

Poly (ADP-ribose) polymerase (PARP) inhibitors, which induce synthetic lethality of BRCA mutant breast and ovarian cancers, are now under active exploration for treatment of acute leukemias, specifically acute myeloid leukemia (AML). Experimental data has revealed that DNA repair deficiencies similar to those found in BRCA mutant solid tumors function in malignant hematopoietic cells to enhance cell survival and promote therapy resistance. Preclinical studies have demonstrated that inhibition of PARP with a variety of agents can dramatically enhance the efficacy of other therapeutic approaches including cytotoxic and epigenetic chemotherapy, small molecule inhibitors (IDH and FLT3 inhibitors) and antibody drug conjugates. This has led to early stage clinical trials of multiple PARP inhibitors (PARPi) for AML patients. Despite small patient numbers, evidence of modest clinical efficacy and tolerability in combinatorial regimens support the further development of PARP inhibition as a novel therapeutic strategy for AML, particularly in select molecular subsets (MLL rearranged, FLT3 and IDH1 mutant disease.

Combination of Withaferin-A and CAPE Provides Superior Anticancer Potency: Bioinformatics and Experimental Evidence to Their Molecular Targets and Mechanism of Action

We have earlier reported anticancer activity in Withaferin A (Wi-A), a withanolide derived from Ashwagandha (Withania somnifera) and caffeic acid phenethyl ester (CAPE), an active compound from New Zealand honeybee propolis. Whereas Wi-A was cytotoxic to both cancer and normal cells, CAPE has been shown to cause selective death of cancer cells. In the present study, we investigated the efficacy of Wi-A, CAPE, and their combination to ovarian and cervical cancer cells. Both Wi-A and CAPE were seen to activate tumor suppressor protein p53 by downregulation of mortalin and abrogation of its interactions with p53. Downregulation of mortalin translated to compromised mitochondria integrity and function that affected poly ADP-ribose polymerase1 (PARP1); a key regulator of DNA repair and protein-target for Olaparib, drugs clinically used for treatment of breast, ovarian and cervical cancers)-mediated DNA repair yielding growth arrest or apoptosis. Furthermore, we also compared the docking capability of Wi-A and CAPE to PARP1 and found that both of these could bind to the catalytic domain of PARP1, similar to Olaparib. We provide experimental evidences that (i) Wi-A and CAPE cause inactivation of PARP1-mediated DNA repair leading to accumulation of DNA damage and activation of apoptosis signaling by multiple ways, and (ii) a combination of Wi-A and CAPE offers selective toxicity and better potency to cancer cells.

Talazoparib nanoparticles for overcoming multidrug resistance in triple-negative breast cancer

Herein, we investigated efflux pumps-mediated talazoparib-resistance in the treatment of triple-negative breast cancer (TNBC). Furthermore, we produced a novel talazoparib-solid lipid nanoparticles (SLNs) and then explored in vitro therapeutic efficacy of talazoparib-SLNs to overcome talazoparib-resistance in TNBC cells. Talazoparib-SLNs formulation was produced and then characterized. Calcein and Rho-123 were used to analyze the functional activity of drug efflux pumps in these cells. Additionally, RT-PCR, western blot and immunofluorescence analysis were used to detect the messenger RNA, and protein expression level, and cellular localization of the multidrug resistance (MDR1), breast cancer resistance protein (BCRP), and MRP1. We found that talazoparib efflux was mediated by BCRP and MRP1 pumps in TNBC cells. Talazoparib-SLNs could significantly enhance therapeutic efficacy of talazoparib. Furthermore, talazoparib-SLNs were more effective in the suppression of MDR1, BCRP, and MRP1 gene and protein expression levels than talazoparib. Consequently, this study suggests that talazoparib-SLNs formulation represents a promising therapeutic carrier to reverse MDR-mediated resistance in TNBC.

Low-Dose and Long-Term Olaparib Treatment Sensitizes MDA-MB-231 and SUM1315 Triple-Negative Breast Cancers Spheroids to Fractioned Radiotherapy

The Triple-Negative Breast Cancer subtype (TNBC) is particularly aggressive and heterogeneous. Thus, Poly-ADP-Ribose Polymerase inhibitors were developed to improve the prognosis of patients and treatment protocols are still being evaluated. In this context, we modelized the efficacy of Olaparib (i.e., 5 and 50 µM), combined with fractioned irradiation (i.e., 5 × 2 Gy) on two aggressive TNBC cell lines MDA-MB-231 (BRCAness) and SUM1315 (BRCA1-mutated). In 2D cell culture and for both models, the clonogenicity drop was 95-fold higher after 5 µM Olaparib and 10 Gy irradiation than Olaparib treatment alone and was only 2-fold higher after 50 µM and 10 Gy. Similar responses were obtained on TNBC tumor-like spheroid models after 10 days of co-treatment. Indeed, the ratio of metabolic activity decrease was of 1.2 for SUM1315 and 3.3 for MDA-MB-231 after 5 µM and 10 Gy and of only 0.9 (both models) after 50 µM and 10 Gy. MDA-MB-231, exhibiting a strong proliferation profile and an overexpression of AURKA, was more sensitive to the co-treatment than SUM1315 cell line, with a stem-cell like phenotype. These results suggest that, with the studied models, the potentiation of Olaparib treatment could be reached with low-dose and long-term exposure combined with fractioned irradiation.

A nano-liposome formulation of the PARP inhibitor Talazoparib enhances treatment efficacy and modulates immune cell populations in mammary tumors of BRCA-deficient mice

Two recently approved PARP inhibitors provide an important new therapeutic option for patients with BRCA-mutated metastatic breast cancer. PARP inhibitors significantly prolong progression-free survival in patients, but conventional oral delivery of PARP inhibitors is hindered by limited bioavailability and off-target toxicities, thus compromising the therapeutic benefits and quality of life for patients. Here, we developed a new delivery system, in which the PARP inhibitor Talazoparib is encapsulated in the bilayer of a nano-liposome, to overcome these limitations.

Methods: Nano-Talazoparib (NanoTLZ) was characterized both in vitro and in vivo. The therapeutic efficacy and toxicity of Nano-Talazoparib (NanoTLZ) were evaluated in BRCA-deficient mice. The regulation of NanoTLZ on gene transcription and immunomodulation were further investigated in spontaneous BRCA-deficient tumors.

Results: NanoTLZ significantly (p<0.05) prolonged the overall survival of BRCA-deficient mice compared to all of the other experimental groups, including saline control, empty nanoparticles, and free Talazoparib groups (oral and i.v.). Moreover, NanoTLZ was better tolerated than treatment with free Talazoparib, with no significant weight lost or alopecia as was observed with the free drug. After 5 doses, NanoTLZ altered the expression of over 140 genes and induced DNA damage, cell cycle arrest and inhibition of cell proliferation in the tumor. In addition, NanoTLZ favorably modulated immune cell populations in vivo and significantly (p<0.05) decreased the percentage of myeloid derived suppressor cells in both the tumor and spleen compared to control groups.

Conclusions: Our results demonstrate that delivering nanoformulated Talazoparib not only enhances treatment efficacy but also reduces off-target toxicities in BRCA-deficient mice; the same potential is predicted for patients with BRCA-deficient breast cancer.

Facile synthesis of aquo-cisplatin arsenite multidrug nanocomposites for overcoming drug resistance and efficient combination therapy

Cisplatin (CDDP) and arsenic trioxide (ATO), two representative inorganic anticancer drugs, have been successful in the treatment against several kinds of malignancies. However, combination therapy with these two drugs in clinical application suffers from poor pharmacokinetics, serious side effects, and drug resistance of the tumor. Herein, we report a carrier-free aquo-cisplatin arsenite multidrug nanocomposite loaded with cisplatin and arsenic trioxide prodrugs simultaneously. This nanocomposite achieves a high loading capacity and pH-dependent controlled release of the drugs. Because of these features, this nanocomposite shows better in vitro toxicity against various carcinoma cell lines than either the single drug or free drug combination, promotes the synergistic effect of cisplatin and arsenic trioxide, and significantly inhibits the growth of tumors in vivo. Furthermore, cisplatin and arsenic trioxide in this nanocomposite can realize a coordination of both enhanced DNA damage and DNA repair interference within cisplatin-resistant cells, which results in overcoming the drug resistance effectively. Gene expression profiles demonstrate the reduced expression of proto-oncogenes and DNA damage repair related genes MYC, MET, and MSH2, along with the increase of tumor suppressor genes PTEN, VHL, and FAS after the nanocomposite treatment. This type of multidrug nanocomposite offers an alternative and promising strategy for combination therapy and overcoming drug resistance.

CDCA7 and HELLS mutations undermine nonhomologous end joining in centromeric instability syndrome

Mutations in CDCA7 and HELLS that respectively encode a CXXC-type zinc finger protein and an SNF2 family chromatin remodeler cause immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome types 3 and 4. Here, we demonstrate that the classical nonhomologous end joining (C-NHEJ) proteins Ku80 and Ku70, as well as HELLS, coimmunoprecipitated with CDCA7. The coimmunoprecipitation of the repair proteins was sensitive to nuclease treatment and an ICF3 mutation in CDCA7 that impairs its chromatin binding. The functional importance of these interactions was strongly suggested by the compromised C-NHEJ activity and significant delay in Ku80 accumulation at DNA damage sites in CDCA7- and HELLS-deficient HEK293 cells. Consistent with the repair defect, these cells displayed increased apoptosis, abnormal chromosome segregation, aneuploidy, centrosome amplification, and significant accumulation of γH2AX signals. Although less prominent, cells with mutations in the other ICF genes DNMT3B and ZBTB24 (responsible for ICF types 1 and 2, respectively) showed similar defects. Importantly, lymphoblastoid cells from ICF patients shared the same changes detected in the mutant HEK293 cells to varying degrees. Although the C-NHEJ defect alone did not cause CG hypomethylation, CDCA7 and HELLS are involved in maintaining CG methylation at centromeric and pericentromeric repeats. The defect in C-NHEJ may account for some common features of ICF cells, including centromeric instability, abnormal chromosome segregation, and apoptosis.