BRCA Gene Mutations and Poly(ADP-Ribose) Polymerase Inhibitors in Triple-Negative Breast Cancer

Fertility Preservation in BRCA1/2 Germline Mutation Carriers: An Overview

BRCA1 and BRCA2 mutations are responsible for a higher incidence of breast and ovarian cancer (from 55% up to 70% vs. 12% in the general population). If their functions have been widely investigated in the onset of these malignancies, still little is known about their role in fertility impairment. Cancer patients treated with antineoplastic drugs can be susceptible to their gonadotoxicity and, in women, some of them can induce apoptotic program in premature ovarian follicles, progressive depletion of ovarian reserve and, consequently, cancer treatment-related infertility (CTRI). BRCA variants seem to be associated with early infertility, thus accelerating treatment impairment of ovaries and making women face the concrete possibility of an early pregnancy. In this regard, fertility preservation (FP) procedures should be discussed in oncofertility counseling-from the first line of prevention with risk-reducing salpingo-oophorectomy (RRSO) to the new experimental ovarian stem cells (OSCs) model as a new way to obtain in vitro-differentiated oocytes, several techniques may represent a valid option to BRCA-mutated patients. In this review, we revisit knowledge about BRCA involvement in lower fertility, pregnancy feasibility, and the fertility preservation (FP) options available.

Veliparib for the treatment of solid malignancies

OBJECTIVE

Veliparib is a poly adenosine diphosphate ribose polymerase (PARP) -1 and -2 inhibitor with chemo-sensitizing and anticancer activities that has shown promising results in early-phase trials. The aim of this comprehensive review is to summarise the profile of veliparib and to provide an overview of its early clinical investigations.

DATA SOURCES

Details of all the completed trials evaluating the profile of veliparib were identified from ClinicalTrials.gov with the relevant keywords. Furthermore, databases such as Google Scholar and PubMed were searched using the National Clinical Trial (NCT) number to retrieve publications of results not listed in the trial registry.

DATA SUMMARY

A total of 25 completed clinical trials indicating the use of veliparib in solid malignancies were identified. The results showed that veliparib is well tolerated, both as a single agent and in combination with standard chemotherapy doses. Being a broad-spectrum potentiator of DNA-damaging agents and radiation, it has shown to improve the clinical outcomes, particularly in solid tumors like ovarian cancer, breast cancer and lung cancer.

CONCLUSIONS

The results from clinical trials indicate that veliparib can be an excellent therapeutic strategy for BRCA mutation associated cancers and tumors bearing deficiencies in the HR pathway as well. Further studies establishing the dosing, sequence of therapy, extended use and compatibility with various anti-cancer drugs are warranted to define its exact role in cancer therapy.

DNA methylation and breast cancer: A way forward (Review)

The current management of breast cancer (BC) lacks specific non‑invasive biomarkers able to provide an early diagnosis of the disease. Epigenetic‑sensitive signatures are influenced by environmental exposures and are mediated by direct molecular mechanisms, mainly guided by DNA methylation, which regulate the interplay between genetic and non‑genetic risk factors during cancerogenesis. The inactivation of tumor suppressor genes due to promoter hypermethylation is an early event in carcinogenesis. Of note, targeted tumor suppressor genes are frequently hypermethylated in patient‑derived BC tissues and peripheral blood biospecimens. In addition, epigenetic alterations in triple‑negative BC, as the most aggressive subtype, have been identified. Thus, detecting both targeted and genome‑wide DNA methylation changes through liquid‑based assays appears to be a useful clinical strategy for early detection, more accurate risk stratification and a personalized prediction of therapeutic response in patients with BC. Of note, the DNA methylation profile may be mapped by isolating the circulating tumor DNA from the plasma as a more accessible biospecimen. Furthermore, the sensitivity to treatment with chemotherapy, hormones and immunotherapy may be altered by gene‑specific DNA methylation, suggesting novel potential drug targets. Recently, the use of epigenetic drugs administered alone and/or with anticancer therapies has led to remarkable results, particularly in patients with BC resistant to anticancer treatment. The aim of the present review was to provide an update on DNA methylation changes that are potentially involved in BC development and their putative clinical utility in the fields of diagnosis, prognosis and therapy.

Genetic variants of BRCA1 and BRCA2 genes in cats with mammary gland carcinoma

Mammary tumours are the first and third most incident neoplasm in women and cats, respectively. Approximately 85% of feline mammary gland tumours are malignant and aggressive, especially the triple-negative and HER-2⁺ molecular subtypes. Triple-negative basal-like feline mammary carcinomas (FMCs) are considered suitable models due to the clinical and morphological similarities with human basal-like triple-negative breast cancer (TNBC). In women, TNBC has a poor prognosis and is often associated with mutations in the tumour suppressor genes BRCA1 and BRCA2. In light of this, the aim of the present investigation was to screen somatic and germline variants of BRCA1 and BRCA2 in nine female cats bearing FMCs. Matched whole blood and FMC samples were obtained for genetic analysis. Additional tumour samples were obtained for histopathological and immunohistochemical evaluation. Genomic DNA was isolated and 27 exonic regions of BRCA1 and BRCA2 genes were amplified and screened by next-generation sequencing. A somatic variant with high functional impact was found in exon 11 of BRCA2 at a frequency of 4.34% in one FMC-bearing cat. Four germline variants with moderate impact were detected in three of the nine FMC-bearing cats and were restricted to exon 9 of BRCA1. It is concluded that the germline genetic variants found in one-third of FMC-bearing animals might be associated with a higher risk of hereditary mammary carcinogenesis.

Small-Molecule Drug Discovery in Triple Negative Breast Cancer: Current Situation and Future Directions

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, but an effective targeted therapy has not been well-established so far. Considering the lack of effective targets, where do we go next in the current TNBC drug development? A promising intervention for TNBC might lie in de novo small-molecule drugs that precisely target different molecular characteristics of TNBC. However, an ideal single-target drug discovery still faces a huge challenge. Alternatively, other new emerging strategies, such as dual-target drug, drug repurposing, and combination strategies, may provide new insight into the improvement of TNBC therapeutics. In this review, we focus on summarizing the current situation of a series of candidate small-molecule drugs in TNBC therapy, including single-target drugs, dual-target drugs, as well as drug repurposing and combination strategies that will together shed new light on the future directions targeting TNBC vulnerabilities with small-molecule drugs for future therapeutic purposes.

Triple‑negative breast cancer therapy: Current and future perspectives (Review)

Triple-negative breast cancer (TNBC) accounts for 10-15% of all breast cancer cases. TNBCs lack estrogen and progesterone receptors and express low levels of HER2, and therefore do not respond to hormonal or anti-HER2 therapies. TNBC is a particularly aggressive form of breast cancer that generally displays poorer prognosis compared to other breast cancer subtypes. TNBC is chemotherapy sensitive, and this treatment remains the standard of care despite its limited benefit. Recent advances with novel agents have been made for specific subgroups with PD-L1⁺ tumors or germline Brca-mutated tumors. However, only a fraction of these patients responds to immune checkpoint or PARP inhibitors and even those who do respond often develop resistance and relapse. Various new agents and combination strategies have been explored to further understand molecular and immunological aspects of TNBC. In this review, we discuss clinical trials in the management of TNBC as well as perspectives for potential future treatments.

Treatment options after first-line immunotherapy in metastatic NSCLC

Introduction: The recent approvals of checkpoint inhibitors as single agents or in combination with chemotherapy with programmed death ligand 1 expression of < or ≥1% have challenged clinicians when it is time to begin a metastatic lung cancer patient in second-line therapy. The advantages given by immunotherapy over conventional chemotherapy such as improved overall survival and a better toxicity profile make the second-line clinical scenario more difficult for a patient who faces a likely inferior regimen as well as toxicity which may significantly impact the quality of life.Areas covered: Options given today by the National Comprehensive Cancer Network are very limited, and essentially, we go back to conventional cytotoxic agents alone or in combination with biological agents if possible. In this article, we discuss the actual treatment available for this difficult scenario and some of the ongoing trials which aim to address this dilemma.Expert commentary: This is an unmet need in lung cancer management; we need a better understanding of the mechanism of resistance to immunotherapy so we can target them once the patient moves to second-line treatment.

Role of mitochondria in rescuing glycolytically inhibited subpopulation of triple negative but not hormone-responsive breast cancer cells

Triple-negative breast cancer (TNBC) subtype is among the most aggressive cancers with the worst prognosis and least therapeutic targetability while being more likely to spread and recur. Cancer transformations profoundly alter cellular metabolism by increasing glucose consumption via glycolysis to support tumorigenesis. Here we confirm that relative to ER-positive cells (MCF7), TNBC cells (MBA-MD-231) rely more on glycolysis thus providing a rationale to target these cells with glycolytic inhibitors. Indeed, iodoacetate (IA), an effective GAPDH inhibitor, caused about 70% drop in MDA-MB-231 cell viability at 20 μM while 40 μM IA was needed to decrease MCF7 cell viability only by 30% within 4 hours of treatment. However, the triple negative cells showed strong ability to recover after 24 h whereas MCF7 cells were completely eliminated at concentrations <10 μM. To understand the mechanism of MDA-MB-231 cell survival, we studied metabolic modulations associated with acute and extended treatment with IA. The resilient TNBC cell population showed a significantly greater count of cells with active mitochondria, lower apoptotic markers, normal cell cycle regulations, moderately lowered ROS, but increased mRNA levels of p27 and PARP1; all compatible with enhanced cell survival. Our results highlight an interplay between PARP and mitochondrial oxidative phosphorylation in TNBC that comes into play in response to glycolytic disruption. In the light of these findings, we suggest that combined treatment with PARP and mitochondrial inhibitors may provide novel therapeutic strategy against TNBC.

Small-Molecule Poly(ADP-ribose) Polymerase and PD-L1 Inhibitor Conjugates as Dual-Action Anticancer Agents

Immune checkpoint blockades have revolutionized the treatment landscape for several cancer indications, yet they have not gained traction in a range of other tumors such as triple-negative breast cancer. Despite durable disease control by many patients, a third of cancer patients relapse due to acquired resistance. Combined immunotherapy has shown significant promise to overcome these grand challenges. In this report, we describe the synthesis and characterization of dual-action small-molecule PARP1/PD-L1 inhibitor conjugates as potential targeted anticancer agents. These conjugates display significant apoptosis and cytotoxic efficacy to approximately 2-20-fold better than their individual agents in a panel of cancer cell lines. This was underscored by derived combination indices, which was consistent with strong synergy when cells were treated with the individual agents, olaparib and BMS-001 using the Chou-Talalay method. Furthermore, we sought to unravel the mechanistic behavior of the conjugates and their implications on the PARP/PD-L1 axis. We used apoptosis, cell cycle, immunoblotting, and T-cell proliferation assays to establish the synergy imparted by these conjugates. These multifunctional compounds enable the discovery of small-molecule immunochemotherapeutic agents and chemical probes to elucidate the cross-talk between DNA repair and PD-L1 pathways.

CRISPR/Cas9-Mediated BRCA1 Knockdown Adipose Stem Cells Promote Breast Cancer Progression

BACKGROUND

The tumor microenvironment within the breast is rich in adipose elements. The interaction between adipose cells and breast cancer is poorly understood, particularly as it pertains to patients with genetic susceptibility to breast cancer. This study focuses on the phenotype of human adipose-derived stem cells with the BRCA1 mutation and the effect they may have on breast cancer cell behavior.

METHODS

CRISPR/Cas9 was used to generate de novo BRCA1-knockdown human adipose-derived stem cells. The effect of the BRCA1 knockdown on the adipose-derived stem cell phenotype was compared to wild-type adipose-derived stem cells and patient-derived breast adipose-derived stem cells with known BRCA1 mutations. Interactions between adipose-derived stem cells and the MDA-MB-231 breast cancer cell line were evaluated.

RESULTS

BRCA1-knockdown adipose-derived stem cells stimulated MDA-MB-231 proliferation (1.4-fold increase on day 4; p = 0.0074) and invasion (2.3-fold increase on day 2; p = 0.0171) compared to wild-type cells. Immunofluorescence staining revealed higher levels of phosphorylated ataxia telangiectasia-mutated activation in BRCA1-knockdown cells (72.9 ± 5.32 percent versus 42.9 ± 4.97 percent; p = 0.0147), indicating higher levels of DNA damage. Beta-galactosidase staining demonstrated a significantly higher level of senescence in BRCA1-knockdown cells compared with wild-type cells (7.9 ± 0.25 percent versus 0.17 ± 0.17 percent; p < 0.0001). Using quantitative enzyme-linked immunosorbent assay to evaluate conditioned media, the authors found significantly higher levels of interleukin-8 in BRCA1-knockdown cells (2.57 ± 0.32-fold; p = 0.0049).

CONCLUSIONS

The authors show for the first time that the BRCA1 mutation affects the adipose-derived stem cell phenotype. Moreover, CRISPR/Cas9-generated BRCA1-knockdown adipose-derived stem cells stimulate a more aggressive behavior in breast cancer cells than wild-type adipose-derived stem cells. This appears to be related to increased inflammatory cytokine production by means of a DNA damage-mediated cell senescence pathway.

Knockdown of DNA/RNA-binding protein KIN17 promotes apoptosis of triple-negative breast cancer cells

Effective therapy for breast cancer has been extensively studied worldwide, particularly for triple-negative breast cancer and drug-resistant subtypes. DNA/RNA-binding protein KIN17 (kin17) has been reported to be significantly upregulated in breast cancer cells, and is proposed to serve a role in the regulation of cell proliferation. The present study further investigated the association of kin17-knockdown with breast cancer cell apoptosis. Cell Counting kit-8, flow cytometry, TUNEL assay and caspase 3/7 analysis were performed on MDA-MB-231 cells to determine the association between kin17 and breast cancer cell apoptosis. In addition, western blot analysis was performed to investigate the mechanism of kin17 in the apoptosis of MDA-MB-231 cells. The results revealed that knockdown of kin17 inhibited proliferation and promoted apoptosis of MDA-MB-231 cells, and suggested a poly (adenosine diphosphate-ribose) polymerase-related mechanism behind the apoptosis of the cells. These findings suggested that kin17 could become a novel target for breast cancer therapy.

Combining PARP inhibition, radiation, and immunotherapy: A possible strategy to improve the treatment of cancer?

Immunotherapy has revolutionized the practice of oncology, improving survival in certain groups of patients with cancer. Immunotherapy can synergize with radiation therapy, increase locoregional control, and have abscopal effects. Combining it with other treatments, such as targeted therapies, is a promising means of improving the efficacy of immunotherapy. Because the value of immunotherapy is amplified with the expression of tumor antigens, coupling poly(ADP-ribose) polymerase (PARP) inhibitors and immunotherapy might be a promising treatment for cancer. Further, PARP inhibitors (PARPis) are being combined with radiation therapy to inhibit DNA repair functions, thus enhancing the effects of radiation; this association might interact with the antitumor immune response. Cytotoxic T lymphocytes are central to the antitumor immune response. PARP inhibitors and ionizing radiation can enhance the infiltration of cytotoxic T lymphocytes into the tumor bed, but they can also enhance PD-1/PDL-1 expression. Thus, the addition of immune checkpoint inhibitors with PARP inhibitors and/or ionizing radiation could counterbalance such immunosuppressive effects. With the present review article, we proposed to evaluate some of these associated therapies, and we explored the biological mechanisms and medical benefits of the potential combination of radiation therapy, immunotherapy, and PARP inhibitors.

Targeted and immuno-biology driven treatment strategies for triple-negative breast cancer: current knowledge and future perspectives

Introduction: Accounting for about 15% of breast cancer patients, triple-negative breast cancer (TNBC) is responsible for 25% of disease related deaths, more frequent distant spread and visceral metastasis. However, improving survival in TNBC failed and primary resistance, immunological ignorance and tumor heterogeneity limit clinical activity of novel therapies. In view of recent molecular, genetic and immunologic insights, this review aims to describe the current status of immunological and targeted treatments from a hypothesis driven perspective. Areas covered: Recent preclinical studies and ongoing clinical trials for immune directed and targeted treatments of TNBC are summarized, including immune-checkpoint blockade, resistance mechanisms, inhibition of poly (ADP-ribose) polymerase (PARP), combinatorial strategies as well as preclinical, hypothesis generating studies. Expert commentary: Sustained responses have been observed with immune-checkpoint blockade and PARP inhibitors demonstrated remarkable efficacy in germline BRCA mutated TNBC. In order to generate clinical success of many other, to date ineffective, targeted and immune therapies, the integration of multidimensional, large amounts of data, will be essential and likely accelerate treatment progress of TNBC.

Molecular Mechanisms and Emerging Therapeutic Targets of Triple-Negative Breast Cancer Metastasis

Breast cancer represents a highly heterogeneous disease comprised by several subtypes with distinct histological features, underlying molecular etiology and clinical behaviors. It is widely accepted that triple-negative breast cancer (TNBC) is one of the most aggressive subtypes, often associated with poor patient outcome due to the development of metastases in secondary organs, such as the lungs, brain, and bone. The molecular complexity of the metastatic process in combination with the lack of effective targeted therapies for TNBC metastasis have fostered significant research efforts during the past few years to identify molecular “drivers” of this lethal cascade. In this review, the most current and important findings on TNBC metastasis, as well as its closely associated basal-like subtype, including metastasis-promoting or suppressor genes and aberrantly regulated signaling pathways at specific stages of the metastatic cascade are being discussed. Finally, the most promising therapeutic approaches and novel strategies emerging from these molecular targets that could potentially be clinically applied in the near future are being highlighted.