Role of PARP in TNBC: Mechanism of Inhibition, Clinical Applications, and Resistance

Unlocking the epigenetic code: new insights into triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and clinically challenging subtype of breast cancer, lacking the expression of estrogen receptor (ER), progesterone receptor (PR), and HER2/neu. The absence of these receptors limits therapeutic options necessitating the exploration of novel treatment strategies. Epigenetic modifications, which include DNA methylation, histone modifications, and microRNA (miRNA) regulation, play a pivotal role in TNBC pathogenesis and represent promising therapeutic targets. This review delves into the therapeutic potential of epigenetic interventions in TNBC, with a focus on DNA methylation, histone modifications, and miRNA therapeutics. We examine the role of DNA methylation in gene silencing within TNBC and the development of DNA methylation inhibitors designed to reactivate silenced tumor suppressor genes. Histone modifications, through histone deacetylation and acetylation in particular, are critical in regulating gene expression. We explore the efficacy of histone deacetylase inhibitors (HDACi), which have shown promise in reversing aberrant histone deacetylation patterns, thereby restoring normal gene function, and suppressing tumor growth. Furthermore, the review highlights the dual role of miRNAs in TNBC as both oncogenes and tumor suppressors and discusses the therapeutic potential of miRNA mimics and inhibitors in modulating these regulatory molecules to inhibit cancer progression. By integrating these epigenetic therapies, we propose a multifaceted approach to target the underlying epigenetic mechanisms that drive TNBC progression. The synergistic use of DNA methylation inhibitors, HDACi, and the miRNA-based therapies offers a promising avenue for personalized treatment strategies, aiming to enhance the clinical outcome for patients with TNBC.

Insight into the molecular mechanism of anti-breast cancer therapeutic potential of substituted salicylidene-based compounds using cell-based assays and molecular docking studies

Targeting oxidative stress and inflammatory signaling pathways is an effective cancer prevention and therapy approach. The mechanism of action of synthesized salicylidene-based compounds was investigated in regulating key molecular targets of breast cancer development. Compounds (1), (4), (5), and (7) were found to be more cytotoxic to MCF-7 and 4T1 cells compared to non-cancerous Chang liver cells, while these compounds were cytotoxic to MDA-MB-231 cells, but with poor selectivity. The colony formation assay indicated that bioactive compounds induced significant damage to breast cancer cells, as observed by a reduction in the number of colonies compared to control cells. By inducing a concentration and time-dependent increase of luminescence and fluorescence of phosphatidylserine, and activating the expression of caspases-3, -7, -8, -9 in breast cancer cells, (1) and (7) have shown to induce caspase-dependent apoptosis. The downregulation of NF-kB-p65 and an upregulation of TP53 expression after exposure to bioactive compounds, demonstrated the suppression of two key targets of breast cancer development. Molecular docking studies revealed that selected protein targets strongly interact with bioactive compounds, and the estimated inhibition constants (Ki) of JAK2, STAT3, COX-2, HPV31 E6, EGFR1, TP53, and PARP1 were significantly decreased compared to acetylsalicylic acid. This could be a clear indication that these protein targets are implicated with antiproliferative efficacy, thereby warranting the potential of (1) and (7) to be used as anti-breast cancer drug candidates.

Remodeling of tumour microenvironment: strategies to overcome therapeutic resistance and innovate immunoengineering in triple-negative breast cancer

Triple-negative breast cancer (TNBC) stands as the most complex and daunting subtype of breast cancer affecting women globally. Regrettably, treatment options for TNBC remain limited due to its clinical complexity. However, immunotherapy has emerged as a promising avenue, showing success in developing effective therapies for advanced cases and improving patient outcomes. Improving TNBC treatments involves reducing side effects, minimizing systemic toxicity, and enhancing efficacy. Unlike traditional cancer immunotherapy, engineered nonmaterial's can precisely target TNBC, facilitating immune cell access, improving antigen presentation, and triggering lasting immune responses. Nanocarriers with enhanced sensitivity and specificity, specific cellular absorption, and low toxicity are gaining attention. Nanotechnology-driven immunoengineering strategies focus on targeted delivery systems using multifunctional molecules for precise tracking, diagnosis, and therapy in TNBC. This study delves into TNBC's tumour microenvironment (TME) remodeling, therapeutic resistance, and immunoengineering strategies using nanotechnology.

Alterations in the expression of homologous recombination repair (HRR) genes in breast cancer tissues considering germline BRCA1/2 mutation status

INTRODUCTION

Homologous recombination (HR) is a crucial DNA-repair mechanism, and its disruption can lead to the accumulation of mutations that initiate and promote cancer formation. The key HR genes, BRCA1 and BRCA2, are particularly significant as their germline pathogenic variants are associated with a hereditary predisposition to breast and/or ovarian cancer.

MATERIALS AND METHODS

The study was performed on 45 FFPE breast cancer tissues obtained from 24 and 21 patients, with and without the germline BRCA1/2 mutation, respectively. The expression of 11 genes: BRCA1, BRCA2, ATM, BARD1, FANCA, FANCB, FANCI, RAD50, RAD51D, BRIP1, and CHEK2 was assessed using Custom RT2 PCR Array (Qiagen), and results were analysed using R.

RESULTS

Cancer tissues from patients with BRCA1 or BRCA2 germline mutations displayed no significant differences in the expression of the selected HR genes compared to BRCA1 or BRCA2 wild-type cancer tissues. In BRCA1mut cancer tissues, BRCA1 expression was significantly higher than in BRCA2mut and BRCA wild-type cancer tissues.

CONCLUSIONS

In cancer tissues harbouring either BRCA1 or BRCA2 germline mutations, no significant differences in expression were observed at the mRNA level of any tested HR genes, except BRCA1. However, the significant differences observed in BRCA1 expression between germline BRCA1mut, germline BRCA2mut and BRCA1/2wt tissues may indicate a compensatory mechanism at the mRNA level to mitigate the loss of BRCA1 function in the cells.

Unveiling the future of breast cancer therapy: Cutting-edge antibody-drug conjugate strategies and clinical outcomes

Breast cancer has become the most prevalent malignant tumor worldwide and remains one of the leading causes of cancer-related mortality among women globally. The prognosis for patients with metastatic breast cancer remains poor, necessitating the exploration of novel therapeutic strategies to improve survival rates. In the era of precision medicine, antibody-drug conjugates (ADCs) have gained significant attention as a targeted therapeutic strategy in breast cancer treatment. ADCs, a relatively new treatment for breast cancer, deliver cytotoxic drugs (payloads), directly into the tumor space, turning chemotherapy into a targeted agent, which enables patients to experience significant improvements with manageable drug toxicity. For the treatment of breast cancer, there are three ADCs approved for breast cancer treatment: Trastuzumab emtansine (T-DM1), Trastuzumab Deruxtecan (T-Dxd) targeting HER-2, and Sacituzumab Govitecan (SG) targeting Trop-2. Recent clinical studies have demonstrated that the benefits of ADC therapies extend beyond HER2-positive breast cancer toinclude hormone receptor (HR)-positive breast cancer, triple-negative breast cancer (TNBC), and HER2-low expressing breast cancer. Notably, the DESTINY-Breast series of studies, particularly focusing on T-Dxd, encompass neoadjuvant, adjuvant, and multiple lines of therapy for advanced breast cancer. This marks the advent of a comprehensive ADC era in breast cancer treatment. This review summarizes the efficacy and adverse effects of ADC therapies that have completed or are currently undergoing phase I-III clinical trials. Additionally, it analyzes potential combination strategies to overcome ADC resistance, aiming to provide clinicians with a comprehensive clinical guide to the use of ADCs in breast cancer treatment.

Nuclear IMPDH2 controls the DNA damage response by modulating PARP1 activity

Nuclear metabolism and DNA damage response are intertwined processes, but the precise molecular links remain elusive. Here, we explore this crosstalk using triple-negative breast cancer (TNBC) as a model, a subtype often prone to DNA damage accumulation. We show that the de novo purine synthesis enzyme IMPDH2 is enriched on chromatin in TNBC compared to other subtypes. IMPDH2 chromatin localization is DNA damage dependent, and IMPDH2 repression leads to DNA damage accumulation. On chromatin, IMPDH2 interacts with and modulates PARP1 activity by controlling the nuclear availability of NAD+ to fine-tune the DNA damage response. However, when IMPDH2 is restricted to the nucleus, it depletes nuclear NAD+, leading to PARP1 cleavage and cell death. Our study identifies a non-canonical nuclear role for IMPDH2, acting as a convergence point of nuclear metabolism and DNA damage response.

Study of Iron Complex Photosensitizer with Hollow Double-Shell Nano Structure Used to Enhance Ferroptosis and Photodynamic Therapy

Ferroptosis therapy, which uses ferroptosis inducers to produce lethal lipid peroxides and induce tumor cell death, is considered a promising cancer treatment strategy. However, challenges remain regarding how to increase the accumulation of reactive oxygen species (ROS) in the tumor microenvironment (TME) to enhance antitumor efficacy. In this study, a hyaluronic acid (HA) encapsulated hollow mesoporous manganese dioxide (H-MnO2) with double-shell nanostructure is designed to contain iron coordinated cyanine near-infrared dye IR783 (IR783-Fe) for synergistic ferroptosis photodynamic therapy against tumors. The nano photosensitizer IR783-Fe@MnO2-HA, in which HA actively targets the CD44 receptor, subsequently dissociates and releases Fe3+ and IR783 in acidic TME. First, Fe3+ consumes glutathione to produce Fe2+, which promotes the Fenton reaction in cells to produce hydroxyl free radicals (·OH) and induce ferroptosis of tumor cells. In addition, MnO2 catalyzes the production of O2 from H2O2 and enhances the production of singlet oxygen (1O2) by IR783 under laser irradiation, thus increasing the production and accumulation of ROS to provide photodynamic therapy. The highly biocompatible IR783-Fe@MnO2-HA nano-photosensitizers have exhibited tumor-targeting ability and efficient tumor inhibition in vivo due to the synergistic effect of photodynamic and ferroptosis antitumor therapies.

Peroxiporins in Triple-Negative Breast Cancer: Biomarker Potential and Therapeutic Perspectives

Triple-negative breast cancer (TNBC) remains one of the most challenging subtypes since it is initially characterized by the absence of specific biomarkers and corresponding targeted therapies. Advances in methodology, translational informatics, genomics, and proteomics have significantly contributed to the identification of therapeutic targets. The development of innovative treatments, such as antibody-drug conjugates and immune checkpoint inhibitors, alongside chemotherapy, has now become the standard of care. However, the quest for biomarkers defining therapy outcomes is still ongoing. Peroxiporins, which comprise a subgroup of aquaporins, which are membrane pores facilitating the transport of water, glycerol, and hydrogen peroxide, have emerged as potential biomarkers for therapy response. Research on peroxiporins reveals their involvement beyond traditional channeling activities, which is also reflected in their cellular localization and roles in cellular signaling pathways. This research on peroxiporins provides fresh insights into the mechanisms of therapy resistance in tumors, offering potential avenues for predicting treatment outcomes and tailoring successful TNBC therapies.

Chemoresistance to additive PARP/PI3K dual inhibition in triple-negative breast cancer cell lines is associated with adaptive stem cell-like prevalence

Cancer stem-like cells (CSCs) are posited to exhibit specialized oncogenic capacity to drive malignancies. CSCs are distinguished by enhanced hallmarks of cancer, including apoptosis avoidance, phenotypic plasticity and aberrant growth pathway signaling. Standard-of-care chemotherapies targeted to rapidly cycling cells routinely fail to eliminate this resistant subpopulation, leading to disease recurrence and metastasis. Triple-negative breast cancer (TNBC), a highly aggressive subtype of breast cancer, is enriched for tumor-propagating CD44+/CD24-/low CSCs, which are poorly ablated by chemotherapeutics and are associated with poor prognosis. CD44 governs sustained PI3K signaling in breast cancer, which is essential for CSC maintenance. PI3K inhibition can elicit DNA damage and down-regulate BRCA1 expression, which in turn enhance the synthetic lethality of PARP inhibitors. Here, we examined a dual chemotherapeutic approach targeting these pathways by combining a pan-PI3K inhibitor (Buparlisib) and a PARP1 inhibitor (Olaparib) on a panel of TNBC cell lines with distinct mutational profiles and proportions of CSCs. We observed differential sensitivity to this dual inhibition strategy and varying cellular stress and resistance responses across eight TNBC lines. The dual chemotherapeutic effect is associated with a reduction in S-phase cells, an increased in apoptotic cells and elevated expression of cleaved PARP, indicating a provoked replicative stress response. We observed that PARP/PI3K inhibition efficacy was potentiated by repeated administration in some TNBC lines and identified critical treatment schedules, which further potentiated the dual chemotherapeutic effect. Dual inhibition induced small but significant increases in CSC relative abundance as marked by CD44+/CD24-/low or ALDH1+ cells and increased stress and survival signaling in multiple TNBC cell lines, suggesting this sub-population contributes to TNBC chemoresistance. These results suggest the additive effects of PARP and PI3K inhibition against CSC phenotypes may be enhanced by temporally-staged administration in TNBC cells.

Molecular pathways and therapeutic targets linked to triple-negative breast cancer (TNBC)

Cancer is a group of diseases characterized by uncontrolled cellular growth, abnormal morphology, and altered proliferation. Cancerous cells lose their ability to act as anchors, allowing them to spread throughout the body and infiltrate nearby cells, tissues, and organs. If these cells are not identified and treated promptly, they will likely spread. Around 70% of female breast cancers are caused by a mutation in the BRCA gene, specifically BRCA1. The absence of progesterone, oestrogen and HER2 receptors (human epidermal growth factor) distinguishes the TNBC subtype of breast cancer. There were approximately 6,85,000 deaths worldwide and 2.3 million new breast cancer cases in women in 2020. Breast cancer is the most common cancer globally, affecting 7.8 million people at the end of 2020. Compared to other cancer types, breast cancer causes more women to lose disability-adjusted life years (DALYs). Worldwide, women can develop breast cancer at any age after puberty, but rates increase with age. The maintenance of mammary stem cell stemness is disrupted in TNBC, governed by signalling cascades controlling healthy mammary gland growth and development. Interpreting these essential cascades may facilitate an in-depth understanding of TNBC cancer and the search for an appropriate therapeutic target. Its treatment remains challenging because it lacks specific receptors, which renders hormone therapy and medications ineffective. In addition to radiotherapy, numerous recognized chemotherapeutic medicines are available as inhibitors of signalling pathways, while others are currently undergoing clinical trials. This article summarizes the vital druggable targets, therapeutic approaches, and strategies associated with TNBC.

Discovery of novel PARP-1 inhibitors using tandem in silico studies: integrated docking, e-pharmacophore, deep learning based de novo and molecular dynamics simulation approach

Cancer accounts for the majority of deaths worldwide, and the increasing incidence of breast cancer is a matter of grave concern. Poly (ADP-ribose) polymerase-1 (PARP-1) has emerged as an attractive target for the treatment of breast cancer as it has an important role in DNA repair. The focus of the study was to identify novel PARP-1 inhibitors using a blend of tandem structure-based screening (Docking and e-pharmacophore-based screening) and artificial intelligence (deep learning)-based de novo approaches. The scrutiny of compounds having good binding characteristics for PARP-1 was carried out using a tandem mode of screening along with parameters such as binding energy and ADME analysis. The efforts afforded compound Vab1 (PubChem ID 129142036), which was chosen as a seed for obtaining novel compounds through a trained artificial intelligence (AI)-based model. Resultant compounds were assessed for PARP-1 inhibition; binding affinity prediction and interaction pattern analysis were carried out using the extra precision (XP) mode of docking. Two best hits, Vab1-b and Vab1-g, exhibiting good dock scores and suitable interactions, were subjected to 100 nanoseconds (ns) of molecular dynamics simulation in the active site of PARP-1 and compared with the reference Protein-Ligand Complex. The stable nature of PARP-1 upon binding to these compounds was revealed through MD simulation.Communicated by Ramaswamy H. Sarma.

Therapeutic Advantage of Targeting PRMT5 in Combination with Chemotherapies or EGFR/HER2 Inhibitors in Triple-Negative Breast Cancers

Purpose

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subgroup characterized by a high risk of resistance to chemotherapies and high relapse potential. TNBC shows inter-and intra-tumoral heterogeneity; more than half expresses high EGFR levels and about 30% are classified as HER2-low breast cancers. High PRMT5 mRNA levels are associated with poor prognosis in TNBC and inhibiting PRMT5 impairs the viability of subsets of TNBC cell lines and delays tumor growth in TNBC mice models. TNBC patients may therefore benefit from a treatment targeting PRMT5. The aim of this study was to assess the therapeutic benefit of combining a PRMT5 inhibitor with different chemotherapies used in the clinics to treat TNBC patients, or with FDA-approved inhibitors targeting the HER family members.

Methods

The drug combinations were performed using proliferation and colony formation assays on TNBC cell lines that were sensitive or resistant to EPZ015938, a PRMT5 inhibitor that has been evaluated in clinical trials. The chemotherapies analyzed were cisplatin, doxorubicin, camptothecin, and paclitaxel. The targeted therapies tested were erlotinib (EGFR inhibitor), neratinib (EGFR/HER2/HER4 inhibitor) and tucatinib (HER2 inhibitor).

Results

We found that PRMT5 inhibition synergized mostly with cisplatin, and to a lesser extent with doxorubicin or camptothecin, but not with paclitaxel, to impair TNBC cell proliferation. PRMT5 inhibition also synergized with erlotinib and neratinib in TNBC cell lines, especially in those overexpressing EGFR. Additionally, a synergistic interaction was observed with neratinib and tucatinib in a HER2-low TNBC cell line as well as in a HER2-positive breast cancer cell line. We noticed that synergy can be obtained in TNBC cell lines that were resistant to PRMT5 inhibition alone.

Conclusion

Altogether, our data highlight the therapeutic potential of targeting PRMT5 using combinatorial strategies for the treatment of subsets of TNBC patients.

Discovery of a novel dual-target inhibitor of CDK12 and PARP1 that induces synthetic lethality for treatment of triple-negative breast cancer

Triple negative breast cancer (TNBC) is one of the most aggressive breast tumors, with a high rate of recurrence and metastasis as well as a poor prognosis. Consequently, it is urgent to find new targeted therapeutic strategies and development of corresponding drugs. Previous studies have shown that CDK12 inhibitors in combination with PARP1 inhibitors is able to induce synthetic lethality in TNBC cells. Here, we reported simultaneously inhibition of CDK12 and PARP1 by genetic or pharmacological approaches synergistically inhibited the proliferation of TNBC cells. Then, a series of small molecule inhibitors targeting both CDK12 and PARP1 were designed and synthesized. The new dual-target inhibitor (12e) showed potent inhibitory activity against CDK12 (IC50 = 285 nM) and PARP1 (IC50 = 34 nM), as well as good anti-proliferative effects in TNBC cell lines. Meanwhile, compound 12e showed favorable synergistic anti-tumor efficacy in cells and xenografts by inhibiting DNA damage repair, promoting cell cycle arrest and apoptosis. Taken together, we successfully synthesized the first effective CDK12-PARP1 dual inhibitor, which is expected to be an attractive therapeutic strategy for TNBC.

Small molecule nitroalkenes inhibit RAD51-mediated homologous recombination and amplify triple-negative breast cancer cell killing by DNA-directed therapies

Nitro fatty acids (NO2-FAs) are endogenously generated lipid signaling mediators from metabolic and inflammatory reactions between conjugated diene fatty acids and nitric oxide or nitrite-derived reactive species. NO2-FAs undergo reversible Michael addition with hyperreactive protein cysteine thiolates to induce posttranslational protein modifications that can impact protein function. Herein, we report a novel mechanism of action of natural and non-natural nitroalkenes structurally similar to (E) 10-nitro-octadec-9-enoic acid (CP-6), recently de-risked by preclinical Investigational New Drug-enabling studies and Phase 1 and Phase 2 clinical trials and found to induce DNA damage in a TNBC xenograft by inhibiting homologous-recombination (HR)-mediated repair of DNA double-strand breaks (DSB). CP-6 specifically targets Cys319, essential in RAD51-controlled HR-mediated DNA DSB repair in cells. A nitroalkene library screen identified two structurally different nitroalkenes, a non-natural fatty acid [(E) 8-nitro-nonadec-7-enoic acid (CP-8)] and a dicarboxylate ester [dimethyl (E)nitro-oct-4-enedioate (CP-23)] superior to CP-6 in TNBC cells killing, synergism with three different inhibitors of the poly ADP-ribose polymerase (PARP) and γ-IR. CP-8 and CP-23 effectively inhibited γ-IR-induced RAD51 foci formation and HR in a GFP-reported assay but did not affect benign human epithelial cells or cell cycle phases. In vivo, CP-8 and CP-23's efficacies diverged as only CP-8 showed promising anticancer activities alone and combined with the PARP inhibitor talazoparib in an HR-proficient TNBC mouse model. As preliminary preclinical toxicology analysis also suggests CP-8 as safe, our data endorse CP-8 as a novel anticancer molecule for treating cancers sensitive to homologous recombination-mediated DNA repair inhibitors.

A novel isoxazole compound CM2-II-173 inhibits the invasive phenotype of triple-negative breast cancer cells

Invasion and metastasis are important hallmarks of breast cancer and are the leading cause of patient mortality. Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer characterized by a poor prognosis and a lack of effective targeted therapies. The present study investigated the inhibitory effect of a novel FTY720 derivative on the invasive phenotype of TNBC cells. Here, we showed that a novel compound with an isoxazole ring, 4-(3-Decylisoxazol-5-yl)-1-hydroxy-2-(hydroxymethyl)butan-2-aminium chloride (CM2-II-173), significantly inhibited invasiveness of MDA-MB-231 TNBC cells. Expression of matrix metalloproteinase (MMP)-9 and invasiveness of MCF10A normal breast cells induced by sphingosine-1-phosphate (S1P) were reduced by CM2-II-173 treatment. Activations of pMEK1, pAkt, pERK, and p38 MAPK by S1P were inhibited by treatment with CM2-II-173. Proliferation and anchorage-independent growth of MDA-MB-231 TNBC cells were significantly decreased by CM2-II-173. CM2-II-173 efficiently induced apoptosis in MDA-MB-231 TNBC cells. CM2-II-173 significantly inhibited invasive phenotypes of breast, liver, prostate, and ovarian cancer cells. CM2-II-173 exhibited a more potent effect on the invasiveness of MDA-MB-231 TNBC cells compared to FTY720. Taken together, this study demonstrated that CM2-II-173 has the potential to be a lead compound that can inhibit cancer progression of not only TNBC cells, but also of liver, prostate, and ovarian cancer cells.

Small molecule nitroalkenes inhibit RAD51-mediated homologous recombination and amplify triple-negative breast cancer cell killing by DNA-directed therapies

Nitro fatty acids (NO 2 -FAs) are endogenously generated lipid signaling mediators from metabolic and inflammatory reactions between conjugated diene fatty acids and nitric oxide or nitrite-derived reactive species. NO 2 -FAs undergo reversible Michael addition with hyperreactive protein cysteine thiolates to induce posttranslational protein modifications that can impact protein function. Herein, we report a novel mechanism of action of natural and non-natural nitroalkenes structurally similar to ( E ) 10-nitro-octadec-9-enoic acid (CP-6), recently de-risked by preclinical Investigational New Drug-enabling studies and Phase 1 and Phase 2 clinical trials and found to induce DNA damage in a TNBC xenograft by inhibiting homologous-recombination (HR)-mediated repair of DNA double-strand breaks (DSB). CP-6 specifically targets Cys319, essential in RAD51-controlled HR-mediated DNA DSB repair in cells. A nitroalkene library screen identified two structurally different nitroalkenes, a non-natural fatty acid [( E ) 8-nitro- nonadec-7-enoic acid (CP-8)] and a dicarboxylate ester [dimethyl ( E )nitro-oct-4-enedioate (CP- 23)] superior to CP-6 in TNBC cells killing, synergism with three different inhibitors of the poly ADP-ribose polymerase (PARP) and γ-IR. CP-8 and CP-23 effectively inhibited γ-IR-induced RAD51 foci formation and HR in a GFP-reported assay but did not affect benign human epithelial cells or cell cycle phases. In vivo, CP-8 and CP-23's efficacies diverged as only CP-8 showed promising anticancer activities alone and combined with the PARP inhibitor talazoparib in an HR-proficient TNBC mouse model. As preliminary preclinical toxicology analysis also suggests CP-8 as safe, our data endorse CP-8 as a novel anticancer molecule for treating cancers sensitive to homologous recombination-mediated DNA repair inhibitors.

Mitochondrial Metabolism: A New Dimension of Personalized Oncology

Energy is needed by cancer cells to stay alive and communicate with their surroundings. The primary organelles for cellular metabolism and energy synthesis are mitochondria. Researchers recently proved that cancer cells can steal immune cells' mitochondria using nanoscale tubes. This finding demonstrates the dependence of cancer cells on normal cells for their living and function. It also denotes the importance of mitochondria in cancer cells' biology. Emerging evidence has demonstrated how mitochondria are essential for cancer cells to survive in the harsh tumor microenvironments, evade the immune system, obtain more aggressive features, and resist treatments. For instance, functional mitochondria can improve cancer resistance against radiotherapy by scavenging the released reactive oxygen species. Therefore, targeting mitochondria can potentially enhance oncological outcomes, according to this notion. The tumors' responses to anticancer treatments vary, ranging from a complete response to even cancer progression during treatment. Therefore, personalized cancer treatment is of crucial importance. So far, personalized cancer treatment has been based on genomic analysis. Evidence shows that tumors with high mitochondrial content are more resistant to treatment. This paper illustrates how mitochondrial metabolism can participate in cancer resistance to chemotherapy, immunotherapy, and radiotherapy. Pretreatment evaluation of mitochondrial metabolism can provide additional information to genomic analysis and can help to improve personalized oncological treatments. This article outlines the importance of mitochondrial metabolism in cancer biology and personalized treatments.

Mitochondrial metabolism: a predictive biomarker of radiotherapy efficacy and toxicity

INTRODUCTION

Radiotherapy is a mainstay of cancer treatment. Clinical studies revealed a heterogenous response to radiotherapy, from a complete response to even disease progression. To that end, finding the relative prognostic factors of disease outcomes and predictive factors of treatment efficacy and toxicity is essential. It has been demonstrated that radiation response depends on DNA damage response, cell cycle phase, oxygen concentration, and growth rate. Emerging evidence suggests that altered mitochondrial metabolism is associated with radioresistance.

METHODS

This article provides a comprehensive evaluation of the role of mitochondria in radiotherapy efficacy and toxicity. In addition, it demonstrates how mitochondria might be involved in the famous 6Rs of radiobiology.

RESULTS

In terms of this idea, decreasing the mitochondrial metabolism of cancer cells may increase radiation response, and enhancing the mitochondrial metabolism of normal cells may reduce radiation toxicity. Enhancing the normal cells (including immune cells) mitochondrial metabolism can potentially improve the tumor response by enhancing immune reactivation. Future studies are invited to examine the impacts of mitochondrial metabolism on radiation efficacy and toxicity. Improving radiotherapy response with diminishing cancer cells' mitochondrial metabolism, and reducing radiotherapy toxicity with enhancing normal cells' mitochondrial metabolism.

Updates on Triple-Negative Breast Cancer in Type 2 Diabetes Mellitus Patients: From Risk Factors to Diagnosis, Biomarkers and Therapy

Triple-negative breast cancer (TNBC) is usually the most malignant and aggressive mammary epithelial tumor characterized by the lack of expression for estrogen receptors and progesterone receptors, and the absence of epidermal growth factor receptor (HER)2 amplification. Corresponding to 15-20% of all breast cancers and well-known by its poor clinical outcome, this negative receptor expression deprives TNBC from targeted therapy and makes its management therapeutically challenging. Type 2 diabetes mellitus (T2DM) is the most common ageing metabolic disorder due to insulin deficiency or resistance resulting in hyperglycemia, hyperinsulinemia, and hyperlipidemia. Due to metabolic and hormonal imbalances, there are many interplays between both chronic disorders leading to increased risk of breast cancer, especially TNBC, diagnosed in T2DM patients. The purpose of this review is to provide up-to-date information related to epidemiology and clinicopathological features, risk factors, diagnosis, biomarkers, and current therapy/clinical trials for TNBC patients with T2DM compared to non-diabetic counterparts. Thus, in-depth investigation of the diabetic complications on TNBC onset, development, and progression and the discovery of biomarkers would improve TNBC management through early diagnosis, tailoring therapy for a better outcome of T2DM patients diagnosed with TNBC.

Gestational Breast Cancer - a Review of Outcomes, Pathophysiology, and Model Systems

The onset of pregnancy marks the start of offspring development, and represents the key physiological event that induces re-organization and specialization of breast tissue. Such drastic tissue remodeling has also been linked to epithelial cell transformation and the establishment of breast cancer (BC). While patient outcomes for BC overall continue to improve across subtypes, prognosis remains dismal for patients with gestational breast cancer (GBC) and post-partum breast cancer (PPBC), as pregnancy and lactation pose additional complications and barriers to several gold standard clinical approaches. Moreover, delayed diagnosis and treatment, coupled with the aggressive time-scale in which GBC metastasizes, inevitably contributes to the higher incidence of disease recurrence and patient mortality. Therefore, there is an urgent and evident need to better understand the factors contributing to the establishment and spreading of BC during pregnancy. In this review, we provide a literature-based overview of the diagnostics and treatments available to patients with BC more broadly, and highlight the treatment deficit patients face due to gestational status. Further, we review the current understanding of the molecular and cellular mechanisms driving GBC, and discuss recent advances in model systems that may support the identification of targetable approaches to block BC development and dissemination during pregnancy. Our goal is to provide an updated perspective on GBC, and to inform critical areas needing further exploration to improve disease outcome.

Mutations in Homologous Recombination Genes and Loss of Heterozygosity Status in Advanced-Stage Breast Carcinoma

Poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPis) have demonstrated antitumor activity in cancers with a homologous recombination deficiency (HRD) and have recently been approved by the FDA for the treatment of germline BRCA1/2-mutation-associated breast cancer. PARPis have also been found to be efficacious in BRCA wild-type (BRCAwt) lesions with high genomic loss of heterozygosity (LOH-high). The goal of this study was to retrospectively investigate the tumor mutations in homologous recombination (HRR) genes and the LOH score in advanced-stage breast carcinomas (BCs). Sixty-three patients were included in our study, 25% of whom had HRR gene mutations in their tumors, including 6% BRCA1/2 and 19% non-BRCA-containing gene mutations. An HRR gene mutation was associated with a triple-negative phenotype. Twenty-eight percent of the patients had an LOH-high score, which, in turn, was associated with a high histological grade, a triple-negative phenotype, and a high tumor mutational burden (TMB). Among the six patients who received PARPi therapy, one had a tumor with a PALB2 mutation other than BRCA and had a clinical partial response. Twenty-two percent of the LOH-low tumors had BRCAwt-HRR gene mutations, compared with 11% of the LOH-high tumors. Comprehensive genomic profiling revealed a subset of breast cancer patients with a BRCAwt-HRR gene mutation that would be missed by an LOH test. The necessity of next-generation sequencing coupled with HRR gene analysis for PARPi therapy requires further investigation in clinical trials.

Recent Advances with Precision Medicine Treatment for Breast Cancer including Triple-Negative Sub-Type

Breast cancer is a heterogeneous disease with different molecular subtypes. Breast cancer is the second leading cause of mortality in woman due to rapid metastasis and disease recurrence. Precision medicine remains an essential source to lower the off-target toxicities of chemotherapeutic agents and maximize the patient benefits. This is a crucial approach for a more effective treatment and prevention of disease. Precision-medicine methods are based on the selection of suitable biomarkers to envision the effectiveness of targeted therapy in a specific group of patients. Several druggable mutations have been identified in breast cancer patients. Current improvements in omics technologies have focused on more precise strategies for precision therapy. The development of next-generation sequencing technologies has raised hopes for precision-medicine treatment strategies in breast cancer (BC) and triple-negative breast cancer (TNBC). Targeted therapies utilizing immune checkpoint inhibitors (ICIs), epidermal growth factor receptor inhibitor (EGFRi), poly(ADP-ribose) polymerase inhibitor (PARPi), antibody-drug conjugates (ADCs), oncolytic viruses (OVs), glucose transporter-1 inhibitor (GLUT1i), and targeting signaling pathways are potential treatment approaches for BC and TNBC. This review emphasizes the recent progress made with the precision-medicine therapy of metastatic breast cancer and TNBC.

Upregulation of the ferroptosis-related STEAP3 gene is a specific predictor of poor triple-negative breast cancer patient outcomes

Objective

This study was designed to assess ferroptosis regulator gene (FRG) expression patterns in patients with TNBC based on data derived from The Cancer Genome Atlas (TCGA). Further, it was utilized to establish a TNBC FRG signature, after which the association between this signature and the tumor immune microenvironment (TIME) composition was assessed, and relevant prognostic factors were explored.

Methods

The TCGA database was used to obtain RNA expression datasets and clinical information about 190 TNBC patients, after which a prognostic TNBC-related FRG signature was established using a least absolute shrinkage and selection operator (LASSO) Cox regression approach. These results were validated with separate data from the Gene Expression Omnibus (GEO). The TNBC-specific prognostic gene was identified via this method. The STEAP3 was then validated through Western immunoblotting, immunohistochemical staining, and quantitative real‐time polymerase chain reaction (RT-qPCR) analyses of clinical tissue samples and TNBC cell lines. Chemotherapy interactions and predicted drug sensitivity studies were investigated to learn more about the potential clinical relevance of these observations.

Results

These data revealed that 87 FRGs were differentially expressed when comparing TNBC tumors and healthy tissue samples (87/259, 33.59%). Seven of these genes (CA9, CISD1, STEAP3, HMOX1, DUSP1, TAZ, HBA1) are significantly related to the overall survival of TNBC patients. Kaplan-Meier analyses and established FRG signatures and nomograms identified CISD1 and STEAP3 genes of prognostic relevance. Prognostic Risk Score values were positively correlated with the infiltration of CD4+ T cells (p = 0.001) and myeloid dendritic cells (p =0.004). Further evidence showed that STEAP3 was strongly and specifically associated with TNBC patient OS (P<0.05). The results above were confirmed by additional examinations of STEAP3 expression changes in TNBC patient samples and cell lines. High STEAP3 levels were negatively correlated with half-maximal inhibitory concentration (IC50) values for GSK1904529A (IGF1R inhibitor), AS601245 (JNK inhibitor), XMD8−85 (Erk5 inhibitor), Gefitinib, Sorafenib, and 5-Fluorouracil (P < 0.05) in patients with TNBC based on information derived from the TCGA-TNBC dataset.

Conclusion

In the present study, a novel FRG model was developed and used to forecast the prognosis of TNBC patients accurately. Furthermore, it was discovered that STEAP3 was highly overexpressed in people with TNBC and associated with overall survival rates, laying the groundwork for the eventually targeted therapy of individuals with this form of cancer.

Novel diagnostic biomarkers of T cell-mediated tumor killing characteristics for early-stage triple negative breast cancer: A SEER analysis and molecular portraits

The primary objective was to investigate the epidemiology, molecular characteristics, and clinical survival to identify potential transcriptome biomarkers to promote early diagnosis and screening of triple-negative breast cancer patients. Early-stage triple-negative breast cancer patients (E-TNBC) and late-stage triple-negative breast cancer patients (L-TNBC) were identified from the Surveillance, Epidemiology, and End Results database from 2010 to 2019. The difference in cancer specific survival (CSS) and overall survival (OS) between E-TNBC and L-TNBC was analyzed via a Kaplan-Meier plotter. 118 triple-negative breast cancer samples and 114 normal samples with the RNA sequencing expression data were selected from the cohort of TCGA breast cancer from UCSC Xena Database. The study involved 13,690 patients with L-TNBC and 44,994 patients with E-TNBC. L-TNBC patients were more frequently to be ≤ 60 years old (54.9% vs 52.2%), multiple primary site (44.0% vs 30.1%), and were more likely to receive radiotherapy (49.6% vs 47.4%) and chemotherapy (81.1% vs 72.1%), while L-TNBC patients were less likely to be white (68.7% vs 73.0%), married or with domestic partner (46.7% vs 54.7%), poorly differentiated grade (54.0% vs 61.9%), < 3 months from diagnosis to treatment (91.6% vs 96.4%), and were less likely to receive surgery (72.3% vs 95.4%). Stage-stratified survival analysis revealed that the prognosis of L-TNBC was worse when compared to E-TNBC, Kaplan-Meier analysis demonstrated that there were striking differences in OS and CSS between E-TNBC and L-TNBC. In the multivariable regression models, L-TNBC was the single highest risk factor, with a death risk that was 4.741 and 6.074 times higher than E-TNBC in terms of OS and CSS, respectively. The results also showed that treatment with surgery, radiation, or chemotherapy was effective for a better prognosis. Transcriptome analyses revealed that the top 5 upregulated genes in L-TNBC were, respectively, ISX, ALOX15B, MADCAM1, TP63, and ARG1 compared with E-TNBC. And the top 5 downregulated genes were, respectively, CTAG1B, CT45A1, MAGEC2, TFF2, and TNFRSF11B. The L-TNBC exhibited a lower rate of survival than E-TNBC, and the 2 groups differed in terms of transcriptome characteristics. To date, the diagnostic value of T cell-mediated tumor killing portraits on E-TNBC may not be completely recognized.

Regulation of Inflammasome by microRNAs in Triple-Negative Breast Cancer: New Opportunities for Therapy

During the past decade, researchers have investigated the molecular mechanisms of breast cancer initiation and progression, especially triple-negative breast cancer (TNBC), in order to identify specific biomarkers that could serve as feasible targets for innovative therapeutic strategies development. TNBC is characterized by a dynamic and aggressive nature, due to the absence of estrogen, progesterone and human epidermal growth factor 2 receptors. TNBC progression is associated with the dysregulation of nucleotide-binding oligomerization domain-like receptor and pyrin domain-containing protein 3 (NLRP3) inflammasome, followed by the release of pro-inflammatory cytokines and caspase-1 dependent cell death, termed pyroptosis. The heterogeneity of the breast tumor microenvironment triggers the interest of non-coding RNAs' involvement in NLRP3 inflammasome assembly, TNBC progression and metastasis. Non-coding RNAs are paramount regulators of carcinogenesis and inflammasome pathways, which could help in the development of efficient treatments. This review aims to highlight the contribution of non-coding RNAs that support inflammasome activation and TNBC progression, pointing up their potential for clinical applications as biomarkers for diagnosis and therapy.

Novel combination treatment of CDK 4/6 inhibitors with PARP inhibitors in triple negative breast cancer cells

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors provide promising results for treating hormone receptor-positive breast cancer. However, the efficacy of CDK4/6 inhibitors remains uncertain in triple negative breast cancer (TNBC) patients with particularly carrying RB-deficient tumors. Poly-(ADP-ribose) polymerase (PARP) inhibitors offer a therapeutic strategy for the treatment of BRCA-mutated TNBC patients. However, the acquired drug resistance, changes in the cell cycle regulation, and DNA damage repair have demonstrated the necessity for developing new combination strategies. This preclinical study assessed a combinatory treatment of the CDK4/6 inhibitor abemaciclib with PARP inhibitors talazoparib (TAL) in HCC1937 BRCA-mutated RB-deficient TNBC cells and TAL-resistant HCC1937-R cells through WST-1 analysis, annexin V, cell cycle, acridine orange/propidium iodide staining, RT-PCR, and apoptosis array. Our findings revealed that abemaciclib and TAL combination synergistically suppressed the growth of TNBC cells and overcame TAL resistance through G0/G1 arrest and the activity of both intrinsic and extrinsic apoptotic pathways. These preliminary results suggest that the combination of abemaciclib and TAL could expand the use of these inhibitors in BRCA mutated and RB deficient TNBC patients and potentially overcomes PARP inhibitors resistance.

Molecular Classification, Treatment, and Genetic Biomarkers in Triple-Negative Breast Cancer: A Review

Breast cancer is the most common malignancy and the second most common cause of cancer-related mortality in women. Triple-negative breast cancers do not express estrogen receptors, progesterone receptors, or human epidermal growth factor receptor 2 and have a higher recurrence rate, greater metastatic potential, and lower overall survival rate than those of other breast cancers. Treatment of triple-negative breast cancer is challenging; molecular-targeted therapies are largely ineffective and there is no standard treatment. In this review, we evaluate current attempts to classify triple-negative breast cancers based on their molecular features. We also describe promising treatment methods with different advantages and discuss genetic biomarkers and other prediction tools. Accurate molecular classification of triple-negative breast cancers is critical for patient risk categorization, treatment decisions, and surveillance. This review offers new ideas for more effective treatment of triple-negative breast cancer and identifies novel targets for drug development.

Role of PARP Inhibitors in Cancer Immunotherapy: Potential Friends to Immune Activating Molecules and Foes to Immune Checkpoints

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induce cytotoxic effects as single agents in tumors characterized by defective repair of DNA double-strand breaks deriving from BRCA1/2 mutations or other abnormalities in genes associated with homologous recombination. Preclinical studies have shown that PARPi-induced DNA damage may affect the tumor immune microenvironment and immune-mediated anti-tumor response through several mechanisms. In particular, increased DNA damage has been shown to induce the activation of type I interferon pathway and up-regulation of PD-L1 expression in cancer cells, which can both enhance sensitivity to Immune Checkpoint Inhibitors (ICIs). Despite the recent approval of ICIs for a number of advanced cancer types based on their ability to reinvigorate T-cell-mediated antitumor immune responses, a consistent percentage of treated patients fail to respond, strongly encouraging the identification of combination therapies to overcome resistance. In the present review, we analyzed both established and unexplored mechanisms that may be elicited by PARPi, supporting immune reactivation and their potential synergism with currently used ICIs. This analysis may indicate novel and possibly patient-specific immune features that might represent new pharmacological targets of PARPi, potentially leading to the identification of predictive biomarkers of response to their combination with ICIs.

A Pair of Prognostic Biomarkers in Triple-Negative Breast Cancer: KLK10 and KLK11 mRNA Expression

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with poor patient prognosis and limited therapeutic options. A lack of prognostic biomarkers and therapeutic targets fuels the need for new approaches to tackle this severe disease. Extracellular matrix degradation, release, and modulation of the activity of growth factors/cytokines/chemokines, and the initiation of signaling pathways by extracellular proteolytic networks, have been identified as major processes in the carcinogenesis of breast cancer. Members of the kallikrein-related peptidase (KLK) family contribute to these tumor-relevant processes, and are associated with breast cancer progression and metastasis. In this study, the clinical relevance of mRNA expression of two members of this family, KLK10 and KLK11, has been evaluated in TNBC. For this, their expression levels were quantified in tumor tissue of a large, well-characterized patient cohort (n = 123) via qPCR. Although, in general, the overall expression of both factors are lower in tumor tissue of breast cancer patients (encompassing all subtypes) compared to normal tissue of healthy donors, in the TNBC subtype, expression is even increased. In our cohort, a significant, positive correlation between the expression levels of both KLKs was detected, indicating a coordinate expression mode of these proteases. Elevated KLK10 and KLK11 mRNA levels were associated with poor patient prognosis. Moreover, both factors were found to be independent of other established clinical factors such as age, lymph node status, or residual tumor mass, as determined by multivariable Cox regression analysis. Thus, both proteases, KLK10 and KLK11, may represent unfavorable prognostic factors for TNBC patients and, furthermore, appear as promising potential targets for therapy in TNBC.

Nanobiotherapeutic strategies to target immune microenvironment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the subtype with the least favourable outcomes in breast cancer. Besides chemotherapy, there is a chronic lack of other effective treatments. Advances in omic technologies have liberated us from the ambiguity of TNBC heterogeneity in terms of cancer cell and immune microenvironment in recent years. This new understanding of TNBC pathology has already led to the exploitation of novel nanoparticulate systems, including tumor vaccines, oncolytic viruses, and antibody derivatives. The revolutionary ideas in the therapeutic landscape provide new opportunities for TNBC patients. Translating these experimental medicines into clinical benefit is both appreciated and challenging. In this review, we describe the prospective nanobiotherapy of TNBC that has been developed to overcome clinical obstacles, and provide our vision for this booming field at the overlap of cancer biotherapy and nanomaterial design.

Development and Verification of a Prognostic Ferroptosis-Related Gene Model in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the subtype with the worst prognosis of breast cancer. Ferroptosis, a novel iron-dependent programmed cell death, has an increasingly important role in tumorigenesis and development. However, there is still a lack of research on the relationship between ferroptosis-related genes and the prognosis of TNBC. In this study, we obtained the gene expression profile of TNBC patients and matched clinical data from The Cancer Genome Atlas (TCGA) database. Univariate Cox analysis was used to screen out ferroptosis-related genes associated with TNBC prognosis. Then, the least absolute shrinkage and selection operator (LASSO) regression analysis was employed to establish a prognostic prediction model. A 15-ferroptosis-related gene prognostic prediction model was developed, which classified patients into low-risk (LR) or high-risk (HR) groups. Kaplan-Meier analysis results showed that the prognosis of the LR group was better. The receiver operating characteristic (ROC) curve also confirmed the satisfactory predictive ability of this model. Evaluation of the immune microenvironment of TNBC patients in the HR and LR group suggested these 15 ferroptosis-related genes might affect the prognosis of TNBC by regulating the tumor microenvironment. Our prognostic model can provide a theoretical basis for accurate prognosis prediction of TNBC in clinical practice.

PARP-1 Expression and BRCA1 Mutations in Breast Cancer Patients' CTCs

Simple Summary

Recent estimates have shown that approx. 70% of individuals with BRCA1 mutations will develop breast cancer by the age of 70. To make matters worse, breast cancer patients with BRCA1 mutations are more likely to have the more aggressive triple-negative breast cancer. PARPs, belong to a family of nuclear enzymes, which are involved in many cellular processes, including DNA repair. PARP inhibitors have been approved for the treatment of BRCA-mutated breast cancer. The aim of the study was the determination of PARP-1 expression in the context of the presence of BRCA1 mutations in circulating tumor cells of breast cancer patients. PARP-1 (nuclear) expression and BRCA1 mutations were mainly detected in triple negative breast cancer patients, and the latter were correlated with decreased survival. Our data suggest that PARP-1, in conjunction with BRCA1, could potentially be used as (a) biomarker(s) for patients’ stratification.

Abstract

BRCA1 and PARP are involved in DNA damage repair pathways. BRCA1 mutations have been linked to higher likelihood of triple negative breast cancer (TNBC). The aim of the study was to determine PARP-1 expression and BRCA1 mutations in circulating tumor cells (CTCs) of BC patients. Fifty patients were enrolled: 23 luminal and 27 TNBC. PARP expression in CTCs was identified by immunofluorescence. Genotyping was performed by PCR-Sanger sequencing in the same samples. PARP-1 expression was higher in luminal (61%) and early BC (54%), compared to TNBC (41%) and metastatic (33%) patients. In addition, PARP-1 distribution was mostly cytoplasmic in luminal patients (p = 0.024), whereas it was mostly nuclear in TNBC patients. In cytokeratin (CK)-positive patients, those with the CK⁺PARP⁺ phenotype had longer overall survival (OS, log-rank p = 0.046). Overall, nine mutations were detected; M1 and M2 were completely new and M4, M7 and M8 were characterized as pathogenic. M7 and M8 were predominantly found in metastatic TNBC patients (p = 0.014 and p = 0.002). Thus, PARP-1 expression and increased mutagenic burden in TNBC patients’ CTCs, could be used as an indicator to stratify patients regarding therapeutic approaches.

Homologous Recombination Deficiency (HRD) and BRCA 1/2 Gene Mutation for Predicting the Effect of Platinum-Based Neoadjuvant Chemotherapy of Early-Stage Triple-Negative Breast Cancer (TNBC): A Systematic Review and Meta-Analysis

BACKGROUND

Platinum-based agents may benefit patients with triple-negative breast cancer (TNBC) whose tumors are dysfunctional in DNA repair mechanisms associated with the homologous recombination repair (HRR) genes. The purpose of this meta-analysis was to assess the values of BRCA1/2 and homologous recombination deficiency (HRD) in the prediction of the pathological complete response (pCR) rates of patients with TNBC treated with platinum-based neoadjuvant chemotherapy (NAC).

PATIENTS AND METHODS

Patients with TNBC with BRCA or HRD status from platinum-based NAC trials were analyzed. The odds ratios (ORs) with 95% confidence intervals (CI) for the identified studies were calculated.

RESULTS

13 eligible studies between January 2000 and September 2021 were included through systematic literature searches of Embase, PubMed, Cochrane, and Web of Science databases. In 12 trials with BRCA status, 629 of 1266 (49.7%) patients with TNBC achieved pCR with platinum-based NAC, including 134 out of 222 (60.4%) BRCA1/2-mutated patients and 495 out of 1044 (47.4%) BRCA wildtype patients (OR, 1.62; 95% CI, 1.20-2.20). The prevalence of HRD was higher than BRCA1/2 mutations in patients with TNBC (69.2% vs. 17.5%). In six trials with HRD information, pCR rates of HRD-positive patients with TNBC were significantly higher than those of HRD-negative patients with TNBC (241/412, 58.5% vs. 60/183, 32.8%, OR, 3.01; 95% CI, 2.07-4.39, p < 0.001).

CONCLUSIONS

BRCA1/2-mutated and HRD-positive patients with TNBC could benefit from platinum-based NAC. In the future, a prospective study using unified HRD testing criteria is warranted for further investigation.

Therapeutic potential of the PI3K inhibitor LY294002 and PARP inhibitor Talazoparib combination in BRCA-deficient triple negative breast cancer cells

Poly (ADP-ribose) polymerase (PARP) inhibitors provide a promising therapeutic strategy for triple-negative breast cancers (TNBCs) with BRCA1/2 mutation. However, acquire resistance mechanisms and genetic alterations limit the clinical efficacy of PARP inhibitors. The aberrant activation of phosphatidylinositol 3-kinase (PI3K) is a significant problem for cancer development and thus the inhibition of PI3K by PI3K inhibitors is a novel targeted therapy in advanced breast cancer. Here, we, for the first time, investigated that the combined inhibition of PARP by Talazoparib (TAL) and PI3K by LY294002 synergistically inhibited proliferation of BRCA1 mutant HCC1937 TNBC cells through apoptosis, G0/G1 arrest, oxidative stress and increased DNA damage compared to drug alone. Additionally, TAL and LY294002 combination could be a promising strategy for overcoming TAL resistance. Co-treatment of TAL with LY294002 considerably suppressed the activation of PI3K, Akt1 and mTOR expression and phosphorylated protein levels in TNBC cells and caused changes in the multiple kinase phosphorylation. Our findings revealed that the dual inhibition of PARP and PI3K might represent an effective therapeutic strategy for TNBC and potentially overcome TAL resistance.