Association of BRCA1- and BRCA2-deficiency with mutation burden, expression of PD-L1/PD-1, immune infiltrates, and T cell-inflamed signature in breast cancer

CD105+ fibroblasts support an immunosuppressive niche in women at high risk of breast cancer initiation

BACKGROUND

Aging is the greatest risk factor for breast cancer, and although epithelial cells are the source of carcinomas, epithelial changes alone do not fully explain cancer susceptibility. Fibroblasts and macrophages are key stromal constituents around the cells of origin for cancer in breast tissue. With age, macrophages surrounding terminal ductal lobular units (TDLUs) become increasingly immunosuppressive. CD105+ fibroblasts intercalate within TDLUs, drive luminal differentiation, and give rise to immunosuppressive cancer-associated fibroblasts in other tissues. We propose that differences in fibroblasts are a crucial component of the stroma that shapes cancer susceptibility.

METHODS

Primary peri-epithelial fibroblast cultures were established from prophylactic and reduction mammoplasties from 30 women ranging in age from 16 to 70 years and from BRCA1 mutation carriers. Growth characteristics, transcriptional profiles, differentiation potential, and secreted proteins were profiled for fibroblast subtypes from diverse donors. Co-cultures with fibroblasts, macrophages, and T cells were used to ascertain the functional role played by CD105+ fibroblasts in immune cell modulation.

RESULTS

We found that peri-epithelial CD105+ fibroblasts are enriched in older women as well as women who carry BRCA1 mutations. These CD105+ fibroblasts exhibit robust adipogenesis and secrete factors related to macrophage polarization. Macrophages cocultured with fibroblasts better maintain or enhance polarization states than media alone. CD105+ fibroblasts increased expression of immunosuppressive macrophage genes. CD105+ fibroblasts supported anti-inflammatory macrophage-mediated suppression of T cell proliferation, whereas CD105- fibroblasts significantly reduced the suppressive effect of anti-inflammatory macrophages on T cell proliferation.

CONCLUSIONS

Establishment of a coculture system to dissect the molecular circuits between CD105+ fibroblasts and macrophages that drive immunosuppressive macrophage polarization has broad utility in understanding mammary gland development and events that precede cancer initiation. CD105+ fibroblasts and macrophages may coordinate to suppress immunosurveillance and increase breast cancer susceptibility.

Advances in TIL therapy: Expanding the horizons beyond melanoma

Tumor-infiltrating lymphocyte (TIL) therapy represents a breakthrough in solid tumor treatment, addressing unmet needs for patients with limited options. While its efficacy is established in advanced melanoma, TIL therapy shows early promise in non-small cell lung cancer, breast cancer, gynecological cancers, and head and neck cancers. However, challenges such as reduced T cell infiltration, lower tumor mutational burden (TMB), immunosuppressive tumor microenvironments (TME), and toxicity associated with the TIL therapy regimen hinder its broader application in these patient groups, compared with melanoma. To address these challenges, new approaches focus on the selection of tumor-reactive TIL, optimization of TIL expansion, combination of immune checkpoint inhibitors with TIL therapy to counteract immunosuppressive microenvironments, and genetic modification of TIL to enhance persistence and functionality. Larger clinical trials are essential to validate these innovations and standardize protocols. With continued advancements, TIL therapy has the potential to redefine the treatment landscape for advanced solid cancers.

Pancancer analysis of DNA damage repair gene mutations and their impact on immune regulatory gene expression

DNA damage is a key factor in many human disorders, including cancer, chronic inflammation, and early aging. Genes involved in DNA damage repair (DDR) not only maintain genomic stability but also contribute to immune responses by regulating the expression of antimicrobial peptides and ligands that activate immune receptors. Various components of the DNA damage response (DDR), including DNA damage sensors, transducer kinases, and effector proteins, are capable of activating diverse immunological signaling pathways. While DDR gene mutations are common in cancers, their effects on immune characteristics are not well understood. We investigated how mutations in DDR genes influence the expression of immune regulatory genes, including immune stimulators, inhibitors, and genes related to the major histocompatibility complex (MHC) pathway. Using gene expression data from The Cancer Genome Atlas (TCGA) and mutation data from cBioPortal, we analyzed 264 DDR-related genes and 66 immune regulatory genes. These genes were clustered and categorized using Metascape, an integrative bioinformatics tool that applies enrichment-based analysis to group functionally related genes into clusters. The clustered genes were further validated through a literature review and the GeneCards database. We scored the change in immune regulatory gene expression in response to DDR gene mutations to identify differentially expressed immune stimulators, inhibitors, and MHC-related genes. Our analysis revealed positive and negative correlations between DDR gene mutations and the expression of immune modulators. These findings could help guide future cancer treatments based on biomarkers and immunotherapy strategies.

CD105+ fibroblasts support an immunosuppressive niche in women at high risk of breast cancer initiation

BACKGROUND

Aging is the greatest risk factor for breast cancer, and although epithelial cells are the source of carcinomas, epithelial changes alone do not fully explain cancer susceptibility. Fibroblasts and macrophages are key stromal constituents around the cells of origin for cancer in breast tissue. With age, macrophages surrounding terminal ductal lobular units (TDLUs) become increasingly immunosuppressive. CD105 + fibroblasts intercalate within TDLUs, drive luminal differentiation, and give rise to immunosuppressive cancer-associated fibroblasts in other tissues. We propose that differences in fibroblasts are a crucial component of the stroma that shapes cancer susceptibility.

METHODS

Primary fibroblast cultures were established from prophylactic and reduction mammoplasties from women ranging in age from 16 to 70 years and breast cancer risk ( BRCA1 mutation carriers). Growth characteristics, transcriptional profiles, differentiation potential, and secreted proteins were profiled for fibroblast subtypes from diverse donors. Co-cultures with fibroblasts, monocytes, macrophages, and T cells were used to ascertain the functional role played by CD105 + fibroblasts in immune cell modulation.

RESULTS

We found that peri-epithelial CD105 + fibroblasts are enriched in older women as well as women who carry BRCA1 mutations. These CD105 + fibroblasts exhibit robust adipogenesis and secrete factors related to macrophage polarization. Macrophages cocultured with fibroblasts better maintain or enhance polarization states than media alone. CD105 + fibroblasts increased expression of immunosuppressive macrophage genes. CD105 + fibroblasts supported anti-inflammatory macrophage-mediated suppression of T cell proliferation, whereas CD105 - fibroblasts significantly reduced the suppressive effect of anti-inflammatory macrophages on T cell proliferation.

CONCLUSIONS

Establishment of a coculture system to dissect the molecular circuits between CD105 + fibroblasts and macrophages that drive immunosuppressive macrophage polarization has broad utility in understanding mammary gland development and events that precede cancer initiation. CD105 + fibroblasts and macrophages may coordinate to suppress immunosurveillance and increase breast cancer susceptibility.

Thirty Years of BRCA1: Mechanistic Insights and Their Impact on Mutation Carriers

SIGNIFICANCE

Here, we explore the impact of three decades of BRCA1 research on the lives of mutation carriers and propose strategies to improve the prevention and treatment of BRCA1-associated cancer.

The Tumour Microenvironment and Epigenetic Regulation in BRCA1 Pathogenic Variant-Associated Breast Cancers

Background/Objectives: BRCA1 pathogenic variant (PV)-associated breast cancers are most commonly seen in hereditary genetic conditions such as the autosomal-dominant Hereditary Breast and Ovarian Cancer (HBOC) syndrome, and rarely in sporadic breast cancer. Such breast cancers tend to exhibit greater aggressiveness and poorer prognoses due to the influence of BRCA1 pathogenic variants (PVs) on the tumour microenvironment. Additionally, while the genetic basis of BRCA1 PV breast cancer is well-studied, the role of epigenetic mediators in the tumourigenesis of these hereditary breast cancers is also worth exploring. Results: PVs in the BRCA1 gene interact with stromal cells and immune cells, promoting epithelial-mesenchymal transition, angiogenesis, and affecting oestrogen levels. Additionally, BRCA1 PVs contribute to breast cancer development through epigenetic effects on cells, including DNA methylation and histone acetylation, leading to the suppression of proto-oncogenes and dysregulation of cytokines. In terms of epigenetics, lysine-specific demethylase 1 (LSD-1) is considered a master epigenetic regulator, governing both transcriptional repression and activation. It exerts epigenetic control over BRCA1 and, to a lesser extent, BRCA2 genes. The upregulation of LSD-1 is generally associated with a poorer prognosis in cancer patients. In the context of breast cancer in BRCA1/2 PV carriers, LSD-1 contributes to tumour development through various mechanisms. These include the maintenance of a hypoxic environment and direct suppression of BRCA1 gene expression. Conclusions: While LSD-1 itself does not directly cause mutations in BRCA1 or BRCA2 genes, its epigenetic influence sheds light on the potential role of LSD-1 inhibitors as a therapeutic approach in managing breast cancer, particularly in individuals with BRCA1/2 PVs. Targeting LSD-1 may help counteract its detrimental effects and provide a promising avenue for therapy in this specific subgroup of breast cancer.

Genomic instability as a driver and suppressor of anti-tumor immunity

Genomic instability is a driver and accelerator of tumorigenesis and influences disease outcomes across cancer types. Although genomic instability has been associated with immune evasion and worsened disease prognosis, emerging evidence shows that genomic instability instigates pro-inflammatory signaling and enhances the immunogenicity of tumor cells, making them more susceptible to immune recognition. While this paradoxical role of genomic instability in cancer is complex and likely context-dependent, understanding it is essential for improving the success rates of cancer immunotherapy. In this review, we provide an overview of the underlying mechanisms that link genomic instability to pro-inflammatory signaling and increased immune surveillance in the context of cancer, as well as discuss how genomically unstable tumors evade the immune system. A better understanding of the molecular crosstalk between genomic instability, inflammatory signaling, and immune surveillance could guide the exploitation of immunotherapeutic vulnerabilities in cancer.

Advances in siRNA Drug Delivery Strategies for Targeted TNBC Therapy

Among breast cancers, triple-negative breast cancer (TNBC) has been recognized as the most aggressive type with a poor prognosis and low survival rate. Targeted therapy for TNBC is challenging because it lacks estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Chemotherapy, radiation therapy, and surgery are the common therapies for TNBC. Although TNBC is prone to chemotherapy, drug resistance and recurrence are commonly associated with treatment failure. Combination therapy approaches using chemotherapy, mAbs, ADC, and antibody-siRNA conjugates may be effective in TNBC. Recent advances with siRNA-based therapy approaches are promising for TNBC therapy with better prognosis and reduced mortality. This review discusses advances in nanomaterial- and nanobiomaterial-based siRNA delivery platforms for TNBC therapy exploring targeted therapy approaches for major genes, proteins, and TFs upregulated in TNBC tumors, which engage in molecular pathways associated with low TNBC prognosis. Bioengineered siRNA drugs targeting one or several genes simultaneously can downregulate desired genes, significantly reducing disease progression.

Targeting cytotoxic lymphocyte antigen 4 (CTLA-4) in breast cancer

Breast cancer (BC) has a high mortality rate and is one of the most common malignancies in the world. Initially, BC was considered non-immunogenic, but a paradigm shift occurred with the discovery of tumor-infiltrating lymphocytes (TILs) and regulatory T cells (Tregs) in the BC tumor microenvironment. CTLA-4 (Cytotoxic T-lymphocyte-associated protein 4) immunotherapy has emerged as a treatment option for BC, but it has limitations, including suboptimal antitumor effects and toxicity. Research has demonstrated that anti-CTLA-4 combination therapies, such as Treg depletion, cancer vaccines, and modulation of the gut microbiome, are significantly more effective than CTLA-4 monoclonal antibody (mAB) monotherapy. Second-generation CTLA-4 antibodies are currently being developed to mitigate immune-related adverse events (irAEs) and augment antitumor efficacy. This review examines anti-CTLA-4 mAB in BC, both as monotherapy and in combination with other treatments, and sheds light on ongoing clinical trials, novel CTLA-4 therapeutic strategies, and potential utility of biomarkers in BC.

A murine model to evaluate immunotherapy effectiveness for human Fanconi anemia-mutated acute myeloid leukemia

Fanconi anemia (FA)-mutated acute myeloid leukemia (AML) is a secondary AML with very poor prognosis and limited therapeutic options due to increased sensitivity to DNA-damaging agents. PD-1 immune checkpoint inhibitors upregulate T-cell killing of cancer cells and is a class of promising treatment for FA-AML. Here, we developed a novel FA-AML murine model that allows the study of human AML with a humanized immune system in order to investigate immunotherapeutic treatments in vivo. FA-AML1 cells and non-FA-mutated Kasumi-1 cells were injected into 8-10 week old NSG mice. Once leukemic engraftment was confirmed by HLA-DR expression in the peripheral blood, human peripheral blood mononuclear cells (hPBMCs) were injected into the mice. One week post-hPBMCs injection, Nivolumab (PD-1 inhibitor) or PBS vehicle control was administered to the mice bi-weekly. In our Nivolumab treated mice, FA-AML1, but not Kasumi-1-engrafted mice, had significantly prolonged overall survival. Both FA-AML1 and Kasumi-1 engrafted mice had decreased spleen weights. Higher leukemic infiltration into vital organs was observed in FA-AML1 engrafted mice compared to Kasumi-1 engrafted mice. In conclusion, our novel humanized murine model of FA-mutated AML is an attractive tool for supporting further studies and clinical trials using PD-1 inhibitors to treat FA-mutated AML.

Gender-Specific Genetic Predisposition to Breast Cancer: BRCA Genes and Beyond

Among neoplastic diseases, breast cancer (BC) is one of the most influenced by gender. Despite common misconceptions associating BC as a women-only disease, BC can also occur in men. Additionally, transgender individuals may also experience BC. Genetic risk factors play a relevant role in BC predisposition, with important implications in precision prevention and treatment. The genetic architecture of BC susceptibility is similar in women and men, with high-, moderate-, and low-penetrance risk variants; however, some sex-specific features have emerged. Inherited high-penetrance pathogenic variants (PVs) in BRCA1 and BRCA2 genes are the strongest BC genetic risk factor. BRCA1 and BRCA2 PVs are more commonly associated with increased risk of female and male BC, respectively. Notably, BRCA-associated BCs are characterized by sex-specific pathologic features. Recently, next-generation sequencing technologies have helped to provide more insights on the role of moderate-penetrance BC risk variants, particularly in PALB2, CHEK2, and ATM genes, while international collaborative genome-wide association studies have contributed evidence on common low-penetrance BC risk variants, on their combined effect in polygenic models, and on their role as risk modulators in BRCA1/2 PV carriers. Overall, all these studies suggested that the genetic basis of male BC, although similar, may differ from female BC. Evaluating the genetic component of male BC as a distinct entity from female BC is the first step to improve both personalized risk assessment and therapeutic choices of patients of both sexes in order to reach gender equality in BC care. In this review, we summarize the latest research in the field of BC genetic predisposition with a particular focus on similarities and differences in male and female BC, and we also discuss the implications, challenges, and open issues that surround the establishment of a gender-oriented clinical management for BC.

BRCA1 and BRCA2 deficient tumour models generate distinct ovarian tumour microenvironments and differential responses to therapy

Clinical trials are currently exploring combinations of PARP inhibitors and immunotherapies for the treatment of ovarian cancer, but their effects on the ovarian tumour microenvironment (TME) remain unclear. Here, we investigate how olaparib, PD-L1 monoclonal antibodies, and their combination can influence TME composition and survival of tumour-bearing mice. We further explored how BRCA deficiencies can influence the response to therapy. Olaparib and combination therapies similarly improved the median survival of Brca1- and Brca2-deficient tumour-bearing mice. Anti-PD-L1 monotherapy improved the survival of mice with Brca1-null tumours, but not Brca2-null tumours. A detailed analysis of the TME revealed that olaparib monotherapy resulted in a large number of immunosuppressive and immunomodulatory effects in the more inflamed Brca1-deficient TME but not Brca2-deficient tumours. Anti-PD-L1 treatment was mostly immunosuppressive, resulting in a systemic reduction of cytokines and a compensatory increase in PD-L1 expression. The results of the combination therapy generally resembled the effects of one or both of the monotherapies, along with unique changes observed in certain immune populations. In-silico analysis of RNA-seq data also revealed numerous differences between Brca-deficient tumour models, such as the expression of genes involved in inflammation, angiogenesis and PD-L1 expression. In summary, these findings shed light on the influence of novel therapeutics and BRCA mutations on the ovarian TME.

Detection and therapeutic implications of homologous recombination repair deficiency in pancreatic cancer: a narrative review

Background and Objective

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal cancers. A major recent advance has been the identification of a subset of patients with PDAC who harbor inherited or somatic genetic alterations that result in homologous recombination deficiency (HRD) in tumor cells. These patients often respond favorably to drugs that can exploit this vulnerability. This review outlines the biomarkers that have been developed to predict HRD and their performance related specifically to PDAC, as well as novel HRD-targeted therapies for PDAC.

Methods

We conducted a narrative review of the HRD in PDAC based on PubMed, Google Scholar, website and citation searches.

Key Content and Findings

Germline mutations in BRCA1 and BRCA2 remains the only validated biomarker for the HRD state but various platforms are now available to define HRD beyond BRCA1/2 alterations. Currently, the available evidence supports the use of platinum-based chemotherapy as well as PARP inhibitors, and there is also emerging data that immune checkpoint inhibitors can produce some durable responses in these patients.

Conclusions

Consistently detecting clinically significant the HRD status in PDAC has remained challenging with current commercially available platforms. Multiple novel HRD-targeted therapies for PDAC are currently in development and clinical trials, offering new opportunities for these patients.

A BRCA2 germline mutation and high expression of immune checkpoints in a TNBC patient

Triple-negative breast cancer (TNBC) is the most aggressive subtype of mammary carcinoma. Here, we describe a case of an 81-year-old female diagnosed with ductal triple negative breast cancer with a germline pathogenic variant in BReast CAncer gene2 (BRCA2). Genetic testing also revealed the presence of four somatic mutations in the ephrin type-A receptor 3 (EphA3), TP53, BRCA1-associated protein (BAP1), and MYB genes. The BRCA2, TP53, and BAP1 gene mutations are highly predictive of a defective homologous recombination repair system and subsequent chromosomal instability in this patient. Coherently, the patient displayed a strong homologous recombination deficiency signature and high tumor mutational burden status, which are generally associated with increased probability of immune neoantigens formation and presentation, and with tumor immunogenicity. Analysis of immune checkpoint revealed high expression of programmed cell death ligand 1 (PD-L1), programmed cell death ligand 2 (PD-L2), programmed death 1 (PD1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA 4), suggesting that the patient might likely benefit from immunotherapies. Altogether, these findings support an unveiled link between BRCA2 inactivation, HR deficiency and increased expression of immune checkpoints in TNBC. This clinical case highlights the importance of screening TNBC patients for genetic mutations and TMB biomarkers in order to predict the potential efficacy of immunotherapy.

βhCG mediates immune suppression through upregulation of CD11b+ Gr1+ myeloid derived suppressor cells, CD206+ M2 macrophages, and CD4+ FOXP3+ regulatory T-cells in BRCA1 deficient breast cancers

BRCA1 mutation is reported in about 70% of all triple negative breast cancers (TNBC), while BRCA1 defect due to promoter hypermethylation is seen in about 30%-60% of sporadic breast cancers. Although PARP inhibitors and platinum-based chemotherapy are used to treat these cancers, more efficient therapeutic approaches are required to overcome the resistance to treatment. Our previous findings have reported elevated βhCG expression but not αhCG in BRCA1 deficient breast cancers. As βhCG causes immune suppression in pregnancy, this study explored the immunomodulatory effect of βhCG in BRCA1mutated/deficient TNBC. We observed that Th1, Th2, and Th17 cytokines are upregulated in the presence of βhCG in BRCA1 defective cancers. In NOD-SCID and syngeneic mouse models, βhCG increases the frequency of Myeloid-derived suppressor cells in tumour tissues and contributes to macrophage reprogramming from antitumor M1 to pro-tumour M2 phenotype. βhCG reduces the CD4+ T-cell infiltration while increasing the density of CD4+ CD25+ FOXP3+ regulatory T-cell in BRCA1 deficient tumour tissues. In contrast, xenograft tumours with βhCG knocked down TNBC cells did not show these immune suppressive effects. We have also shown that βhCG upregulates pro-tumorigenic markers arginase1(Arg1), inducible nitric oxide synthase, PD-L1/PD-1, and NFκB in BRCA1 defective tumours. Thus, for the first time, this study proves that βhCG suppresses the host antitumor immune response and contributes to tumour progression in BRCA1 deficient tumours. This study will help develop new immunotherapeutic approaches for treating BRCA1 defective TNBC by regulating βhCG.

The current advances of lncRNAs in breast cancer immunobiology research

Breast cancer is the most frequently diagnosed malignancy and the leading cause of cancer-related death in women worldwide. Breast cancer development and progression are mainly associated with tumor-intrinsic alterations in diverse genes and signaling pathways and with tumor-extrinsic dysregulations linked to the tumor immune microenvironment. Significantly, abnormal expression of lncRNAs affects the tumor immune microenvironment characteristics and modulates the behavior of different cancer types, including breast cancer. In this review, we provide the current advances about the role of lncRNAs as tumor-intrinsic and tumor-extrinsic modulators of the antitumoral immune response and the immune microenvironment in breast cancer, as well as lncRNAs which are potential biomarkers of tumor immune microenvironment and clinicopathological characteristics in patients, suggesting that lncRNAs are potential targets for immunotherapy in breast cancer.

Immune environment and antigen specificity of the T cell receptor repertoire of malignant ascites in ovarian cancer

We evaluated the association of disease outcome with T cell immune-related characteristics and T cell receptor (TCR) repertoire in malignant ascites from patients with high-grade epithelial ovarian cancer. Ascitic fluid samples were collected from 47 high-grade epithelial ovarian cancer patients and analyzed using flow cytometry and TCR sequencing to characterize the complementarity determining region 3 TCR β-chain. TCR functions were analyzed using the McPAS-TCR and VDJ databases. TCR clustering was implemented using Grouping of Lymphocyte Interactions by Paratope Hotspots software. Patients with poor prognosis had ascites characterized by an increased ratio of CD8+ T cells to regulatory T cells, which correlated with an increased productive frequency of the top 100 clones and decreased productive entropy. TCRs enriched in patients with an excellent or good prognosis were more likely to recognize cancer antigens and contained more TCR reads predicted to recognize epithelial ovarian cancer antigens. In addition, a TCR motif that is predicted to bind the TP53 neoantigen was identified, and this motif was enriched in patients with an excellent or good prognosis. Ascitic fluid in high-grade epithelial ovarian cancer patients with an excellent or good prognosis is enriched with TCRs that may recognize ovarian cancer-specific neoantigens, including mutated TP53 and TEAD1. These results suggest that an effective antigen-specific immune response in ascites is vital for a good outcome in high-grade epithelial ovarian cancer.

Immune cells are increased in normal breast tissues of BRCA1/2 mutation carriers

PURPOSE

Breast cancer risk is elevated in pathogenic germline BRCA 1/2 mutation carriers due to compromised DNA quality control. We hypothesized that if immunosurveillance promotes tumor suppression, then normal/benign breast lobules from BRCA carriers may demonstrate higher immune cell densities.

METHODS

We assessed immune cell composition in normal/benign breast lobules from age-matched women with progressively increased breast cancer risk, including (1) low risk: 19 women who donated normal breast tissue to the Komen Tissue Bank (KTB) at Indiana University Simon Cancer Center, (2) intermediate risk: 15 women with biopsy-identified benign breast disease (BBD), and (3) high risk: 19 prophylactic mastectomies from women with germline mutations in BRCA1/2 genes. We performed immunohistochemical stains and analysis to quantitate immune cell densities from digital images in up to 10 representative lobules per sample. Median cell counts per mm2 were compared between groups using Wilcoxon rank-sum tests.

RESULTS

Normal/benign breast lobules from BRCA carriers had significantly higher densities of immune cells/mm2 compared to KTB normal donors (all p < 0.001): CD8 + 354.4 vs 150.9; CD4 + 116.3 vs 17.7; CD68 + 237.5 vs 57.8; and CD11c + (3.5% vs 0.4% pixels positive). BBD tissues differed from BRCA carriers only in CD8 + cells but had higher densities of CD4 + , CD11c + , and CD68 + immune cells compared to KTB donors.

CONCLUSIONS

These preliminary analyses show that normal/benign breast lobules of BRCA mutation carriers contain increased immune cells compared with normal donor breast tissues, and BBD tissues appear overall more similar to BRCA carriers.

Therapeutic Targeting of DNA Damage Repair in the Era of Precision Oncology and Immune Checkpoint Inhibitors

Cancer manifestation is a multistep process involving accumulation of various genetic and epigenetic changes that results in oncogenic "hallmarks of cancer" processes including genomic instability. Exploitation of aberrant DNA-damage response (DDR) mechanisms in cancer is in part a goal of many therapeutic strategies, and recent evidence supports the role of targeting DDR in modulating the tumor immune microenvironment to enhance immunotherapeutic response. Improved cancer profiling, including next-generation and whole-genome mutational sequencing of tumor tissue, as well as circulating nucleic acids, has enhanced our understanding of the genetic and epigenetic molecular mechanisms in tumorigenesis and will become fundamental to precisely target tumors and achieve cancer control. With the successes of poly(ADP-ribose) polymerase inhibitors (PARPi) and immunotherapies, the intersection of DDR molecular machinery and corresponding antitumor immune response has gained much interest with a focus on achieving therapeutic synergy using DNA damage-targeting agents and immunotherapy. In this review, we provide a bench-to-bedside overview of the fundamentals of DDR signaling and repair as they relate to cancer therapeutic strategies including novel DDR-targeting agents. We also discuss the underlying mechanisms that link DDR signaling to antitumor immunity and immunotherapy efficacy, and how this knowledge can be used to improve precision medicine approaches in the treatment of cancer.

The potential of PARP inhibitors in targeted cancer therapy and immunotherapy

DNA damage response (DDR) deficiencies result in genome instability, which is one of the hallmarks of cancer. Poly (ADP-ribose) polymerase (PARP) enzymes take part in various DDR pathways, determining cell fate in the wake of DNA damage. PARPs are readily druggable and PARP inhibitors (PARPi) against the main DDR-associated PARPs, PARP1 and PARP2, are currently approved for the treatment of a range of tumor types. Inhibition of efficient PARP1/2-dependent DDR is fatal for tumor cells with homologous recombination deficiencies (HRD), especially defects in breast cancer type 1 susceptibility protein 1 or 2 (BRCA1/2)-dependent pathway, while allowing healthy cells to survive. Moreover, PARPi indirectly influence the tumor microenvironment by increasing genomic instability, immune pathway activation and PD-L1 expression on cancer cells. For this reason, PARPi might enhance sensitivity to immune checkpoint inhibitors (ICIs), such as anti-PD-(L)1 or anti-CTLA4, providing a rationale for PARPi-ICI combination therapies. In this review, we discuss the complex background of the different roles of PARP1/2 in the cell and summarize the basics of how PARPi work from bench to bedside. Furthermore, we detail the early data of ongoing clinical trials indicating the synergistic effect of PARPi and ICIs. We also introduce the diagnostic tools for therapy development and discuss the future perspectives and limitations of this approach.

Tumor infiltrating CD8/CD103/TIM-3-expressing lymphocytes in epithelial ovarian cancer co-express CXCL13 and associate with improved survival

Reactivation of tumor infiltrating T lymphocytes (TILs) with immune checkpoint inhibitors or co-stimulators has proven to be an effective anti-cancer strategy for a broad range of malignancies. However, epithelial ovarian cancer (EOC) remains largely refractory to current T cell-targeting immunotherapeutics. Therefore, identification of novel immune checkpoint targets and biomarkers with prognostic value for EOC is warranted. Combining multicolor immunofluorescent staining’s with single cell RNA-sequencing analysis, we here identified a TIM-3/CXCL13-positive tissue-resident memory (CD8/CD103-positive) T cell (Trm) population in EOC. Analysis of a cohort of ~175 patients with high-grade serous EOC revealed TIM-3-positive Trm were significantly associated with improved patient survival. As CXCL13-positive CD8-positive T cells have been strongly linked to patient response to anti-PD1 immune checkpoint blockade, combinatorial TIM-3 and PD-1 blockade therapy may be of interest for the (re)activation of anti-cancer immunity in EOC.

Serendipitous synergism - an exceptional response to treatment with pembrolizumab in the course of a natural immunovirotherapy: a case report and review of the literature

Immune checkpoint inhibitors (ICIs) are the current guideline recommended treatment for many malignancies considered to be terminal. Despite considerable advances, their utility remains limited, and the field requires synergistic partners to further improve outcomes. Oncolytic viruses (OV) are emerging as contenders for the role of the synergistic agent of choice due to their multi-mechanistic effect on activating the tumor 'cold' immune microenvironment. Herpes simplex virus 1, a naturally selective OV, is the most advanced virotherapeutic compound in clinical applications for use in combination with ICI. We here present the case of a 72 year-old patient with a heavily pre-treated, advanced maxillary sinus squamous cell cancer with distant metastases who developed complete response (CR) with only three administrations of a programmed death 1 inhibitor after treatment interference by a severe herpes zoster infection, based on the related alpha-herpesvirus varicella zoster virus (VZV). This exceptional response has been followed and confirmed with imaging studies over more than 5 years. Although the patient had several favorable predictors for response to immunotherapy, we reason that the exceptional response may in part be secondary to the serendipitous VZV infection. Documented cases of cancer patients that achieved CR after few administrations of treatment with ICI are rare, with most reporting follow up of just over 1 year or less. In this case, it is conceivable that the interference of the infection with VZV, soon after the start of immunotherapy with ICI, led to a lasting antitumor immunity and sustained CR. This hypothesis is supported by the concept of 'oncolytic immunotherapy' which is reviewed in this manuscript. In addition, persistence of a TP53 mutation found in a liquid biopsy, despite clinical and radiologic remission, is discussed.

Pro-Inflammatory and Anti-Inflammatory Salivary Cytokines in Breast Cancer: Relationship with Clinicopathological Characteristics of the Tumor

The aim of the work was to compare the salivary cytokine profile of breast cancer patients with the clinicopathological characteristics of the tumor. The study included 113 patients with breast cancer (main group, mean age 54.1 years) and 111 patients with breast fibroadenomas (control group, mean age 56.7 years). Before treatment, saliva samples were collected from all patients and the content of cytokines (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-18, MCP-1, and TNF-α) was determined. The content of cytokines in saliva correlates well with the clinicopathological characteristics of breast cancer. The level of all salivary cytokines increases at advanced stages of breast cancer and at a low degree of tumor differentiation. The exception is MCP-1, for which there is an extremely high content for well-differentiated breast cancer. A statistically significant increase in the content of MCP-1, IL-1β, IL-2, IL-4, and IL-10 was found in triple-negative breast cancer. For the first time, the correlation of salivary levels of TNF-α, IL-1β, and IL-6 with HER2 status, MCP-1, IL-1β, IL-2, and IL-4 with the hormonal status of the tumor was shown. The relationship between the level of IL-2, IL-10, and IL-18 in saliva with the level of Ki-67 expression has been established.

The role of DNA damage repair (DDR) system in response to immune checkpoint inhibitor (ICI) therapy

As our understanding of the mechanisms of cancer treatment has increased, a growing number of studies demonstrate pathways through which DNA damage repair (DDR) affects the immune system. At the same time, the varied response of patients to immune checkpoint blockade (ICB) therapy has prompted the discovery of various predictive biomarkers and the study of combination therapy. Here, our investigation explores the interactions involved in combination therapy, accompanied by a review that summarizes currently identified and promising predictors of response to immune checkpoint inhibitors (ICIs) that are useful for classifying oncology patients. In addition, this work, which discusses immunogenicity and several components of the tumor immune microenvironment, serves to illustrate the mechanism by which higher response rates and improved efficacy of DDR inhibitors (DDRi) in combination with ICIs are achieved.

Homologous Recombination Deficiency Scar: Mutations and Beyond-Implications for Precision Oncology

Homologous recombination deficiency (HRD) is a prevalent in approximately 17% of tumors and is associated with enhanced sensitivity to anticancer therapies inducing double-strand DNA breaks. Accurate detection of HRD would therefore allow improved patient selection and outcome of conventional and targeted anticancer therapies. However, current clinical assessment of HRD mainly relies on determining germline BRCA1/2 mutational status and is insufficient for adequate patient stratification as mechanisms of HRD occurrence extend beyond functional BRCA1/2 loss. HRD, regardless of BRCA1/2 status, is associated with specific forms of genomic and mutational signatures termed HRD scar. Detection of this HRD scar might therefore be a more reliable biomarker for HRD. This review discusses and compares different methods of assessing HRD and HRD scar, their advances into the clinic, and their potential implications for precision oncology.

Common Multiple Primary Cancers Associated With Breast and Gynecologic Cancers and Their Risk Factors, Pathogenesis, Treatment and Prognosis: A Review

The mammary gland is closely related to the female reproductive system in many aspects, affecting the whole gynecological system. Breast cancer (BC) is the most common malignancy in women and associated with considerable negative effects. Due to various factors including co-pathogenic genetic mutations, environment factors, lifestyle, behavioral factors, treatment regimens and in-creased survival of patients with BC, there is an increased probability of developing additional primary gynecologic cancers such as ovarian cancer (OC), endometrial cancer (EC), and cervical cancer (CC). More and more studies have been conducted in recent years. Multiple primary cancers (MPCs), also known as multiple primary malignancies, refers to two or more different primary cancers in the same patient occurring in the same or different organs or tissues. The pathogenesis of multiple primary cancers is complex and has a negative effect on the prognosis and survival of patients. This review discusses the common types of BC-associated MPCs, namely, BC associated with OC, BC associated with EC and BC associated with CC, as well as risk factors, pathogenesis, treatment, and prognosis of MPCs associated with breast and gynecologic cancers. It provides new intervention and treatment ideas for patients with BC-associated MPCs to improve quality of life and prognosis.

PD-L1 and PD-L2 expression in pancreatic ductal adenocarcinoma and their correlation with immune infiltrates and DNA damage response molecules

Immunotherapy targeting programmed cell death‐1 (PD‐1) has considerably improved the prognosis of patients with advanced cancers; however, its efficacy in the treatment of pancreatic ductal adenocarcinoma (PDAC) is unfavourable. To address the issue of PDAC immunotherapy, we investigated the expression of two PD‐1 ligands, PD‐L1 and PD‐L2, in PDAC, analysed their role in survival, and explored their correlation with clinicopathological features, immune infiltration, and DNA damage response molecules. Immunohistochemistry was performed on 291 surgically resected PDAC samples. In tumour cells (TCs) and immune cells (ICs), the positivity of PD‐L1 expression was 30 and 20% and that of PD‐L2 expression was 40 and 20%, respectively. Moreover, PD‐L1 expression on TCs correlated with its expression on ICs (p < 0.0001); a similar result was observed for PD‐L2 (p < 0.0001). Nonetheless, no correlation was observed between PD‐L1 and PD‐L2 expression. Positive PD‐L1 expression on TCs was related to N1 stage (p = 0.011) and AJCC II stage (p = 0.002), whereas positive PD‐L2 expression on TCs was associated with high FOXP3⁺ cell infiltration (p = 0.001) and high BRCA2 expression (p < 0.0001). Survival analysis revealed that positive PD‐L1 (p = 0.046) and PD‐L2 (p = 0.028) expression on TCs was an independent risk factor for unfavourable disease‐specific survival (DSS). Furthermore, positive PD‐L2 expression on TCs was an independent risk factor for lower DSS in the pN0 (p = 0.023), moderate and well tumour differentiation (p = 0.004), low BRCA1 (p = 0.017), wild‐type p53 (p = 0.034), and proficient mismatch repair (p = 0.004) subgroups. Moreover, post‐operative adjuvant chemotherapy could significantly affect DSS, regardless of PD‐L1/PD‐L2 expression status (positive or negative) on TCs, while it only prolonged DSS in PDL1‐ICs⁽⁻⁾ (p < 0.0001) and PDL2‐ICs⁽⁻⁾ (p < 0.0001) subgroups. This study provides a comprehensive understanding of the roles of PD‐L1 and PD‐L2 in PDAC, supporting anti‐PD‐1 axis immunotherapy for PDAC.

Analysis of a novel immune checkpoint, Siglec-15, in pancreatic ductal adenocarcinoma

Siglec‐15, a novel immune checkpoint, is an emerging target for next‐generation cancer immunotherapy. However, the role of Siglec‐15 in pancreatic ductal adenocarcinoma (PDAC) remains poorly understood. We investigated the expression of Siglec‐15 and its association with clinicopathological characteristics, programmed cell death‐ligand 1 (PD‐L1), immune cells, and DNA damage repair (DDR) molecules in a cohort of 291 patients with PDAC. Positive tumour cell expression of Siglec‐15 and PD‐L1 was observed in 18.6 and 30.3% of the samples, respectively. We also detected Siglec‐15 positivity in macrophages in 3.4% of patients. Co‐expression of Siglec‐15 with PD‐L1 was observed in 6.1% of the patients. A total of 33 PD‐L1‐negative samples (18.0%) were Siglec‐15‐positive. Siglec‐15 was observed more frequently in moderate‐to‐well‐differentiated tumours. Siglec‐15 was associated with a low density of Tregs and CD45RO T cells, high BRCA1 expression, and improved survival. Both Siglec‐15 and PD‐L1 are independent factors of patient outcomes. The prognostic significance of Siglec‐15 for survival was more discriminative in lymph node‐negative, high BRCA1 expression, or low BRCA2 expression tumours than in lymph node‐positive, low BRCA1 expression, or high BRCA2 expression tumours. In conclusion, we identified Siglec‐15 as a promising predictor for prognosis combined with different DDR molecular statuses and complex tumour‐infiltrating cells in PDAC. Targeting Siglec‐15 may be a novel therapeutic option for patients who are unresponsive to anti‐PD‐1 therapy. Future studies are needed to validate the prognostic significance of Siglec‐15 and to investigate its regulatory mechanisms in this disease.

Association between pathogenic germline mutations in BRCA2 and ATM and tumor-infiltrating lymphocytes in primary prostate cancer

Pathogenic mutations in homologous recombination (HR) DNA repair genes may be associated with increased tumor mutational burden and numbers of tumor-infiltrating lymphocytes (TIL). Though HR-deficient prostate tumors have been anecdotally associated with improved responses to immunotherapy, it is unclear whether HR mutations or HR deficiency (HRD) scores predict for increased T-cell densities in this cancer. We evaluated 17 primary prostate tumors from patients with pathogenic germline BRCA2 mutations (gBRCA2) and 21 primary prostate tumors from patients with pathogenic germline ATM (gATM) mutations, which were compared to 19 control tumors lacking HR gene mutations, as well as the TCGA prostate cancer cohort. HRD score was estimated by targeted sequencing (gBRCA2 and gATM) or by SNP microarray (TCGA). Tumor-associated T-cell densities were assessed using validated automated digital image analysis of CD8 and FOXP3 immunostaining (gBRCA2 or gATM) or by methylCIBERSORT (TCGA). CD8 + and FOXP3 + T-cell densities were significantly correlated with each other in gBRCA2 and gATM cases. There was no significant difference between CD8 + or FOXP3 + TIL densities in gBRCA2 or gATM cases compared to controls. In the TCGA cohort, HRD score was associated with predicted CD8 + and FOXP3 + TILs. Associations were also seen for HRD score and TIL density among the germline-mutated cases. In contrast to mismatch repair-deficient primary prostate tumors, cancers from germline BRCA2 or ATM mutation carriers do not appear to be associated with elevated TIL density. However, measures of genomic scarring, such as HRD score, may be associated with increased tumor-infiltrating T-cells.

S100A9-CXCL12 activation in BRCA1-mutant breast cancer promotes an immunosuppressive microenvironment associated with resistance to immunotherapy

Immune checkpoint blockade (ICB) is a powerful approach for cancer therapy although good responses are only observed in a fraction of cancer patients. Breast cancers caused by deficiency of breast cancer-associated gene 1 (BRCA1) do not have an improved response to the treatment. To investigate this, here we analyze BRCA1 mutant mammary tissues and tumors derived from both BRCA1 mutant mouse models and human xenograft models to identify intrinsic determinants governing tumor progression and ICB responses. We show that BRCA1 deficiency activates S100A9-CXCL12 signaling for cancer progression and triggers the expansion and accumulation of myeloid-derived suppressor cells (MDSCs), creating a tumor-permissive microenvironment and rendering cancers insensitive to ICB. These oncogenic actions can be effectively suppressed by the combinatory treatment of inhibitors for S100A9-CXCL12 signaling with αPD-1 antibody. This study provides a selective strategy for effective immunotherapy in patients with elevated S100A9 and/or CXCL12 protein levels.

Modulation of Type I Interferon Responses to Influence Tumor-Immune Cross Talk in PDAC

Immunotherapy has revolutionized the treatment of many cancer types. However, pancreatic ductal adenocarcinomas (PDACs) exhibit poor responses to immune checkpoint inhibitors with immunotherapy-based trials not generating convincing clinical activity. PDAC tumors often have low infiltration of tumor CD8+ T cells and a highly immunosuppressive microenvironment. These features classify PDAC as immunologically "cold." However, the presence of tumor T cells is a favorable prognostic feature in PDAC. Intrinsic tumor cell properties govern interactions with the immune system. Alterations in tumor DNA such as genomic instability, high tumor mutation burden, and/or defects in DNA damage repair are associated with responses to both immunotherapy and chemotherapy. Cytotoxic or metabolic stress produced by radiation and/or chemotherapy can act as potent immune triggers and prime immune responses. Damage- or stress-mediated activation of nucleic acid-sensing pathways triggers type I interferon (IFN-I) responses that activate innate immune cells and natural killer cells, promote maturation of dendritic cells, and stimulate adaptive immunity. While PDAC exhibits intrinsic features that have the potential to engage immune cells, particularly following chemotherapy, these immune-sensing mechanisms are ineffective. Understanding where defects in innate immune triggers render the PDAC tumor-immune interface less effective, or how T-cell function is suppressed will help develop more effective treatments and harness the immune system for durable outcomes. This review will focus on the pivotal role played by IFN-I in promoting tumor cell-immune cell cross talk in PDAC. We will discuss how PDAC tumor cells bypass IFN-I signaling pathways and explore how these pathways can be co-opted or re-engaged to enhance the therapeutic outcome.

Immune Checkpoint Inhibitors in Tumors Harboring Homologous Recombination Deficiency: Challenges in Attaining Efficacy

Cancer cells harbor genomic instability due to accumulated DNA damage, one of the cancer hallmarks. At least five major DNA Damage Repair (DDR) pathways are recognized to repair DNA damages during different stages of the cell cycle, comprehending base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR), and non-homologous end joining (NHEJ). The unprecedented benefits achieved with immunological checkpoint inhibitors (ICIs) in tumors with mismatch repair deficiency (dMMR) have prompted efforts to extend this efficacy to tumors with HR deficiency (HRD), which are greatly sensitive to chemotherapy or PARP inhibitors, and also considered highly immunogenic. However, an in-depth understanding of HRD's molecular underpinnings has pointed to essential singularities that might impact ICIs sensitivity. Here we address the main molecular aspects of HRD that underlie a differential profile of efficacy and resistance to the treatment with ICIs compared to other DDR deficiencies.

PTEN Loss and BRCA1 Promoter Hypermethylation Negatively Predict for Immunogenicity in BRCA-Deficient Ovarian Cancer

PURPOSE

Ovarian cancers can exhibit a prominent immune infiltrate, but clinical trials have not demonstrated substantive response rates to immune checkpoint blockade monotherapy. We aimed to understand genomic features associated with immunogenicity in BRCA1/2 mutation-associated cancers.

MATERIALS AND METHODS

Using the Cancer Genome Atlas whole-exome sequencing, methylation, and expression data, we analyzed 66 ovarian cancers with either germline or somatic loss of BRCA1/2 and whole-exome sequencing, immunohistochemistry, and CyTOF in 20 ovarian cancers with germline BRCA1/2 pathogenic variants from Penn.

RESULTS

We found two groups of BRCA1/2 ovarian cancers differing in their immunogenicity: (1) 37 tumors significantly enriched for PTEN loss (11, 30%) and BRCA1 promoter-hypermethylated (10, 27%; P = .0016) and (2) PTEN wild-type (28 of 29 tumors) cancers, with the latter group having longer overall survival (OS; P = .0186, median OS not reached v median OS = 66.1 months). BRCA1/2-mutant PTEN loss and BRCA1 promoter-hypermethylated cancers were characterized by the decreased composition of lymphocytes estimated by gene expression (P = .0030), cytolytic index (P = .034), and cytokine expression but higher homologous recombination deficiency scores (P = .00013). Large-scale state transitions were the primary discriminating feature (P = .001); neither mutational burden nor neoantigen burden could explain differences in immunogenicity. In Penn tumors, PTEN loss and high homologous recombination deficiency cancers exhibited fewer CD3+ (P = .05), CD8+ (P = .012), and FOXP3+ (P = .0087) T cells; decreased PRF1 expression (P = .041); and lower immune costimulatory and inhibitory molecule expression.

CONCLUSION

Our study suggests that within ovarian cancers with genetic loss of BRCA1/2 are two subsets exhibiting differential immunogenicity, with lower levels associated with PTEN loss and BRCA hypermethylation. These genomic features of BRCA1/2-associated ovarian cancers may inform considerations around how to optimally deploy immune checkpoint inhibitors in the clinic.

When breaks get hot: inflammatory signaling in BRCA1/2-mutant cancers

Genomic instability and inflammation are intricately connected hallmark features of cancer. DNA repair defects due to BRCA1/2 mutation instigate immune signaling through the cGAS/STING pathway. The subsequent inflammatory signaling provides both tumor-suppressive as well as tumor-promoting traits. To prevent clearance by the immune system, genomically instable cancer cells need to adapt to escape immune surveillance. Currently, it is unclear how genomically unstable cancers, including BRCA1/2-mutant tumors, are rewired to escape immune clearance. Here, we summarize the mechanisms by which genomic instability triggers inflammatory signaling and describe adaptive mechanisms by which cancer cells can 'fly under the radar' of the immune system. Additionally, we discuss how therapeutic activation of the immune system may improve treatment of genomically instable cancers.

Psychosocial outcome and health behaviour intent of breast cancer patients with BRCA1/2 and PALB2 pathogenic variants unselected by a priori risk

There is an increasing number of cancer patients undertaking treatment-focused genetic testing despite not having a strong family history or high a priori risk of being carriers because of the decreasing cost of genetic testing and development of new therapies. There are limited studies on the psychosocial outcome of a positive result among breast cancer patients who are at low a priori risk, particularly in women of Asian descent. Breast cancer patients enrolled under the Malaysian Breast Cancer Genetic Study between October 2002 and February 2018 were tested for BRCA1, BRCA2 and PALB2 genes. All 104 carriers identified were invited by a research genetic counsellor for result disclosure. Of the 104 carriers, 64% (N = 66) had low a priori risk as determined by PENN II scores. Psychosocial, risk perception and health behaviour measures survey were conducted at baseline (pre-result disclosure), and at two to six weeks after result disclosure. At baseline, younger carriers with high a priori risk had higher Cancer Worry Scale scores than those with low a priori risk but all scores were within acceptable range. Around 75% and 55% of high a priori risk carriers as well as 80% and 67% of low a priori risk carriers had problems in the "living with cancer" and "children" psychosocial domains respectively. All carriers regardless of their a priori risk demonstrated an improved risk perception that also positively influenced their intent to undergo risk management procedures. This study has shown that with sufficient counselling and support, low a priori risk carriers are able to cope psychologically, have improved perceived risk and increased intent for positive health behaviour despite having less anticipation from a family history prior to knowing their germline carrier status.

Current Treatments and New Possible Complementary Therapies for Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is one of the deadliest gynaecological malignancies. The late diagnosis is frequent due to the absence of specific symptomatology and the molecular complexity of the disease, which includes a high angiogenesis potential. The first-line treatment is based on optimal debulking surgery following chemotherapy with platinum/gemcitabine and taxane compounds. During the last years, anti-angiogenic therapy and poly adenosine diphosphate-ribose polymerases (PARP)-inhibitors were introduced in therapeutic schemes. Several studies have shown that these drugs increase the progression-free survival and overall survival of patients with ovarian cancer, but the identification of patients who have the greatest benefits is still under investigation. In the present review, we discuss about the molecular characteristics of the disease, the recent evidence of approved treatments and the new possible complementary approaches, focusing on drug repurposing, non-coding RNAs, and nanomedicine as a new method for drug delivery.

Predictive Biomarkers of Immune Checkpoint Inhibitor Response in Breast Cancer: Looking beyond Tumoral PD-L1

Immune checkpoint inhibitors utilize the immune system to kill cancer cells and are now widely applied across numerous malignancies. Pembrolizumab has two breast-specific indications in triple-negative disease. Currently, programmed death ligand-1 (PD-L1) expression on tumor and surrounding immune cells is the only validated predictive biomarker for immune checkpoint inhibitors (ICIs) in breast cancer; however, it can be imprecise. Additional biomarkers are needed to identify the patient population who will derive the most benefit from these therapies. The tumor immune microenvironment contains many biomarker candidates. In tumor cells, tumor mutational burden has emerged as a robust biomarker across malignancies in general, with higher burden cancers demonstrating improved response, but will need further refinement for less mutated cancers. Preliminary studies suggest that mutations in breast cancer gene 2 (BRCA-2) are associated with increased immune infiltration and response to ICI therapy. Other genomic alterations are also being investigated as potential predictive biomarkers. In immune cells, increased quantity of tumor-infiltrating lymphocytes and CD8+ cytotoxic T cells have correlated with response to immunotherapy treatment. The role of other immune cell phenotypes is being investigated. Peripherally, many liquid-based biomarker strategies such as PD-L1 expression on circulating tumor cells and peripheral immune cell quantification are being studied; however, these strategies require further standardization and refinement prior to large-scale testing. Ultimately, multiple biomarkers utilized together may be needed to best identify the appropriate patients for these treatments.

Therapeutic Associations Comprising Anti-PD-1/PD-L1 in Breast Cancer: Clinical Challenges and Perspectives

Despite a few cases of long-responder patients, immunotherapy with anti-PD-(L)1 has so far proved rather disappointing in monotherapy in metastatic breast cancer, prompting the use of synergistic therapeutic combinations incorporating immunotherapy by immune-checkpoint inhibitors. In addition, a better understanding of both the mechanisms of sensitivity and resistance to immunotherapy, as well as the immunological effects of the usual treatments for breast cancer, make it possible to rationally consider this type of therapeutic combination. For several years, certain treatments, commonly used to treat patients with breast cancer, have shown that in addition to their direct cytotoxic effects, they may have an impact on the tumor immune microenvironment, by increasing the antigenicity and/or immunogenicity of a "cold" tumor, targeting the immunosuppressive microenvironment or counteracting the immune-exclusion profile. This review focuses on preclinical immunologic synergic mechanisms of various standard therapeutic approaches with anti-PD-(L)1, and discusses the potential clinical use of anti-PD-1/L1 combinations in metastatic or early breast cancer.

Genomic instability, inflammatory signaling and response to cancer immunotherapy

Genomic and chromosomal instability are hallmarks of cancer and shape the genomic composition of cancer cells, thereby determining their behavior and response to treatment. Various genetic and epigenetic alterations in cancer have been linked to genomic instability, including DNA repair defects, oncogene-induced replication stress, and spindle assembly checkpoint malfunction. A consequence of genomic and chromosomal instability is the leakage of DNA from the nucleus into the cytoplasm, either directly or through the formation and subsequent rupture of micronuclei. Cytoplasmic DNA subsequently activates cytoplasmic DNA sensors, triggering downstream pathways, including a type I interferon response. This inflammatory signaling has pleiotropic effects, including enhanced anti-tumor immunity and potentially results in sensitization of cancer cells to immune checkpoint inhibitors. However, cancers frequently evolve mechanisms to avoid immune clearance, including suppression of inflammatory signaling. In this review, we summarize inflammatory signaling pathways induced by various sources of genomic instability, adaptation mechanisms that suppress inflammatory signaling, and implications for cancer immunotherapy.

Matched cohort study of germline BRCA mutation carriers with triple negative breast cancer in brightness

In the BrighTNess trial, carboplatin added to neoadjuvant chemotherapy (NAC) was associated with increased pathologic complete response (pCR) rates in patients with stage II/III triple-negative breast cancer (TNBC). In this matched cohort study, cases with a germline BRCA1/2 mutation (gBRCA; n = 75) were matched 1:2 with non-gBRCA controls (n = 150) by treatment arm, lymph node status, and age to evaluate pCR rates and association of benefit from platinum/PARP inhibitors with validated RNA expression-based immune, proliferation, and genomic instability scores among gBRCA with the addition of carboplatin ± veliparib to NAC. Among the well-matched cohorts, odds of pCR were not higher in gBRCA cancers who received standard NAC with carboplatin (OR 0.24, 95% CI [0.04-1.24], p = 0.09) or with carboplatin/veliparib (OR 0.44, 95% CI [0.10-1.84], p = 0.26) compared to non-gBRCA cancers. Higher PAM50 proliferation, GeparSixto immune, and CIN70 genomic instability scores were each associated with higher pCR rate in the overall cohort, but not specifically in gBRCA cases. In this study, gBRCA carriers did not have higher odds of pCR than non-gBRCA controls when carboplatin ± veliparib was added to NAC, and showed no significant differences in molecular, immune, chromosomal instability, or proliferation gene expression metrics.

Harnessing DNA Repair Defects to Augment Immune-Based Therapies in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) has poor prognosis with limited treatment options, with little therapeutic progress made during the past several decades. DNA damage response (DDR) associated therapies, including radiation and inhibitors of DDR, demonstrate potential efficacy against TNBC, especially under the guidance of genomic subtype-directed treatment. The tumor immune microenvironment also contributes greatly to TNBC malignancy and response to conventional and targeted therapies. Immunotherapy represents a developing trend in targeted therapies directed against TNBC and strategies combining immunotherapy and modulators of the DDR pathways are being pursued. There is increasing understanding of the potential interplay between DDR pathways and immune-associated signaling. As such, the question of how we treat TNBC regarding novel immuno-molecular strategies is continually evolving. In this review, we explore the current and upcoming treatment options of TNBC in the context of DNA repair mechanisms and immune-based therapies, with a focus on implications of recent genomic analyses and clinical trial findings.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of breast cancer

Breast cancer has historically been a disease for which immunotherapy was largely unavailable. Recently, the use of immune checkpoint inhibitors (ICIs) in combination with chemotherapy for the treatment of advanced/metastatic triple-negative breast cancer (TNBC) has demonstrated efficacy, including longer progression-free survival and increased overall survival in subsets of patients. Based on clinical benefit in randomized trials, ICIs in combination with chemotherapy for the treatment of some patients with advanced/metastatic TNBC have been approved by the United States (US) Food and Drug Administration (FDA), expanding options for patients. Ongoing questions remain, however, about the optimal chemotherapy backbone for immunotherapy, appropriate biomarker-based selection of patients for treatment, the optimal strategy for immunotherapy treatment in earlier stage disease, and potential use in histological subtypes other than TNBC. To provide guidance to the oncology community on these and other important concerns, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). The expert panel drew upon the published literature as well as their clinical experience to develop recommendations for healthcare professionals on these important aspects of immunotherapeutic treatment for breast cancer, including diagnostic testing, treatment planning, immune-related adverse events (irAEs), and patient quality of life (QOL) considerations. The evidence-based and consensus-based recommendations in this CPG are intended to give guidance to cancer care providers treating patients with breast cancer.

Soluble interleukin-2 receptor as a predictive and prognostic marker for patients with familial breast cancer

The incidence of breast cancer increases annually, and it has become common within families of breast cancer patients. Interleukin-2 activates cytotoxic T lymphocytes, which are important for cancer immunity. To identify markers of increased familial breast cancer risk, soluble interleukin-2 receptor levels and immunologic factors were investigated in familial breast cancer and non-familial breast cancer patients. Of 106 untreated breast cancer patients in this study, 24 had familial breast cancer and 82 had non-familial breast cancer. The patients' soluble interleukin-2 receptor, interleukin-10, vascular endothelial growth factor, interleukin-17, regulatory T cell, myeloid-derived suppressor cell, white blood cell, and C-reactive protein levels, and their neutrophil-to-lymphocyte ratios were measured, and their prognoses were compared according to the soluble interleukin-2 receptor levels. Additionally, postoperative tissues from the patients with high soluble interleukin-2 receptor levels were stained with programmed cell death ligand 1 and cluster of differentiation 8. The soluble interleukin-2 receptor level in the familial breast cancer patients was significantly higher, and it showed significantly stronger correlations with the neutrophil-to-lymphocyte ratio and the interleukin-10, vascular endothelial growth factor, interleukin-17, regulatory T cell, myeloid-derived suppressor cell, white blood cell, and C-reactive protein levels, than in the non-familial breast cancer patients. The regulatory T cell and myeloid-derived suppressor cell levels were significantly higher in the patients with high soluble interleukin-2 receptor levels, and the overall survival and disease-free-survival rates were significantly worse for the familial breast cancer patients than for the non-familial breast cancer patients. Triple-negative breast cancer tissues from the familial breast cancer patients with high soluble interleukin-2 receptor levels stained well for programmed cell death ligand 1 and cluster of differentiation 8. Soluble interleukin-2 receptor levels can be used to predict the prognosis of familial breast cancer patients. Prospectively identifying patients who are less likely to have non-familial breast cancer is vital for improving their overall survival.

BRCA1/2 signaling and homologous recombination deficiency in breast and ovarian cancer

Patients who have mutations of the genes BRCA1 or BRCA2 are at an increased risk for developing breast and ovarian cancer. BRCA1/2 function as tumor suppressor genes, responsible for regulating DNA repair, and play an essential role in homologous recombination. Mutation of BRCA1/2 results in homologous recombination deficiency and genomic instability which drives oncogenesis and cancer proliferation. Recently, BRCA1/2 gene expression has been implicated in regulating immune response. Here we discuss the signaling pathway of BRCA1/2 in relation to breast and ovarian cancer, with emphasis on how dysregulation facilitates the path to malignancy and current treatment options.

Homologous Recombination Repair Deficiency and Implications for Tumor Immunogenicity

Homologous recombination repair deficiency (HRD) can be observed in virtually all cancer types. Although HRD sensitizes tumors to DNA-damaging chemotherapy and poly(ADP-ribose) polymerase (PARP) inhibitors, all patients ultimately develop resistance to these therapies. Therefore, it is necessary to identify therapeutic regimens with a more durable efficacy. HRD tumors have been suggested to be more immunogenic and, therefore, more susceptible to treatment with checkpoint inhibitors. In this review, we describe how HRD might mechanistically affect antitumor immunity and summarize the available translational evidence for an association between HRD and antitumor immunity across multiple tumor types. In addition, we give an overview of all available clinical data on the efficacy of checkpoint inhibitors in HRD tumors and describe the evidence for using treatment strategies that combine checkpoint inhibitors with PARP inhibitors.

Combining poly(ADP-ribose) polymerase inhibitors and immune checkpoint inhibitors in breast cancer: rationale and preliminary clinical results

PURPOSE OF REVIEW

Recently, both immune checkpoint inhibitors and poly(ADP-ribose) polymerase inhibitors have demonstrated clinical benefit in some subsets of HER2-negative breast cancer patients. A biological rationale exists supporting a potential synergism between these compounds, which may further increase their antitumor activity in the clinic.

RECENT FINDINGS

PARP inhibitors were shown to activate type I interferon pathway, thus eliciting local and general immune response, while inducing programmed cell death-ligand 1 (PD-L1) up-regulation. In addition, the DNA damages created by PARP inhibition may increase tumor mutational burden and neo-antigens, thereby favoring efficacy of immune checkpoint inhibitors. Accordingly, clinical trials combining PARP inhibitors and agents targeting the PD-1/PD-L1 axis have been initiated in breast cancer in both advanced and early stages, enrolling patients with germline BRCA1/2 mutation, homologous recombination deficiency and/or with triple negative phenotype. Preliminary safety and efficacy results are encouraging, but it is still unclear whether the combination adds benefit compared with each therapeutic administered as single agent.

SUMMARY

Although a strong rationale exists to support the combination of PARP inhibitors with immune checkpoint inhibitors, future clinical trials will have to demonstrate whether it improves outcome and to identify which patients are the most likely to benefit from.

The Role of BRCA1/2-Mutated Tumor Microenvironment in Breast Cancer

Taking into account the factors of high incidence rate, prevalence and mortality, breast cancer represents a crucial social and economic burden. Most cases of breast cancer develop as a consequence of somatic mutations accumulating in mammary epithelial cells throughout lifetime and approximately 5-10% can be ascribed to monogenic predispositions. Even though the role of genetic predispositions in breast cancer is well described in the context of genetics, very little is known about the role of the microenvironment carrying the same aberrant cells impaired by the germline mutation in the breast cancer development and progression. Based on the clinical observations, carcinomas carrying mutations in hereditary tumor-suppressor genes involved in maintaining genome integrity such as BRCA1/2 have worse prognosis and aggressive behavior. One of the mechanisms clarifying the aggressive nature of BRCA-associated tumors implies alterations within the surrounding adipose tissue itself. The objective of this review is to look at the role of BRCA1/2 mutations in the context of breast tumor microenvironment and plausible mechanisms by which it contributes to the aggressive behavior of the tumor cells.

Update on systemic treatment in early triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogeneous disease representing about 15% of all breast cancers. TNBC are usually high-grade histological tumors, and are generally more aggressive and difficult to treat due to the lack of targeted therapies available, and chemotherapy remains the standard treatment. There is a close relationship between pathological complete response after chemotherapy treatment and higher rates of disease-free survival and overall survival. In this review of systemic treatment in early triple negative breast cancer, our purpose is to analyze and compare different therapies, as well as to highlight the novelties of treatment in this breast cancer subtype.