Homologous recombination deficiency and host anti-tumor immunity in triple-negative breast cancer

Purpose: Triple-negative breast cancer (TNBC) is associated with worse outcomes relative to other breast cancer subtypes. Chemotherapy remains the standard-of-care systemic therapy for patients with localized or metastatic disease, with few biomarkers to guide benefit. Methods: We will discuss recent advances in our understanding of two key biological processes in TNBC, homologous recombination (HR) DNA repair deficiency and host anti-tumor immunity, and their intersection. Results: Recent advances in our understanding of homologous recombination (HR) deficiency, including FDA approval of PARP inhibitor olaparib for BRCA1 or BRCA2 mutation carriers, and host anti-tumor immunity in TNBC offer potential for new and biomarker-driven approaches to treat TNBC. Assays interrogating HR DNA repair capacity may guide treatment with agents inducing or targeting DNA damage repair. Tumor infiltrating lymphocytes (TILs) are associated with improved prognosis in TNBC and recent efforts to characterize infiltrating immune cell subsets and activate host anti-tumor immunity offer promise, yet challenges remain particularly in tumors lacking pre-existing immune infiltrates. Advances in these fields provide potential biomarkers to stratify patients with TNBC and guide therapy: induction of DNA damage in HR-deficient tumors and activation of existing or recruitment of host anti-tumor immune cells. Importantly, these advances provide an opportunity to guide use of existing therapies and development of novel therapies for TNBC. Efforts to combine therapies that exploit HR deficiency to enhance the activity of immune-directed therapies offer promise. Conclusions: HR deficiency remains an important biomarker target and potentially effective adjunct to enhance immunogenicity of ‘immune cold’ TNBCs

The immune microenvironment in hormone receptor-positive breast cancer before and after preoperative chemotherapy

Purpose: Hormone receptor-positive/HER2-negative (HR+/HER2_) breast cancer is associated with low levels of stromal tumor-infiltrating lymphocytes (sTIL) and PD-L1, and demonstrates poor responses to checkpoint inhibitor therapy. Evaluating the effect of standard chemotherapy on the immune microenvironment may suggest new opportunities for immunotherapy-based approaches to treating HR+/HER2_ breast tumors. Experimental Design: HR+/HER2_ breast tumors were analyzed before and after neoadjuvant chemotherapy. sTIL were assessed histologically; CD8+ cells, CD68+ cells, and PD-L1 staining were assessed immunohistochemically; whole transcriptome sequencing and panel RNA expression analysis (NanoString) were performed. Results: Ninety-six patients were analyzed from two cohorts (n = 55, Dana-Farber cohort; n = 41, MD Anderson cohort). sTIL, CD8, and PD-L1 on tumor cells were higher in tumors with basal PAM50 intrinsic subtype. Higher levels of tissuebased lymphocyte (sTIL, CD8, PD-L1) and macrophage (CD68) markers, as well as gene expression markers of lymphocyte or macrophage phenotypes (NanoString or CIBERSORT), correlated with favorable response to neoadjuvant chemotherapy, but not with improved distant metastasis-free survival in these cohorts or a large gene expression dataset (N = 302). In paired pre-/postchemotherapy samples, sTIL and CD8+ cells were significantly decreased after treatment, whereas expression analyses (NanoString) demonstrated significant increase of multiple myeloid signatures. Single gene expression implicated increased expression of immunosuppressive (M2-like) macrophage-specific genes after chemotherapy. Conclusions: The immune microenvironment of HR+/ HER2_ tumors differs according to tumor biology. This cohort of paired pre-/postchemotherapy samples suggests a critical role for immunosuppressive macrophage expansion in residual disease. The role of macrophages in chemoresistance should be explored, and further evaluation of macrophagetargeting therapy is warranted

Serine Hydroxymethyltransferase Anchors de Novo Thymidylate Synthesis Pathway to Nuclear Lamina for DNA Synthesis

The de novo thymidylate biosynthetic pathway in mammalian cells translocates to the nucleus for DNA replication and repair and consists of the enzymes serine hydroxymethyltransferase 1 and 2 alpha (SHMT1 and SHMT2 alpha), thymidylate synthase, and dihydrofolate reductase. In this study, we demonstrate that this pathway forms a multienzyme complex that is associated with the nuclear lamina. SHMT1 or SHMT2 alpha is required for co-localization of dihydrofolate reductase, SHMT, and thymidylate synthase to the nuclear lamina, indicating that SHMT serves as scaffold protein that is essential for complex formation. The metabolic complex is enriched at sites of DNA replication initiation and associated with proliferating cell nuclear antigen and other components of the DNA replication machinery. These data provide a mechanism for previous studies demonstrating that SHMT expression is rate-limiting for de novo thymidylate synthesis and indicate that de novo thymidylate biosynthesis occurs at replication forks

Agronomical and molecular characterization of banana germplasm Caracterização agronômica e molecular de germoplasma de bananeira

The objective of the present work was to characterize banana accessions from the Germplasm Bank at Embrapa Mandioca e Fruticultura Tropical (Brazil), using agronomical, physical and physicochemical characteristics of fruit and simple sequence repeats (SSR) markers. Twenty-six accessions were analyzed, in which high genetic variability was found, especially for the agronomical characters number of fruit and weight of bunch. Accessions with high contents of carotenoids (diploid 'Jaran'), polyphenols (triploid 'Caipira' and tetraploid 'Teparod') and vitamin C (diploid 'Tuugia' and an unknown triploid AAA) in the fruit were identified. Thirteen microsatellite primers revealed an average of 7.23 alleles, which showed high variability. A dendrogram was prepared using the Gower algorithm for the distance matrices obtained from the agronomical, physical and physicolchemical analysis of fruit and SSR markers. Adopting the average genetic divergence as the cut-off point, three clusters were found: G1, formed by the diploids 'Jaran', 028003-01 and M-48; G2, by the diploids 'Malbut' and 'Ido 110'; and G3, by 21 tri-and tetraploid accessions, including one diploid, 'Tuugia'. The triploids with the B genome 'Thap Maeo', 'Walha', 'Pacha Nadan' and 'Champa Madras' were grouped in G2. Results from this work can be used for breeding hybrids with good agronomical traits and fruit quality.<br>O objetivo deste trabalho foi caracterizar acessos de bananeira do Banco de Germoplasma da Embrapa Mandioca e Fruticultura Tropical, por meio de características agronômicas, físicas e físico-químicas dos frutos e por marcadores "Simple sequence repeats" (SSR). Foram analisados 26 acessos, nos quais observou-se ampla variabilidade genética, em especial para número de frutos e peso de cacho. Foram identificados acessos com altos teores de carotenoides (diploide 'Jaran'), polifenóis (tetraploide 'Teparod') e vitamina C (diploide 'Tuugia' e um triploide AAA desconhecido). Os 13 iniciadores microssatélites testados apresentaram uma média de 7,23 alelos, que apresentaram alta variabilidade. Com uso do algoritmo de Gower, foi elaborado um dendrograma com as matrizes de distância obtidas por meio das análises agronômicas, físicas e físico-químicas dos frutos e análises moleculares. Com a divergência genética média usada como ponto de corte, foram identificados três agrupamentos: G1, formado pelos diploides 'Jaran', 028003-01 e M-48; G2, pelos diploides 'Malbut' e 'Ido 110'; e G3, pelos 21 acessos tri-e tetraploides, incluindo-se um diploide 'Tuugia'. Os triploides com genoma B 'Thap Maeo', 'Walha', 'Pacha Nadan' e 'Champa Madras' agruparam-se no G2. Os resultados obtidos podem ser utilizados no melhoramento genético, para o desenvolvimento de híbridos com boas características agronômicas e qualidade de frutos