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Current genetic and genomic tests measuring homologous recombination deficiency (HRD) show limited predictive value. This study compares the performance of an immunohistology-based RAD51 test with genetic/genomic tests to identify patients with HRD primary triple-negative breast cancer (TNBC) and evaluates its accuracy to select patients sensitive to platinum-based neoadjuvant chemotherapy (NACT). This is a retrospective, blinded, biomarker analysis from the GeparSixto randomized clinical trial. TNBC patients received neoadjuvant paclitaxel plus Myocet®-nonpegylated liposomal doxorubicin (PM) or PM plus carboplatin (PMCb), both arms including bevacizumab. Formalin-fixed paraffin-embedded (FFPE) tumor samples were laid on tissue microarrays. RAD51, BRCA1 and γH2AX were quantified using an immunofluorescence assay. The predictive value of RAD51 was assessed by regression models. Concordance analyses were carried out between RAD51 score and tumor BRCA (t BRCA) status or genomic HRD score (Myriad myChoice®). Associations with pathological complete response (pCR) and survival were studied. Functional HRD was predefined as a RAD51 score ≤10% (RAD51-low). Functional HRD by RAD51-low was evidenced in 81/133 tumors (61%). RAD51 identified 93% t BRCA -mutated tumors and 45% non-t BRCA mutant cases as functional HRD. The concordance between RAD51 and genomic HRD was 87% [95% confidence interval (CI) 79% to 93%]. In patients with RAD51-high tumors, pCR was similar between treatment arms [PMCb 31% versus PM 39%, odds ratio (OR) 0.71, 0.23-2.24, P = 0.56]. Patients with RAD51-low tumors benefited from PMCb (pCR 66% versus 33%, OR 3.96, 1.56-10.05, P = 0.004; interaction test P = 0.02). This benefit maintained statistical significance in the multivariate analysis. Carboplatin addition showed similar disease-free survival in the RAD51-high [hazard ratio (HR) 0.40, log-rank P = 0.11] and RAD51-low (0.45, P = 0.11) groups. The RAD51 test identifies tumors with functional HRD and is highly concordant with t BRCA mutation and genomic HRD. RAD51 independently predicts clinical benefit from adding Cb to NACT in TNBC. Our results support further development to incorporate RAD51 testing in clinical decision-making. • Functional HRD by the RAD51 test identifies 93% of t BRCA -mutated TNBC tumors and shows 87% concordance with genomic HRD. • RAD51 independently predicts pCR with platinum (interaction test P = 0.02). • This study supports the use of RAD51 as a clinically relevant biomarker of HRD and platinum response. [ABSTRACT FROM AUTHOR]

Background: Allergen exposure at lung and gut mucosae can lead to aberrant TH2 immunity and allergic disease. The epithelium-associated cytokines thymic stromal lymphopoietin (TSLP), IL-25, and IL-33 are suggested to be important for the initiation of these responses. Objective: We sought to investigate the contributions of TSLP, IL-25, and IL-33 in the development of allergic disease to the common allergens house dust mite (HDM) or peanut. Methods: Neutralizing antibodies or mice deficient in TSLP, IL-25, or IL-33 signaling were exposed to HDM intranasally or peanut intragastrically, and immune inflammatory and physiologic responses were evaluated. In vitro assays were performed to examine specific dendritic cell (DC) functions. Results: We showed that experimental HDM-induced allergic asthma and food allergy and anaphylaxis to peanut were associated with TSLP production but developed independently of TSLP, likely because these allergens functionally mimicked TSLP inhibition of IL-12 production and induction of OX40 ligand (OX40L) on DCs. Blockade of OX40L significantly lessened allergic responses to HDM or peanut. Although IL-25 and IL-33 induced OX40L on DCs in vitro, only IL-33 signaling was necessary for intact allergic immunity, likely because of its superior ability to induce DC OX40L and expand innate lymphoid cells in vivo. Conclusion: These data identify a nonredundant, IL-33–driven mechanism initiating TH2 responses to the clinically relevant allergens HDM and peanut. Our findings, along with those in infectious and transgenic/surrogate allergen systems, favor a paradigm whereby multiple molecular pathways can initiate TH2 immunity, which has implications for the conceptualization and manipulation of these responses in health and disease. [ABSTRACT FROM AUTHOR]

The antitumor efficacy of PARP inhibitors (PARPi) for breast cancer patients harboring germline BRCA1/2 (g BRCA1/2) mutations is well established. While PARPi monotherapy was ineffective in patients with metastatic triple negative breast cancer (TNBC) wild type for BRCA1/2 , we hypothesized that PARPi may be effective in primary TNBCs without previous chemotherapy exposure. In the phase II PETREMAC trial, patients with primary TNBC >2 cm received olaparib for up to 10 weeks before chemotherapy. Tumor biopsies collected before and after olaparib underwent targeted DNA sequencing (360 genes) and BRCA1 methylation analyses. In addition, BRCA ness (multiplex ligation-dependent probe amplification), PAM50 gene expression, RAD51 foci, tumor-infiltrating lymphocytes (TILs) and PD-L1 analyses were performed on pretreatment samples. The median pretreatment tumor diameter was 60 mm (range 25-112 mm). Eighteen out of 32 patients obtained an objective response (OR) to olaparib (56.3%). Somatic or germline mutations affecting homologous recombination (HR) were observed in 10/18 responders [OR 55.6%, 95% confidence interval (CI) 33.7-75.4] contrasting 1/14 non-responders (OR 7.1%; CI 1.3-31.5, P = 0.008). Among tumors without HR mutations, 6/8 responders versus 3/13 non-responders revealed BRCA1 hypermethylation (P = 0.03). Thus, 16/18 responders (88.9%, CI 67.2-96.9), in contrast to 4/14 non-responders (28.6%, CI 11.7-54.7, P = 0.0008), carried HR mutations and/or BRCA1 methylation. Excluding one g PALB2 and four g BRCA1/ 2 mutation carriers, 12/14 responders (85.7%, CI 60.1-96.0) versus 3/13 non-responders (23.1%, CI 8.2-50.3, P = 0.002) carried somatic HR mutations and/or BRCA1 methylation. In contrast to BRCA ness signature or basal-like subtype, low RAD51 scores, high TIL or high PD-L1 expression all correlated to olaparib response. Olaparib yielded a high clinical response rate in treatment-naïve TNBCs revealing HR deficiency, beyond germline HR mutations. ClinicalTrials.gov identifier: NCT02624973. • We observed an objective response to olaparib in 18 out of 32 (56%) of unselected, primary triple negative breast cancers. • Homologous recombination deficiency (HRD) was determined by targeted DNA sequencing and BRCA1 methylation. • HRD was predictive of response to olaparib and present in 16 out of 18 responders. • HRD was also predictive of response to olaparib beyond germline BRCA1/2 and g PALB2 mutations; 12 out of 14 responders. • Olaparib was associated with minor side-effects and did not influence subsequent tolerance to chemotherapy. [ABSTRACT FROM AUTHOR]

Background: BRCA1 and BRCA2 (BRCA1/2)-deficient tumors display impaired homologous recombination repair (HRR) and enhanced sensitivity to DNA damaging agents or to poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi). Their efficacy in germline BRCA1/2 (gBRCA1/2)-mutated metastatic breast cancers has been recently confirmed in clinical trials. Numerous mechanisms of PARPi resistance have been described, whose clinical relevance in gBRCA-mutated breast cancer is unknown. This highlights the need to identify functional biomarkers to better predict PARPi sensitivity. Patients and methods: We investigated the in vivo mechanisms of PARPi resistance in gBRCA1 patient-derived tumor xenografts (PDXs) exhibiting differential response to PARPi. Analysis included exome sequencing and immunostaining of DNA damage response proteins to functionally evaluate HRR. Findings were validated in a retrospective sample set from gBRCA1/ 2-cancer patients treated with PARPi. Results: RAD51 nuclear foci, a surrogate marker of HRR functionality, were the only common feature in PDX and patient samples with primary or acquired PARPi resistance. Consistently, low RAD51 was associated with objective response to PARPi. Evaluation of the RAD51 biomarker in untreated tumors was feasible due to endogenous DNA damage. In PARPi-resistant gBRCA1 PDXs, genetic analysis found no in-frame secondary mutations, but BRCA1 hypomorphic proteins in 60% of the models, TP53BP1-loss in 20% and RAD51-amplification in one sample, none mutually exclusive. Conversely, one of three PARPi-resistant gBRCA2 tumors displayed BRCA2 restoration by exome sequencing. In PDXs, PARPi resistance could be reverted upon combination of a PARPi with an ataxia-telangiectasia mutated (ATM) inhibitor. Conclusion: Detection of RAD51 foci in gBRCA tumors correlates with PARPi resistance regardless of the underlying mechanism restoring HRR function. This is a promising biomarker to be used in the clinic to better select patients for PARPi therapy. Our study also supports the clinical development of PARPi combinations such as those with ATM inhibitors. [ABSTRACT FROM AUTHOR]

Ductal carcinoma in situ (DCIS) is a non-obligate precursor of invasive breast cancer (IBC). Due to a lack of biomarkers able to distinguish high- from low-risk cases, DCIS is treated similar to early IBC even though the minority of untreated cases eventually become invasive. Here, we characterized 115 patient-derived mouse-intraductal (MIND) DCIS models reflecting the full spectrum of DCIS observed in patients. Utilizing the possibility to follow the natural progression of DCIS combined with omics and imaging data, we reveal multiple prognostic factors for high-risk DCIS including high grade, HER2 amplification, expansive 3D growth, and high burden of copy number aberrations. In addition, sequential transplantation of xenografts showed minimal phenotypic and genotypic changes over time, indicating that invasive behavior is an intrinsic phenotype of DCIS and supporting a multiclonal evolution model. Moreover, this study provides a collection of 19 distributable DCIS-MIND models spanning all molecular subtypes. [Display omitted] • Development of a biobank of DCIS-MIND models retaining primary features • Identification of multiple factors associated with invasive progression of DCIS • Identification of two distinct 3D growth patterns associated with outcome • Development of a collection of 19 distributable DCIS models Hutten et al. generate 115 DCIS-MIND models and characterize them with genomic, transcriptomic, and imaging data. With this biobank they identify risk factors associated with progression of ductal carcinoma in situ to invasive breast cancer and create a collection of 19 distributable DCIS models, providing a resource for further research. [ABSTRACT FROM AUTHOR]