HER2-low breast cancer (i.e., HER 1+ or 2+, without gene amplification) is an emerging subtype for which very few data are available, especially within the triple-negative breast cancer (TNBC) group. Our aim was to evaluate HER2 expression and its prognostic value in a large retrospective series of patients with non-metastatic TNBC (median age: 57.7 years; range: 28.5–98.6). Among the 296 TNBC samples, 83.8% were HER2 0, 13.5% were HER2 1+, and 2.7% were HER2 2+ (HercepTestTM and 2018 ASCO/CAP guidelines for HER2 scoring). CK5/6 and/or EGFR-expressing androgen receptors and FOXA1-expressing tumors were classified as basal-like (63.8%) and molecular apocrine-like (MA, 40.2%), respectively. Compared with HER2 0 tumors, HER2 1+/2+ tumors exhibited a lower histological grade (1/2) (35.4% vs. 18.2%, p = 0.007) and MA profile (57.5% vs. 36.7%, p = 0.008). Moreover, patients with HER2 1+/2+ tumors were older (p = 0.047). After a median follow-up of 9.7 years, HER2 2+ tumors (compared with HER2 0/1+ tumors) were associated with worse relapse-free survival (RFS) (HR = 3.16, 95% CI [1.27; 7.85], p = 0.034) in a univariate analysis. Overall survival (OS) and RFS were not different in the HER2 0 and 1+/2+ groups. HER2 levels were not significantly associated with OS or RFS in a multivariate analysis.

Expression of hormone receptor (HR) for estrogens (ER) and progesterone (PR) and HER2 remains the cornerstone to define the therapeutic strategy for breast cancer patients. We aimed to compare phenotypic profiles between matched primary and metastatic breast cancer (MBC) in the ESME database, a National real-life multicenter cohort of MBC patients. Patients with results available on both primary tumour and metastatic disease within 6 months of MBC diagnosis and before any tumour progression were eligible for the main analysis. Among the 16,703 patients included in the database, 1677 (10.0%) had available biopsy results at MBC diagnosis and on matched primary tumour. The change rate of either HR or HER2 was 27.0%. Global HR status changed (from positive = either ER or PR positive, to negative = both negative; and reverse) in 14.2% of the cases (expression loss in 72.5% and gain in 27.5%). HER2 status changed in 7.8% (amplification loss in 45.2%). The discordance rate appeared similar across different biopsy sites. Metastasis to bone, HER2+ and RH+/HER2- subtypes and previous adjuvant endocrine therapy, but not relapse interval were associated with an HR discordance in multivariable analysis. Loss of HR status was significantly associated with a risk of death (HR adjusted = 1.51, p = 0.002) while gain of HR and HER2 discordance was not. In conclusion, discordance of HR and HER2 expression between primary and metastatic breast cancer cannot be neglected. In addition, HR loss is associated with worse survival. Sampling metastatic sites is essential for treatment adjustment.

Well-differentiated and dedifferentiated liposarcomas (LPSs) are characterized by a systematic amplification of the MDM2 oncogene, which encodes a key negative regulator of the p53 pathway. The molecular mechanisms underlying MDM2 overexpression while sparing wild-type p53 in LPS remain poorly understood. Here, we show that the p53-independent metabolic functions of chromatin-bound MDM2 are exacerbated in LPS and mediate an addiction to serine metabolism that sustains nucleotide synthesis and tumor growth. Treatment of LPS cells with Nutlin-3A, a pharmacological inhibitor of the MDM2-p53 interaction, stabilized p53 but unexpectedly enhanced MDM2-mediated control of serine metabolism by increasing its recruitment to chromatin, likely explaining the poor clinical efficacy of this class of MDM2 inhibitors. In contrast, genetic or pharmacological inhibition of chromatin-bound MDM2 by SP141, a distinct MDM2 inhibitor triggering its degradation, or interfering with de novo serine synthesis, impaired LPS growth both in vitro and in clinically relevant patient-derived xenograft models. Our data indicate that targeting MDM2 functions in serine metabolism represents a potential therapeutic strategy for LPS.

In recent years, undifferentiated small round cell sarcomas (USRCSs) have been divided into a variety of new, rare, sarcoma subtypes, including the group of Ewing-like sarcomas, which have the morphological appearance of Ewing sarcomas, but carry CIC-DUX4, BCOR-CCNB3 and other gene fusions different from the classic EWSR1-ETS gene fusion. Using high-throughput RNA-sequencing (RNA-seq) analyses, we identified a novel recurrent gene fusion, CRTC1-SS18, in two cases of USRCS that lacked any known translocation. RNA-seq results were confirmed by reverse transcription polymerase chain reaction, long-range polymerase chain reaction, and fluorescence in situ hybridization. In vitro, we showed that the cells expressing the gene fusion were morphologically distinct and had enhanced oncogenic potential as compared with control cells. Expression profile comparisons with tumours of other sarcoma subtypes demonstrated that both cases clustered close to EWSR1-CREB1-positive tumours. Moreover, these analyses indicated enhanced NTRK1 expression in CRTC1-SS18-positive tumours. We conclude that the novel gene fusion identified in this study adds a new subtype to the USRCSs with unique gene signatures, and may be of therapeutic relevance. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.