Highlights d NF1 is a GAP-independent estrogen receptor transcription co-repressor d Somatic NF1 loss causes tamoxifen/aromatase inhibitor resistance in ER + breast cancer d A MEK inhibitor plus a SERD is effective in NF1 -ER + PDX and cell line models

Microscaled proteogenomics was deployed to probe the molecular basis for differential response to neoadjuvant carboplatin and docetaxel combination chemotherapy for triple-negative breast cancer (TNBC). Proteomic analyses of pre-treatment patient biopsies uniquely revealed metabolic pathways, including oxidative phosphorylation, adipogenesis and fatty acid metabolism, that were resistance-associated. Both proteomics and transcriptomics revealed sensitivity was marked by elevation of DNA repair, E2F targets, G2M checkpoint, interferon-gamma signaling and immune checkpoint components. Proteogenomic analyses of somatic copy number aberrations identified a resistance-associated 19q13.31-33 deletion where LIG1, POLD1 and XRCC1 are located. In orthogonal datasets, LIG1 (DNA ligase I) gene deletion and/or low mRNA expression levels were associated with lack of pathological complete response, higher chromosomal instability (CIN) and poor prognosis in TNBC, as well as carboplatin-selective resistance in TNBC pre-clinical models. Hemizygous loss of LIG1 was also associated with higher CIN and poor prognosis in other cancer types, demonstrating broader clinical implications.

Corresponding author: Valeria I Fink, Pasaje Peluffo 3932,

Purpose The early months of the COVID-19 pandemic led to reduced cancer screenings and delayed cancer surgeries. We used insurance claims data to understand how breast cancer incidence and treatment after diagnosis changed nationwide over the course of the pandemic. Methods Using the Optum Research Database from January 2017 to March 2021, including approximately 19 million US adults with commercial health insurance, we identified new breast cancer diagnoses and first treatment after diagnosis. We compared breast cancer incidence and proportion of newly diagnosed patients receiving pre-operative systemic therapy pre-COVID, in the first 2 months of the COVID pandemic and in the later part of the COVID pandemic. Results Average monthly breast cancer incidence was 19.3 (95% CI 19.1–19.5) cases per 100,000 women and men pre-COVID, 11.6 (95% CI 10.8–12.4) per 100,000 in April–May 2020, and 19.7 (95% CI 19.3–20.1) per 100,000 in June 2020–February 2021. Use of pre-operative systemic therapy was 12.0% (11.7–12.4) pre-COVID, 37.7% (34.9–40.7) for patients diagnosed March–April 2020, and 14.8% (14.0–15.7) for patients diagnosed May 2020–January 2021. The changes in breast cancer incidence across the pandemic did not vary by demographic factors. Use of pre-operative systemic therapy across the pandemic varied by geographic region, but not by area socioeconomic deprivation or race/ethnicity. Conclusion In this US-insured population, the dramatic changes in breast cancer incidence and the use of pre-operative systemic therapy experienced in the first 2 months of the pandemic did not persist, although a modest change in the initial management of breast cancer continued.

The estrogen receptor (ER) has been targeted for breast cancer treatment for over a century, but many challenges persist. ER-positivity identifies the largest breast cancer subgroup, and ER-directed therapies prolong survival and improve symptoms in the advanced setting with a very favorable side effect profile. Treatment strategies have included decreasing estrogen synthesis and modulating or degrading the ER. However, ER+ breast cancer once diagnosed in the advanced setting still represents an incurable condition. Many efforts are ongoing to circumvent resistance mechanisms with a few strategies already incorporated into clinical practice such as the combination of endocrine agents with drugs that interfere with other signaling pathways and cell-cycle progression. Important questions remain as how best to select each available strategy, how to sequence them and ultimately how to extend benefits to the largest number of patients in need.