Clinical proteomics reveals vulnerabilities in non-invasive breast ductal carcinoma and drives personalized treatment strategies.

Ductal carcinoma in situ (DCIS) is the most common type (80%) of non-invasive breast lesions in women. The lack of validated prognostic markers, limited patient numbers, and variable tissue quality have a significant impact on diagnosis, risk stratification, patient enrolment, and the results of clinical studies. Here, we performed label-free quantitative proteomics on 50 clinical formalin-fixed, paraffin embedded biopsies, validating 22 putative biomarkers from independent genetic studies. Our comprehensive proteomic phenotyping reveals more than 380 differentially expressed proteins and metabolic vulnerabilities, that can inform new therapeutic strategies for DCIS and invasive ductal carcinoma (IDC). Due to the readily druggable nature of proteins and metabolic enzymes or metabolism inhibitors, this study is of high interest for clinical research and pharmaceutical industry. To further evaluate our findings, and to promote the clinical translation of our study, we developed a highly multiplexed targeted proteomics assay for 90 proteins associated with cancer metabolism, RNA regulation and signature cancer pathways, such as PI3K/AKT/mTOR and EGFR/RAS/RAF.