Introduction: Netherton syndrome (NS) is a rare and severe ichthyosis characterized by superficial scaling, skin inflammation, a specific hair shaft defect, severe atopic manifestations and multisystemic complications. It is an orphan disease with currently no satisfactory treatment. NS is caused by loss-offunction mutations in SPINK5 encoding the serine protease inhibitor LEKTI. NS patients present with ichthyosiform erythroderma or ichthyosis linearis circumflexa and show considerable clinical variability. Areas covered: Uncontrolled serine protease activity leads to a profound skin barrier defect and the release of pro-inflammatory and pro-allergic mediators by keratinocytes and immune cells. Improved understanding of NS pathogenesis has led to the successful use of repurposed biologics such as intravenous immunoglobulins and anti-IL-17A blockers. Between April 1, 2020 and November 18, 2020, authors searched for NS-relevant information in the following databases: MEDLINE, DrugBank, ClinicalTrials.gov, and patent datasets accessed through lens.org. Expert opinion: Specific KLK5 and/or KLK7 inhibitors represent the most promising disease-modifying treatments. They are currently being developed by several companies. Comprehension of the determinants of NS variability, flares and modification over time will be the foundation for precision medicine. While improved knowledge of the inflammatory and allergic pathways involved is still needed, clinical trials using repurposed biologics have already begun.

IntroductionChemotherapy resistance resulting in incomplete pathologic response is associated with high risk of metastasis and early relapse in breast cancer. The aim of this study was to identify and evaluate biomarkers of treatment-resistant tumor cells.MethodsWe performed a cell surface marker screen in triple-negative breast cancer patient-derived xenograft models treated with standard care genotoxic chemotherapy. Global expression profiling was used to further characterize the identified treatment-resistant subpopulations.ResultsHigh expression of sialyl-glycolipid stage-specific embryonic antigen 4 (SSEA4) was found in residual tumor cells surviving chemotherapy and in samples from metastatic patients who relapsed after neoadjuvant chemotherapy. Gene and microRNA (miRNA) expression profiling linked SSEA4 positivity with a mesenchymal phenotype and a deregulation of drug resistance pathways. Functional assays demonstrated a direct link between epithelial–mesenchymal transition (EMT) and SSEA4 expression. Interestingly, SSEA4 expression, EMT, and drug resistance seemed to be regulated posttranscriptionally. Finally, high expression of CMP-N-acetylneuraminate-β-galactosamide-α-2,3-sialyltransferase 2 (ST3GAL2), the rate-limiting enzyme of SSEA4 synthesis, was found to be associated with poor clinical outcome in breast and ovarian cancer patients treated with chemotherapy.ConclusionsIn this study, we identified SSEA4 as highly expressed in a subpopulation of tumor cells resistant to multiple commonly used chemotherapy drugs, as well as ST3GAL2, the rate-limiting enzyme of SSEA4 synthesis, as a predictive marker of poor outcome for breast and ovarian cancer patients undergoing chemotherapy. Both biomarkers and additionally identified regulatory miRNAs may be used to further understand chemoresistance, to stratify patient groups in order to avoid ineffective and painful therapies, and to develop alternative treatment regimens for breast cancer patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0652-6) contains supplementary material, which is available to authorized users.