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In the absence of targeted treatment options, neoadjuvant chemotherapy (NACT) is applied widely for triple-negative breast cancer (TNBC). Response to NACT is an important parameter predictive of oncological outcomes (progression-free and overall survival). An approach to the evaluation of predictive markers enabling therapy individualization is the identification of tumor driver genetic mutations. This study was conducted to investigate the role of SEC62, harbored at 3q26 and identified as a driver of breast cancer pathogenesis, in TNBC. We analyzed SEC62 expression in The Cancer Genome Atlas database, and immunohistologically investigated SEC62 expression in pre- and post-NACT tissue samples from 64 patients with TNBC treated at the Department of Gynecology and Obstetrics/Saarland University Hospital/Homburg between January 2010 and December 2018 and compared the effect of SEC62 on tumor cell migration and proliferation in functional assays. SEC62 expression dynamics correlated positively with the response to NACT (p ≤ 0.01) and oncological outcomes (p ≤ 0.01). SEC62 expression stimulated tumor cell migration (p ≤ 0.01). The study findings indicate that SEC62 is overexpressed in TNBC and serves as a predictive marker for the response to NACT, a prognostic marker for oncological outcomes, and a migration-stimulating oncogene in TNBC.

Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.

The human Sec61 complex is a widely distributed and abundant molecular machine. It resides in the membrane of the endoplasmic reticulum to channel two types of cargo: protein substrates and calcium ions. The SEC61A1 gene encodes for the pore-forming Sec61α subunit of the Sec61 complex. Despite their ubiquitous expression, the idiopathic SEC61A1 missense mutations p.V67G and p.T185A trigger a localized disease pattern diagnosed as autosomal dominant tubulointerstitial kidney disease (ADTKD–SEC61A1). Using cellular disease models for ADTKD–SEC61A1, we identified an impaired protein transport of the renal secretory protein renin and a reduced abundance of regulatory calcium transporters, including SERCA2. Treatment with the molecular chaperone phenylbutyrate reversed the defective protein transport of renin and the imbalanced calcium homeostasis. Signal peptide substitution experiments pointed at targeting sequences as the cause for the substrate-specific impairment of protein transport in the presence of the V67G or T185A mutations. Similarly, dominant mutations in the signal peptide of renin also cause ADTKD and point to impaired transport of this renal hormone as important pathogenic feature for ADTKD–SEC61A1 patients as well.

Cancer immune-surveillance is essential for the inhibition of carcinogenesis. Malignantly transformed cells can be recognised by both the innate and adaptive immune systems through different mechanisms. Immune effector cells induce extrinsic cell death in the identified tumour cells by expressing death ligand cytokines of the tumour necrosis factor ligand family. However, some tumour cells can escape immune elimination and progress. Acquisition of resistance to the death-ligand induced apoptotic pathway can be obtained through cleavage of effector-cell expressed death-ligands into a poorly active form, mutations or silencing of the death receptors or overexpression of decoy receptors and pro-survival proteins. Although the immune system is highly effective in the elimination of malignantly transformed cells, abnormal/ dysfunctional death-ligand signalling curbs its cytotoxicity. Moreover, death receptors can also transmit pro-survival and pro-migratory signals. Consequently, dysfunctional death receptor-mediated apoptosis/necroptosis signalling does not only give a passive resistance against cell death, but actively drives tumour cell motility, invasion and contributes to consequent metastasis. This dual contribution of the death ligand-death receptor signalling in both the early, elimination phase and then in the late, escape phase of the tumour immunoediting process is discussed in this review. Death receptor agonists still hold potential for cancer therapy since they can execute the tumour-eliminating immune-effector function even in the absence of activation of the immune system against the tumour. The opportunities and challenges of developing death receptor agonists into effective cancer therapeutics are also discussed.

Introduction- The mainstream therapy for AML is cytarabine (AraC) and anthracycline-based intensive chemotherapy. Between 10-40% of patients however have a refractory disease. It is becoming increasingly accepted that the risk for refractory disease could be reduced by finding better ways of selecting the induction therapy. While multiple in vitro and in vivo experimental models exist for pre-clinical drug efficacy testing, they are either labour intensive, too time consuming or generate variable results, making them unsuitable for clinical application. Furthermore, very few, if any of these methods have been shown to replicate the clinical response of patients. The aim of this study was to develop a functional drug testing system that can rapidly and faithfully predict the clinical response of the patient and therefore be utilized to help the identification of patients suitable for AraC+daunorubicin (DnR) therapy. Methods- Primary samples were obtained through Blood Cancer Biobank Ireland. All patients were consented and the research project was approved by the local Research Ethics Committee of NUI, Galway. Mononuclear AML blasts were isolated from bone marrow (BM) aspirates of newly diagnosed patients by ficoll-paque gradient separation. HS-5 human bone marrow mesenchymal stromal cells (BMSC), healthy donor (HD)-derived BMSCs immortalised with hTERT (iMSC) and primary BMSCs (non-immortalised, pBMSC) from HDs and AML patients were used as feeder layers. Cytokine and chemokine secretion by BMSCs was determined using antibody arrays (R&D systems). Extracellular matrix (ECM) scaffold formation was determined by immunocytochemical detection of collagen I, III, IV, V, VI, laminin and fibronectin. AML blasts were cultured in direct contact on established BMSC feeder layer. BMSCs were identifiable by either GFP expression or green cell tracker labelling (CFSE) and the percentage of dying AML cells (negative for GFP/CFSE and positive for the viability dye, ToPro-3) was determined with FACS. Results- In order to choose the most suitable BMSC feeder layer, three main characteristics were studied: cytokine/chemokine secretion, formation of ECM-BMSC proteocellular scaffold and ability to support ex vivo AML blast survival were determined. HS-5 cells, iMSCs and primary, HD pBMSC secreted 66, 59 and 51 paracrine factors, respectively including angiopoietin 1, fibroblast growth factor, interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte colony stimulating factor (G-CSF), C-X-C motif chemokine 12 (CXCL12), CXCL10 and vascular endothelial growth factor. 51% of cytokines/chemokines were common between iMSCs and HD pBMSC, while the HS-5 secretome shared 43% commonality with HD pBMSC. iMSCs also showed an equal ability to establish an ECM-BMSC scaffold with HD pBMSC and they had a superior ability to support the ex vivo survival of AML blasts over HS-5 cells. To determine how closely iMSCs can replicate the effects of BMSCs of AML patients, AML blasts were cultured on matching BMSCs (BMSCs isolated from the same patient). When these AML-BMSC co-cultures were exposed to the BH3 mimetics ABT-199 and ABT-737 or AraC+DnR, iMSCs closely replicated the protective effect of the patients' own BMSCs. Using this optimized ex vivo co-culture model, we tested 16 AML patient samples by exposing iMSC-AML blast co-cultures to a clinically-relevant dosage of AraC+DnR. To quantify drug efficacy, the area under the curve (AUC) for each treatment timepoint (24 h and 48 h) was calculated. By applying a cut-off value of 35% efficacy, we found that the ex vivo test could predict the clinical response of the patient in 81.2% of cases (p-value= 0.002, Figure). Conclusions- The developed drug efficacy test can recapitulate the key features of the BM microenvironment and could predict the clinical response of patients with high accuracy. The advantages of this model over more complex pre-clinical AML models is its suitability to be developed into a laboratory diagnostic tool which could greatly advance the clinical decision on treatment choice. Figure. Figure. Disclosures Quinn: Janssen: Honoraria.