Multifunctional role of the tumor associated monocytes/macrophages in the metastatic potential of inflammatory breast cancer.

Inflammatory breast cancer (IBC) is the most aggressive and lethal phenotype form of breast cancer, which afflicts young women at high incidence in North Africa compared to other continents of the world. IBC is characterized by highly metastatic behavior and possesses specific pathobiological properties different from non-IBC. IBC disease displays unusual common properties at typical presentation, including positive metastatic lymph-nodes, high infiltration of tumor associated monocytes/macrophages, rapid progression to distant metastasis, and possibly the production of a unique repertoire of growth factors, cytokines and chemokines, as well as a striking association with different polarized macrophages compared to non-IBC. Indeed, tumor associated monocytes/macrophages (TAM/M) play a crucial role in breast cancer development. Previously, we showed that cross talk between IBC cells and patient derived TAMs occurs via secretion of inflammatory mediators from TAMs that act on specific extracellular domain receptors activating down-stream signaling pathways that promote the epithelial-to-mesenchymal transition, cancer cell invasion, IBC stem cell properties, drug resistance, local and metastatic recurrence of residual tumor cells and other key markers of malignancy, including in vitro colony formation capacity. In this mini review, we will discuss the role of TAMs in IBC cancer metastatic potential and molecules involved. The review also discusses the recent discoveries in the field of IBC research.

Novel Inhibition of Central Carbon Metabolism Pathways by Rac and CDC42 inhibitor MBQ167 and Paclitaxel.

Triple negative breast cancer (TNBC) represents a therapeutic challenge in which standard chemotherapy is limited to paclitaxel. MBQ167, a clinical stage small molecule inhibitor that targets Rac and Cdc42, inhibits tumor growth and metastasis in mouse models of TNBC. Herein, we investigated the efficacy of MBQ167 in combination with paclitaxel in TNBC preclinical models, as a prelude to safety trials of this combination in patients with advanced breast cancer. Individual MBQ167 or combination therapy with paclitaxel was more effective at reducing TNBC cell viability and increasing apoptosis compared with paclitaxel alone. In orthotopic mouse models of human TNBC (MDA-MB231 and MDA-MB468), individual MBQ167, paclitaxel, or the combination reduced mammary tumor growth with similar efficacy, with no apparent liver toxicity. However, paclitaxel single agent treatment significantly increased lung metastasis, whereas MBQ167, single or combined, reduced lung metastasis. In the syngeneic 4T1/BALB/c model, combined MBQ167 and paclitaxel decreased established lung metastases by ∼80%. To determine the molecular basis for the improved efficacy of the combined treatment on metastasis, 4T1 tumor extracts from BALB/c mice treated with MBQ167, paclitaxel, or the combination were subjected to transcriptomic analysis. Gene set enrichment identified specific downregulation of central carbon metabolic pathways by the combination of MBQ167 and paclitaxel but not individual compounds. Biochemical validation, by immunoblotting and metabolic Seahorse analysis, shows that combined MBQ167 and paclitaxel reduces glycolysis. This study provides a strong rationale for the clinical testing of MBQ167 in combination with paclitaxel as a potential therapeutic for TNBC and identifies a unique mechanism of action.

Non-canonical mRNA translation initiation in cell stress and cancer.

The now well described canonical mRNA translation initiation mechanism of m7G 'cap' recognition by cap-binding protein eIF4E and assembly of the canonical pre-initiation complex consisting of scaffolding protein eIF4G and RNA helicase eIF4A has historically been thought to describe all cellular mRNA translation. However, the past decade has seen the discovery of alternative mechanisms to canonical eIF4E mediated mRNA translation initiation. Studies have shown that non-canonical alternate mechanisms of cellular mRNA translation initiation, whether cap-dependent or independent, serve to provide selective translation of mRNAs under cell physiological and pathological stress conditions. These conditions typically involve the global downregulation of canonical eIF4E1/cap-mediated mRNA translation, and selective translational reprogramming of the cell proteome, as occurs in tumor development and malignant progression. Cancer cells must be able to maintain physiological plasticity to acquire a migratory phenotype, invade tissues, metastasize, survive and adapt to severe microenvironmental stress conditions that involve inhibition of canonical mRNA translation initiation. In this review we describe the emerging, important role of non-canonical, alternate mechanisms of mRNA translation initiation in cancer, particularly in adaptation to stresses and the phenotypic cell fate changes involved in malignant progression and metastasis. These alternate translation initiation mechanisms provide new targets for oncology therapeutics development.

Genetics of enzymatic dysfunctions in metabolic disorders and cancer.

Inherited metabolic disorders arise from mutations in genes involved in the biogenesis, assembly, or activity of metabolic enzymes, leading to enzymatic deficiency and severe metabolic impairments. Metabolic enzymes are essential for the normal functioning of cells and are involved in the production of amino acids, fatty acids and nucleotides, which are essential for cell growth, division and survival. When the activity of metabolic enzymes is disrupted due to mutations or changes in expression levels, it can result in various metabolic disorders that have also been linked to cancer development. However, there remains much to learn regarding the relationship between the dysregulation of metabolic enzymes and metabolic adaptations in cancer cells. In this review, we explore how dysregulated metabolism due to the alteration or change of metabolic enzymes in cancer cells plays a crucial role in tumor development, progression, metastasis and drug resistance. In addition, these changes in metabolism provide cancer cells with a number of advantages, including increased proliferation, resistance to apoptosis and the ability to evade the immune system. The tumor microenvironment, genetic context, and different signaling pathways further influence this interplay between cancer and metabolism. This review aims to explore how the dysregulation of metabolic enzymes in specific pathways, including the urea cycle, glycogen storage, lysosome storage, fatty acid oxidation, and mitochondrial respiration, contributes to the development of metabolic disorders and cancer. Additionally, the review seeks to shed light on why these enzymes represent crucial potential therapeutic targets and biomarkers in various cancer types.

Breast cancer cell mesenchymal transition and metastasis directed by DAP5/eIF3d-mediated selective mRNA translation.

Cancer cell plasticity enables cell survival in harsh physiological environments and fate transitions such as the epithelial-to-mesenchymal transition (EMT) that underlies invasion and metastasis. Using genome-wide transcriptomic and translatomic studies, an alternate mechanism of cap-dependent mRNA translation by the DAP5/eIF3d complex is shown to be essential for metastasis, EMT, and tumor directed angiogenesis. DAP5/eIF3d carries out selective translation of mRNAs encoding EMT transcription factors and regulators, cell migration integrins, metalloproteinases, and cell survival and angiogenesis factors. DAP5 is overexpressed in metastatic human breast cancers associated with poor metastasis-free survival. In human and murine breast cancer animal models, DAP5 is not required for primary tumor growth but is essential for EMT, cell migration, invasion, metastasis, angiogenesis, and resistance to anoikis. Thus, cancer cell mRNA translation involves two cap-dependent mRNA translation mechanisms, eIF4E/mTORC1 and DAP5/eIF3d. These findings highlight a surprising level of plasticity in mRNA translation during cancer progression and metastasis.

eIF2Bδ blocks the integrated stress response and maintains eIF2B activity and cancer metastasis by overexpression in breast cancer stem cells.

Breast cancer (BC) metastasis involves cancer stem cells (CSCs) and their regulation by micro-RNAs (miRs), but miR targeting of the translation machinery in CSCs is poorly explored. We therefore screened miR expression levels in a range of BC cell lines, comparing non-CSCs to CSCs, and focused on miRs that target translation and protein synthesis factors. We describe a unique translation regulatory axis enacted by reduced expression of miR-183 in breast CSCs, which we show targets the eIF2Bδ subunit of guanine nucleotide exchange factor eIF2B, a regulator of protein synthesis and the integrated stress response (ISR) pathway. We report that reduced expression of miR-183 greatly increases eIF2Bδ protein levels, preventing strong induction of the ISR and eIF2α phosphorylation, by preferential interaction with P-eIF2α. eIF2Bδ overexpression is essential for BC cell invasion, metastasis, maintenance of metastases, and breast CSC expansion in animal models. Increased expression of eIF2Bδ, a site of action of the drug ISRIB that also prevents ISR signaling, is essential for breast CSC maintenance and metastatic capacity.

Macrophage-Derived 25-Hydroxycholesterol Promotes Vascular Inflammation, Atherogenesis, and Lesion Remodeling.

BACKGROUND: Cross-talk between sterol metabolism and inflammatory pathways has been demonstrated to significantly affect the development of atherosclerosis. Cholesterol biosynthetic intermediates and derivatives are increasingly recognized as key immune regulators of macrophages in response to innate immune activation and lipid overloading. 25-Hydroxycholesterol (25-HC) is produced as an oxidation product of cholesterol by the enzyme cholesterol 25-hydroxylase (CH25H) and belongs to a family of bioactive cholesterol derivatives produced by cells in response to fluctuating cholesterol levels and immune activation. Despite the major role of 25-HC as a mediator of innate and adaptive immune responses, its contribution during the progression of atherosclerosis remains unclear. METHODS: The levels of 25-HC were analyzed by liquid chromatography-mass spectrometry, and the expression of CH25H in different macrophage populations of human or mouse atherosclerotic plaques, respectively. The effect of CH25H on atherosclerosis progression was analyzed by bone marrow adoptive transfer of cells from wild-type or Ch25h-/- mice to lethally irradiated Ldlr-/- mice, followed by a Western diet feeding for 12 weeks. Lipidomic, transcriptomic analysis and effects on macrophage function and signaling were analyzed in vitro from lipid-loaded macrophage isolated from Ldlr-/- or Ch25h-/-;Ldlr-/- mice. The contribution of secreted 25-HC to fibrous cap formation was analyzed using a smooth muscle cell lineage-tracing mouse model, Myh11ERT2CREmT/mG;Ldlr-/-, adoptively transferred with wild-type or Ch25h-/- mice bone marrow followed by 12 weeks of Western diet feeding. RESULTS: We found that 25-HC accumulated in human coronary atherosclerotic lesions and that macrophage-derived 25-HC accelerated atherosclerosis progression, promoting plaque instability through autocrine and paracrine actions. 25-HC amplified the inflammatory response of lipid-loaded macrophages and inhibited the migration of smooth muscle cells within the plaque. 25-HC intensified inflammatory responses of lipid-laden macrophages by modifying the pool of accessible cholesterol in the plasma membrane, which altered Toll-like receptor 4 signaling, promoted nuclear factor-κB-mediated proinflammatory gene expression, and increased apoptosis susceptibility. These effects were independent of 25-HC-mediated modulation of liver X receptor or SREBP (sterol regulatory element-binding protein) transcriptional activity. CONCLUSIONS: Production of 25-HC by activated macrophages amplifies their inflammatory phenotype, thus promoting atherogenesis.

DDX60 selectively reduces translation off viral type II internal ribosome entry sites.

Co-opting host cell protein synthesis is a hallmark of many virus infections. In response, certain host defense proteins limit mRNA translation globally, albeit at the cost of the host cell's own protein synthesis. Here, we describe an interferon-stimulated helicase, DDX60, that decreases translation from viral internal ribosome entry sites (IRESs). DDX60 acts selectively on type II IRESs of encephalomyocarditis virus (EMCV) and foot and mouth disease virus (FMDV), but not by other IRES types or by 5' cap. Correspondingly, DDX60 reduces EMCV and FMDV (type II IRES) replication, but not that of poliovirus or bovine enterovirus 1 (BEV-1; type I IRES). Furthermore, replacing the IRES of poliovirus with a type II IRES is sufficient for DDX60 to inhibit viral replication. Finally, DDX60 selectively modulates the amount of translating ribosomes on viral and in vitro transcribed type II IRES mRNAs, but not 5' capped mRNA. Our study identifies a novel facet in the repertoire of interferon-stimulated effector genes, the selective downregulation of translation from viral type II IRES elements.

Inflammatory Breast Cancer: The Secretome of HCMV+ Tumor-Associated Macrophages Enhances Proliferation, Invasion, Colony Formation, and Expression of Cancer Stem Cell Markers.

Inflammatory breast cancer (IBC) is a highly aggressive phenotype of breast cancer that is characterized by a high incidence early metastasis. We previously reported a significant association of human cytomegalovirus (HCMV) DNA in the carcinoma tissues of IBC patients but not in the adjacent normal tissues. HCMV-infected macrophages serve as "mobile vectors" for spreading and disseminating virus to different organs, and IBC cancer tissues are highly infiltrated by tumor-associated macrophages (TAMs) that enhance IBC progression and promote breast cancer stem cell (BCSC)-like properties. Therefore, there is a need to understand the role of HCMV-infected TAMs in IBC progression. The present study aimed to test the effect of the secretome (cytokines and secreted factors) of TAMs derived from HCMV+ monocytes isolated from IBC specimens on the proliferation, invasion, and BCSC abundance when tested on the IBC cell line SUM149. HCMV+ monocytes were isolated from IBC patients during modified radical mastectomy surgery and tested in vitro for polarization into TAMs using the secretome of SUM149 cells. MTT, clonogenic, invasion, real-time PCR arrays, PathScan Intracellular Signaling array, and cytokine arrays were used to characterize the secretome of HCMV+ TAMs for their effect on the progression of SUM149 cells. The results showed that the secretome of HCMV+ TAMs expressed high levels of IL-6, IL-8, and MCP-1 cytokines compared to HCMV- TAMs. In addition, the secretome of HCMV+ TAMs induced the proliferation, invasion, colony formation, and expression of BCSC-related genes in SUM149 cells compared to mock untreated cells. In addition, the secretome of HCMV+ TAMs activated the phosphorylation of intracellular signaling molecules p-STAT3, p-AMPKα, p-PRAS40, and p-SAPK/JNK in SUM149 cells. In conclusion, this study shows that the secretome of HCMV+ TAMs enhances the proliferation, invasion, colony formation, and BCSC properties by activating the phosphorylation of p-STAT3, p-AMPKα, p-PRAS40, and p-SAPK/JNK intracellular signaling molecules in IBC cells.

Translational regulation of TFH cell differentiation and autoimmune pathogenesis.

Little is known regarding T cell translational regulation. We demonstrate that T follicular helper (TFH) cells use a previously unknown mechanism of selective messenger RNA (mRNA) translation for their differentiation, role in B cell maturation, and in autoimmune pathogenesis. We show that TFH cells have much higher levels of translation factor eIF4E than non-TFH CD4+ T cells, which is essential for translation of TFH cell fate-specification mRNAs. Genome-wide translation studies indicate that modest down-regulation of eIF4E activity by a small-molecule inhibitor or short hairpin RN impairs TFH cell development and function. In mice, down-regulation of eIF4E activity specifically reduces TFH cells among T helper subtypes, germinal centers, B cell recruitment, and antibody production. In experimental autoimmune encephalomyelitis, eIF4E activity down-regulation blocks TFH cell participation in disease pathogenesis while promoting rapid remission and spinal cord remyelination. TFH cell development and its role in autoimmune pathogenesis involve selective mRNA translation that is highly druggable.

Ganoderma lucidum enhances carboplatin chemotherapy effect by inhibiting the DNA damage response pathway and stemness.

Inflammatory Breast Cancer (IBC) is a rare and aggressive type of breast cancer with a poor prognosis. Its management is challenging because of a lack of targeted therapies, increased metastatic potential, and high recurrence rates. Interest in using platinum agents such as carboplatin emerged from data suggesting frequent DNA repair defects in breast cancer. Because studies show that medicinal mushroom Ganoderma lucidum (GLE) sensitizes cancer cells to radiation and other drugs; herein, we aimed to investigate the therapeutic potential of GLE, alone or in combination with carboplatin in breast cancer models. Our studies were focused on the regulation of the DNA Damage Response (DDR) and on cancer cell stemness. Carboplatin and GLE were tested in vitro using the IBC cell line, SUM-149, breast cancer non-IBC cells, MDA-MB-231, and in vivo using IBC xenograft models. Our results show that the GLE/carboplatin combination decreased cell viability, induced cell death by two different mechanisms, and delayed the response to DNA damage. Furthermore, the combination suppressed mammosphere formation and the expression of cancer stemness proteins. In xenograft models, the combination showed significant tumor growth inhibitory effects without systemic toxicity. This study emphasizes the potential of this dual therapy for IBC patients.

Melanoma-Secreted Amyloid Beta Suppresses Neuroinflammation and Promotes Brain Metastasis.

Brain metastasis is a significant cause of morbidity and mortality in multiple cancer types and represents an unmet clinical need. The mechanisms that mediate metastatic cancer growth in the brain parenchyma are largely unknown. Melanoma, which has the highest rate of brain metastasis among common cancer types, is an ideal model to study how cancer cells adapt to the brain parenchyma. Our unbiased proteomics analysis of melanoma short-term cultures revealed that proteins implicated in neurodegenerative pathologies are differentially expressed in melanoma cells explanted from brain metastases compared with those derived from extracranial metastases. We showed that melanoma cells require amyloid beta (Aß) for growth and survival in the brain parenchyma. Melanoma-secreted Aß activates surrounding astrocytes to a prometastatic, anti-inflammatory phenotype and prevents phagocytosis of melanoma by microglia. Finally, we demonstrate that pharmacologic inhibition of Aß decreases brain metastatic burden. SIGNIFICANCE: Our results reveal a novel mechanistic connection between brain metastasis and Alzheimer's disease, two previously unrelated pathologies; establish Aß as a promising therapeutic target for brain metastasis; and demonstrate suppression of neuroinflammation as a critical feature of metastatic adaptation to the brain parenchyma. This article is highlighted in the In This Issue feature, p. 1171.

Ribosome profiling reveals novel regulation of C9ORF72 GGGGCC repeat-containing RNA translation.

GGGGCC (G4C2) repeat expansion in the first intron of C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia. Repeat-containing RNA is translated into dipeptide repeat (DPR) proteins, some of which are neurotoxic. Using dynamic ribosome profiling, we identified three translation initiation sites in the intron upstream of (G4C2) repeats; these sites are detected irrespective of the presence or absence of the repeats. During translocation, ribosomes appear to be stalled on the repeats. An AUG in the preceding C9ORF72 exon initiates a uORF that inhibits downstream translation. Polysome isolation indicates that unspliced (G4C2) repeat-containing RNA is a substrate for DPR protein synthesis. (G4C2) repeat-containing RNA translation is 5' cap-independent but inhibited by the initiation factor DAP5, suggesting an interplay with uORF function. These results define novel translational mechanisms of expanded (G4C2) repeat-containing RNA in disease.

A DAP5/eIF3d alternate mRNA translation mechanism promotes differentiation and immune suppression by human regulatory T cells.

Regulatory T cells (Treg cells) inhibit effector T cells and maintain immune system homeostasis. Treg cell maturation in peripheral sites requires inhibition of protein kinase mTORC1 and TGF-beta-1 (TGF-beta). While Treg cell maturation requires protein synthesis, mTORC1 inhibition downregulates it, leaving unanswered how Treg cells achieve essential mRNA translation for development and immune suppression activity. Using human CD4+ T cells differentiated in culture and genome-wide transcription and translation profiling, here we report that TGF-beta transcriptionally reprograms naive T cells to express Treg cell differentiation and immune suppression mRNAs, while mTORC1 inhibition impairs translation of T cell mRNAs but not those induced by TGF-beta. Rather than canonical mTORC1/eIF4E/eIF4G translation, Treg cell mRNAs utilize the eIF4G homolog DAP5 and initiation factor eIF3d in a non-canonical translation mechanism that requires cap-dependent binding by eIF3d directed by Treg cell mRNA 5' noncoding regions. Silencing DAP5 in isolated human naive CD4+ T cells impairs their differentiation into Treg cells. Treg cell differentiation is mediated by mTORC1 downregulation and TGF-beta transcriptional reprogramming that establishes a DAP5/eIF3d-selective mechanism of mRNA translation.

AUF1 gene transfer increases exercise performance and improves skeletal muscle deficit in adult mice.

Muscle function and mass begin declining in adults long before evidence of sarcopenia and include reduced mitochondrial function, although much remains to be characterized. We found that mRNA decay factor AU-rich mRNA binding factor 1 (AUF1), which stimulates myogenesis, is strongly reduced in skeletal muscle of adult and older mice in the absence of evidence of sarcopenia. Muscle-specific adeno-associated virus (AAV)8-AUF1 gene therapy increased expression of AUF1, muscle function, and mass. AAV8 AUF1 muscle gene transfer in 12-month-old mice increased the levels of activated muscle stem (satellite) cells, increased muscle mass, reduced markers of muscle atrophy, increased markers of mitochondrial content and muscle fiber oxidative capacity, and enhanced exercise performance to levels of 3-month-old mice. With wild-type and AUF1 knockout mice and cultured myoblasts, AUF1 supplementation of muscle fibers was found to increase expression of Peroxisome Proliferator-activated Receptor Gamma Co-activator 1-alpha (PGC1α), a major effector of skeletal muscle mitochondrial oxidative metabolism. AUF1 stabilized and increased translation of the pgc1α mRNA, which is strongly reduced in adult muscle in the absence of AUF1 supplementation. Skeletal muscle-specific gene transfer of AUF1 therefore restores muscle mass, increases exercise endurance, and may provide a therapeutic strategy for age-related muscle loss.

m7G tRNA modification reveals new secrets in the translational regulation of cancer development.

Orellana et al. (2021) and Dai et al. (2021) demonstrate that increased m7G modification of a subset of tRNAs by the METTL1/WDR4 complex stabilizes these mRNAs against decay, increases translation efficiency, reduces ribosome pausing, is associated with poor survival in human cancers, and is directly transforming.

Phase 0 Clinical Trial of Everolimus in Patients with Vestibular Schwannoma or Meningioma.

Inhibition of mTORC1 signaling has been shown to diminish growth of meningiomas and schwannomas in preclinical studies, and clinical data suggest that everolimus, an orally administered mTORC1 inhibitor, may slow tumor progression in a subset of patients with neurofibromatosis type 2 (NF2) with vestibular schwannoma. To assess the pharmacokinetics, pharmacodynamics, and potential mechanisms of treatment resistance, we performed a presurgical (phase 0) clinical trial of everolimus in patients undergoing elective surgery for vestibular schwannoma or meningiomas. Eligible patients with meningioma or vestibular schwannoma requiring tumor resection enrolled on study received everolimus 10 mg daily for 10 days immediately prior to surgery. Everolimus blood levels were determined immediately before and after surgery. Tumor samples were collected intraoperatively. Ten patients completed protocol therapy. Median pre- and postoperative blood levels of everolimus were found to be in a high therapeutic range (17.4 ng/mL and 9.4 ng/mL, respectively). Median tumor tissue drug concentration determined by mass spectrometry was 24.3 pg/mg (range, 9.2-169.2). We observed only partial inhibition of phospho-S6 in the treated tumors, indicating incomplete target inhibition compared with control tissues from untreated patients (P = 0.025). Everolimus led to incomplete inhibition of mTORC1 and downstream signaling. These data may explain the limited antitumor effect of everolimus observed in clinical studies for patients with NF2 and will inform the design of future preclinical and clinical studies targeting mTORC1 in meningiomas and schwannomas.

Inhibiting LXRα phosphorylation in hematopoietic cells reduces inflammation and attenuates atherosclerosis and obesity in mice.

Atherosclerosis and obesity share pathological features including inflammation mediated by innate and adaptive immune cells. LXRα plays a central role in the transcription of inflammatory and metabolic genes. LXRα is modulated by phosphorylation at serine 196 (LXRα pS196), however, the consequences of LXRα pS196 in hematopoietic cell precursors in atherosclerosis and obesity have not been investigated. To assess the importance of LXRα phosphorylation, bone marrow from LXRα WT and S196A mice was transplanted into Ldlr-/- mice, which were fed a western diet prior to evaluation of atherosclerosis and obesity. Plaques from S196A mice showed reduced inflammatory monocyte recruitment, lipid accumulation, and macrophage proliferation. Expression profiling of CD68+ and T cells from S196A mouse plaques revealed downregulation of pro-inflammatory genes and in the case of CD68+ upregulation of mitochondrial genes characteristic of anti-inflammatory macrophages. Furthermore, S196A mice had lower body weight and less visceral adipose tissue; this was associated with transcriptional reprograming of the adipose tissue macrophages and T cells, and resolution of inflammation resulting in less fat accumulation within adipocytes. Thus, reducing LXRα pS196 in hematopoietic cells attenuates atherosclerosis and obesity by reprogramming the transcriptional activity of LXRα in macrophages and T cells to promote an anti-inflammatory phenotype.

Nanopore Identification of Single Nucleotide Mutations in Circulating Tumor DNA by Multiplexed Ligation.

BACKGROUND: Circulating tumor DNAs (ctDNAs) are highly promising cancer biomarkers, potentially applicable for noninvasive liquid biopsy and disease monitoring. However, to date, sequencing of ctDNAs has proven to be challenging primarily due to small sample size and high background of fragmented cell-free DNAs (cfDNAs) derived from normal cells in the circulation, specifically in early stage cancer. METHODS: Solid-state nanopores (ssNPs) have recently emerged as a highly efficient tool for single-DNA sensing and analysis. Herein, we present a rapid nanopore genotyping strategy to enable an amplification-free identification and classification of ctDNA mutations. A biochemical ligation detection assay was used for the creation of specific fluorescently-labelled short DNA reporter molecules. Color conjugation with multiple fluorophores enabled a unique multi-color signature for different mutations, offering multiplexing potency. Single-molecule readout of the fluorescent labels was carried out by electro-optical sensing via solid-state nanopores drilled in titanium oxide membranes. RESULTS: As proof of concept, we utilized our method to detect the presence of low-quantity ERBB2 F310S and PIK3Ca H1047R breast cancer mutations from both plasmids and xenograft mice blood samples. We demonstrated an ability to distinguish between a wild type and a mutated sample, and between the different mutations in the same sample. CONCLUSIONS: Our method can potentially enable rapid and low cost ctDNA analysis that completely circumvents PCR amplification and library preparation. This approach will thus meet a currently unmet demand in terms of sensitivity, multiplexing and cost, opening new avenues for early diagnosis of cancer.