An international consensus on effective, inclusive, and career-spanning short-format training in the life sciences and beyond.

Science, technology, engineering, mathematics, and medicine (STEMM) fields change rapidly and are increasingly interdisciplinary. Commonly, STEMM practitioners use short-format training (SFT) such as workshops and short courses for upskilling and reskilling, but unaddressed challenges limit SFT's effectiveness and inclusiveness. Education researchers, students in SFT courses, and organizations have called for research and strategies that can strengthen SFT in terms of effectiveness, inclusiveness, and accessibility across multiple dimensions. This paper describes the project that resulted in a consensus set of 14 actionable recommendations to systematically strengthen SFT. A diverse international group of 30 experts in education, accessibility, and life sciences came together from 10 countries to develop recommendations that can help strengthen SFT globally. Participants, including representation from some of the largest life science training programs globally, assembled findings in the educational sciences and encompassed the experiences of several of the largest life science SFT programs. The 14 recommendations were derived through a Delphi method, where consensus was achieved in real time as the group completed a series of meetings and tasks designed to elicit specific recommendations. Recommendations cover the breadth of SFT contexts and stakeholder groups and include actions for instructors (e.g., make equity and inclusion an ethical obligation), programs (e.g., centralize infrastructure for assessment and evaluation), as well as organizations and funders (e.g., professionalize training SFT instructors; deploy SFT to counter inequity). Recommendations are aligned with a purpose-built framework-"The Bicycle Principles"-that prioritizes evidenced-based teaching, inclusiveness, and equity, as well as the ability to scale, share, and sustain SFT. We also describe how the Bicycle Principles and recommendations are consistent with educational change theories and can overcome systemic barriers to delivering consistently effective, inclusive, and career-spanning SFT.

Assessing the Diagnostic Yield of Targeted Next-Generation Sequencing for Melanoma and Gastrointestinal Tumors.

A common rationale in molecular diagnostic laboratories is that implementation of next-generation sequencing (NGS) enables simultaneous multigene testing, allowing increased information benefit compared with non-NGS assays. However, minimal published data exist to support this justification. The current study compared clinical diagnostic yield of TruSight Tumor 26 Sequencing Panel (TST26) in melanoma, colorectal (CRC), and gastrointestinal stromal (GIST) tumors with non-NGS assays. A total of 1041 formalin-fixed, paraffin-embedded tumors, of melanoma, CRC, and GIST, were profiled. NGS results were compared with non-NGS single-gene or single-variant assays with respect to variant output and diagnostic yield. A total of 79% melanoma and 94% CRC tumors were variant positive by panel testing. TST26 panel improved serine/threonine-protein kinase B-raf (BRAF) variant detection in melanoma compared with single-variant BRAF Val600Glu/Lys (V600E/K) routine tests by 24% and detected variants in genes other than BRAF, NRAS, and KIT, which could impact patient management in 20% additional cases. NGS enhanced diagnostic yield in CRC by 36% when compared with routine single-gene assays. In contrast, no added benefit of NGS-based testing for GIST tumors was observed. TST26 panel either missed or inaccurately called complex insertion/deletion variants in KIT exon 11, which were accurately identified by non-NGS methods. Findings of this study demonstrate the differential impact of cancer site and variant type on diagnostic test information yield from NGS assays.

Latency and interval therapy affect the evolution in metastatic colorectal cancer.

While comparison of primary tumor and metastases has highlighted genomic heterogeneity in colorectal cancer (CRC), previous studies have focused on a single metastatic site or limited genomic testing. Combining data from whole exome and ultra-deep targeted sequencing, we explored possible evolutionary trajectories beyond the status of these mutations, particularly among patient-matched metastatic tumors. Our findings confirm the persistence of known clinically-relevant mutations (e.g., those of RAS family of oncogenes) in CRC primary and metastases, yet reveal that latency and interval systemic therapy affect the course of evolutionary events within metastatic lesions. Specifically, our analysis of patient-matched primary and multiple metastatic lesions, developed over time, showed a similar genetic composition for liver metastatic tumors, which were 21-months apart. This genetic makeup was different from those identified in lung metastases developed before manifestation of the second liver metastasis. These results underscore the role of latency in the evolutionary path of metastatic CRC and may have implications for future treatment options.

Somatic Tumor Variant Filtration Strategies to Optimize Tumor-Only Molecular Profiling Using Targeted Next-Generation Sequencing Panels.

A common approach in clinical diagnostic laboratories to variant assessment from tumor molecular profiling is sequencing of genomic DNA extracted from both tumor (somatic) and normal (germline) tissue, with subsequent variant comparison to identify true somatic variants with potential impact on patient treatment or prognosis. However, challenges exist in paired tumor-normal testing, including increased cost of dual sample testing and identification of germline cancer predisposing variants. Alternatively, somatic variants can be identified by in silico tumor-only variant filtration precluding the need for matched normal testing. The barrier to tumor-only variant filtration is defining a reliable approach, with high sensitivity and specificity to identify somatic variants. In this study, we used retrospective data sets from paired tumor-normal samples tested on small (48 gene) and large (555 gene) targeted next-generation sequencing panels, to model algorithms for tumor-only variants classification. The optimal algorithm required an ordinal filtering approach using information from variant population databases (1000 Genomes Phase 3, ESP6500, ExAC), clinical mutation databases (ClinVar), and information on recurring clinically relevant somatic variants. Overall the tumor-only variant filtration strategy described in this study can define clinically relevant somatic variants from tumor-only analysis with sensitivity of 97% to 99% and specificity of 87% to 94%, and with significant potential utility for clinical laboratories implementing tumor-only molecular profiling.

Minimally Invasive Real-Time Detection of Actionable Mutations in Patients With Metastatic Solid Tumors Using Fine-Needle and Liquid Biopsies.

PURPOSE: Fine-needle biopsy (FNB) and liquid biopsy are minimally invasive methods of tumor sampling that provide feasible means to assess tumor genotypes in real time. However, more data are needed to establish the strength of these methods by benchmarking against the current gold standard methods, core-needle biopsy (CNB) or surgical excision of the tumor. PATIENTS AND METHODS: Eligible patients with advanced solid tumors were prospectively recruited. We performed mutation profiling using matched tumor DNA obtained by CNB, FNB and liquid biopsy, and matrix-assisted laser desorption/ionization time-of-flight custom mass-spectrometry or targeted next-generation DNA sequencing. The actionability of detected mutations was determined using the OncoKB Web tool. Agreement between mutations detected in CNBs, FNBs, and circulating tumor DNA (ctDNA) was examined. RESULTS: Forty-one patients underwent tumor biopsy. Thirty CNBs (73%) and 34 FNBs (83%) had sufficient tumor and DNA for mutation profiling. Median DNA yield from CNB and FNB were 775 ng (interquartile range, 240 to 347 4ng) and 649 ng (interquartile range, 180 to1350 ng), respectively. Of 29 CNB/FNB pairs available for comparison, actionable mutation results were concordant in 28 (96%). Six of nine actionable mutations (67%) that were found by CNB, FNB, or both were detectable in ctDNA. Two additional actionable mutations were found exclusively in ctDNA. CONCLUSION: Optimally processed FNB and liquid biopsy can be used routinely for tumor mutation profiling to identify actionable mutations.

Improving validation methods for molecular diagnostics: application of Bland-Altman, Deming and simple linear regression analyses in assay comparison and evaluation for next-generation sequencing.

AIMS: A standard approach in test evaluation is to compare results of the assay in validation to results from previously validated methods. For quantitative molecular diagnostic assays, comparison of test values is often performed using simple linear regression and the coefficient of determination (R2), using R2 as the primary metric of assay agreement. However, the use of R2 alone does not adequately quantify constant or proportional errors required for optimal test evaluation. More extensive statistical approaches, such as Bland-Altman and expanded interpretation of linear regression methods, can be used to more thoroughly compare data from quantitative molecular assays. METHODS: We present the application of Bland-Altman and linear regression statistical methods to evaluate quantitative outputs from next-generation sequencing assays (NGS). NGS-derived data sets from assay validation experiments were used to demonstrate the utility of the statistical methods. RESULTS: Both Bland-Altman and linear regression were able to detect the presence and magnitude of constant and proportional error in quantitative values of NGS data. Deming linear regression was used in the context of assay comparison studies, while simple linear regression was used to analyse serial dilution data. Bland-Altman statistical approach was also adapted to quantify assay accuracy, including constant and proportional errors, and precision where theoretical and empirical values were known. CONCLUSIONS: The complementary application of the statistical methods described in this manuscript enables more extensive evaluation of performance characteristics of quantitative molecular assays, prior to implementation in the clinical molecular laboratory.

Integration of Technical, Bioinformatic, and Variant Assessment Approaches in the Validation of a Targeted Next-Generation Sequencing Panel for Myeloid Malignancies.

CONTEXT: - Detection of variants in hematologic malignancies is increasingly important because of a growing number of variants impacting diagnosis, prognosis, and treatment response, and as potential therapeutic targets. The use of next-generation sequencing technologies to detect variants in hematologic malignancies in a clinical diagnostic laboratory setting allows for efficient identification of routinely tested markers in multiple genes simultaneously, as well as the identification of novel and rare variants in other clinically relevant genes. OBJECTIVE: - To apply a systematic approach to evaluate and validate a commercially available next-generation sequencing panel (TruSight Myeloid Sequencing Panel, Illumina, San Diego, California) targeting 54 genes. In this manuscript, we focused on the parameters that were used to evaluate assay performance characteristics. DATA SOURCES: - Analytical validation was performed using samples containing known variants that had been identified previously. Cases were selected from different disease types, with variants in a range of genes. Panel performance characteristics were assessed and genomic regions requiring additional analysis or wet-bench approaches identified. CONCLUSIONS: - We validated the performance characteristics of a myeloid next-generation sequencing panel for detection of variants. The TruSight Myeloid Sequencing Panel covers more than 95% of target regions with depth greater than 500×. However, because of unique variant types such as large insertions or deletions or genomic regions of high GC content, variants in CEBPA, FLT3, and CALR required supplementation with non-next-generation sequencing assays or with informatics approaches to address deficiencies in performance. The use of multiple bioinformatics approaches (2 variant callers and informatics scripts) allows for maximizing calling of true positives, while identifying limitations in using either method alone.

Molecular profiling of advanced solid tumors and patient outcomes with genotype-matched clinical trials: the Princess Margaret IMPACT/COMPACT trial.

BACKGROUND: The clinical utility of molecular profiling of tumor tissue to guide treatment of patients with advanced solid tumors is unknown. Our objectives were to evaluate the frequency of genomic alterations, clinical "actionability" of somatic variants, enrollment in mutation-targeted or other clinical trials, and outcome of molecular profiling for advanced solid tumor patients at the Princess Margaret Cancer Centre (PM). METHODS: Patients with advanced solid tumors aged ≥18 years, good performance status, and archival tumor tissue available were prospectively consented. DNA from archival formalin-fixed paraffin-embedded tumor tissue was tested using a MALDI-TOF MS hotspot panel or a targeted next generation sequencing (NGS) panel. Somatic variants were classified according to clinical actionability and an annotated report included in the electronic medical record. Oncologists were provided with summary tables of their patients' molecular profiling results and available mutation-specific clinical trials. Enrolment in genotype-matched versus genotype-unmatched clinical trials following release of profiling results and response by RECIST v1.1 criteria were evaluated. RESULTS: From March 2012 to July 2014, 1893 patients were enrolled and 1640 tested. After a median follow-up of 18 months, 245 patients (15 %) who were tested were subsequently treated on 277 therapeutic clinical trials, including 84 patients (5 %) on 89 genotype-matched trials. The overall response rate was higher in patients treated on genotype-matched trials (19 %) compared with genotype-unmatched trials (9 %; p < 0.026). In a multi-variable model, trial matching by genotype (p = 0.021) and female gender (p = 0.034) were the only factors associated with increased likelihood of treatment response. CONCLUSIONS: Few advanced solid tumor patients enrolled in a prospective institutional molecular profiling trial were treated subsequently on genotype-matched therapeutic trials. In this non-randomized comparison, genotype-enrichment of early phase clinical trials was associated with an increased objective tumor response rate. TRIAL REGISTRATION: NCT01505400 (date of registration 4 January 2012).

Comparison of Next-Generation Sequencing Panels and Platforms for Detection and Verification of Somatic Tumor Variants for Clinical Diagnostics.

Use of next-generation sequencing to detect somatic variants in DNA extracted from formalin-fixed, paraffin-embedded tumor tissues poses a challenge for clinical molecular diagnostic laboratories because of variable DNA quality and quantity, and the potential to detect low allele frequency somatic variants difficult to verify by non-next-generation sequencing methods. We evaluated somatic variant detection performance of the MiSeq and Ion Proton benchtop sequencers using two commercially available panels, the TruSeq Amplicon Cancer Panel and the AmpliSeq Cancer Hotspot Panel Version 2. Both the MiSeq-TruSeq Amplicon Cancer Panel and Ion Proton-AmpliSeq Cancer Hotspot Panel Version 2 were comparable in terms of detection of somatic variants and allele frequency determination using DNA extracted from tumor tissue. Concordance was 100% between the panels for detection of somatic variants in genomic regions tested by both panels, including 27 variants present at low somatic allele frequency (<15%). Use of both the MiSeq and Ion Proton platforms in a combined workflow enabled detection of potentially actionable variants with importance for patient diagnosis, prognosis, or treatment in 49% (305/621) of cases. Overall, a combined workflow using both platforms enabled successful molecular profiling of 96% (621/644) of tumor samples, and provided an approach for verification of somatic variants not amenable to verification by Sanger sequencing (<15% variant allele frequency).

A classification system for clinical relevance of somatic variants identified in molecular profiling of cancer.

PURPOSE: Interpretation systems for clinical laboratory reporting of genetic variants for inherited conditions have been widely published. By contrast, there are no existing systems for interpretation and classification of somatic variants found from molecular testing of cancer. METHODS: We designed an assessment protocol and classification system for somatic variants identified through next-generation sequencing molecular profiling of tumor-derived samples and applied these to a pilot dataset of somatic variants found by next-generation sequencing profiling of 158 tumor samples derived from advanced cancer patients examined at the Princess Margaret Cancer Centre. RESULTS: We present a classification system to interpret the significance of genetic variants in molecular analysis of cancer, including the following key factors: (i) known or predicted pathogenicity of the variant; (ii) primary site and tumor histology in which the variant is found; (iii) recurrence of the variant; and (iv) evidence of clinical actionability. We used these factors to develop a five-category somatic variant classification for simplified reporting of variant interpretations to treating oncologists. CONCLUSION: Our somatic variant classification can be of practical value to other clinical molecular laboratories performing cancer genetic profiling by promoting consistent reporting of somatic variants and permitting harmonization of variant data among laboratories and clinical studies.

Inhibition of the Mitochondrial Protease ClpP as a Therapeutic Strategy for Human Acute Myeloid Leukemia.

From an shRNA screen, we identified ClpP as a member of the mitochondrial proteome whose knockdown reduced the viability of K562 leukemic cells. Expression of this mitochondrial protease that has structural similarity to the cytoplasmic proteosome is increased in leukemic cells from approximately half of all patients with AML. Genetic or chemical inhibition of ClpP killed cells from both human AML cell lines and primary samples in which the cells showed elevated ClpP expression but did not affect their normal counterparts. Importantly, Clpp knockout mice were viable with normal hematopoiesis. Mechanistically, we found that ClpP interacts with mitochondrial respiratory chain proteins and metabolic enzymes, and knockdown of ClpP in leukemic cells inhibited oxidative phosphorylation and mitochondrial metabolism.

Carnitine transporter CT2 (SLC22A16) is over-expressed in acute myeloid leukemia (AML) and target knockdown reduces growth and viability of AML cells.

AML (acute myeloid leukemia) cells have a unique reliance on mitochondrial metabolism and fatty acid oxidation (FAO). Thus, blocking FAO is a potential therapeutic strategy to target these malignant cells. In the current study, we assessed plasma membrane carnitine transporters as novel therapeutic targets for AML. We examined the expression of the known plasma membrane carnitine transporters, OCTN1, OCTN2, and CT2 in AML cell lines and primary AML samples and compared expression to normal hematopoietic cells. Of the three carnitine transporters, CT2 demonstrated the greatest differential expression between AML and normal cells. Using shRNA, we knocked down CT2 and demonstrated that target knockdown impaired the function of the transporter. In addition, knockdown of CT2 reduced the growth and viability of AML cells with high expression of CT2 (OCI-AML2 and HL60), but not low expression. CT2 knockdown reduced basal oxygen consumption without a concomitant increase in glycolysis. Thus, CT2 may be a novel target for a subset of AML.

Select microtubule inhibitors increase lysosome acidity and promote lysosomal disruption in acute myeloid leukemia (AML) cells.

To identify new biological vulnerabilities in acute myeloid leukemia, we screened a library of natural products for compounds cytotoxic to TEX leukemia cells. This screen identified the novel small molecule Deoxysappanone B 7,4' dimethyl ether (Deox B 7,4), which possessed nanomolar anti-leukemic activity. To determine the anti-leukemic mechanism of action of Deox B 7,4, we conducted a genome-wide screen in Saccharomyces cerevisiae and identified enrichment of genes related to mitotic cell cycle as well as vacuolar acidification, therefore pointing to microtubules and vacuolar (V)-ATPase as potential drug targets. Further investigations into the mechanisms of action of Deox B 7,4 and a related analogue revealed that these compounds were reversible microtubule inhibitors that bound near the colchicine site. In addition, Deox B 7,4 and its analogue increased lysosomal V-ATPase activity and lysosome acidity. The effects on microtubules and lysosomes were functionally important for the anti-leukemic effects of these drugs. The lysosomal effects were characteristic of select microtubule inhibitors as only the Deox compounds and nocodazole, but not colchicine, vinca alkaloids or paclitaxel, altered lysosome acidity and induced lysosomal disruption. Thus, our data highlight a new mechanism of action of select microtubule inhibitors on lysosomal function.

AML cells have low spare reserve capacity in their respiratory chain that renders them susceptible to oxidative metabolic stress.

Mitochondrial respiration is a crucial component of cellular metabolism that can become dysregulated in cancer. Compared with normal hematopoietic cells, acute myeloid leukemia (AML) cells and patient samples have higher mitochondrial mass, without a concomitant increase in respiratory chain complex activity. Hence these cells have a lower spare reserve capacity in the respiratory chain and are more susceptible to oxidative stress. We therefore tested the effects of increasing the electron flux through the respiratory chain as a strategy to induce oxidative stress and cell death preferentially in AML cells. Treatment with the fatty acid palmitate induced oxidative stress and cell death in AML cells, and it suppressed tumor burden in leukemic cell lines and primary patient sample xenografts in the absence of overt toxicity to normal cells and organs. These data highlight a unique metabolic vulnerability in AML, and identify a new therapeutic strategy that targets abnormal oxidative metabolism in this malignancy.

A randomized phase II study of cediranib alone versus cediranib in combination with dasatinib in docetaxel resistant, castration resistant prostate cancer patients.

BACKGROUND: Activation of the vascular endothelial growth factor receptor (VEGFR) and the oncogenic Src pathway has been implicated in the development of castration-resistant prostate cancer (CRPC) in preclinical models. Cediranib and dasatinib are multi-kinase inhibitors targeting VEGFR and Src respectively. Phase II studies of cediranib and dasatinib in CRPC have shown single agent activity. METHODS: Docetaxel-pretreated CRPC patients were randomized to arm A: cediranib alone (20 mg/day) versus arm B: cediranib (20 mg/day) plus dasatinib (100 mg/day) given orally on 4-week cycles. Primary endpoint was 12-week progression-free survival (PFS) as per the Prostate Cancer Clinical Trials Working Group (PCWG2). Patient reported outcomes were evaluated using Functional Assessment of Cancer Therapy-Prostate (FACT-P) and Present Pain Intensity (PPI) scales. Correlative studies of bone turnover markers (BTM), including bone alkaline phosphate (BAP) and serum beta-C telopeptide (B-CTx) were serially assayed. Results A total of 22 patients, 11 per arm, were enrolled. Baseline demographics were similar in both arms. Median number of cycles =4 in arm A (range 1-12) and 2 in arm B (range 1-9). Twelve-week PFS was 73 % in arm A versus 18 % in arm B (p = 0.03). Median PFS in months (arm A versus B) was: 5.2 versus 2.6 (95 % CI: 1.9-6.5 versus 1.4-not reached). Most common grade 3 toxicities were hypertension, anemia and thrombocytopenia in arm A and hypertension, diarrhea and fatigue in arm B. One treatment-related death (retroperitoneal hemorrhage) was seen in arm A. FACT-P and PPI scores did not significantly change in either arm. No correlation between BTM and PFS was seen in either arm. CONCLUSIONS: Although limited by small numbers, this randomized study showed that the combination of VEGFR and Src targeted therapy did not result in improved efficacy and may be associated with a worse outcome than VEGFR targeted therapy alone in patients with CRPC. ClinicalTrials.gov number: NCT01260688.

Mutations in UBA3 confer resistance to the NEDD8-activating enzyme inhibitor MLN4924 in human leukemic cells.

The NEDD8-activating enzyme (NAE) initiates neddylation, the cascade of post-translational NEDD8 conjugation onto target proteins. MLN4924, a selective NAE inhibitor, has displayed preclinical anti-tumor activity in vitro and in vivo, and promising clinical activity has been reported in patients with refractory hematologic malignancies. Here, we sought to understand the mechanisms of resistance to MLN4924. K562 and U937 leukemia cells were exposed over a 6 month period to MLN4924 and populations of resistant cells (R-K562(MLN), R-U937(MLN)) were selected. R-K562(MLN) and R-U937(MLN) cells contain I310N and Y352H mutations in the NAE catalytic subunit UBA3, respectively. Biochemical analyses indicate that these mutations increase the enzyme's affinity for ATP while decreasing its affinity for NEDD8. These mutations effectively contribute to decreased MLN4924 potency in vitro while providing for sufficient NAE function for leukemia cell survival. Finally, R-K562(MLN) cells showed cross-resistance to other NAE-selective inhibitors, but remained sensitive to a pan-E1 (activating enzyme) inhibitor. Thus, our work provides insight into mechanisms of MLN4924 resistance to facilitate the development of more effective second-generation NAE inhibitors.

Metabolic adaptation to chronic inhibition of mitochondrial protein synthesis in acute myeloid leukemia cells.

Recently, we demonstrated that the anti-bacterial agent tigecycline preferentially induces death in leukemia cells through the inhibition of mitochondrial protein synthesis. Here, we sought to understand mechanisms of resistance to tigecycline by establishing a leukemia cell line resistant to the drug. TEX leukemia cells were treated with increasing concentrations of tigecycline over 4 months and a population of cells resistant to tigecycline (RTEX+TIG) was selected. Compared to wild type cells, RTEX+TIG cells had undetectable levels of mitochondrially translated proteins Cox-1 and Cox-2, reduced oxygen consumption and increased rates of glycolysis. Moreover, RTEX+TIG cells were more sensitive to inhibitors of glycolysis and more resistant to hypoxia. By electron microscopy, RTEX+TIG cells had abnormally swollen mitochondria with irregular cristae structures. RNA sequencing demonstrated a significant over-representation of genes with binding sites for the HIF1α:HIF1ß transcription factor complex in their promoters. Upregulation of HIF1α mRNA and protein in RTEX+TIG cells was confirmed by Q-RTPCR and immunoblotting. Strikingly, upon removal of tigecycline from RTEX+TIG cells, the cells re-established aerobic metabolism. Levels of Cox-1 and Cox-2, oxygen consumption, glycolysis, mitochondrial mass and mitochondrial membrane potential returned to wild type levels, but HIF1α remained elevated. However, upon re-treatment with tigecycline for 72 hours, the glycolytic phenotype was re-established. Thus, we have generated cells with a reversible metabolic phenotype by chronic treatment with an inhibitor of mitochondrial protein synthesis. These cells will provide insight into cellular adaptations used to cope with metabolic stress.

Lysosomal disruption preferentially targets acute myeloid leukemia cells and progenitors.

Despite efforts to understand and treat acute myeloid leukemia (AML), there remains a need for more comprehensive therapies to prevent AML-associated relapses. To identify new therapeutic strategies for AML, we screened a library of on- and off-patent drugs and identified the antimalarial agent mefloquine as a compound that selectively kills AML cells and AML stem cells in a panel of leukemia cell lines and in mice. Using a yeast genome-wide functional screen for mefloquine sensitizers, we identified genes associated with the yeast vacuole, the homolog of the mammalian lysosome. Consistent with this, we determined that mefloquine disrupts lysosomes, directly permeabilizes the lysosome membrane, and releases cathepsins into the cytosol. Knockdown of the lysosomal membrane proteins LAMP1 and LAMP2 resulted in decreased cell viability, as did treatment of AML cells with known lysosome disrupters. Highlighting a potential therapeutic rationale for this strategy, leukemic cells had significantly larger lysosomes compared with normal cells, and leukemia-initiating cells overexpressed lysosomal biogenesis genes. These results demonstrate that lysosomal disruption preferentially targets AML cells and AML progenitor cells, providing a rationale for testing lysosomal disruption as a novel therapeutic strategy for AML.

Suppression of cancer progression by MGAT1 shRNA knockdown.

Oncogenic signaling promotes tumor invasion and metastasis, in part, by increasing the expression of tri- and tetra- branched N-glycans. The branched N-glycans bind to galectins forming a multivalent lattice that enhances cell surface residency of growth factor receptors, and focal adhesion turnover. N-acetylglucosaminyltransferase I (MGAT1), the first branching enzyme in the pathway, is required for the addition of all subsequent branches. Here we have introduced MGAT1 shRNA into human HeLa cervical and PC-3-Yellow prostate tumor cells lines, generating cell lines with reduced transcript, enzyme activity and branched N-glycans at the cell surface. MGAT1 knockdown inhibited HeLa cell migration and invasion, but did not alter cell proliferation rates. Swainsonine, an inhibitor of α-mannosidase II immediately downstream of MGAT1, also inhibited cell invasion and was not additive with MGAT1 shRNA, consistent with a common mechanism of action. Focal adhesion and microfilament organization in MGAT1 knockdown cells also indicate a less motile phenotype. In vivo, MGAT1 knockdown in the PC-3-Yellow orthotopic prostate cancer xenograft model significantly decreased primary tumor growth and the incidence of lung metastases. Our results demonstrate that blocking MGAT1 is a potential target for anti-cancer therapy.