Biobanking and research quality: think locally, act globally.

Although biobanks can support research across geographic and governance boundaries, biomedical researchers consistently describe preferences for either collaborating with local biobanks or establishing their own biobanks. This article summarizes the potential research impacts of local biobank use and suggests how descriptions of biospecimen provenance can be improved in research publications.

Does IPSS-R down staging before transplantation improve the prognosis of patients with Myelodysplastic neoplasms?

In MDS patients higher IPSS-R at transplant is associated with worse transplant outcome. Thus, it may seem beneficial to improve IPSS-R by therapeutic intervention prior to transplantation in order to "down-stage" the disease risk. However, there is no evidence to date to support this approach. A retrospective analysis of the EBMT transplant registry was performed to investigate the role of therapeutic interventions prior to transplantation with regard to changes in IPSS-R and transplant outcomes. A total of 1482 MDS patients with sufficient data to calculate IPSS-R at diagnosis and at time of transplantation were selected and analysed for transplant outcome in a multivariable Cox model including IPSS-R at diagnosis, treatment intervention, change in IPSS-R before transplant and several patient and transplant variables. Transplant outcome was unaffected by IPSS-R change in untreated patients and moderately superior in chemotherapy-treated patients with improved IPSS-R at transplant. Improved IPSS-R after hypomethylating agents (HMA) or other therapies showed no beneficial effect. However, when IPSS-R progressed after chemotherapy, (HMA) or other therapies, transplant outcome was worse than without any prior treatment. Similar results were found when reduction or increase in bone marrow (BM) blasts between diagnosis and transplantation was considered. The results show a limited benefit of IPSS-R down staging or reduction of BM blasts after chemotherapy and no benefit for HMA or other treatments and thus question the role of prior therapy in MDS patients scheduled for transplantation. The model-based survival estimates should help inform decision making for both doctors and patients.

Misspellings or "miscellings"-Non-verifiable and unknown cell lines in cancer research publications.

Reproducible laboratory research relies on correctly identified reagents. We have previously described gene research papers with wrongly identified nucleotide sequence(s), including papers studying miR-145. Manually verifying reagent identities in 36 recent miR-145 papers found that 56% and 17% of papers described misidentified nucleotide sequences and cell lines, respectively. We also found 5 cell line identifiers in miR-145 papers with misidentified nucleotide sequences and cell lines, and 18 cell line identifiers published elsewhere, that did not represent indexed human cell lines. These 23 identifiers were described as non-verifiable (NV), as their identities were unclear. Studying 420 papers that mentioned 8 NV identifier(s) found 235 papers (56%) that referred to 7 identifiers (BGC-803, BSG-803, BSG-823, GSE-1, HGC-7901, HGC-803, and MGC-823) as independent cell lines. We could not find any publications describing how these cell lines were established. Six cell lines were sourced from cell line repositories with externally accessible online catalogs, but these cell lines were not indexed as claimed. Some papers also stated that short tandem repeat (STR) profiles had been generated for three cell lines, yet no STR profiles could be identified. In summary, as NV cell lines represent new challenges to research integrity and reproducibility, further investigations are required to clarify their status and identities.

Protection of the human gene research literature from contract cheating organizations known as research paper mills.

Human gene research generates new biology insights with translational potential, yet few studies have considered the health of the human gene literature. The accessibility of human genes for targeted research, combined with unreasonable publication pressures and recent developments in scholarly publishing, may have created a market for low-quality or fraudulent human gene research articles, including articles produced by contract cheating organizations known as paper mills. This review summarises the evidence that paper mills contribute to the human gene research literature at scale and outlines why targeted gene research may be particularly vulnerable to systematic research fraud. To raise awareness of targeted gene research from paper mills, we highlight features of problematic manuscripts and publications that can be detected by gene researchers and/or journal staff. As improved awareness and detection could drive the further evolution of paper mill-supported publications, we also propose changes to academic publishing to more effectively deter and correct problematic publications at scale. In summary, the threat of paper mill-supported gene research highlights the need for all researchers to approach the literature with a more critical mindset, and demand publications that are underpinned by plausible research justifications, rigorous experiments and fully transparent reporting.

Rare germline variants in childhood cancer patients suspected of genetic predisposition to cancer.

Identification of cancer-predisposing germline variants in childhood cancer patients is important for therapeutic decisions, disease surveillance and risk assessment for patients, and potentially, also for family members. We investigated the spectrum and prevalence of pathogenic germline variants in selected childhood cancer patients with features suggestive of genetic predisposition to cancer. Germline DNA was subjected to exome sequencing to filter variants in 1048 genes of interest including 176 known cancer predisposition genes (CPGs). An enrichment burden analysis compared rare deleterious germline CPG variants in the patient cohort with those in a healthy aged control population. A subset of predicted deleterious variants in novel candidate CPGs was investigated further by examining matched tumor samples, and the functional impact of AXIN1 variants was analyzed in cultured cells. Twenty-two pathogenic/likely pathogenic (P/LP) germline variants detected in 13 CPGs were identified in 19 of 76 patients (25.0%). Unclear association with the diagnosed cancer types was observed in 11 of 19 patients carrying P/LP CPG variants. The burden of rare deleterious germline variants in autosomal dominant CPGs was significantly higher in study patients versus healthy aged controls. A novel AXIN1 frameshift variant (Ser321fs) may impact the regulation of ß-catenin levels. Selection of childhood cancer patients for germline testing based on features suggestive of an underlying genetic predisposition could help to identify carriers of clinically relevant germline CPG variants, and streamline the integration of germline genomic testing in the pediatric oncology clinic.

Trends in autologous stem cell transplantation for newly diagnosed multiple myeloma: Changing demographics and outcomes in European Society for Blood and Marrow Transplantation centres from 1995 to 2019.

Multiple myeloma (MM) accounts for 10% of haematological malignancies. Overall survival (OS) has improved in recent years due to increased use of autologous stem cell transplantation (ASCT) in the treatment of newly diagnosed MM and the advent of novel agents, including proteasome inhibitors, immunomodulatory drugs and monoclonal antibodies. To assess trends in ASCT including patient selection, choice of induction regimen, depth of response and survival, we performed a retrospective analysis of all patients undergoing first ASCT for MM in European Society for Blood and Marrow Transplantation centres between 1995 and 2019. A total of 117 711 patients across 575 centres were included. The number of transplants performed increased sevenfold across the study period. The median age increased from 55 to 61 years, and the percentage of patients aged >65 years rose from 7% to 30%. Use of chemotherapy-based induction fell significantly, being largely replaced by bortezomib-based regimens. The two-year complete response rate increased from 22% to 42%. The five-year progression-free survival and OS rates increased from 28% to 31% and from 52% to 69%, respectively. Transplant mortality fell from 5.9% to 1.5%. Ongoing advances in MM treatment may challenge the future role of ASCT. However, at the current time, ASCT remains central to the MM treatment paradigm.

Cytogenetic risk classification maintains its prognostic significance in transplanted FLT3-ITD mutated acute myeloid leukemia patients: On behalf of the acute leukemia working party/European society of blood and marrow transplantation.

FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutational status is a pivotal prognosticator in acute myeloid leukemia (AML) patients and significantly increases the risk of disease relapse. However, it remains unclear whether in FLT3-ITD patients referred for allogeneic stem cell transplantation (allo-SCT), baseline cytogenetics significantly impacts clinical outcome. Using the European Society of Blood and Marrow Transplantation registry, we performed a retrospective analysis of 1631 FLT3-ITD AML patients who underwent allo-SCT with the aim of determining the influence of cytogenetic risk category on patient outcomes. Median patient age was 49 years and median follow-up duration was 36 months. Two-year leukemia-free survival (LFS) and incidence of relapse were 54% and 31.6%, respectively. Non-relapse mortality was experienced by 14.4% with a 2-year overall survival (OS) of 60.1%. On multivariate analysis, LFS was significantly lower in patients with intermediate and adverse risk cytogenetics compared with those with favorable risk cytogenetics, (hazard ratio [HR] = 1.48, 95% confidence interval [CI], 1.06-2.06; p = .02), and (HR = 01.65, 95% CI, 1.13-2.40; p = .009), respectively. OS was significantly lower in patients with adverse risk cytogenetics compared with patients with favorable risk cytogenetics (HR = 1.74, 95% CI, 1.16-2.61; p = .008) with a trend toward lower OS in patients with intermediate risk cytogenetics compared to those with favorable risk cytogenetics (HR = 1.43, 95% CI, 1.00-2.05; p = .052). In addition, adverse risk patients and intermediate risk patients experienced higher relapse rates compared with favorable risk patients (HR = 1.83, 95% CI, 1.13-2.94; p = .013 and HR = 1.82, 95% CI, 1.19-2.77; p = .005). Overall, cytogenetic studies aid in refinement of risk stratification in transplanted FLT3-ITD AML patients.

The Australia and New Zealand Cardio-Oncology Registry: evaluation of chemotherapy-related cardiotoxicity in a national cohort of paediatric cancer patients.

Cancer therapy related cardiac dysfunction (CTRCD) is an area of increasing focus, particularly during the survivorship period, for paediatric, adolescent and adult cancer survivors. With the advent of immunotherapy and targeted therapy, there is a new set of mechanisms from which paediatric and young adult patients with cancer may suffer cardiovascular injury. Furthermore, cardiovascular disease is the leading cause of morbidity and mortality in the survivorship period. The recently established Australian Cardio-Oncology Registry is the largest and only population-based cardiotoxicity database of paediatric and adolescent and young adult oncology patients in the world, and the first paediatric registry that will document cardiotoxicity caused by chemotherapy and novel targeted therapies using a prospective approach. The database is designed for comprehensive data collection and evaluation of the Australian practice in terms of diagnosis and management of CTRCD. Using the Australian Cardio-Oncology Registry critical clinical information will be collected regarding predisposing factors for the development of CTRCD, the rate of subclinical left ventricular dysfunction and transition to overt heart failure, further research into protectant molecules against cardiac dysfunction and aid in the discovery of which genetic variants predispose to CTRCD. A health economic arm of the study will assess the cost/benefit of both the registry and cardio-oncology clinical implementation. Finally, an imaging arm will establish if exercise cardiac magnetic resonance imaging and VO2 max testing is a more sensitive predictor of cardiac reserve in paediatric and adolescent and young adult oncology patients exposed to cardiac toxic therapies.

Improving Academic Biobank Value and Sustainability Through an Outputs Focus.

Although it is generally accepted that human tissue biobanks are important to facilitate progress in health and medical research, many academic biobanks face sustainability challenges. We propose that biobank sustainability is challenged by a lack of available data describing the outputs and benefits that are produced by biobanks, as reflected by a dearth of publications that enumerate biobank outputs. We further propose that boosting the available information on biobank outputs and using a broader range of output metrics will permit economic analyses such as cost-consequence analyses of biobank activity. Output metrics and cost-consequence analyses can allow biobanks to achieve efficiencies, and improve the quality and/or quantity of their outputs. In turn, biobank output measures provide all stakeholders with explicit and accountable data on biobank value, which could contribute to the evolution of biobank operations to best match research needs, and mitigate some threats to biobank sustainability.

Predictors of Success of Phase II Pediatric Oncology Clinical Trials.

BACKGROUND: There are limited data to predict which novel childhood cancer therapies are likely to be successful. To help rectify this, we sought to identify the factors that impact the success of phase II clinical trials for pediatric malignancies. MATERIALS AND METHODS: We examined the impact of 24 preclinical and trial design variables for their influence on 132 phase II pediatric oncology clinical trials. Success was determined by an objective assessment of patient response, with data analyzed using Fisher's exact test, Pearson's chi-square test, and logistic regression models. RESULTS: Trials that evaluated patients with a single histological cancer type were more successful than those that assessed multiple different cancer types (68% vs. 47%, 27%, and 17% for 1, 2-3, 4-7, and 8+; p < .005). Trials on liquid or extracranial solid tumors were more successful than central nervous system or combined trials (70%, 60%, 38%, and 24%; p < .005), and trials of combination therapies were more successful than single agents (71% vs. 28%; p < .005). Trials that added therapies to standard treatment backbones were more successful than trials testing novel therapies alone or those that incorporated novel agents (p < .005), and trials initiated based on the results of adult studies were less likely to succeed (p < .05). For 61% of trials (80/132), we were unable to locate any relevant preclinical findings to support the trial. When preclinical studies were carried out (52/132), there was no evidence that the conduct of any preclinical experiments made the trial more likely to succeed (p < .005). CONCLUSION: Phase II pediatric oncology clinical trials that examine a single cancer type and use combination therapies have the highest possibility of clinical success. Trials building upon a standard treatment regimen were also more successful. The conduct of preclinical experiments did not improve clinical success, emphasizing the need for a better understanding of the translational relevance of current preclinical testing paradigms. IMPLICATIONS FOR PRACTICE: To improve the clinical outcomes of phase II childhood cancer trials, this study identified factors impacting clinical success. These results have the potential to impact not only the design of future clinical trials but also the assessment of preclinical studies moving forward. This work found that trials on one histological cancer type and trials testing combination therapies had the highest possibility of success. Incorporation of novel therapies into standard treatment backbones led to higher success rates than testing novel therapies alone. This study found that most trials had no preclinical evidence to support initiation, and even when preclinical studies were available, they did not result in improved success.

"I remember how I felt, but I don't remember the gene": Families' experiences of cancer-related genetic testing in childhood.

BACKGROUND: Genetic testing in children for hereditary cancer predisposition syndromes (CPSs) involves unique psychosocial and family-systems considerations. This retrospective study explored the perspectives and emotional reactions of parents and young adults about cancer-related genetic counseling and testing offered to children in the family. METHODS: Families were eligible if they had considered genetic testing for a child (≤18 years) within the family. Parents and young adults ≥16 years participated in semistructured interviews that we coded and identified key themes. We also quantitively assessed emotional distress, quality of life, impact of receiving genetic cancer risk information, and service-related satisfaction. RESULTS: From 35 interviews (26 parents, nine young adults), we identified themes spanning families' experiences from referral to genetic services to the longer term impact of receiving information about family cancer risk from testing of children. Supported by quantitative data, families generally described positive experiences of genetic services and reported benefits to genetic testing. Nevertheless, families faced unique emotional and relational challenges that changed over the family lifecycle. Those challenges differed according to whether the child was asymptomatic or had a cancer diagnosis at testing. Parents of children with cancer described genetic consultations as a secondary concern to the immediate stressors of their child's treatment. CONCLUSIONS: We conclude that the successful integration of cancer genetics into pediatric cancer care requires specialist pediatric genetic counseling and psychosocial support services that are able to respond to families' changing needs.

Investigation of clinically relevant germline variants detected by next-generation sequencing in patients with childhood cancer: a review of the literature.

Genetic predisposition is an important underlying cause of childhood cancer, although the proportion of patients with childhood cancer carrying predisposing pathogenic germline variants is uncertain. This review considers the pathogenic or likely pathogenic germline variants reported by six studies that used next-generation sequencing to investigate genetic predisposition in selected cohorts of patients with childhood cancer and used incompletely overlapping gene sets for analysis and interpretation. These six studies reported that 8.5%-35.5% of patients with childhood cancer carried clinically relevant germline variants. Analysis of 52 autosomal dominant cancer predisposition genes assumed common to all six studies showed that 5.5%-25.8% of patients with childhood cancer carried pathogenic or likely pathogenic germline variants in at least one of these genes. When only non-central nervous system solid tumours (excluding adrenocortical carcinomas) were considered, 8.5%-10.3% of the patients carried pathogenic or likely pathogenic germline variants in at least one of 52 autosomal dominant cancer predisposition genes. There was a lack of concordance between the genotype and phenotype in 33.3%-57.1% of the patients reported with pathogenic or likely pathogenic germline variants, most of which represented variants in autosomal dominant cancer predisposition genes associated with adult onset cancers. In summary, germline genetic testing in patients with childhood cancer requires clear definition of phenotypes and genes considered for interpretation, with potential to inform and broaden childhood cancer predisposition syndromes.

Identification and epidemiological analysis of Perostrongylus falciformis infestation in Irish badgers.

BACKGROUND: The lungworm, Perostrongylus falciformis (fomerly known as Aelurostrongylus falciformis) has been identified in badgers (Meles meles) in Britain, the Russian Federation, Italy, Norway, Poland, Ukraine, Bosnia Herzegovina and Romania, while Aelurostrongylus pridhami has been reported from badgers in Spain. RESULTS: Pulmonary tissue from 1580 Irish badgers was examined and an estimated prevalence of 32.09% (95% CI: 29.79-34.45%) of this parasite was detected. Confirmation of its occurrence was made by PCR analysis on a subset of the population. CONCLUSION: Infestation was widely distributed throughout the Republic of Ireland, with a trend towards higher infestation risk in western versus eastern counties. In addition males were at a higher risk of infestation than females and juveniles were at a significantly higher risk than adult badgers.

Acute acinar pancreatitis blocks vesicle-associated membrane protein 8 (VAMP8)-dependent secretion, resulting in intracellular trypsin accumulation.

Zymogen secretory granules in pancreatic acinar cells express two vesicle-associated membrane proteins (VAMP), VAMP2 and -8, each controlling 50% of stimulated secretion. Analysis of secretion kinetics identified a first phase (0-2 min) mediated by VAMP2 and second (2-10 min) and third phases (10-30 min) mediated by VAMP8. Induction of acinar pancreatitis by supramaximal cholecystokinin (CCK-8) stimulation inhibits VAMP8-mediated mid- and late-phase but not VAMP2-mediated early-phase secretion. Elevation of cAMP during supramaximal CCK-8 mitigates third-phase secretory inhibition and acinar damage caused by the accumulation of prematurely activated trypsin. VAMP8-/- acini are resistant to secretory inhibition by supramaximal CCK-8, and despite a 4.5-fold increase in total cellular trypsinogen levels, are fully protected from intracellular trypsin accumulation and acinar damage. VAMP8-mediated secretion is dependent on expression of the early endosomal proteins Rab5, D52, and EEA1. Supramaximal CCK-8 (60 min) caused a 60% reduction in the expression of D52 followed by Rab5 and EEA1 in isolated acini and in in vivo The loss of D52 occurred as a consequence of its entry into autophagic vacuoles and was blocked by lysosomal cathepsin B and L inhibition. Accordingly, adenoviral overexpression of Rab5 or D52 enhanced secretion in response to supramaximal CCK-8 and prevented accumulation of activated trypsin. These data support that acute inhibition of VAMP8-mediated secretion during pancreatitis triggers intracellular trypsin accumulation and loss of the early endosomal compartment. Maintaining anterograde endosomal trafficking during pancreatitis maintains VAMP8-dependent secretion, thereby preventing accumulation of activated trypsin.

Proteomic screening of glutamatergic mouse brain synaptosomes isolated by fluorescence activated sorting.

For decades, neuroscientists have used enriched preparations of synaptic particles called synaptosomes to study synapse function. However, the interpretation of corresponding data is problematic as synaptosome preparations contain multiple types of synapses and non-synaptic neuronal and glial contaminants. We established a novel Fluorescence Activated Synaptosome Sorting (FASS) method that substantially improves conventional synaptosome enrichment protocols and enables high-resolution biochemical analyses of specific synapse subpopulations. Employing knock-in mice with fluorescent glutamatergic synapses, we show that FASS isolates intact ultrapure synaptosomes composed of a resealed presynaptic terminal and a postsynaptic density as assessed by light and electron microscopy. FASS synaptosomes contain bona fide glutamatergic synapse proteins but are almost devoid of other synapse types and extrasynaptic or glial contaminants. We identified 163 enriched proteins in FASS samples, of which FXYD6 and Tpd52 were validated as new synaptic proteins. FASS purification thus enables high-resolution biochemical analyses of specific synapse subpopulations in health and disease.

The efficacy and safety of continued hydroxycarbamide therapy versus switching to ruxolitinib in patients with polycythaemia vera: a randomized, double-blind, double-dummy, symptom study (RELIEF).

The randomized, double-blind, double-dummy, phase 3b RELIEF trial evaluated polycythaemia vera (PV)-related symptoms in patients who were well controlled with a stable dose of hydroxycarbamide (also termed hydroxyurea) but reported PV-related symptoms. Patients were randomized 1:1 to ruxolitinib 10 mg BID (n = 54) or hydroxycarbamide (prerandomization dose/schedule; n = 56); crossover to ruxolitinib was permitted after Week 16. The primary endpoint, ≥50% improvement from baseline in myeloproliferative neoplasm -symptom assessment form total symptom score cytokine symptom cluster (TSS-C; sum of tiredness, itching, muscle aches, night sweats, and sweats while awake) at Week 16, was achieved by 43·4% vs. 29·6% of ruxolitinib- and hydroxycarbamide-treated patients, respectively (odds ratio, 1·82; 95% confidence interval, 0·82-4·04; P = 0·139). The primary endpoint was achieved by 34% of a subgroup who maintained their hydroxycarbamide dose from baseline to Weeks 13-16. In a post hoc analysis, the primary endpoint was achieved by more patients with stable screening-to-baseline TSS-C scores (ratio ≤ 2) receiving ruxolitinib than hydroxycarbamide (47·4% vs. 25·0%; P = 0·0346). Ruxolitinib treatment after unblinding was associated with continued symptom score improvements. Adverse events were primarily grades 1/2 with no unexpected safety signals. Ruxolitinib was associated with a nonsignificant trend towards improved PV-related symptoms versus hydroxycarbamide, although an unexpectedly large proportion of patients who maintained their hydroxycarbamide dose reported symptom improvement.

TPD52 expression increases neutral lipid storage within cultured cells.

Tumor protein D52 (TPD52) is amplified and/or overexpressed in cancers of diverse cellular origins. Altered cellular metabolism (including lipogenesis) is a hallmark of cancer development, and protein-protein associations between TPD52 and known regulators of lipid storage, and differential TPD52 expression in obese versus non-obese adipose tissue, suggest that TPD52 might regulate cellular lipid metabolism. We found increased lipid droplet numbers in BALB/c 3T3 cell lines stably expressing TPD52, compared with control and TPD52L1-expressing cell lines. TPD52-expressing 3T3 cells showed increased fatty acid storage in triglyceride (from both de novo synthesis and uptake) and formed greater numbers of lipid droplets upon oleic acid supplementation than control cells. TPD52 colocalised with Golgi, but not endoplasmic reticulum (ER), markers and also showed partial colocalisation with lipid droplets coated with ADRP (also known as PLIN2), with a proportion of TPD52 being detected in the lipid droplet fraction. Direct interactions between ADRP and TPD52, but not TPD52L1, were demonstrated using the yeast two-hybrid system, with ADRP-TPD52 interactions confirmed using GST pulldown assays. Our findings uncover a new isoform-specific role for TPD52 in promoting intracellular lipid storage, which might be relevant to TPD52 overexpression in cancer.

An HPLC-UV method for determining plasma dimethylacetamide concentrations in patients receiving intravenous busulfan.

Dimethylacetamide (DMA) is a solvent used in the preparation of intravenous busulfan, an alkylating agent used in blood or marrow transplantation. DMA may contribute to hepatic toxicity, so it is important to monitor its clearance. The aim of this study was to develop an HPLC-UV assay for measurement of DMA in human plasma. After precipitation of plasma proteins with acetonitrile followed by dilution (1:4) with water, the extract was injected onto the HPLC and detected at 195 nm. Separation was performed using a Cogent-HPS 5 µm C18 column (250 × 4.6 mm) preceded by a Brownlee 7 µm RP18 , pre-column (1.5 cm × 3.2 mm). The mobile phase was 25 mm sodium phosphate buffer (pH 3), containing 2.5% (v/v) acetonitrile and 0.0005% (v/v) sodium-octyl-sulfonate. Using a flow rate of 1 mL/min, the retention times of DMA and the internal standard (IS), 2-chloroacetamide, were 9.5 and 3.5 min, respectively. Peak area ratio (DMA:IS) was a linear function of concentration from 1 to 1000 µg/mL. There was excellent intraday precision (<5% for 5-700 µg/mL DMA), accuracy (<3% deviation from the true concentration) and recovery (74-98%). The limits of detection and quantification were 1 and 5 µg/mL, respectively. In eight children who received intravenous busulfan, DMA concentrations ranged from 110 to 438 µg/mL.

Bruton's tyrosine kinase is required for apoptotic cell uptake via regulating the phosphorylation and localization of calreticulin.

In addition to regulating B cell development and activation, Bruton's tyrosine kinase (Btk) functions downstream of multiple TLRs, including TLR7, to regulate innate immune responses in myeloid cells. Although critical for defense against RNA viruses such as influenza and Sendai virus, recognition of self-RNA by TLR7 also has been shown to be an important contributor to the pathophysiology of systemic lupus erythematosus. To date, the role of Btk in regulating TLR7-mediated responses is poorly understood. In the current study, we have demonstrated a hitherto undiscovered role for Btk in apoptotic cell uptake, identifying the molecular chaperone calreticulin (CRT) as a novel substrate for Btk in regulating this response. CRT together with the transmembrane receptor CD91 function at the cell membrane and regulate uptake of C1q-opsonised apoptotic cells. Our results show that Btk directly phosphorylates CRT and that in the absence of Btk, CRT fails to localize with CD91 at the cell surface and at the phagocytic cup. Critically, a blocking Ab against CRT in wild-type macrophages mimics the inability of Btk-deficient macrophages to phagocytose apoptotic cells efficiently, indicating the critical importance of Btk in regulating CRT-driven apoptotic cell uptake. Our data have revealed a novel regulatory role for Btk in mediating apoptotic cell clearance, with CRT identified as the critical component of the CRT/CD91/C1q system targeted by Btk. Given the importance of clearing apoptotic cell debris to prevent inappropriate exposure of TLRs to endogenous ligands, our results have important implications regarding the role of Btk in myeloid cell function.