Phagocytosis is initiated by lateral clustering of receptors, which in turn activates Src-family kinases (SFKs). Activation of SFKs requires depletion of tyrosine phosphatases from the area of ...particle engagement. We investigated how the major phosphatase CD45 is excluded from contact sites, using single-molecule tracking. The mobility of CD45 increased markedly upon engagement of Fcγ receptors. While individual CD45 molecules moved randomly, they were displaced from the advancing phagocytic cup by an expanding diffusional barrier. By micropatterning IgG, the ligand of Fcγ receptors, we found that the barrier extended well beyond the perimeter of the receptor-ligand engagement zone. Second messengers generated by Fcγ receptors activated integrins, which formed an actin-tethered diffusion barrier that excluded CD45. The expanding integrin wave facilitates the zippering of Fcγ receptors onto the target and integrates the information from sparse receptor-ligand complexes, coordinating the progression and ultimate closure of the phagocytic cup.
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•Tyrosine phosphatases are excluded from sites of phagocytosis•An expanding diffusion barrier prevents phosphatase access to sites of phagocytosis•Integrins activated by phagocytic receptors generate the diffusion barrier•Activated integrins bridge sparse phagocytic receptors and coordinate phagocytosis
To create the large zone of Src-family kinase (SFK) phosphorylation required for phagocytosis, a cascade of integrin activation, emanating from antigen contact sites, generates an expanding actin-based diffusion barrier that restricts the access of the bulky phosphatase molecules that target SFK.
Phagocytic receptors must diffuse laterally to become activated upon clustering by multivalent targets. Receptor diffusion, however, can be obstructed by transmembrane proteins (“pickets”) that are ...immobilized by interacting with the cortical cytoskeleton. The molecular identity of these pickets and their role in phagocytosis have not been defined. We used single-molecule tracking to study the interaction between Fcγ receptors and CD44, an abundant transmembrane protein capable of indirect association with F-actin, hence likely to serve as a picket. CD44 tethers reversibly to formin-induced actin filaments, curtailing receptor diffusion. Such linear filaments predominate in the trailing end of polarized macrophages, where receptor mobility was minimal. Conversely, receptors were most mobile at the leading edge, where Arp2/3-driven actin branching predominates. CD44 binds hyaluronan, anchoring a pericellular coat that also limits receptor displacement and obstructs access to phagocytic targets. Force must be applied to traverse the pericellular barrier, enabling receptors to engage their targets.
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•CD44 functions as a picket, affixing the cortical actin cytoskeleton to the membrane•The extracellular domain of CD44 binds hyaluronan, which forms a pericellular coat•The picket fence and pericellular coat limit the mobility of phagocytic receptors•Remodeling of the actin fence enables receptors to cluster and initiate phagocytosis
The actin cytoskeleton is affixed to the plasma membrane by a cell-surface protein bound to a pericellular coat, forming a barrier that limits receptor mobility.
Hijal et al comment on Tsang and Patel's article "Proton beam therapy for cancer." Currently, no proton beam facility exists in Canada, and patients deemed eligible receive this therapy at proton ...centers in the US at a cost often exceeding $250,000 per patient, paid for by provincial health plans. In Quebec, there is a well-established process for referral for treatment with proton therapy in the US, but the number of children and young adults who currently benefit from this treatment is lower than expected. They argue that developing proton therapy as a stand-alone private initiative is wrong for several reasons. Perhaps most importantly, receiving treatment at a private facility could introduce major risks for the patients. Most children younger than 5-7 years will need to undergo treatments under anesthesia. A serious complication occurring away from the support of a pediatric care facility could be devastating. As well, since radiation therapy is part of a multidisciplinary cancer treatment strategy that, in pediatric practice, almost always combines surgery and chemotherapy and requires intensive supportive care, it is highly preferable that proton therapy be geographically embedded in a multidisciplinary environment that can provide this type of complete care.
Macrophages continuously survey their environment in search of pathogens or apoptotic corpses or debris. Targets intended for clearance expose ligands that initiate their phagocytosis (“eat me” ...signals), while others avoid phagocytosis by displaying inhibitory ligands (“don’t eat me” signals). We report that such ligands can be obscured by the glycosaminoglycans and glycoproteins that coat pathogenic as well as malignant phagocytic targets. In addition, a reciprocal barrier of self-synthesized or acquired glycocalyx components on the macrophage surface shrouds phagocytic receptors, curtailing their ability to engage particles. The coating layers of macrophages and their targets hinder phagocytosis by both steric and electrostatic means. Their removal by enzymatic means is shown to markedly enhance phagocytic efficiency. In particular, we show that the removal of mucins, which are overexpressed in cancer cells, facilitates their clearance. These results shed light on the physical barriers that modulate phagocytosis, which have been heretofore underappreciated.
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•Large hyaluronans in synovial fluid obstruct particle binding by macrophages•The glycocalyx contributes to negative surface potential of macrophages•Macrophages selectively bind targets according to their charge•Bulky transmembrane mucins of tumors override antibody blockade of CD47-SIRPα
Imbert et al. report that ligands that stimulate phagocytosis can be obscured by the glycocalyx of pathogenic and malignant targets. A reciprocal barrier conceals phagocytic receptors. Removal of these barriers enhances phagocytic efficiency and facilitates target clearance. The results shed light on physical barriers that modulate phagocytosis.
•Our investigation focused on the neutrophil-to-lymphocyte ratio (NLR) as a prognostic biomarker in response to radiotherapy.•Our observations revealed a significant association between a post-RT ...NLR > 4 and a higher incidence of recurrence and distant metastasis.•NLR in soft tissue sarcomas did not impact overall survival.•This is the first study focusing on the influence of NLR measured at the time of curative treatment involving surgery and RT.•The results presented in our manuscript underscore the necessity of gaining a deeper understanding of the immunobiological effects of radiation therapy.
This study aims to assess the prognostic value of the neutrophil-to-lymphocyte ratio (NLR) in soft tissue sarcomas (STS) treated with pre-operative hypofractionated radiotherapy (HFRT).
This retrospective analysis included patients treated with pre-operative HFRT of 30 Gy in 5 fractions between 2016 and 2023. Clinical, demographic, and complete blood count (CBC) data were collected. NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. Only patients with CBCs conducted within 6 months after radiotherapy were included. Cox proportional-hazard regression models were used to assess the impact of NLR and different variables on outcomes. Kaplan Meier were used to illustrate survival curves. A p-value < 0.05 was considered significant, and 95 % confidence intervals (CI) were employed.
A total of 40 patients received HFRT and had CBCs within 6 months after radiotherapy. There were 17 (42.5 %) females and 23 (57.5 %) males with a mean age of 66 years. The mean largest tumor size dimension was 7.1 cm, and the mean NLR post-RT was 5.3. The most frequent histological subtypes were myxofibrosarcoma (17.5 %), pleomorphic spindle cell sarcoma (10 %), leiomyosarcoma (7.5 %), and myxoid liposarcoma (5 %). The median follow-up period was 15.4 months. From all patients, 14 patients had disease progression, 12 metastatic disease and 3 died of disease. Multivariable Cox proportional-hazards regression analysis displayed that a higher post-RT NLR was associated with worse disease-free survival (DFS) (HR: 1.303 1.098–1.548, p = 0.003), and distant metastasis-free survival (DMFS) (HR: 1.38 1.115–1.710, p = 0.003). Moreover, post-NLR ≥ 4 as a single variable was associated with worse DFS, DMFS, but not worse local recurrence or overall survival.
This study is the first to evaluate NLR as a prognostic biomarker in STS patients treated with pre-operative radiotherapy. A higher NLR after pre-operative radiotherapy was associated with increased disease progression.
We performed a multi-institutional prospective phase II trial to assess late toxicities in patients with extremity soft tissue sarcoma (STS) treated with preoperative image-guided radiation therapy ...(IGRT) to a reduced target volume.
Patients with extremity STS received IGRT with (cohort A) or without (cohort B) chemotherapy followed by limb-sparing resection. Daily pretreatment images were coregistered with digitally reconstructed radiographs so that the patient position could be adjusted before each treatment. All patients received IGRT to reduced tumor volumes according to strict protocol guidelines. Late toxicities were assessed at 2 years.
In all, 98 patients were accrued (cohort A, 12; cohort B, 86). Cohort A was closed prematurely because of poor accrual and is not reported. Seventy-nine eligible patients from cohort B form the basis of this report. At a median follow-up of 3.6 years, five patients did not have surgery because of disease progression. There were five local treatment failures, all of which were in field. Of the 57 patients assessed for late toxicities at 2 years, 10.5% experienced at least one grade ≥ 2 toxicity as compared with 37% of patients in the National Cancer Institute of Canada SR2 (CAN-NCIC-SR2: Phase III Randomized Study of Pre- vs Postoperative Radiotherapy in Curable Extremity Soft Tissue Sarcoma) trial receiving preoperative radiation therapy without IGRT (P < .001).
The significant reduction of late toxicities in patients with extremity STS who were treated with preoperative IGRT and absence of marginal-field recurrences suggest that the target volumes used in the Radiation Therapy Oncology Group RTOG-0630 (A Phase II Trial of Image-Guided Preoperative Radiotherapy for Primary Soft Tissue Sarcomas of the Extremity) study are appropriate for preoperative IGRT for extremity STS.
The purpose of this work is to propose a method to characterize tumour heterogeneity on MRI, using probabilistic classification based on a reference tissue. The method uses maps of the apparent ...diffusion coefficient (ADC), T2 relaxation, and a calculated map representing high‐b‐value diffusion‐weighted MRI (denoted simDWI) to identify up to five habitats (i.e. sub‐regions) of tumours.
In this classification method, the parameter values (ADC, T2, and simDWI) from each tumour voxel are compared against the corresponding parameter probability distributions in a reference tissue. The probability that a tumour voxel belongs to a specific habitat is the joint probability for all parameters. The classification can be visualized using a custom colour scheme.
The proposed method was applied to data from seven patients with biopsy‐confirmed soft tissue sarcoma, at three time‐points over the course of pre‐operative radiotherapy. Fast‐spin‐echo images with two different echo times and diffusion MRI with three b‐values were obtained and used as inputs to the method. Imaging findings were compared with pathology reports from pre‐radiotherapy biopsy and post‐surgical resection.
Regions of hypercellularity, high‐T2 proteinaceous fluid, necrosis, collagenous stroma, and fibrosis were identified within soft tissue sarcoma. The classifications were qualitatively consistent with pathological observations. The percentage of necrosis on imaging correlated strongly with necrosis estimated from FDG‐PET before radiotherapy (R2 = 0.97) and after radiotherapy (R2 = 0.96).
The probabilistic classification method identifies realistic habitats and reflects the complex microenvironment of tumours, as demonstrated in soft tissue sarcoma.
A reference‐tissue‐based probabilistic classification method is proposed to characterize intra‐tumoural heterogeneity on MRI. This method uses maps of ADC and T2, and a calculated map representing high‐b‐value diffusion‐weighted MRI. A soft tissue sarcoma dataset was classified into five intra‐tumoural habitats: hypercellular tumour, high‐T2 proteinaceous fluid, necrosis, collagenous stroma, and fibrosis. The classifications were qualitatively consistent with pathological observations. The percentage of identified necrosis correlated strongly with low‐uptake regions on FDG‐PET, before radiotherapy (R2 = 0.97) and after radiotherapy (R2 = 0.96).
The Children's Oncology Group Long-Term Follow-Up Guidelines for Survivors of Childhood, Adolescent, and Young Adult Cancers are risk-based, exposure-related clinical practice guidelines intended to ...promote earlier detection of and intervention for complications that may potentially arise as a result of treatment for pediatric malignancies. Developed through the collaborative efforts of the Children's Oncology Group Late Effects Committee, Nursing Discipline, and Patient Advocacy Committee, these guidelines represent a statement of consensus from a multidisciplinary panel of experts in the late effects of pediatric cancer treatment. The guidelines are both evidence-based (utilizing established associations between therapeutic exposures and late effects to identify high-risk categories) and grounded in the collective clinical experience of experts (matching the magnitude of risk with the intensity of screening recommendations). They are intended for use beginning 2 or more years following the completion of cancer therapy; however, they are not intended to provide guidance for follow-up of the survivor's primary disease. A complementary set of patient education materials ("Health Links") was developed to enhance follow-up care and broaden the application of the guidelines. The information provided in these guidelines is important for health care providers in the fields of pediatrics, oncology, internal medicine, family practice, and gynecology, as well as subspecialists in many fields. Implementation of these guidelines is intended to increase awareness of potential late effects and to standardize and enhance follow-up care provided to survivors of pediatric cancer throughout the lifespan. The Guidelines, and related Health Links, can be downloaded in their entirety at www.survivorshipguidelines.org.
To report the results of an analysis of dose received to tissues and organs outside the target volume, in the setting of spinal axis irradiation for the treatment of medulloblastoma, using three ...treatment techniques.
Treatment plans (total dose, 23.4 Gy) for a standard two-dimensional (2D) technique, a three-dimensional (3D) technique using a 3D imaging-based target volume, and an intensity-modulated radiotherapy (IMRT) technique, were compared for 3 patients in terms of dose-volume statistics for target coverage, as well as organ at risk (OAR) and overall tissue sparing.
Planning target volume coverage and dose homogeneity was superior for the IMRT plans for V(95%) (IMRT, 100%; 3D, 96%; 2D, 98%) and V(107%) (IMRT, 3%; 3D, 38%; 2D, 37%). In terms of OAR sparing, the IMRT plan was better for all organs and whole-body contour when comparing V(10Gy), V(15Gy), and V(20Gy). The 3D plan was superior for V(5Gy) and below. For the heart and liver in particular, the IMRT plans provided considerable sparing in terms of V(10Gy) and above. In terms of the integral dose, the IMRT plans were superior for liver (IMRT, 21.9 J; 3D, 28.6 J; 2D, 38.6 J) and heart (IMRT, 9 J; 3D, 14.1J; 2D, 19.4 J), the 3D plan for the body contour (IMRT, 349 J; 3D, 337 J; 2D, 555 J).
Intensity-modulated radiotherapy is a valid treatment option for spinal axis irradiation. We have shown that IMRT results in sparing of organs at risk without a significant increase in integral dose.
Craniospinal irradiation (CSI) is a complex radiation therapy technique that is used for patients, often children and teenagers/young adults, with tumors that have a propensity to spread throughout ...the central nervous system such as medulloblastoma. CSI is associated with important long‐term side effects, the risk of which may be affected by numerous factors including radiation modality and technique. Lack of standardization for a technique that is used even in larger radiation oncology departments only a few times each year may be one such factor and the current ad hoc manner of planning new CSI patients may be greatly improved by implementing a dose–volume histogram registry (DVHR) to use previous patient data to facilitate prospective constraint guidance for organs at risk. In this work, we implemented a DVHR and used it to provide standardized constraints for CSI planning. Mann–Whitney U tests and mean differences at 95% confidence intervals were used to compare two cohorts (pre‐ and post‐DVHR intervention) at specific dosimetric points to determine if observed improvements in standardization were statistically significant. Through this approach, we have shown that the implementation of dosimetric constraints based on DVHR‐derived data helped improve the standardization of pediatric CSI planning at our center. The DVHR also provided guidance for a change in CSI technique, helping to achieve practice standardization across TomoTherapy and IMRT.
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