Structure of natural killer cell receptor KLRG1 bound to E-cadherin reveals basis for MHC-independent missing self recognition.

The cytolytic activity of natural killer (NK) cells is regulated by inhibitory receptors that detect the absence of self molecules on target cells. Structural studies of missing self recognition have focused on NK receptors that bind MHC. However, NK cells also possess inhibitory receptors specific for non-MHC ligands, notably cadherins, which are downregulated in metastatic tumors. We determined the structure of killer cell lectin-like receptor G1 (KLRG1) in complex with E-cadherin. KLRG1 mediates missing self recognition by binding to a highly conserved site on classical cadherins, enabling it to monitor expression of several cadherins (E-, N-, and R-) on target cells. This site overlaps the site responsible for cell-cell adhesion but is distinct from the integrin alpha(E)beta(7) binding site. We propose that E-cadherin may coengage KLRG1 and alpha(E)beta(7) and that KLRG1 overcomes its exceptionally weak affinity for cadherins through multipoint attachment to target cells, resulting in inhibitory signaling.

Short-Term Follow-Up Mammography in Breast Conservation Therapy Likely Leads to Unnecessary Downstream Workup: A Longitudinal Study.

PURPOSE: To analyze the effect of post-radiation therapy (XRT) mammographic timing and radiation technique in relation to additional downstream workup for 569 breast conservation therapy patients treated with adjuvant XRT after their initial surveillance mammogram (MMG). METHODS AND MATERIALS: From January 2011 to December 2014, 569 breast cancer patients treated with breast conservation surgery and adjuvant XRT with a follow-up MMG were reviewed. Patients were stratified by the time interval until their first post-XRT MMG, and by XRT technique-whole breast (472), accelerated partial breast (96), conventional fractionation (373), hypofractionation (94), surgical cavity boosts (407), or no boost (66). The primary endpoint was further imaging after the initial MMG. RESULTS: Additional workup for those receiving an MMG within 3 months of completing XRT was 51% (73 of 143), compared with 40% (84 of 210) with MMG between 3 and 6 months and 34.5% (75 of 216) with MMG after 6 months (P=.04). Radiation boost to the postoperative bed was associated with further downstream imaging, whereas accelerated partial-breast irradiation and hypofractionated treatment were not. CONCLUSIONS: Breast conservation therapy patients who underwent screening MMG before 6 months after completion of XRT were more likely to undergo downstream workup, including additional biopsies. Accelerated and hypofractionated radiation techniques were not associated with supplementary workup. Further study is needed to assess appropriate selection of high-risk patients and possible negative implications of earlier post-XRT screening MMG.

Pancreatic Carcinosarcoma: A Case Report Highlighting Computed Tomography Characteristics.

Primary pancreatic carcinosarcoma is a rare and malignant neoplasm arising within the pancreas. With fewer than a dozen cases ever reported, the recognition and treatment of this rare phenomenon can be difficult. We describe the case of an 85-year-old man who presented with vague right upper quadrant and epigastric abdominal pain and was found to have a pancreatic mass on ultrasound and computed tomography. The patient underwent open pancreaticoduodenectomy and was found to have pancreatic carcinosarcoma on microscopic evaluation. Although specific radiologic diagnosis of this entity is not possible, bringing the possibility of primary pancreatic carcinosarcoma to the ordering clinician׳s attention has the potential to hasten treatment and improve patient outcomes. We review the current literature on this rare type of neoplasia, considering histopathologic and clinical features. This case highlights the importance of radiologist awareness of this rare neoplasm and to consider carcinosarcoma in the differential when presented with a mixed solid and cystic pancreatic mass.

Structural basis for the recognition of mutant self by a tumor-specific, MHC class II-restricted T cell receptor.

Structural studies of complexes of T cell receptor (TCR) and peptide-major histocompatibility complex (MHC) have focused on TCRs specific for foreign antigens or native self. An unexplored category of TCRs includes those specific for self determinants bearing alterations resulting from disease, notably cancer. We determined here the structure of a human melanoma-specific TCR (E8) bound to the MHC molecule HLA-DR1 and an epitope from mutant triosephosphate isomerase. The structure had features intermediate between 'anti-foreign' and autoimmune TCR-peptide-MHC class II complexes that may reflect the hybrid nature of altered self. E8 manifested very low affinity for mutant triosephosphate isomerase-HLA-DR1 despite the highly tumor-reactive properties of E8 cells. A second TCR (G4) had even lower affinity but underwent peptide-specific formation of dimers, suggesting this as a mechanism for enhancing low-affinity TCR-peptide-MHC interactions for T cell activation.