LtpD is a novel legionella pneumophila effector that binds phosphatidylinositol 3-phosphate and inositol monophosphatase IMPA1

The Dot/Icm type IV secretion system (T4SS) of Legionella pneumophila is crucial for the pathogen to survive in protozoa and cause human disease. Although more than 275 effector proteins are delivered into the host cell by the T4SS, the function of the majority is unknown. Here we have characterized the Dot/Icm effector LtpD. During infection, LtpD localized to the cytoplasmic face of the membrane of the Legionella-containing vacuole (LCV). In A549 lung epithelial cells, ectopically expressed LtpD localized to large vesicular structures that contained markers of endosomal compartments. Systematic analysis of LtpD fragments identified an internal 17-kDa fragment, LtpD_471-626, which was essential for targeting ectopically expressed LtpD to vesicular structures and for the association of translocated LtpD with the LCV. LtpD_471-626 bound directly to phosphatidylinositol 3-phosphate [PtdIns(3)P] in vitro and colocalized with the PtdIns(3)P markers FYVE and SetA in cotransfected cells. LtpD was also found to bind the host cell enzyme inositol (myo)-1 (or 4)-monophosphatase 1, an important phosphatase involved in phosphoinositide production. Analysis of the role of LtpD in infection showed that LtpD is involved in bacterial replication in THP-1 macrophages, the larvae of Galleria mellonella, and mouse lungs. Together, these data suggest that LtpD is a novel phosphoinositide- binding L. pneumophila effector that has a role in intracellular bacterial replication. © 2013, American Society for Microbiology.

Biomarker analysis in oesophagogastric cancer: Results from the REAL3 and TransMAGIC trials.

BACKGROUND: REAL3 (Randomised ECF for Advanced or Locally advanced oesophagogastric cancer 3) was a phase II/III trial designed to evaluate the addition of panitumumab (P) to epirubicin, oxaliplatin and capecitabine (EOC) in untreated advanced oesophagogastric adenocarcinoma, or undifferentiated carcinoma. MAGIC (MRC Adjuvant Gastric Infusional Chemotherapy) was a phase III study which demonstrated that peri-operative epirubicin, cisplatin and infused 5-fluorouracil (ECF) improved survival in early oesophagogastric adenocarcinoma. PATIENTS AND METHODS: Analysis of response rate (RR; the primary end-point of phase II) and biomarkers in the first 200 patients randomised to EOC or modified dose (m) EOC+P in REAL3 was pre-planned to determine if molecular selection for the on-going study was indicated. KRAS, BRAF and PIK3CA mutations and PTEN expression were assessed in pre-treatment biopsies and results correlated with response to mEOC+P. Association between these biomarkers and overall survival (OS) was assessed in MAGIC patients to determine any prognostic effect. RESULTS: RR was 52% to mEOC+P, 48% to EOC. Results from 175 assessable biopsies: mutations in KRAS (5.7%), BRAF (0%), PIK3CA (2.5%) and loss of PTEN expression (15.0%). None of the biomarkers evaluated predicted resistance to mEOC+P. In MAGIC, mutations in KRAS, BRAF and PIK3CA and loss of PTEN (phosphatase and tensin homolog) were found in 6.3%, 1.0%, 5.0% and 10.9%, respectively, and were not associated with survival. CONCLUSIONS: The RR of 52% in REAL3 with mEOC+P met pre-defined criteria to continue accrual to phase III. The frequency of the mutations was too low to exclude any prognostic or predictive effect.