A pleckstrin homology-related domain in SHIP1 mediates membrane localization during Fcγ receptor-induced phagocytosis.

SH2 domain-containing inositol-5'-phosphatase-1 (SHIP1) inhibits inflammation by hydrolyzing phosphoinositide-3'-kinase generated membrane phosphatidylinositol-3,4,5-trisphosphate (PIP(3)). Bioinformatic analysis of SHIP1 from multiple species revealed a pleckstrin homololgy-related (PH-R) domain, which we hypothesize mediates SHIP1's association with the membrane, a requirement for its biological function. Recombinant murine SHIP1 PH-R domain was subjected to biophysical and biochemical analysis. Residues K370 and K397 were found to be important for PH-R domain association with membrane PIP(3). Wild-type PH-R domain bound PIP(3) with 1.9 ± 0.2 nM affinity, while the affinity of a K370A/K397A substituted mutant was too low to measure. Wild-type (but not the K370A/K397A substituted) full-length SHIP1 protein, reconstitutes normal inhibition of Fcγ receptor-mediated phagocytosis when introduced into SHIP1(-/-) murine macrophages, reducing the number of phagocytic events by 2-fold as compared to SHIP1(-/-) cells. In fact, the PH-R-mediated membrane interaction appears to be a major mechanism by which SHIP1 is recruited to the membrane, since the K370A/K397A substitution reduced the recruitment of both full-length SHIP1 and the PH-R domain by ≥2-fold. We have previously shown that SHIP1 enzyme activity can be targeted for therapeutic purposes. The current studies suggest that molecules targeting the PH-R domain can also modulate SHIP1 function.

Positive identification of CA215 pan cancer biomarker from serum specimens of cancer patients.

BACKGROUND: To evaluate the clinical utility of CA215 as a pan cancer biomarker, serum levels of CA215 were determined with clinically defined serum specimens from over 500 cancer patients and compared with results obtained by other nine established cancer markers. The molecular nature of this cancer-associated antigen from selected patients' sera was determined. METHODS: By using improved immunoassays, serum levels of CA215 and other known biomarkers were determined for respective positive detection rates. The molecular size of CA215 from cancer patients was determined by Western blot assay. RESULTS: By using 0.1 AU/ml as the normal cut-off value, the positive rates of CA215 for different cancers were shown to be 52% (lung), 74% (liver), 44% (colon), 61% (esophagus), 60% (stomach), 59% (ovary), 40% (prostate), 71% (breast), 38% (kidney), 41% (pancreas), 51% (cervix), and 83% (lymphoma), respectively. Other cancer markers including AFP, CEA, CA125, CA19-9, CA15-3, Cyfra21-1, Ferritin, beta(2) microglobulin and PSA were also parallelly compared. A combination of CA215 with other tissue-associated cancer markers generally resulted in much higher cancer detection rates. CA215 detected from cancer patients was confirmed to be human immunoglobulins that contain common RP215-specific carbohydrate-associated epitope. CONCLUSION: Through clinical evaluations of serum specimens of various cancer patients, CA215 was confirmed to be human cancer cell-derived immunoglobulins. CA215 is apparently comparable to or better than other known biomarkers for the positive detection and monitoring of many types of human cancers.