Calcium-independent phospholipase A 2 (iPLA 2 ) plays a pivotal role in phospholipid remodeling and many other biological processes, including inflammation and cancer development. iPLA 2 can be activated by caspase-3 via a proteolytic process in apoptotic cells. In this study we identify novel signaling and functional loops of iPLA 2 activation leading to migration of non-apoptotic human ovarian cancer cells. The extracellular matrix protein, laminin-10/11, but not collagen I, induces integrin-and caspase-3-dependent cleavage and activation of overexpressed and endogenous iPLA 2 . The truncated iPLA 2 (amino acids 514 -806) generates lysophosphatidic acid and arachidonic acid. Arachidonic acid is important for enhancing cell migration toward laminin-10/11. Lysophosphatidic acid activates Akt that in turn acts in a feedback loop to block the cleavage of poly-(ADP-ribose) polymerase and DNA fragmentation factor as well as prevent apoptosis. By using pharmacological inhibitors, blocking antibodies, and genetic approaches (such as point mutations, dominant negative forms of genes, and siRNAs against specific targets), we show that ␤ 1 , but not ␤ 4 , integrin is involved in iPLA 2 activation and cell migration to laminin-10/ 11. The role of caspase-3 in iPLA 2 activation and cell migration are supported by several lines of evidence. 1) Point mutation of Asp 513 (a cleavage site of caspase-3 in iPLA 2 ) to Ala blocks laminin-10/11-induced cleavage and activation of overexpressed iPLA 2 , whereas mutation of Asp 733 to Ala has no such effect, 2) treatment of inhibitors or a small interfering RNA against caspase-3 results in decreased cell migration toward laminin-10/11, and 3) selective caspase-3 inhibitor blocks cleavage of endogenous iPLA 2 induced by laminin-10/11. Importantly, small interfering RNA-mediated down-regulation of endogenous iPLA 2 expression in ovarian carcinoma HEY cells results in decreased migration toward laminin, suggesting that our findings are pathophysiologically important.

One mechanism by which oncoproteins work is through perturbation of cellular maturation; understanding the mechanisms by which this occurs can lead to the development of targeted therapies. EVI1 is a zinc finger oncoprotein involved in the development of acute myeloid leukemia; previous work has shown it to interfere with the maturation of granulocytes from immature precursors. Here we investigate the mechanism by which that occurs, using an immortalized hematopoietic progenitor cell line, EML-C1, as a model system. We document that overexpression of EVI1 abrogates retinoic acid-induced maturation of EML cells into committed myeloid cells, a process that can be documented by the down-regulation of stem cell antigen-1 and acquisition of responsiveness to granulocyte-macrophage colony-stimulating factor. We show that this requires DNA binding capacity of EVI1, suggesting that downstream target genes are involved. We identify the myeloid regulator Cebpa as a target gene and identify two EVI1 binding regions within evolutionarily conserved enhancer elements at ؉35 and ؉37 kb relative to the gene. EVI1 can strongly suppress Cebpa transcription, and add-back of Cebpa into EVI1-expressing EML cells partially corrects the block in maturation. We identify the DNA sequences to which EVI1 binds at ؉35 and ؉37 kb and show that mutation of one of these releases Cebpa from EVI1-induced suppression. We observe a more complex picture in primary bone marrow cells, where EVI1 suppresses Cebpa in stem cells but not in more committed progenitors. Our data thus identify a regulatory node by which EVI1 contributes to leukemia, and this represents a possible therapeutic target for treatment of EVI1-expressing leukemia.

After completing this course, the reader will be able to:1. Cite the primary concerns of oncologists regarding influenza vaccination for their cancer patients.2. Describe research showing that cancer patients, whether taking myelosuppressive chemotherapy or not, are able to generate an immune response to the H1N1 vaccine similar to that of healthy controls.This article is available for continuing medical education credit at CME.TheOncologist.com. CME CME ABSTRACTBackground. The immune response of patients who have cancer, who may be receiving immunosuppressive therapy, is generally considered to be decreased. This study

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