Cleavage of L1 in exosomes and apoptotic membrane vesicles released from ovarian carcinoma cells.
OBJECTIVE
The L1 adhesion molecule (CD171) is overexpressed in human ovarian and endometrial carcinomas and is associated with bad prognosis. Although expressed as a transmembrane molecule, L1 is released from carcinoma cells in a soluble form. Soluble L1 is present in serum and ascites of ovarian carcinoma patients. We investigated the mode of L1 cleavage and the function of soluble L1.


METHODS
We used ovarian carcinoma cell lines and ascites from ovarian carcinoma patients to analyze soluble L1 and L1 cleavage by Western blot analysis and ELISA.


RESULTS
We find that in ovarian carcinoma cells the constitutive cleavage of L1 proceeds in secretory vesicles. We show that apoptotic stimuli like C2-ceramide, staurosporine, UV irradiation, and hypoxic conditions enhance L1-vesicle release resulting in elevated levels of soluble L1. Constitutive cleavage of L1 is mediated by a disintegrin and metalloproteinase 10, but under apoptotic conditions multiple metalloproteinases are involved. L1 cleavage occurs in two types of vesicles with distinct density features: constitutively released vesicles with similarity to exosomes and apoptotic vesicles. Both types of L1-containing vesicles are present in the ascites fluids of ovarian carcinoma patients. Soluble L1 from ascites is a potent inducer of cell migration and can trigger extracellular signal-regulated kinase phosphorylation.


CONCLUSIONS
We suggest that tumor-derived vesicles may be an important source for soluble L1 that could regulate tumor cell function in an autocrine/paracrine fashion.
Gutwein
Paul
P
Tumor Immunology Programme, D010, German Cancer Research Center, Heidelberg, Germany.
Stoeck
Alexander
A
Riedle
Svenja
S
Gast
Daniela
D
Runz
Steffen
S
Condon
Thomas P
TP
Marmé
Alexander
A
Phong
Minh-Chau
MC
Linderkamp
Otwin
O
Skorokhod
Alexander
A
Altevogt
Peter
P
D051722:ADAM Proteins; D000072198:ADAM17 Protein; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D017209:Apoptosis; D001202:Ascitic Fluid / Q000737:chemistry; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001667:Binding, Competitive; D016466:CHO Cells; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism*; D010450:Endopeptidases; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008666:Metalloendopeptidases / Q000378:metabolism; D039842:Neural Cell Adhesion Molecule L1 / Q000378:metabolism* / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D012995:Solubility; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology
C064769:N-acetylsphingosine; D039842:Neural Cell Adhesion Molecule L1; D048049:Extracellular Signal-Regulated MAP Kinases; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000072198:ADAM17 Protein; D013110:Sphingosine