new report: Functional Role and Prognostic Significance of CD157 in Ovarian Carcinoma

lindaprocopio

This research results is particularly hard to understand, but for those of you who have or want to have tissue assays, especially those with serous ovarian, it may be useful. (Please post if you can interpret this in layman's terms; this is a HARD one to understand):

Functional Role and Prognostic Significance of CD157 in Ovarian Carcinoma
J Natl Cancer Inst. 2010 Aug 4;102(15):1160-1177, E Ortolan, R Arisio, S Morone, P Bovino, N Lo-Buono, G Nacci, R Parrotta, D Katsaros, I Rapa, G Migliaretti, E Ferrero, M Volante, A Funaro


TAKE-HOME MESSAGE
CD157 mediates the invasive potential of serous ovarian cancer cells, and its expression is associated with disease-free survival and overall survival in patients with ovarian cancer.

STUDY IN CONTEXT
CD157 is expressed by mesothelial cells and mediates leukocyte adhesion and migration. Recent evidence shows that CD157 genes are differentially expressed in epithelial ovarian cancer cells vs normal ovarian cells. This study evaluated several aspects of CD157 expression and behavior that supported the hypothesis that CD157 is involved in interactions between the mesothelium and ovarian tumor cells that might control ovarian cancer invasion and metastasis. CD157 may thus be a useful diagnostic marker or therapeutic target.

CD157 expression and behavior were evaluated in 9 ovarian cancer cell lines and in ovarian cancer cells obtained from tumor biopsies and neoplastic ascites. In addition, 3 primary human peritoneal mesothelial cell (HPMC) cultures that were free of tumor cells were used. Assays included flow cytometry, reverse transcription–polymerase chain reaction (RT-PCR) analysis, immunoprecipitation and Western blot analysis, confocal and phase contrast microscopy, invasion assay, adhesion assay, wound assay, and assays involving spheroids formed of ovarian tumor culture cells. Pathologic and clinical data were obtained from patients treated for ovarian cancer, and immunohistochemistry analysis was carried out using tissue sections of epithelial ovarian cancer tumors.

CD157 was expressed by cancer cells from patients with serous ovarian cancer, but not by cells from nonserous ovarian cancer. There were also differences in the level of expression of CD157 in the various ovarian cancer cell lines. All nonmalignant HPMCs expressed CD157. In HPMC monolayers, CD157 expression was mainly found in the intercellular junctions and on the basal surfaces. Although almost all of the cells in patients’ primary tumors expressed CD157, only approximately 10% of fresh tumor cells in the same patients’ ascites expressed CD157. However, approximately 80% of these ascites cells expressed CD157 after 2 to 3 days in culture.

CD157 was not expressed on the surface of floating spheroids, but expression increased by seven-fold when the spheroids were in culture for 24 hours. Cells that were separated from spheroids attached to culture plates and began expressing CD157, which was mainly localized at the intercellular junctions.

Anti-CD157 treatment reduced the ability of CD157-positive tumor cells to migrate through artificial tissue membranes. Transfection of CD157 into a poorly invasive, CD157-negative cell line doubled the rate of migration of the transfected cells. Anti-CD157 treatment interfered with the ability of CD157-positive spheroids to invade an HPMC monolayer, even though anti-CD157 did not appear to prevent initial spheroid adhesion to the HPMCs.Anti-CD157 also reduced the ability of spheroids to spread on surfaces coated with extracellular membrane components.

CD157 was expressed in 93% of tumor samples from patients with a variety of ovarian cancer types. These types included serous papillary (51 cases), endometrioid (12 cases), undifferentiated (12 cases), clear cell (9 cases), and mucinous (4 cases). Expression was localized at the intercellular boundaries and on the basolateral surface of the epithelial cells. CD157 expression was significantly associated with patient outcomes. Higher levels of CD157 expression (histologic [H] score ≥60) were associated with significantly shorter disease-free survival (DFS) than were lower levels of CD157 expression (H <60) (median DFS, 30 months vs unreached; P = .004). There was a similar trend in overall survival (OS) (P = .059). In serous tumors, which are the most aggressive type of ovarian cancer histotype, CD157 expression was significantly associated with survival (DFS, 18 months vs unreached; P = .005; OS, 45 months vs unreached; P = .024). This effect was not observed in nonserous tumors. On multivariate analysis, CD157 was an independent prognostic factor for DFS, tumor relapse, and OS.

This study provides evidence that CD157 is involved in interactions among ovarian cancer cells, extracellular membrane proteins, and mesothelial cells. These interactions control tumor cell migration and invasion. CD157 expression was associated with reduced DFS and OS. CD157 thus appears to be a potential diagnostic target for ovarian cancer as well as a potential therapeutic target to prevent tumor dissemination in patients with serous ovarian cancer.

bea-mil

CD157 in Ovarian Carcinoma: How Does It Help Us?
"CD157 is the second member of a family of nicotinamide adenine dinucleotidases that also includes CD38. These cell surface markers are ectoenzymes that cleave extracellular nicotinamide adenine dinucleotide to produce ADP-ribose and cyclic ADP-ribose at the cell surface. They also act as receptors for CD31 (aka "platelet–endothelial cell adhesion molecule-1") expressed on endothelial cells. The signaling regulated by CD38 and CD157 may serve to regulate calcium homeostasis, as well as to modulate the function of poly-ADP ribosyl transferases involved in cell signaling, DNA repair, and apoptosis.

In this issue of the Journal (1), Ortolan et al. present an intriguing story involving CD157 that suggests a role for this protein in the progression and aggressiveness of ovarian tumors. CD157 was detected in half of human primary ovarian cancers. Expression of CD157 was higher in primary tumors than in nonadherent ascites cells and was associated with more aggressive ovarian cancer, as reflected by decreased overall patient survival. Exogenous expression of CD157 in an ovarian cancer cell line increased cell migration in a scratch assay in vitro. Conversely, inhibiting CD157 function with an antagonist antibody decreased migration, invasion, and adhesion of primary cultured ovarian cancer cells and ovarian cancer cell lines. These findings were consistent with the known ability of CD157 to interact with CD31 on endothelial and stromal cells.

What is the potential clinical utility of this observation? CD157 is anchored to the plasma membrane by glycophosphatidylinositol and can be shed into serum. In rheumatoid arthritis, high serum CD157 is associated with more severe joint destruction (2). Therefore, levels of CD157 could be potentially measured in the serum of ovarian cancer patients, as well as in the tumors themselves. CD157 is unlikely to be sensitive or specific enough as a biomarker for diagnosis of ovarian cancer but could confer increased invasive capacity to some ovarian cancers and therefore could indicate a particular line of therapy. CD157 was detected in ovarian cancers of each histology and may impart its function independent of histological classification.

Could CD157 be prognostic of outcome in ovarian cancer? In multiple myeloma and chronic lymphocytic leukemia, high expression of the related molecule CD38 on tumor cells indicates a worse prognosis (3). CD157 expression appears to be associated with poor outcome in ovarian cancer because tumors that expressed high levels of CD157 as assessed by histological scoring gave worse overall survival in comparison with those with lower levels of CD157 in this study. The effect was more profound in the tumors of serous histology. However, given the myriad of prognostic markers for this disease (CA-125, gene signatures, and cyclin E to name a few), it is not clear whether another one will greatly assist the field or the management of these patients.

It may be more valuable to look closely at the biology. It is interesting to speculate how the function of CD157 might contribute to a more aggressive ovarian cancer or to the generation of a chemoresistant phenotype. CD157 binds to its ligand, CD31, that is expressed on endothelial cells, thereby anchoring the cancer cell and possibly activating signaling in either cell type. CD157 does not have a transmembrane domain, but it interacts with other key cell surface molecules to increase their signaling (2). For example, CD31-mediated ligation of CD157 induces colocalization and tyrosine phosphorylation of focal adhesion kinase (2), which potentially triggers intracellular signal transduction downstream of src-family kinases. Similarly, binding of the family member CD38 to CD31 triggers phosphorylation of c-abl and extracellular signal-regulated kinase/mitogen-associated protein kinase (4). The focal adhesion kinase–mitogen-associated protein kinase signaling cascade could mediate increased cellular migration.

Could CD157 provide a target for therapeutic intervention? A monoclonal antibody that blocks CD157 binding to CD31 or similar counterreceptors might prevent invasion of malignant ovarian epithelial cells, but it is not likely to affect ovarian cancer cells that are in the ascites because CD157 was not expressed by the nonadherent ascites cells in the current study. If CD157 promotes invasion in the metastatic ovarian cancer cells, but is not expressed when the cells are dispersed in the ascites, it is unclear whether CD157 must be reexpressed to promote heterotypic cellular adhesion or whether the reexpression of CD157 on adherent cells is triggered by the microenvironment after the ovarian cancer cells have metastasized. Each of these possibilities in the timing of CD157 expression in the process of ovarian cancer dissemination would have different implications for the development of CD157 as a potential therapeutic target. It also remains to be explored whether the interaction between CD157 and CD31 activates the endothelial cell through CD31, and whether this triggers angiogenesis. This activity would provide solid support for CD157 as a therapeutic target.

The enzymatic activity of CD157 may be as important as its role as a receptor. When CD157 cleaves nicotinamide adenine dinucleotide to generate ADP-ribose and cyclic ADP-ribose (5), the reaction generates substrate for ADP-ribosyl transferases and polymerases. ADP-ribosylation of cell surface proteins may modulate their function and promote aggressiveness in ovarian cancer. This potential outcome of CD157 activity warrants further examination, given the recent development of poly-ADP-ribose polymerase inhibitors in the clinic. Specifically, which proteins become ADP-ribosylated at the cell surface? How is this affected by CD157 activity? How might this affect the CD31-expressing cells?

As with most interesting biomarker studies, this one generates more questions than answers. To be clinically important, these results need additional validation and better understanding from a biological and biochemical standpoint. Once these stromal–epithelial interactions are mapped out, it is likely that novel therapeutic approaches will evolve leading to more effective treatment of women with ovarian cancer."

http://jnci.oxfordjournals.org/cgi/content/full/djq269

gdpawel

bea-mil said:

CD157 in Ovarian Carcinoma: How Does It Help Us?
"CD157 is the second member of a family of nicotinamide adenine dinucleotidases that also includes CD38. These cell surface markers are ectoenzymes that cleave extracellular nicotinamide adenine dinucleotide to produce ADP-ribose and cyclic ADP-ribose at the cell surface. They also act as receptors for CD31 (aka "platelet–endothelial cell adhesion molecule-1") expressed on endothelial cells. The signaling regulated by CD38 and CD157 may serve to regulate calcium homeostasis, as well as to modulate the function of poly-ADP ribosyl transferases involved in cell signaling, DNA repair, and apoptosis.

In this issue of the Journal (1), Ortolan et al. present an intriguing story involving CD157 that suggests a role for this protein in the progression and aggressiveness of ovarian tumors. CD157 was detected in half of human primary ovarian cancers. Expression of CD157 was higher in primary tumors than in nonadherent ascites cells and was associated with more aggressive ovarian cancer, as reflected by decreased overall patient survival. Exogenous expression of CD157 in an ovarian cancer cell line increased cell migration in a scratch assay in vitro. Conversely, inhibiting CD157 function with an antagonist antibody decreased migration, invasion, and adhesion of primary cultured ovarian cancer cells and ovarian cancer cell lines. These findings were consistent with the known ability of CD157 to interact with CD31 on endothelial and stromal cells.

What is the potential clinical utility of this observation? CD157 is anchored to the plasma membrane by glycophosphatidylinositol and can be shed into serum. In rheumatoid arthritis, high serum CD157 is associated with more severe joint destruction (2). Therefore, levels of CD157 could be potentially measured in the serum of ovarian cancer patients, as well as in the tumors themselves. CD157 is unlikely to be sensitive or specific enough as a biomarker for diagnosis of ovarian cancer but could confer increased invasive capacity to some ovarian cancers and therefore could indicate a particular line of therapy. CD157 was detected in ovarian cancers of each histology and may impart its function independent of histological classification.

Could CD157 be prognostic of outcome in ovarian cancer? In multiple myeloma and chronic lymphocytic leukemia, high expression of the related molecule CD38 on tumor cells indicates a worse prognosis (3). CD157 expression appears to be associated with poor outcome in ovarian cancer because tumors that expressed high levels of CD157 as assessed by histological scoring gave worse overall survival in comparison with those with lower levels of CD157 in this study. The effect was more profound in the tumors of serous histology. However, given the myriad of prognostic markers for this disease (CA-125, gene signatures, and cyclin E to name a few), it is not clear whether another one will greatly assist the field or the management of these patients.

It may be more valuable to look closely at the biology. It is interesting to speculate how the function of CD157 might contribute to a more aggressive ovarian cancer or to the generation of a chemoresistant phenotype. CD157 binds to its ligand, CD31, that is expressed on endothelial cells, thereby anchoring the cancer cell and possibly activating signaling in either cell type. CD157 does not have a transmembrane domain, but it interacts with other key cell surface molecules to increase their signaling (2). For example, CD31-mediated ligation of CD157 induces colocalization and tyrosine phosphorylation of focal adhesion kinase (2), which potentially triggers intracellular signal transduction downstream of src-family kinases. Similarly, binding of the family member CD38 to CD31 triggers phosphorylation of c-abl and extracellular signal-regulated kinase/mitogen-associated protein kinase (4). The focal adhesion kinase–mitogen-associated protein kinase signaling cascade could mediate increased cellular migration.

Could CD157 provide a target for therapeutic intervention? A monoclonal antibody that blocks CD157 binding to CD31 or similar counterreceptors might prevent invasion of malignant ovarian epithelial cells, but it is not likely to affect ovarian cancer cells that are in the ascites because CD157 was not expressed by the nonadherent ascites cells in the current study. If CD157 promotes invasion in the metastatic ovarian cancer cells, but is not expressed when the cells are dispersed in the ascites, it is unclear whether CD157 must be reexpressed to promote heterotypic cellular adhesion or whether the reexpression of CD157 on adherent cells is triggered by the microenvironment after the ovarian cancer cells have metastasized. Each of these possibilities in the timing of CD157 expression in the process of ovarian cancer dissemination would have different implications for the development of CD157 as a potential therapeutic target. It also remains to be explored whether the interaction between CD157 and CD31 activates the endothelial cell through CD31, and whether this triggers angiogenesis. This activity would provide solid support for CD157 as a therapeutic target.

The enzymatic activity of CD157 may be as important as its role as a receptor. When CD157 cleaves nicotinamide adenine dinucleotide to generate ADP-ribose and cyclic ADP-ribose (5), the reaction generates substrate for ADP-ribosyl transferases and polymerases. ADP-ribosylation of cell surface proteins may modulate their function and promote aggressiveness in ovarian cancer. This potential outcome of CD157 activity warrants further examination, given the recent development of poly-ADP-ribose polymerase inhibitors in the clinic. Specifically, which proteins become ADP-ribosylated at the cell surface? How is this affected by CD157 activity? How might this affect the CD31-expressing cells?

As with most interesting biomarker studies, this one generates more questions than answers. To be clinically important, these results need additional validation and better understanding from a biological and biochemical standpoint. Once these stromal–epithelial interactions are mapped out, it is likely that novel therapeutic approaches will evolve leading to more effective treatment of women with ovarian cancer."

http://jnci.oxfordjournals.org/cgi/content/full/djq269

Cancer is heterogeneous
What research scientists in universities and cancer centers have been doing for the past ten years is trying to figure out a way to use mutation testing to look for patterns of gene expression which correlate with and predict for the activity of anticancer drugs. However, genes do not operate alone within the cell but in an intricate network of interactions.

Since the new millenium there has been the increasing acceptance of the concept that cancer is a very heterogenous disease and that it would be a good thing to try and "individualize' treatment. The cell is a system, an integrated, intereacting network of genes, proteins and other cellular constituents that produce functions. One needs to analyze the systems' response to drug treatments, not just one or a few targets (pathways).

A gene test is simply incapable of capturing the complexities associated with human tumor biology. Examing a patient's DNA can give physicians a lot of information, but as the NCI has concluded (J Natl Cancer Inst. March 16, 2010), it cannot determine treatment plans for patients. It cannot test sensitivity to any of the targeted therapies. They just test for "theoretical" candidates for targeted therapy.

Cancer dynamics are not linear, Cancer biology does not conform to the dictates of molecular biologists. Once again, we are forced to confront the realization that genotype does not equal phenotype. Cancer cells utilize cross talk and redundancy to circumvent therapies. They back up, zig-zag and move in reverse, regardless of what the sign posts say.

The building blocks of human biology are carefully construed into the complexities that we recognize as human beings. However appealing gene profiling may appear to those engaged in this field, it will be years, perhaps decades, before these profiles can approximate the vagaries of human cancer.

Functional profiling analyses, which measure biological signals rather than DNA indicators, will continue to provide clinically validated information and play an important role in cancer drug selection. The data that support functional profiling analyses is demonstrably greater and more compelling than any data currently generated from DNA analyses.

Functional profiling assesses the activity of a drug upon combined effect of all cellular processes, using several metabolic (cell metabolism) and morphologic (structure) endpoints, at the cell "population" level, rather than at the "single cell" level, measuring the interaction of the entire genome.

The original Human Genome Project dealt with a homogeneous population of normal diploid cells. This is different from primary tumors, which are heterogeneous and have a genomic signature unique to each and every patient. Functional profiling is a biomarker of heterogeneous cancer cells and genomic signatures unique to every individual patient.