Mechanisms of FUS1/TUSC2 deficiency in mesothelioma and its tumorigenic transcriptional effects.
BACKGROUND
FUS1/TUSC2 is a novel tumor suppressor located in the critical 3p21.3 chromosomal region frequently deleted in multiple cancers. We previously showed that Tusc2-deficient mice display a complex immuno-inflammatory phenotype with a predisposition to cancer. The goal of this study was to analyze possible involvement of TUSC2 in malignant pleural mesothelioma (MPM) - an aggressive inflammatory cancer associated with exposure to asbestos.


METHODS
TUSC2 insufficiency in clinical specimens of MPM was assessed via RT-PCR (mRNA level), Representational Oligonucleotide Microarray Analysis (DNA level), and immunohistochemical evaluation (protein level). A possible link between TUSC2 expression and exposure to asbestos was studied using asbestos-treated mesothelial cells and ROS (reactive oxygen species) scavengers. Transcripional effects of TUSC2 in MPM were assessed through expression array analysis of TUSC2-transfected MPM cells.


RESULTS
Expression of TUSC2 was downregulated in approximately 84% of MM specimens while loss of TUSC2-containing 3p21.3 region observed in approximately 36% of MPMs including stage 1 tumors. Exposure to asbestos led to a transcriptional suppression of TUSC2, which we found to be ROS-dependent. Expression array studies showed that TUSC2 activates transcription of multiple genes with tumor suppressor properties and down-regulates pro-tumorigenic genes, thus supporting its role as a tumor suppressor. In agreement with our knockout model, TUSC2 up-regulated IL-15 and also modulated more than 40 other genes (approximately 20% of total TUSC2-affected genes) associated with immune system. Among these genes, we identified CD24 and CD274, key immunoreceptors that regulate immunogenic T and B cells and play important roles in systemic autoimmune diseases. Finally, clinical significance of TUSC2 transcriptional effects was validated on the expression array data produced previously on clinical specimens of MPM. In this analysis, 42 TUSC2 targets proved to be concordantly modulated in MM serving as disease discriminators.


CONCLUSIONS
Our data support immuno-therapeutic potential of TUSC2, define its targets, and underscore its importance as a transcriptional stimulator of anti-tumorigenic pathways.
Ivanova
Alla V
AV
Hematology/Oncology Division, Vanderbilt Medical Center, Nashville, TN, USA. alla.ivanova@vanderbilt.edu
Ivanov
Sergey V
SV
Prudkin
Ljudmila
L
Nonaka
Daisuke
D
Liu
Zhandong
Z
Tsao
Anne
A
Wistuba
Ignacio
I
Roth
Jack
J
Pass
Harvey I
HI
D000595:Amino Acid Sequence; D001194:Asbestos / Q000633:toxicity; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D016166:Free Radical Scavengers / Q000378:metabolism; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D050839:Interferon Regulatory Factor-7 / Q000737:chemistry; D008654:Mesothelioma / Q000235:genetics* / Q000473:pathology; D008954:Models, Biological; D008969:Molecular Sequence Data; D010997:Pleural Neoplasms / Q000235:genetics* / Q000473:pathology; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism
D016166:Free Radical Scavengers; C494234:IRF7 protein, human; D050839:Interferon Regulatory Factor-7; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; C499993:TUSC2 protein, human; D025521:Tumor Suppressor Proteins; D001194:Asbestos