Programmed cell death 4 loss increases tumor cell invasion and is regulated by miR-21 in oral squamous cell carcinoma.
BACKGROUND
The tumor suppressor Programmed Cell Death 4 (PDCD4) has been found to be under-expressed in several cancers and associated with disease progression and metastasis. There are no current studies characterizing PDCD4 expression and its clinical relevance in Oral Squamous Cell Carcinoma (OSCC). Since nodal metastasis is a major prognostic factor in OSCC, we focused on determining whether PDCD4 under-expression was associated with patient nodal status and had functional relevance in OSCC invasion. We also examined PDCD4 regulation by microRNA 21 (miR-21) in OSCC.


RESULTS
PDCD4 mRNA expression levels were assessed in 50 OSCCs and 25 normal oral tissues. PDCD4 was under-expressed in 43/50 (86%) OSCCs, with significantly reduced mRNA levels in patients with nodal metastasis (p = 0.0027), and marginally associated with T3-T4 tumor stage (p = 0.054). PDCD4 protein expression was assessed, by immunohistochemistry (IHC), in 28/50 OSCCs and adjacent normal tissues; PDCD4 protein was absent/under-expressed in 25/28 (89%) OSCCs, and marginally associated with nodal metastasis (p = 0.059). A matrigel invasion assay showed that PDCD4 expression suppressed invasion, and siRNA-mediated PDCD4 loss was associated with increased invasive potential of oral carcinoma cells. Furthermore, we showed that miR-21 levels were increased in PDCD4-negative tumors, and that PDCD4 expression may be down-regulated in OSCC by direct binding of miR-21 to the 3'UTR PDCD4 mRNA.


CONCLUSIONS
Our data show an association between the loss of PDCD4 expression, tumorigenesis and invasion in OSCC, and also identify a mechanism of PDCD4 down-regulation by microRNA-21 in oral carcinoma. PDCD4 association with nodal metastasis and invasion suggests that PDCD4 may be a clinically relevant biomarker with prognostic value in OSCC.
Reis
Patricia P
PP
Division of Applied Molecular Oncology, Princess Margaret Hospital, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada. suzanne.kamel-reid@uhn.on.ca.
Tomenson
Miranda
M
Cervigne
Nilva K
NK
Machado
Jerry
J
Jurisica
Igor
I
Pintilie
Melania
M
Sukhai
Mahadeo A
MA
Perez-Ordonez
Bayardo
B
Grénman
Reidar
R
Gilbert
Ralph W
RW
Gullane
Patrick J
PJ
Irish
Jonathan C
JC
Kamel-Reid
Suzanne
S
D020413:3' Untranslated Regions / Q000235:genetics / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002460:Cell Line; D045744:Cell Line, Tumor; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis / Q000235:genetics / Q000473:pathology*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009062:Mouth Neoplasms / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D020413:3' Untranslated Regions; D051017:Apoptosis Regulatory Proteins; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C114487:PDCD4 protein, human; D016601:RNA-Binding Proteins