Isoform-specific upregulation of palladin in human and murine pancreas tumors.
Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with a characteristic pattern of early metastasis, which is driving a search for biomarkers that can be used to detect the cancer at an early stage. Recently, the actin-associated protein palladin was identified as a candidate biomarker when it was shown that palladin is mutated in a rare inherited form of PDA, and overexpressed in many sporadic pancreas tumors and premalignant precursors. In this study, we analyzed the expression of palladin isoforms in murine and human PDA and explored palladin's potential use in diagnosing PDA. We performed immunohistochemistry and immunoblot analyses on patient samples and tumor-derived cells using an isoform-selective monoclonal antibody and a pan-palladin polyclonal antibody. Immunoblot and real-time quantitative reverse transcription-PCR were used to quantify palladin mRNA levels in human samples. We show that there are two major palladin isoforms expressed in pancreas: 65 and 85-90 kDa. The 65 kDa isoform is expressed in both normal and neoplastic ductal epithelial cells. The 85-90 kDa palladin isoform is highly overexpressed in tumor-associated fibroblasts (TAFs) in both primary and metastatic tumors compared to normal pancreas, in samples obtained from either human patients or genetically engineered mice. In tumor-derived cultured cells, expression of palladin isoforms follows cell-type specific patterns, with the 85-90 kDa isoform in TAFs, and the 65 kDa isoform predominating in normal and neoplastic epithelial cells. These results suggest that upregulation of 85-90 kDa palladin isoform may play a role in the establishment of the TAF phenotype, and thus in the formation of a desmoplastic tumor microenvironment. Thus, palladin may have a potential use in the early diagnosis of PDA and may have much broader significance in understanding metastatic behavior.
Goicoechea
Silvia M
SM
Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina, USA. sgoico@med.unc.edu
Bednarski
Brian
B
Stack
Christianna
C
Cowan
David W
DW
Volmar
Keith
K
Thorne
Leigh
L
Cukierman
Edna
E
Rustgi
Anil K
AK
Brentnall
Teresa
T
Hwang
Rosa F
RF
McCulloch
Christopher A G
CA
Yeh
Jen Jen
JJ
Bentrem
David J
DJ
Hochwald
Steven N
SN
Hingorani
Sunil R
SR
Kim
Hong Jin
HJ
Otey
Carol A
CA
D000818:Animals; D014408:Biomarkers, Tumor; D021441:Carcinoma, Pancreatic Ductal / Q000175:diagnosis*; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000235:genetics*; D005347:Fibroblasts / Q000473:pathology; D006801:Humans; D007118:Immunoassay; D051379:Mice; D009154:Mutation; D009363:Neoplasm Proteins; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
D014408:Biomarkers, Tumor; D003598:Cytoskeletal Proteins; D009363:Neoplasm Proteins; C412722:PALLD protein, human; D010750:Phosphoproteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C485873:palladin protein, mouse