Parathyroid hormone-related protein as a novel tumor marker in pancreatic adenocarcinoma.
BACKGROUND
Parathyroid hormone-related protein (PTHrP) can act as an oncoprotein to regulate the growth and proliferation of many common malignancies, including pancreatic cancer. Previous studies have shown that PTHrP is produced by human pancreatic cancer cell lines, can be shown in the cytoplasm and nucleus of paraffin-embedded pancreatic adenocarcinoma tumor specimens, and is secreted into the media of cultured pancreatic adenocarcinoma cells. We hypothesized that PTHrP could serve as a tumor-marker for growth of pancreatic cancer in vivo.


OBJECTIVE
To test this hypothesis, we used an orthotopic model developed in our laboratory of the PTHrP-producing human pancreatic cancer line, BxPC-3. This tumor was stably transduced with green fluorescence protein (GFP) to facilitate visualization of tumor growth and metastases. At early (5 weeks) and late (13 weeks) time points after surgical orthotopic implantation, serum PTHrP was measured and primary and metastatic tumor burden was determined for each mouse by assessing GFP expression.


RESULTS
By 5 weeks after surgical orthotopic implantation (early group), the mean serum PTHrP level was 33.3 pg/mL. In contrast, by 13 weeks after surgical orthotopic implantation (late group), the mean serum PTHrP level increased to 158.5 pg/mL. These differences were highly significant (p < 0.001, Student t test). Numerous metastatic lesions were readily visualized by GFP in the late group. Serum PTHrP levels measured by immunoassay correlated with primary pancreatic tumor weights and serum calcium levels (p <0.01). PTHrP levels were not detectable (<21 pg/mL) in any of the 10 control mice with no tumor. Western blotting of BxPC-3-GFP tumor lysates confirmed the presence of PTHrP. BxPC-3-GFP tumor tissue stained with antibody to PTHrP.


CONCLUSIONS
These results indicate that PTHrP can serve as a tumor marker in animal models of pancreatic cancer and may be a useful tumor marker for clinical pancreatic adenocarcinoma.
Bouvet
Michael
M
Department of Surgery, University of California San Diego and the San Diego VA Medical Center, La Jolla, California 92161, USA. mbouvet@ucsd.edu
Nardin
Stephanie R
SR
Burton
Douglas W
DW
Lee
Natalie C
NC
Yang
Meng
M
Wang
Xiaoen
X
Baranov
Eugene
E
Behling
Cynthia
C
Moossa
A R
AR
Hoffman
Robert M
RM
Deftos
Leonard J
LJ
D000230:Adenocarcinoma / Q000097:blood* / Q000473:pathology; D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood*; D015153:Blotting, Western; D002118:Calcium / Q000097:blood; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D006801:Humans; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000097:blood* / Q000473:pathology; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000032:analysis*; D011994:Recombinant Proteins / Q000032:analysis; D014162:Transfection; D014407:Tumor Cells, Cultured
D014408:Biomarkers, Tumor; D008164:Luminescent Proteins; C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D002118:Calcium