Oncogenic KRAS induces progenitor cell expansion and malignant transformation in zebrafish exocrine pancreas.
OBJECTIVE
Although the cell of origin for pancreatic cancer remains unknown, prior studies have suggested that pancreatic neoplasia may be initiated in progenitor-like cells. To examine the effects of oncogene activation within the pancreatic progenitor pool, we devised a system for real-time visualization of both normal and oncogenic KRAS-expressing pancreatic progenitor cells in living zebrafish embryos.


METHODS
By using BAC transgenes under the regulation of ptf1a regulatory elements, we expressed either extended green fluorescent protein (eGFP) alone or eGFP fused to oncogenic KRAS in developing zebrafish pancreas.


RESULTS
After their initial specification, normal eGFP-labeled pancreatic progenitor cells were observed to actively migrate away from the forming endodermal gut tube, and subsequently underwent characteristic exocrine differentiation. In contrast, pancreatic progenitor cells expressing oncogenic KRAS underwent normal specification and migration, but failed to differentiate. This block in differentiation resulted in the abnormal persistence of an undifferentiated progenitor pool, and was associated with the subsequent formation of invasive pancreatic cancer. These tumors showed several features in common with the human disease, including evidence of abnormal Hedgehog pathway activation.


CONCLUSIONS
These results provide a unique view of the tumor-initiating effects of oncogenic KRAS in a living vertebrate organism, and suggest that zebrafish models of pancreatic cancer may prove useful in advancing our understanding of the human disease.
Department of Surgery, The Sol Goldman Center for Pancreatic Cancer Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Seung Woo
SW
Park
Jon M
JM
Davison
Jerry
J
Rhee
Ralph H
RH
Hruban
Anirban
A
Maitra
Steven D
SD
Leach
D000818:Animals; D030801:Animals, Genetically Modified; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D022202:Chromosomes, Artificial, Bacterial; D015972:Gene Expression Regulation, Neoplastic; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000378:metabolism; D053823:Hedgehog Proteins / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D009361:Neoplasm Invasiveness; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D046790:Pancreas, Exocrine / Q000378:metabolism* / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D053823:Hedgehog Proteins; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C485184:enhanced green fluorescent protein; C062602:transcription factor PTF1; D049452:Green Fluorescent Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins