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Differential in vivo tumorigenicity of diverse KRAS mutations in vertebrate pancreas: A comprehensive survey.

Park JT, Johnson N, Liu S, Levesque M, Wang YJ, Ho H, Huso D, Maitra A, Parsons MJ, Prescott JD, Leach SD - Oncogene (2014)

Bottom Line: These mutations occur primarily at codon 12 and less frequently at codons 13 and 61.All eight tumorigenic KRAS mutations were associated with downstream MAPK/ERK pathway activation in preneoplastic pancreatic epithelium, whereas nontumorigenic mutations were not.These results suggest that the spectrum of KRAS mutations observed in human pancreatic cancer reflects selection based on variable tumorigenic capacities, including the ability to activate MAPK/ERK signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Johns Hopkins Medical Institutions, Baltimore, MD, USA.

ABSTRACT
Somatic activation of the KRAS proto-oncogene is evident in almost all pancreatic cancers, and appears to represent an initiating event. These mutations occur primarily at codon 12 and less frequently at codons 13 and 61. Although some studies have suggested that different KRAS mutations may have variable oncogenic properties, to date there has been no comprehensive functional comparison of multiple KRAS mutations in an in vivo vertebrate tumorigenesis system. We generated a Gal4/UAS-based zebrafish model of pancreatic tumorigenesis in which the pancreatic expression of UAS-regulated oncogenes is driven by a ptf1a:Gal4-VP16 driver line. This system allowed us to rapidly compare the ability of 12 different KRAS mutations (G12A, G12C, G12D, G12F, G12R, G12S, G12V, G13C, G13D, Q61L, Q61R and A146T) to drive pancreatic tumorigenesis in vivo. Among fish injected with one of five KRAS mutations reported in other tumor types but not in human pancreatic cancer, 2/79 (2.5%) developed pancreatic tumors, with both tumors arising in fish injected with A146T. In contrast, among fish injected with one of seven KRAS mutations known to occur in human pancreatic cancer, 22/106 (20.8%) developed pancreatic cancer. All eight tumorigenic KRAS mutations were associated with downstream MAPK/ERK pathway activation in preneoplastic pancreatic epithelium, whereas nontumorigenic mutations were not. These results suggest that the spectrum of KRAS mutations observed in human pancreatic cancer reflects selection based on variable tumorigenic capacities, including the ability to activate MAPK/ERK signaling.

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Comparison of in vivo tumorigenic capacity among twelve different oncogenic KRASmutant alleles(A) Percentage fish displaying eGFP fluorescence in the cerebellum (light green bars) and pancreas (darker green bars), along with incidence of pancreatic tumor formation at 3 months of age (red bars). Numbers in parentheses indicate number of fish examined for each mutant allele. (B) Comparison of KRAS mutant allele-specific efficiency of tumor formation in zebrafish for human KRAS mutations previously observed in human pancreatic cancer (n=7) vs. those not previously observed (n=5). Tumor-forming efficiency is significantly greater among mutations previously reported in human pancreatic cancer (p<0.01 by T-test).
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Figure 3: Comparison of in vivo tumorigenic capacity among twelve different oncogenic KRASmutant alleles(A) Percentage fish displaying eGFP fluorescence in the cerebellum (light green bars) and pancreas (darker green bars), along with incidence of pancreatic tumor formation at 3 months of age (red bars). Numbers in parentheses indicate number of fish examined for each mutant allele. (B) Comparison of KRAS mutant allele-specific efficiency of tumor formation in zebrafish for human KRAS mutations previously observed in human pancreatic cancer (n=7) vs. those not previously observed (n=5). Tumor-forming efficiency is significantly greater among mutations previously reported in human pancreatic cancer (p<0.01 by T-test).

Mentions: At 3 months of age, fish were randomly selected for examination of eGFP fluorescence in the cerebellum and pancreas. All twelve versions of activated KRAS were associated with high frequencies of eGFP fluorescence in the cerebellum, as shown for G12D and G12V in Fig. 2A and I. The percentage of fish displaying cerebellar eGFP fluorescence is shown in Fig. 3 (light green bars), and ranged from 44%-100%. As in the case of previously reported ptf1a:eGFP-KRASG12V transgenic fish 8, no cerebellar or hindbrain tumors were observed in transgenic fish expressing UAS:eGFP-KRASmutant transgenes.


Differential in vivo tumorigenicity of diverse KRAS mutations in vertebrate pancreas: A comprehensive survey.

Park JT, Johnson N, Liu S, Levesque M, Wang YJ, Ho H, Huso D, Maitra A, Parsons MJ, Prescott JD, Leach SD - Oncogene (2014)

Comparison of in vivo tumorigenic capacity among twelve different oncogenic KRASmutant alleles(A) Percentage fish displaying eGFP fluorescence in the cerebellum (light green bars) and pancreas (darker green bars), along with incidence of pancreatic tumor formation at 3 months of age (red bars). Numbers in parentheses indicate number of fish examined for each mutant allele. (B) Comparison of KRAS mutant allele-specific efficiency of tumor formation in zebrafish for human KRAS mutations previously observed in human pancreatic cancer (n=7) vs. those not previously observed (n=5). Tumor-forming efficiency is significantly greater among mutations previously reported in human pancreatic cancer (p<0.01 by T-test).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836617&req=5

Figure 3: Comparison of in vivo tumorigenic capacity among twelve different oncogenic KRASmutant alleles(A) Percentage fish displaying eGFP fluorescence in the cerebellum (light green bars) and pancreas (darker green bars), along with incidence of pancreatic tumor formation at 3 months of age (red bars). Numbers in parentheses indicate number of fish examined for each mutant allele. (B) Comparison of KRAS mutant allele-specific efficiency of tumor formation in zebrafish for human KRAS mutations previously observed in human pancreatic cancer (n=7) vs. those not previously observed (n=5). Tumor-forming efficiency is significantly greater among mutations previously reported in human pancreatic cancer (p<0.01 by T-test).
Mentions: At 3 months of age, fish were randomly selected for examination of eGFP fluorescence in the cerebellum and pancreas. All twelve versions of activated KRAS were associated with high frequencies of eGFP fluorescence in the cerebellum, as shown for G12D and G12V in Fig. 2A and I. The percentage of fish displaying cerebellar eGFP fluorescence is shown in Fig. 3 (light green bars), and ranged from 44%-100%. As in the case of previously reported ptf1a:eGFP-KRASG12V transgenic fish 8, no cerebellar or hindbrain tumors were observed in transgenic fish expressing UAS:eGFP-KRASmutant transgenes.

Bottom Line: These mutations occur primarily at codon 12 and less frequently at codons 13 and 61.All eight tumorigenic KRAS mutations were associated with downstream MAPK/ERK pathway activation in preneoplastic pancreatic epithelium, whereas nontumorigenic mutations were not.These results suggest that the spectrum of KRAS mutations observed in human pancreatic cancer reflects selection based on variable tumorigenic capacities, including the ability to activate MAPK/ERK signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Johns Hopkins Medical Institutions, Baltimore, MD, USA.

ABSTRACT
Somatic activation of the KRAS proto-oncogene is evident in almost all pancreatic cancers, and appears to represent an initiating event. These mutations occur primarily at codon 12 and less frequently at codons 13 and 61. Although some studies have suggested that different KRAS mutations may have variable oncogenic properties, to date there has been no comprehensive functional comparison of multiple KRAS mutations in an in vivo vertebrate tumorigenesis system. We generated a Gal4/UAS-based zebrafish model of pancreatic tumorigenesis in which the pancreatic expression of UAS-regulated oncogenes is driven by a ptf1a:Gal4-VP16 driver line. This system allowed us to rapidly compare the ability of 12 different KRAS mutations (G12A, G12C, G12D, G12F, G12R, G12S, G12V, G13C, G13D, Q61L, Q61R and A146T) to drive pancreatic tumorigenesis in vivo. Among fish injected with one of five KRAS mutations reported in other tumor types but not in human pancreatic cancer, 2/79 (2.5%) developed pancreatic tumors, with both tumors arising in fish injected with A146T. In contrast, among fish injected with one of seven KRAS mutations known to occur in human pancreatic cancer, 22/106 (20.8%) developed pancreatic cancer. All eight tumorigenic KRAS mutations were associated with downstream MAPK/ERK pathway activation in preneoplastic pancreatic epithelium, whereas nontumorigenic mutations were not. These results suggest that the spectrum of KRAS mutations observed in human pancreatic cancer reflects selection based on variable tumorigenic capacities, including the ability to activate MAPK/ERK signaling.

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Related in: MedlinePlus