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The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine

BACKGROUND: Alterations in gene splicing occur in human sporadic colorectal cancer (CRC) and may contribute to tumour progression. The K-ras proto-oncogene encodes two splice variants, K-ras 4A and 4B, and K-ras activating mutations which jointly affect both isoforms are prevalent in CRC. Past studi...

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Autores principales: Patek, Charles E, Arends, Mark J, Rose, Lorraine, Luo, Feijun, Walker, Marion, Devenney, Paul S, Berry, Rachel L, Lawrence, Nicola J, Ridgway, Rachel A, Sansom, Owen J, Hooper, Martin L
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2008
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2442095/
https://www.ncbi.nlm.nih.gov/pubmed/18554389
http://dx.doi.org/10.1186/1471-230X-8-24
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author Patek, Charles E
Arends, Mark J
Rose, Lorraine
Luo, Feijun
Walker, Marion
Devenney, Paul S
Berry, Rachel L
Lawrence, Nicola J
Ridgway, Rachel A
Sansom, Owen J
Hooper, Martin L
author_facet Patek, Charles E
Arends, Mark J
Rose, Lorraine
Luo, Feijun
Walker, Marion
Devenney, Paul S
Berry, Rachel L
Lawrence, Nicola J
Ridgway, Rachel A
Sansom, Owen J
Hooper, Martin L
author_sort Patek, Charles E
collection PubMed
description BACKGROUND: Alterations in gene splicing occur in human sporadic colorectal cancer (CRC) and may contribute to tumour progression. The K-ras proto-oncogene encodes two splice variants, K-ras 4A and 4B, and K-ras activating mutations which jointly affect both isoforms are prevalent in CRC. Past studies have established that splicing of both the K-ras oncogene and proto-oncogene is altered in CRC in favour of K-ras 4B. The present study addressed whether the K-Ras 4A proto-oncoprotein can suppress tumour development in the absence of its oncogenic allele, utilising the Apc(Min/+ )(Min) mouse that spontaneously develops intestinal tumours that do not harbour K-ras activating mutations, and the K-ras(tmΔ4A/tmΔ4A )mouse that can express the K-ras 4B splice variant only. By this means tumorigenesis in the small intestine was compared between Apc(Min/+), K-ras(+/+ )and Apc(Min/+), K-ras(tmΔ4A/tmΔ4A )mice that can, and cannot, express the K-ras 4A proto-oncoprotein respectively. METHODS: The relative levels of expression of the K-ras splice variants in normal small intestine and small intestinal tumours were quantified by real-time RT-qPCR analysis. Inbred (C57BL/6) Apc(Min/+), K-ras(+/+ )and Apc(Min/+), K-ras(tmΔ4A/tmΔ4A )mice were generated and the genotypes confirmed by PCR analysis. Survival of stocks was compared by the Mantel-Haenszel test, and tumour number and area compared by Student's t-test in outwardly healthy mice at approximately 106 and 152 days of age. DNA sequencing of codons 12, 13 and 61 was performed to confirm the intestinal tumours did not harbour a K-ras activating mutation. RESULTS: The K-ras 4A transcript accounted for about 50% of K-ras expressed in the small intestine of both wild-type and Min mice. Tumours in the small intestine of Min mice showed increased levels of K-ras 4B transcript expression, but no appreciable change in K-ras 4A transcript levels. No K-ras activating mutations were detected in 27 intestinal tumours derived from Min and compound mutant Min mice. K-Ras 4A deficiency did not affect mouse survival, or tumour number, size or histopathology. CONCLUSION: The K-Ras 4A proto-oncoprotein does not exhibit tumour suppressor activity in the small intestine, even though the K-ras 4A/4B ratio is reduced in adenomas lacking K-ras activating mutations.
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spelling pubmed-24420952008-07-01 The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine Patek, Charles E Arends, Mark J Rose, Lorraine Luo, Feijun Walker, Marion Devenney, Paul S Berry, Rachel L Lawrence, Nicola J Ridgway, Rachel A Sansom, Owen J Hooper, Martin L BMC Gastroenterol Research Article BACKGROUND: Alterations in gene splicing occur in human sporadic colorectal cancer (CRC) and may contribute to tumour progression. The K-ras proto-oncogene encodes two splice variants, K-ras 4A and 4B, and K-ras activating mutations which jointly affect both isoforms are prevalent in CRC. Past studies have established that splicing of both the K-ras oncogene and proto-oncogene is altered in CRC in favour of K-ras 4B. The present study addressed whether the K-Ras 4A proto-oncoprotein can suppress tumour development in the absence of its oncogenic allele, utilising the Apc(Min/+ )(Min) mouse that spontaneously develops intestinal tumours that do not harbour K-ras activating mutations, and the K-ras(tmΔ4A/tmΔ4A )mouse that can express the K-ras 4B splice variant only. By this means tumorigenesis in the small intestine was compared between Apc(Min/+), K-ras(+/+ )and Apc(Min/+), K-ras(tmΔ4A/tmΔ4A )mice that can, and cannot, express the K-ras 4A proto-oncoprotein respectively. METHODS: The relative levels of expression of the K-ras splice variants in normal small intestine and small intestinal tumours were quantified by real-time RT-qPCR analysis. Inbred (C57BL/6) Apc(Min/+), K-ras(+/+ )and Apc(Min/+), K-ras(tmΔ4A/tmΔ4A )mice were generated and the genotypes confirmed by PCR analysis. Survival of stocks was compared by the Mantel-Haenszel test, and tumour number and area compared by Student's t-test in outwardly healthy mice at approximately 106 and 152 days of age. DNA sequencing of codons 12, 13 and 61 was performed to confirm the intestinal tumours did not harbour a K-ras activating mutation. RESULTS: The K-ras 4A transcript accounted for about 50% of K-ras expressed in the small intestine of both wild-type and Min mice. Tumours in the small intestine of Min mice showed increased levels of K-ras 4B transcript expression, but no appreciable change in K-ras 4A transcript levels. No K-ras activating mutations were detected in 27 intestinal tumours derived from Min and compound mutant Min mice. K-Ras 4A deficiency did not affect mouse survival, or tumour number, size or histopathology. CONCLUSION: The K-Ras 4A proto-oncoprotein does not exhibit tumour suppressor activity in the small intestine, even though the K-ras 4A/4B ratio is reduced in adenomas lacking K-ras activating mutations. BioMed Central 2008-06-13 /pmc/articles/PMC2442095/ /pubmed/18554389 http://dx.doi.org/10.1186/1471-230X-8-24 Text en Copyright © 2008 Patek et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Patek, Charles E
Arends, Mark J
Rose, Lorraine
Luo, Feijun
Walker, Marion
Devenney, Paul S
Berry, Rachel L
Lawrence, Nicola J
Ridgway, Rachel A
Sansom, Owen J
Hooper, Martin L
The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine
title The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine
title_full The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine
title_fullStr The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine
title_full_unstemmed The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine
title_short The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the Apc(Min/+ )mouse small intestine
title_sort pro-apoptotic k-ras 4a proto-oncoprotein does not affect tumorigenesis in the apc(min/+ )mouse small intestine
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2442095/
https://www.ncbi.nlm.nih.gov/pubmed/18554389
http://dx.doi.org/10.1186/1471-230X-8-24
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