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Mutations in TGFbeta-RII and BAX mediate tumor progression in the later stages of colorectal cancer with microsatellite instability.

Yashiro M, Hirakawa K, Boland CR - BMC Cancer (2010)

Bottom Line: In this study, early stage CRCs were examined for frameshift mutations in these target genes, and compared with late stage tumors and CRC cell lines.There is a statistical association (p = 0.014) between mutation in any one gene and tumor stage.TGFbetaRII, BAX, hMSH3 and hMSH6 mutations are relatively late events in the genesis of MSI CRCs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Osaka, Japan. m9312510@med.osaka-cu.ac.jp

ABSTRACT

Background: Microsatellite instability (MSI) occurs in 15% of colorectal cancers (CRC). The genetic targets for mutation in the MSI phenotype include somatic mutations in the transforming growth factor beta receptor typeII (TGFbetaRII), BAX, hMSH3 and hMSH6. It is not clear how mutations of these genes mediate tumor progression in the MSI pathway, and the temporal sequence of these mutations remains uncertain. In this study, early stage CRCs were examined for frameshift mutations in these target genes, and compared with late stage tumors and CRC cell lines.

Methods: We investigated 6 CRC cell lines and 71 sporadic CRCs, including 61 early stage cancers and 10 late stage cancers. Mutations of repetitive mononucleotide tracts in the coding regions of TGFbetaRII, BAX, hMSH3, hMSH6, IGFIIR and Fas antigen were identified by direct sequencing.

Results: Thirteen (18.3%) of 71 CRC, including 9/61 (14.7%) early stage cancers and 4/10 (40%) late stage cancers, were identified as MSI and analyzed for frameshift mutations. No mutation in the target genes was observed in any of the 9 early stage MSI CRCs. In contrast, frameshift mutations of TGFbetaRII, BAX, hMSH3 and hMSH6 were present in 3/4 late stage MSI tumors. There is a statistical association (p = 0.014) between mutation in any one gene and tumor stage.

Conclusions: TGFbetaRII, BAX, hMSH3 and hMSH6 mutations are relatively late events in the genesis of MSI CRCs. The frameshift mutations in these target genes might mediate progression from early to late stage cancer, rather than mediating the adenoma to carcinoma transition.

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Frameshift mutations in CRC cell lines. Lane a: products from normal control DNA. The products of MSI cell lines are shown in Lanes b (HCT116), c (LoVo), e (LS174-T) and f (DLD1). Products of non-MSI cell lines are shown in Lanes d (SW480) and g (HT29). The genes are indicated at the left. Arrowheads indicate frameshift mutations in cell lines.
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Figure 1: Frameshift mutations in CRC cell lines. Lane a: products from normal control DNA. The products of MSI cell lines are shown in Lanes b (HCT116), c (LoVo), e (LS174-T) and f (DLD1). Products of non-MSI cell lines are shown in Lanes d (SW480) and g (HT29). The genes are indicated at the left. Arrowheads indicate frameshift mutations in cell lines.

Mentions: It has been reported that HCT116, LoVo, LS174t and DLD1 have the MSI phenotype, whereas SW480 and HT29 do not [16]. In this study, frameshift mutations in the (A)10 tract of TGFβRII were found in all 4 MMR-deficient cell lines: HCT116, LoVo, LS174t and DLD1. All cell lines have only mutant alleles of TGFβRII, either (A)9 or (A)8. Microsatellite alterations in the (G)8 tract of BAX were present in HCT116, LoVo and LS174t. LoVo and LS174t cells had only (G)9 and (G)7 mutant BAX alleles; HCT116 had one (G)7 mutant allele and one (G)8wild-type allele. Deletions in the (A)8 tract of the coding sequence of hMSH3 were present in HCT116. Insertion and deletion mutations in the (C)8 tract of hMSH6 were detected in HCT116 and LS174t, respectively. In contrast, the MMR-proficient cell lines SW480 and HT29 demonstrated microsatellite stability, and did not have mutations in TGFβRII, BAX, hMSH3 or hMSH6. No alterations in the (G)8 tract of IGFIIR or the (T)7 tract of Fas antigen were found in any of the cell lines examined (Figure 1).


Mutations in TGFbeta-RII and BAX mediate tumor progression in the later stages of colorectal cancer with microsatellite instability.

Yashiro M, Hirakawa K, Boland CR - BMC Cancer (2010)

Frameshift mutations in CRC cell lines. Lane a: products from normal control DNA. The products of MSI cell lines are shown in Lanes b (HCT116), c (LoVo), e (LS174-T) and f (DLD1). Products of non-MSI cell lines are shown in Lanes d (SW480) and g (HT29). The genes are indicated at the left. Arrowheads indicate frameshift mutations in cell lines.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927997&req=5

Figure 1: Frameshift mutations in CRC cell lines. Lane a: products from normal control DNA. The products of MSI cell lines are shown in Lanes b (HCT116), c (LoVo), e (LS174-T) and f (DLD1). Products of non-MSI cell lines are shown in Lanes d (SW480) and g (HT29). The genes are indicated at the left. Arrowheads indicate frameshift mutations in cell lines.
Mentions: It has been reported that HCT116, LoVo, LS174t and DLD1 have the MSI phenotype, whereas SW480 and HT29 do not [16]. In this study, frameshift mutations in the (A)10 tract of TGFβRII were found in all 4 MMR-deficient cell lines: HCT116, LoVo, LS174t and DLD1. All cell lines have only mutant alleles of TGFβRII, either (A)9 or (A)8. Microsatellite alterations in the (G)8 tract of BAX were present in HCT116, LoVo and LS174t. LoVo and LS174t cells had only (G)9 and (G)7 mutant BAX alleles; HCT116 had one (G)7 mutant allele and one (G)8wild-type allele. Deletions in the (A)8 tract of the coding sequence of hMSH3 were present in HCT116. Insertion and deletion mutations in the (C)8 tract of hMSH6 were detected in HCT116 and LS174t, respectively. In contrast, the MMR-proficient cell lines SW480 and HT29 demonstrated microsatellite stability, and did not have mutations in TGFβRII, BAX, hMSH3 or hMSH6. No alterations in the (G)8 tract of IGFIIR or the (T)7 tract of Fas antigen were found in any of the cell lines examined (Figure 1).

Bottom Line: In this study, early stage CRCs were examined for frameshift mutations in these target genes, and compared with late stage tumors and CRC cell lines.There is a statistical association (p = 0.014) between mutation in any one gene and tumor stage.TGFbetaRII, BAX, hMSH3 and hMSH6 mutations are relatively late events in the genesis of MSI CRCs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Osaka, Japan. m9312510@med.osaka-cu.ac.jp

ABSTRACT

Background: Microsatellite instability (MSI) occurs in 15% of colorectal cancers (CRC). The genetic targets for mutation in the MSI phenotype include somatic mutations in the transforming growth factor beta receptor typeII (TGFbetaRII), BAX, hMSH3 and hMSH6. It is not clear how mutations of these genes mediate tumor progression in the MSI pathway, and the temporal sequence of these mutations remains uncertain. In this study, early stage CRCs were examined for frameshift mutations in these target genes, and compared with late stage tumors and CRC cell lines.

Methods: We investigated 6 CRC cell lines and 71 sporadic CRCs, including 61 early stage cancers and 10 late stage cancers. Mutations of repetitive mononucleotide tracts in the coding regions of TGFbetaRII, BAX, hMSH3, hMSH6, IGFIIR and Fas antigen were identified by direct sequencing.

Results: Thirteen (18.3%) of 71 CRC, including 9/61 (14.7%) early stage cancers and 4/10 (40%) late stage cancers, were identified as MSI and analyzed for frameshift mutations. No mutation in the target genes was observed in any of the 9 early stage MSI CRCs. In contrast, frameshift mutations of TGFbetaRII, BAX, hMSH3 and hMSH6 were present in 3/4 late stage MSI tumors. There is a statistical association (p = 0.014) between mutation in any one gene and tumor stage.

Conclusions: TGFbetaRII, BAX, hMSH3 and hMSH6 mutations are relatively late events in the genesis of MSI CRCs. The frameshift mutations in these target genes might mediate progression from early to late stage cancer, rather than mediating the adenoma to carcinoma transition.

Show MeSH
Related in: MedlinePlus