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SMAD4--molecular gladiator of the TGF-beta signaling is trampled upon by mutational insufficiency in colorectal carcinoma of Kashmiri population: an analysis with relation to KRAS proto-oncogene.

Sameer AS, Chowdri NA, Syeed N, Banday MZ, Shah ZA, Siddiqi MA - BMC Cancer (2010)

Bottom Line: We examined the paired tumor and normal tissue specimens of 86 CRC patients for the occurrence of aberrations in MCR region of SMAD4 and exon 1 of KRAS by PCR-SSCP and/or PCR-Direct sequencing.The overall mutation rate of mutation cluster region (MCR) region of SMAD4 gene among 86 patients was 18.6% (16 of 86). 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well.Further more, we found a significant association of tumor location, tumor grade, node status, occupational exposure to pesticides and bleeding PR/Constipation with the mutation status of the SMAD4 gene (P = or < 0.05).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences, Soura, Srinagar, Kashmir, India.

ABSTRACT

Background: The development and progression of colorectal cancer has been extensively studied and the genes responsible have been well characterized. However the correlation between the SMAD4 gene mutations with KRAS mutant status has not been explored by many studies so far. Here, in this study we aimed to investigate the role of SMAD4 gene aberrations in the pathogenesis of CRC in Kashmir valley and to correlate it with various clinicopathological variables and KRAS mutant genotype.

Methods: We examined the paired tumor and normal tissue specimens of 86 CRC patients for the occurrence of aberrations in MCR region of SMAD4 and exon 1 of KRAS by PCR-SSCP and/or PCR-Direct sequencing.

Results: The overall mutation rate of mutation cluster region (MCR) region of SMAD4 gene among 86 patients was 18.6% (16 of 86). 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well. The association between the KRAS mutant genotype with SMAD4 mutants was found to be significant (P = or < 0.05). Further more, we found a significant association of tumor location, tumor grade, node status, occupational exposure to pesticides and bleeding PR/Constipation with the mutation status of the SMAD4 gene (P = or < 0.05).

Conclusion: Our study suggests that SMAD4 gene aberrations are the common event in CRC development but play a differential role in the progression of CRC in higher tumor grade (C+D) and its association with the KRAS mutant status suggest that these two molecules together are responsible for the progression of the tumor to higher/advanced stage.

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Partial nucleotide sequence (reverse) representing the mutant (A) and normal (B) {Shown by asterik and arrows}, of KRAS exon 1 gene. 3A: Transition of C > T at codon 19; CTT > TTT; Leu > Phe in Exon 1 of KRAS oncogene. 3B: Transversion of A > T at codon 16; AAG > TAG; Lys > Stop in Exon 1 of KRAS oncogene
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Figure 3: Partial nucleotide sequence (reverse) representing the mutant (A) and normal (B) {Shown by asterik and arrows}, of KRAS exon 1 gene. 3A: Transition of C > T at codon 19; CTT > TTT; Leu > Phe in Exon 1 of KRAS oncogene. 3B: Transversion of A > T at codon 16; AAG > TAG; Lys > Stop in Exon 1 of KRAS oncogene

Mentions: The overall mutation rate of mutation cluster region (MCR) of SMAD4 gene among 86 patients was 18.6% (16 of 86) [Table 2, Figure 1 &2]. 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well, the data (of KRAS mutations only) has been previously declared by our lab in two studies [14,15] by Sameer et al, 2009. Out of 11 KRAS mutants seven had mutations that has been reported already by our lab. In addition to those we also found two new novel mutations in KRAS oncogene in new procured tumor tissue samples. One was the A:T > T:A transversion of in codon 16 resulting in the truncation (AAG > TAG; Lys > Stop) of Kras protein in two tumor tissues and second was the C:T > T:C transition at codon 19 leading to change of leucine to phenaylalanine (CTT > TTT) in two tumor tissues [Table 2, Figures 3 &4]. In Total 21 of 86 (24.4%) tumor tissues had mutant KRAS gene out of these 21, 11 (52.4%) were SMAD4 gene mutants [Table 3 &4]. There were 9 (56.25%) tumors which had both KRAS activating mutations as well as SMAD4 single point mutations. Furthermore, in case of advanced/higher grade tumors (C+D = 48), KRAS gene mutations was found 15 (31.25%) and SMAD4 gene was found to be mutated in 14 (29.2%) tumors. Also, 9 (18.75%) of C + D grade tumors had mutations in both KRAS as well as SMAD4 gene as compared to only 2 (5.2%) of A+B grade tumors [Table 4 &5]. The mutant status of KRAS and SMAD4 gene was found to be significantly associated with the higher tumor grade (C+D) (P value = 0.03).


SMAD4--molecular gladiator of the TGF-beta signaling is trampled upon by mutational insufficiency in colorectal carcinoma of Kashmiri population: an analysis with relation to KRAS proto-oncogene.

Sameer AS, Chowdri NA, Syeed N, Banday MZ, Shah ZA, Siddiqi MA - BMC Cancer (2010)

Partial nucleotide sequence (reverse) representing the mutant (A) and normal (B) {Shown by asterik and arrows}, of KRAS exon 1 gene. 3A: Transition of C > T at codon 19; CTT > TTT; Leu > Phe in Exon 1 of KRAS oncogene. 3B: Transversion of A > T at codon 16; AAG > TAG; Lys > Stop in Exon 1 of KRAS oncogene
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927996&req=5

Figure 3: Partial nucleotide sequence (reverse) representing the mutant (A) and normal (B) {Shown by asterik and arrows}, of KRAS exon 1 gene. 3A: Transition of C > T at codon 19; CTT > TTT; Leu > Phe in Exon 1 of KRAS oncogene. 3B: Transversion of A > T at codon 16; AAG > TAG; Lys > Stop in Exon 1 of KRAS oncogene
Mentions: The overall mutation rate of mutation cluster region (MCR) of SMAD4 gene among 86 patients was 18.6% (16 of 86) [Table 2, Figure 1 &2]. 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well, the data (of KRAS mutations only) has been previously declared by our lab in two studies [14,15] by Sameer et al, 2009. Out of 11 KRAS mutants seven had mutations that has been reported already by our lab. In addition to those we also found two new novel mutations in KRAS oncogene in new procured tumor tissue samples. One was the A:T > T:A transversion of in codon 16 resulting in the truncation (AAG > TAG; Lys > Stop) of Kras protein in two tumor tissues and second was the C:T > T:C transition at codon 19 leading to change of leucine to phenaylalanine (CTT > TTT) in two tumor tissues [Table 2, Figures 3 &4]. In Total 21 of 86 (24.4%) tumor tissues had mutant KRAS gene out of these 21, 11 (52.4%) were SMAD4 gene mutants [Table 3 &4]. There were 9 (56.25%) tumors which had both KRAS activating mutations as well as SMAD4 single point mutations. Furthermore, in case of advanced/higher grade tumors (C+D = 48), KRAS gene mutations was found 15 (31.25%) and SMAD4 gene was found to be mutated in 14 (29.2%) tumors. Also, 9 (18.75%) of C + D grade tumors had mutations in both KRAS as well as SMAD4 gene as compared to only 2 (5.2%) of A+B grade tumors [Table 4 &5]. The mutant status of KRAS and SMAD4 gene was found to be significantly associated with the higher tumor grade (C+D) (P value = 0.03).

Bottom Line: We examined the paired tumor and normal tissue specimens of 86 CRC patients for the occurrence of aberrations in MCR region of SMAD4 and exon 1 of KRAS by PCR-SSCP and/or PCR-Direct sequencing.The overall mutation rate of mutation cluster region (MCR) region of SMAD4 gene among 86 patients was 18.6% (16 of 86). 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well.Further more, we found a significant association of tumor location, tumor grade, node status, occupational exposure to pesticides and bleeding PR/Constipation with the mutation status of the SMAD4 gene (P = or < 0.05).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences, Soura, Srinagar, Kashmir, India.

ABSTRACT

Background: The development and progression of colorectal cancer has been extensively studied and the genes responsible have been well characterized. However the correlation between the SMAD4 gene mutations with KRAS mutant status has not been explored by many studies so far. Here, in this study we aimed to investigate the role of SMAD4 gene aberrations in the pathogenesis of CRC in Kashmir valley and to correlate it with various clinicopathological variables and KRAS mutant genotype.

Methods: We examined the paired tumor and normal tissue specimens of 86 CRC patients for the occurrence of aberrations in MCR region of SMAD4 and exon 1 of KRAS by PCR-SSCP and/or PCR-Direct sequencing.

Results: The overall mutation rate of mutation cluster region (MCR) region of SMAD4 gene among 86 patients was 18.6% (16 of 86). 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well. The association between the KRAS mutant genotype with SMAD4 mutants was found to be significant (P = or < 0.05). Further more, we found a significant association of tumor location, tumor grade, node status, occupational exposure to pesticides and bleeding PR/Constipation with the mutation status of the SMAD4 gene (P = or < 0.05).

Conclusion: Our study suggests that SMAD4 gene aberrations are the common event in CRC development but play a differential role in the progression of CRC in higher tumor grade (C+D) and its association with the KRAS mutant status suggest that these two molecules together are responsible for the progression of the tumor to higher/advanced stage.

Show MeSH
Related in: MedlinePlus