Consistently, knockdown of Smad7 associates with inactivation of eIF2α, lower CDC25A expression and diminished fraction of proliferating cells in human CRC explants, and reduces the number of intestinal tumors in Apc(min/+) mice.
Our results, combined with previous studies, suggest that IL10, PSCA, IL1B, and SMAD7 are significantly correlated with CRC susceptibility in the Han Chinese population.
Genome-wide association studies (GWAS) in colorectal cancer (CRC) identified five regions near transforming growth factor β-related genes BMP4, GREM1, CDH1, SMAD7 and RPHN2.
The aim of this study was to investigate the influence of a SMAD7 gene polymorphism (rs2337107) on risk of CRC and clinicopathological features in an Iranian population.
Taken together, we propose that the associated CRC risk at 18q21.1 is due to four functional variants that regulate SMAD7 expression and potentially perturb a BMP negative feedback loop in TGFβ/BMP signaling pathways.
For SMAD7 gene, rs4939827 and rs4464148 are risk factors for CRC among Caucasian whereas rs12953717 could elevate the susceptibility to CRC in both Caucasian and Asian.
The two stage association studies showed that missense variant rs3764482 (c. 83C>T; p. rs3764482" genes_norm="4092">S28F) in the gene SMAD7 was consistently and significantly associated with CRC risk.
Eight miRSNPs (rs1804191, rs397768, rs41116 in APC; rs1137918, s227091, rs4585 in ATM; rs712, rs1137282, rs61764370 in KRAS; rs8674 in PARP1 and rs16950113 in SMAD7) were tested for their association with CRC risk in a case-control study (1111 cases and 1469 healthy controls).
We found that two of the loci most strongly linked with colorectal cancer (CRC) risk, 8q24 (upstream of MYC) and 18q21 (in the intron of SMAD7), as well as 20q13 (in the intron of LAMA5), are tightly associated with the prognosis of rectal cancer patients.
As partial validation of our approach, a known CRC risk variant in SMAD7 (in both the TGF-β and WNT pathways: rs11874392) was associated with CRC risk in our data.
When assessed by a priori defined functional pathways, tumor growth factor β (TGFβ) signaling was associated with CRC risk (<i>P</i> ≤ 0.001), with most statistically significant genes being <i>SMAD7 (P<sub>BH</sub></i> = 0.008) and <i>SMAD3 (P<sub>BH</sub></i> = 0.008), and 18 SNPs in the vitamin D receptor (VDR) binding sites (<i>P</i> = 0.036).