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Abstract
Colorectal Cancer (CRC) is the third most common cancer worldwide so it is considered a major health problem. One of the most important pathways that involved in the control of cell proliferation, differentiation, migration and apoptosis is the TGF-Ý signaling pathway. Therefore, in CRC, many alterations appear in this pathway whatever in its ligands, receptors or in downstream transcription factors (SMAD family). RNA extraction and cDNA synthesis for each specimen in this work was processed and gene expression of SMAD4 and SMAD7 was evaluated. It was found that, SMAD4 gene expression level decreased in more than 23% of CRC patients (P < 0.01), while the expression level of SMAD7 gene increased in more than 35% (P < 0.01). In the metastatic cases, the expression level of SMAD4 gene decreased while the expression level of SMAD7 gene increased in more than 10% of CRC patients (P=0.01).To determine 18q chromosome deletion and allelic loss of SMAD4 gene(LOH), another part of each sample underwent genomic DNA extraction and amplification of two pairs of primers, one lie upstream of SMAD4 gene and the second lie the downstream region. The association between SMAD4 gene expression and CRC and its metastasis doesn{u2019}t mean that the SMAD4 gene deletion developed