With the use of a slot blot assay, relatively low levels of MDR1 RNA were present in all four gastric carcinoma cell lines, while intermediate or high levels were present in most of the colorectal carcinoma cell lines.
While expression levels of Nrf2 and ABCB1 (P-gp) were markedly higher in both mRNA and protein levels in CRC biopsies (p < 0.01), Keap1 expression level was significantly lower in these samples (p < 0.05).
We analyzed the C3435T SNP in the MDR1 gene which is associated with altered cellular drug uptake in matched tumor and normal tissues of 45 patients suffering from colorectal carcinoma.
Using a case-control design, the association between the MDR1 intron 3 G-rs3789243-A polymorphism and the risk of colorectal carcinomas and adenomas in the Norwegian population was assessed in 167 carcinomas, 990 adenomas, and 400 controls.
This study suggests that low ABCB1 mRNA levels are an early event in CRC development and that the two polymorphisms affect ABCB1 mRNA levels whereas low NFKB1 mRNA levels occur later in carcinogenesis.
These findings implicate a role of ESR2 in the risk for developing CRC in women and suggest that HSD17B1, ABCB1, and SHBG genes may contribute to sex steroid-mediated effects on CRC development.
Therefore, we aimed to investigate the relationship between colorectal cancer and the functional common variants of ABCB1 (1236C > T; 2677G > T/A; 3435C > T).
The expression of cytochrome P450 2C19 (CYP2C19) and ATP-binding cassette, sub-family B member 1 (ABCB1) were significantly lower in the EREC group (6/15) compared to the NREC group (9/15) in colorectal cancer with metachronous liver metastasis and with serum CEA >5 ng/ml.
The ABCB1 polymorphisms might be a candidate pharmacogenomic factor to assess susceptibility and prognosis after oxaliplatin-based chemotherapy for CRC patients.
TAM can reverse the MDR of colorectal carcinoma in nude mice, which is independent of the expression of ER; however, no change was observed in the expressive level of mdr1 mRNA.