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Numerous studies have evaluated the association between CYP1A1 gene polymorphisms and hepatocellular carcinoma (HCC) risk. However, the specific association is still controversial. The aim of our study was to clarify the effects of CYP1A1 gene polymorphisms (3801 T＞C and A2455G) on HCC risk by conducting a meta-analysis. We conducted searches of the literature published in PubMed and EMBASE databases up to April 2014. We estimated the pooled odds ratio with its 95% confidence interval to assess the association using a fixed or random-effects model. Publication bias was investigated by the Begg funnel plot. Meta-analysis was performed using the STATA package version 12.0. Meta-analysis results showed no significant association between the CYP1A1 3801 T＞C polymorphism and HCC risk. In a subgroup analysis by nationality, we found a significant association between 3801 T＞C polymorphism and HCC risk in Asians (TT vs TC: OR = 0.77, 95%CI = 0.60-0.99). As for A2455G, the meta-analysis indicated no significant association between the CYP1A1 A2455G polymorphism and HCC risk. In conclusion, the 3801 T＞C polymorphism in the CYP1A1 gene may be related to increased risk of HCC in Asians. Conclusive evidence on the effects of the variants in HCC should be addressed in further studies.

Purpose: To determine factors which influence the sensitivity of human colorectal carcinoma cell lines to paclitaxel., Methods: The paclitaxel sensitivity of ten human colorectal carcinoma cell lines, and a panel of RKO colon carcinoma cell lines, isogenic except for p53 status, were studied. The inhibitory concentrations causing a 50% decrease in growth (IC50) were assayed after 3, 24, and 96 h after paclitaxel exposure. The doubling time (DT) and cell cycle parameters of cells were also measured. The expression of the multidrug resistance glycoprotein-1 (MDR-1), bcl-2 and bax was quantitatively assessed by immunoblotting., Results: Mean IC50 values at 24 and 96 h drug exposure were about 1.5 logs lower than the IC50 values at 3 h, regardless of the p53 status. No difference was found between the IC50 values of wild-type and mutant p53 cells, or among the RKO panel of cells. Correlation analysis showed that: (1) resistance was associated with longer DTs, but this was generally abated by a 96-h exposure; (2) with a 3-h exposure, the combination of MDR, bcl-2 and bax parameters with DT (DT + MDR + bcl-2 bax) best correlated with IC50 values (r = 0.77); (3) with a 96-h exposure, in spite of the generally decreased IC50 values, a combination of MDR-1, bcl-2 and bax parameters (MDR + bcl-2-bax) best correlated with the IC50 values (r = 0.71)., Conclusions: These results suggest that the exposure duration, DT, and expression of MDR-1, bcl-2 and bax each contribute to paclitaxel sensitivity of human colorectal carcinoma cells. In assessing paclitaxel drug resistance, multiple factors should always be considered. There may be a therapeutic window for taxanes in colon cancer by optimizing pharmacokinetics and modulating MDR-1 and bcl-2 resistance factors.

Background: The functional significance of c-myc overexpression in human colon carcinoma is unclear., Materials and Methods: Three human colon carcinoma cell lines, LS174T, SW1116 and SW48, were treated in vitro with phosphorothioate modified antisense oligonucleotides (ASO), complementary to the c-myc translation initiation site, or two control oligonucleotides. Growth was assayed by the methyl tetrazolium (MTT) assay and colony formation. C-myc, retinoblastoma (Rb), carcinoembryonic antigen (CEA), and alkaline phosphatase (AP) expression was assessed by immunoblotting., Results: The ASO specifically inhibited growth of all three human colon carcinoma cell lines. Further studies were conducted on LS174T because growth inhibition was associated with a more differentiated morphology. In LS174T cells, ASO caused a dose dependent decrease in c-myc and Rb protein expression, but an increase in CEA and AP expression., Conclusions: The growth of human colon carcinoma cells is dependent on c-myc expression, and the inhibition of c-myc expression in LS174T is associated with a more differentiated phenotype.

The activated c-myc allele in Burkitt's lymphoma tumor cells is associated with a clustering of somatic mutations within intron I near the exon I boundary. We have identified several discrete protein binding sites within this region of c-myc intron I designated as myc intron factor-1 (MIF-1), MIF-2, and MIF-3. In addition to our previous characterization of a 20-nucleotide binding site for MIF-1, we now have identified adjacent 20-nucleotide and 34-nucleotide binding sites for MIF-2 and MIF-3, respectively. All three elements are protected from exonuclease digestion by nuclear protein extracts, and each gives rise to a distinct migration pattern on mobility shift assays. In addition, MIF-1, 2, and 3 share a 5-nucleotide (TTATG) internal sequence, which may account for cross-competition of these binding sites in the exonuclease protection experiment. Deletion mutant analyses showed that selective removal of the MIF-3 binding site alone was sufficient to enhance chloramphenicol acetyltransferase reporter activity similar to that observed with larger deletions of myc intron I. We have demonstrated that somatic mutations in activated c-myc alleles are frequently clustered in discrete domains that define protein recognition sequences.