[Show abstract][Hide abstract] ABSTRACT: The cysteinyl leukotrienes receptors (CysLTRs) are implicated in many different pathological conditions, such as inflammation and cancer. We have previously shown that colon cancer patients with high CysLT(1)R and low CysLT(2)R expression demonstrate poor prognosis. Therefore, we wanted to investigate ways for the transcriptional regulation of CysLT(2)R, which still remains to be poorly understood.
We investigated the potential role of the anti-tumorigenic interferon α (IFN-α) and the mitogenic epidermal growth factor (EGF) on CysLT(2)R regulation using non-transformed intestinal epithelial cell lines and colon cancer cells to elucidate the effects on the CysLT(2)R expression and regulation. This was done using Western blot, qPCR, luciferase reporter assay and a colon cancer patient array. We found a binding site for the transcription factor IRF-7 in the putative promoter region of CysLT(2)R. This site was involved in the IFN-α induced activity of the CysLT(2)R luciferase reporter assay. In addition, IFN-α induced the activity of the differentiation marker alkaline phosphatase along with the expression of mucin-2, which protects the epithelial layer from damage. Interestingly, EGF suppressed both the expression and promoter activity of the CysLT(2)R. E-boxes present in the CysLT(2)R putative promoter region were involved in the suppressing effect. CysLT(2)R signaling was able to suppress cell migration that was induced by EGF signaling.
The patient array showed that aggressive tumors generally expressed less IFN-α receptor and more EGFR. Interestingly, there was a negative correlation between CysLT(2)R and EGFR expression. Our data strengthens the idea that there is a protective role against tumor progression for CysLT(2)R and that it highlights new possibilities to regulate the CysLT(2)R.
[Show abstract][Hide abstract] ABSTRACT: The fact that breast cancer patients with local or distal dissemination exhibit decreased survival, promotes a search for novel mechanisms to suppress such tumor progression. Here, we have determined the expression of proinflammatory cysteinyl leukotriene receptors (CysLTRs) in breast tumor tissue and their signaling effect on breast cancer cell functions related to tumor progression. Patients with breast tumors characterized by high CysLT(1)R and low CysLT(2)R expression levels exhibited increased risk of cancer-induced death in univariate analysis for both the total patient group (hazard ratio [HR] = 2.88, 95% confidence interval [CI] = 1.11-7.41), as well as patients with large (>20 mm) tumors (HR = 5.08, 95% CI = 1.39-18.5). Multivariate analysis revealed that patients with large tumors exhibiting high CysLT(1)R and low CysLT(2)R expression levels had a significantly reduced survival, also when adjusted for established prognostic parameters (HR = 7.51, 95% CI = 1.83-30.8). In patients with large (>20 mm) tumors, elevated CysLT(2)R expression predicted an improved 5-year survival (log-rank test p = 0.04). Surprisingly, for longer time periods, this prognostic value was lost. This disappearance coincided with the termination of hormonal treatment. Tamoxifen preserved and even induced transcription of CysLT(2)R, but not CysLT(1)R, in estrogene receptor-positive MCF-7 breast cancer cells. This elevated CysLT(2)R expression decreased, even below the level of untreated cells, when tamoxifen was withdrawn. CysLT(2)R signaling reduced MCF-7 cell migration, but had no effect on either proliferation or apoptosis. Our data indicate that low CysLT(1)R together with high CysLT(2)R expression levels might be useful parameters in prognostication and treatment stratification of breast cancer patients.
Full-text · Article · Jul 2011 · International Journal of Cancer