ABSTRACT
BACKGROUND: A functional blood supply is essential for tumor growth and proliferation. However, the mechanism of blood vessel recruitment to the tumor is still poorly understood. Ideally, a thorough molecular assessment of blood vessel cells would be critical in our comprehension of this process. Yet, to date, there is little known about the molecular makeup of the endothelial cells of tumor-associated blood vessels, due in part to the difficulty of isolating a pure population of endothelial cells from the heterogeneous tissue environment. METHODS: Here we describe the use of a recently developed technique, Expression Microdissection, to isolate endothelial cells from the tumor microenvironment. The methylation status of the dissected samples was evaluated for GSTP1 and RARbeta2 promoters via the QMS-PCR method. RESULTS: Comparing GSTP1 and RARbeta2 promoter methylation data, we show that 100% and 88% methylation is detected, respectively, in the tumor areas, both in epithelium and endothelium. Little to no methylation is observed in non-tumor tissue areas. CONCLUSION: We applied an accurate microdissection technique to isolate endothelial cells from tissues, enabling DNA analysis such as promoter methylation status. The observations suggest that epigenetic alterations may play a role in determining the phenotype of tumor-associated vasculature.
ABSTRACT
BACKGROUND: Gene expression can be silenced through the methylation of specific sites in the promoter region. This mechanism of gene silencing has an important role in the carcinogenesis of prostate and other cancers. Although tumor-associated stromal cells also exhibit changes in gene expression, promoter methylation has not been described in these cells. METHODS: Tumor epithelia, tumor-associated stroma and normal epithelia, and stroma adjacent to tumor tissues were isolated from whole-mount prostatectomy specimens (two per patient) of patients (n = 5) with localized prostate cancer and from normal epithelia and stroma from benign prostate hyperplasia specimens (two per patient) from men (n = 5) without prostate cancer by using laser capture microdissection or expression microdissection. The methylation status of three genes important in prostate carcinogenesis, GSTP1, RARbeta2, and CD44, were evaluated using quantitative methylation-sensitive polymerase chain reaction. RESULTS: GSTP1 and RARbeta2 were methylated in the tumor epithelium of all five prostate cancer patients and in the tumor-associated stroma in four of the five patients. CD44 was methylated in the tumor epithelium from four of the five patients but not in the tumor stroma. GSTP1 and RARbeta2 were methylated in normal epithelium of two and four patients, respectively, and in normal stroma of one and two patients, respectively, that were isolated from regions adjacent to the tumors and may have resulted from a tumor-field effect; CD44 methylation was not observed in normal epithelium or stroma. In contrast, normal epithelia and stroma from benign prostate hyperplasia specimens showed no promoter methylation in GSTP1, RARbeta2, or CD44. CONCLUSIONS: The observation of promoter methylation in the non-neoplastic cells of the prostate tumor microenvironment may advance our understanding of prostate cancer development and progression and lead to new diagnostic and prognostic markers and therapeutic targets.
