Expression of the apoptotic calcium channel P2X7 in the glandular epithelium
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In the current study, expression of the apoptotic calcium channel receptor P2X7 and prostate-specific antigen (PSA) levels were studied in biopsy cores from 174 patients as well as 20 radical prostatectomy cases. In clinical biopsies, we have previously demonstrated that P2X1 and P2X2 calcium channel receptors are absent from normal prostate epithelium that does not progress to prostate cancer within 5 years. In cases that did progress to prostate cancer however, P2X1 and P2X2 labeling was observed in a stage-specific manner first in the nucleus, then the cytoplasm and finally on the apical epithelium, as prostate cancer developed. These markers were present up to 5 years before cancer was detectable by the usual morphological criteria (Gleason grading) as determined by H&E staining. In the current study, the apoptotic calcium channel receptor P2X7 yielded similar results to that of P2X1 and P2X2. Using radical prostatectomy tissue sections as well as biopsies, these changes in calcium channel metabolism were noted throughout the prostate, indicating a field effect. This finding suggests that the presence of a prostate tumor could be detected without the need for direct sampling of tumor tissue, leading to detection of false negative cases missed by H&E stain. The reliability of PSA levels as a prognostic indicator has been questioned in recent years. In the current study, PSA levels were correlated with the P2X7 labeling results. All patients who exhibited no P2X7 labeling had a prostatic serum antigen (PSA) level of <2. Patients who exhibited stage-specific P2X7 expression, and who later developed obvious prostate cancer as diagnosed by H&E stain, all had a PSA > 2. This finding suggests that increasing PSA may be an accurate indicator of cancer development.
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