Organ-wide telomeric status in diseased and disease-free prostatic tissues

Abstract

Background: Telomere attrition occurs early in the development of prostatic adenocarcinoma. However, little is known about either telomere status in benign prostatic hyperplasia (BPH), or the spatial and organ-wide distribution of potential telomere aberrations throughout all areas of prostatic glands affected by cancer or BPH.

Methods: Slot blot titration assay was used to determine telomere DNA content (TC), a proxy for telomere length, in macrodissected tissue consisting of 54 normal samples from 5 disease-free prostates, 128 BPH samples from 4 non-cancerous prostates, and 45 tumor, 73 BPH, and 4 prostatic intraepithelial neoplasia (PIN) samples from 5 cancerous prostates.

Results: Compared to TC in normal prostate samples (n = 54; TC mean = 0.98), tumor samples displayed telomere attrition (n = 45; TC mean = 0.67). TC in PIN samples was similar to tumors. TC in BPH samples from cancerous prostates was similar to TC in tumors and also displayed telomere shortening (n = 73; TC mean = 0.76), whereas BPH samples from non-cancerous prostates displayed longer telomeres (n = 128; TC mean = 1.06). In prostates affected by adenocarcinoma, areas of potential telomere attrition occurred in histologically normal tissues through the entire gland. However, three-dimensional zoning revealed a pattern of increasing TC as a function of distance from the primary (index) tumor.

Conclusions: Spatial distributions of TC in prostate specimens indicate a complex "field effect" with varying contributions from both cancer and BPH. The observation that telomere length variations occur in fields of histologically normal tissues surrounding the tumor is of clinical importance, as it may have implications for the diagnosis and focal therapy of prostate cancer.

Fig. 1

TC distributions in disease-free prostates and in prostate affected by adenocarcinoma, HGPIN and BPH. The number of cases and tissue samples is indicated. TC is expressed as a ratio of TC in a placental DNA control. Individual data points are shown as small black squares; vertical columns of data points represent individual cases. The boxes represent group medians (line across middle) and quartiles (25th and 75th percentiles) at its ends. Lines above and below boxes indicate 10th and 90th percentiles, respectively. The gray shaded area indicates 95% of TC measurements in the disease-free normals (0.80–1.25). p values indicate statistical significance between indicated groups, as calculated by parametric analysis of variance (ANOVA), generalized estimating equations (GEE), and repeated measure ANOVA (rmANOVA).

Fig. 2

Organ-wide (from apex to base) spatial distribution of TC in transversal sections of a representative prostate affected by adenocarcinoma. The dark shaded areas represent cancerous tissues (indicated by thick arrows); the circumscribed areas represent excised tissues for TC analysis. Relative TC ratios are color coded with red designating low and yellow high TC as indicated by the heat map. Note: Outlier TC measurement (non-colored excision located in upper right quadrant of second section from top) was omitted.

Fig. 3

Relative TC of zones located at increasing distances from the primary (index) tumor zone (bolded T) for 5 prostates affected by adenocarcinoma. N denotes TC in disease-free normal tissues. Bars denote average TC +/− standard deviation for an average number of tissue samples per zone of 6 (for tumors) and 10 (for tumor adjacent). # denotes statistically significant difference (p<0.05) from disease-free normal tissues (N); * denotes statistically significant difference by student’s t-test (p<0.05) from zone T containing the tumor; † in tumors 1 and 5 denotes the presence of an additional cancerous focus in that zone; ** in tumor 5 denotes statistically significant difference by student’s t-test (p<0.05) from neighboring zone D. Note: The cancerous area in tumor 1 contained only one sample.