Given the task definition and input, reply with output. Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

To evaluate the expression of CXCR4, its ligand SDF-1, -catenin and E-cadherin throughout the local tumor microenvironment of prostate cancer.', "A total of 64 prostate cancer specimens, 24 frozen and 40 paraffin-embedded sections, were obtained from patients treated with radical prostatectomy for clinically localized cancer. Real-time RT-PCR was used for mRNA quantification of CXCR4 and SDF-1 in the tumor center (T), tumor front (F) and distant peritumoral tissue (D). Immunohistochemical analysis was used to investigate the expression patterns of CXCR4, E-cadherin and -catenin. Clinical records of these patients were studied for follow-up data, and the prognostic value of these molecules' expression was statistically assessed.", 'CXCR4 mRNA and protein were significantly increased at the tumor front as compared to distant tissue or tumor center. In comparison, SDF-1 mRNA level gradually increased from the tumor center to the distant peritumoral tissue. High CXCR4 at the tumor front was associated with high Gleason score. Low SDF-1 at the tumor front was associated with locally advanced cancer and disease recurrence. Moreover, high CXCR4 staining at the tumor front and increased cytosolic E-cadherin expression in the same location was associated with locally advanced disease.
Is cXCR4 highly expressed at the tumor front but not in the center of prostate cancers?