Aalinkeel et al. (1) have recently reported that gene expression of angiogenic factors correlates with metastatic potential of prostate cancer cells. The rationale for the study of Aalinkeel et al. is that a variety of growth factors, among them interleukin-8 (il-8), can induce angiogenesis (2). Further, parathyroid hormone related peptide (PTHrP) acts to induce il-8 production in prostate cancer cells via an intracrine pathway independent of its classical nuclear localization sequence. This novel pathway could mediate the effects of PTHrP on the progression of prostate cancer (3). We measured il-8 in the serum of 39 men with biopsy-proven prostate cancer. Their average age was 69 +/- 9 (mean +/- SD). Serum il-8 was measured with an automated chemiluminometric high sensitivity il-8 protein assay (Immulite, Diagnostic Products Corporation, Los Angeles, CA). We noted a significant elevation of il-8 in men with bone metastases, diagnosed by Tc-99 MDP bone scan, when compared to men with localized disease (Figure 1). Aalinkeel et al. found that il-8 was significantly higher in the more metastatic PC-3 and DU-145 prostate cancer cell lines, when compared to the poorly metastatic LnCAP cells. The results of our study of il-8 in men with prostate cancer support the findings of Aalinkeel et al. Therefore, new anti-angiogenic therapies targeting specific genes controlling prostate tumor metastasis may be of benefit in treating prostate cancer.