We have recently identified glucose-regulated protein-78 (GRP78) as a relevant molecular target expressed in metastatic tumors by fingerprinting the circulating repertoire of antibodies from cancer patients. Here we design and evaluate a ligand-receptor system based on the tumor cell membrane expression of GRP78. We show that GRP78 binding peptide motifs target tumor cells specifically in vivo and in human cancer specimens ex vivo. Moreover, synthetic chimeric peptides composed of GRP78 binding motifs fused to a programmed cell death-inducing sequence can suppress tumor growth in xenograft and isogenic mouse models of prostate and breast cancer. Together, these preclinical data validate GRP78 on the tumor cell surface as a functional molecular target that may prove useful for translation into clinical applications.

Recognition of molecular diversity in disease is required for the development of targeted therapies. We have developed a screening method based on phage display to select peptides recognized by the repertoire of circulating tumor-associated antibodies. Here we isolated peptides recognized by antibodies purified from the serum of prostate cancer patients. We identified a consensus motif, NX(S/T)DK(S/T), that bound selectively to circulating antibodies from cancer patients over control antibodies from blood donors. We validated this motif by showing that positive serum reactivity to the peptide was specifically linked to disease progression and to shorter survival in a large patient population. Moreover, we identified the corresponding protein eliciting the immune response. Finally, we showed a strong and specific positive correlation between serum reactivity to the tumor antigen, development of metastatic androgen-independent disease, and shorter overall survival. Exploiting the differential humoral response to cancer through such an approach may identify molecular markers and targets for diagnostic and therapeutic intervention.

In spite of prompt diagnosis and either orchiectomy or preservation of the affected testis, infertility remains a significant sequel to testicular torsion. The objective of this study was to evaluate the late endocrine profile, seminal parameters, and antisperm antibody levels after testicular torsion. We also analyzed the impact of orchiectomy or detorsion on the organ fate. Of 24 patients evaluated after testicular torsion, 15 were treated with orchiectomy (group 1) and 9 were treated with orchiopexy (group 2). All subjects were assessed by semen analysis, endocrine profile (levels of follicle-stimulating hormone, luteinizing hormone, and testosterone), and seminal antisperm antibody levels. A group of 20 proven fertile men was used as the control. Median ischemia time in group 1 (48 hours) was significantly higher than in group 2 (7 hours). Both groups demonstrated decreases in sperm count and morphology compared with controls. Group 1 showed a significantly higher motility than group 2 (P 5 .02). Group 1 also showed a significantly better morphology by World Health Organization and Kruger criteria than group 2 (P 5 .01). All patients presented endocrine profiles within the normal range, and no significant differences in antisperm antibody levels were detected between the groups. However, a trend for higher levels was found in patients treated for testicular torsion, regardless of the fate of the testis. Moreover, no significant correlation was found between antisperm antibody levels and age at torsion, ischemia time, seminal parameters, or treatment applied. In conclusion, we found that after torsion patients maintain late hormonal levels within the normal range. Testicular fate did not have any correlation with the formation of antisperm antibodies. Although sperm quality was preserved in most of the patients with the exception of sperm morphology, patients treated with orchiectomy presented better motility and morphology compared with the detorsion group. Further studies may clarify whether maintenance of a severely ischemic testicle may impair testicular function.

We show that a membrane-associated protease, aminopeptidase A (APA), is upregulated and enzymatically active in blood vessels of human tumors. To gain mechanistic insight, we evaluated angiogenesis in APA null mice. We found that, although these mice develop normally, they fail to mount the expected angiogenic response to hypoxia or growth factors. We then isolated peptide inhibitors of APA from a peptide library and show that they specifically bind to and inhibit APA, suppress migration and proliferation of endothelial cells, inhibit angiogenesis, and home to tumor blood vessels. Finally, we successfully treated tumor-bearing mice with APA binding peptides or anti-APA blocking monoclonal antibodies. These data show that APA is a regulator of blood vessel formation, and can serve as a functional vascular target.

No abstract