Role of neuropilin-2 in the immune system

Neuropilins (NRPs) are single transmembrane receptors with short cytoplasmic tails and are dependent on receptors like VEGF receptors or Plexins for signal transduction. NRPs are known to be important in angiogenesis, lymphangiogenesis, and axon guidance. The Neuropilin-family consists of two members, Neuropilin-1 (NRP1) and Neuropilin-2 (NRP2). They are up to 44 % homologous and conserved in all vertebrates. High levels of NRP2 are found on immune cells. Current research is very limited regarding the functions of NRP2 on these cells. Recent evidence suggests that NRP2 is important for migration, antigen presentation, phagocytosis and cell-cell contact within the immune system. Additionally, posttranslational NRP2 modifications like polysialylation are crucial for the function of some immune cells. This review is an overview about expression and functions of NRP2 in the immune system.

[The metastatic niche. Mechanisms and prognostic implications]

Disseminated tumor cells require a special microenvironment to form metastases. This metastatic niche is organ specific and forms prior to the establishment of visible metastases. The niche is characterized by vascular remodeling and bone marrow-derived cells which have migrated into it. Studies by other groups and our own results have already shown that intranodal lymphangiogenesis is an important prerequisite for regional lymph node metastases in rectal cancer patients, and can be used as a prognostic marker for progression-free survival. Niche cells such as endothelia secrete factors that attract tumor and bone marrow-derived cells. CXCL12 is one of these factors. CXCL12 activates the CXCR4 chemokine axis and induces migration along its gradient. Several factors, such as hypoxia, have been described to regulate CXCR4 function and surface expression on tumor cells. Low molecular weight agents have been used to block CXCR4 activation. This review focuses on the function and regulation of CXCR4 and its ligand CXCL12 in metastases formation. It also discusses potential options for therapeutic blockage.

Neuropilin-2 and its ligand VEGF-C predict treatment response after transurethral resection and radiochemotherapy in bladder cancer patients

The standard treatment for invasive bladder cancer is radical cystectomy. In selected patients, bladder-sparing therapy can be performed by transurethral resection (TURBT) and radio-chemotherapy (RCT) or radiotherapy (RT). Our published in vitro data suggest that the Neuropilin-2 (NRP2)/VEGF-C axis plays a role in therapy resistance. Therefore, we studied the prognostic impact of NRP2 and VEGF-C in 247 bladder cancer patients (cN0M0) treated with TURBT and RCT (n = 198) or RT (n = 49) and a follow-up time up to 15 years. A tissue microarray was analyzed by immunohistochemistry. NRP2 expression emerged as a prognostic factor in overall survival (OS; HR: 3.42; 95% CI: 1.48 - 7.86; p = 0.004) and was associated with a 3.85-fold increased risk of an early cancer specific death (95% CI: 0.91 - 16.24; p = 0.066) in multivariate analyses. Cancer specific survival (CSS) dropped from 166 months to 85 months when NRP2 was highly expressed (p = 0.037). Patients with high VEGF-C expression have a 2.29-fold increased risk of shorter CSS (95% CI: 1.03-5.35; p = 0.043) in univariate analysis. CSS dropped from 170 months to 88 months in the case of high VEGF-C expression (p = 0.041). Additionally, NRP2 and VEGF-C coexpression is a prognostic marker for OS in multivariate models (HR: 7.54; 95% CI: 1.57-36.23; p = 0.012). Stratification for muscle invasiveness (T1 vs. T2-T4) confirmed the prognostic role of NRP2 and NRP2/VEGF-C co-expression in patients with T2-T4 but also with high risk T1 disease. In conclusion, immunohistochemistry for NRP2 and VEGF-C has been determined to predict therapy outcome in bladder cancer patients prior to TURBT and RCT.

Impact of the adaptor protein GIPC1/Synectin on radioresistance and survival after irradiation of prostate cancer

PURPOSE

Studies have shown that GIPC1/Synectin is an essential adaptor protein of receptors that play an important role in cancer progression and therapy resistance. This is the first study to explore the role of GIPC1/Synectin in radioresistance of prostate cancer and as a possible predictive marker for outcome of primary radiation therapy.

MATERIALS AND METHODS

The effect of RNA interference-mediated GIPC1/Synectin depletion on clonogenic cell survival after irradiation with 0, 2, 4, or 6 Gy was assayed in two different GIPC1/Synectin-expressing human prostate cancer cell lines. The clinical outcome data of 358 men who underwent radiotherapy of prostate cancer with a curative intention were analyzed retrospectively. Uni- and multivariate analysis was performed of prostate-specific antigen recurrence-free survival and overall survival in correlation with protein expression in pretreatment biopsy specimens. Protein expression was evaluated by standard immunohistochemistry methods.

RESULTS

In cell culture experiments, no change was detected in radiosensitivity after depletion of GIPC1/Synectin in GIPC1/Synectin-expressing prostate cancer cell lines. Furthermore, there was no correlation between GIPC1/Synectin expression in human pretreatment biopsy samples and overall or biochemical recurrence-free survival after radiotherapy in a retrospective analysis of the study cohort.

CONCLUSION

Our results do not show a predictive or prognostic function of GIPC1/Synectin expression for the outcome of radiotherapy in prostate cancer. Furthermore, our in vitro results do not support a role of GIPC1 in the cellular radiation response. However, the role of GIPC1 in the progression of prostate cancer and its precursors should be subject to further research.

[GIPC: a new target for therapy in pancreatic adenocarcinoma?]

GIPC is highly expressed in human pancreatic adenocarcinoma and is a central protein for the stability of IGF-1R in pancreatic adenocarcinoma cell lines (15). The goal of this study was to prove the importance of GIPC in vivo and to evaluate possible therapeutic strategies that target this protein and its PDZ domain. In vivo effects of GIPC knockout were studied after lentiviral transduction of luciferase-expressing MiaPaCa2 pancreatic cancer cells with shRNA against GIPC; growth characteristics were monitored with bioluminiscence. Knockdown of GIPC led to a significant inhibition of pancreatic tumor cell growth in vivo in different mouse models. To test a possible therapeutic approach, the PDZ domain of GIPC was targeted by a short peptide composed of the amino acid sequence PSQSSSEA. This octapeptide was designed based on the C-terminal binding motif of GAIP. Targeting GIPC with this peptide inhibited the association between IGF-1R and GIPC. The subsequent downregulation of IGF-1R decreased proliferation in vitro and in vivo. In conclusion, our findings suggest that targeting GIPC and its PDZ domain-mediated interaction with the tyrosine kinase receptor IGF-1R could be a promising new treatment option for pancreatic cancer.