cDNA microarray analysis of pigment epithelium-derived factor-regulated gene expression profile in prostate carcinoma cells

Stanniocalcin 2 (STC2): a universal tumour biomarker and a potential therapeutical target

Stanniocalcin 2 (STC2) is a glycoprotein which is expressed in a broad spectrum of tumour cells and tumour tissues derived from human breast, colorectum, stomach, esophagus, prostate, kidney, liver, bone, ovary, lung and so forth. The expression of STC2 is regulated at both transcriptional and post-transcriptional levels; particularly, STC2 is significantly stimulated under various stress conditions like ER stress, hypoxia and nutrient deprivation. Biologically, STC2 facilitates cells dealing with stress conditions and prevents apoptosis. Importantly, STC2 also promotes the development of acquired resistance to chemo- and radio- therapies. In addition, multiple groups have reported that STC2 overexpression promotes cell proliferation, migration and immune response. Therefore, the overexpression of STC2 is positively correlated with tumour growth, invasion, metastasis and patients' prognosis, highlighting its potential as a biomarker and a therapeutic target. This review focuses on discussing the regulation, biological functions and clinical importance of STC2 in human cancers. Future perspectives in this field will also be discussed.

Proapoptotic PEDF functional peptides inhibit prostate tumor growth--a mechanistic study

PEDF inhibits tumor growth via anti-angiogenic activity; however, the direct effect of PEDF on prostate carcinoma and its functional epitope as well as the underlying mechanism regulating the pathway from extracellular receptors to nuclear transcription factors has not been fully elucidated. This study investigates the ability and mechanism by which the functional PEDF peptides PEDF34 and PEDF44 suppress tumor growth. The results showed that death receptor pathway was activated by PEDF34 through up-regulation of FasL and activation of caspase-8 in both xenograft tumor tissues and PC-3 cells. FasL knockdown by siRNA or JNK-p inhibition attenuated apoptosis induced by PEDF34. NF-κB and PPARγ are crucial transcription factors for FasL expression. PEDF34 up-regulated PPARγ but did not affect NF-κB. PEDF34-induced up-regulation of FasL was abolished by siRNA-mediated PPARγ knockdown or using PPARγ inhibitor GW9662, whereas inhibition of NF-κB by the inhibitor PDTC or by siRNA had no effect. Furthermore, activation of JNK is necessary for PEDF34-induced up-regulation of FasL. PEDF34 has stronger hydropathicity and more interactions with laminin receptor than PEDF44. Blocking the laminin receptor abolished the up-regulation of FasL and PPARγ by PEDF34. Moreover, PEDF34 uses a similar mechanism to induce apoptosis in both endothelial and cancer cells. This study provides evidence that PEDF34, not PEDF44, serves as the proapoptotic epitope and exerts proapoptotic activity in both cancer and endothelial cells through activation of the extrinsic death receptor pathway. The dual anti-tumor and anti-angiogenic activities of PEDF34 suggest that it may be a promising agent for the treatment of prostate cancer.

Changes in the gene expression profile of A375 human melanoma cells induced by overexpression of multifunctional pigment epithelium-derived factor

Pigment epithelium-derived factor (PEDF) is a broad-spectrum angiogenesis inhibitor that displays potent antimetastatic activity in multiple tumor types. We have previously shown that PEDF prevents primary tumor growth and metastatic spread of human melanoma in mouse experimental models. Consistent with these observations, PEDF expression is lost at the late stages of melanoma progression, allowing melanoma cells to become angiogenic, migratory, and invasive. PEDF's ability to modify the interplay between the host and tumor tissues strongly supports its use as a therapeutic agent for the treatment of metastatic melanoma. However, transition to the clinic requires a more detailed knowledge of the molecular mechanisms underpinning PEDF's activity. In this study, we describe changes in the gene expression profile of A375 human melanoma cells induced by PEDF overexpression. PEDF modulated diverse categories of genes known to be involved in angiogenesis and migration. It downregulated cytokines such as interleukin-8 and extracellular matrix proteins such as collagen IV, while it upregulated fibronectin. Multiple transcripts previously described as contributing to the acquisition of malignant phenotype by melanoma were also diminished by PEDF overexpression, among which we validated galectin 3 and jagged 1. In addition, PEDF downregulated S100β and melanoma inhibitory activity, which are widely used in the pathological diagnosis of melanoma. Interestingly, PEDF increased the expression of melanophilin and decreased rab27A, which are relevant targets for melanosome transport; suggesting that PEDF could directly impinge on melanocytic lineage-specific processes. Our study identifies new molecular targets and signaling pathways that may potentially contribute to determine PEDF's ability to restrict the aggressiveness of A375 human melanoma cells.

Functional genomics of endothelial cells treated with anti-angiogenic or angiopreventive drugs

Angiogenesis is a highly regulated physiological process that has been studied in considerable detail given its importance in several chronic pathologies. Many endogenous factors and hormones intervene in the regulation of angiogensis and classical as well as targeted drugs have been developed for its control. Angiogenesis inhibition has come off the bench and entered into clinical application for cancer therapy, particularly for metastatic disease. While the clinical benefit is currently in terms of months, preclinical data suggest that novel drugs and drug combinations could lead to substantial improvement. The many targets of endogenous angiogenesis inhibitors reflect the complexity of the process; in contrast, current clinical therapies mainly target the vascular endothelial growth factor system. Cancer chemopreventive compounds can retard tumor insurgence and delay or prevent metastasis and many of these molecules hinder angiogenesis, a mechanism that we termed angioprevention. Angiopreventive drugs appear to prevalently act through the inhibition of the pro-inflammatory and anti-apoptotic player NFkappaB, thus contrasting inflammation dependent angiogenesis. Relatively little is known concerning the effects of these angiogenesis inhibitors on gene expression of endothelial cells, the main target of many of these molecules. Here we provide an exhaustive list of anti-angiogenic molecules, and summarize their effects, where known, on the transcriptome and functional genomics of endothelial cells. The regulation of specific genes can be crucial to preventive or therapeutic intervention. Further, novel targets might help to circumvent resistance to anti-angiogenic therapy. The studies we review are relevant not only to cancer but also to other chronic degenerative diseases involving endothelial cells, such as cardiovascular disorders, diabetes, rheumatoid arthritis and retinopaties, as well as vessel aging.

In vitro and in vivo biological activity of PEDF against a range of tumors

BACKGROUND

Pigment epithelium-derived factor (PEDF) is an emerging anti-cancer agent that targets both tumor tissue and its supporting vasculature. These direct and indirect effects of PEDF have been examined in vitro and in vivo for a range of malignancies.

OBJECTIVE

This review seeks to present PEDF as a potential anti-cancer agent with applications across multiple malignancies. We refer closely to experimental methodology whilst still highlighting the clinical significance of PEDF in cancer, drawing on biological findings in vitro and in vivo.

METHODS

A Pubmed database search was performed limiting the scope of this discussion paper mainly to PEDF's biological role in cancer, specifically lung, breast, prostatic, ovarian and pancreatic carcinomas, melanoma, glioma and osteosarcoma.

CONCLUSIONS

The biological roles of PEDF are diverse and multidimensional. As an anti-cancer agent, PEDF has great potential as a focused anti-neoplastic therapy against a variety of tumor types.