Receptor activator of nuclear factor kappaB (RANK) is expressed as a late event during malignant progression in Barrett's metaplasia

NF-κB signaling and crosstalk during carcinogenesis

Transcription factors (TFs) are proteins that control the transcription of genetic information from DNA to mRNA by binding to specific DNA sequences either on their own or with other proteins as a complex. TFs thus support or suppress the recruitment of the corresponding RNA polymerase. In general, TFs are classified by structure or function. The TF, Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), is expressed in all cell types and tissues. NF-κB signaling and crosstalk are involved in several steps of carcinogenesis including in sequences involving pathogenic stimulus, chronic inflammation, fibrosis, establishment of its remodeling to the precancerous niche (PCN) and transition of a normal cell to a cancer cell. Triggered by various inflammatory cytokines, NF-κB is activated along with other TFs with subsequent stimulation of cell proliferation and inhibition of apoptosis. The involvement of NF-κB in carcinogenesis provides an opportunity to develop anti-NF-κB therapies. The complexity of these interactions requires that we elucidate those aspects of NF-κB interactions that play a role in carcinogenesis, the sequence of events leading to cancer.

Expression of RANKL/RANK/OPG in primary and metastatic human prostate cancer as markers of disease stage and functional regulation

BACKGROUND

Late-stage prostate cancer patients are refractory to hormone therapy and exhibit a high propensity to develop skeletal metastasis. In this regard, the role of a novel cytokine system belonging to the tumor necrosis factor (TNF) family that is critical for osteoclastic osteolysis and that consists of receptor activator of NF-kappaB ligand (RANKL), its receptor (RANK), and decoy receptor osteoprotegerin (OPG) is of potential interest.

METHODS

Reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohistochemical analysis was used to examine the expression of RANKL, RANK, and OPG in human prostate cancer cell lines and in 89 archival samples of primary and metastatic (lymph nodes, skeleton) prostate cancer patients. Expression of these proteins was correlated with clinicopathogic parameters of the prostate cancer.

RESULTS

Expression of RANKL/RANK/OPG was low in normal but markedly higher in prostate cancer cell lines. Analysis of surgical biopsy specimens showed the expression of RANKL (31%), RANK (38%), and OPG (19%) in primary carcinoma. The expression frequency was significantly higher (RANKL [44%], RANK [49%], and OPG [73%]) in metastatic prostate cancer. OPG (83%) production was more common in skeletal as compared with lymph node metastases (46%), whereas the expression of RANKL expression was less discordant in bone (47%) and lymph node metastases (36%). The increased expression of RANKL/RANK/OPG observed correlated with Gleason score, TNM stage, androgen status, and serum prostate-specific antigen (PSA) levels in the prostate cancer patients.

CONCLUSIONS

Expression of RANKL/RANK/OPG correlates with more aggressive, advanced, metastatic prostate carcinoma to suggest their role as diagnostic, prognostic, and therapeutic targets for prostate cancer.

The molecular triad OPG/RANK/RANKL: involvement in the orchestration of pathophysiological bone remodeling

The past decade has seen an explosion in the field of bone biology. The area of bone biology over this period of time has been marked by a number of key discoveries that have opened up entirely new areas for investigation. The recent identification of the receptor activator of nuclear factor kappaB ligand (RANKL), its cognate receptor RANK, and its decoy receptor osteoprotegerin (OPG) has led to a new molecular perspective on osteoclast biology and bone homeostasis. Specifically, the interaction between RANKL and RANK has been shown to be required for osteoclast differentiation. The third protagonist, OPG, acts as a soluble receptor antagonist for RANKL that prevents it from binding to and activating RANK. Any dysregulation of their respective expression leads to pathological conditions such as bone tumor-associated osteolysis, immune disease, or cardiovascular pathology. In this context, the OPG/RANK/RANKL triad opens novel therapeutic areas in diseases characterized by excessive bone resorption. The present article is an update and extension of an earlier review published by Kwan Tat et al. [Kwan Tat S, Padrines M, Theoleyre S, Heymann D, Fortun Y. IL-6, RANKL, TNF-alpha/IL-1: interrelations in bone resorption pathophysiology. Cytokine Growth Factor Rev 2004;15:49-60].