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P1.02 - Poster Session 1 - Novel Cancer Genes and Pathways (ID 144)
- Event: WCLC 2013
- Type: Poster Session
- Track: Biology
- Presentations: 1
- Coordinates: 10/28/2013, 09:30 - 16:30, Exhibit Hall, Ground Level
P1.02-011 - RANK and RANK Ligand (RANKL) expression in primary human lung cancer (ID 870)
09:30 - 16:30 | Author(s): W.C. Dougal
RANKL is an essential mediator of osteoclast differentiation, function, and survival. Tumor cells can induce RANKL expression in the bone stroma, causing activation of osteoclasts, leading to bone breakdown and subsequent tumor growth. In mouse models of lung cancer bone metastasis, RANKL inhibition by OPG-Fc can prevent tumor-induced osteolysis, decrease skeletal tumor burden, and increase survival. The effects on disease progression and survival may be explained by direct effects on the tumor in addition to indirect effects via osteoclast suppression. Recent clinical studies in patients with advanced cancer, including lung cancer, showed that RANKL inhibition with denosumab reduced the risk of skeletal-related events. Denosumab also improved overall survival compared with zoledronic acid in patients with lung cancer. In addition to the well-defined expression in the bone compartment, RANK and RANKL expression has also been demonstrated in human lung cancer cell lines and the functional expression of RANK has been confirmed through the demonstration of RANKL-dependent responses. The current study assessed the expression of human RANK and RANKL in human primary lung cancer samples in order to gain a potential mechanistic understanding of these clinical observations.
RANK and RANKL expression was analyzed in a panel of human primary lung cancer samples. Specific, monoclonal antibodies against human RANK (N-1H8, N-2B10; Amgen) and human RANKL (M366, AMG161; Amgen) were validated and optimized for immunohistochemistry (IHC) and used for expression analysis. mRNA was quantified using RT-PCR. Expression of RANK and RANKL was determined by IHC in the carcinoma element, tumor adjacent normal lung, and infiltrating cells. Incidence was scored as a positive IHC signal (any intensity). The specificity of the antibodies was substantiated by concordant signals observed using multiple independent analyses, including IHC, flow cytometry, and Western blots of positive and negative control cells and xenograft samples.
Analysis of primary human lung cancer using IHC demonstrated RANK staining in the tumor epithelium of 9/16 (56%) non-small cell lung cancer (NSCLC) adenocarcinomas, 9/26 (34%) squamous cell carcinomas (SCC), and 5/10 (50%) small cell carcinomas (SCLC). RANKL staining was observed in the tumor epithelium of 12/16 (75%) adenocarcinomas, 5/26 (19%) SCC, and 3/10 (30%) SCLC. RANK and RANKL were also observed in infiltrating macrophages and lymphocytes, respectively, within the majority of tumors examined. In addition, RANKL expression was frequently observed in type II pneumocytes of the alveoli, Clara cells of the terminal bronchioles, and in lymphocytes within the bronchus-associated lymphoid tissue (BALT); RANK expression was observed in alveolar macrophages proximal to the tumor and in M-cells of BALT. Analysis of mRNA levels indicated significantly greater levels of both RANK and RANKL in primary human NSCLC as compared with normal lung.
RANK and RANKL expression was observed in the epithelial carcinoma element in human primary lung cancer. Whether the expression of RANK and/or RANKL on lung cancer will directly contribute to tumor progression and/or metastatic activity and whether RANKL inhibition has a potential direct anti-tumor effect in lung cancer beyond the well established bone-targeted mechanism remains an objective of ongoing research.