Abstract
CD24 is a heavily glycosylated glycosylphosphatidylinositol-anchored protein that is over-expressed in many different tumor types including lung cancer (NSCLC and SCLC), and has been shown to correlate with disease progression. Around 70% of the primary NSCLC was shown to overexpress CD24 and these patients tended to have higher risk of disease progression. CD24 plays a role in regulating cancer cell proliferation and tumor microenvironment interactions. The mechanism by which CD24 regulates cell survival and proliferation is not very well understood. It is better known that CD24 modulates cancer cell adhesion to the vasculature wall and cancer cell-platelet thrombi formation by its binding to P-selectin expressed on activated platelets and endothelial cells. The aim of this study was to investigate CD24 as a target for NSCLC therapy.
In order to assess CD24 as a target for NSCLC, we have investigated CD24 expression at the mRNA level in NSCLC tissues. CD24 mRNA was shown to be expressed both in squamous cell carcinoma, and in KRas and EGFR mutant adenocarcinoma tumors (123/168 samples). In order to investigate if CD24 has a critical role in cancer cell functions, we performed knock-down experiments using siRNA and several different NSCLC lines. CD24 siRNA treatment significantly affected NSCLC cancer cell line survival in vitro, by causing cell viability inhibition of 38 to 92% (depending on the cell line tested and the siRNA used), as measured by MTS assay. CD24 knockdown also caused inhibition of H358 colony formation in a soft agar anchorage-independent growth assay. Moreover, CD24 knock-down caused a 4-13 fold increase in apoptosis, as measured by propidium iodide staining. To further test the impact of CD24 knock-down on cell viability, we developed an in vitro 3D model system that is more reflective of the tumor microenvironment, containing basement membrane extract and lung cancer associated fibroblasts (CAFs) in co-culture with H358 lung tumor cells. CD24 knock-down significantly decreased cell viability and inhibited spheroid formation by H358 lung cancer cells grown alone or with CAFs. The migration of H358 cells in the scratch-wound assay was also significantly inhibited by CD24 knock down. Finally, using the H358 xenograft tumor model, we tested the effect of an anti-mouse CD24 antibody (SWA11). Treatment was initiated on the same day of cell implantation and repeated twice a week for 2 weeks. SWA11 significantly inhibited tumor formation.
Together, these results demonstrate that CD24 expression affects both the viability and motility of lung cancer cell lines and is a potential target for NSCLC treatment.
Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C189.
Citation Format: Luciana F. Macedo, Elizabeth Kaiser, Haiyan Jiang, Hillary Millar, E. Christine Pietsch, Fred Kaplan, Diana Wiley, Linda A. Snyder, Debbie Marshall. CD24 plays an important role on NSCLC cell functions relevant to tumor growth. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C189.
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