Panoply™ Human SIRPA Knockdown Stable Cell Line

The function of signal regulatory protein α (SIRPA) has been well studied in macrophages and dendritic cells, but relatively little research has been conducted in tumors. Notably, SIRPA is upregulated in osteosarcoma tissues, particularly metastatic tissues, and is associated with poor clinical outcomes. Knockdown of SIRPA reduces the stability of specific protein 1 (SP1) and inhibits arginine uptake, thereby suppressing osteosarcoma cell migration. Importantly, SIRPA protects SP1 from proteasome degradation by activating extracellular signal-regulated kinase (ERK) to phosphorylate threonine 278 (Thr278) of SP1. Furthermore, SP1 promotes osteosarcoma cell migration by binding to the promoter of solute carrier family 7 member 3 (SLC7A3), increasing SLC7A3 expression and enhancing arginine uptake. More interestingly, arginine promotes SP1 stability in an ERK-independent manner, forming an "SP1 stabilization circle." Treatment with a combination of anti-SIRPA antibody and arginase (arginase blocks this loop) inhibited tumor metastasis in mice with xenograft tumors formed from SIRPA-overexpressing cells. In summary, these studies demonstrate that SIRPA upregulation promotes osteosarcoma metastasis through the SP1 stabilization circle and SLC7A3-mediated arginine uptake, potentially representing a novel therapeutic target for osteosarcoma.

To investigate the function of SIRPA in human osteosarcoma cells, researchers constructed SIRPA knockdown 143B and U2-OS cell lines (Figure 1A and B). Subsequently, while SIRPA knockdown had a slight effect on cell proliferation (Figure 1C) and colony formation (Figure 1D), it significantly reduced the migration ability of osteosarcoma cells (Figure 1E and F). Furthermore, in a mouse 143B-Luc xenograft model, the number and size of lung metastatic nodules were significantly reduced in the SIRPA knockdown group compared to the negative control group (NC) (Figure 1G). In addition, researchers assessed the metastatic potential of 143B-Luc osteosarcoma cells by labeling them with PKH26, and the results showed that SIRPA knockdown reduced the metastatic ability of 143B cells (Figure 1H and I). Importantly, these results indicate that SIRPA promotes the metastasis of osteosarcoma cells both in vitro and in vivo.

Figure 1. Knockdown of SIRPA impairs 143B cell metastasis in vitro and in vivo. (Wang P, et al., 2023)