Panoply™ Human STAT3 Knockdown Stable Cell Line

In hepatocellular carcinoma (HCC), Signal Transducer and Activator of Transcription 3 (STAT3) is hyperactivated, a state closely linked to tumorigenesis, tumor progression, and immune escape. Inhibiting STAT3 can remodel the tumor immune microenvironment, though the underlying mechanisms remain incompletely understood. Research has shown that STAT3 inhibition induces immunogenic cell death (ICD) in HCC cells by promoting the translocation of the "eat-me" signal molecule calreticulin to the cell surface and significantly downregulating the expression of the "don't-eat-me" signal molecule CD47 (a leukocyte surface antigen). Furthermore, STAT3 inhibition promotes dendritic cell (DC) activation and enhances the recognition and phagocytosis of HCC cells by macrophages. Additionally, inhibiting STAT3 blocks the expression of key glycolytic enzymes, thereby facilitating ICD in HCC cells. Interestingly, STAT3 directly regulates the transcription of CD47 and solute carrier family 2 member 1 (SLC2A1, also known as GLUT1). In mouse models of subcutaneous and orthotopic xenografts, the STAT3 inhibitor Napabucasin not only suppressed tumor growth but also induced the expression of calreticulin and protein disulfide isomerase family A member 3 (PDIA3, also known as ERp57) while suppressing CD47 and GLUT1 expression. Notably, STAT3-targeted therapy induced an anti-tumor immune memory response. These findings reveal a novel mechanism by which targeting STAT3 induces ICD in HCC cells and confirm STAT3 as a potential therapeutic target for HCC through the remodeling of the tumor immune microenvironment.

To investigate whether STAT3 is involved in the process of immunogenic cell death (ICD) in hepatocellular carcinoma (HCC) cells, researchers generated STAT3-knockdown cells; the results showed that HCC cell proliferation was inhibited and apoptosis increased. Furthermore, we confirmed that, compared with wild-type STAT3 (STAT3-WT), the STAT3 mutant vector (STAT3-Y705F) failed to restore STAT3 phosphorylation levels in Huh7 and HepG2.2.15 cells. Alongside increased ATP release, researchers observed significantly elevated surface expression of calreticulin, ERp57, HSP70, and HSP90 in STAT3-knockdown Huh7 and HepG2.2.15 cells-an effect that could not be reversed by STAT3-Y705F reconstitution (Figure 1A–E). Additionally, they co-cultured immature dendritic cells (DCs)-derived from the peripheral blood mononuclear cells (PBMCs) of healthy volunteers-with Huh7 and HepG2.2.15 cells that had either been treated with STAT3-shRNA or left untreated. After 48 hours, DCs co-cultured with STAT3-knockdown Huh7 or HepG2.2.15 cells exhibited higher surface expression levels of CD80 and CD86 compared to those co-cultured with control HCC cells (Figure 1F, G). These data indicate that STAT3 knockdown induces ICD in HCC cells and promotes DC activation.

Figure 1. Knockdown of STAT3 expression induces membrane translocation of ICD‐related molecules in HCC cells and promotes DC activation. (Li Y, et al., 2022)