Panoply™ Human EGFR Over-expressing Stable Cell Line

Cetuximab resistance is a major obstacle to the treatment of epidermal growth factor receptor (EGFR) overexpressing cancers, including triple-negative breast cancer (TNBC). MicroRNA (miRNA)-155-5p is highly expressed in TNBC cells. Therefore, researchers investigated whether downregulating miR-155-5p could enhance the antitumor effect of cetuximab in TNBC cells. First, they constructed EGFR-overexpressing cell lines (MDA-MB-231 and MDA-MB-468). The inhibitory effect of cetuximab on the proliferation and migration of EGFR-overexpressing MDA-MB-468 cells was enhanced after transfection with a miR-155-5p antagonist, while miR-155-5p knockdown enhanced the pro-apoptotic effect of cetuximab on EGFR-overexpressing MDA-MB-468 cells. Furthermore, luciferase reporter gene assays showed that gasdermin E (GSDME) is a direct binding target of miR-155-5p. Cetuximab in combination with a miR-155-5p antagonist promotes pyroptosis in EGFR-overexpressing MDA-MB-468 cells by upregulating GSDME-N and cleaved caspase-1. In vivo experiments confirmed that downregulation of miR-155-5p enhanced the antitumor effect of cetuximab in MDA-MB-468 xenograft models and EGFR-overexpressing TNBC cells, through the induction of apoptosis and pyroptosis. Therefore, cetuximab combined with a miR-155-5p antagonist may be a novel therapeutic strategy for TNBC.

Here, researchers used flow cytometry to detect the cytotoxic effects of cetuximab combined with a miR-155-5p antagonist on EGFR-overexpressing MDA-MB-468 cells. The results showed that cell death occurred in apoptosis (quadrants Q2 and Q3), necrosis, or pyroptosis (quadrants Q1 and Q2). As shown in Figures 1A and 1B, 10 nM cetuximab significantly induced apoptosis in EGFR-overexpressing MDA-MB-468 cells, while downregulation of miR-155-5p significantly enhanced the induction of necrosis or pyroptosis in EGFR-overexpressing TNBC cells. Furthermore, compared to the cetuximab monotherapy group, the expression of Bax and cleaved caspase-3 was increased in EGFR-overexpressing MDA-MB-468 cells treated with cetuximab combined with a miR-155-5p antagonist. However, compared with the cetuximab monotherapy group, the cetuximab plus miR-155-5p treatment group showed decreased Bcl-2 levels in EGFR-overexpressing MDA-MB-468 cells (Figures 1C-F). These data suggest that downregulation of miR-155-5p enhances the cytotoxic effect of cetuximab on EGFR-overexpressing MDA-MB-468 cells.

Figure 1. Downregulation of miR-155-5p enhances the pro-apoptotic effect of cetuximab in TNBC cells. (Xu W, et al., 2021)