Inhibition of ERK1/2 in cancer-associated pancreatic stellate cells suppresses cancer-stromal interaction and metastasis

Background: Extracellular signal-regulated kinases (ERKs) have been related to multiple cancers, including breast Cancer, hepatocellular Cancer, lung Cancer and colorectal Cancer. ERK1/2 inhibitor can suppress growth of KRAS-mutant pancreatic tumors by targeting Cancer cell. However, no studies have shown the expression of ERK1/2 on pancreatic stromal and its effect on pancreatic cancer-stromal interaction.

Methods: Immunohistochemistry and western blotting were performed to detect the expression of p-ERK1/2 in pancreatic tissues and cells. Cell viability assay was used to study IC50 of ERK Inhibitor on pancreatic Cancer cells (PCCs) and primary cancer-associated pancreatic stellate cells (PSCs). Transwell migration, invasion, cell viability assay, senescence β-galactosidase staining were performed to determine the effect of ERK Inhibitor on PCCs and PSCs in vitro and in vivo. The expression of key factors involved in Autophagy and epithelial-to-mesenchymal transition (EMT) process were evaluated by western blotting. The expression of key factors related to cell invasiveness and malignancy were confirmed by qRT-PCR. Co-transplantation of PCC Organoid and PSC using a splenic xenograft mouse model was used to evaluated combined treatment of ERK Inhibitor and Autophagy Inhibitor.

Results: Immunohistochemical staining in pancreatic tumor samples and transgenetic mice detected p-ERK1/2 expression in both Cancer cells and stromal cells. In pancreatic tissues, p-ERK1/2 was strongly expressed in cancer-associated PSCs compared with Cancer cells and normal PSCs. PSCs were also significantly more sensitive to ERK1/2 inhibitor treatment. Inhibition of ERK1/2 suppressed EMT transition in HMPCCs, upregulated cellular senescence markers, activated Autophagy in cancer-associated PSCs; and suppressed cancer-stromal interaction, which enhanced invasiveness and viability of Cancer cells. We also found that chloroquine, an Autophagy Inhibitor, suppressed ERK inhibition-induced Autophagy and promoted PSC cellular senescence, leading to significantly decreased cell proliferation. The combination of an ERK Inhibitor and Autophagy Inhibitor suppressed liver metastasis in a splenic pancreatic Cancer organoid xenograft mouse model.

Conclusions: These data indicate that inhibition of ERK1/2 in cancer-associated pancreatic stellate cells suppresses cancer-stromal interaction and metastasis.