Rac/Cdc42 inhibitors target pancreatic cancer cells and macrophages in the tumor microenvironment

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest forms of cancer, with a distinct extracellular matrix and immunosuppressive tumor microenvironment. Therefore, there is a critical need for therapies that simultaneously target metastatic cancer cells and immunosuppressive cells such as tumor associated macrophages (TAMS) that promote pancreatic cancer progression. Ras-activated homologous GTPases Rac and Cdc42 are ideal targets for pancreatic cancer therapy because they regulate cell migration/invasion, cell polarity/morphology, and cell viability/survival in cancer cells and immune cells, mainly through activation of their common downstream effector p21-activated kinase (PAK) via autophosphorylation. Rac, Cdc42, and PAK are poor prognostic factors in PDAC. Accordingly, we found phospho-PAK levels to be elevated in invasive PDAC from Puerto Rican patient tissue. The potential of the dual Rac/Cdc42 inhibitors MBQ-167 and MBQ-168 were tested in human and mouse PDAC cells or macrophages by pulldown assays for Rac and Cdc42 activation, MTT assays for cell viability, wound-healing assays for cell migration, phagocytosis, as well as co-culture assays with PDAC cells and macrophages. Results show that Rac/Cdc42 inhibitors significantly reduce active Rac and Cdc42 in pancreatic and macrophage cells. Both MBQ-167 and MBQ-168 reduced pancreatic cancer cell viability with higher efficacy than macrophage viability, and inhibited morphology and migration of both cell types. In Transwell co-culture, MBQ-167 and MBQ 168 decreased pancreatic cancer cell migration and reduced inflammatory mediators such as Interleukin-6 (IL-6), Chinase-3-like protein 1 (CHI3L1) and S100A8/A9 (calprotectin). Therefore, MBQ-167 and MBQ-168 are potential PDAC therapeutics by targeting both pancreatic cancer cells and macrophages in the TME.