The Canonical Wnt Pathway Drives Macropinocytosis in Cancer

Abstract

Macropinocytosis has emerged as an important pathway of protein acquisition in cancer cells, particularly in tumors with activated Ras such as pancreatic and colon cancer. Macropinocytosis is also the route of entry of Bacillus Calmette-Guerin (BCG) and other microbial therapies of cancer. Despite this important role in tumor biology and therapy, the full mechanisms by which cancer cells can activate macropinocytosis remain incompletely defined. Using BCG uptake to assay macropinocytosis, we executed a genome-wide shRNA screen for macropinocytosis activators and identified Wnt pathway activation as a strong driver of macropinocytosis. Wnt-driven macropinocytosis was downstream of the β-catenin-dependent canonical Wnt pathway, was PAK1 dependent, and supported albumin-dependent growth in Ras-WT cells. In cells with activated Ras-dependent macropinocytosis, pharmacologic or genetic inhibition of Wnt signaling suppressed macropinocytosis. In a mouse model of Wnt-driven colonic hyperplasia via silencing, Wnt-activated macropinocytosis stimulated uptake of luminal microbiota, a process reversed by topical pharmacologic inhibition of macropinocytosis. Our findings indicate that Wnt pathway activation drives macropinocytosis in cancer, and its inhibition could provide a therapeutic vulnerability in Wnt-driven intestinal polyposis and cancers with Wnt activation. The Wnt pathway drives macropinocytosis in cancer cells, thereby contributing to cancer growth in nutrient-deficient conditions and, in the context of colon cancer, to the early phases of oncogenesis. .

Combined Proteomic and Genetic Interaction Mapping Reveals New RAS Effector Pathways and Susceptibilities

“…We demonstrate that RIN1 is a significant regulator of macropinocytosis, a process which has recently been specifically associated with RAS activation ( Figure 2B,C) (22,23). These observations establish a mechanistic link between RAS and macropinocytosis and provide a context for more detailed screening (45).…”

ATM inhibition drives metabolic adaptation via induction of macropinocytosis

“…Previous studies have shown that macropinocytosis is one mechanism whereby cancer cells scavenge nutrients from the microenvironment to support survival and proliferation (Commisso et al, 2013;Davidson et al, 2017;Hodakoski et al, 2019;Kamphorst et al, 2015;Kim et al, 2018;Lee et al, 2019;Palm, 2019;Palm et al, 2017;Recouvreux and Commisso, 2017;Redelman-Sidi et al, 2018;Yao et al, 2019;Zhang and Commisso, 2019). Due to its large size, fluorescently-labeled dextran is used as a surrogate for macropinocytosis as it cannot be taken up through other endocytic pathways Ivanov, 2008).…”

“…Next we aimed to determine the mechanism of macropinocytosis induction downstream of ATM inhibition. Towards this goal, we used pharmacological or genetic inhibition of PI3K/AKT, WNT, and AMPK, three known inducers of macropinocytosis (Commisso et al, 2013;Kim et al, 2018;Redelman-Sidi et al, 2018;Tejeda-Munoz et al). While inhibition of PI3K, AKT, or WNT had no effect ( Fig.…”

“…Finally, we aimed to determine the metabolic consequences of increased macropinocytosis due to inhibition of ATM. Previous studies have demonstrated that diverse nutrients including proteins, lipids, glucose, and others are taken up by macropinocytosis to promote cancer cell survival under nutrient stress (Commisso et al, 2013;Hodakoski et al, 2019;Kamphorst et al, 2015;Kim et al, 2018;Palm, 2019;Palm et al, 2017;Recouvreux and Commisso, 2017;Redelman-Sidi et al, 2018; Tejeda-Munoz et al; Zhang and Commisso, 2019). To determine the metabolites that may be important for tumors in the ATM inhibitor treated mice, we performed metabolomics on the tumor tissue, interstitial fluid, and the ascites fluid, which commonly occurs in ovarian cancer models.…”

“…Macropinocytosis is an endocytic process whereby cells take up fluid, macromolecules, metabolites, and other cargo from the surrounding microenvironment (King and Kay, 2019;Palm, 2019;Zhang and Commisso, 2019). Many studies have evaluated the critical role of macropinocytosis as a nutrient scavenging mechanism in cancers under nutrientdeprived conditions (Commisso et al, 2013;Davidson et al, 2017;Hodakoski et al, 2019;Kamphorst et al, 2015;Kim et al, 2018;Redelman-Sidi et al, 2018;Tejeda-Munoz et al;Yao et al, 2019). To date, these studies have focused on cancers with high PI3K activity, such as those with mutant RAS or PTEN loss, which act upstream of the Rac1-Pak1 actin remodeling pathway to promote macropinosome formation .…”