P53- and mevalonate pathway–driven malignancies require Arf6 for metastasis and drug resistance

Abstract

Drug resistance, metastasis, and a mesenchymal transcriptional program are central features of aggressive breast tumors. The GTPase Arf6, often overexpressed in tumors, is critical to promote epithelial-mesenchymal transition and invasiveness. The metabolic mevalonate pathway (MVP) is associated with tumor invasiveness and known to prenylate proteins, but which prenylated proteins are critical for MVP-driven cancers is unknown. We show here that MVP requires the Arf6-dependent mesenchymal program. The MVP enzyme geranylgeranyl transferase II (GGT-II) and its substrate Rab11b are critical for Arf6 trafficking to the plasma membrane, where it is activated by receptor tyrosine kinases. Consistently, mutant p53, which is known to support tumorigenesis via MVP, promotes Arf6 activation via GGT-II and Rab11b. Inhibition of MVP and GGT-II blocked invasion and metastasis and reduced cancer cell resistance against chemotherapy agents, but only in cells overexpressing Arf6 and components of the mesenchymal program. Overexpression of Arf6 and mesenchymal proteins as well as enhanced MVP activity correlated with poor patient survival. These results provide insights into the molecular basis of MVP-driven malignancy.

High expression of EPB41L5, an integral component of the Arf6-driven mesenchymal program, correlates with poor prognosis of squamous cell carcinoma of the tongue

“…An irrelevant siRNA was purchased from GE Healthcare. The specificity and efficacy of the siRNAs were confirmed previously [17, 18]. …”

“…Rabbit polyclonal antibodies against EPB41L5 were established as described previously [17]. Peroxidase-conjugated donkey antibodies against mouse or rabbit IgGs were purchased from Jackson ImmunoResearch Laboratories, Inc. Immunoblotting analysis was performed as described previously [6] using ECL Western detection reagents (GE Healthcare).…”

Endothelin type B receptor interacts with the 78‐kDa glucose‐regulated protein

“…Endogenous GRP78 was stably silenced by infecting EA.hy926 cells with lentiviruses constructed by inserting a GRP78 shRNA sequence into pLKO.1‐puro (Addgene, Watertown, MA, USA), as described previously . The infected EA.hy926 cells were selected with 0.5 μg·mL −1 puromycin.…”

Arf6 wins the MVP award

“…Mutations in the tumor suppressor p53 can up-regulate the MVP, a phenomenon that enhances the invasiveness of certain breast cancer cell lines by an unknown mechanism (2). reveal that the MVP drives cancer cell invasion by promoting the activation of the GTPase Arf6, suggesting that MVP inhibitors may be effective treatments for breast cancer patients whose tumors express high levels of Arf6 signaling components (3).…”

“…Sabe and colleagues, led by assistant professor Ari Hashimoto, first determined that the cytokine TGFβ1 activates Arf6 signaling and MDA-MB-231 cell invasion through the receptor tyrosine kinase c-Met (3). But silencing mutant p53, or inhibiting the MVP, blocked Arf6 activation and invasion.…”