Acquisition of mesenchymal properties by cancer cells is critical for their malignant behaviour, but regulators of the mesenchymal molecular machinery and how it is activated remain elusive. Here we show that clear cell renal cell carcinomas (ccRCCs) frequently utilize the Arf6-based mesenchymal pathway to promote invasion and metastasis, similar to breast cancers. In breast cancer cells, ligand-activated receptor tyrosine kinases employ GEP100 to activate Arf6, which then recruits AMAP1; and AMAP1 then binds to the mesenchymal-specific protein EPB41L5, which promotes epithelial–mesenchymal transition and focal adhesion dynamics. In renal cancer cells, lysophosphatidic acid (LPA) activates Arf6 via its G-protein-coupled receptors, in which GTP-Gα12 binds to EFA6. The Arf6-based pathway may also contribute to drug resistance. Our results identify a specific mesenchymal molecular machinery of primary ccRCCs, which is triggered by a product of autotaxin and it is associated with poor outcome of patients.

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.

Onset of the cancer mesenchymal program is closely associated with cancer malignancy and drug resistance. Among the different epithelial–mesenchymal transition (EMT)-associated transcriptional factors, ZEB1 has a key role in inducing the mesenchymal phenotypes and stem cell-like properties of different breast cancer cells. ARF6 and its effector AMAP1 are frequently overexpressed in breast cancer cells, and promote invasion, metastasis and drug resistance. EPB41L5 is induced during EMT, and mediates the disruption of E-cadherin-based cell–cell adhesion and the promotion of focal adhesion dynamics. Here we show that EPB41L5 is an integral component of the ARF6-based pathway, which is induced by ZEB1. We found that EPB41L5 is expressed at high levels in malignant breast cancer cells and binds to AMAP1. ZEB1 induced EPB41L5 both in cancer cells and normal cells. This relationship was recaptured with The Cancer Genome Atlas RNASeq data set, and correlated with the poor outcome of the patients. In contrast, diversified events, such as tumor growth factor β1 stimulation, expression of SNAI1 and TP53 mutation, can each cause the induction of ZEB1 and EPB41L5, depending on the cellular context. Our results demonstrated that the ZEB1-EPB41L5 axis is at the core of the cancer mesenchymal program that drives ARF6-based invasion, metastasis and drug resistance of significant populations of primary breast cancers, and is tightly correlated with the poor outcomes of patients.

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Locally advanced and metastatic invasive bladder cancer (BC) has a poor prognosis, and no advanced therapies beyond cisplatin‐based combination chemotherapy have been developed. Therefore, it is an urgent issue to elucidate the underlying mechanisms of tumor progression and metastasis of invasive BC for the development of new therapeutic strategies. Here, we clarified a novel role of exosomes containing ErbB2 and CRK in a formation of premetastatic niches and subsequent metastases. CRK adaptors were overexpressed in invasive UM‐UC‐3 BC cells. In an orthotopic xenograft model, metastases to lung, liver, and bone of UM‐UC‐3 cells were completely abolished by CRK elimination. Mass spectrometry analysis identified that ErbB2 was contained in UM‐UC‐3‐derived exosomes in a CRK‐dependent manner; the exosomes significantly increased proliferation and invasion properties of low‐grade 5637 BC cells and HUVECs through FAK and PI3K/AKT signaling pathways. In athymic mice educated with UM‐UC‐3‐derived exosomes, i.v. implanted UM‐UC‐3 cells were trapped with surrounding PKH67‐labeled exosomes in lung and led to development of lung metastasis with disordered vascular proliferation. In contrast, exosomes derived from CRK‐depleted BC cells failed to induce these malignant features. Taken together, we showed that CRK adaptors elevated the expression of ErbB2/3 in BC cells, and these tyrosine kinase/adaptor units were transferred from host BC cells to metastatic recipient cells by exosomes, leading to vascular leakiness and proliferation and contributing to the formation of distant metastasis. Thus, CRK intervention with ErbB2/3 blockade might be a potent therapeutic strategy for patients with ErbB2 overexpressing advanced and metastatic BC.