ARF1 controls proliferation of breast cancer cells by regulating the retinoblastoma protein

Abstract

The ADP-ribosylation factors (ARFs) 1 and 6 are small GTP-binding proteins, highly expressed and activated in several breast cancer cell lines and are associated with enhanced migration and invasiveness. In this study, we report that ARF1 has a critical role in cell proliferation. Depletion of this GTPase or expression of a dominant negative form, which both resulted in diminished ARF1 activity, led to sustained cell-growth arrest. This cellular response was associated with the induction of senescent markers in highly invasive breast cancer cells as well as in control mammary epithelial cells by a mechanism regulating retinoblastoma protein (pRB) function. When examining the role of ARF1, we found that this GTPase was highly activated in normal proliferative conditions, and that a limited amount could be found in the nucleus, associated with the chromatin of MDA-MB-231 cells. However, when cells were arrested in the G 0 /G 1 phase or transfected with a dominant negative form of ARF1, the total level of activated ARF1 was markedly reduced and the GTPase significantly enriched in the chromatin. Using biochemical approaches, we demonstrated that the GDP-bound form of ARF1 directly interacted with pRB, but not other members of this family of proteins. In addition, depletion of ARF1 or expression of ARF1T 31 N resulted in the constitutive association of pRB and E2F1, thereby stabilizing the interaction of E2F1 as well as pRB at endogenous sites of target gene promoters, preventing expression of E2F target genes, such as cyclin D1, Mcm6 and E2F1, important for cell-cycle progression. These novel findings provide direct physiological and molecular evidence for the role of ARF1 in controlling cell proliferation, dependent on its ability to regulate pRB/E2F1 activity and gene expression for enhanced proliferation and breast cancer progression.

Arf proteins in cancer cell migration

“…Since several Arfs like Arf1, Arf4 and Arf6 regulate integrin trafficking, it is not surprising that they have an impact on the migratory and invasive capacities of cancer cells. Indeed, it has been demonstrated that Arf1 controls cell migration and proliferation of breast cancer cells 26 . Arf1 interacts with β1-integrin and regulates the interaction between this integrin and key proteins of FAs, such as paxillin, talin and FAK (Fig.…”

ARF1 promotes prostate tumorigenesis via targeting oncogenic MAPK signaling

“…We have recently found that ARF1 regulates the activation of the Raf1/MEK/ERK1/2 pathway by α 2B -adrenergic receptor, a prototypic G protein-coupled receptor (GPCR) [20]. In cancer biology, ARF1 has been shown to regulate proliferation and migration of breast cancer cells which is mediated through the phosphoinositide 3-kinase (PI3K) pathway [21], the retinoblastoma protein [22] and Rac1 [23]. Interestingly, AMF-26, a small molecule octahydronaphthalene derivative, inhibits ARF1 activation and induces complete regression of human breast cancer BSY-1 xenografts [24].…”

ARF1 regulates the Rho/MLC pathway to control EGF-dependent breast cancer cell invasion

“…Because ARF1 controls migration and proliferation (Boulay et al. , 2008, 2011), we reasoned that this ARF isoform is also a key signaling effector regulating invasion. Here we demonstrate that modulation of ARF1 expression levels and activity leads to impaired invasive capacities of MDA-MB-231 cells through invadopodia maturation and shedding of microvesicles.…”