The guanosine triphosphatases of the Rho and Rac subfamilies regulate protumorigenic pathways and are activated by guanine nucleotide exchange factors (Rho GEFs), which could be potential targets for anticancer therapies. We report that two Rho GEFs, Vav2 and Vav3, play synergistic roles in breast cancer by sustaining tumor growth, neoangiogenesis, and many of the steps involved in lung-specific metastasis. The involvement of Vav proteins in these processes did not correlate with Rac1 and RhoA activity or cell migration, implying the presence of additional biological programs. Microarray analyses revealed that Vav2 and Vav3 controlled a vast transcriptional program in breast cancer cells through mechanisms that were shared between the two proteins, isoform-specific or synergistic. Furthermore, the abundance of Vav-regulated transcripts was modulated by Rac1-dependent and Rac1-independent pathways. This transcriptome encoded therapeutically targetable proteins that played nonredundant roles in primary tumorigenesis and lung-specific metastasis, such as integrin-linked kinase (Ilk), the transforming growth factor-β family ligand inhibin βA, cyclooxygenase-2, and the epithelial cell adhesion molecule Tacstd2. It also contained gene signatures that predicted disease outcome in breast cancer patients. These results identify possible targets for treating breast cancer and lung metastases and provide a potential diagnostic tool for clinical use.

Aberrant activation of the phosphoinositide-3-kinase (PI3K)/ PTEN/Akt pathway, leading to increased proliferation and decreased apoptosis, has been implicated in several human pathologies including cancer. Our previous data have shown that Akt-mediated signaling is an essential mediator in the mouse skin carcinogenesis system during both the tumor promotion and progression stages. In addition, overexpression of Akt is also able to transform keratinocytes through transcriptional and posttranscriptional processes. Here, we report the consequences of the increased expression of Akt1 (wtAkt) or constitutively active Akt1 (myrAkt) in the basal layer of stratified epithelia using the bovine keratin K5 promoter. These mice display alterations in epidermal proliferation and differentiation. In addition, transgenic mice with the highest levels of Akt expression developed spontaneous epithelial tumors in multiple organs with age.

Bladder cancer (BC) is a highly prevalent human disease in which retinoblastoma (Rb) pathway inactivation and epigenetic alterations are common events. However, the connection between these two processes is still poorly understood. Here we show that the in vivo inactivation of all Retinoblastoma (Rb) family genes in the mouse urothelium is sufficient to initiate BC development. The characterization of the mouse tumors revealed multiple molecular features of human BC, including the activation of E2F transcription factor and subsequent Ezh2 expression, and the activation of several signaling pathways previously identified as highly relevant in urothelial tumors. These mice represent a genetically defined model for human high-grade superficial BC. Whole transcriptional characterizations of mouse and human bladder tumors revealed a significant overlap and confirm the predominant role for Ezh2 in the downregulation of gene expression programs. Importantly, the increased tumor recurrence and progression in human superficial BC patients is associated with increased E2F and Ezh2 expression and Ezh2-mediated gene expression repression. Collectively, our studies provide a genetically defined model for human high-grade superficial BC and demonstrate the existence of an Rb-E2F-Ezh2 axis in bladder whose disruption can promote tumor development.

The assembly of African swine fever virus (ASFV) at the cytoplasmic virus factories commences with the formation of precursor membranous structures, which are thought to be collapsed cisternal domains recruited from the surrounding endoplasmic reticulum (ER). This report analyzes the role in virus morphogenesis of the structural protein p54, a 25-kDa polypeptide encoded by the E183L gene that contains a putative transmembrane domain and localizes at the ER-derived envelope precursors. We show that protein p54 behaves in vitro and in infected cells as a type I membrane-anchored protein that forms disulfide-linked homodimers through its unique luminal cysteine. Moreover, p54 is targeted to the ER membranes when it is transiently expressed in transfected cells. Using a lethal conditional recombinant, vE183Li, we also demonstrate that the repression of p54 synthesis arrests virus morphogenesis at a very early stage, even prior to the formation of the precursor membranes. Under restrictive conditions, the virus factories appeared as discrete electron-lucent areas essentially free of viral structures. In contrast, outside the assembly sites, large amounts of aberrant zipper-like structures formed by the unprocessed core polyproteins pp220 and pp62 were produced in close association to ER cisternae. Altogether, these results indicate that the transmembrane structural protein p54 is critical for the recruitment and transformation of the ER membranes into the precursors of the viral envelope.