Stabilization of the Transcription Factors Slug and Twist by the Deubiquitinase Dub3 is a Key Requirement for Tumor Metastasis

The Epithelial-mesenchymal transition (EMT) represents a cellular de-differentiation process that provides cells with the increased plasticity required during embryonic development, tissue remodeling, wound healing and metastasis. Slug and Twist are two key EMT transcription factors (EMT-TFs) that are tightly regulated via ubiquitination and degradation. How Slug and Twist escape degradation and become stabilized in cancer cells remains unclear. One plausible mechanism of Slug and Twist stabilization involves removal of ubiquitin by deubiquitinases (DUBs). In this study, we identified Dub3 as a novel DUB for both Slug and Twist. We further found that Dub3 overexpression increased Slug and Twist protein levels in a dose-dependent manner, whereas Dub3-knockdown decreased their protein levels. Of importance, Dub3 interacted with Slug and Twist and prevented them from degradation, thereby promoting migration, invasion, and cancer stem cell (CSC)-like properties of breast cancer cells. Intriguingly, Dub3 was identified as an early response gene that was upregulated after exposure to inflammatory cytokines such as IL-6, which plays a critical role in the growth and metastasis of breast cancer cells, as well as the maintenance of breast CSCs. We found that Dub3 played an essential role in IL-6 induced EMT through stabilization of Slug and Twist. Our study has uncovered an IL-6-Dub3-Slug/Twist signaling axis during EMT and suggests potential approaches that could target Dub3 to prevent metastatic breast tumor

Oral administration of tipranavir with long-chain triglyceride results in moderate intestinal lymph targeting but no efficient delivery to HIV-1 reservoir in mesenteric lymph nodes

The introduction of combination antiretroviral therapy (cART) led to substantial improvement in mortality and morbidity of HIV-1 infection. However, the poor penetration of antiretroviral agents to HIV-1 reservoirs limit the ability of the antiretroviral agents to eliminate the virus. Mesenteric lymph nodes (MLNs) are one of the main HIV-1 reservoirs in patients under suppressive cART. Intestinal lymphatic absorption pathway substantially increases the concentration of lipophilic drugs in mesenteric lymph and MLNs when they are co-administered with long-chain triglyceride (LCT). Chylomicrons (CM) play a crucial role in the intestinal lymphatic absorption as they transport drugs to the lymph lacteals rather than blood capillary by forming CM-drug complexes in the enterocytes. Thus, lipophilic antiretroviral drugs could potentially be delivered to HIV-1 reservoirs in MLNs by LCT-based formulation approach. In this study, protease inhibitors (PIs) were initially screened for their potential for intestinal lymphatic targeting using a computational model. The candidates were further assessed for their experimental affinity to CM. Tipranavir (TPV) was the only-candidate with substantial affinity to both artificial and natural CM in vitro and ex vivo. Pharmacokinetics and biodistribution studies were then performed to evaluate the oral bioavailability and intestinal lymphatic targeting of TPV in rats. The results showed similar oral bioavailability of TPV with and without co-administration of LCT vehicle. Although LCT-based formulation led to 3-fold higher concentrations of TPV in mesenteric lymph compared to plasma, the levels of the drug in MLNs were similar to plasma in both LCT-based and lipid-free formulation groups. Thus, LCT-based formulation approach alone was not sufficient for effective delivery of TPV to MLNs. Future efforts should be directed to a combined highly lipophilic prodrugs/lipid-based formulation approach to target TPV, other PIs and potentially other classes of antiretroviral agents to viral reservoirs within the mesenteric lymphatic system