Forkhead box protein A1 confers resistance to transforming growth factor-β-induced apoptosis in breast cancer cells through inhibition of Smad3 nuclear translocation

[Novel Tyrosine Phosphorylation Signals in the Nucleus and on Mitotic Spindle Fibers and Lysosomes Revealed by Strong Inhibition of Tyrosine Dephosphorylation]

Protein-tyrosine phosphorylation is one of the posttranslational modifications and plays critical roles in regulating a wide variety of cellular processes, such as cell proliferation, differentiation, adhesion, migration, survival, and apoptosis. Protein-tyrosine phosphorylation is reversibly regulated by protein-tyrosine kinases and protein-tyrosine phosphatases. Strong inhibition of protein-tyrosine phosphatase activities is required to undoubtedly detect tyrosine phosphorylation. Our extremely careful usage of Na₃VO₄, a potent protein-tyrosine phosphatase inhibitor, has revealed not only the different intracellular trafficking pathways of Src-family tyrosine kinase members but also novel tyrosine phosphorylation signals in the nucleus and on mitotic spindle fibers and lysosomes. Furthermore, despite that the first identified oncogene product v-Src is generally believed to induce transformation through continuous stimulation of proliferation signaling by its strong tyrosine kinase activity, v-Src-driven transformation was found to be caused not by continuous proliferation signaling but by v-Src tyrosine kinase activity-dependent stochastic genome alterations. Here, I summarize our findings regarding novel tyrosine phosphorylation signaling in a spatiotemporal sense and highlight the significance of the roles of tyrosine phosphorylation in transcriptional regulation inside the nucleus and chromosome dynamics.

High-Mobility Group Box 1 (HMGB1) Promotes Angiogenesis and Tumor Migration by Regulating Hypoxia-Inducible Factor 1 (HIF-1α) Expression via the Phosphatidylinositol 3-Kinase (PI3K)/AKT Signaling Pathway in Breast Cancer Cells

Background

High-mobility group box 1 (HMGB1) is an essential contributor towards initiation and progression of many kinds of cancers. Nevertheless, our understanding of the molecular etiology of HMGB1-modulated vasculogenesis, as well as invasion, of breast cancer is poor. This study explored HMGB1 expression in breast cancer and its role in the development and spread of malignancy.

Material/Methods

We enrolled 15 patients with breast cancer who received primary surgery at the Department of Thyroid and Breast Surgery in our hospital. HMGB1 was recorded and analyzed.

Results

Our investigation successfully proves that HMGB1 is upregulated in breast cancer tissues in comparison to the surrounding non-malignant tissues. HMGB1 enhanced vessel formation in breast cancer tissues by regulating hypoxia-inducible factor 1 (HIF-1α), which in turn upregulates the expression of VEGF. Furthermore, HMGB1-mediated upregulation of HIF-1α relies on its ability to stimulate the phosphatidylinositol 3-kinase (PI3K) pathway to reinforce AKT subunit phosphorylation. HMGB1 overexpression reinforces the vasculogenesis in malignancies not only in vivo but also in vitro. Additionally, shRNA knockdown of HMGB1 prohibited the vessel-forming and invasive capabilities, downregulated VEGF and HIF-1α, and suppressed AKT phosphorylation in breast cancer cells. Most importantly, PI3K/AKT axis suppression eliminated the effect of HMGB1-modulated vascularization and invasion in breast cancer cells.

Conclusions

Our research indicates that HMGB1 serves as a crucial regulator of malignant cell-modulated vessel formation and is involved in the development of malignancy. Our findings indicate that HMGB1 is a promising target for breast cancer treatment.

The Ambivalent Function of YAP in Apoptosis and Cancer

Yes-associated protein, a core regulator of the Hippo-YAP signaling pathway, plays a vital role in inhibiting apoptosis. Thus, several studies and reviews suggest that yes-associated protein is a good target for treating cancer. Unfortunately, more and more evidence demonstrates that this protein is also an essential contributor of p73-mediated apoptosis. This questions the concept that yes-associated protein is always a good target for developing novel anti-cancer drugs. Thus, the aim of this review was to evaluate the clinical relevance of yes-associated protein for cancer pathophysiology. This review also summarized the molecules, processes and drugs, which regulate Hippo-YAP signaling and discusses their effect on apoptosis. In addition, issues are defined, which should be addressed in the future in order to provide a solid basis for targeting the Hippo-YAP signaling pathway in clinical trials.