Despite advances in our understanding of molecular aspects of oncogenesis, cancer remains a leading cause of death. The malignant behavior of a cancer cell is driven by the inappropriate activation of transcription factors. In particular, signal transducers and activators of transcription (STATs), which regulate many critical cellular processes such as proliferation, apoptosis, and differentiation, are frequently activated inappropriately in a wide spectrum of human cancers. Multiple signaling pathways converge on the STATs, highlighting their importance in the development and progression of oncogenic diseases. STAT3 and STAT5 are two members of the STAT protein family that are the most frequently activated in cancers and can drive cancer pathogenesis directly. The development of inhibitors targeting STAT3 and STAT5 has been the subject of intense investigations in the last decade, although effective treatment options remain limited. In this review, we investigate the specific roles of STAT3 and STAT5 in normal physiology and cancer biology, discuss the opportunities and challenges in pharmacologically targeting STAT proteins and their upstream activators, and offer insights into novel therapeutic strategies to identify STAT inhibitors as cancer therapeutics.

Inflammatory reaction after ischemia-reperfusion contributes significantly to prognosis, and microglia activation is the main resource of inflammation in nervous system. STAT5 is proving to be a highly effective anti-inflammatory therapy with great potential, and inhibition of STAT5 has demonstrated significant anti-inflammation and therapeutic effects, but rarely focus on mechanism of neuroinflammation and brain injury from ischemia-reperfusion. It is the first time to found that the anti-inflammation of dauricine is mainly through STAT5-NF-κB pathway, might act as a STAT5 inhibitor. Dauricine suppressed the inflammation cytokines Eotaxin, KC, TNF-α, IL-1α, IL-1β, IL-6, IL-12β, IL-17α, and also inhibited the microglia activation. STAT5b mutant at Tyr-699 reversed the protective effect of dauricine on oxygen-glucose deprivation-reperfusion injury of neurons, and reactivated the suppression of dauricine on P-NF-κB of microglia. These results suggest that dauricine might suppress the neuroinflammation and protect the neuron from the injury of post-ischemia-reperfusion via mediating the microglia activation through STAT5-NF-κB pathway, and ss a potential therapeutic target for neuroinflammation, STAT5 needs to be raised concern in ischemic stroke.

Ruxolitinib has been approved by FDA for the treatment of myeloproliferative neoplasms such as polycythemia vera and idiopathic myelofibrosis. Although ruxolitinib has been in the clinic for more than ten years, surprisingly, no JAK2 drug resistant mutations have been identified in patients. At the moment, it is not clear whether the absence of JAK2 mutations in MPN patients is due to a lack of JAK2 addiction or residues that mediate the drug resistance compromising the JAK2 function. To find out this, we established a Ba/F3 cell-based screening strategy to predict mutations in JAK2-V617F that cause resistance towards ruxolitinib. In this study, we have recovered seven residues in the kinase domain of JAK2 that affect ruxolitinib sensitivity. All these mutations confer cross-resistance across the panel of JAK2 kinase inhibitors except JAK2-L983F. JAK2-L983F reduces the sensitivity towards ruxolitinib. However, it is sensitive towards fedratinib indicating that our screen identifies the drug-specific resistance profiles. All the ruxolitinib resistant JAK2 variants displayed sensitivity towards Type II JAK2 inhibitor CHZ-868. Finally, our study also shows that HSP90 inhibitors are potent against ruxolitinib resistant variants through the JAK2 degradation and provides the rationale for clinical evaluation of potent HSP90 inhibitors in genetic resistance driven by JAK2 inhibitors.