Signal transducer and activator of transcription 3 (STAT3) is a cytoplasmic transcription factor that regulates cell proliferation, differentiation, apoptosis, angiogenesis, inflammation and immune responses. Aberrant STAT3 activation triggers tumor progression through oncogenic gene expression in numerous human cancers, leading to promote tumor malignancy. On the contrary, STAT3 activation in immune cells cause elevation of immunosuppressive factors. Accumulating evidence suggests that the tumor microenvironment closely interacts with the STAT3 signaling pathway. So, targeting STAT3 may improve tumor progression, and anti-cancer immune response. In this review, we summarized the role of STAT3 in cancer and the tumor microenvironment, and present inhibitors of STAT3 signaling cascades.

It is difficult to assemble multi-component metallo-supramolecular architectures in a non-statistical fashion, which limits their development toward functional materials. Herein, we report a system of interconverting bowls and cages that are able to respond to various selective stimuli (light, ligands, anions), based on the self-assembly of a photochromic dithienylethene (DTE) ligand, L a , with Pd II cations. By combining the concept of “coordination sphere engineering”, relying on bulky quinoline donors, with reversible photoswitching between the ligand’s open ( o - L a ) and closed ( c - L a ) forms, a [Pd 2 ( o - L a ) 4 ] cage ( o - C ) and a [Pd 2 ( c - L a ) 3 ] bowl ( c - B ) were obtained, respectively. This structural rearrangement modulates the system’s guest uptake capabilities. Among three bis-sulfonate guests ( G1 , G2 , and G3 ), the cage can encapsulate only the smallest ( G1 ), while the bowl binds all of them. Bowl c - B was further used to synthesize a series of heteroleptic cages, [Pd 2 L A 3 L B ], representing a motif never reported before. Additional ligands ( L c-f ), with short or long arms, tune the cavity size, thus enabling or preventing guest uptake. Addition of Br – /Ag + makes it possible to change the overall charge, again triggering guest uptake and release, as well as fourth ligand de-/recomplexation. In combination, site-selective introduction of functionality and application of external stimuli lead to an intricate system of hosts with different guest preferences. A high degree of complexity is achieved through cooperativity between only a few components.

Stimuli-responsive coordination cages allow reversible control over guest binding and release, relevant for adaptive receptors, carriers, catalysts, and complex systems. Light serves as an advantageous stimulus, as it can be applied with precise spatial and temporal resolution without producing chemical waste products. We report the first Pd-mediated coordination cage based on ligands embedding a diazocine photoswitch. While the thermodynamically more stable cis -photoisomer sloppily assembles to a mixture of species with general formula [Pd n cis -L 2 n ], the less stable trans -isomer yields a defined [Pd 2 trans -L 4 ] cage that reversibly converts back to the cis -system by irradiation at 530 nm or thermal relaxation. The [Pd n cis -L 2 n ] species do not bind a given guest; however, [Pd 2 trans -L 4 ] is able to encapsulate a bis-sulfonate as long as it is kept assembled, requiring continuous irradiation at 385 nm. In the absence of UV light, thermal relaxation results in back-switching and guest release. Assembly and properties of the system were characterized by a combination of NMR, ion mobility ESI-MS, single-crystal X-ray diffraction, and UV–vis absorption studies.

A bent fluorenone-based dipyridyl ligand L A reacts with Pd II cations to a solvent-dependent dynamic library of [Pd n L 2 n ] assemblies, constituted by a [Pd 3 L A 6 ] ring and a [Pd 4 L A 8 ] tetrahedron as major components, and a [Pd 6 L A 12 ] octahedron as minor component. Introduction of backbone steric hindrance in ligand L B allows exclusive formation of the [Pd 6 L B 12 ] octahedron. Combining equimolar amounts of both ligands results in integrative self-sorting to give an unprecedented [Pd 4 L A 4 L B 4 ] heteroleptic tetrahedron. Key to the non-statistical assembly outcome is exploiting the structural peculiarity of the [Pd 4 L 8 ] tetrahedral topology, where the four lean ligands occupy two doubly bridged edges and the bulky ligands span the four remaining, singly bridged edges. Hence, the system finds a compromise between the entropic drive to form an assembly smaller than the octahedron and the enthalpic prohibition of pairing two bulky ligands on the same edge of the triangular ring. The emission of luminescent L A is maintained in both homoleptic [Pd 3 L A 6 ] and heteroleptic [Pd 4 L A 4 L B 4 ].