Fluorescent Kinase Probes Enabling Identification and Dynamic Imaging of HER2(+) Cells

Design, synthesis and biological evaluation of small molecule fluorescent probes targeting EGFR for tumor detection and treatment

The epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor that plays a crucial role in cell differentiation and tumor progression, and its overexpression is closely associated with the development and metastasis of multiple cancers. The development of a fluorescent probe capable of targeting EGFR while simultaneously integrating diagnostic and therapeutic functions could have a profound impact on the treatment of related cancers. In this study, we developed a series of EGFR-targeting probes that consisted of an environment-sensitive 1,8-naphthalimide fluorophore, a linker unit and a targeting unit (gefitinib), using a coupling strategy. The synthesized probes were first evaluated for their spectroscopic properties and cytotoxicities against different cell lines, which were selected based on their intrinsic EGFR expression levels. Remarkably, among the probes tested, GP1 showed outstanding environmental sensitivity and exhibited a specific response to tumor cells that overexpress EGFR. Furthermore, the representative probe GP1 was evaluated for its EGFR-specific targeting ability in live-cell fluorescence imaging and in vivo xenograft imaging, as well as its in vivo anti-tumor activity. The results showed that the probe GP1 had excellent EGFR-specific targeting ability, exhibited competitive replacement behavior towards the EGFR inhibitor gefitinib, and demonstrated potent anti-tumor effects in a CT-26 tumor-bearing mouse model. Overall, as a turn-on EGFR targeting fluorescent ligand, GP1 holds immense promise as a valuable tool for tumor detection and treatment.

M1 Macrophages Enhance Survival and Invasion of Oral Squamous Cell Carcinoma by Inducing GDF15-Mediated ErbB2 Phosphorylation

M2 macrophages are generally recognized to have a protumor role, while the effect of M1 macrophages in cancer is controversial. Here, the in vitro and in vivo effects of conditioned medium from M1 macrophages (M1-CM) on oral squamous cell carcinoma (OSCC) cells and a potential mechanism were studied. CCK-8, colony formation, EdU labeling, xenograft growth, and Transwell assays were utilized to observe cell survival/proliferation and migration/invasion, respectively, in OSCC cell lines treated with basic medium (BM) and M1-CM. The ErbB2 phosphorylation inhibitor (CI-1033) and GDF15 knockout cell lines were used to appraise the role of ErbB2 and GDF15 in mediating the effects of M1-CM. Compared with BM, M1-CM significantly enhanced the survival/proliferation of SCC25 cells. The migration/invasion of SCC25 and CAL27 cells also increased. Mechanically, M1-CM promoted GDF15 expression and increased the phosphorylation of ErbB2, AKT, and ErK. CI-1033 significantly declined the M1-CM-induced activation of p-AKT and p-ErK and its protumor effects. M1-CM stimulated enhancement of p-ErbB2 expression was significantly decreased in cells with GDF15 gene knockout vs without. In xenograft, M1-CM pretreatment significantly promoted the carcinogenic potential of OSCC cells. Our results demonstrate that M1 macrophages induce the proliferation, migration, invasion, and xenograft development of OSCC cells. Mechanistically, this protumor effect of M1 macrophages is partly associated with inducing GDF15-mediated ErbB2 phosphorylation.

Fluorescent kinase inhibitors as probes in cancer

Fluorescent dyes attached to kinase inhibitors (KIs) can be used to probe kinases in vitro, in cells, and in vivo. Ideal characteristics of the dyes vary with their intended applications. Fluorophores used in vitro may inform on kinase active site environments, hence the dyes used should be small and have minimal impact on modes of binding. These probes may have short wavelength emissions since blue fluorophores are perfectly adequate in this context. Thus, for instance, KI fragments that mimic nucleobases may be modified to be fluorescent with minimal perturbation to the kinase inhibitor structure. However, progressively larger dyes, that emit at longer wavelengths, are required for cellular and in vivo work. In cells, it is necessary to have emissions above autofluorescence of biomolecules, and near infrared dyes are needed to enable excitation and observation through tissue in vivo. This review is organized to describe probes intended for applications in vitro, in cells, then in vivo. The readers will observe that the probes featured tend to become larger and responsive to the near infared end of the spectrum as the review progresses. Readers may also be surprised to realize that relatively few dyes have been used for fluorophore-kinase inhibitor conjugates, and the area is open for innovations in the types of fluorophores used.

Insight into triphenylamine and coumarin serving as copper (II) sensors with "OFF" strategy and for bio-imaging in living cells

Chemosensing is one of the widest and powerful techniques for response to anions and cations in living systems serving as bio-probes. Meanwhile, copper(II) (Cu(II)) widely exists in the environment and the human body as a common trace element, which plays an necessary role in most physiological processes. Thus, it is extremely urgent to explore means for effective, rapid and convenient detection of Cu(II) in living cells. Herein, we introduce a novel strategy for designing triphenylamine (TS) and coumarin-based (CS) functional sensors for Cu(II) detection with fluorescence "OFF" switching mechanism by blocking intramolecular charge transfer (ICT). Based on this design strategy, we have demonstrated two kinds of fluorophores sensors with aunique new fluorescent dye and excellent photophysical properties, which have shown rapid recognition of Cu(II) via a stoichiometric ratio of 2:1 and the proposed binding mode was confirmed by the single-crystal structure of CS-Cu(II) complex. In addition, we have carried out density functional theory (DFT) calculation with the B3LYP exchange functional employing RB3LYP/6-31G basis sets to get insight into the mechanism of Cu(II)-sensors alongside their optical properties. Furthermore, the sensors were capable of bio-imaging Cu(II) in living cancer cells (HepG2, A549 and Hela) with low cytotoxicity and good biocompatibility shown. Taken together, We expect that this novel strategy would provide new insight into the development of Cu(II) detection techniques and could be used more for biomedical applications.

Discovery of Nonpeptide, Reversible HER1/HER2 Dual-Targeting Small-Molecule Inhibitors as Near-Infrared Fluorescent Probes for Efficient Tumor Detection, Diagnostic Imaging, and Drug Screening

The abnormal expression of epidermal growth factor receptors HER1(EGFR) and HER2 is strongly associated with cancer invasion, metastasis, and angiogenesis. Their molecular detection is mainly executed using genetically encoded or antibody-based diagnostic tracers, but no dual-targeting small-molecule bioprobe has been achieved. Here, we report the novel small-molecule fluorescent probes Cy3-AFTN and Cy5-AFTN as potent dual-targeting inhibitors for efficient detection of HER1/HER2 expression in cancer cells and in vivo tumor diagnostic imaging. Unlike the irreversible HER1/HER2 inhibitors, Cy3-AFTN and Cy5-AFTN were designed as reversible/noncovalent probes based on the clinical drug afatinib, by making the molecule structurally impossible for receptor-mediated Michael additions. The synthesized probes were validated with live cell fluorescence imaging, flow cytometry and confocal-mediated competitive binding inhibition, molecular docking study, and in vivo xenograft tumor detection. The probes are competitively replaceable by other HER1/HER2 inhibitors; thus, they are potentially useful in fluorometric high-throughput screening for drug discovery.

Synthesis and photophysical properties of a fluorescent cyanoquinoline probe for profiling ERBB2 kinase inhibitor response

A fluorescent probe targeting the ERBB2 receptor tyrosine was designed, synthesized and evaluated as reporter of ERBB2 dynamics in overexpressing BT474, i.e. Her2(+), cells. Two cyanoquinazoline (CQ) probes modeled after type-I (CQ1) or active state and type-II (CQ2) or inactive state inhibitors were designed and synthesized with extended π systems that impart binding-induced, turn-on fluorescence. Solution spectroscopy revealed that CQ1 exhibited attractive photophysical properties and displayed turn-on emission in the presence of purified, soluble ERBB2 kinase domain, while CQ2 was found to be non-emissive, likely due to quenching via a photoinduced electron transfer mechanism. Live cell imaging with CQ1 revealed that this probe targeted an intracellular population of ERBB2, which increased following treatment with type-I inhibitors, gefinitib and canertinib, but showed no response to type-II inhibitors. CQ1 thus provides a novel means of imaging the dynamic response of ERBB2(+) cells to kinase inhibitors.