A Novel Estrogen Receptor α-Targeted Near-Infrared Fluorescent Probe for in Vivo Detection of Breast Tumor

Novel GAL7-targeted fluorescent molecular imaging probe for high-grade squamous intraepithelial lesion and cervical cancer screening

BACKGROUND

Early detection and treatment are critical for improving the survival and prognosis of patients with cervical cancer. However, there is a notable scarcity of targeted imaging probes specifically designed to detect high-grade squamous intraepithelial lesions (HSIL) and cervical cancer. Our study aimed to address this gap by identifying and validating a targeted imaging probe for these conditions.

RESULTS

Using bioinformatics data, we identified galectin-7 (GAL7) as highly expressed in patients with cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC). Immunohistochemical staining of biopsy samples from 30 HSIL and cervical cancer patients verified the high and specific expression of GAL7. Further validation was performed using mouse and human CESC cell lines and tumor xenografts, confirming the consistent expression of GAL7. Based on this finding, we synthesized a GAL7-specific antibody conjugated with FITC, creating the GAL7-FITC fluorescence imaging probe. Fluorescence molecular imaging revealed that GAL7-FITC exhibited specific binding to various CESC cell lines and xenograft mouse models. Additionally, the diagnostic capability of GAL7-FITC was demonstrated in fresh HSIL specimens from cervical cone excisions, validated through histopathology and immunohistochemical analysis.

CONCLUSIONS

Our study identified GAL7 as a specific target for CESC and successfully developed the GAL7-FITC fluorescence imaging probe. GAL7-FITC has shown promising potential for clinical application in the early detection of HSIL and CESC, providing rapid fluorescence imaging diagnosis without observable toxicity. This advancement may significantly enhance the accuracy and speed of cervical cancer diagnostics, ultimately improving patient outcomes.

Near-Infrared-II Fluorescent Probes for Analytical Applications: From In Vitro Detection to In Vivo Imaging Monitoring

Biomarkers play a vital role in the regulation of life processes, especially in predicting the occurrence and development of diseases. For the early diagnosis and precise treatment of diseases, it has become necessary and significant to detect biomarkers with sensitivity, accuracy, simplicity, convenience, and even visualization. Fluorescent-probe-based techniques have been recognized as one of the most powerful tools for the sensitive detection and real time imaging of biomarkers in biological samples. However, traditional optical probes, mainly including the visible probes (400-700 nm) and the near-infrared I (NIR-I, 700-900 nm) probes, suffer from low sensitivity, poor resolution, strong absorption and scattering, and high background fluorescence, which hinder effective monitoring of biomarkers. Fortunately, the past decade has witnessed a remarkable evolution in the application fields of near-infrared II (NIR-II, 900-1700 nm) fluorescence, driven by its exceptional optical characteristics and the advancement of imaging technologies. Leveraging the superior penetration capabilities, negligible autofluorescence, and extended fluorescence emission wavelengths, NIR-II fluorescent probes significantly enhance the signal-to-noise ratio (SNR) of in vitro detection (IVD) and the temporal resolution of in vivo imaging. Our team has been committed to the design strategy, controlled synthesis, luminous mechanisms, and biomedical applications of NIR-II fluorescent probes. In this Account, we present the representative works in recent years from our group in the field of NIR-II fluorescent probes for analytical applications, ranging from in vitro detection of biomarkers to in vivo imaging monitoring of different biomarkers and various diseases, which also will further provide a general overview of analytical applications of NIR-II fluorescence probes. First, the in vitro analytical applications of NIR-II fluorescent probes are fully summarized, including tumor marker detection, virus and bacteria analysis, cell testing, and small-molecule sensing. Second, the in vivo imaging monitoring applications of NIR-II fluorescent probes are adequately discussed, including ROS detection, gas monitoring, pH sensing, small-molecule testing, receptor analysis, and the imaging diagnosis of some serious diseases. Finally, we further outline the application advantages of NIR-II fluorescent probes in analytical fields and also discuss in detail some challenges as well as their future development. There is a reasonable prospect that the in vitro detection technology and the in vivo imaging monitoring technology based on NIR-II fluorescent probes will exhibit great development potential in biomedical research and clinical disease diagnosis. We hope that this Account can expand their reach into an even broader spectrum of fields, further enhancing their impact on scientific discovery and medical practice.

Fluorescence-based techniques for investigating estrogen receptor dynamics

Understanding estrogen receptor (ER) signaling pathways is crucial for uncovering the mechanisms behind estrogen-related diseases, such as breast cancer, and addressing the effects of environmental estrogenic disruptors. Traditionally, ER signaling involves genomic events, including ligand binding, receptor dimerization, and transcriptional modulation within cellular nuclei. However, recent research have revealed ERs also participate in non-genomic signaling pathways, adding complexity to their functions. Researchers use advanced fluorescence-based techniques, leveraging fluorescent probes (FPb) to study ER dynamics in living cells, such as spatial distribution, expression kinetics, and functional activities. This review systematically examines the application of fluorescent probes in ER signaling research, covering the visualization of ER, ligandreceptor interactions, receptor dimerization, estrogen response elements (EREs)-mediated transcriptional activation, and G-proteincoupled estrogen receptor (GPER) signaling. Our aim is to provide researchers with valuable insights for employing FPb in their explorations of ER signaling. [BMB Reports 2024; 57(11): 472-483].

Clearly fluorescent delineating ER+ breast tumor incisal edge and identifying tiny metastatic tumor foci at high resolution

Fluorescence-image guided surgery (FGS) can intraoperatively provide real-time visualization of a tumor incisal edge and high-resolution identification of tumor foci to improve treatment outcomes. In this contribution, we report a fluorescent probe NB-TAM based on intramolecularly folded photoinduced electron transfer (PET), which displayed a prominent turn-on response in the near-infrared (NIR) window upon specific interaction with the estrogen receptor (ER). Significantly, NB-TAM could delineate a clear tumor incisal edge (tumor-to-normal tissue ratio > 5) in a 70-min time window, and was successfully used to guide the facile and precise resection of ER+ breast tumors in mice. To our surprise, NB-TAM was found to be capable of identifying very tiny lung metastatic ER+ breast tumor foci (0.4 × 0.3 mm), and this ultrahigh resolution was essential to effectively promote tumor resection precision and early diagnosis of tiny tumors. These results clearly elucidate the promising application of NB-TAM as a diagnostic agent for intraoperative fluorescence imaging of ER+ breast cancer.

Design, Synthesis, and Evaluation of 18F-Labeling CYP1B1 PET Tracer Based on 2-Phenylquinazolin

Cytochrome P450 (CYP)1B1 has been identified to be specifically overexpressed in several solid tumors, thus it's a potential target for the detection of tumors. Based on the 2-Phenylquinazolin CYP1B1 inhibitors, we designed and synthesized several positron emission computed tomography (PET) imaging probes targeting CYP1B1. Through IC50 determinations, most of these probes exhibited good affinity and selectivity to CYP1B1. Considering their affinity, solubility, and their 18F labeling methods, we chose compound 5c as the best candidate. The 18F radiolabeling of [18F] 5c was easy to handle with good radiolabeling yield and radiochemical purity. In vitro and in vivo stability study indicated that probe [18F]5c has good stability. In cell binding assay, [18F]5c could be specifically taken up by tumor cells, especially HCT-116 cells. Although the tumor-blood (T/B) and tumor-muscle (T/M) values and PET imaging results were unsatisfied, it is still possible to develop PET probes targeting CYP1B1 by structural modification on the basis of 5c in the future.

Evolving an Ultra-Sensitive Near-Infrared β-Galactosidase Fluorescent Probe for Breast Cancer Imaging and Surgical Resection Navigation

Early diagnosis and therapy are clinically crucial in decreasing mortality from breast carcinoma. However, the existing probes have difficulty in accurately identifying the margins and contours of breast carcinoma due to poor sensitivity and specificity. There is an urgent need to develop high-sensitive fluorescent probes for the diagnosis of breast carcinoma and for differentiating tumors from normal tissues during surgery. β-Galactosidase is a significant biomarker, whose overexpression is closely associated with the progression of breast tumors. Herein, we have constructed a β-galactosidase-activated fluorescent probe NIR-βgal-2 through rational design and molecular docking engineering simulations. The probe displayed superior sensitivity (detection limit = 2.0 × 10^-3 U/mL), great affinity (K_m = 1.84 μM), and catalytic efficiency (k_cat/K_m = 0.24 μM^-1 s^-1) for β-galactosidase. Leveraging this probe, we demonstrated the differentiation of cancer cells overexpressing β-galactosidase from normal cells and then applied the probe for intraoperative guided excision of breast tumors. Moreover, we exhibited the application of NIR-βgal-2 for the successful resection of orthotopic breast tumors by "in situ spraying" and monitored a good prognostic recovery. This work may promote the application of enzyme-activated near-infrared fluorescent probes for the development of carcinoma diagnosis and image-guided surgery.

Fluorescent sterol probes for intracellular transport, imaging, and therapeutics

Sterols play a significant role in many physiological processes affecting membrane organization, transport, permeability, and signal transduction. The development of fluorescent sterol analogs that have immediate functional relevance to the natural biomolecules is one approach to understanding the sterol-driven physiological processes. Visualizing cellular compartments with tailor-made fluorescent molecules through specific labeling methods enables organelle targeting and reveals dynamic information. In this review, we focus on the recent literature published between 2020 and 2022, with particular emphasis on extrinsic fluorophores and their investigations of sterol-driven biological processes involving sterol transport, biomolecular interactions, and biological imaging.

Robust ERα-Targeted Near-Infrared Fluorescence Probe for Selective Hydrazine Imaging in Breast Cancer

Breast cancer is the most common malignancy in women and may become worse when a high concentration of hydrazine is absorbed from the environment or drug metabolite. Therefore, rapid and sensitive detection of hydrazine in vivo is beneficial for people's health. In this work, a novel estrogen receptor α (ERα)-targeted near-infrared fluorescence probe was designed to detect hydrazine levels. The probe showed good ERα affinity and an excellent fluorescence response toward hydrazine. Selectivity experiments demonstrated that the probe had a strong anti-interference ability. Mechanistic studies, including mass spectrometry (MS) and density functional theory (DFT) calculation, indicated that intermolecular charge transfer (ICT) progress was hindered when the probe reacted with hydrazine, resulting in fluorescent quenching. In addition, the probe could selectively bind to MCF-7 breast cancer cells with excellent biocompatibility. The in vivo and ex vivo imaging studies demonstrated that the probe could rapidly visualize hydrazine with high contrast in MCF-7 xenograft tumors. Therefore, this probe can serve as a potential tool to robustly monitor hydrazine levels in vivo.

Using the yeast three-hybrid system for the identification of small molecule-protein interactions with the example of ethinylestradiol

Since the first report on a yeast three-hybrid system, several approaches have successfully utilized different setups for discovering targets of small molecule drugs. Compared to broadly applied MS based target identification approaches, the yeast three-hybrid system represents a complementary method that allows for the straightforward identification of direct protein binders of selected small molecules. One major drawback of this system, however, is that the drug has to be taken up by the yeast cells in sufficient concentrations. Here, we report the establishment of a yeast three-hybrid screen in the deletion strain ABC9Δ, which is characterized by being highly permeable to small molecules. We used this system to screen for protein binding partners of ethinylestradiol, a widely used drug mainly for contraception and hormone replacement therapy. We identified procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2 or lysyl hydroxylase, LH2) as a novel direct target and were able to confirm the interaction identified with the yeast three-hybrid system by a complementary method, affinity chromatography, to prove the validity of the hit. Furthermore, we provide evidence for an interaction between the drug and PLOD2 in vitro and in cellulo.

Heptamethine Cyanine–Based Application for Cancer Theranostics

Cancer is the most common life-threatening malignant disease. The future of personalized cancer treatments relies on the development of functional agents that have tumor-targeted anticancer activities and can be detected in tumors through imaging. Cyanines, especially heptamethine cyanine (Cy7), have prospective application because of their excellent tumor-targeting capacity, high quantum yield, low tissue autofluorescence, long absorption wavelength, and low background interference. In this review, the application of Cy7 and its derivatives in tumors is comprehensively explored. Cy7 is enormously acknowledged in the field of non-invasive therapy that can “detect” and “kill” tumor cells via near-infrared fluorescence (NIRF) imaging, photothermal therapy (PTT), and photodynamic therapy (PDT). Furthermore, Cy7 is more available and has excellent properties in cancer theranostics by the presence of multifunctional nanoparticles via fulfilling multimodal imaging and combination therapy simultaneously. This review provides a comprehensive scope of Cy7’s application for cancer NIRF imaging, phototherapy, nanoprobe-based combination therapy in recent years. A deeper understanding of the application of imaging and treatment underlying Cy7 in cancer may provide new strategies for drug development based on cyanine. Thus, the review will lead the way to new types with optical properties and practical transformation to clinical practice.

Estrogen Receptor β-Targeted Near-Infrared Inherently Fluorescent Probe: A Potent Tool for Estrogen Receptor β Research

Estrogen receptor β (ERβ) is associated with many diseases, and ERβ probes can help to reveal the complex role of ERβ and promote the development of ERβ-targeted therapy. Herein, we designed and synthesized the first ERβ-targeted near-infrared (NIR) inherently fluorescent probe P5, which showed the advantages of high ERβ selectivity, good optical properties, and excellent ERβ imaging capability in living cells. The probe was successfully utilized to explore ERβ motion characteristic, and for the first time, the diffusion coefficient of ERβ was obtained. Moreover, P5 was also successfully applied to the in vivo imaging of ERβ in the prostate cancer mice model. Therefore, this ERβ-targeted NIR probe might be employed as a potential tool for the research of ERβ and related diseases.

Near-infrared (NIR) fluorescence-emitting small organic molecules for cancer imaging and therapy

We discuss recent advances made in the development of NIR fluorescence-emitting small organic molecules for tumor imaging and therapy.

A selective and sensitive near-infrared fluorescent probe for real-time detection of Cu(i)

The disruption of copper homeostasis (Cu+/Cu2+) may cause neurodegenerative disorders. Thus, the need for understanding the role of Cu+ in physiological and pathological processes prompted the development of improved methods of Cu+ analysis. Herein, a new near-infrared (NIR) fluorescent turn-on probe (NPCu) for the detection of Cu+ was developed based on a Cu+-mediated benzylic ether bond cleavage mechanism. The probe showed high selectivity and sensitivity toward Cu+, and was successfully applied for bioimaging of Cu+ in living cells.

Design and Application of Receptor-Targeted Fluorescent Probes Based on Small Molecular Fluorescent Dyes

In recent years, a variety of receptor-targeted fluorescent probes have been developed and widely used to realize the visualization of certain receptors, which facilitates the early diagnosis and treatment of diseases. In this Review, we focus on the recent achievements in design, chemical structure, imaging characterization, and potential applications of receptor-targeted fluorescent probes from the past 10 years. The development and application of receptor-targeted fluorescent probes will expand our knowledge of the distribution and function of disease-related receptors, shed light on the drug discovery for clinical diseases where receptors are implicated, and feed into the diagnosis and treatment of a plethora of diseases, including tumors.

Cyanine Conjugate-Based Biomedical Imaging Probes

Cyanine is a class of fluorescent dye with meritorious fluorescence properties and has motivated numerous researchers to explore its imaging capabilities by miscellaneous structural modification and functionalization strategies. The covalent conjugation with other functional molecules represents a distinctive design strategy and has shown immense potential in both basic and clinical research. This review article summarizes recent achievements in cyanine conjugate-based probes for biomedical imaging. Particular attention is paid to the conjugation with targeting warheads and other contrast agents for targeted fluorescence imaging and multimodal imaging, respectively. Additionally, their clinical potential in cancer diagnostics is highlighted and some concurrent impediments for clinical translation are discussed.

Development of a novel melatonin-modified near-infrared fluorescent probe for in vivo hepatocellular carcinoma imaging

Hepatocellular carcinoma (HCC) is a common malignancy worldwide with poor prognosis. The early identification and precise resection of HCC are essential for improving the prognosis and overall survival of patients. In clinical practice, fluorescence imaging is a powerful technology to identify and remove HCC lesions, but accurate and reliable detection of HCC continues to remain a challenge due to non-specificity and false-positive uptake of probes. To circumvent these problems, it is crucial to design a specific probe for the accurate detection of HCC. Herein, we reported the design and synthesis of an NIR fluorescent probe by conjugating IRDye800CW with melatonin, which plays a significant role in the HCC development. The in vivo imaging revealed that IRDye800-MT was uptake specifically by the HCC tumor with a high tumor-to-background ratio. These results demonstrated that IRDye800-MT might hold clinical potentials for future diagnosis of HCC patients.

Establishment of evaluation criteria for the development of high quality ERα-targeted fluorescent probes

ERα-targeted fluorescent probes are important tools for ERα study. In order to develop high quality ERα-targeted probes, a sound and complete evaluation system is essential but has not been established yet. Herein, we set up a series of evaluation criteria for ERα-targeted fluorescent probes including ERα binding affinity, fluorescence quantum yield, cytotoxicity, ERα tracking capacity, ERα selectivity and ERα labeling ability. To verify the practicability of the evaluation criteria, we designed and synthesized two ERα-targeted fluorescent probes and fully characterized their properties based on the proposed evaluation criteria. It showed that the probes exhibited better performance. Moreover, we applied the probes in MCF-7 cells to study the ERα motion characteristics for the first time. We hope that our evaluation criteria could be helpful for the establishment of a complete evaluation system for ERα-targeted fluorescent probes.

Rational design of ERα targeting hypoxia turn-on fluorescent probes with antiproliferative activity for breast cancer

The overexpression of estrogen receptor (ER) α is not only closely related to the development of ER⁺ breast cancer, but is also an important biomarker for clinical diagnosis and treatment. Herein, we report several ERα targeting hypoxia turn-on fluorescent probes with antitumor activity for breast cancer cells. Among them, probes 3 and 5 displayed good ERα targeting ability and favorable hypoxia turn-on response in MCF-7 cells. Moreover, the probes 3 and 5 exhibited good antiproliferative activity towards MCF-7 cells (IC₅₀ = 8.5 μM, 10.3 μM) and a much lower cytotoxicity to normal cells compared with the positive control. It is expected that these novel fluorescent probes may provide useful tools for the theranostics of ER⁺ breast cancer.

Quicker, deeper and stronger imaging: A review of tumor-targeted, near-infrared fluorescent dyes for fluorescence guided surgery in the preclinical and clinical stages

Cancer is a public health problem and the main cause of human mortality and morbidity worldwide. Complete removal of tumors and metastatic lymph nodes in surgery is significantly beneficial for the prognosis of patients. Tumor-targeted, near-infrared fluorescent (NIRF) imaging is an emerging field of real-time intraoperative cancer imaging based on tumor-targeted NIRF dyes. Targeted NIRF dyes contain NIRF fluorophores and specific binding ligands such as antibodies, peptides and small molecules. The present article reviews recently updated tumor-targeted NIRF dyes for the molecular imaging of malignant tumors in the preclinical stage and clinical trials. The strengths and challenges of NIRF agents with tumor-targeting ability are also summarized. Smaller ligands, near infrared II dyes, dual-modality dyes and activatable dyes may contribute to quicker, deeper, stronger imaging in the nearest future. In this review, we highlighted tumor-targeted NIRF dyes for fluorescence-guided surgery and their potential clinical translation.