ImmunoPET Imaging of CD146 in Murine Models of Intrapulmonary Metastasis of Non-Small Cell Lung Cancer

124I-labeled anti-CD147 antibody for noninvasive detection of CD147-positive pan-cancers: construction and preclinical studies

Extracellular matrix metalloproteinase inducer CD147 is a glycoprotein on the cell surface. There is minimal expression of CD147 in normal epithelial and fetal tissues, but it is highly expressed in a number of aggressive tumors. CD147 has been implicated in pan-cancer immunity and progression. With the development of CD147-targeting therapeutic strategy, accurate detection of CD147 expression in tumors and its changes during the therapy is necessary. In this study we constructed a novel radiotracer by labeling the anti-CD147 mAb with radionuclide 124/125I (124/125I-anti-CD147) for noninvasive detection of CD147 expression in pan-cancers, and characterized its physicochemical properties, affinity, metabolic characteristics, biodistribution and immunoPET imaging with 124I-IgG and 18F-FDG as controls. By examining the expression of CD147 in cancer cell lines, we found high CD147 expression in colon cancer cells LS174T, FADU human pharyngeal squamous cancer cells and 22RV1 human prostate cancer cells, and low expression of CD147 in human pancreatic cancer cells ASPC1 and human gastric cancer cells BGC823. 124/125I-anti-CD147 was prepared using N-bromine succinimide (NBS) as oxidant and purified by PD-10 column. Its radiochemical purity (RCP) was over 99% and maintained over 85% in saline or 5% human serum albumin (HSA) for more than 7 d; the RCP of 125I-anti-CD147 in blood was over 90% at 3 h post injection (p.i.) in healthy mice. The Kd value of 125I-anti-CD147 to CD147 protein was 6.344 nM, while that of 125I-IgG was over 100 nM. 125I-anti-CD147 showed much greater uptake in CD147 high-expression cancer cells compared to CD147 low-expression cancer cells. After intravenous injection in healthy mice, 125I-anti-CD147 showed high initial uptake in blood pool and liver, the uptake was decreased with time. The biological half-life of distribution and clearance phases in healthy mice were 0.63 h and 19.60 h, respectively. The effective dose of 124I-anti-CD147 was estimated as 0.104 mSv/MBq. We conducted immunoPET imaging in tumor-bearing mice, and demonstrated a significantly higher tumor-to-muscle ratio of 124I-anti-CD147 compared to that of 124I-IgG and 18F-FDG in CD147 (+) tumors. The expression levels of CD147 in cells and tumors were positively correlated with the maximum standardized uptake value (SUVmax) (P < 0.01). In conclusion, 124/125I-anti-CD147 displays high affinity to CD147, and represents potential for the imaging of CD147-positive tumors. The development of 124I-anti-CD147 may provide new insights into the regulation of tumor microenvironment and formulation of precision diagnosis and treatment programs for tumors.

CD146-targeted nuclear medicine imaging in cancer: state of the art

The transmembrane glycoprotein adhesion molecule CD146 is overexpressed in a wide variety of cancers. Through molecular imaging, a specific biomarker's expression and distribution can be viewed in vivo non-invasively. Radionuclide-labeled monoclonal antibodies or relevant fragments that target CD146 may find potential applications in cancer imaging, thereby offering tremendous value in cancer diagnosis, staging, prognosis evaluation, and prediction of drug resistance. This review discusses the recent developments of CD146-targeted molecular imaging via nuclear medicine, especially in malignant melanoma, brain tumor, lung cancer, liver cancer, breast cancer, and pancreatic cancer. Many studies have proved that CD146 targeting may present a promising strategy for cancer theranostics.

Radionuclide-based theranostics - a promising strategy for lung cancer

PURPOSE

This review aims to provide a comprehensive overview of the latest literature on personalized lung cancer management using different ligands and radionuclide-based tumor-targeting agents.

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide. Due to the heterogeneity of lung cancer, advances in precision medicine may enhance the disease management landscape. More recently, theranostics using the same molecule labeled with two different radionuclides for imaging and treatment has emerged as a promising strategy for systemic cancer management. In radionuclide-based theranostics, the target, ligand, and radionuclide should all be carefully considered to achieve an accurate diagnosis and optimal therapeutic effects for lung cancer.

METHODS

We summarize the latest radiotracers and radioligand therapeutic agents used in diagnosing and treating lung cancer. In addition, we discuss the potential clinical applications and limitations associated with target-dependent radiotracers as well as therapeutic radionuclides. Finally, we provide our views on the perspectives for future development in this field.

CONCLUSIONS

Radionuclide-based theranostics show great potential in tailored medical care. We expect that this review can provide an understanding of the latest advances in radionuclide therapy for lung cancer and promote the application of radioligand theranostics in personalized medicine.

PET Imaging of Lung Cancers in Precision Medicine: Current Landscape and Future Perspective

Despite the recent advances in cancer treatment, lung cancer remains the leading cause of cancer mortality worldwide. Immunotherapies using immune checkpoint inhibitors (ICIs) achieved substantial efficacy in nonsmall cell lung cancer (NSCLC). Currently, most ICIs are still a monoclonal antibody (mAb). Using mAbs or antibody derivatives labeled with radionuclide as the tracers, immunopositron emission tomography (immunoPET) possesses multiple advantages over traditional ¹⁸F-FDG PET in imaging lung cancers. ImmunoPET presents excellent potential in detecting, diagnosing, staging, risk stratification, treatment guidance, and recurrence monitoring of lung cancers. By using radiolabeled mAbs, immunoPET can visualize the biodistribution and uptake of ICIs, providing a noninvasive modality for patient stratification and response evaluation. Some novel targets and associated tracers for immunoPET have been discovered and investigated. This Review introduces the value of immunoPET in imaging lung cancers by summarizing both preclinical and clinical evidence. We also emphasize the value of immunoPET in optimizing immunotherapy in NSCLC. Lastly, immunoPET probes developed for imaging small cell lung cancer (SCLC) will also be discussed. Although the major focus is to summarize the immunoPET tracers for lung cancers, we also highlighted several small-molecule PET tracers to give readers a balanced view of the development status.

ImmunoPET: Antibody-Based PET Imaging in Solid Tumors

Immuno-positron emission tomography (immunoPET) is a molecular imaging modality combining the high sensitivity of PET with the specific targeting ability of monoclonal antibodies. Various radioimmunotracers have been successfully developed to target a broad spectrum of molecules expressed by malignant cells or tumor microenvironments. Only a few are translated into clinical studies and barely into clinical practices. Some drawbacks include slow radioimmunotracer kinetics, high physiologic uptake in lymphoid organs, and heterogeneous activity in tumoral lesions. Measures are taken to overcome the disadvantages, and new tracers are being developed. In this review, we aim to mention the fundamental components of immunoPET imaging, explore the groundbreaking success achieved using this new technique, and review different radioimmunotracers employed in various solid tumors to elaborate on this relatively new imaging modality.

ImmunoPET of the differential expression of CD146 in breast cancer

With advancement in antibody engineering, the development and characterization of new cancer-specific molecular targets are in the forefront of this PET-antibody combination "revolution". Overexpression of CD146 in different types of tumors, including breast tumor, has been associated with tumor progression and poor prognosis. Non-invasive detection of CD146 with a monoclonal antibody may provide a noninvasive diagnostic tool with high specificity and accountability.

METHODS

Herein, we have developed a CD146-specific monoclonal antibody (YY146), radiolabeled it with 52Mn and 89Zr and identified its capability in acting as a non-invasive imaging agent that specific targets CD146 in different murine breast cancer models. CD146 expression was first screened in different breast tumor cell lines through Western Blot and confirmed its binding ability to YY146 using Flow Cytometry. Serial immunoPET images were carried out after intravenous administration of 52Mn or 89Zr labeled YY146. In addition, we also performed in vivo fluorescence imaging in animals injected with YY146 conjugated with Cy5.5.

RESULTS

Western Blot results show that MDA-MB-435 cell line had greater levels of CD146 expression when compared to the other cell lines investigated. Flow cytometry confirmed binding ability of YY146. PET images revealed well correlated uptake between tumor uptake and CD146 expression levels, confirmed by biodistribution studies and fluorescence imaging.

CONCLUSION

PET imaging, for up to 7 days, of mice bearing three different breast tumors were carried out and revealed radiotracer uptake in tumors that strongly (r2 = 0.98, P < 0.01), correlated with CD146 expression levels, as confirmed by in vitro and ex vivo studies.

Interactions Between Tumor Biology and Targeted Nanoplatforms for Imaging Applications

Although considerable efforts have been conducted to diagnose, improve, and treat cancer in the past few decades, existing therapeutic options are insufficient, as mortality and morbidity rates remain high. Perhaps the best hope for substantial improvement lies in early detection. Recent advances in nanotechnology are expected to increase the current understanding of tumor biology, and will allow nanomaterials to be used for targeting and imaging both in vitro and in vivo experimental models. Owing to their intrinsic physicochemical characteristics, nanostructures (NSs) are valuable tools that have received much attention in nanoimaging. Consequently, rationally designed NSs have been successfully employed in cancer imaging for targeting cancer-specific or cancer-associated molecules and pathways. This review categorizes imaging and targeting approaches according to cancer type, and also highlights some new safe approaches involving membrane-coated nanoparticles, tumor cell-derived extracellular vesicles, circulating tumor cells, cell-free DNAs, and cancer stem cells in the hope of developing more precise targeting and multifunctional nanotechnology-based imaging probes in the future.

ImmunoPET: Concept, Design, and Applications

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as ⁸⁹Zr-Df-pertuzumab and ⁸⁹Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

CD146 T cells in lung cancer: its function, detection, and clinical implications as a biomarker and therapeutic target

CD146 alternatively called melanoma cell adhesion molecule (MCAM), is a biomarker and therapeutic target of clinical significance. It is found on different cells including the endothelial cells and lymphocytes which participate in heterotypic and homotypic ligand-receptor. This review concentrated on the CD146 expression T cells (or lymphocytes) centering on Treg in lung cancer. Here, we have also considered the vigorous investigation of CD146 mainly acknowledged new roles, essential mechanisms and clinical implications of CD146 in cancer. CD146 has progressively become a significant molecule, particularly recognized as a novel biomarker, prognosis and therapy for cancer. Hence, targeting CD146 expression by utilization of methanol extracts of Calotropis procera leaf may be useful for the treatment of carcinogenesis.

ImmunoPET imaging of CD38 expression in hepatocellular carcinoma using 64Cu-labeled daratumumab

CD38 is expressed on the surface of many immune cells, which are closely associated with antitumor immunity and immune tolerance of tumor cells. Therefore, monitoring CD38 expression has gained great attention for tracking the progression of tumors and cancer treatment. Herein, we aim to develop a PET tracer using an anti-CD38 monoclonal antibody (daratumumab) to monitor CD38 expression in hepatocellular carcinoma (HCC). In this study, daratumumab was radiolabeled with ⁶⁴Cu (t_1/2=12.7 h) to obtain ⁶⁴Cu-NOTA-daratumumab. Relative CD38 expression in HepG2 and Huh7 HCC cell lines was assessed using western blot. The specificity of ⁶⁴Cu-NOTA-daratumumab to both cell lines was examined using an in vitro cell-binding assay. PET imaging in subcutaneous models of HCC was performed to evaluate the capability and specificity of ⁶⁴Cu-NOTA-daratumumab to target CD38 in vivo. Region-of-interest analysis and ex vivo biodistribution were performed to verify the tracer targeting capability of CD38. Through cellular studies of two HCC cell lines, CD38 expression was found to be higher in HepG2 and minimal in Huh7 cells. ⁶⁴Cu-NOTA-daratumumab showed relatively high affinity to CD38 (K_a=18.21 ± 1.74 nM), while the affinity of Huh7 was in the micromolar range for daratumumab binding to the cells (K_a=3.98 ± 0.87 μM). At 48 h post-injection, PET imaging of subcutaneous models with ⁶⁴Cu-NOTA-daratumumab revealed tumor uptakes of 12.23 ± 2.4 and 2.7 ± 1.2 %ID/g for HepG2 and Huh7, respectively (n=4), which correlated well with relative CD38 expression of the cells. Moreover, the ⁶⁴Cu-NOTA-IgG nonspecific analogue showed a significantly lower uptake in HepG2 subcutaneous model in mice, suggesting a specific binding of daratumumab with CD38 in vivo. Our cellular studies and PET imaging confirmed the capability and specificity of ⁶⁴Cu-NOTA-daratumumab for the imaging of CD38 in murine models of HCC. This study supports our claim that ⁶⁴Cu-NOTA-daratumumab is an effective PET tracer for the non-invasive evaluation of CD38 expression and sensitive detection of CD38-positive tumor lesions in HCC.

Synthesis and evaluation of 64Cu-radiolabeled NOTA-cetuximab (64Cu-NOTA-C225) for immuno-PET imaging of EGFR expression

Objective

Epidermal growth factor receptor (EGFR) is overexpressed in a wide variety of solid tumors, serving as a well-characterized target for cancer imaging or therapy. In this study, we aimed to design and synthesize a radiotracer, ⁶⁴Cu-NOTA-C225, targeting EGFR for tumor positron emission tomography (PET) imaging.

Methods

Cetuximab (C225) was conjugated to a bifunctional chelator, p-isothiocyanatobenzyl-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), and further radiolabeled with copper-64 for PET imaging. ⁶⁴Cu-NOTA-IgG and Cy5.5-C225 were also synthesized as control probes. A431 and A549 mouse models were established for micro-PET and/or near-infrared fluorescence (NIRF) imaging.

Results

⁶⁴Cu-NOTA-C225 exhibited stability in vivo and in vitro up to 24 h and 50 h post-injection, respectively. A431 tumors with average standard uptake values (SUVs) of 5.61±0.69, 6.68±1.14, 7.80±1.51 at 6, 18 and 36 h post-injection, respectively, which were significantly higher than that of moderate EGFR expressing tumors (A549), with SUVs of 0.89±0.16, 4.70±0.81, 2.01±0.50 at 6, 18 and 36 h post-injection, respectively. The expression levels of A431 and A549 were confirmed by western blotting. Additionally, the tracer uptake in A431 tumors can be blocked by unlabeled cetuximab, suggesting that tracer uptake by tumors was receptor-mediated. Furthermore, NIRF imaging using Cy5.5-C225 showed that the fluorescence intensity in tumors increased with time, with a maximal intensity of 8.17E+10 (p/s/cm²/sr)/(μW/cm²) at 48 h post-injection, which is consistent with the paradigm from micro-PET imaging in A431 tumor-bearing mice.

Conclusions

The ⁶⁴Cu-NOTA-C225 PET imaging may be able to specifically and sensitively differentiate tumor models with different EGFR expression levels. It offers potentials as a PET radiotracer for imaging of tracer EGFR-positive tumors.

CD146-Targeted Multimodal Image-Guided Photoimmunotherapy of Melanoma

For melanoma resistant to molecularly targeted therapy and immunotherapy, new treatment strategies are urgently needed. A molecularly targeted theranostic pair may thus be of importance, where the diagnostic probe facilitates patient stratification and the therapeutic companion treats the selected cases. For this purpose, flow cytometry is used to assess the CD146 level in melanoma cells. Based on YY146, a CD146-specific monoclonal antibody, an imaging probe 89Zr-Df-YY146 is synthesized and its diagnostic performance is evaluated by positron emission tomography (PET) imaging. Furthermore, a photoimmunotherapy (PIT) agent IR700-YY146 is developed and the therapeutic effect of IR700-YY146 PIT is assessed comprehensively. CD146 is highly expressed in A375 and SK-MEL-5 cells. 89Zr-Df-YY146 PET readily detects CD146-positive A375 melanomas. Tumor accumulation of 89Zr-Df-YY146 peaks at 72 h with an uptake value of 26.48 ± 3.28%ID g-1, whereas the highest uptake of the nonspecific 89Zr-Df-IgG is 4.80 ± 1.75%ID g-1. More importantly, IR700-YY146 PIT effectively inhibits the growth of A375 tumors, owing to production of reactive oxygen species, decreased glucose metabolism, and reduced expression of CD146. To conclude, 89Zr-Df-YY146 and IR700-YY146 are a promising theranostic pair with the former revealing CD146 expression in melanoma as a PET probe and the latter specifically treating CD146-positive melanoma as an effective PIT agent.