CD146-Targeted Multimodal Image-Guided Photoimmunotherapy of Melanoma

Preclinical ImmunoPET Imaging Using a Zr-89-Labeled Anti-CD146 Monoclonal Antibody for Diagnosis of Melanoma

The aim of this study was to evaluate the preclinical efficacy of [89Zr]Zr-DFO-Ab253 as a novel positron emission tomography (PET) tracer for CD146-positive malignant melanoma imaging. Considering the high expression of CD146 in malignant melanoma, this study investigated the effect of different CD146 expression levels on the tumor uptake of [89Zr]Zr-DFO-Ab253. CD146 selectivity was investigated by using the CD146-positive human melanoma cell A375 and the CD146-negative human alveolar epithelial cell A549. The cell uptake of [89Zr]Zr-DFO-Ab253 tracers was investigated, and receptor-binding affinities were measured by radioactive enzyme-linked immunosorbent assay. Biodistribution studies and micro-PET imaging of the radiotracers were performed on mice bearing A375 and A549 xenografts under baseline and blocking conditions. An immunohistochemical test was performed using A375 and A549 tissue sections for CD146 expression level analysis. [89Zr]Zr-DFO-Ab253 was obtained with a high radiochemical yield (87.86 ± 4.66%) and a satisfactory radiochemical purity (>98.0%). The specificity and affinity of [89Zr]Zr-DFO-Ab253 were confirmed in melanoma A375 cells and in vivo PET imaging of A375 tumor models. [89Zr]Zr-DFO-IgG and A549 lung tumors were prepared as control radiotracers and negative models to verify the specificity of [89Zr]Zr-DFO-Ab253 on CD146. [89Zr]Zr-DFO-Ab253 has a Kd of 4.01 ± 0.50 nM. PET imaging and biodistribution showed a higher uptake of [89Zr]Zr-DFO-Ab253 in A375 melanomas than that in A549 tumors (42.1 ± 4.04% vs 7.87 ± 1.30% ID/g at 120 h, P < 0.05). A low tumor uptake of [89Zr]Zr-DFO-IgG was observed with uptakes of 1.91 ± 0.41 and 2.80 ± 0.14 ID%/g when blocked at 120 h. The radiation-absorbed dose was calculated to be 0.13 mSv/MBq. This study demonstrates the synthesis and preclinical evaluation of [89Zr]Zr-DFO-Ab253 and indicates that the novel tracer has promising applications in malignant melanoma-specific PET imaging because of its high uptake and long-time retention in malignant melanoma. It also provides feasibility for the development of integrated molecular probes for diagnosis and treatment based on the CD146 target.

The fusion of light and immunity: Advancements in photoimmunotherapy for melanoma

Metastatic melanoma is an aggressive skin cancer with high mortality and recurrence rates. Despite the clinical success of recent immunotherapy approaches, prevailing resistance rates necessitate the continued development of novel therapeutic options. Photoimmunotherapy (PIT) is emerging as a promising immunotherapy strategy that uses photodynamic therapy (PDT) to unleash systemic immune responses against tumor sites while maintaining the superior tumor-specificity and minimally invasive nature of traditional PDT. In this review, we discuss recent advances in PIT and strategies for the management of melanoma using PIT. PIT can strongly induce immunogenic cell death, inviting the concomitant application of immune checkpoint blockade or adoptive cell therapies. PIT can also be leveraged to selectively remove the suppressive immune populations associated with immunotherapy resistance. The modular nature of PIT therapy design combined with the potential for patient-specific antigen selection or drug co-delivery makes PIT an alluring option for future personalized melanoma care.

Construction and preclinical evaluation of a zirconium-89 labelled monoclonal antibody targeting PD-L2 in lung cancer

OBJECTIVES

The aim of this study was to design a novel tracer targeting programmed cell death-ligand 2 (PD-L2) to dynamically monitor PD-L2 expression and perform preclinical screening to identify patients who may benefit from immune checkpoint inhibitor therapy (ICI) therapy.

METHODS

89Zr labelling of DFO-conjugated PD-L2 antibody (ATL2) was carried out in Na2CO3 buffer at pH 7 (37 °C, 1 h). In vitro stability was analysed using radio-thin layer chromatography (radio-TLC). The affinity of [89Zr]Zr-DFO-ATL2 was evaluated by radio-ELISA. Cell uptake, pharmacokinetic, and biodistribution experiments were used to evaluate the biological properties. Micro-PET/CT imaging with [89Zr]Zr-DFO-ATL2 was conducted at different time points. Immunohistochemical and HE staining studies were carried out using tumour tissues from tumour-bearing mice.

RESULTS

The radiochemical yield of [89Zr]Zr-DFO-ATL2 was 65.6 ± 3.9%, and the radiochemical purity (RCP) of the tracer was greater than 99%. The tracer maintained relatively high stability and had a high affinity for the PD-L2 protein (Kd = 31.85 nM, R2 = 0.94). The uptake of [89Zr]Zr-DFO-ATL2 in A549-PD-L2 cells was higher than that in A549 cells at each time point. Micro-PET/CT showed significant uptake in the tumour region of mice bearing tumours derived from A549-PD-L2 (SUVmax = 3.53 ± 0.09 at 96 h) and H2228 (SUVmax = 2.30 ± 0.12 at 48 h) cells.

CONCLUSION

The high tumour uptake at early imaging time points demonstrates the feasibility of applying [89Zr]Zr-DFO-ATL2 to image PD-L2 expression in tumours and is encouraging for further clinical application in the screening of patients who may benefit from ICI therapy.

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.

In vivo imaging of acute physiological responses after treatment of cancer with near-infrared photoimmunotherapy

PURPOSE

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer phototherapy using an antibody-photosensitizer conjugate (Ab-IR700). By NIR light irradiation, Ab-IR700 forms a water-insoluble aggregation on the plasma membrane of cancer cells, leading to lethal membrane damage of cancer cells with high selectivity. However, IR700 produces singlet oxygen, which induces non-selective inflammatory responses such as edema in normal tissues around the tumor. Understanding such treatment-emergent responses is important to minimize side effects and improve clinical outcomes. Thus, in this study, we evaluated physiological responses during NIR-PIT by magnetic resonance imaging (MRI) and positron emission tomography (PET).

PROCEDURES

Ab-IR700 was intravenously injected into tumor-bearing mice with two tumors on the right and left sides of the dorsum. At 24 h after injection, a tumor was irradiated with NIR light. Edema formation was examined by T1/T2/diffusion-weighted MRI and inflammation was investigated by PET with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG). Because inflammation can increase vascular permeability via inflammatory mediators, we evaluated changes in oxygen levels in tumors using a hypoxia imaging probe, [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO).

RESULTS

The uptake of [¹⁸F]FDG in the irradiated tumor was significantly decreased compared to the control tumor, indicating the impairment of glucose metabolism induced by NIR-PIT. MRI and [¹⁸F]FDG-PET images showed that inflammatory edema with [¹⁸F]FDG accumulation was present in the surrounding normal tissues of the irradiated tumor. Furthermore, [¹⁸F]FMISO accumulation in the center of the irradiated tumor was relatively low, indicating the enhancement of oxygen supply due to increased vascular permeability. In contrast, high [¹⁸F]FMISO accumulation was observed in the peripheral region, indicating enhancement of hypoxia in the region. This could be because inflammatory edema was formed in the surrounding normal tissues, which blocked blood flow to the tumor.

CONCLUSIONS

We successfully monitored inflammatory edema and changes in oxygen levels during NIR-PIT. Our findings on the acute physiological responses after light irradiation will help to develop effective measures to minimize the side effects in NIR-PIT.

Claudin18.2-targeted cancer theranostics

Claudin 18.2 (CLDN18.2) is an emerging target for the treatment of CLDN18.2-expressing cancers such as gastric and pancreatic cancers. Cell and antibody therapies targeting CLDN18.2 are under intensive clinical trials. In this setting, how to efficiently and specifically detect CLDN18.2 expression before and after the therapies is a clinical challenge. In recent years, molecular imaging with radiolabeled antibodies or antibody fragments have shown promise in noninvasively annotating antigen expression across the body. In this Perspective, we will bring together the most recent progress on CLDN18.2-targeted imaging and therapy of solid tumors.

Near Infrared Photoimmunotherapy: A Review of Recent Progress and Their Target Molecules for Cancer Therapy

Near infrared photoimmunotherapy (NIR-PIT) is a newly developed molecular targeted cancer treatment, which selectively kills cancer cells or immune-regulatory cells and induces therapeutic host immune responses by administrating a cancer targeting moiety conjugated with IRdye700. The local exposure to near-infrared (NIR) light causes a photo-induced ligand release reaction, which causes damage to the target cell, resulting in immunogenic cell death (ICD) with little or no side effect to the surrounding normal cells. Moreover, NIR-PIT can generate an immune response in distant metastases and inhibit further cancer attack by combing cancer cells targeting NIR-PIT and immune regulatory cells targeting NIR-PIT or other cancer treatment modalities. Several recent improvements in NIR-PIT have been explored such as catheter-driven NIR light delivery, real-time monitoring of cancer, and the development of new target molecule, leading to NIR-PIT being considered as a promising cancer therapy. In this review, we discuss the progress of NIR-PIT, their mechanism and design strategies for cancer treatment. Furthermore, the overall possible targeting molecules for NIR-PIT with their application for cancer treatment are briefly summarised.

Development and Characterization of Nanobody-Derived CD47 Theranostic Pairs in Solid Tumors

Overexpression of CD47 is frequently observed in various types of human malignancies, inhibiting myeloid-mediated elimination of tumor cells and affecting the prognosis of cancer patients. By mapping biomarker expression, immuno-positron emission tomography has been increasingly used for patient screening and response monitoring. By immunization alpacas with recombinant human CD47, we prepared a CD47-targeting nanobody C2 and developed [⁶⁸Ga]Ga-NOTA-C2, followed by an exploration of the diagnostic value in CD47-expressing tumor models including gastric-cancer patient-derived xenograft models. By fusing C2 to an albumin binding domain (ABD), we synthesized ABDC2, which had increased in vivo half-life and improved targeting properties. We further labeled ABDC2 with ⁶⁸Ga/⁸⁹Zr/¹⁷⁷Lu to develop radionuclide theranostic pairs and evaluated the pharmacokinetics and theranostic efficacies of the agents in cell- and patient-derived models. Both C2 and ABDC2 specifically reacted with human CD47 with a high K _D value of 23.50 and 84.57 pM, respectively. [⁶⁸Ga]Ga-NOTA-C2 was developed with high radiochemical purity (99 >%, n = 4) and visualized CD47 expression in the tumors. In comparison to the rapid renal clearance and short half-life of [⁶⁸Ga]Ga-NOTA-C2, both [⁶⁸Ga]Ga-NOTA-ABDC2 and [⁸⁹Zr]Zr-DFO-ABDC2 showed prolonged circulation and increased tumor uptake, with the highest uptake of [⁸⁹Zr]Zr-DFO-ABDC2 occurring at 72 h post-injection. Moreover, [¹⁷⁷Lu]Lu-DOTA-ABDC2 radioimmunotherapy suppressed the tumor growth but was associated with toxicity, warranting further optimization of the treatment schedules. Taken together, we reported a series of nanobody-derived CD47-targeted agents, of which [⁶⁸Ga]Ga-NOTA-C2 and [⁸⁹Zr]Zr-DFO-ABDC2 are readily translatable. Optimization and translation of CD47-targeted theranostic pair may provide new prospects for CD47-targeted management of solid tumors.

Development and comparison of 68Ga/18F/64Cu-labeled nanobody tracers probing Claudin18.2

Claudin 18.2 (CLDN18.2) is an emerging target for the treatment of gastric cancers. We aim to develop tracers to image the expression of CLDN18.2. A humanized nanobody targeting CLDN18.2 (clone hu19V3) was produced and labeled with ⁶⁸Ga, ⁶⁴Cu, and ¹⁸F. The tracers were investigated in subcutaneous and metastatic models established using two different mouse types (nude and Balb/c mice) and two different cell lines (CHO-CLDN18.2 and CT26-CLDN18.2). Gastric cancer patient-derived xenograft (PDX) models were further established for validation experiments. Three novel CLDN18.2-targeted tracers (i.e., [⁶⁸Ga]Ga-NOTA-hu19V3, [⁶⁴Cu]Cu-NOTA-hu19V3, and [¹⁸F]F-hu19V3) were developed with good radiochemical yields and excellent radiochemical purities. [⁶⁸Ga]Ga-NOTA-hu19V3 immuno-positron emission tomography (immunoPET) rapidly delineated subcutaneous CHO-CLDN18.2 lesions and CT26-CLDN18.2 tumors, as well as showing excellent diagnostic value in PDX models naturally expressing CLDN18.2. While [⁶⁸Ga]Ga-NOTA-hu19V3 had high kidney accumulation, [⁶⁴Cu]Cu-NOTA-hu19V3 showed reduced kidney accumulation and improved image contrast at late time points. Moreover, [¹⁸F]F-hu19V3 was developed via click chemistry reaction under mild conditions and precisely disseminated CHO-CLDN18.2 lesions in the lungs. Furthermore, region of interest analysis, biodistribution study, and histopathological staining results correlated well with the in vivo imaging results. Taken together, immunoPET imaging with the three tracers can reliably visualize CLDN18.2 expression.

Near-infrared photoimmunotherapy: design and potential applications for cancer treatment and beyond

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment modality based on a target-specific photosensitizer conjugate (TSPC) composed of an NIR phthalocyanine photosensitizer and an antigen-specific recognition system. NIR-PIT has predominantly been used for targeted therapy of tumors via local irradiation with NIR light, following binding of TSPC to antigen-expressing cells. Physical stress-induced membrane damage is thought to be a major mechanism underlying NIR-PIT-triggered photokilling. Notably, NIR-PIT can rapidly induce immunogenic cell death and activate the adaptive immune response, thereby enabling its combination with immune checkpoint inhibitors. Furthermore, NIR-PIT-triggered “super-enhanced permeability and retention” effects can enhance drug delivery into tumors. Supported by its potential efficacy and safety, NIR-PIT is a rapidly developing therapeutic option for various cancers. Hence, this review seeks to provide an update on the (i) broad range of target molecules suitable for NIR-PIT, (ii) various types of receptor-selective ligands for designing the TSPC “magic bullet,” (iii) NIR light parameters, and (iv) strategies for enhancing the efficacy of NIR-PIT. Moreover, we review the potential application of NIR-PIT, including the specific design and efficacy in 19 different cancer types, and its clinical studies. Finally, we summarize possible NIR-PIT applications in noncancerous conditions, including infection, pain, itching, metabolic disease, autoimmune disease, and tissue engineering.

Hydrogen sulfide activatable metal-organic frameworks for Fluorescence Imaging-Guided Photodynamic Therapy of colorectal cancer

Photodynamic therapy (PDT) is a promising alternative and palliative therapeutic strategy for colorectal cancer (CRC). A novel photosensitizer with higher selectivity for CRC and fewer side effects is vital for clinical application. Given that the overexpression of hydrogen sulfide (H₂S) in CRC, it is expected to provide a selective stimulus for activatable photosensitizers that in respond to the specific microenvironment. Herein, we report a novel development of metal-organic frameworks (MOFs) composed of meso-Tetra (4-carboxyphenyl) porphine (TCPP) and ferric ion (Fe³⁺) through a facile one-pot process. Experiments both in vitro and in vivo reveal that the MOF is capable of depredating in response to the high content of H₂S in tumor microenvironment of CRC. Accompanying with the degradation and release of TCPP, the fluorescence and photosensitivity effect is switched from “off” to “on”, enabling the MOF to serve as a H₂S activatable nano-photosensitizer for real-time fluorescence imaging-guided and targeted PDT of CRC.

Emerging Biomaterials Imaging Antitumor Immune Response

Immunotherapy is one of the most promising clinical modalities for the treatment of malignant tumors and has shown excellent therapeutic outcomes in clinical settings. However, it continues to face several challenges, including long treatment cycles, high costs, immune-related adverse events, and low response rates. Thus, it is critical to predict the response rate to immunotherapy by using imaging technology in the preoperative and intraoperative. Here, the latest advances in nanosystem-based biomaterials used for predicting responses to immunotherapy via the imaging of immune cells and signaling molecules in the immune microenvironment are comprehensively summarized. Several imaging methods, such as fluorescence imaging, magnetic resonance imaging, positron emission tomography imaging, ultrasound imaging, and photoacoustic imaging, used in immune predictive imaging, are discussed to show the potential of nanosystems for distinguishing immunotherapy responders from nonresponders. Nanosystem-based biomaterials aided by various imaging technologies are expected to enable the effective prediction and diagnosis in cases of tumors, inflammation, and other public diseases.

Combinatory therapy of MRP1-targeted photoimmunotherapy and liposomal doxorubicin promotes the antitumor effect for chemoresistant small cell lung cancer

Small cell lung cancer (SCLC), considered a mortal recalcitrant cancer, is a severe healthcare issue because of its poor prognosis, early metastasis, drug resistance and limited clinical treatment options. In our previous study, we established a MRP1-targeted antibody-IR700 system (Mab-IR700) for near infrared photoimmunotherapy (NIR-PIT) which exhibited a promising therapeutic effect on drug resistant H69AR cells both in vitro and in vivo, though the tumor growth suppression effect did not last long with a single round of PIT treatment. To achieve a better anticancer effect, we have combined Mab-IR700-mediated NIR-PIT with liposomal doxorubicin (Doxil®) and investigated the in vitro and in vivo cytotoxicity by using a H69AR/3T3 cell co-culture model in which 3T3 cells were used to mimic stromal cells. Cytotoxicity experiments demonstrated the specificity of Mab-IR700 to H69AR cells, while cytotoxicity and flow cytometry experiments confirmed that H69AR cells were doxorubicin-resistant. Compared with Mab-IR700-mediated PIT or Doxil-mediated chemotherapy, the combination therapy exhibited the best cell killing effect in vitro and superior tumor growth inhibition and survival prolongation effect in vivo. Super enhanced permeability and retention (SUPR) effect was observed in both co-culture spheroids and tumor-bearing mice. Owing to an approximately 9-fold greater accumulation of Doxil within the tumors, NIR-PIT combined with Doxil resulted in enhanced antitumor effects compared to NIR-PIT alone. This photoimmunochemotherapy is a practical strategy for the treatment of chemoresistant SCLC and should be further investigated for clinical translation.

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.

Nectin-4-targeted immunoSPECT/CT imaging and photothermal therapy of triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is more prone to distant metastasis and visceral recurrence in comparison to other breast cancer subtypes, and is related to dismal prognosis. Nevertheless, TNBC has an undesirable response to targeted therapies. Therefore, to tackle the huge challenges in the diagnosis and treatment of TNBC, Nectin-4 was selected as a theranostic target because it was recently found to be highly expressed in TNBC. We developed anti-Nectin-4 monoclonal antibody (mAbNectin-4)-based theranostic pair, 99mTc-HYNIC-mAbNectin-4 and mAbNectin-4-ICG. 99mTc-HYNIC-mAbNectin-4 was applied to conduct immuno-single photon emission computed tomography (SPECT) for TNBC diagnosis and classification, and mAbNectin-4-ICG to mediate photothermal therapy (PTT) for relieving TNBC tumor growth.

METHODS

Nectin-4 expression levels of breast cancer cells (MDA-MB-468: TNBC cells; and MCF-7, non-TNBC cells) were proved by western blot, flow cytometry, and immunofluorescence imagning. Cell uptake assays, SPECT imaging, and biodistribution were performed to evaluate Nectin-4 targeting of 99mTc-HYNIC-mAbNectin-4. A photothermal agent (PTA) mAbNectin-4-ICG was generated and characterized. In vitro photothermal therapy (PTT) mediated by mAbNectin-4-ICG was conducted under an 808 nm laser. Fluorescence (FL) imaging was performed for mAbNectin-4-ICG mapping in vivo. In vivo PTT treatment effects on TNBC tumors and corresponding systematic toxicity were evaluated.

RESULTS

Nectin-4 is overexpressed in MDA-MB-468 TNBC cells, which could specifically uptake 99mTc-HYNIC-mAbNectin-4 with high targeting in vitro. The corresponding immunoSPECT imaging demonstrated exceptional performance in TNBC diagnosis and molecular classification. mAbNectin-4-ICG exhibited favourable biocompatibility, photothermal effects, and Nectin-4 targeting. FL imaging mapped biodistribution of mAbNectin-4-ICG with excellent tumor-targeting and retention in vivo. Moreover, mAbNectin-4-ICG-mediated PTT provided advanced TNBC tumor destruction efficiency with low systematic toxicity.

CONCLUSION

mAbNectin-4-based radioimmunoimaging provides visualization tools for the stratification and diagnosis for TNBC, and the corresponding mAbNectin-4-mediated PTT shows a powerful anti-tumor effect. Our findings demonstrate that this Nectin-4 targeting strategy offers a simple theranostic platform for TNBC.

A novel Pyroptosis-related long non-coding RNA signature for predicting the prognosis and immune landscape of head and neck squamous cell carcinoma

BACKGROUND

Pyroptosis plays an essential function in carcinogenesis and the antitumor immune response. Herein, we constructed a pyroptosis-related long noncoding RNA (prLncRNA) signature to predict therapeutic effects and outcomes for head and neck squamous cell carcinoma (HNSCC) patients.

METHODS

Patients obtained from the TCGA-HNSC project were divided randomly into the training as well as the validation sets at a ratio of 7:3. A novel prognostic prLncRNA signature was constructed from the results of the training set using the least absolute shrinkage and selection operation. The medium value was used as the basis for categorizing all HNSCC patients into a low- or high-risk cohort. Cox regression and Kaplan-Meier (KM) survival analyses were executed to estimate the prognostic value. We also evaluated the functional enrichment, tumor microenvironment, immune cell infiltration, and the sensitivity to chemotherapy and immunotherapy between the high- and low-risk cohorts.

RESULTS

Nineteen prognostic prlncRNAs were identified to establish the prognostic signature. Multivariate Cox regression and KM survival analyses confirmed that this prlncRNA signature might serve as an independent prognostic indicator of patient survival, which was subsequently confirmed using a validating dataset. Multiple ROC curves indicated the prlncRNA signature presented a more predictive power than clinicopathological factors (age, sex, tumor grade, and tumor stage). GO, KEGG, and GSEA enrichment analysis disclosed several immune-related pathways which appeared to be enhanced in the low-risk cohort. ESTIMATE, CIBERSORT, and ssGSEA algorithms indicated considerable differences in the tumor microenvironment and immune cell infiltration in the low- and high-risk cohorts. Furthermore, the low-risk cohort was predicted to achieve a better response to immunotherapeutic drugs, while in contrast, the high-risk cohort would be more sensitive to chemotherapy drugs.

CONCLUSIONS

Our findings robustly demonstrate that our constructed prlncRNA signature could serve as an efficient indicator of prognosis, immunotherapy response, and chemosensitivity for HNSCC patients.

Targeted photoimmunotherapy for cancer

Photodynamic therapy (PDT) is a clinically approved procedure that can exert a curative action against malignant cells. The treatment implies the administration of a photoactive molecular species that, upon absorption of visible or near infrared light, sensitizes the formation of reactive oxygen species. These species are cytotoxic and lead to tumor cell death, damage vasculature, and induce inflammation. Clinical investigations demonstrated that PDT is curative and does not compromise other treatment options. One of the major limitations of the original method was the low selectivity of the photoactive compounds for malignant over healthy tissues. The development of conjugates with antibodies has endowed photosensitizing molecules with targeting capability, so that the compounds are delivered with unprecedented precision to the site of action. Given their fluorescence emission capability, these supramolecular species are intrinsically theranostic agents.

CD29 targeted near-infrared photoimmunotherapy (NIR-PIT) in the treatment of a pigmented melanoma model

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that utilizes an antibody-photoabsorber-conjugate (AbPC) combined with NIR light. The AbPC is injected and binds to the tumor whereupon NIR light irradiation causes a photochemical reaction that selectively kills cancer cells. NIR-PIT is ideal for surface-located skin cancers such as melanoma. However, there is concern that the pigment in melanoma lesions could interfere with light delivery, rendering treatment ineffective. We investigated the efficacy of CD29- and CD44-targeted NIR-PIT (CD29-PIT and CD44-PIT, respectively) in the B16 melanoma model, which is highly pigmented. While CD29-PIT and CD44-PIT killed B16 cells invitro and invivo, CD29-PIT suppressed tumor growth more efficiently. Ki67 expression showed that cells surviving CD29-PIT were less proliferative, suggesting that CD29-PIT was selective for more proliferative cancer cells. CD29-PIT did not kill immune cells, whereas CD44-PIT killed both T and NK cells and most myeloid cells, including DCs, which could interfere with the immune response to NIR-PIT. The addition of anti-CTLA4 antibody immune checkpoint inhibitor (ICI) to CD29-PIT increased the infiltration of CD8 T cells and enhanced tumor suppression with prolonged survival. Such effects were less prominent when the anti-CTLA4 ICI was combined with CD44-PIT. The preservation of immune cells in the tumor microenvironment (TME) after CD29-PIT likely led to a better response when combined with anti-CTLA4 treatment. We conclude that NIR-PIT can be performed in pigmented melanomas and that CD29 is a promising target for NIR-PIT, which is amenable to combination therapy with other immunotherapies.

Annotating CD38 Expression in Multiple Myeloma with [18F]F-Nb1053

Noninvasive diagnosis of multiple myeloma (MM) is a clinical challenge. CD38 is an established biomarker for MM, and the development of CD38-targeted radiotracers may improve the management of MM. By taking the advantages of bioorthogonal click chemistry, a nanobody (i.e., Nb1053-LLQS) specific for CD38 was successfully labeled with ¹⁸F. The diagnostic efficacy and specificity of the developed tracer (i.e., [¹⁸F]F-Nb1053) were evaluated by immuno-positron emission tomography (immunoPET) imaging in disseminated MM.1S-bearing models. [¹⁸F]F-Nb1053 was developed with high radiochemical purity (>98%) and excellent immunoreactivity. [¹⁸F]F-Nb1053 immunoPET successfully delineated disseminated MM lesions in preclinical MM models. The uptake in the humerus, femur, and tibia was 1.42 ± 0.50%ID/g, 1.35 ± 0.53%ID/g, and 1.48 ± 0.67%ID/g (n = 6), respectively. Tumor uptake of [¹⁸F]F-Nb1053 decreased after daratumumab premedication, indicating the superior specificity of the reported probe. This work successfully developed a novel CD38-specific probe [¹⁸F]F-Nb1053 that may potentially optimize the management of MM upon clinical translation.

Annotating BCMA Expression in Multiple Myelomas

B cell maturation antigen (BCMA) is a promising theranostic target for multiple myeloma (MM). BCMA-targeted therapeutics, such as antibody-drug conjugates and chimeric antigen receptor T-cell immunotherapies, are rapidly reshaping the treatment landscape of MM. Along with the progress, a critical challenge is to noninvasively visualize the dynamic change of BCMA for a better-personalized prescription of the above-mentioned therapeutics. We aim to develop immuno-positron emission tomography (immunoPET) imaging strategies to visualize BCMA expression and realize target-specific diagnosis of MM in the work. A series of BCMA-targeting nanobodies were produced and two of them were successfully labeled with gallium-68 (⁶⁸Ga). MM models were established using MM.1S cell line and NOD-Prkdc^em26Cd52Il2rg^em26Cd22/Nju mice. The diagnostic efficacies of the developed probes (i.e., [⁶⁸Ga]Ga-NOTA-MMBC2 and [⁶⁸Ga]Ga-NOTA-MMBC3) were investigated in disseminated MM models by immunoPET imaging, region of interest analysis on PET images, biodistribution study, and histopathological staining study. [⁶⁸Ga]Ga-NOTA-MMBC2 and [⁶⁸Ga]Ga-NOTA-MMBC3 were developed with radiochemical purities of >99%. ImmunoPET imaging with either [⁶⁸Ga]Ga-NOTA-MMBC2 or [⁶⁸Ga]Ga-NOTA-MMBC3 precisely visualized BCMA expression and delineated MM lesions throughout the bone marrows. Moreover, [⁶⁸Ga]Ga-NOTA-MMBC3 immunoPET successfully detected remnant MM after treatment with daratumumab, a prescription medicine used to treat MM. The immunoPET imaging data correlated well with the biodistribution and immunohistochemistry staining results. The work successfully developed two state-of-the-art BCMA-targeted radiotracers for annotating BCMA expression and diagnosing MM. Translational studies interpreting the diagnostic efficacies of the immunoPET radiotracers are warranted.

Comparison of low-molecular-weight ligand and whole antibody in prostate-specific membrane antigen targeted near-infrared photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) is a cancer phototherapy that uses antibody-IR700 conjugate (Ab-IR700) and NIR light. Ab-IR700 forms aggregates on the plasma membranes of targeted cancer cells after light exposure, inducing lethal physical damage within the membrane. Low-molecular-weight (LMW) ligands are candidate targeting moieties instead of antibodies, but whether LMW-IR700 conjugates induce cell death by aggregation, the same mechanism as Ab-IR700, is unknown. Thus, we investigated differences in cytotoxicity and mechanisms between LMW-IR700 and Ab-IR700 targeting prostate-specific membrane antigen (PSMA). Both conjugates decreased cell viability to the same degree after light irradiation, but different morphological changes were observed in PSMA-positive LNCaP cells by microscopy. Cell swelling and bleb formation were induced by Ab-IR700, but only swelling was observed in cells treated with LMW-IR700, suggesting the cells were damaged via different cytotoxic mechanisms. However, LMW-IR700 induced bleb formation, a hallmark of NIR-PIT with Ab-IR700, when singlet oxygen was quenched or LMW-IR700 was localized only on the plasma membrane. Moreover, the water-soluble axial ligands of LMW-IR700 were cleaved, consistent with previous reports on Ab-IR700. Thus, the main cytotoxic mechanisms of Ab-IR700 and LMW-IR700 differ, although LMW-IR700 on the plasma membrane can cause aggregation-mediated cytotoxicity as well as Ab-IR700.

Near infrared photoimmunotherapy of cancer; possible clinical applications

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that uses an antibody-photo-absorber conjugate (APC) composed of a targeting monoclonal antibody conjugated with a photoactivatable phthalocyanine-derivative dye, IRDye700DX (IR700). APCs injected into the body can bind to cancer cells where they are activated by local exposure to NIR light typically delivered by a NIR laser. NIR light alters the APC chemical conformation inducing damage to cancer cell membranes, resulting in necrotic cell death within minutes of light exposure. NIR-PIT selectivity kills cancer cells by immunogenic cell death (ICD) with minimal damage to adjacent normal cells thus, leading to rapid recovery by the patient. Moreover, since NIR-PIT induces ICD only on cancer cells, NIR-PIT initiates and activates antitumor host immunity that could be further enhanced when combined with immune checkpoint inhibition. NIR-PIT induces dramatic changes in the tumor vascularity causing the super-enhanced permeability and retention (SUPR) effect that dramatically enhances nanodrug delivery to the tumor bed. Currently, a worldwide Phase 3 study of NIR-PIT for recurrent or inoperable head and neck cancer patients is underway. In September 2020, the first APC and accompanying laser system were conditionally approved for clinical use in Japan. In this review, we introduce NIR-PIT and the SUPR effect and summarize possible applications of NIR-PIT in a variety of cancers.

Real-time cancer diagnosis of breast cancer using fluorescence lifetime endoscopy based on the pH

A biopsy is often performed for the diagnosis of cancer during a surgical operation. In addition, pathological biopsy is required to discriminate the margin between cancer tissues and normal tissues in surgical specimens. In this study, we presented a novel method for discriminating between tumor and normal tissues using fluorescence lifetime endoscopy (FLE). We demonstrated the relationship between the fluorescence lifetime and pH in fluorescein using the proposed fluorescence lifetime measurement system. We also showed that cancer could be diagnosed based on this relationship by assessing differences in pH based fluorescence lifetime between cancer and normal tissues using two different types of tumor such as breast tumors (MDA-MB-361) and skin tumors (A375), where cancer tissues have ranged in pH from 4.5 to 7.0 and normal tissues have ranged in pH from 7.0 to 7.4. To support this approach, we performed hematoxylin and eosin (H&E) staining test of normal and cancer tissues within a certain area. From these results, we showed the ability to diagnose a cancer using FLE technique, which were consistent with the diagnosis of a cancer with H&E staining test. In summary, the proposed pH-based FLE technique could provide a real time, in vivo, and in-situ clinical diagnostic method for the cancer surgical and could be presented as an alternative to biopsy procedures.

Cell Adhesion Molecules in Normal Skin and Melanoma

Cell adhesion molecules (CAMs) of the cadherin, integrin, immunoglobulin, and selectin protein families are indispensable for the formation and maintenance of multicellular tissues, especially epithelia. In the epidermis, they are involved in cell–cell contacts and in cellular interactions with the extracellular matrix (ECM), thereby contributing to the structural integrity and barrier formation of the skin. Bulk and single cell RNA sequencing data show that >170 CAMs are expressed in the healthy human skin, with high expression levels in melanocytes, keratinocytes, endothelial, and smooth muscle cells. Alterations in expression levels of CAMs are involved in melanoma propagation, interaction with the microenvironment, and metastasis. Recent mechanistic analyses together with protein and gene expression data provide a better picture of the role of CAMs in the context of skin physiology and melanoma. Here, we review progress in the field and discuss molecular mechanisms in light of gene expression profiles, including recent single cell RNA expression information. We highlight key adhesion molecules in melanoma, which can guide the identification of pathways and strategies for novel anti-melanoma therapies.

Tumor immunotherapy and multi-mode therapies mediated by medical imaging of nanoprobes

Immunotherapy is an effective tumor treatment strategy that has several advantages over conventional methods such as surgery, radiotherapy and chemotherapy. Studies show that multifunctional nanoprobes can achieve multi-mode image-guided multiple tumor treatment modes. The tumor cells killed by chemotherapies or phototherapies release antigens that trigger an immune response and augment the effects of tumor immunotherapy. Thus, combining immunotherapy and multifunctional nanoprobes can achieve early cancer diagnosis and treatment. In this review, we have summarized the current research on the applications of multifunctional nanoprobes in image-guided immunotherapy. In addition, image-guided synergistic chemotherapy/photothermal therapy/photodynamic therapy and immunotherapy have also been discussed. Furthermore, the application potential and clinical prospects of multifunctional nanoprobes in combination with immunotherapy have been assessed.

Near Infrared Photoimmunotherapy; A Review of Targets for Cancer Therapy

Simple Summary

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that uses an antibody-photoabsorber (IRDye700DX) conjugate (APC) that is activated by NIR light irradiation. A major benefit of NIR-PIT is that only APC-bound cancer cells that are exposed to NIR light are killed by NIR-PIT; thus, minimal damage occurs in adjacent normal cells. NIR-PIT has now been applied to many cancers expressing various cell-surface target proteins using monoclonal antibodies designed to bind to them. Moreover, NIR-PIT is not limited to tumor antigens but can also be used to kill specific host cells that create immune-permissive environments in which tumors grow. Moreover, multiple targets can be treated simultaneously with NIR-PIT using a cocktail of APCs. NIR-PIT has great potential to treat a wide variety of cancers by targeting appropriate tumor cells, immune cells, or both, and can be augmented by other immunotherapies.

Abstract

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that uses an antibody-photoabsorber (IRDye700DX) conjugate (APC) that is activated by NIR light irradiation. In September 2020, the first APC and laser system were conditionally approved for clinical use in Japan. A major benefit of NIR-PIT is that only APC-bound cancer cells that are exposed to NIR light are killed by NIR-PIT; thus, minimal damage occurs in adjacent normal cells. These early trials have demonstrated that in addition to direct cell killing, there is a significant therapeutic host immune response that greatly contributes to the success of the therapy. Although the first clinical use of NIR-PIT targeted epidermal growth factor receptor (EGFR), many other targets are suitable for NIR-PIT. NIR-PIT has now been applied to many cancers expressing various cell-surface target proteins using monoclonal antibodies designed to bind to them. Moreover, NIR-PIT is not limited to tumor antigens but can also be used to kill specific host cells that create immune-permissive environments in which tumors grow. Moreover, multiple targets can be treated simultaneously with NIR-PIT using a cocktail of APCs. NIR-PIT can be used in combination with other therapies, such as immune checkpoint inhibitors, to enhance the therapeutic effect. Thus, NIR-PIT has great potential to treat a wide variety of cancers by targeting appropriate tumor cells, immune cells, or both, and can be augmented by other immunotherapies.

Role of vitronectin-rich protein corona on tumor-specific siRNA delivery and transfection with lipid nanoparticles

Aim: To evaluate the role of vitronectin-enriched protein corona on systemic delivery of siRNA-encapsulated cationic lipid nanoparticles (LNPs) to αvβ3 integrin expressing solid tumors. Materials & methods: 1,2-Dioleoyl-3-trimethylammonium-propane LNPs were formulated, protein corona formed in nude mice serum and its impact on drug delivery were analyzed. Results: 1,2-Dioleoyl-3-trimethylammonium-propane-containing LNP led to enhanced recruitment of vitronectin and showed preferential transfection to αvβ3-expressed cells relative to controls. Upon systemic administration in mice, the LNPs accumulated in the αvβ3-expressing endothelial lining of the tumor blood vessels before reaching tumor cells. Conclusion: These results present an optimized LNP that selectively recruits endogenous proteins in situ to its corona which may lead to enhanced delivery and transfection in tissues of interest.

ImmunoPET imaging of human CD8+ T cells with novel 68Ga-labeled nanobody companion diagnostic agents

BACKGROUND

Although immunotherapy has revolutionized treatment strategies for some types of cancers, most patients failed to respond or obtain long-term benefit. Tumor-infiltrating CD8+ T lymphocytes are closely related to the treatment outcome and prognosis of patients. Therefore, noninvasive elucidation of both systemic and tumor-infiltrating CD8+ T lymphocytes is of extraordinary significance for patients during cancer immunotherapy. Herein, a panel of 68Ga-labeled Nanobodies were designed and investigated to track human CD8+ T cells in vivo through immuno-positron emission tomography (immunoPET).

RESULTS

Among the screened Nanobodies, SNA006a showed the highest binding affinity and specificity to both human CD8 protein and CD8+ cells in vitro, with the equilibrium dissociation constant (KD) of 6.4 × 10-10 M and 4.6 × 10-10 M, respectively. 68Ga-NOTA-SNA006 was obtained with high radiochemical yield and purity, and stayed stable for at least 1 h both in vitro and in vivo. Biodistribution and Micro-PET/CT imaging studies revealed that all tracers specifically concentrated in the CD8+ tumors with low accumulation in CD8- tumors and normal organs except the kidneys, where the tracer was excreted and reabsorbed. Notably, the high uptake of 68Ga-NOTA-SNA006a in CD8+ tumors was rapid and persistent, which reached 24.41 ± 1.00% ID/g at 1.5 h after intravenous injection, resulting in excellent target-to-background ratios (TBRs). More specifically, the tumor-to-muscle, tumor-to-liver, and CD8+ to CD8- tumor was 28.10 ± 3.68, 5.26 ± 0.86, and 19.58 ± 2.70 at 1.5 h, respectively. Furthermore, in the humanized PBMC-NSG and HSC-NPG mouse models, 68Ga-NOTA-SNA006a accumulated in both CD8+ tumors and specific tissues such as liver, spleen and lung where human CD8 antigen was overexpressed or CD8+ T cells located during immunoPET imaging.

CONCLUSIONS

68Ga-NOTA-SNA006a, a novel Nanobody tracer targeting human CD8 antigen, was developed with high radiochemical purity and high affinity. Compared with other candidates, the long retention time, low background, excellent TBRs of 68Ga-NOTA-SNA006a make it precisely track the human CD8+ T cells in mice models, showing great potential for immunotherapy monitoring and efficacy evaluation.

Molecular targets for anticancer therapies in companion animals and humans: what can we learn from each other?

Despite clinical successes in the treatment of some early stage cancers, it is undeniable that novel and innovative approaches are needed to aid in the fight against cancer. Targeted therapies offer the desirable feature of tumor specificity while sparing healthy tissues, thereby minimizing side effects. However, the success rate of translation of these therapies from the preclinical setting to the clinic is dramatically low, highlighting an important point of necessary improvement in the drug development process in the oncology field. The practice of a comparative oncology approach can address some of the current issues, by introducing companion animals with spontaneous tumors in the linear drug development programs. In this way, animals from the veterinary clinic get access to novel/innovative therapies, otherwise inaccessible, while generating robust data to aid therapy refinement and increase translational success. In this review, we present an overview of targetable membrane proteins expressed in the most well-characterized canine and feline solid cancers, greatly resembling the counterpart human malignancies. We identified particular areas in which a closer collaboration between the human and veterinary clinic would benefit both human and veterinary patients. Considerations and challenges to implement comparative oncology in the development of anticancer targeted therapies are also discussed.

ImmunoPET imaging of multiple myeloma with [68Ga]Ga-NOTA-Nb1053

PURPOSE

Multiple myeloma (MM) remains incurable and its diagnosis relies heavily on bone marrow aspiration and biopsy. CD38 is a glycoprotein highly specific for MM. Antibody therapeutics (e.g., daratumumab) targeting CD38 have shown encouraging efficacy in treating MM, either as a monotherapy agent or in combination with other regimens. However, efficient stratification of patients who might benefit from daratumumab therapy and timely monitoring of the therapeutic responses are still clinical challenges. This work aims to devise a CD38-targeted imaging strategy and assess its value in diagnosing MMs.

METHODS

By labeling a CD38-specific single domain antibody (Nb1053) with ⁶⁸Ga (t_1/2 = 1.1 h), we developed a CD38-targeted immuno-positron emission tomography (immunoPET) imaging probe [⁶⁸Ga]Ga-NOTA-Nb1053. The probe was developed with good radiochemical yield (> 50%), excellent radiochemical purity (> 99%), and immunoreactivity (> 95%). The diagnostic accuracy of the probe was thoroughly investigated in preclinical MM models.

RESULTS

ImmunoPET imaging with [⁶⁸Ga]Ga-NOTA-Nb1053 specifically depicted all the subcutaneous and orthotopic MM lesions, outperforming the traditional ¹⁸F-fluorodeoxyglucose PET and the nonspecific [⁶⁸Ga]Ga-NOTA-NbGFP immunoPET. More importantly, daratumumab preloading significantly reduced [⁶⁸Ga]Ga-NOTA-Nb1053 uptake in the disseminated bone lesions, indicating the overlapping targeting epitopes of [⁶⁸Ga]Ga-NOTA-Nb1053 with that of daratumumab. Furthermore, premedication with sodium maleate or fructose significantly decreased kidney retention of [⁶⁸Ga]Ga-NOTA-Nb1053 and improved the diagnostic value of the probe in lymphoma models.

CONCLUSION

This work successfully developed a novel CD38-targeted immunoPET imaging approach that enabled precise visualization of CD38 and diagnosis of MMs. Upon clinical translation, [⁶⁸Ga]Ga-NOTA-Nb1053 immunoPET may serve as a valuable CD38-targeted molecular imaging toolbox, facilitating early diagnosis of MM and precise assessment of the therapeutic responses.

ImmunoPET of CD146 in Orthotopic and Metastatic Breast Cancer Models

The overexpression of CD146 in breast cancer is considered a hallmark of tumor progression and metastasis, particularly in triple negative breast cancer. Aimed at imaging differential CD146 expressions in breast cancer, a noninvasive method for predictive prognosis and diagnosis was investigated using a ⁶⁴Cu-labeled CD146-specific monoclonal antibody, YY146. CD146 expression was screened in human breast cancer cell lines using Western blotting. Binding ability was evaluated using flow cytometry and immunofluorescent staining. YY146 was conjugated with 1,4,7-triazacyclononane-triacetic acid (NOTA) and radiolabeled with ⁶⁴Cu following standard procedures. Serial PET or PET/CT imaging was performed in orthotopic and metastatic breast cancer tumor models. Biodistribution was performed after the final time point of imaging. Finally, tissue immunofluorescent staining and hematoxylin and eosin (H&E) staining were performed on tumor tissues. The MDA-MB-435 cell line showed the highest CD146 expression level, whereas MCF-7 had the lowest level at the cellular level. ImmunoPET showed that MDA-MB-435 orthotopic tumors had high and clear radioactive accumulation after the administration of ⁶⁴Cu-NOTA-YY146. The tumor uptake of ⁶⁴Cu-NOTA-YY146 in MDA-MB-435 was significantly higher than that in MCF-7 and nonspecific IgG control groups (P < 0.01). Biodistribution verified the PET imaging results. For metastatic models, ⁶⁴Cu-NOTA-YY146 allowed for the visualization of high radioactivity accumulation in metastatic MDA-MB-435 tumors, which was confirmed by ex vivo biodistribution of lung tissues. H&E staining proved the successful building of metastatic tumor models. Immunofluorescent staining verified the differential expression of CD146 in orthotopic tumors. Therefore, ⁶⁴Cu-NOTA-YY146 could be used as an immunoPET probe to visualize CD146 in the breast cancer model and is potentially useful for cancer diagnosis, prognosis prediction, and monitoring therapeutic response.

Near-infrared photoimmunotherapy of cancer: a new approach that kills cancer cells and enhances anti-cancer host immunity

Near-infrared photoimmunotherapy (NIR-PIT) is a recently developed hybrid cancer therapy that directly kills cancer cells as well as producing a therapeutic host immune response. Conventional immunotherapies, such as immune-activating cytokine therapy, checkpoint inhibition, engineered T cells and suppressor cell depletion, do not directly destroy cancer cells, but rely exclusively on activating the immune system. NIR-PIT selectively destroys cancer cells, leading to immunogenic cell death that initiates local immune reactions to released cancer antigens from dying cancer cells. These are characterized by rapid maturation of dendritic cells and priming of multi-clonal cancer-specific cytotoxic T cells that kill cells that escaped the initial direct effects of NIR-PIT. The NIR-PIT can be applied to a wide variety of cancers either as monotherapy or in combination with conventional immune therapies to further activate anti-cancer immunity. A global Phase 3 clinical trial (https://clinicaltrials.gov/ct2/show/NCT03769506) of NIR-PIT targeting the epidermal growth factor receptor (EGFR) in patients with recurrent head and neck cancer is underway, employing RM1929/ASP1929, a conjugate of anti-EGFR antibody (cetuximab) plus the photo-absorber IRDye700DX (IR700). NIR-PIT has been given fast-track recognition by regulators in the USA and Japan. A variety of imaging methods, including direct IR700 fluorescence imaging, can be used to monitor NIR-PIT. As experience with NIR-PIT grows, additional antibodies will be employed to target additional antigens on other cancers or to target immune-suppressor cells to enhance host immunity. NIR-PIT will be particularly important in patients with localized and locally advanced cancers and may help such patients avoid side-effects associated with surgery, radiation and chemotherapy.

Ligand-Targeted Delivery of Photosensitizers for Cancer Treatment

Photodynamic therapy (PDT) is a promising cancer treatment which involves a photosensitizer (PS), light at a specific wavelength for PS activation and oxygen, which combine to elicit cell death. While the illumination required to activate a PS imparts a certain amount of selectivity to PDT treatments, poor tumor accumulation and cell internalization are still inherent properties of most intravenously administered PSs. As a result, common consequences of PDT include skin photosensitivity. To overcome the mentioned issues, PSs may be tailored to specifically target overexpressed biomarkers of tumors. This active targeting can be achieved by direct conjugation of the PS to a ligand with enhanced affinity for a target overexpressed on cancer cells and/or other cells of the tumor microenvironment. Alternatively, PSs may be incorporated into ligand-targeted nanocarriers, which may also encompass multi-functionalities, including diagnosis and therapy. In this review, we highlight the major advances in active targeting of PSs, either by means of ligand-derived bioconjugates or by exploiting ligand-targeting nanocarriers.

Tissue Factor-Targeted ImmunoPET Imaging and Radioimmunotherapy of Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is the most aggressive subtype of thyroid cancers with a dismal prognosis. It is aimed to explore a new biomarker and devise a marker-dependent theranostic pair for ATC. Flow cytometry is used to determine tissue factor (TF) expression in thyroid cancer cell lines. ALT-836, a TF-specific monoclonal antibody, is radiolabeled with 64Cu to develop 64Cu-NOTA-ALT-836. The diagnostic utility is assessed by immuno-positron emission tomography (immunoPET) imaging in ATC models. To facilitate total surgical removal of orthotopic ATCs, a near-infrared fluorescent imaging probe IRDye 800CW-ALT-836 is designed. As the therapeutic component, 131I-ALT-836 is further developed and the radioimmunotherapy (RIT) efficacy of this agent is interrogated in orthotopic ATC models. The results demonstrate that TF is highly expressed on the ATC cell line THJ-16T. 64Cu-NOTA-ALT-836 immunoPET imaging clearly delineates both subcutaneous and orthotopic ATCs, with a peak tumor uptake of 19.93 ± 2.17% ID per g (n = 3) and 37.20 ± 1.71% ID per g (n = 3), respectively. Fluorescent imaging with IRDye 800CW-ALT-836 facilitates the total resection of orthotopic ATCs. Moreover, 131I-ALT-836 RIT prolongs the survival of ATC-bearing mice. Taken together, TF is a promising marker for ATC and successive use of 64Cu-NOTA-ALT-836 and 131I-ALT-836 can realize precise management of ATC.

ImmunoPET Imaging of TIM-3 in Murine Melanoma Models

T cell immunoglobulin and mucin domain-containing-3 (TIM-3) is an immune checkpoint expressed mainly on CD4+ and CD8+ T cells. In addition to negatively regulating inflammatory T cell function, TIM-3 is a promising immunotherapy target. Herein, the aim is to develop an immuno-positron emission tomography (immunoPET) probe for noninvasively characterizing TIM-3 expression. Flow cytometry is used to detect the expression levels of TIM-3 in B16F10 cells. RMT3-23, a rat antimouse TIM-3-specific monoclonal antibody, is radiolabeled with 64Cu and the performance of 64Cu-NOTA-RMT3-23 is interrogated by immunoPET in murine melanoma models before and after radiation therapies. Biodistribution and immunofluorescent staining studies are carried out after the immunoPET imaging studies. TIM-3 is negatively expressed in B16F10 cells, and its expression is not induced by radiation therapies. ImmunoPET imaging with 64Cu-NOTA-RMT3-23 precisely tracks the unique distribution of TIM-3-positive lymphocytes in immunocompetent melanoma models, and tumor uptake of the radiotracer is not affected by either single-dose or fractionated radiation therapies. The 64Cu-NOTA-RMT3-23 immunoPET imaging results are further mirrored by the immunofluorescent staining studies. These results demonstrate the feasibility of 64Cu-NOTA-RMT3-23 immunoPET in tracking TIM-3 and highlight a new opportunity to optimize TIM-3-targeted immunotherapies with this novel imaging strategy.

Near Infrared Light Triggered Photo/Immuno-Therapy Toward Cancers

Nanomaterials-based phototherapies, mainly including photothermal therapy (PTT), photodynamic therapy (PDT) and photoimmunotherapy (PIT), present high efficacy, minimal invasion and negligible adverse effects in cancer treatment. The integrated phototherapeutic modalities can enhance the efficiency of cancer immunotherapy for clinical application transformation. The near-infrared (NIR) light source enables phototherapies with the high penetration depth in the biological tissues, less toxic to normal cells and tissues and a low dose of light irradiation. Mediated via the novel NIR-responsive nanomaterials, PTT and PDT are able to provoke cancer cells apoptosis from the generated heat and reactive oxygen species, respectively. The released cancer-specific antigens and membrane damage danger signals from the damaged cancer cells trigger immune responses, which would enhance the antitumor efficacy via a variety of immunotherapy. This review summarized the recent advances in NIR-triggered photo-/immune-therapeutic modalities and their synergistic mechanisms and applications toward cancers. Furthermore, the challenges, potential solutions and future directions of NIR-triggered photo-/immunotherapy were briefly discussed.

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.

Development and characterization of CD54-targeted immunoPET imaging in solid tumors

PURPOSE

Intercellular adhesion molecule-1 (ICAM-1, CD54) is an emerging therapeutic target for a variety of solid tumors including melanoma and anaplastic thyroid cancer (ATC). This study aims to develop an ICAM-1-targeted immuno-positron emission tomography (immunoPET) imaging strategy and assess its diagnostic value in melanoma and ATC models.

METHODS

Flow cytometry was used to screen ICAM-1-positive melanoma and ATC cell lines. Melanoma and ATC models were established using A375 cell line and THJ-16T cell line, respectively. An ICAM-1-specific monoclonal antibody (R6-5-D6) and a nonspecific human IgG were radiolabeled with ⁶⁴Cu and the diagnostic efficacies were interrogated in tumor-bearing mouse models. Biodistribution and fluorescent imaging studies were performed to confirm the specificity of the ICAM-1-targeted imaging probes.

RESULTS

ICAM-1 was strongly expressed on melanoma and advanced thyroid cancer cell lines. ⁶⁴Cu-NOTA-ICAM-1 immunoPET imaging efficiently delineated A375 melanomas with a peak tumor uptake of 21.28 ± 6.56 %ID/g (n = 5), significantly higher than that of ⁶⁴Cu-NOTA-IgG (10.63 ± 2.58 %ID/g, n = 3). Moreover, immunoPET imaging with ⁶⁴Cu-NOTA-ICAM-1 efficiently visualized subcutaneous and orthotopic ATCs with high clarity and contrast. Fluorescent imaging with IRDye 800CW-ICAM-1 also visualized orthotopic ATCs and the tumor uptake could be blocked by the ICAM-1 parental antibody R6-5-D6, indicating the high specificity of the developed probe. Finally, blocking with the human IgG prolonged the circulation of the ⁶⁴Cu-NOTA-ICAM-1 in R2G2 mice without compromising the tumor uptake.

CONCLUSION

ICAM-1-targeted immunoPET imaging could characterize ICAM-1 expression in melanoma and ATC, which holds promise for optimizing ICAM-1-targeted therapies in the future.

Carcinoembryonic antigen-targeted photodynamic therapy in colorectal cancer models

BACKGROUND

In colorectal cancer, survival of patients is drastically reduced when complete resection is hampered by involvement of critical structures. Targeted photodynamic therapy (tPDT) is a local and targeted therapy which could play a role in eradicating residual tumor cells after incomplete resection. Since carcinoembryonic antigen (CEA; CEACAM5) is abundantly overexpressed in colorectal cancer, it is a potential target for tPDT of colorectal cancer.

METHODS

To address the potential of CEA-targeted PDT, we compared colorectal cancer cell lines with different CEA-expression levels (SW-48, SW-480, SW-620, SW-1222, WiDr, HT-29, DLD-1, LS174T, and LoVo) under identical experimental conditions. We evaluated the susceptibility to tPDT by varying radiant exposure and concentration of our antibody conjugate (DTPA-hMN-14-IRDye700DX). Finally, we assessed the efficacy of tPDT in vivo in 18 mice (BALB/cAnNRj-Foxn1nu/nu) with subcutaneously xenografted LoVo tumors.

RESULTS

In vitro, the treatment effect of tPDT varied per cell line and was dependent on both radiant exposure and antibody concentration. Under standardized conditions (94.5 J/cm2 and 0.5 μg/μL antibody conjugate concentration), the effect of tPDT was higher in cells with higher CEA availability: SW-1222, LS174T, LoVo, and SW-48 (22.8%, 52.8%, 49.9%, and 51.9% reduction of viable cells, respectively) compared to cells with lower CEA availability. Compared to control groups (light or antibody conjugate only), tumor growth rate was reduced in mice with s.c. LoVo tumors receiving tPDT.

CONCLUSION

Our findings suggest cells (and tumors) have different levels of susceptibility for tPDT even though they all express CEA. Furthermore, tPDT can effectively reduce tumor growth in vivo.

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.