Targeted protein degradation combined with PET imaging reveals the role of host PD-L1 in determining anti-PD-1 therapy efficacy.

PURPOSE: Immunohistochemical staining of programmed death-ligand 1 (PD-L1) in tumor biopsies acquired through invasive procedures is routinely employed in clinical practice to identify patients who are most likely to benefit from anti-programmed cell death protein 1 (PD-1) therapy. Nevertheless, PD-L1 expression is observed in various cellular subsets within tumors and their microenvironments, including tumor cells, dendritic cells, and macrophages. The impact of PD-L1 expression across these different cell types on the responsiveness to anti-PD-1 treatment is yet to be fully understood. METHODS: We synthesized polymer-based lysosome-targeting chimeras (LYTACs) that incorporate both PD-L1-targeting motifs and liver cell-specific asialoglycoprotein receptor (ASGPR) recognition elements. Small-animal positron emission tomography (PET) imaging of PD-L1 expression was also conducted using a PD-L1-specific radiotracer 89Zr-αPD-L1/Fab. RESULTS: The PD-L1 LYTAC platform was capable of specifically degrading PD-L1 expressed on liver cancer cells through the lysosomal degradation pathway via ASGPR without impacting the PD-L1 expression on host cells. When coupled with whole-body PD-L1 PET imaging, our studies revealed that host cell PD-L1, rather than tumor cell PD-L1, is pivotal in the antitumor response to anti-PD-1 therapy in a mouse model of liver cancer. CONCLUSION: The LYTAC strategy, enhanced by PET imaging, has the potential to surmount the limitations of knockout mouse models and to provide a versatile approach for the selective degradation of target proteins in vivo. This could significantly aid in the investigation of the roles and mechanisms of protein functions associated with specific cell subsets in living subjects.

Sustained Secretion of CCL21 via an Implantable Cell Reservoir Hydrogel Enhances the Systemic Antitumor Effect of Radiotherapy.

The combination of radiotherapy (RT) and immunotherapy shows promise in improving the clinical treatment of solid tumors; however, it faces challenges of low response rates and systemic toxicity. Herein, an implantable alginate/collagen hydrogel encapsulating C-C motif ligand 21 (CCL21)-expressing dendritic cells (CCL21-DCs@gel) was developed to potentiate the systemic antitumor effects of RT. The hydrogel functioned as a suitable reservoir for in vivo culture and proliferation of CCL21-DCs, thereby enabling sustained CCL21 release. The local CCL21 gradient induced by CCL21-DCs@gel significantly enhanced the efficacy of RT in suppressing primary tumor growth and inhibiting distant metastasis across several mouse models. Furthermore, the combination of RT with CCL21-DCs@gel provided complete prophylactic protection to mice. Mechanistic investigations revealed that CCL21-DCs@gel potentiated RT by promoting tumor lymphangiogenesis and attracting immune cell infiltration into the tumor. Collectively, these results suggest that CCL21-DCs@gel is a promising adjunct to RT for effectively eradicating tumors and preventing tumor recurrence.

Noninvasively Deciphering the Immunosuppressive Tumor Microenvironment Using Galectin-1 PET to Inform Immunotherapy Responses.

Immune checkpoint blockade (ICB) has achieved groundbreaking results in clinical cancer therapy; however, only a subset of patients experience durable benefits. The aim of this study was to explore strategies for predicting tumor responses to optimize the intervention approach using ICB therapy. Methods: We used a bilateral mouse model for proteomics analysis to identify new imaging biomarkers for tumor responses to ICB therapy. A PET radiotracer was synthesized by radiolabeling the identified biomarker-targeting antibody with 124I. The radiotracer was then tested for PET prediction of tumor responses to ICB therapy. Results: We identified galectin-1 (Gal-1), a member of the carbohydrate-binding lectin family, as a potential negative biomarker for ICB efficacy. We established that Gal-1 inhibition promotes a sensitive immune phenotype within the tumor microenvironment (TME) for ICB therapy. To assess the pre-ICB treatment status of the TME, a Gal-1-targeted PET radiotracer, 124I-αGal-1, was developed. PET imaging with 124I-αGal-1 showed the pretreatment immunosuppressive status of the TME before the initiation of therapy, thus enabling the prediction of ICB resistance in advance. Moreover, the use of hydrogel scaffolds loaded with a Gal-1 inhibitor, thiodigalactoside, demonstrated that a single dose of thiodigalactoside-hydrogel significantly potentiated ICB and adoptive cell transfer immunotherapies by remodeling the immunosuppressive TME. Conclusion: Our study underscores the potential of Gal-1-targeted PET imaging as a valuable strategy for early-stage monitoring of tumor responses to ICB therapy. Additionally, Gal-1 inhibition effectively counteracts the immunosuppressive TME, resulting in enhanced immunotherapy efficacy.

Annotation of CD8+ T-cell function via ICAM-1 imaging identifies FAK inhibition as an adjuvant to augment the antitumor immunity of radiotherapy.

Background: Radiotherapy (RT) may trigger systemic antitumor immunity, manifesting as regression of non-irradiated lesions (abscopal effect). Intracellular adhesion molecule-1 (ICAM-1) is a key molecule involved in the abscopal effect of RT. However, the specific function of ICAM-1 in CD8+ T cells during antitumor immune responses remains unclear. Herein, we investigated whether noninvasive imaging of ICAM-1 can be used to annotate CD8+ T-cell function, thereby better selecting combinational therapy to enhance the antitumor immunity induced by RT. Methods: Using knockout mouse models, we investigated the role of ICAM-1 expressed on CD8+ T cells in the antitumor immunity of RT and conducted drug screening guided by ICAM-1-targeted noninvasive imaging. Results: The systemic antitumor effect of RT relies on the expression of ICAM-1 on CD8+ T cells. ICAM-1 expression is essential for CD8+ T-cell activation, proliferation, and effector function. Noninvasive annotation of the proliferation and effector function of CD8+ T cells by ICAM-1-targeted imaging identified VS-6063, a focal adhesion kinase inhibitor, as a new adjuvant to augment systemic antitumor immunity of RT in an immunologically "cold" tumor model. Mechanistically, VS-6063 overcomes the physical barriers in tumors and promotes the migration and infiltration of CD8+ T cells primed by RT into distant tumors. Conclusion: Our findings highlight that molecular imaging of ICAM-1 levels provides a dynamic readout of the proliferation and effector function of tumor-infiltrating CD8+ T cells, which facilitates the high-throughput exploitation of new combinational drugs to maximize the systemic antitumor effect of RT.

Calycosin protects against chronic prostatitis in rats via inhibition of the p38MAPK/NF-κB pathway.

Currently, the effect and molecular mechanism of calycosin, the main active ingredient of Qinshi Simiao San, which can alleviate chronic prostatitis (CP), on CP remain unclear. This study aimed to elucidate the potential mechanism of action of calycosin in CP in a rat CP model. The prostate tissue morphology was evaluated based on hematoxylin-eosin staining. Enzyme-linked immunosorbent assay was conducted to evaluate inflammatory cytokine and immune factor levels (secretory immunoglobulin A [SIgA]; immunoglobulin G [IgG]) in prostate tissues and serum. Additionally, representative biomarkers of oxidative stress, including malondialdehyde, superoxide dismutase, and catalase were detected using detection kits, and reactive oxygen species release was evaluated using immunofluorescence staining. Furthermore, the p38 mitogen-activated protein kinase (p38MAPK)/NF-kappaB (NF-κB) signaling pathway was analyzed by western blotting. The results showed that calycosin substantially ameliorated the pathological damage to prostate tissues of the CP rats. Moreover, calycosin significantly downregulated interleukin (IL)-1ß, IL-6, and tumor necrosis factor-alpha, IgG, and SIgA levels. Furthermore, we found that calycosin considerably suppressed oxidative stress and inhibited the activation of the p38MAPK/NF-κB signaling pathway in rats with CP. In summary, our findings revealed that calycosin protects against CP in rats by inhibiting the p38MAPK/NF-κB pathway.

Noninvasive interrogation of CD8+ T cell effector function for monitoring early tumor responses to immunotherapy.

Accurately identifying patients who respond to immunotherapy remains clinically challenging. A noninvasive method that can longitudinally capture information about immune cell function and assist in the early assessment of tumor responses is highly desirable for precision immunotherapy. Here, we show that PET imaging using a granzyme B-targeted radiotracer named 68Ga-grazytracer, could noninvasively and effectively predict tumor responses to immune checkpoint inhibitors and adoptive T cell transfer therapy in multiple tumor models. 68Ga-grazytracer was designed and selected from several radiotracers based on non-aldehyde peptidomimetics, and exhibited excellent in vivo metabolic stability and favorable targeting efficiency to granzyme B secreted by effector CD8+ T cells during immune responses. 68Ga-grazytracer permitted more sensitive discrimination of responders and nonresponders than did 18F-fluorodeoxyglucose, distinguishing between tumor pseudoprogression and true progression upon immune checkpoint blockade therapy in mouse models with varying immunogenicity. In a preliminary clinical trial with 5 patients, no adverse events were observed after 68Ga-grazytracer injection, and clinical responses in cancer patients undergoing immunotherapy were favorably correlated with 68Ga-grazytracer PET results. These results highlight the potential of 68Ga-grazytracer PET to enhance the clinical effectiveness of granzyme B secretion-related immunotherapies by supporting early response assessment and precise patient stratification in a noninvasive and longitudinal manner.

A self-triggered radioligand therapy agent for fluorescence imaging of the treatment response in prostate cancer.

PURPOSE: Radioligand therapy (RLT) targeting prostate-specific membrane antigen (PSMA) is emerging as an effective treatment option for metastatic castration-resistant prostate cancer (mCRPC). An imaging-based method to quantify early treatment responses can help to understand and optimize RLT. METHODS: We developed a self-triggered probe 2 targeting the colocalization of PSMA and caspase-3 for fluorescence imaging of RLT-induced apoptosis. RESULTS: The probe binds to PSMA potently with a Ki of 4.12 nM, and its fluorescence can be effectively switched on by caspase-3 with a Km of 67.62 µM. Cellular and in vivo studies demonstrated its specificity for imaging radiation-induced caspase-3 upregulation in prostate cancer. To identify the detection limit of our method, we showed that probe 2 could achieve 1.79 times fluorescence enhancement in response to 177Lu-RLT in a medium PSMA-expressing 22Rv1 xenograft model. CONCLUSION: Probe 2 can potently bind to PSMA, and the fluorescence signal can be sensitively switched on by caspase-3 both in vitro and in vivo. This method may provide an effective tool to investigate and optimize PSMA-RLT.

Galectin expression detected by 68Ga-galectracer PET as a predictive biomarker of radiotherapy resistance.

PURPOSE: Hypoxia is a hallmark of solid tumors that is related to radiotherapy resistance. As galectin members, such as galectin-1 and galectin-3, are associated with tumor hypoxia, herein we aimed to investigate whether positron emission tomography (PET) imaging of galectin expression can be employed to effectively pinpoint tumor hypoxia, and to predict radiotherapy resistance. METHODS: We synthesized a galectin-targeting radiotracer, designated 68Ga-galectracer, by radiolabeling a thiodigalactoside derivative. The properties of 68Ga-galectracer for PET imaging of tumor hypoxia were characterized in three tumor hypoxia mouse models. Additionally, preliminary PET/CT was performed in two patients with lung cancer to investigate the potential application of 68Ga-galectracer for clinical imaging. RESULTS: High-contrast imaging was achieved in the murine acute hypoxia tumor model, A549 natural hypoxia model, and sorafenib treatment-induced hypoxic 4T1 tumor model by PET using 68Ga-galectracer. In fact, 68Ga-galectracer exhibited superior hypoxia detection to that of 18F-misonidazole in the 4T1 tumors. Moreover, tumors with high galectin expression levels, as detected by 68Ga-galectracer PET, exhibited significantly lower responses to subsequent radiotherapy compared to those with low galectin expression levels. In patients with lung cancer, PET imaging using 68Ga-galectracer provided data that were complementary to that of the glucose metabolic PET radiotracer 18F-fluorodeoxyglucose. CONCLUSION: 68Ga-galectracer is a promising radiotracer for PET-based imaging of tumor hypoxia in vivo. Thus, hypoxia PET with 68Ga-galectracer could provide a noninvasive approach to proactively predict radiotherapy efficacy. TRIAL REGISTRATION: Chictr.org.cn (ChiCTR2000029522). Registered 03 February 2020.

LINC00265 promotes the viability, proliferation, and migration of bladder cancer cells via the miR-4677-3p/FGF6 axis.

BACKGROUND: Bladder cancer (BCa) is a common genitourinary malignancy with higher incidence in males. Long intergenic non-protein coding RNA 265 (LINC00265) is identified as an oncogene in many malignancies, while its role in BCa development remains unknown. PURPOSE: To explore the functions and mechanism of LINC00265 in BCa. RESEARCH DESIGN: Reverse transcription quantitative polymerase chain reaction was performed to examine LINC00265 expression in BCa cells. Cell counting kit-8 assays, colony formation assays, TdT-mediated dUTP Nick-End Labeling assays, and Transwell assays were conducted to examine BCa cell viability, proliferation, apoptosis, and migration. Luciferase reporter assays and RNA immunoprecipitation assays were carried out to explore the binding capacity between miR-4677-3p and messenger RNA fibroblast growth factor 6 (FGF6) (or LINC00265). Xenograft tumor model was established to explore the role of LINC00265 in vivo. RESULTS: LINC00265 was highly expressed in BCa cells. LINC00265 knockdown inhibited xenograft tumor growth and BCa cell viability, proliferation and migration while enhancing cell apoptosis. Moreover, LINC00265 interacted with miR-4677-3p to upregulate the expression of FGF6. FGF6 overexpression reversed the suppressive effect of LINC00265 knockdown on malignant phenotypes of BCa cells. CONCLUSIONS: LINC00265 promotes the viability, proliferation, and migration of BCa cells by binding with miR-4677-3p to upregulate FGF6 expression.

JFK Is a Hypoxia-Inducible Gene That Functions to Promote Breast Carcinogenesis.

Many carcinomas feature hypoxia, a condition has long been associated with tumor progression and poor prognosis, as well as resistance to chemoradiotherapy. Here, we report that the F-box protein JFK promotes mammary tumor initiation and progression in MMTV-PyMT murine model of spontaneous breast cancer. We find that JFK is inducible under hypoxic conditions, in which hypoxia-inducible factor HIF-1α binds to and transcriptionally activates JFK in breast cancer cells. Consistently, analysis of public clinical datasets reveals that the mRNA level of JFK is positively correlated with that of HIF-1α in breast cancer. We show that JFK deficiency leads to a decrease in HIF-1α-induced glycolysis in breast cancer and sensitizes hypoxic breast cancer cells to ionizing radiation and chemotherapeutic treatment. These results indicate that JFK is an important player in hypoxic response, supporting the pursuit of JFK as a potential therapeutic target for breast cancer intervention.

Molecular PET/CT Profiling of ACE2 Expression In Vivo: Implications for Infection and Outcome from SARS-CoV-2.

Rapid progress has been made to identify and study the causative agent leading to coronavirus disease 2019 (COVID-19) but many questions including who is most susceptible and what determines severity remain unanswered. Angiotensin-converting enzyme 2 (ACE2) is a key factor in the infection process of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). In this study, molecularly specific positron emission tomography imaging agents for targeting ACE2 are first developed, and these novel agents are evaluated in vitro, in preclinical model systems, and in a first-in-human translational ACE2 imaging of healthy volunteers and a SARS-CoV-2 recovered patient (NCT04422457). ACE2 expression levels in different organs in live subjects are quantitatively delineated and observable differences are measured in the patient recovered from COVID-19. Surprising sites of uptake in the breast, reproductive system and very low uptake in pulmonary tissues are reported. This novel method can add a unique tool to facilitate SARS-CoV-2 related research and improve understanding of this enigmatic disease. Molecular imaging provides quantitative annotation of ACE2, the SARS-CoV-2 entry receptor, to noninvasively monitor organs impacted by the COVID-19.

Metabolic radiolabeling and in vivo PET imaging of cytotoxic T lymphocytes to guide combination adoptive cell transfer cancer therapy.

BACKGROUND: Adoptive T cell transfer-based immunotherapy yields unsatisfactory results in the treatment of solid tumors, partially owing to limited tumor infiltration and the immunosuppressive microenvironment in solid tumors. Therefore, strategies for the noninvasive tracking of adoptive T cells are critical for monitoring tumor infiltration and for guiding the development of novel combination therapies. METHODS: We developed a radiolabeling method for cytotoxic T lymphocytes (CTLs) that comprises metabolically labeling the cell surface glycans with azidosugars and then covalently conjugating them with 64Cu-1,4,7-triazacyclononanetriacetic acid-dibenzo-cyclooctyne (64Cu-NOTA-DBCO) using bioorthogonal chemistry. 64Cu-labeled control-CTLs and ovalbumin-specific CTLs (OVA-CTLs) were tracked using positron emission tomography (PET) in B16-OVA tumor-bearing mice. We also investigated the effects of focal adhesion kinase (FAK) inhibition on the antitumor efficacy of OVA-CTLs using a poly(lactic-co-glycolic) acid (PLGA)-encapsulated nanodrug (PLGA-FAKi). RESULTS: CTLs can be stably radiolabeled with 64Cu with a minimal effect on cell viability. PET imaging of 64Cu-OVA-CTLs enables noninvasive mapping of their in vivo behavior. Moreover, 64Cu-OVA-CTLs PET imaging revealed that PLGA-FAKi induced a significant increase in OVA-CTL infiltration into tumors, suggesting the potential for a combined therapy comprising OVA-CTLs and PLGA-FAKi. Further combination therapy studies confirmed that the PLGA-FAKi nanodrug markedly improved the antitumor effects of adoptive OVA-CTLs transfer by multiple mechanisms. CONCLUSION: These findings demonstrated that metabolic radiolabeling followed by PET imaging can be used to sensitively profile the early-stage migration and tumor-targeting efficiency of adoptive T cells in vivo. This strategy presents opportunities for predicting the efficacy of cell-based adoptive therapies and for guiding combination regimens.

ICAM-1 orchestrates the abscopal effect of tumor radiotherapy.

Compelling evidence indicates that radiotherapy (RT) has a systemic inhibitory effect on nonirradiated lesions (abscopal effect) in addition to the ablation of irradiated tumors. However, this effect occurs only in rare circumstances in clinical practice, and mechanisms underlying the abscopal effect of RT are neither fully understood nor therapeutically utilized. Here we identified that intercellular adhesion molecule-1 (ICAM-1), an inducible glycoprotein of the immunoglobulin superfamily, is up-regulated in nonirradiated tumors responsive to RT. ICAM-1 expression in preclinical animal models can be noninvasively detected by optical imaging and positron emission tomography (PET) using near-infrared fluorescence dye- and 64Cu-labeled imaging probes that we synthesized, respectively. Importantly, the expression levels of ICAM-1 determined by quantitative PET imaging showed a strong negative linear correlation with the growth of nonirradiated tumors. Moreover, genetic or pharmacologic up-regulation of ICAM-1 expression by either an intratumoral injection of engineered recombinant adenovirus or systemic administration of a Toll-like receptor 7 agonist-capsulated nanodrug could induce markedly increased abscopal responses to local RT in animal models. Mechanistic investigation revealed that ICAM-1 expression can enhance both the activation and tumor infiltration of CD8+ T cells to improve the responses of the nonirradiated tumors to RT. Together, our findings suggest that noninvasive PET imaging of ICAM-1 expression could be a powerful means to predict the responses of nonirradiated tumors to RT, which could facilitate the exploration of new combination RT strategies for effective ablation of primary and disseminated lesions.

Nuclear imaging-guided PD-L1 blockade therapy increases effectiveness of cancer immunotherapy.

OBJECTIVES: Strategies to improve the responsiveness of programmed death-1 (PD-1)/programmed death ligand-1 (PD-L1) checkpoint blockade therapy remain an essential topic in cancer immunotherapy. In this study, we developed a new radiolabeled nanobody-based imaging probe 99mTc-MY1523 targeting PD-L1 for the enhanced therapeutic efficacy of PD-L1 blockade immunotherapy by the guidance of 99mTc-MY1523 SPECT/CT imaging. METHODS: The binding affinity and specificity of nanobody MY1523 were measured in vitro. MY1523 was radiolabeled with 99mTc by a site-specific transpeptidation of Sortase-A, and the biodistribution and single photon emission CT (SPECT)/CT were performed in mice bearing different tumors. We used interferon-γ (IFN-γ) as an intervention means to establish animal models with different levels of PD-L1 expression, then investigated the ability of 99mTc-MY1523 SPECT/CT for the in vivo non-invasive measurement of PD-L1 expression in tumors. Finally, the PD-L1 blockade immunotherapies guided by 99mTc-MY1523 SPECT/CT were carried out in MC-38, A20, and 4T1 tumor-bearing mouse models, followed by the testing of tumor infiltration T cells. RESULTS: MY1523 exhibited a high binding affinity and specificity to PD-L1 and had no competitive binding with the therapeutic antibody. 99mTc-MY1523 was prepared with high specific activity and radiochemical purity. It was found that tumor PD-L1 expression was dynamically upregulated by IFN-γ intervention in MC-38, A20, and 4T1 tumor-bearing mouse models, as indicated by 99mTc-MY1523 SPECT/CT. The PD-L1 blockade therapy initiated during the therapeutic time window determined by 99mTc-MY1523 SPECT/CT imaging significantly enhanced the therapeutic efficacy in all animal models, while the tumor growth was effectively suppressed, and the survival time of mice was evidently prolonged. A correlation between dynamically upregulated PD-L1 expression and improved PD-L1 blockade therapy effectiveness was revealed, and the markedly increased infiltration of effector T cells into tumors was verified after the imaging-guided therapy. CONCLUSION: Our results demonstrated that 99mTc-MY1523 SPECT/CT allowed a real-time, quantitative and dynamic mapping of PD-L1 expression in vivo, and the imaging-guided PD-L1 blockade immunotherapy significantly enhanced the therapeutic efficacy. This strategy merits translation into clinical practice for the better management of combination therapies with radiotherapy or chemotherapy.

[Expression of CDC25A in non-small cell lung cancer and its relationship with let-7 gene].

OBJECTIVE: To investigate the expression of CDC25A in non- small cell lung cancer (NSCLC) tissues and explore its correlation with the clinicpathological features of the patients and the expressions of let-7a1 and let-7c. METHODS: We collected surgical specimens of pathologically confirmed NSCLC tissues and paired adjacent lung tissues from 44 patients and tissues of benign lung lesions from 9 patients. The expressions of CDC25A protein and mRNA in the tissues were detected by immunohistochemistry and fluorescence quantitative RT-PCR, respectively; the expressions of let-7a1 and let-7c mRNA were detected using tail-adding fluorescence quantitative RT-PCR. RESULTS: The positivity rate of CDC25A protein expression was significantly higher in NSCLC tissues than in the adjacent tissues and benign pulmonary lesions (P < 0.05). CDC25A protein expression in NSCLC was not correlated with the patients' age, gender, pathological type, degree of tumor differentiation, or clinical stages (P > 0.05), and was significantly correlated with smoking and lymph node metastasis (P < 0.05). CDC25A mRNA expression was also significantly higher in NSCLC tissues than in the adjacent tissues and benign pulmonary lesions (F=6.33, P < 0.05), and was similar between the latter two tissues (P > 0.05). Pearson correlation analysis showed that CDC25A expression had a significant negative correlation with let-7c expression in both NSCLC tissues (r=-0.42) and adjacent lung tissues (r=-0.40) but was not correlated with let-7a1 expression. CONCLUSIONS: The expression level of CDC25A is significantly increased in NSCLC with a negative correlation with Let-7c expression, which identifies CDC25A as a possible downstream target gene of Let-7c.

Clinical Translation of a 68Ga-Labeled Integrin αvß6-Targeting Cyclic Radiotracer for PET Imaging of Pancreatic Cancer.

The overexpression of integrin αvß6 in pancreatic cancer makes it a promising target for noninvasive PET imaging. However, currently, most integrin αvß6-targeting radiotracers are based on linear peptides, which are quickly degraded in the serum by proteinases. Herein, we aimed to develop and assess a 68Ga-labeled integrin αvß6-targeting cyclic peptide (68Ga-cycratide) for PET imaging of pancreatic cancer. Methods:68Ga-cycratide was prepared, and its PET imaging profile was compared with that of the linear peptide (68Ga-linear-pep) in an integrin αvß6-positive BxPC-3 human pancreatic cancer mouse model. Five healthy volunteers (2 women and 3 men) underwent whole-body PET/CT imaging after injection of 68Ga-cycratide, and biodistribution and dosimetry were calculated. PET/CT imaging of 2 patients was performed to investigate the potential role of 68Ga-cycratide in pancreatic cancer diagnosis and treatment monitoring. Results:68Ga-cycratide exhibited significantly higher tumor uptake than did 68Ga-linear-pep in BxPC-3 tumor-bearing mice, owing-at least in part-to markedly improved in vivo stability. 68Ga-cycratide could sensitively detect the pancreatic cancer lesions in an orthotopic mouse model and was well tolerated in all healthy volunteers. Preliminary PET/CT imaging in patients with pancreatic cancer demonstrated that 68Ga-cycratide was comparable to 18F-FDG for diagnostic imaging and postsurgery tumor relapse monitoring. Conclusion:68Ga-cycratide is an integrin αvß6-specific PET radiotracer with favorable pharmacokinetics and a favorable dosimetry profile. 68Ga-cycratide is expected to provide an effective noninvasive PET strategy for pancreatic cancer lesion detection and therapy response monitoring.

Evaluation of 64Cu radiolabeled anti-hPD-L1 Nb6 for positron emission tomography imaging in lung cancer tumor mice model.

Recently, we selected a novel anti-hPD-L1-specific HCAb named Nb6 with high affinity (EC50 = 0.65 ng/mL) for potential hPD-L1 targeted non-invasive PET imaging. In this research, Nb6 was conjugated with the bifunctional chelator NCS-Bz-NOTA ((2-[(4-Isothiocyanophenyl) methyl]-1,4,7-triazacy-clononane-1,4,7-triacetic acid)) and further labeled with radio-nuclide 64Cu. 64Cu-NOTA-Nb6 was prepared with over 95% labeling yield, over 99% radiochemical purity and 14-16 GBq/µmol specific activity after PD-10 column purification. It shows good stability in 0.01 M PBS and 5% HSA solutions. 64Cu-NOTA-Nb6 has a high binding affinity to 3.60 nM which was tested by humanlungadenocarcinoma A549 cell lines. Tumor lesion can be clearly observed from 20 h to 38 h by Micro-PET equipment after 64Cu-NOTA-Nb6 administration. The study revealed that 64Cu-NOTA-Nb6 has good lesion detection ability, high ratios between tumor and non-tumor signal and can specifically target A549 xenografted tumor model. Taken together of good stability, high binding affinity, and tumor detection ability, 64Cu labeled Nb6 is a promising radio-tracer in diagnosing of hPD-L1 overexpression tumor, supposed to monitor PD-L1overexpression tumor progression and guide targeted therapy with PET molecular imaging.

Noninvasive PET tracking of post-transplant gut microbiota in living mice.

PURPOSE: The role that gut microbiota plays in determining the efficacy of the anti-tumor effect of immune checkpoint inhibitors is gaining increasing attention, and fecal bacterial transplantation has been recognized as a promising strategy for improving or rescuing the effect of immune checkpoint inhibition. However, techniques for the precise monitoring of in vivo bacterial behaviors after transplantation are limited. In this study, we aimed to use metabolic labeling and subsequent positron emission tomography (PET) imaging to track the in vivo behaviors of gut bacteria that are responsible for the efficacy of anti-PD-1 therapy in living mice. METHODS: The antitumor effect of anti-PD-1 blockade was tested in a low-response 4T1 syngeneic mouse model with or without fecal transplantation and with or without broad-spectrum antibiotic imipenem treatment. High-throughput sequencing analyses of 16S rRNA gene amplicons in feces of 4T1 tumor-bearing mice pre- and post-anti-PD-1 treatment were performed. The identified bacteria, Bacteroides fragilis (B. fragilis), were labeled with 64Cu and fluorescence dye by the metabolic labeling of N3 followed by click chemistry. In vivo PET and optical imaging of B. fragilis were performed in mice after oral gavage. RESULTS: The disturbance of gut microbiota reduced the efficacy of anti-PD-1 treatment, and the combination of B. fragilis gavage and PD-1 blockade was beneficial in rescuing the antitumor effect of anti-PD-1 therapy. Metabolic oligosaccharide engineering and biorthogonal click chemistry resulted in successful B. fragilis labeling with 64Cu and fluorescence dye with high in vitro and in vivo stability and no effect on viability. PET imaging successfully detected the in vivo behaviors of B. fragilis after transplantation. CONCLUSION: PET tracking by metabolic labeling is a powerful, noninvasive tool for the real-time tracking and quantitative imaging of gut microbiota. This strategy is clinically translatable and may also be extended to the PET tracking of other functional cells to guide cell-based adoptive therapies.

The deubiquitylase OTUD3 stabilizes GRP78 and promotes lung tumorigenesis.

The deubiquitylase OTUD3 plays a suppressive role in breast tumorigenesis through stabilizing PTEN protein, but its role in lung cancer remains unclear. Here, we demonstrate that in vivo deletion of OTUD3 indeed promotes breast cancer development in mice, but by contrast, it slows down KrasG12D-driven lung adenocarcinoma (ADC) initiation and progression and markedly increases survival in mice. Moreover, OTUD3 is highly expressed in human lung cancer tissues and its higher expression correlates with poorer survival of patients. Further mechanistic studies reveal that OTUD3 interacts with, deubiquitylates and stabilizes the glucose-regulated protein GRP78. Knockdown of OTUD3 results in a decrease in the level of GRP78 protein, suppression of cell growth and migration, and tumorigenesis in lung cancer. Collectively, our results reveal a previously unappreciated pro-oncogenic role of OTUD3 in lung cancer and indicate that deubiquitylases could elicit tumor-suppressing or tumor-promoting activities in a cell- and tissue-dependent context.

HOXB13 networking with ABCG1/EZH2/Slug mediates metastasis and confers resistance to cisplatin in lung adenocarcinoma patients.

Rationale: Distant metastasis and chemoresistance are the major causes of short survival after initial chemotherapy in lung adenocarcinoma patients. However, the underlying mechanisms remain elusive. Our pilot study identified high expression of the homeodomain transcription factor HOXB13 in chemoresistant lung adenocarcinomas. We aimed to investigate the role of HOXB13 in mediating lung adenocarcinoma chemoresistance. Methods: Immunohistochemistry assays were employed to assess HOXB13 protein levels in 148 non-small cell lung cancer patients. The role of HOXB13 in lung adenocarcinoma progression and resistance to cisplatin therapy was analyzed in cells, xenografted mice, and patient-derived xenografts. Needle biopsies from 15 lung adenocarcinoma patients who were resistant to cisplatin and paclitaxel therapies were analyzed for HOXB13 and EZH2 protein levels using immunohistochemistry. Results: High expression of HOXB13 observed in 17.8% of the lung adenocarcinoma patients in this study promoted cancer progression and predicted poor prognosis. HOXB13 upregulated an array of metastasis- and drug-resistance-related genes, including ABCG1, EZH2, and Slug, by directly binding to their promoters. Cisplatin induced HOXB13 expression in lung adenocarcinoma cells, and patient-derived xenografts and depletion of ABCG1 enhanced the sensitivity of lung adenocarcinoma cells to cisplatin therapy. Our results suggest that determining the combined expression of HOXB13 and its target genes can predict patient outcomes. Conclusions: A cisplatin-HOXB13-ABCG1/EZH2/Slug network may account for a novel mechanism underlying cisplatin resistance and metastasis after chemotherapy. Determining the levels of HOXB13 and its target genes from needle biopsy specimens may help predict the sensitivity of lung adenocarcinoma patients to platinum-based chemotherapy and patient outcomes.