The Relationship Between Tumor Glucose Metabolism and Host Systemic Inflammatory Responses in Patients with Cancer: A Systematic Review

SPECT Imaging with Tc-99m-Labeled HYNIC-FAPI-04 to Extend the Differential Time Window in Evaluating Tumor Fibrosis

The so-far used Ga-68- or F-18-labelled tracers are of a relative short time window in differentiating tumor fibrosis. SPECT applicable imaging probe, 99mTc-HYNIC-FAPI-04, was synthesized and evaluated in tumor cells and animal models of FAP-positive glioma and FAP-negative hepatoma, and then compared with 18F-FDG or 68Ga-FAPI-04 PET/CT. The radio-labeling rate of 99mTc-HYNIC-FAPI-04 was greater than 90%, and the radiochemical purity was >99% after purification with sep-pak C18 column. In vitro cell uptake experiments of 99mTc-HYNIC-FAPI-04 showed good FAP binding specificity, and the cellular uptake significantly decreased when blocked by DOTA-FAPI-04, reflecting the similar targeting mechanism of HYNIC-FAPI-04 and DOTA-FAPI-04. SPECT/CT imaging showed that U87MG tumor was distinguishable and of a high uptake of 99mTc-HYNIC-FAPI-04 (2.67 ± 0.35 %ID/mL at 1.5 h post injection (h P.I.), while tumor signal of FAP-negative HUH-7 was as low as 0.34 ± 0.06 %ID/mL. At 5 h P.I., U87MG tumor was still distinguishable (1.81 ± 0.20 %ID/mL). In comparison, although U87MG tumor was of obvious 68Ga-FAPI-04 uptake and clearly visible at 1 h P.I., the tumorous radioactive signals were fuzzy at 1.5 h P.I. 99mTc-HYNIC-FAPI-04 specifically bound to FAP-positive tumors and qualified with the ability of evaluating tumor fibrosis over longer time windows.

Lactate dehydrogenase: relationship with the diagnostic GLIM criterion for cachexia in patients with advanced cancer

BACKGROUND

Although suggestive of dysregulated metabolism, the relationship between serum LDH level, phenotypic/aetiologic diagnostic Global Leadership Initiative on Malnutrition (GLIM) criteria and survival in patients with advanced cancer has yet to examined.

METHODS

Prospectively collected data from patients with advanced cancer, undergoing anti-cancer therapy with palliative intent, across nine sites in the UK and Ireland between 2011-2016, was retrospectively analysed. LDH values were grouped as <250/250-500/>500 Units/L. Relationships were examined using χ² test for linear-by-linear association and binary logistics regression analysis.

RESULTS

A total of 436 patients met the inclusion criteria. 46% (n = 200) were male and 59% (n = 259) were ≥65 years of age. The median serum LDH was 394 Units/L and 33.5% (n = 146) had an LDH > 500 Units/L. LDH was significantly associated with ECOG-PS (p < 0.001), NLR (p < 0.05), mGPS (p < 0.05) and 3-month survival (p < 0.001). LDH was significantly associated with 3-month survival independent of weight loss (p < 0.01), BMI (p < 0.05), skeletal muscle mass (p < 0.01), metastatic disease (p < 0.05), NLR (p < 0.05) and mGPS (p < 0.01).

DISCUSSION

LDH was associated with performance status, systemic inflammation and survival in patients with advanced cancer. LDH measurement may be considered as an aetiologic criteria and become a potential therapeutic target in the treatment of cancer cachexia.

Correlations between glucose metabolism of bone marrow on 18 F-fluoro-D-glucose PET/computed tomography and hematopoietic cell populations in autoimmune diseases

PURPOSE

This study aims to investigate which hematopoieticcell populations, clinical factors, and laboratory values are associated with FDG uptake in bone marrow (BM) on FDG PET/CT in patients with autoimmune diseases.

METHODS

Forty-six patients with autoimmune disease who underwent FDG PET/CT and BM aspiration (BMA) between 2017 and 2022 were enrolled. The max and mean standard uptake values (SUVmax and SUVmean, SUVs) of FDG in BM, liver, and spleen were measured, and the bone marrow-to-liver SUVs ratios (BLRmax and BLRmean, BLRs) and spleen-to-liver SUVs ratios (SLRmax and SLRmean, SLRs) were calculated. BMA and clinical and laboratory parameters were collected and evaluated for association with BLRs and SLRs.

RESULTS

The patients were divided into the Grade II group (20; 43.5%) and Grade III groups (26; 56.5%) according to hemopoietic activity. The BLRmax ( P = 0.021), proportion of granulocytes ( P = 0.011), metamyelocytes ( P = 0.009), myelocytes ( P = 0.024), and monocytes ( P = 0.037) in BM were significantly higher in the Grade II group. Multivariate (stepwise) linear regression analyses showed that the proportion of granulocytes in BM was the strongest and only independent factor ( P < 0.0001) associated with BLRmax with an adjusted R2 of 0.431 in model 1. In model 2, ferritin ( P = 0.018), CRP ( P = 0.025), and the proportion of metamyelocytes ( P = 0.043) in BM were correlated with BLRmax with an adjusted R2 of 0.414.

CONCLUSION

The FDG uptake in BM is associated with hemopoietic activity and is regulated by hyperplastic granulocytes, particularly immature metamyelocytes, in patients with autoimmune diseases. Glucose metabolism in the BM correlates with the severity of systemic inflammation.

Affinity probes based on small-molecule inhibitors for tumor imaging

Methods for molecular imaging of target areas, including optical imaging, radionuclide imaging, magnetic resonance imaging and other imaging technologies, are helpful for the early diagnosis and precise treatment of cancers. In addition to cancer management, small-molecule inhibitors are also used for developing cancer target probes since they act as the tight-binding ligands of overexpressed proteins in cancer cells. This review aims to summarize the structural designs of affinity probes based on small-molecule inhibitors from the aspects of the inhibitor, linker, dye and radionuclide, and discusses the influence of the modification of these structures on affinity and pharmacokinetics. We also present examples of inhibitor affinity probes in clinical applications, and these summaries will provide insights for future research and clinical translations.

Chronic Inflammation in Obesity and Cancer Cachexia

Chronic inflammation has long been linked to obesity and related conditions such as type 2 diabetes and metabolic syndrome. According to current research, the increased risk of cancer in people with certain metabolic diseases may be due to chronic inflammation. Adipocytokines, which are pro-inflammatory cytokines secreted in excess, are elevated in many chronic metabolic diseases. Cytokines and inflammatory mediators, which are not directly linked to DNA, are important in tumorigenesis. Cachexia, a type of metabolic syndrome linked to the disease, is associated with a dysregulation of metabolic pathways. Obesity and cachexia have distinct metabolic characteristics, such as insulin resistance, increased lipolysis, elevated free fatty acids (FFA), and ceramide levels, which are discussed in this section. The goal of this research project is to create a framework for bringing together our knowledge of inflammation-mediated insulin resistance.

Anchoring Group-Mediated Radiolabeling of Inorganic Nanoparticles─A Universal Method for Constructing Nuclear Medicine Imaging Nanoprobes

Nuclear medicine imaging has aroused great interest in the design and synthesis of versatile radioactive nanoprobes, while most of the methods developed for radiolabeling nanoprobes are difficult to satisfy the criteria of clinical translation, including easy operation, mild labeling conditions, high efficiency, and high radiolabeling stability. Herein, we demonstrated the universality of a simple but efficient radiolabeling method recently developed for constructing nuclear imaging nanoprobes, that is, ligand anchoring group-mediated radiolabeling (LAGMERAL). In this method, a diphosphonate-polyethylene glycol (DP-PEG) decorating on the surface of inorganic nanoparticles plays an essential role. In principle, owing to the strong binding affinity to a great variety of metal ions, it can not only endow the underlying nanoparticles containing metal ions including some main group metal ions, transition metal ions, and lanthanide metal ions with excellent colloidal stability and biocompatibility but also enable efficient radiolabeling through the diphosphonate group. Based on this assumption, inorganic nanoparticles such as Fe₃O₄ nanoparticles, NaGdF₄:Yb,Tm nanoparticles, and Cu_2-xS nanoparticles, as representatives of functional inorganic nanoparticles suitable for different imaging modalities including magnetic resonance imaging (MRI), upconversion luminescence imaging (UCL), and photoacoustic imaging (PAI), respectively, were chosen to be radiolabeled with different kinds of radionuclides such as SPECT nuclides (e.g., ^99mTc), PET nuclides (e.g., ⁶⁸Ga), and therapeutic SPECT nuclides (e.g., ¹⁷⁷Lu) to demonstrate the reliability of the LAGMERAL approach. The experimental results showed that the obtained nanoprobes exhibited high radiolabeling stability, and the whole radiolabeling process had negligible impacts on the physical and chemical properties of the initial nanoparticles. Through passive targeting SPECT/MRI of glioma tumor, active targeting SPECT/UCL of colorectal cancer, and SPECT/PAI of lymphatic metastasis, the outstanding potentials of the resulting radioactive nanoprobes for sensitive tumor diagnosis were demonstrated, manifesting the feasibility and efficiency of LAGMERAL.

Metabolic activity of extranodal NK/T cell lymphoma on 18F-FDG PET/CT according to immune subtyping

Disseminated extranodal NK/T cell lymphoma (ENKTL) is associated with dismal prognosis. Hence, distinct tumor immune microenvironment (TIME) subtypes were proposed to explain their influence on ENKTL progression and help predict treatment response. In this study, we investigated the capacity of FDG PET/CT to discern ENKTL TIME subtypes. A total of 108 pretreatment FDG PET/CT scans of 103 patients with newly diagnosed or relapsed ENKTL were retrospectively analyzed. TIME subtype was determined using three key immunohistochemical markers. SUVmax, MTV and TLG were measured, and metabolic features associated with TIME subtype were statistically extracted. TIME subtype was immune tolerance (IT) in 13.9%, immune evasion A (IE-A) in 56.5%, immune evasion B (IE-B) in 21.3%, and immune silenced (IS) in 8%. The IS group showed the highest SUVmax (15.9 ± 6.4, P = 0.037), followed by IE-A (14.1 ± 7.8), IE-B (10.9 ± 5.6), and IT groups (9.6 ± 5.1). Among 53 with only nasal FDG lesions, 52 had non-IS subtype. Among 55 with extra-nasal FDG lesions, those with IS subtype more often had adrenal (P = 0.001) or testis involvement (P = 0.043), greater MTV (P = 0.005), greater TLG (P = 0.005), and SUVmax located at extra-nasal sites. The presence of 0–2 and 3–4 of these four findings was associated with low probability (2/46) and high probability (6/9) of IS subtype, respectively. Furthermore, patients showing IS subtype-favoring PET/CT pattern had worse overall survival compared to their counterparts. These results demonstrate that FDG PET/CT can help predict immune subtype in ENKTL patients. The different patterns between glycolytic activity and involved site according to TIME subtype might be related to the interplay between tumor cells and immune cells in the tumor microenvironment.

State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation

AIM

The diagnosis, severity and extent of a sterile inflammation or a septic infection could be challenging since there is not one single test able to achieve an accurate diagnosis. The clinical use of 18F-fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) imaging in the assessment of inflammation and infection is increasing worldwide. The purpose of this paper is to achieve an Italian consensus document on [¹⁸F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases, such as osteomyelitis (OM), prosthetic joint infections (PJI), infective endocarditis (IE), prosthetic valve endocarditis (PVE), cardiac implantable electronic device infections (CIEDI), systemic and cardiac sarcoidosis (SS/CS), diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), fever and inflammation of unknown origin (FUO/IUO), pediatric infections (PI), inflammatory bowel diseases (IBD), spine infections (SI), vascular graft infections (VGI), large vessel vasculitis (LVV), retroperitoneal fibrosis (RF) and COVID-19 infections.

METHODS

In September 2020, the inflammatory and infectious diseases focus group (IIFG) of the Italian Association of Nuclear Medicine (AIMN) proposed to realize a procedural paper about the clinical applications of [¹⁸F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases. The project was carried out thanks to the collaboration of 13 Italian nuclear medicine centers, with a consolidate experience in this field. With the endorsement of AIMN, IIFG contacted each center, and the pediatric diseases focus group (PDFC). IIFG provided for each team involved, a draft with essential information regarding the execution of [¹⁸F]FDG PET/CT or PET/MRI scan (i.e., indications, patient preparation, standard or specific acquisition modalities, interpretation criteria, reporting methods, pitfalls and artifacts), by limiting the literature research to the last 20 years. Moreover, some clinical cases were required from each center, to underline the teaching points. Time for the collection of each report was from October to December 2020.

RESULTS

Overall, we summarized 291 scientific papers and guidelines published between 1998 and 2021. Papers were divided in several sub-topics and summarized in the following paragraphs: clinical indications, image interpretation criteria, future perspectivess and new trends (for each single disease), while patient preparation, image acquisition, possible pitfalls and reporting modalities were described afterwards. Moreover, a specific section was dedicated to pediatric and PET/MRI indications. A collection of images was described for each indication.

CONCLUSIONS

Currently, [¹⁸F]FDG PET/CT in oncology is globally accepted and standardized in main diagnostic algorithms for neoplasms. In recent years, the ever-closer collaboration among different European associations has tried to overcome the absence of a standardization also in the field of inflammation and infections. The collaboration of several nuclear medicine centers with a long experience in this field, as well as among different AIMN focus groups represents a further attempt in this direction. We hope that this document will be the basis for a "common nuclear physicians' language" throughout all the country.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40336-021-00445-w.

Lymphoma Severity and Type Are Associated With Aortic FDG Uptake by 18F-FDG PET/CT Imaging

Background

There is evidence that metabolic disease burden in lymphoma influences patient outcome. However, the impact of disease severity on the cardiovascular system is unknown.

Objectives

The aim of this study was to examine whether lymphoma is associated with arterial inflammation by investigating the relationship between disease metabolic burden and arterial fluorodeoxyglucose (FDG) uptake.

Methods

Sixty-two chemotherapy-naïve patients with active Hodgkin’s or non-Hodgkin’s lymphoma were matched (2:1) to individual control groups of lymphoma patients previously treated and free of active disease. All groups underwent ¹⁸F-FDG position emission tomography–computed tomography imaging. Disease severity was quantified by metabolic tumor volume (MTV) and total lesion glycolysis corresponding to standardized uptake values (SUVs) ≥41% or ≥2.5 of the maximum SUV within lymphoma regions, and aortic FDG uptake was quantified through the target-to-background ratio (TBR). Inflammatory and disease severity biomarkers were also measured.

Results

MTV and total lesion glycolysis measurements were significantly correlated with inflammatory and disease biomarkers. Aortic TBR was higher in patients with active non-Hodgkin’s lymphoma compared with control subjects (median difference 0.51; 95% confidence interval [CI]: 0.28 to 0.78; p < 0.001). Similarly, patients with active Hodgkin’s lymphoma had higher values of aortic TBR compared with control subjects (median difference 0.31; 95% CI: 0.15 to 0.49; p < 0.001). In addition, aortic TBR was modestly increased in patients with stage III to IV disease compared with those with stage I to II disease (median aortic TBR: 2.23 [interquartile range: 2.01 to 2.54] vs. 2.06 [interquartile range: 1.83 to 2.27; p = 0.050). In multivariable analysis, aortic FDG uptake and MTV_≥2.5 values were independently associated (β = 0.425; 95% CI: 0.189 to 0.662; p = 0.001; R² = 0.208), as were aortic FDG uptake and MTV_≥41% (β = 0.407; 95% CI: 0.167 to 0.649, p = 0.001; R² = 0.191).

Conclusions

Aortic wall FDG uptake is related with disease severity indicative of a possible vascular effect of lymphoma. This work highlights a new potential role of molecular imaging in cardio-oncology for evaluating disease severity and its consequences on the vasculature.

Tacrolimus, a rapamycin target protein inhibitor, exerts anti-cystic echinococcosis effects both in vitro and in vivo

In view of a growing need for new treatment options for human cystic echinococcosis (CE), we aimed to investigate the efficacy of mTOR pathway inhibitors against CE in vitro and in vivo. Among the seven mTOR inhibitors evaluated, tacrolimus (TAC) showed significant dose- and time-dependent killing of cultured protoscoleces and cysts in vitro. Notably, the oral administration of TAC (4 mg/kg/day) to CE mice model highly effectively reduced both the weight and number of parasitic cysts. Transmission electron microscopy revealed that TAC destroys the ultrastructure of cysts, both in vitro and in vivo. Furthermore, TAC had no significant effect on blood glucose, body weight, liver, or kidney functions in mice. We further observed that the ATP levels and glucose content of cysts reduced upon TAC treatment, indicating that inhibiting mTORC1 activity possibly affects glucose metabolism in the cysts of mice. Based on our experimental data, TAC emerged as a promising anti-cyst drug that efficiently inhibits the growth of cysts.

The relationship between 18F-FDG-PETCT-derived tumour metabolic activity, nutritional risk, body composition, systemic inflammation and survival in patients with lung cancer

The aim of this study was to examine the relationship between PET-CT derived tumour glucose uptake as measured by maximum standard glucose uptake (SUVmax) and total lesion glycolysis (TLG), nutritional risk as measured by the malnutrition universal screening tool (MUST), CT derived body composition as measured by skeletal muscle index (SMI) and skeletal muscle radiodensity (SMD), the systemic inflammatory response as measured by the modified Glasgow prognostic score (mGPS) and the neutrophil to lymphocyte ratio (NLR) and survival in patients with lung cancer, treated with radiotherapy. In a retrospective cohort study, 119 patients were included in final analyses. The majority of patients were over 65 (86%), female (52%), had a performance status (ECOG-PS) of 0 or 1 (57%), were at nutritional risk (57%), were overweight (53%), had visceral obesity (62%), had a normal SMI (51%), had a low SMD (62%) and were systemically inflammed (mGPS 1/2, 51%). An elevated TLG was associated with sex (p < 0.05), TNM stage (p < 0.001), MUST (p < 0.01) and mGPS (p < 0.01). An elevated mGPS was associated with age (p < 0.05), NLR (p < 0.01), MUST (p < 0.01), and TLG (p < 0.01). On univariate survival analysis, TNM stage (p < 0.01), mGPS (p < 0.05), NLR (p < 0.01), MUST (p ≤ 0.001), Low SMD (p < 0.05), SUVmax (p ≤ 0.001) and TLG (p < 0.001) were associated with overall survival. On multivariate survival analysis MUST (HR: 1.49 95%CI 1.12–01.98 p < 0.01) and TLG (HR: 2.02 95%CI 1.34–3.04 p = 0.001) remained independently associated with survival. In conclusion, elevated tumour metabolic activity was associated with more advanced stage, greater nutritional risk, the systemic inflammatory response and poorer survival but not body composition analysis in patients with lung cancer. These results suggest that detrimental body composition is not directly determined by tumour metabolic activity but rather an ongoing systemic inflammatory response.

Altered glucose metabolism and insulin resistance in cancer-induced cachexia: a sweet poison

Cancer cachexia is a wasting disorder characterised by specific skeletal muscle and adipose tissue loss. Cancer cachexia is also driven by inflammation, altered metabolic changes such as increased energy expenditure, elevated plasma glucose, insulin resistance and excess catabolism. In cachexia, host-tumor interaction causes release of the lactate and inflammatory cytokines. Lactate released by tumor cells takes part in hepatic glucose production with the help of gluconeogenic enzymes. Thus, Cori cycle between organs and cancerous cells contributes to increased glucose production and energy expenditure. A high amount of blood glucose leads to increased production of insulin. Overproduction of insulin causes inactivation of PI3K/Akt/m-TOR pathway and finally results in insulin resistance. Insulin is involved in maintaining the vitality of organs and regulate the metabolism of glucose, protein and lipids. Insulin insensitivity decreases the uptake of glucose in the organs and results in loss of skeletal muscles and adipose tissues. However, looking into the complexity of this metabolic syndrome, it is impossible to rely on a single variable to treat patients having cancer cachexia. Hence, it becomes greater a challenge to produce a clinically effective treatment for this metabolic syndrome. Thus, the present paper aims to provide an understanding of pathogenesis and mechanism underlining the altered glucose metabolism and insulin resistance and its contribution to the progression of skeletal muscle wasting and lipolysis, providing future direction of research to develop new pharmacological treatment in cancer cachexia.

Real-time metabolic profiling of oesophageal tumours reveals an altered metabolic phenotype to different oxygen tensions and to treatment with Pyrazinib

Oesophageal cancer is the 6th most common cause of cancer related death worldwide. The current standard of care for oesophageal adenocarcinoma (OAC) focuses on neoadjuvant therapy with chemoradiation or chemotherapy, however the 5-year survival rates remain at < 20%. To improve treatment outcomes it is critical to further investigate OAC tumour biology, metabolic phenotype and their metabolic adaptation to different oxygen tensions. In this study, by using human ex-vivo explants we demonstrated using real-time metabolic profiling that OAC tumour biopsies have a significantly higher oxygen consumption rate (OCR), a measure of oxidative phosphorylation compared to extracellular acidification rate (ECAR), a measure of glycolysis (p = 0.0004). Previously, we identified a small molecule compound, pyrazinib which enhanced radiosensitivity in OAC. Pyrazinib significantly inhibited OCR in OAC treatment-naïve biopsies (p = 0.0139). Furthermore, OAC biopsies can significantly adapt their metabolic rate in real-time to their environment. Under hypoxic conditions pyrazinib produced a significant reduction in both OCR (p = 0.0313) and ECAR in OAC treatment-naïve biopsies. The inflammatory secretome profile from OAC treatment-naïve biopsies is heterogeneous. OCR was positively correlated with three secreted factors in the tumour conditioned media: vascular endothelial factor A (VEGF-A), IL-1RA and thymic stromal lymphopoietin (TSLP). Pyrazinib significantly inhibited IL-1β secretion (p = 0.0377) and increased IL-3 (p = 0.0020) and IL-17B (p = 0.0181). Importantly, pyrazinib did not directly alter the expression of dendritic cell maturation markers or reduce T-cell viability or activation markers. We present a new method for profiling the metabolic rate of tumour biopsies in real-time and demonstrate the novel anti-metabolic and anti-inflammatory action of pyrazinib ex-vivo in OAC tumours, supporting previous findings in-vitro whereby pyrazinib significantly enhanced radiosensitivity in OAC.

Diagnostic value of 18F-FDG-PET to predict the tumour immune status defined by tumoural PD-L1 and CD8+tumour-infiltrating lymphocytes in oral squamous cell carcinoma

BACKGROUND

Lately, immune checkpoint proteins, such as programmed death 1 (PD-1) and its ligand-1 (PD-L1), have garnered attention as a new target in oral squamous cell carcinoma (OSCC). Reportedly, fluoro-D-glucose (FDG)-uptake alteration by anti-PD-1 antibody treatment depicts the response in patients with lung cancer. This study aims to elucidate the correlations between tumour immune status, clinicopathological factors, ¹⁸F-FDG-uptake and cold tumour phenotypes as low PD-L1 expression/low CD8⁺tumour-infiltrating lymphocytes (TILs) in OSCC.

METHODS

We performed immunohistochemical analysis of PD-L1, hypoxia-inducible factor 1 A (HIF-1A), glucose transporter type 1 (GLUT1), CD8, E-cadherin and Ki-67 on 59 operable OSCC samples. We assessed the correlations between these factors and preoperative ¹⁸F-FDG-uptake, clinicopathological characteristics and prognosis.

RESULTS

Low expression of PD-L1 in OSCC correlated with cancer aggressiveness, poor prognosis, high ¹⁸F-FDG-uptake with HIF-1A/GLUT1 and low E-cadherin expression and low CD8. Cold tumour phenotypes as low PD-L1 tumour cells and low stromal CD8 correlated with the poor prognosis, high ¹⁸F-FDG-uptake and E-cadherin suppression. Furthermore, the high level of preoperative ¹⁸F-FDG-uptake in OSCC was an independent predictor of the cold tumour immune status.

CONCLUSIONS

¹⁸F-FDG-uptake is an independent predictor of cold tumour in OSCC. ¹⁸F-FDG-PET imaging could be a promising diagnostic tool to estimate tumour immune status.

Cancer immunotherapy is accompanied by distinct metabolic patterns in primary and secondary lymphoid organs observed by non-invasive in vivo 18F-FDG-PET

Purpose: Cancer immunotherapy depends on a systemic immune response, but the basic underlying mechanisms are still largely unknown. Despite the very successful and widespread use of checkpoint inhibitors in the clinic, the majority of cancer patients do not benefit from this type of treatment. In this translational study, we investigated whether noninvasive in vivo positron emission tomography (PET) imaging using 2-[¹⁸F]fluoro-2-deoxy-D-glucose (¹⁸F-FDG) is capable of detecting immunotherapy-associated metabolic changes in the primary and secondary lymphoid organs and whether this detection enables the prediction of a successful anti-cancer immune response. Methods: RIP1-Tag2 mice with progressed endogenous insular cell carcinomas underwent a combined cancer immunotherapy consisting of CD4⁺ T cells plus monoclonal antibodies (mAbs) against programmed death ligand-1 (PD-L1) and lymphocyte activation gene-3 (LAG-3) or a sham treatment after radiation-mediated immune cell depletion. A second cohort of RIP1-Tag2 mice underwent exclusive checkpoint inhibitor therapy (CIT) using anti-PD-L1/LAG-3 mAbs or sham treatment without initial immune cell depletion to mimic the clinical situation. All mice were monitored by ¹⁸F-FDG-PET combined with anatomical magnetic resonance imaging (MRI). In addition, we retrospectively analyzed PET / computed tomography (CT) scans (PET/CT) regarding ¹⁸F-FDG uptake of CIT-treated metastatic melanoma patients in the spleen (n=23) and bone marrow (BM; n=20) as well as blood parameters (n=17-21). Results: RIP1-Tag2 mice with advanced insular cell carcinomas treated with combination immunotherapy exhibited significantly increased ¹⁸F-FDG uptake in the spleen compared to sham-treated mice. Histopathology of the spleens from treated mice revealed atrophy of the white pulp with fewer germinal centers and an expanded red pulp with hyperplasia of neutrophils than those of sham-treated mice. Immunohistochemistry and flow cytometry analyses of the spleens revealed a lower number of T cells and a higher number of neutrophils compared to those in the spleens of sham-treated mice. Flow cytometry of the BM showed enhanced activation of T cells following the treatment schemes that included checkpoint inhibitors. The ratio of ¹⁸F-FDG uptake at baseline to the uptake at follow-up in the spleens of exclusively CIT-treated RIP1-Tag2 mice was significantly enhanced, but the ratio was not enhanced in the spleens of the sham-treated littermates. Flow cytometry analysis confirmed a reduced number of T cells in the spleens of exclusively CIT-treated mice compared to that of sham-treated mice. A retrospective analysis of clinical ¹⁸F-FDG-PET/CT scans revealed enhanced ¹⁸F-FDG uptake in the spleens of some successfully CIT-treated patients with metastatic melanoma, but there were no significant differences between responders and non-responders. The analysis of the BM in clinical ¹⁸F-FDG-PET/CT scans with a computational segmentation tool revealed significantly higher baseline ¹⁸F-FDG uptake in patients who responded to CIT than in non-responders, and this relationship was independent of bone metastasis, even in the baseline scan. Conclusions: Thus, we are presenting the first translational study of solid tumors focusing on the metabolic patterns of primary and secondary lymphoid organs induced by the systemic immune response after CIT. We demonstrate that the widely available ¹⁸F-FDG-PET modality is an applicable translational tool that has high potential to stratify patients at an early time point.

Radiolabeling nanomaterials for multimodality imaging: New insights into nuclear medicine and cancer diagnosis

Nuclear medicine imaging has been developed as a powerful diagnostic approach for cancers by detecting gamma rays directly or indirectly from radionuclides to construct images with beneficial characteristics of high sensitivity, infinite penetration depth and quantitative capability. Current nuclear medicine imaging modalities mainly include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that require administration of radioactive tracers. In recent years, a vast number of radioactive tracers have been designed and constructed to improve nuclear medicine imaging performance toward early and accurate diagnosis of cancers. This review will discuss recent progress of nuclear medicine imaging tracers and associated biomedical imaging applications. Radiolabeling nanomaterials for rational development of tracers will be comprehensively reviewed with highlights on radiolabeling approaches (surface coupling, inner incorporation and interface engineering), providing profound understanding on radiolabeling chemistry and the associated imaging functionalities. The applications of radiolabeled nanomaterials in nuclear medicine imaging-related multimodality imaging will also be summarized with typical paradigms described. Finally, key challenges and new directions for future research will be discussed to guide further advancement and practical use of radiolabeled nanomaterials for imaging of cancers.