Interleukin 17 signaling supports clinical benefit of dual CTLA-4 and PD-1 checkpoint inhibition in melanoma.

Recent studies suggest that BRAFV600-mutated melanomas in particular respond to dual anti-programmed cell death protein 1 (PD-1) and anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) immune checkpoint inhibition (ICI). Here we identified an over-representation of interleukin (IL)-17-type 17 helper T (TH17) gene expression signatures (GES) in BRAFV600-mutated tumors. Moreover, high baseline IL-17 GES consistently predicted clinical responses in dual-ICI-treated patient cohorts but not in mono anti-CTLA-4 or anti-PD-1 ICI cohorts. High IL-17 GES corresponded to tumor infiltration with T cells and neutrophils. Accordingly, high neutrophil infiltration correlated with clinical response specifically to dual ICI, and tumor-associated neutrophils also showed strong IL-17-TH17 pathway activity and T cell activation capacity. Both the blockade of IL-17A and the depletion of neutrophils impaired dual-ICI response and decreased T cell activation. Finally, high IL-17A levels in the blood of patients with melanoma indicated a higher global TH17 cytokine profile preceding clinical response to dual ICI but not to anti-PD-1 monotherapy, suggesting a future role as a biomarker for patient stratification.

Administration Routes for SSTR-/PSMA- and FAP-Directed Theranostic Radioligands in Mice.

The NETTER-1, VISION, and TheraP trials proved the efficacy of repeat intravenous application of small radioligands. Application by subcutaneous, intraperitoneal, or oral routes is an important alternative and may yield comparable or favorable organ and tumor radioligand uptake. Here, we assessed organ and tumor biodistribution for various radioligand application routes in healthy mice and models of cancer expressing somatostatin receptor (SSTR), prostate-specific membrane antigen (PSMA), and fibroblast activation protein (FAP). Methods: Healthy and tumor-bearing male C57BL/6 or NOD SCID γ-mice, respectively, were administered a mean of 6.0 ± 0.5 MBq of 68Ga-DOTATOC (RM1-SSTR allograft), 5.3 ± 0.3 MBq of 68Ga-PSMA11 (RM1-PSMA allograft), or 4.8 ± 0.2 MBq of 68Ga-FAPI46 (HT1080-FAP xenograft) by intravenous, intraperitoneal, subcutaneous, or oral routes. In vivo PET images and ex vivo biodistribution in tumor, organs, and the injection site were assessed up to 5 h after injection. Healthy mice were monitored for up to 7 d after the last scan for signs of stress or adverse reactions. Results: After intravenous, intraperitoneal, and subcutaneous radioligand administration, average residual activity at the injection site was less than 17 percentage injected activity per gram (%IA/g) at 1 h after injection, less than 10 %IA/g at 2 h after injection, and no more than 4 %IA/g at 4 h after injection for all radioligands. After oral administration, at least 50 %IA/g remained within the intestines until 4 h after injection. Biodistribution in organs of healthy mice was nearly equivalent after intravenous, intraperitoneal, and subcutaneous application at 1 h after injection and all subsequent time points (≤1 %IA/g for liver, blood, and bone marrow; 11.2 ± 1.4 %IA/g for kidneys). In models for SSTR-, PSMA- and FAP-expressing cancer, tumor uptake was increased or equivalent for intraperitoneal/subcutaneous versus intravenous injection at 5 h after injection (ex vivo): SSTR, 7.2 ± 1.0 %IA/g (P = 0.0197)/6.5 ± 1.3 %IA/g (P = 0.0827) versus 2.9 ± 0.3 %IA/g, respectively; PSMA, 3.4 ± 0.8 %IA/g (P = 0.9954)/3.9 ± 0.8 %IA/g (P = 0.8343) versus 3.3 ± 0.7% IA/g, respectively; FAP, 1.1 ± 0.1 %IA/g (P = 0.9805)/1.1 ± 0.1 %IA/g (P = 0.7446) versus 1.0 ± 0.2 %IA/g, respectively. Conclusion: In healthy mice, biodistribution of small theranostic ligands after intraperitoneal/subcutaneous application is nearly equivalent to that after intravenous injection. Subcutaneous administration resulted in the highest absolute SSTR tumor and tumor-to-organ uptake as compared with the intravenous route, warranting further clinical assessment.

Enzalutamide Enhances PSMA Expression of PSMA-Low Prostate Cancer.

Prostate-specific membrane antigen (PSMA)-directed radioligand therapy (RLT) prolongs overall survival in men with metastatic castration-resistant prostate cancer (mCRPC). However, men with low PSMA expression are excluded from RLT. We explored the effect of androgen receptor blockade with enzalutamide on PSMA expression. Assessment of PSMA and androgen receptor (AR) expression on the human PC cell lines 22Rv1, C4-2, and LNCaP by immunohistochemistry and flow cytometry revealed low (22Rv1) and high (C4-2 and LNCaP) PSMA expression, and high, comparable AR positivity. Treatment with enzalutamide increased PSMA levels in 22Rv1, C4-2, and LNCaP (2.2/2.3/2.6-fold, p = 0.0005/0.03/0.046) after one week compared to DMSO-treated controls as assessed by flow cytometry. NOD/Scid mice bearing 22Rv1 tumors were treated with enzalutamide for two weeks. Positron emission tomography/computed tomography (PET/CT) demonstrated higher tumor uptake of 68Ga-PSMA after enzalutamide treatment (p = 0.004). Similarly, a clinical case with low baseline PSMA avidity demonstrated increased uptake of 68Ga-PSMA after enzalutamide on PET/CT and post-therapeutic 177Lu-PSMA scintigraphy in a patient with mCRPC. Enzalutamide induced PSMA expression in the 22Rv1 xenograft model and in an mCRPC patient, both with low baseline tumoral PSMA levels. Therefore, enzalutamide pre-treatment might render patients with low PSMA expression eligible for 177Lu-PSMA RLT.

Imaging Inflammation with Positron Emission Tomography.

The impact of inflammation on the outcome of many medical conditions such as cardiovascular diseases, neurological disorders, infections, cancer, and autoimmune diseases has been widely acknowledged. However, in contrast to neurological, oncologic, and cardiovascular disorders, imaging plays a minor role in research and management of inflammation. Imaging can provide insights into individual and temporospatial biology and grade of inflammation which can be of diagnostic, therapeutic, and prognostic value. There is therefore an urgent need to evaluate and understand current approaches and potential applications for imaging of inflammation. This review discusses radiotracers for positron emission tomography (PET) that have been used to image inflammation in cardiovascular diseases and other inflammatory conditions with a special emphasis on radiotracers that have already been successfully applied in clinical settings.