Programmed death–ligand 1 (PD-L1) expression on tumor cells is essential for T cell impairment, and PD-L1 blockade therapy has shown unprecedented durable responses in several clinical studies. Although higher expression of PD-L1 on tumor cells is associated with a better immune response after Ab blockade, some PD-L1–negative patients also respond to this therapy. In the current study, we explored whether PD-L1 on tumor or host cells was essential for anti–PD-L1–mediated therapy in 2 different murine tumor models. Using real-time imaging in whole tumor tissues, we found that anti–PD-L1 Ab accumulates in tumor tissues, regardless of the status of PD-L1 expression on tumor cells. We further observed that, while PD-L1 on tumor cells was largely dispensable for the response to checkpoint blockade, PD-L1 in host myeloid cells was essential for this response. Additionally, PD-L1 signaling in defined antigen-presenting cells (APCs) negatively regulated and inhibited T cell activation. PD-L1 blockade inside tumors was not sufficient to mediate regression, as limiting T cell trafficking reduced the efficacy of the blockade. Together, these findings demonstrate that PD-L1 expressed in APCs, rather than on tumor cells, plays an essential role in checkpoint blockade therapy, providing an insight into the mechanisms of this therapy.

Background Programmed death-ligand 1 (PD-L1) expression in metastatic renal cell carcinoma (RCC) correlates with a worse prognosis, but whether it also predicts responsiveness to anti-PD-1/PD-L1 therapy remains unclear. Most studies of PD-L1 are limited by evaluation in primary rather than metastatic sites, and in biopsy samples, which may not be representative. These limitations may be overcome with immuno–positron emission tomography (iPET), an emerging tool allowing the detection of cell surface proteins with radiolabeled antibodies. Here, we report iPET studies of PD-L1 in a preclinical tumorgraft model of clear cell RCC (ccRCC) from a patient who had a favorable response to anti-PD-1 therapy. Case presentation A 49-year-old man underwent a cytoreductive nephrectomy in 2017 of a right kidney tumor invading into the adrenal gland that was metastatic to the lungs and a rib. Histological analyses revealed a ccRCC of ISUP grade 4 with extensive sarcomatoid features. IMDC risk group was poor. Within two hours of surgery, a tumor sample was implanted orthotopically into NOD/SCID mice. Consistent with an aggressive tumor, a renal mass was detected 18 days post-implantation. Histologically, the tumorgraft showed sarcomatoid differentiation and high levels of PD-L1, similar to the patient’s tumor. PD-L1 was evaluated in subsequently transplanted mice using iPET and the results were compared to control mice implanted with a PD-L1-negative tumor. We labeled atezolizumab, an anti-PD-L1 antibody with a mutant Fc, with zirconium-89. iPET revealed significantly higher ⁸⁹Zr-atezolizumab uptake in index than control tumorgrafts. The patient was treated with high-dose IL2 initially, and subsequently with pazopanib, with rapidly progressive disease, but had a durable response with nivolumab. Conclusions To our knowledge, this is the first report of non-invasive detection of PD-L1 in renal cancer using molecular imaging. This study supports clinical evaluation of iPET to identify RCC patients with tumors deploying the PD-L1 checkpoint pathway who may be most likely to benefit from PD-1/PD-L1 disrupting drugs.

Purpose: Immune checkpoint inhibitors (ICI) targeting the programmed cell death protein 1 and its ligand (PD-1/PD-L1) have transformed the treatment paradigm for metastatic renal cell carcinoma (RCC). However, response rates to ICIs as single agents or in combination vary widely and predictive biomarkers are lacking. Possibly related to the heterogeneity and dynamic nature of PD-L1 expression, tissue-based methods have shown limited value. Immuno–positron emission tomography (immunoPET) may enable noninvasive, comprehensive, and real-time PD-L1 detection. Herein, we systematically examined the performance of immunoPET for PD-L1 detection relative to IHC in an RCC patient-derived tumorgraft (TG) platform. Experimental Design: Eight independent RCC TGs with a wide range of PD-L1 expression (0%–85%) were evaluated by immunoPET. Uptake of 89Zr-labeled atezolizumab ([89Zr]Zr-DFO-ATZ) was compared with PD-L1 expression in tumors by IHC through double-blind analyses. Clinical outcomes of ICI-treated patients whose TGs were examined were analyzed to evaluate the clinical role of immunoPET in RCC. Results: ImmunoPET with [89Zr]Zr-DFO-ATZ (day 6/7 postinjection) revealed a statistically significant association with PD-L1 IHC assays (P = 0.0014; correlation ρXY = 0.78). Furthermore, immunoPET can be used to assess the heterogeneous distribution of PD-L1 expression. Finally, studies in the corresponding patients (n = 4) suggest that PD-L1 signal may influence ICI responsiveness. Conclusions: ImmunoPET with [89Zr]Zr-DFO-ATZ may enable a thorough and dynamic assessment of PD-L1 across sites of disease. The power of immunoPET to predict ICI response in RCC is being explored in an ongoing clinical trial (NCT04006522).

Radiation therapy has emerged as an important modality to treat triple negative breast cancer (TNBC) and locoregional micro-metastases after breast conservation surgery. To alleviate the side effects caused by high radiation dose, we harness the radiosensitization effects exhibited by hollow gold nanoparticles (HAuNPs: hollow core with 50 nm diameter and 35 nm shell thickness) for efficacious radiotherapy of TNBC. In this work, we report a comparative study with 4 groups of mice bearing TNBC MDA-MB-231 xenografts: (A) HAuNPs + X-radiation, (B) saline + X-radiation, (C) HAuNPs, and (D) saline. The injection of HAuNPs was maintained at 2.8 mg of HAuNPs per gram of tumor tissue. A single dose of X-radiation (10 Gy, 225 kVp) resulted in a significant tumor growth delay in groups A and B when compared to the control groups C and D. Although no significant difference in tumor growth was observed between groups A and B, the combination treatment of HAuNPs + X-radiation exhibited a significantly prolonged overall survival (p < 0.05 vs. any other group). No adverse effects were observed with the use of HAuNPs as radiosensitizers. Taken together, we demonstrated the promising potential of using HAuNPs as radiosensitization agents for efficacious treatment of breast cancer.

We report the successful synthesis of monodispersed Cu₂S nanocrystals and the subsequent formation of highly ordered nanocrystal superlattices. The synthesis is performed under ambient air conditions using simple experimental setups, making the process both accessible and scalable. By systematically tuning the reaction temperature and duration, we demonstrate precise control over the nanocrystal size, which is crucial in achieving uniformity and monodispersity. Furthermore, we uncover a previously unidentified nanocrystal growth mechanism that plays a key role in producing highly monodisperse Cu₂S nanocrystals. This insight into the growth process enhances our fundamental understanding of nanocrystal formation and could be extended to the synthesis of other semiconductor nanomaterials. The self-assembly of these nanocrystals into superlattices is carefully examined using electron diffraction techniques, revealing the presence of pseudo-crystalline structures. The ordered arrangement of nanocrystals within these superlattices suggests strong interparticle interactions and opens up new possibilities to tailor their collective optical, electronic, and mechanical properties for potential applications in optoelectronics, nanomedicine, and energy storage.