[225Ac]Ac- and [111In]In-DOTA-trastuzumab theranostic pair: cellular dosimetry and cytotoxicity in vitro and tumour and normal tissue uptake in vivo in NRG mice with HER2-positive human breast cancer xenografts.

BACKGROUND: Trastuzumab (Herceptin) has improved the outcome for patients with HER2-positive breast cancer (BC) but brain metastases (BM) remain a challenge due to poor uptake of trastuzumab into the brain. Radioimmunotherapy (RIT) with trastuzumab labeled with α-particle emitting, 225Ac may overcome this challenge by increasing the cytotoxic potency on HER2-positive BC cells. Our first aim was to synthesize and characterize [111In]In-DOTA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab as a theranostic pair for imaging and RIT of HER2-positive BC, respectively. A second aim was to estimate the cellular dosimetry of [225Ac]Ac-DOTA-trastuzumab and determine its cytotoxicity in vitro on HER2-positive BC cells. A third aim was to study the tumour and normal tissue uptake of [225Ac]Ac-DOTA-trastuzumab using [111In]In-DOTA-trastuzumab as a radiotracer in vivo in NRG mice with s.c. 164/8-1B/H2N.luc+ human BC tumours that metastasize to the brain. RESULTS: Trastuzumab was conjugated to 12.7 ± 1.2 DOTA chelators and labeled with 111In or 225Ac. [111In]In-DOTA-trastuzumab exhibited high affinity specific binding to HER2-positive SK-BR-3 human BC cells (KD = 1.2 ± 0.3 × 10-8 mol/L). Treatment with [225Ac]Ac-DOTA-trastuzumab decreased the surviving fraction (SF) of SK-BR-3 cells dependent on the specific activity (SA) with SF < 0.001 at SA = 0.74 kBq/µg. No surviving colonies were noted at SA = 1.10 kBq/µg or 1.665 kBq/µg. Multiple DNA double-strand breaks (DSBs) were detected in SK-BR-3 cells exposed to [225Ac]Ac-DOTA-trastuzumab by γ-H2AX immunofluorescence microscopy. The time-integrated activity of [111In]In-DOTA-trastuzumab in SK-BR-3 cells was measured and used to estimate the absorbed doses from [225Ac]Ac-DOTA-trastuzumab by Monte Carlo N-Particle simulation for correlation with the SF. The dose required to decrease the SF of SK-BR-3 cells to 0.10 (D10) was 1.10 Gy. Based on the D10 reported for γ-irradiation of SK-BR-3 cells, we estimate that the relative biological effectiveness of the α-particles emitted by 225Ac is 4.4. Biodistribution studies in NRG mice with s.c. 164/8-1B/H2N.luc+ human BC tumours at 48 h post-coinjection of [111In]In-DOTA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab revealed HER2-specific tumour uptake (10.6 ± 0.6% ID/g) but spleen uptake was high (28.9 ± 7.4% ID/g). Tumours were well-visualized by SPECT/CT imaging using [111In]In-DOTA-trastuzumab. CONCLUSION: We conclude that [225Ac]Ac-DOTA-trastuzumab exhibited potent and HER2-specific cytotoxicity on SK-BR-3 cells in vitro and HER2-specific uptake in s.c. 164/8-1B/H2N.luc+ human BC tumours in NRG mice, and these tumours were imaged by SPECT/CT with [111In]In-DOTA-trastuzumab. These results are promising for combining [111In]In-DOTA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab as a theranostic pair for imaging and RIT of HER2-positive BC.

Macroscopic Banding Pattern of Collagen Gel Formed by a Diffusion-Reaction Process.

Shapes and patterns observed in internal organs and tissues are reproducibly and robustly produced over a long distance (up to millimeters in length). The most fundamental remaining question is how these long geometries of shape and pattern form arise from the genetic message. Recent studies have demonstrated that extracellular matrix (ECM) critically participates as a structural foundation on which cells can organize and communicate. ECMs may be a key to understanding the underlying mechanisms of long-distance patterning and morphogenesis. However, previous studies in this field mainly focused on the complexes and interaction of cells and ECM. This paper pays particular attention to ECM and demonstrates that collagen, a major ECM component, natively possesses the reproducible and definite patterning ability reaching centimeter-scale length. The macroscopic pattern consists of striped transparent layers. The observation under crossed Nicols demonstrates that the layers consist of alternately arranged polarized and unpolarized parts. Confocal fluorescence microscopy studies revealed that the polarized and unpolarized segments include collagen-rich and -poor regions, respectively. The patterning process was proposed based on the Liesegang banding formation, which are mineral precipitation bands formed in hydrogel matrixes. These findings will give hints to the questions about long-distance cell alignment and provide new clues to artificially control cell placement over micron size in the field of regenerative medicine.

Dose predictions for [177Lu]Lu-DOTA-panitumumab F(ab')2 in NRG mice with HNSCC patient-derived tumour xenografts based on [64Cu]Cu-DOTA-panitumumab F(ab')2 - implications for a PET theranostic strategy.

BACKGROUND: Epidermal growth factor receptors (EGFR) are overexpressed on many head and neck squamous cell carcinoma (HNSCC). Radioimmunotherapy (RIT) with F(ab')2 of the anti-EGFR monoclonal antibody panitumumab labeled with the ß-particle emitter, 177Lu may be a promising treatment for HNSCC. Our aim was to assess the feasibility of a theranostic strategy that combines positron emission tomography (PET) with [64Cu]Cu-DOTA-panitumumab F(ab')2 to image HNSCC and predict the radiation equivalent doses to the tumour and normal organs from RIT with [177Lu]Lu-DOTA-panitumumab F(ab')2. RESULTS: Panitumumab F(ab')2 were conjugated to DOTA and complexed to 64Cu or 177Lu in high radiochemical purity (95.6 ± 2.1% and 96.7 ± 3.5%, respectively) and exhibited high affinity EGFR binding (Kd = 2.9 ± 0.7 × 10- 9 mol/L). Biodistribution (BOD) studies at 6, 24 or 48 h post-injection (p.i.) of [64Cu]Cu-DOTA-panitumumab F(ab')2 (5.5-14.0 MBq; 50 µg) or [177Lu]Lu-DOTA-panitumumab F(ab')2 (6.5 MBq; 50 µg) in NRG mice with s.c. HNSCC patient-derived xenografts (PDX) overall showed no significant differences in tumour uptake but modest differences in normal organ uptake were noted at certain time points. Tumours were imaged by microPET/CT with [64Cu]Cu-DOTA-panitumumab F(ab')2 or microSPECT/CT with [177Lu]Lu-DOTA-panitumumab F(ab')2 but not with irrelevant [177Lu]Lu-DOTA-trastuzumab F(ab')2. Tumour uptake at 24 h p.i. of [64Cu]Cu-DOTA-panitumumab F(ab')2 [14.9 ± 1.1% injected dose/gram (%ID/g) and [177Lu]Lu-DOTA-panitumumab F(ab')2 (18.0 ± 0.4%ID/g) were significantly higher (P < 0.05) than [177Lu]Lu-DOTA-trastuzumab F(ab')2 (2.6 ± 0.5%ID/g), demonstrating EGFR-mediated tumour uptake. There were no significant differences in the radiation equivalent doses in the tumour and most normal organs estimated for [177Lu]Lu-DOTA-panitumumab F(ab')2 based on the BOD of [64Cu]Cu-DOTA-panitumumab F(ab')2 compared to those estimated directly from the BOD of [177Lu]Lu-DOTA-panitumumab F(ab')2 except for the liver and whole body which were modestly underestimated by [64Cu]Cu-DOTA-panitumumab F(ab')2. Region-of-interest (ROI) analysis of microPET/CT images provided dose estimates for the tumour and liver that were not significantly different for the two radioimmunoconjugates. Human doses from administration of [177Lu]Lu-DOTA-panitumumab F(ab')2 predicted that a 2 cm diameter HNSCC tumour in a patient would receive 1.1-1.5 mSv/MBq and the whole body dose would be 0.15-0.22 mSv/MBq. CONCLUSION: A PET theranostic strategy combining [64Cu]Cu-DOTA-panitumumab F(ab')2 to image HNSCC tumours and predict the equivalent radiation doses in the tumour and normal organs from RIT with [177Lu]Lu-DOTA-panitumumab F(ab')2 is feasible. RIT with [177Lu]Lu-DOTA-panitumumab F(ab')2 may be a promising approach to treatment of HNSCC due to frequent overexpression of EGFR.

Clinical Implications of Folate Transport in the Central Nervous System.

Folates are essential for key biosynthetic processes in mammalian cells and play a crucial role in the maintenance of central nervous system homeostasis. Mammals lack the metabolic capacity for folate biosynthesis; hence, folate requirements are largely met through dietary sources. To date, three major folate transport pathways have been characterized: the folate receptors (FRs), reduced folate carrier (RFC), and proton-coupled folate transporter (PCFT). This article reviews current knowledge on the role of folate transport systems in mediating folate delivery to vital tissues, particularly the brain, and how these pathways are modulated by various regulatory mechanisms. We will also briefly highlight the clinical significance of cerebral folate transport in relation to neurodevelopmental disorders associated with folate deficiency.

Electrodeposited ZnO-nanowire/Cu2O photovoltaic device with highly resistive ZnO intermediate layer.

Cl-doped ZnO-nanowire (Cl:ZnO-nws)/Cu2O photovoltaic devices were prepared by electrodeposition in aqueous solutions, and the effects of the insertion of the highly resistive ZnO (i-ZnO) layer has been demonstrated by an improvement of the photovoltaic performance. The Cl:ZnO-nws and i-ZnO layer were prepared by electrodeposition in a zinc chloride aqueous solution with saturated molecular oxygen and simple zinc nitrate aqueous solution, respectively. The i-ZnO layer was directly deposited on the Cl:ZnO-nws and suppressed the electrodeposition of the Cu2O layer on the Cl:ZnO-nws. The insertion of the i-ZnO layer between the Cl:ZnO-nws and Cu2O layers induced an improvement in the photovoltaic performance from 0.40 to 1.26% with a 0.35 V open circuit voltage, 7.1 mA·cm(-2) short circuit current density, and 0.52 fill factor due to the reduction of the recombination loss.