Synovial sarcoma (SS) is a rare yet refractory soft‐tissue sarcoma that predominantly affects young adults. We show in a mouse model that radioimmunotherapy (RIT) with an α‐particle emitting anti‐Frizzled homolog 10 (FZD10) antibody, synthesized using the α‐emitter radionuclide astatine‐211 (211At‐OTSA101), suppresses the growth of SS xenografts more efficiently than the corresponding β‐particle emitting anti‐FZD10 antibody conjugated with the β‐emitter yettrium‐90 (90Y‐OTSA101). In biodistribution analysis, 211At was increased in the SS xenografts but decreased in other tissues up to 1 day after injection as time proceeded, albeit with a relatively higher uptake in the stomach. Single 211At‐OTSA101 doses of 25 and 50 μCi significantly suppressed SS tumor growth in vivo, whereas a 50‐μCi dose of 90Y‐OTSA101 was needed to achieve this. Importantly, 50 μCi of 211At‐OTSA101 suppressed tumor growth immediately after injection, whereas this effect required several days in the case of 90Y‐OTSA101. Both radiolabeled antibodies at the 50‐μCi dosage level significantly prolonged survival. Histopathologically, severe cellular damage accompanied by massive cell death was evident in the SS xenografts at even 1 day after the 211At‐OTSA101 injection, but these effects were relatively milder with 90Y‐OTSA101 at the same timepoint, even though the absorbed doses were comparable (3.3 and 3.0 Gy, respectively). We conclude that α‐particle RIT with 211At‐OTSA101 is a potential new therapeutic option for SS.
Arsenic contamination is a major environmental issue, as it may lead to serious health hazard. The reduced trivalent form of inorganic arsenic, arsenite, is in general more toxic to plants compared with the fully oxidized pentavalent arsenate. The uptake of arsenite in plants has been shown to be mediated through a large subfamily of plant aquaglyceroporins, nodulin 26-like intrinsic proteins (NIPs). However, the efflux mechanisms, as well as the mechanism of arsenite-induced root growth inhibition, remain poorly understood. Using molecular physiology, synchrotron imaging, and root transport assay approaches, we show that the cellular transport of trivalent arsenicals in
Arabidopsis thaliana
is strongly modulated by PIN FORMED 2 (PIN2) auxin efflux transporter. Root transport assay using radioactive arsenite, X-ray fluorescence imaging (XFI) coupled with X-ray absorption spectroscopy (XAS), and inductively coupled plasma mass spectrometry analysis revealed that
pin2
plants accumulate higher concentrations of arsenite in roots compared with the wild-type. At the cellular level, arsenite specifically targets intracellular sorting of PIN2 and thereby alters the cellular auxin homeostasis. Consistently, loss of PIN2 function results in arsenite hypersensitivity in roots. XFI coupled with XAS further revealed that loss of PIN2 function results in specific accumulation of arsenical species, but not the other metals such as iron, zinc, or calcium in the root tip. Collectively, these results suggest that PIN2 likely functions as an arsenite efflux transporter for the distribution of arsenical species
in planta
.
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