Radium 223-mediated zonal cytotoxicity of prostate cancer in bone

No Thumbnail Available
File version
Author(s)
Dondossola, Eleonora
Casarin, Stefano
Paindelli, Claudia
De-Juan-Pardo, Elena M
Hutmacher, Dietmar W
Logothetis, Christopher J
Friedl, Peter
Griffith University Author(s)
Primary Supervisor
Other Supervisors
Editor(s)
Date
2019
Size
File type(s)
Location
License
Abstract

Background: Bone-targeting radiotherapy with Radium-223 (Rad-223), a radioisotope emitting genotoxic alpha-radiation with limited tissue penetrance (∼100 µm), prolongs the survival of patients with metastatic prostate cancer (PCa). Confoundingly, the clinical response to Rad-223 is often followed by detrimental relapse and progression, and whether Rad-223 causes tumor-cell directed cytotoxicity in vivo remains unclear. We hypothesized that limited radiation penetrance in situ defines outcome.

Methods: We tested Rad-223 overall response by PC3 and C4–2B human PCa cell lines in mouse bones (n = 5–18 tibiae per group). Rad-223 efficacy at subcellular resolution was determined by intravital microscopy analysis of dual-color fluorescent PC3 cells (n = 3–4 mice per group) in tissue-engineered bone constructs. In vivo data were fed into an in silico model to predict Rad-223 effectiveness in lesions of different sizes (1–27, 306 initial cells; n = 10–100 simulations) and the predictions validated in vivo by treating PCa tumors of varying sizes in bones (n = 10–14 tibiae per group). Statistical tests were performed by two-sided Student t test or by one-way ANOVA followed by Tukey’s post-hoc test.

Results: Rad-223 (385 kBq/kg) delayed the growth (means [SD]; comparison with control-treated mice) of PC3 (6.7 × 105 [4.2 × 105] vs 2.8 × 106 [2.2 × 106], P = .01) and C4–2B tumors in bone (7.7 × 105 [4.0 × 105] vs 3.5 × 106 [1.3 × 106], P < .001). Cancer cell lethality in response to Rad-223 (385 kBq/kg) was profound but zonally confined along the bone interface compared with the more distant tumor core, which remained unperturbed (day 4; 13.1 [2.3%] apoptotic cells, 0–100 µm distance from bone vs 3.6 [0.2%], >300 µm distance; P = .01). In silico simulations predicted greater efficacy of Rad-223 on single-cell lesions (eradication rate: 88.0%) and minimal effects on larger tumors (no eradication, 16.2% growth reduction in tumors of 27 306 cells), as further confirmed in vivo for PC3 and C4–2B tumors.

Conclusions: Micro-tumors showed severe growth delay or eradication in response to Rad-223, whereas macro-tumors persisted and expanded. The relative inefficacy in controlling large tumors points to application of Rad-223 in secondary prevention of early bone-metastatic disease and regimens co-targeting the tumor core.

Journal Title

Journal of the National Cancer Institute

Conference Title
Book Title
Edition
Volume
Issue
Thesis Type
Degree Program
School
Publisher link
Patent number
Funder(s)
Grant identifier(s)
Rights Statement
Rights Statement
Item Access Status
Note

This publication has been entered into Griffith Research Online as an Advanced Online Version.

Access the data
Related item(s)
Subject

Oncology and carcinogenesis

Persistent link to this record
Citation
Collections