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Relative Biological Effectiveness (RBE) of [Cu]Cu and [Lu]Lu-NOTA-panitumumab F (ab') radioimmunotherapeutic agents vs. γ-radiation for decreasing the clonogenic survival in vitro of human pancreatic ductal adenocarcinoma (PDAC) cells. | LitMetric
Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON M5S 3M2, Canada; Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2C1, Canada; Department of Medical Imaging, University of Toronto, Toronto, ON M5T 1W7, Canada. Electronic address:
Published: November 2023
AI Article Synopsis
Article Abstract
Introduction: Our objective was to compare [Cu]Cu-NOTA-panitumumab F(ab') and [Lu]Lu-NOTA-panitumumab F(ab') radioimmunotherapy (RIT) agents for decreasing the clonogenic survival fraction (SF) in vitro of EGFR-positive human pancreatic ductal adenocarcinoma (PDAC) cell lines and estimate the relative biological effectiveness (RBE) vs. γ-radiation (XRT).
Methods: EGFR-positive PDAC cell lines (AsPC-1, PANC-1, MIAPaCa-2, Capan-1) and EGFR-knockout PANC-1 EGFR KO cells were treated in vitro for 18 h with (0-19.65 MBq; 72 nmols/L) of [Cu]Cu-NOTA-panitumumab F(ab') or [Lu]Lu-NOTA-panitumumab F(ab') or XRT (0-8 Gy) followed by clonogenic assay. The SF was determined after culturing single treated cells for 14 d. Cell fractionation studies were performed for cells incubated with 1 MBq (72 nmols/L) of [Cu]Cu-NOTA-panitumumab F(ab') or [Lu]Lu-NOTA-panitumumab F(ab') for 1, 4, or 24 h to estimate the time-integrated activity (Ã) on the cell surface, cytoplasm, nucleus and medium. Radiation absorbed doses in the nucleus were calculated by multiplying à by S-factors calculated by Monte Carlo N Particle (MCNP) modeling using monolayer cell culture geometry. The SF of PDAC cells was plotted vs. dose and fitted to a linear quadratic model to estimate the dose required to decrease the SF to 0.1 (D). The D for RIT agents were compared to XRT to estimate the RBE. DNA double-strand breaks (DSBs) caused by [Cu]Cu-NOTA-panitumumab F(ab') or [Lu]Lu-NOTA-panitumumab F(ab') continuous exposure for 5 h or 20 h were probed by immunofluorescence for γ-H2AX. Relative EGFR expression of PDAC cells was assessed by flow cytometry (scored + to +++) and cell doubling times for untreated cells were determined.
Results: The D for [Cu]Cu-NOTA-panitumumab F(ab') ranged from 9.1 Gy (PANC-1) to 39.9 Gy (Capan-1). The D for [Lu]Lu-NOTA-panitumumab F(ab') ranged from 11.7 Gy (AsPC-1) to 170.8 Gy (Capan-1). The D for XRT ranged from 2.5 Gy (Capan-1) to 6.7 Gy (PANC-1 EGFR KO). D values were not correlated with EGFR expression over a relatively narrow range (++ to +++) or with cell doubling times. Based on D values, PANC-1 EGFR KO cells were 1.6-fold less sensitive than PANC-1 cells to [Cu]Cu-NOTA-panitumumab F(ab') and 1.9-fold less sensitive to [Lu]Lu-NOTA-panitumumab F(ab'). The RBE for [Cu]Cu-NOTA-panitumumab F(ab') ranged from 0.06 for Capan-1 cells to 0.45 for PANC-1 cells. The RBE for [Lu]Lu-NOTA-panitumumab F(ab') ranged from 0.015 for Capan-1 cells to 0.28 for AsPC-1 cells. DNA DSBs were detected in PDAC cells exposed to [Cu]Cu-NOTA-panitumumab F(ab') or [Lu]Lu-NOTA-panitumumab F(ab') but were not correlated with the SF of the cells.
Conclusions: We conclude that at the same dose delivered to the cell nucleus [Cu]Cu-NOTA-panitumumab F(ab') and [Lu]Lu-NOTA-panitumumab F(ab') were less radiobiologically effective than XRT for decreasing the SF of human PDAC cells, but [Cu]Cu-NOTA-panitumumab F(ab') was more cytotoxic than [Lu]Lu-NOTA-panitumumab F(ab') except for AsPC-1 cells which were more sensitive to [Lu]Lu-NOTA-panitumumab F(ab').
Advances In Knowledge And Implications For Patient Care: This study demonstrates that higher radiation doses may be required for RIT than XRT to achieve radiobiologically equivalent effects when used to treat PDAC.
