Acute cellular and vascular responses to photodynamic therapy using EGFR-targeted nanobody-photosensitizer conjugates studied with intravital optical imaging and magnetic resonance imaging

Bruijn, H.S. de; Mashayekhi, V.; Schreurs, T.J.L.; Driel, P.B.A.A. van; Strijkers, G.J.; Diest, P.J. van; ... ; Oliveira, S. (2020)

Article / Letter to editor

Targeted photodynamic therapy (PDT) has the potential to selectively damage tumor tissue and to increase tumor vessel permeability. Here we characterize the tissue biodistribution of two EGFR-targeted nanobody-photosensitizer conjugates (NB-PS), the monovalent 7D12-PS and the biparatopic 7D12-9G8-PS. In addition, we report on the local and acute phototoxic effects triggered by illumination of these NB-PS which have previously shown to lead to extensive tumor damage.Methods: Intravital microscopy and the skin-fold chamber model, containing OSC-19-luc2-cGFP tumors, were used to investigate: a) the fluorescence kinetics and distribution, b) the vascular response and c) the induction of necrosis after illumination at 1 or 24 h post administration of 7D12-PS and 7D12-9G8-PS. In addition, dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) of a solid tumor model was used to investigate the microvascular status 2 h after 7D12-PS mediated PDT.Results: Image analysis showed significant tumor colocalization for both NB-PS which was higher for 7D12-9G8-PS. Intravital imaging showed clear tumor cell membrane localization 1 and 2 h after administration of 7D12-9G8-PS, and fluorescence in or close to endothelial cells in normal tissue for both NB-PS. PDT lead to vasoconstriction and leakage of tumor and normal tissue vessels in the skin-fold chamber model. DCE-MRI confirmed the reduction of tumor perfusion after 7D12-PS mediated PDT. PDT induced extensive tumor necrosis and moderate normal tissue damage, which was similar for both NB-PS conjugates. This was significantly reduced when illumination was performed at 24 h compared to 1 h after administration.Discussion: Although differences were observed in distribution of the two NB-PS conjugates, both led to similar necrosis. Clearly, the response to PDT using NB-PS conjugates is the result of a complex mixture of tumor cell responses and vascular effects, which is likely to be necessary for a maximally effective treatment.

• Targeted
• EGFR
• Nanobody
• Photosensitizer
• Photodynamic therapy
• Intravital microscopy

• All authors: Bruijn, H.S. de; Mashayekhi, V.; Schreurs, T.J.L.; Driel, P.B.A.A. van; Strijkers, G.J.; Diest, P.J. van; Lowik, C.W.G.M.; Seynhaeve, A.L.B.; Hagen, T.L.M. ten; Prompers, J.J.; Henegouwen, P.M.P.V.E.; Robinso, D.J.; Oliveira, S.
• Date: 2020-01-01
• Journal: Theranostics
• Volume: 10
• Issue: 5
• Pages: 2436 - 2452
• DOI: doi:10.7150/thno.37949
• Link: https://www.thno.org/v10p2436.htm