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A comparative PET imaging study with the reversible and irreversible EGFR tyrosine kinase inhibitors [(11)C]erlotinib and [(18)F]afatinib in lung cancer-bearing mice.

Slobbe P, Windhorst AD, Stigter-van Walsum M, Smit EF, Niessen HG, Solca F, Stehle G, van Dongen GA, Poot AJ - EJNMMI Res (2015)

Bottom Line: Additionally, the effect of drug efflux transporter permeability glycoprotein (P-gp) on the tumor uptake of tracers was explored by therapeutic blocking with tariquidar.Under P-gp blocking conditions, no significant changes in tumor-to-background ratio were observed; however, [(18)F]afatinib demonstrated better tumor retention in all xenograft models.TKI-PET provides a method to image sensitizing mutations and can be a valuable tool to compare the distinguished targeting properties of TKIs in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, Amsterdam, 1081 HV The Netherlands ; Department of Otolaryngology/Head and Neck Surgery, VU University Medical Center, De Boelelaan 1117, Amsterdam, 1081 HV The Netherlands.

ABSTRACT

Background: Tyrosine kinase inhibitors (TKIs) have experienced a tremendous boost in the last decade, where more than 15 small molecule TKIs have been approved by the FDA. Unfortunately, despite their promising clinical successes, a large portion of patients remain unresponsive to these targeted drugs. For non-small cell lung cancer (NSCLC), the effectiveness of TKIs is dependent on the mutational status of epidermal growth factor receptor (EGFR). The exon 19 deletion as well as the L858R point mutation lead to excellent sensitivity to TKIs such as erlotinib and gefitinib; however, despite initial good response, most patients invariably develop resistance against these first-generation reversible TKIs, e.g., via T790M point mutation. Second-generation TKIs that irreversibly bind to EGFR wild-type and mutant isoforms have therefore been developed and one of these candidates, afatinib, has now reached the market. Whether irreversible TKIs differ from reversible TKIs in their in vivo tumor-targeting properties is, however, not known and is the subject of the present study.

Methods: Erlotinib was labeled with carbon-11 and afatinib with fluorine-18 without modifying the structure of these compounds. A preclinical positron emission tomography (PET) study was performed in mice bearing NSCLC xenografts with a representative panel of mutations: an EGFR-WT xenograft cell line (A549), an acquired treatment-resistant L858R/T790M mutant (H1975), and a treatment-sensitive exon 19 deleted mutant (HCC827). PET imaging was performed in these xenografts with both tracers. Additionally, the effect of drug efflux transporter permeability glycoprotein (P-gp) on the tumor uptake of tracers was explored by therapeutic blocking with tariquidar.

Results: Both tracers only demonstrated selective tumor uptake in the HCC827 xenograft line (tumor-to-background ratio, [(11)C]erlotinib 1.9 ± 0.5 and [(18)F]afatinib 2.3 ± 0.4), thereby showing the ability to distinguish sensitizing mutations in vivo. No major differences were observed in the kinetics of the reversible and the irreversible tracers in each of the xenograft models. Under P-gp blocking conditions, no significant changes in tumor-to-background ratio were observed; however, [(18)F]afatinib demonstrated better tumor retention in all xenograft models.

Conclusions: TKI-PET provides a method to image sensitizing mutations and can be a valuable tool to compare the distinguished targeting properties of TKIs in vivo.

No MeSH data available.


Related in: MedlinePlus

Immunohistochemical staining of NSCLC xenograft lines as used in PET studies. Images depicted at 5× magnification. Mutations: A549 (wild type), H1975 (L858R/T790M), and HCC827 (exon 19 deletion).
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Fig2: Immunohistochemical staining of NSCLC xenograft lines as used in PET studies. Images depicted at 5× magnification. Mutations: A549 (wild type), H1975 (L858R/T790M), and HCC827 (exon 19 deletion).

Mentions: To fully characterize these cell lines before the start of PET imaging studies, they were xenografted onto athymic nu/nu mice and immunohistochemistry and sequencing were performed on the xenograft material. EGFR expression was found in all lines (Figure 2) and although immunohistochemistry is a semi-quantitative technique, staining appeared most intense in HCC827 xenografts. The EGFR mutations of the xenografts, as described before, were confirmed by sequencing. Finally, the tumors were stained for the expression of P-gp, a drug efflux transporter, for which erlotinib and afatinib are known substrates [27,28]. The staining indicated that this efflux transporter was most extensively expressed by HCC827 xenografts.Figure 2


A comparative PET imaging study with the reversible and irreversible EGFR tyrosine kinase inhibitors [(11)C]erlotinib and [(18)F]afatinib in lung cancer-bearing mice.

Slobbe P, Windhorst AD, Stigter-van Walsum M, Smit EF, Niessen HG, Solca F, Stehle G, van Dongen GA, Poot AJ - EJNMMI Res (2015)

Immunohistochemical staining of NSCLC xenograft lines as used in PET studies. Images depicted at 5× magnification. Mutations: A549 (wild type), H1975 (L858R/T790M), and HCC827 (exon 19 deletion).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385286&req=5

Fig2: Immunohistochemical staining of NSCLC xenograft lines as used in PET studies. Images depicted at 5× magnification. Mutations: A549 (wild type), H1975 (L858R/T790M), and HCC827 (exon 19 deletion).
Mentions: To fully characterize these cell lines before the start of PET imaging studies, they were xenografted onto athymic nu/nu mice and immunohistochemistry and sequencing were performed on the xenograft material. EGFR expression was found in all lines (Figure 2) and although immunohistochemistry is a semi-quantitative technique, staining appeared most intense in HCC827 xenografts. The EGFR mutations of the xenografts, as described before, were confirmed by sequencing. Finally, the tumors were stained for the expression of P-gp, a drug efflux transporter, for which erlotinib and afatinib are known substrates [27,28]. The staining indicated that this efflux transporter was most extensively expressed by HCC827 xenografts.Figure 2

Bottom Line: Additionally, the effect of drug efflux transporter permeability glycoprotein (P-gp) on the tumor uptake of tracers was explored by therapeutic blocking with tariquidar.Under P-gp blocking conditions, no significant changes in tumor-to-background ratio were observed; however, [(18)F]afatinib demonstrated better tumor retention in all xenograft models.TKI-PET provides a method to image sensitizing mutations and can be a valuable tool to compare the distinguished targeting properties of TKIs in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, Amsterdam, 1081 HV The Netherlands ; Department of Otolaryngology/Head and Neck Surgery, VU University Medical Center, De Boelelaan 1117, Amsterdam, 1081 HV The Netherlands.

ABSTRACT

Background: Tyrosine kinase inhibitors (TKIs) have experienced a tremendous boost in the last decade, where more than 15 small molecule TKIs have been approved by the FDA. Unfortunately, despite their promising clinical successes, a large portion of patients remain unresponsive to these targeted drugs. For non-small cell lung cancer (NSCLC), the effectiveness of TKIs is dependent on the mutational status of epidermal growth factor receptor (EGFR). The exon 19 deletion as well as the L858R point mutation lead to excellent sensitivity to TKIs such as erlotinib and gefitinib; however, despite initial good response, most patients invariably develop resistance against these first-generation reversible TKIs, e.g., via T790M point mutation. Second-generation TKIs that irreversibly bind to EGFR wild-type and mutant isoforms have therefore been developed and one of these candidates, afatinib, has now reached the market. Whether irreversible TKIs differ from reversible TKIs in their in vivo tumor-targeting properties is, however, not known and is the subject of the present study.

Methods: Erlotinib was labeled with carbon-11 and afatinib with fluorine-18 without modifying the structure of these compounds. A preclinical positron emission tomography (PET) study was performed in mice bearing NSCLC xenografts with a representative panel of mutations: an EGFR-WT xenograft cell line (A549), an acquired treatment-resistant L858R/T790M mutant (H1975), and a treatment-sensitive exon 19 deleted mutant (HCC827). PET imaging was performed in these xenografts with both tracers. Additionally, the effect of drug efflux transporter permeability glycoprotein (P-gp) on the tumor uptake of tracers was explored by therapeutic blocking with tariquidar.

Results: Both tracers only demonstrated selective tumor uptake in the HCC827 xenograft line (tumor-to-background ratio, [(11)C]erlotinib 1.9 ± 0.5 and [(18)F]afatinib 2.3 ± 0.4), thereby showing the ability to distinguish sensitizing mutations in vivo. No major differences were observed in the kinetics of the reversible and the irreversible tracers in each of the xenograft models. Under P-gp blocking conditions, no significant changes in tumor-to-background ratio were observed; however, [(18)F]afatinib demonstrated better tumor retention in all xenograft models.

Conclusions: TKI-PET provides a method to image sensitizing mutations and can be a valuable tool to compare the distinguished targeting properties of TKIs in vivo.

No MeSH data available.


Related in: MedlinePlus