Facile synthesis and18F-radiolabeling of α4β1-specific LLP2A-aryltrifluoroborate peptidomimetic conjugates

Article abstract of DOI:10.1016/j.bmcl.2016.08.011

The peptidomimetic, LLP2A, is a specific, high-affinity ligand for α₄β₁integrin receptors. Previously, several PEGylated LLP2A conjugates were evaluated in vivo as imaging agents for the detection of lymphoma, leukemia, multiple myel

Full text of DOI:10.1016/j.bmcl.2016.08.011

Bioorganic & Medicinal Chemistry Letters xxx (2016) xxx–xxx
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Facile synthesis and 18F-radiolabeling of
a4b1-specific
LLP2A-aryltrifluoroborate peptidomimetic conjugates
Daniel Walker a, Ying Li a, Áron Roxin a, Paul Schaffer b, Michael J. Adam b, David M. Perrin a,
⇑
a Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
b Triumf, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
The peptidomimetic, LLP2A, is a specific, high-affinity ligand for
a
4b1 integrin receptors. Previously,
Received 18 May 2016
Revised 4 August 2016
Accepted 5 August 2016
Available online xxxx
several PEGylated LLP2A conjugates were evaluated in vivo as imaging agents for the detection of lym-
phoma, leukemia, multiple myeloma and melanoma tumours via NIR-fluorescence, 111In-SPECT, and
64Cu- and 68Ga-PET imaging. Despite these successes, to date there is no report of an 18F-labeled LLP2A
conjugate. Notably, fluorine-18 is a preferred radionuclide for PET imaging, yet its short half-life and gen-
eral inactivity under aqueous conditions present challenges for peptide labeling. A simple method for
labeling complex biomolecules can be achieved with arylboronic acids that readily capture aqueous
Keywords:
Peptidomimetic
Radiotracer
Integrin receptor
F-18
[
18F]-fluoride ion resulting in an 18F-labeled aryltrifluoroborate ([18F]-ArBFÀ3 ) radioprosthetic group.
Herein, we present the first radiosynthesis of an 18F-labeled LLP2A conjugate by both one-step 18F‐label-
ing and one-pot two-step 18F-labeling post-‘click’ conjugation of the 18F-alkynyl-ArBFÀ3 prosthetic.
Competition with a fluorescent conjugate of LLP2A demonstrated specific binding of the non-radioactive
isotopolog ArBFÀ3 -PEG2-LLP2A to
a4b1 integrin-expressing MOLT-4 leukemia cells, as evidenced and
confirmed by fluorescence microscopy. This work provides a key first step in the development of an
expanding library of [18F]-R-BF3À-LLP2A radiotracers for PET imaging.
Ó 2016 Elsevier Ltd. All rights reserved.
Integrins are heterodimeric proteins consisting of non-cova-
lently associated and b subunits that link distinct extracellular
and can contribute to angiogenesis,5,26 and tumour
metastasis.5,21,26
a
matrix proteins to the cytoskeleton, of which two dozen subtypes
play essential roles in cell adhesion, cell mobility, and signal trans-
duction for normal cellular and tissue function.1–3 Many cancers
overexpress particular integrins to promote tumour cell migration,
angiogenesis, tumour growth, metastasis, and drug resistance.3
Crystallographic structural elucidations of the binding domains of
The peptidomimetic, LLP2A, discovered by one-bead-one-
compound (OBOC) library screening, shows extraordinarily high-
affinity (IC50 = 2 pM) to the
study reported in vivo NIR-fluorescence imaging activity of a
a
4b1 integrin receptor.27 A subsequent
Cy5.5-modified PEGylated LLP2A conjugate to visualize a4b1 inte-
grin-overexpressing MOLT-4 tumour xenografts.28 LLP2A deriva-
tives containing extended PEG spacers, as well as dimers and
tetramers thereof were affixed to metal chelators for one-step
labeling with [111In]-indium that demonstrated successful in vivo
imaging.29 Their report showed that extending the PEG length
integrins, namely for a a axb2 have each shown that
Vb3,4 IIbb3,5 and
integrins contain extracellular ligand binding domains. Hence
these are key targets for imaging and therapy, especially the inte-
grins
pared to healthy adult epithelial cells.3
More specifically, the
aVb3, a5b1, aVb6, a4b1, that are highly overexpressed com-
reduced
a4b1 integrin receptor binding, while multimers of the
a
4b1 integrin, or very late antigen-4 (VLA-
LLP2A ligand enhanced binding affinities in vitro. Nevertheless,
biodistribution studies revealed that multimeric constructs
showed enhanced kidney retention and high muscle retention.
Subsequent reports on radiometallated LLP2A-chelator conjugates,
labeled either with [64Cu]-copper for PET or [99mTc]-technetium for
SPECT, revealed bone metastasis of breast carcinoma,30 non-
Hodgkin lymphoma,31 multiple myeloma,32 primary melanoma
tumours,33 and melanoma metastases.34 In each report, a modified
PEG4-spacer first reported by Lam et al. was used.27
4), is involved in lympho-hemopoiesis,6,7 leukocyte trafficking,8
and cell motility9 primarily via VCAM-1 binding and the down-
stream signalling resulting from such interactions.10 Several
reports have revealed that the
a4b1 integrin plays pivotal roles in
promoting the progression of osteosarcomas,11 multiple myelo-
mas,12–15 lymphomas,16–18 leukemias19,20 and melanomas21–25
⇑
Corresponding author. Tel.: +1 604 822 0567.
E-mail address: dperrin@chem.ubc.ca (D.M. Perrin).
http://dx.doi.org/10.1016/j.bmcl.2016.08.011
0960-894X/Ó 2016 Elsevier Ltd. All rights reserved.
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D. Walker et al. / Bioorg. Med. Chem. Lett. xxx (2016) xxx–xxx
These promising studies indicate the potential for using LLP2A
synthesize LLP2A using previously described methods.27 Briefly,
HBTU and DIPEA in DMF afforded efficient amide coupling within
1 h at room temperature for each residue. Fmoc cleavage was
achieved using piperidine in DMF. These methods were used to
sequentially couple the residues Fmoc-Ach-OH, Fmoc-Aad(OtBu)-
OH, and Fmoc-Lys(Dde)-OH to provide resin-PEG2-Ach-Fmoc (1),
resin-PEG2-Ach-Aad(OtBu)-Fmoc (2), and resin-PEG2-Ach-Aad
(OtBu)-Lys(Dde)-Fmoc (3), respectively (Scheme 1). The urea, 2-(4-
(3-o-tolylureido)phenyl)acetic acid (4) (Fig. S1), was synthesized
as previously reported27and coupled to 3 using the aforementioned
conditions to produce resin-PEG2-Ach-Aad(OtBu)-Lys(Dde)-[2-(4-
(3-o-tolylureido)phenyl)acetyl] (5). After Dde deprotection of 5
for imaging several cancers, made possible by the facility of radio-
metal chelation. Yet various potential disadvantages of radiometals
including lower resolution, lower specific activity, increased
radiotoxicity, higher costs, challenges to scalable production, and
the possibility for off-target transchelation in vivo would suggest
the need for a radiofluorinated version of LLP2A. Surprisingly, to
date, there has been no report of an 18F-labeled LLP2A. Previously,
we demonstrated that peptide-boronic acid bioconjugates
effectively capture aqueous
one-pot-two-step click labeling to give the corresponding
[
18F]-fluoride for one-step and
[
18F]-ArBFÀ3 -bioconjugates to several ligands including biotin,35
marimastat,36,37 bisRGD,38 RGD,39 and bombesin.40 In these cases,
radiochemical yields (RCYs) ranged from 15% to 60% and specific
activities (SAs), which depend on the ratio of NCA [18F]-fluoride
with hydrazine, 3-(3-pyridyl)acrylic acid was coupled to the e–
NH2 of Lys to provide resin-PEG2-Ach-Aad(OtBu)-Lys(3-(3-pyri-
dyl)acrylyl)-[2-(4-(3-o-tolylureido)phenyl)acetyl] (6). Treatment
with (3:7) HFIP/DCM and preparatory TLC purification then pro-
ion to
[ lmol. Most
19F]-fluoride ion, ranged from 0.1–15 Ci/
importantly, corresponding in vivo images showed specific target
binding and good serum stability with minimal bone uptake. Here,
we apply this labeling method to the LLP2A scaffold to afford the
first-ever examples of 18F-labeled LLP2A-bioconjugates. The
synthesis, radiosynthesis, and in vitro binding properties form
the basis of this Letter.
To begin, O‐bis‐(aminoethyl)ethylene glycol trityl resin was
chosen for the solid-phase peptide synthesis (SPPS) of the PEGy-
lated LLP2A; this strategy affords a C-terminal amide-linked PEG2
spacer terminated with a primary amine for conjugation upon
resin cleavage following SPPS. The focus of this Letter is to present
the first 18F-labeling of LLP2A conjugates, and to investigate their
targeting specificity in vitro. Therefore, the PEG2 linker would not
influence 18F-labeling, allows the facile introduction of a standard
spacer at the beginning of peptide synthesis, and was not foreseen
to hinder in vitro binding. Standard Fmoc-chemistry was used to
vided 20.03 lmol of LLP2A-PEG2-NH2 (7) for an overall yield of
7%. Compound 7 was identified using HRMS and the purity
(>95%) was assessed by RP-HPLC analysis (Fig. S2).
The prosthetic, 2,4,6-trifluoro-3-(4,4,5,5-tetraphenyl-1,2,3-
dioxaborolan-2-yl)benzoic acid (8), was synthesized as previously
described41 and characterized by ESI-MS, 1H NMR (Fig. S3) and
19F NMR (Fig. S4). The tetraphenylpinacol (TPP) boronate ester, 8,
was conjugated to the terminal PEG2-NH2 of the LLP2A, 7, using
EDC–HCl in the presence of HOBt-hydrate in pyridine-THF. The
OtBu group was removed in the presence of TFA to provide ArB
(TPP)-PEG2-LLP2A (9) (Scheme 2). The identity and purity (>95%)
of 9 was confirmed by HRMS and RP-HPLC analysis, respectively
(Fig. S5). Compound 9 (100 nmol) was converted to the nonra-
dioactive trifluoroborate derivative, ArBFÀ3 -PEG2-LLP2A (10), as
previously reported for the conversion of arylboronylte-
traphenylpinacolates into aryltrifluoroborates.35,37 The identity of
Scheme 1. Synthesis of (7). Reagents and conditions: (a) Fmoc-Ach-OH, HBTU, DIPEA, DMF, 1 h, RT. (b) (i) 2 Â (1:4) piperidine/DMF, 10 min, RT. (ii) Fmoc-Aad(OtBu)-OH,
HBTU, DIPEA, DMF, 1 h, RT. (c) (i) 2 Â (1:4) piperidine/DMF, 10 min, RT. (ii) Fmoc-Lys(Dde)-OH, HBTU, DIPEA, DMF, 1 h, RT. (d) (i) 2 Â (1:4) piperidine/DMF, 10 min, RT. (ii) 2-
(4-(3-(o-Tolyl)ureido)phenyl)acetic acid (4), HBTU, DIPEA, DMF, 1 h, RT. (e) (i) 2 Â 2% hydrazine in DMF, 4 min, RT. (ii) 3-(3-Pyridyl)acrylic acid, HBTU, DIPEA, DMF, 1 h, RT.
(iii) (3:7) HFIP/DCM, 30 min, RT.
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D. Walker et al. / Bioorg. Med. Chem. Lett. xxx (2016) xxx–xxx
3
Scheme 2. Synthesis of (11). Reagents and conditions: (a) (i) 2,4,6-Trifluoro-3-(4,4,5,5-tetraphenyl-1,2,3-dioxaborolan-2-yl)benzoic acid (8), EDC–HCl, HOBt–H2O, pyridine,
THF, 16 h, RT. (ii) (1:1) TFA/DCM, 1 h, RT. (b) (i) [18F]-Fluoride, THF, HCl(conc.), 1 h, RT. (ii) (5:45:50) NH4OH(conc.)/H2O/EtOH.
10 (the nonradioactive isotopolog not shown) was confirmed by
ESI-MS and was used as an HPLC standard (Fig. S6) for the subse-
quent analysis of its 18F-labeled counterpart. One-step aqueous
18F-labeling of 9 (100 nmol) was achieved using [18F]-fluoride ion
conversion of 40%. The quenched solution of 15 was then used to
dissolve 13. Copper-catalysed ‘click’ chemistry was used to conju-
gate the 18F-labeled alkynyl arytrifluoroborate (15) to the azide-
modified LLP2A derivative, 13. This was accomplished using Cu(II)
SO4 and sodium ascorbate within 36 min at room temperature
(Scheme 3). The solution was then analysed by RP-HPLC to assess
the conversion to [18F]-ArBF3À-triazolyl-(CH2)4-C(O)NH-PEG2-LLP2A
(16) (Fig. 1B). This analysis showed a ꢀ79% conversion of 15 to 16
post 18F-labeling, for an overall radiochemical conversion of ꢀ30%
by the described one-pot two-step 18F-labeling conditions with an
(995 l
Ci) and 750 nmol [19F]-fluoride ion in (1:4) HCl(conc.)/THF
within 1 h at room temperature. After quenching with diluted
NH4OH(aq) in EtOH, a sample was used for RP-HPLC analysis of
[
18F]-ArBFÀ3 -PEG2-LLP2A (11) (Fig. 1A). Radiochemical yields were
reproducibly found to be in the range of 15% with effective specific
activities of 3.9 mCi/ mol; activities that are low, in keeping with
l
sub-millicurie amounts of radioactivity used (Scheme 2).
effective specific activity of 18F = 1.31 mCi/
lmol.
To complement a one-step labeling via the conversion of an
arylboronate ester into an 18F-labeled aryltrifluoroborate, we also
sought a one-pot-two-step 18F-labeling. For this approach, we first
synthesized N3-(CH2)4-C(O)NH-PEG2-LLP2A (13) by coupling 7
with 5-azidopentanoic acid (12), which was synthesized in two
steps from commercially available 5-bromo ethyl pentanoate
(Fig. S7). This precursor was then treated with (1:1) TFA/DCM to
remove the OtBu protecting group to afford 13. The identity of 13
was confirmed by ESI-MS and the purity (>95%) was assessed by
RP-HPLC (Fig. S8). A 100 nmol sample of alkynyl-ArB(dan) (B
With methods in hand for 18F-labeling the LLP2A derivatives 9
and 13 either by a one-step direct labeling method or a one-pot
two-step reaction (respectively), a fluorescent derivative of 11
was prepared to investigate the
a4b1 integrin binding specificity
by fluorescence microscopy. Briefly, fluorescein isothiocyanate
(FITC) was conjugated to 7 under aqueous conditions (pH = 8.4)
after 12 h at 4 °C. This precursor was subjected to (1:1) TFA/DCM
to remove the OtBu protecting group and provided FITC-PEG2-
LLP2A (17). The identity of 17 was then confirmed by ESI-MS and
was characterized by UV–vis to illustrate the presence of the FITC
(dan) = diaminonaphthyl
borimidine)
(14)
as
previously
moiety (Fig. S10). The
assessed using 4b1-expressing human MOLT‐4 leukemia cells.
Fluorescence microscopy found significant binding of 17 following
1 h incubations of 1 M (Fig. 2A) and 400 M (Fig. 2B) of 17 (in
1 mL of TBS containing 1 mM Mn2+ and 10 mM glucose). As
expected, fluorescence was not observed when 100 M of the
a4b1 integrin binding specificity of 17 was
reported38,39 was 18F-labeled under aqueous conditions within
22 min at room temperature using 1.28 mCi of [18F]-fluoride in
(1:8) HCl(conc.)/THF. After quenching with diluted NH4OH(aq) in
EtOH, a sample was used for RP-HPLC analysis of [18F]-alkynyl-
ArBFÀ3 (15) (Fig. S9). This showed an overall radiochemical
a
l
l
l
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D. Walker et al. / Bioorg. Med. Chem. Lett. xxx (2016) xxx–xxx
Figure 1. Representative RP-HPLC radio-chromatogram analysis of (A) [18F]-ArBFÀ3 -PEG2-LLP2A (11, tR = 20.3 min) following one-step 18F-labeling and (B) [18F]-ArBFÀ3 -
triazolyl-(CH2)4-C(O)NH-PEG2-LLP2A (16, tR = 19.7 min) following one-pot two-step 18F-labeling using HPLC program 3 (with unreacted [18F]-alkynyl-ArBF3À (15) at
tR = 15.0 min and unreacted [18F]-fluoride at tR = 3.0–6.0 min).
Scheme 3. Synthesis of (16). Reagents and conditions: (a) (i) 5-Azidopentanoic acid (12), HBTU, DIPEA, DMF, 1 h, RT. (ii) (1:1) TFA/DCM, 1 h, RT. (b) (i) 18F-Alkynyl-ArBF3 (15),
Na-ascorbate(aq), CuSO4(aq), 36 min, RT. (ii) (5:45:50) NH4OH(conc.)/H2O/EtOH.
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D. Walker et al. / Bioorg. Med. Chem. Lett. xxx (2016) xxx–xxx
5
Figure 2. In vitro analysis of the binding and specificity of FITC-PEG2-LLP2A (17) to
well) were incubated with (A) 1 M of 17 for 1 h at 37 °C, (B) 400
M of 17 for 1 h at 37 °C, and (D) 100 M of 10 for 1 h at 37 °C, washed and incubated with 400 l
M of 17 for 1 h at 37 °C in TBS containing 1 mM Mn2+ and 10 mM glucose.
a
4b1-expressing MOLT-4 leukemia cells by fluorescence microscopy. Cells (1 Â 106 per
l
lM of 17 for 1 h at 37 °C, (C) 100 l
M of ArBFÀ3 -PEG2-LLP2A (10) for 1 h at 37 °C, washed and incubated with
1
l
l
non-fluorescent trifluoroborate, ArBFÀ3 -PEG2-LLP2A (10), was pre-
incubated with cells for 1 h before incubation with either 1
(Fig. 2C) or 400 M (Fig. 2D) of 17. While 1 M incubations of 17
were required to obtain sufficient fluorescence intensities for visu-
alizing cells, the relatively high concentration of 17 (400 M) was
chosen to illustrate that there was little fluorescence enhancement
compared to 1 M incubations—owing to the high binding affinity
of the LLP2A targeting moiety. Although a priori this ligand should
bind at much lower concentrations, we used higher concentrations
to ensure rapid on-rates and complete saturation on cells. These
in vitro fluorescence assays confirmed the binding specificity of
10 and also shows that this non-radioactive counterpart of 11
showed for several peptides and fluorophores that increasing the
amount of [18F]-fluoride ion activity and/or reducing the amount
of boronate conjugate, it is easy to achieve very high specific activ-
lM
l
l
ities (7–15 Ci/l
mol).42 While we have not explored the use of iso-
l
tope exchange herein, this technique also affords good-to-excellent
radiochemical yields at very high specific activities (up to
l
16 Ci/
[
lmol) when working with Curie-levels of no-carrier added
18F]-fluoride ion.43,44 There is nothing to suggest that this could
not be applied to LLP2A for future imaging studies. Henceforth,
future efforts will involve optimizing the 18F-labeling conditions
to improve radiochemical yields and the specific activity of 11
and 16. In addition, we will explore the utility of other organotri-
fluoroborates that we have recently disclosed for imaging45,46 with
an eye to tuning the tumour uptake and pharmacokinetics of
has over ꢀ4Â the binding affinity to
a4b1 integrin receptors
in vitro compared to the fluorescent derivative, 17. Therefore, this
shows that the 18F-labeled counterpart of 10, 11, will also have
18F-labeled LLP2A-trifluoroborate bioconjugates with
grin-overexpressing tumour models.
a4b1 inte-
specificity to
To the best of our knowledge, we report the first 18F-labeling of
the 4b1 integrin-specific LLP2A peptidomimetic. Herein, we have
a4b1 integrin receptors.
a
Acknowledgements
used facile boronate-based 18F-labeling in the context of one-step
labeling and one-pot-two-step click labeling to prepare two 18F-
labeled bioconjugates of the integrin-binding peptidomimetic,
LLP2A. The one-step 18F-labeling procedure afforded effective
specific activities ꢀ3 times greater than the one-pot-two-step.
However, the latter procedure provided ꢀ2 times higher radio-
chemical yields than the former method. Although a one-step
method would arguably be of greater interest and utility, because
others have preferred one-pot-two-step click methods for labeling,
we have featured this as well with similar success. While herein
radiolabeling was performed at low activity levels (ꢀ2 mCi), which
in turn resulted in low specific activities, we have previously
Financial support of this research provided by the Canadian
Institutes of Health Research and the Canadian Cancer Society
Research Initiative. D.W. held a PGSM fellowship from NSERC.
Supplementary data
Supplementary data (details for materials and equipment, syn-
thetic methods, structural characterization spectra, 18F-labeling
methods and characterizations, and in vitro binding study meth-
ods) associated with this article can be found, in the online version,
at http://dx.doi.org/10.1016/j.bmcl.2016.08.011.
Please cite this article in press as: Walker, D.; et al. Bioorg. Med. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.bmcl.2016.08.011

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D. Walker et al. / Bioorg. Med. Chem. Lett. xxx (2016) xxx–xxx
26. Garmy-Susini, B.; Avraamides, C. J.; Schmid, M. C.; Foubert, P.; Ellies, L. G.;
References and notes
Barnes, L.; Feral, C.; Papayannopoulou, T.; Lowy, A.; Blair, S. L. Cancer Res. 2010,
70, 3042.
27. Peng, L.; Liu, R. W.; Marik, J.; Wang, X. B.; Takada, Y.; Lam, K. S. Nat. Chem. Biol.
2006, 2, 381.
1. Barczyk, M.; Carracedo, S.; Gullberg, D. Cell Tissue Res. 2010, 339, 269.
2. Bouvard, D.; Pouwels, J.; De Franceschi, N.; Ivaska, J. Nat. Rev. Mol. Cell Biol.
2013, 14, 430.
28. Peng, L.; Liu, R.; Andrei, M.; Xiao, W.; Lam, K. S. Mol. Cancer Ther. 2008, 7, 432.
29. DeNardo, S. J.; Liu, R. W.; Albrecht, H.; Natarajan, A.; Sutcliffe, J. L.; Anderson,
C.; Peng, L.; Ferdani, R.; Cherry, S. R.; Lam, K. S. J. Nucl. Med. 2009, 50, 625.
30. Shokeen, M.; Zheleznyak, A.; Wilson, J. M.; Jiang, M. J.; Liu, R. W.; Ferdani, R.;
Lam, K. S.; Schwarz, J. K.; Anderson, C. J. J. Nucl. Med. 2012, 53, 779.
31. Zwingenberger, A. L.; Kent, M. S.; Liu, R. W.; Kukis, D. L.; Wisner, E. R.; DeNardo,
S. J.; Taylor, S. L.; Chen, X. C.; Lam, K. S. PloS One 2012, 7.
32. Soodgupta, D.; Hurchla, M. A.; Jiang, M.; Zheleznyak, A.; Weilbaecher, K. N.;
Anderson, C. J.; Tomasson, M. H.; Shokeen, M. PloS One 2013, 8.
33. Jiang, M.; Ferdani, R.; Shokeen, M.; Anderson, C. J. Nucl. Med. Biol. 2013, 40.
34. Beaino, W.; Anderson, C. J. J. Nucl. Med. 2014, 55, 1856.
35. Ting, R.; Harwig, C. W.; auf dem Keller, U.; McCormick, S.; Austin, P.; Overall, C.
M.; Adam, M. J.; Ruth, T. J.; Perrin, D. M. J. Am. Chem. Soc. 2008, 130, 12045.
36. Keller, U. A. D.; Bellac, C. L.; Li, Y.; Lou, Y. M.; Lange, P. F.; Ting, R.; Harwig, C.;
Kappelhoff, R.; Dedhar, S.; Adam, M. J.; Ruth, T. J.; Benard, F.; Perrin, D. M.;
Overall, C. M. Cancer Res. 2010, 70, 7562.
37. Li, Y.; Ting, R.; Harwig, C. W.; Keller, U. A. D.; Bellac, C. L.; Lange, P. F.; Inkster, J.
A. H.; Schaffer, P.; Adam, M. J.; Ruth, T. J.; Overall, C. M.; Perrin, D. M.
MedChemComm 2011, 2, 942.
38. Li, Y.; Liu, Z. B.; Lozada, J.; Wong, M. Q.; Lin, K. S.; Yapp, D.; Perrin, D. M. Nucl.
Med. Biol. 2013, 40, 959.
39. Li, Y.; Guo, J.; Tang, S.; Lang, L.; Chen, X.; Perrin, D. M. Am. J. Nucl. Med. Mol.
Imag. 2013, 3, 44.
40. Li, Y.; Liu, Z.; Pourghiasian, M.; Lin, K.-S.; Schaffer, P.; Benard, F.; Perrin, D. M.
Am. J. Nucl. Med. Mol. Imag. 2013, 3, 57.
41. Ting, R.; Lo, J.; Adam, M. J.; Ruth, T. J.; Perrin, D. M. J. Fluor. Chem. 2008, 129,
349.
42. Liu, Z. B.; Li, Y.; Lozada, J.; Schaffer, P.; Adam, M. J.; Ruth, T. J.; Perrin, D. M.
Angew. Chem., Int. Ed. 2013, 52, 2303.
43. Liu, Z.; Li, Y.; Lozada, J.; Lin, K.-S.; Schaffer, P.; Perrin, D. M. J. Label. Compd.
Radiopharm. 2012, 14, 491.
44. Liu, Z.; Li, Y.; Lozada, J.; Wong, M. Q.; Greene, J.; Lin, K.-S.; Yapp, D.; Perrin, D. M.
Nucl. Med. Biol. 2013, 40, 841.
45. Liu, Z.; Hundal-Jabal, N.; Wong, M.; Yapp, D.; Lin, K. S.; Benard, F.; Perrin, D. M.
MedChemComm 2014, 5, 171.
46. Liu, Z. B.; Pourghiasian, M.; Radtke, M. A.; Lau, J.; Pan, J. H.; Dias, G. M.; Yapp,
D.; Lin, K. S.; Benard, F.; Perrin, D. M. Angew. Chem., Int. Ed. 1880, 53, 11876.
3. Desgrosellier, J. S.; Cheresh, D. A. Nat. Rev. Cancer 2010, 10, 9.
4. Campbell, I. D.; Humphries, M. J. Cold Spring Harb. Perspect. Biol 2011, 3,
a004994.
5. Garmy-Susini, B.; Jin, H.; Zhu, Y.; Sung, R.-J.; Hwang, R.; Varner, J. J. Clin. Invest.
2005, 115, 1542.
6. Miyake, K.; Hasunuma, Y.; Yagita, H.; Kimoto, M. J. Cell. Biol. 1992, 119, 653.
7. Miyake, K.; Weissman, I.; Greenberger, J.; Kincade, P. J. Exp. Med. 1991, 173, 599.
8. Rose, D. M.; Han, J.; Ginsberg, M. H. Immunol. Rev. 2002, 186, 118.
9. Hsia, D. A.; Lim, S.-T.; Bernard-Trifilo, J. A.; Mitra, S. K.; Tanaka, S.; Den Hertog,
J.; Streblow, D. N.; Ilic, D.; Ginsberg, M. H.; Schlaepfer, D. D. Mol. Cell. Biol. 2005,
25, 9700.
10. Yusuf-Makagiansar, H.; Anderson, M. E.; Yakovleva, T. V.; Murray, J. S.; Siahaan,
T. J. Med. Res. Rev. 2002, 22, 146.
11. Marco, R. A.; Díaz-Montero, C. M.; Wygant, J. N.; Kleinerman, E. S.; McIntyre, B.
W. J. Cell. Biochem. 2003, 88, 1038.
12. Michigami, T.; Shimizu, N.; Williams, P. J.; Niewolna, M.; Dallas, S. L.; Mundy,
G. R.; Yoneda, T. Blood 2000, 96, 1953.
13. Hatano, K.; Kikuchi, J.; Takatoku, M.; Shimizu, R.; Wada, T.; Ueda, M.;
Nobuyoshi, M.; Oh, I.; Sato, K.; Suzuki, T. Oncogene 2009, 28, 231.
14. Olson, D. L.; Burkly, L. C.; Leone, D. R.; Dolinski, B. M.; Lobb, R. R. Mol. Cancer
Ther. 2005, 4, 91.
15. Sanz-rodríguez, F.; Teixidó, J. Leuk. Lymphoma 2001, 41, 239.
16. Drillenburg, P.; Pals, S. T. Blood 2000, 95, 1900.
17. Baldini, L.; Cro, L.; Calori, R.; Nobili, L.; Silvestris, I.; Maiolo, A. Blood 1992, 79,
2688.
18. Finn, W. G.; Singleton, T. P.; Schnitzer, B.; Ross, C. W.; Stoolman, L. M. Human
Pathol. 2001, 32, 66.
19. Matsunaga, T.; Takemoto, N.; Sato, T.; Takimoto, R.; Tanaka, I.; Fujimi, A.;
Akiyama, T.; Kuroda, H.; Kawano, Y.; Kobune, M. Nat. Med. 2003, 9, 1158.
20. Vincent, A.; Cawley, J.; Burthem, J. Blood 1996, 87, 4780.
21. Hart, I. R.; Birch, M.; Marshall, J. F. Cancer Metast. Rev. 1991, 10, 115.
22. Klemke, M.; Weschenfelder, T.; Konstandin, M. H.; Samstag, Y. J. Cell. Physiol.
2007, 212, 368.
23. Kuphal, S.; Bauer, R.; Bosserhoff, A.-K. Cancer Metast. Rev. 2005, 24, 195.
24. Schadendorf, D.; Gawlik, C.; Haney, U.; Ostmeier, H.; Suter, L.; Czarnetzki, B. M.
J. Pathol. 1993, 170, 429.
25. Schadendorf, D.; Heidel, J.; Gawlik, C.; Suter, L.; Czarnetzki, B. M. J. Natl. Cancer
Inst. 1995, 87, 366.
Please cite this article in press as: Walker, D.; et al. Bioorg. Med. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.bmcl.2016.08.011