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McKenna et al Hypoxia in prostate cancer

drug from molecular profiling to potentially single pharmacodynamics readouts, such as that provided
cell functional analysis. Thus here we consider by a truncated 53BP1 double-strand reporter, recently
approaches aimed at developing novel and functional shown to accentuate the approach for in situ single
assays for tumor stratification. cell analysis of cancer therapeutics [68] . Applying
this PK-PD linked imaging at the single cell would
Many hypoxia-targeting small molecules, for example, provide the evidence and mechanisms essential for
[(18)F]FAZA, [(18)F]FMISO, [(18)F]EF5, and [(123) the development of HAP therapeutic strategies that
I]IAZA, have been shown to accrue selectively in address changing patterns of target presentation in
hypoxic cells. These positron emission tomography different cellular microenvironments, and prostate
molecular contrast agents have been extensively tissue architecture.
applied in clinical hypoxia imaging, including
cancer [63] . However the outstanding challenge is to BH3 PROFILING TO PREDICT CAPACITY FOR
multiplex these imaging readouts with the delivery CELL DEATH AT THE SINGLE CELL LEVEL
and conversion of prodrug in the same tumor and
package the acquisition and analysis algorithms such
that they offer pragmatic solutions for advancing our The primary action of the AQ4N and OCT1002
understanding of HAP bioavailability and conversion. metabolites is through DNA damage and subsequently
apoptosis. Despite much research into the molecular
Many bioactive molecules have chromophores [64] pathways that regulate cell death, the signalling
thus offering the prospect for tracking target networks involved are so complex that molecular
interactions through methods such as steady-state profiling of key pro-and anti-apoptotic players alone
fluorescence readouts, or determining fluorescence does not provide the predictive capability needed to
[69]
quenching properties and fluorescence lifetime assess chemo-responsiveness . Thus, functional
BH3 profiling would lead to the derivation of cell death
measurements for detecting drug tethering to target. fingerprinting, determining the sensitivity thresholds
Fluorescence life-time and quenching analyses can for apoptosis between and within heterogeneous
lead to a unique means for dissecting sub-resolution cancer cell populations. The underlying principle of
molecular interactions in situ [65] . For instance, BH3 profiling is that mitochondrial depolarization
recent spectroscopic investigations show molecular or subsequent processes such as BAK/BAX
properties of doxorubicin change due to alterations oligomerisation or cytochrome release following BH3
in the local environment, such as when the drug is peptide exposure serves as a functional biomarker
encapsulated to nanoparticles. Thus we suggest that for cellular response to pro-apoptotic cues. A recent
fluorescence imaging provides a powerful tool for technology innovation has led to the development
investigating drug delivery in tumor cells and tissue, and implementation of novel nano-tools (cross-linked
and further allows for the linking of multi-scalar stapled peptides) to aid the understanding of apoptotic
features of drug design, stability and metabolism responses using flow and image cytometry [70,71] .
together with the complexities imposed by the Feasibility studies have shown that BH3-derived
biological system including tissue penetration and peptides alkylated with azobenzene cross-linkers have
drug-target interactions. the ability to induce detectable physiological changes

paralleling the early events in apoptotic cell death. The
All these fluorescent modalities are very much objective now is to establish a validated BH3-profiling
applicable for the uHAPs such as AQ4N and OCT1002 pipeline suitable for sample stratification, using these
which are fluorescent due to the anthraquinone peptide BH3 pathway inducers and sensitizers [72] .
chromophore and detectable in vitro and in vivo [55,66] In short, BH3 profiling provides a functional readout
and also retained in tissue even after snap-freezing for the primed apoptotic state of a heterogenous
of xenograft material. Cryosections of frozen population of cells, again which can be directly linked
xenograft tumor tissue slices were examined for to drug bioreduction and retention at the single cell
AQ4 fluorescence and distribution by fluorescence level.
microscopy, alongside HPLC/mass spectroscopy
analysis [67] . To extend the concept further, the
efficiency of drug-target interaction of the prodrug is MOLECULAR PROFILING AND
driven by not only pharmacokinetic factors but a host BIOINFORMATIC ANALYSIS
of parallel cellular status and events that are required
to elicit the sought pharmacodynamic responses, The drive towards personalised medicine depends
which are also heterogeneously expressed through on the discovery of biomarkers which can allow
the tumor. Hence the requirement for in vivo molecular stratification of patients. Such information

Journal of Cancer Metastasis and Treatment ¦ Volume 4 ¦ March 1, 2018 7