Macrophages - vectors for a novel nanoparticle anti-cancer therapy

Fascinating new research into refractory metastatic cancer shows promise for macrophage-borne anti-cancer nanoparticle therapy.

A multi-centre team led by The Houston Methodist Research Institute postulated that the predominant cell in the tumor environment - macrophages - may have a central role in hypovascularised tissues to aid targeted delivery of nanoparticles loaded with cytotoxic drug. Importantly, unaffected tissue in vivo has significantly lower numbers of macrophages.

They developed a 3-D in vitro model that clearly showed improved efficacy for paclitaxel (complexed with albumin nanoparticles) in the presence of macrophages.

This work should be the basis for powerful new advances in tumor-targeted drug delivery, with initial interest in breast cancer-derived liver metastases.

Far-red viability probe DRAQ7 was utilised to report cell death in their model system. DRAQ7 has, elsewhere, been shown to be compatible with real-time and with 3D cell health monitoring and cytotoxicity assays as well as nanoparticle-based research. Importantly, it does not synergize with nor inhibit drug action.

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Reference:
Enhanced performance of macrophage-encapsulated nanoparticle albumin-bound-paclitaxel in hypo-perfused cancer lesions.

Leonard, F., Curtis, L.T., Yesantharao, P., Tanei, T., Alexander, J.F., Wu, M., Lowengrub, J., Liu, X., Ferrari, M., Yokoi, K., Frieboes, H.B., and Godin, B.

Nanoscale (2016) 8: 12544-12552 DOI:10.1039/C5NR07796F

Listening to cells! A new diagnostics tool?

Scientists in the laboratory of Prof. Michael Kolios at Ryerson University in Toronto have developed a novel methodology for the rapid identification of circulating tumor cells that might have applications in diagnostics.

In their recent paper, Moore, et al. modified an acoustic microscope with a 532 nm laser.  Ultrasound backscatter signals were used to determine cell radii.  Cells were also DRAQ5-stained to label nuclei.  The unique properties of DRAQ5 facilitated generation of photoacoustic signals from the cell nuclei to permit measurement of their radii.  In this work cancer cell lines MCF-7 and HT-29 were utilised to gain model representative data for homogenous populations.

The authors have postulated that in a liquid biopsy non-malignant hematopoietic cells will have significantly different radii (generating a useful nuclear:cytoplasmic ratio) when compared to malignant CTC's.

DRAQ5 benefitted the detection platform since it allows direct labeling of nucleated cells without fixation or permeabilization.  This occurs rapidly even at room temperature, with stoichiometry.  Significantly, DRAQ5's characteristics preferentially mediate a photo-acoustic signal that is otherwise not possible with fluorophores.

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Reference:

Moore, M.J., Strohm, E.M. and Kolios, M.C., 2015, October. Evaluation of the morphological parameters of cancer cells using high-frequency ultrasound and photoacoustics. In Ultrasonics Symposium (IUS), 2015 IEEE International (pp. 1-4). IEEE.

Malignant cells in CSF: diagnostic & prognostic value in Leptomeningeal Carcinomatosis

Clinical researchers from centres of excellence across Spain have described a flow cytometric method to robustly detect tumour epithelial cells in cerebrospinal fluid (CSF) of patients with leptomeningeal carcinomatosis (LC).

Subirá et al. used DRAQ5(TM) to label nucleated cells in CSF and therefore discriminate these cells from debris, avoiding the need for sample processing that might otherwise impact cell integrity, cell loss or absolute enumeration.

CSF samples were collected in EDTA with Transfix (Cytomark) for preservation and transportation.

In parallel steps one fraction of CSF was labeled with DRAQ5 and supplemented by counting beads to enumerate total nucleated cell burden.  A further CSF fraction was centrifuged to pellet the cells, firstly stained with a pair of epithelial-cell adhesion molecule (EpCAM) antibodies, separately labeled with FITC and PE, and then labeled with DRAQ5.  This combination allowed discrimination of malignant (EpCam-positive) epithelial cells from the non-malignant (EpCam-negative) inflammatory cells; lymphocytes, monocytes, polymorphonuclear cells identified according to their relative FSC/SSC scatter properties.

Use of DRAQ5 is simple, ideal for such procedures.  Being supplied in aqueous solution, preparation for use is straightforward. DRAQ5 is entirely cell permeant, labeling nucleated cells in complex samples within a few minutes, and without any subsequent wash steps.  Its spectral properties (far-red fluorescent) mean it has no spectral overlap with FITC/PE antibody pairs avoiding compensation issues.

In summary, the authors suggest that a CSF burden of EpCam+ cells of above 8% was a useful further diagnostic parameter and was clinically significant in terms of both overall survival and in identifying patients that may benefit from additional therapy.  This should be the subject of further validations studies.

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Reference:

Diagnostic and prognostic significance of flow cytometry immunophenotyping in patients with leptomeningeal carcinomatosis.

D. Subirá, M. Simó, J. Illán, C. Serrano,S. Castañón, R. Gonzalo, J. J. Granizo,M. Martínez-García, M. Navarro,J. Pardo, et al.

Clin Exp Metastasis (2015) 32: 383-391    DOI 10.1007/s10585-015-9716-3