Effects of Enzymatic Activation on the Distribution of Fluorescently Tagged MMP-2 Cleavable Peptides in Cancer Cells and Spheroids

A peptide tagged at the N-terminus with FITC, at the C-terminus with coumarin-343, and incorporating a sequence selectively cleaved by the matrix metalloproteinase, MMP-2, was synthesized to investigate the effect of peptide cleavage on both cellular accumulation and distribution in cancer cell spheroids. The peptide was shown by HPLC and mass spectroscopy to be cleaved in the presence of MMP-2 at the expected site. The cellular and spheroid distribution of each of the fragments was monitored using confocal fluorescence microscopy. The intact peptide had minimal accumulation in 2D-cultured DLD-1 cells that do not express MMP-2 in these conditions. Following addition of serum containing MMP-2 to the cell media, the cleaved C-terminal fragment was seen to enter the cells, while the N-terminal fragment remained extracellular, evidently blocked by the presence of the FITC group. 3D culture of DLD-1 cells as spheroids resulted in measurable MMP-2 activity. Different distribution patterns of the two fluorophores were seen in spheroids treated with the intact peptide, consistent with cleavage occurring. Different rates of accumulation of each of the fragments were observed within the spheroid over time, which is attributed to the extent of accumulation and sequestration of the fragments by cells residing in the periphery of the spheroids. The outcomes suggest that tumor-associated enzymes have the potential to modify the distribution of peptides and peptide fragments in solid tumors by modifying the cellular uptake of those peptides

Influence of Equatorial and Axial Carboxylato Ligands on the Kinetic Inertness of Platinum(IV) Complexes in the Presence of Ascorbate and Cysteine and within DLD‑1 Cancer Cells

The rapid and premature reduction of platinum­(IV) complexes in vivo is a significant impediment to these complexes being successfully employed as anticancer prodrugs. This study investigates the influence of the platinum­(IV) coordination sphere on the ease of reduction of the platinum center in various biological contexts. In the presence of the biological reductants, ascorbate and cysteine, platinum­(IV) complexes with dicarboxylato equatorial ligands were observed to exhibit lower reduction potentials and slower reduction rates than analogous platinum­(IV) complexes with dichlorido equatorial ligands. Diaminetetracarboxylatoplatinum­(IV) complexes exhibited unusually long half-lives in the presence of excess reductants; however, the complexes exhibited moderate potency in vitro, indicative of rapid reduction within the intracellular environment. By use of XANES spectroscopy, <i>trans</i>-[Pt­(OAc)₂(ox)­(en)] and <i>trans</i>-[PtCl₂­(OAc)₂(en)] were observed to be reduced at a similar rate within DLD-1 cancer cells. This large variability in kinetic inertness of diamine­tetracarboxylato­platinum­(IV) complexes in different biological contexts has significant implications for the design of platinum­(IV) prodrugs

Dual Targeting of Hypoxic and Acidic Tumor Environments with a Cobalt(III) Chaperone Complex

The rational design of prodrugs for selective accumulation and activation in tumor microenvironments is one of the most promising strategies for minimizing the toxicity of anticancer drugs. Manipulation of the charge of the prodrug represents a potential mechanism to selectively deliver the prodrug to the acidic tumor microenvironment. Here we present delivery of a fluorescent coumarin using a cobalt­(III) chaperone to target hypoxic regions, and charged ligands for pH selectivity. Protonation or deprotonation of the complexes over a physiologically relevant pH range resulted in pH dependent accumulation of the fluorophore in colon cancer cells. Furthermore, in a spheroid solid tumor model, the anionic complexes exhibited preferential release of the fluorophore in the acidic/hypoxic region. By fine-tuning the physicochemical properties of the cobalt–chaperone moiety, we have demonstrated selective drug release in the acidic and hypoxic tumor microenvironment