Evaluation of fluorophore-tethered platinum complexes to monitor the fate of cisplatin analogs

Abstract

The platinum drugs cisplatin, carboplatin, and oxaliplatin are highly utilized in the clinic and as a consequence have been extensively studied in the laboratory setting, sometimes by generating fluorophore-tagged analogs. Here, we synthesized two Pt(II) complexes containing ethane-1,2-diamine ligands linked to a BODIPY fluorophore, and compared their biological activity with previously reported Pt(II) complexes conjugated to carboxyfluorescein and carboxyfluorescein diacetate. The cytotoxicity and DNA-damage capacity of Pt-fluorophore complexes was compared to cisplatin, and the Pt-BODIPY complexes were found to be more cytotoxic with reduced cytotoxicity in cisplatin-resistant cells. Microscopy revealed a predominately cytosolic localization, with nuclear distribution at higher concentrations. Spheroids grown from parent and resistant cells revealed penetration of Pt-BODIPY into spheroids, and retention of the cisplatin-resistant spheroid phenotype. While most activity profiles were retained for the Pt-BODIPY complexes, accumulation in resistant cells was only slightly affected, suggesting that some aspects of Pt-fluorophore cellular pharmacology deviate from cisplatin.

Enhancer of zeste homolog 2 promotes cisplatin resistance by reducing cellular platinum accumulation

“…In addition to quantitative techniques for measuring intracellular platinum content, such as FAAS, inductively coupled plasma mass spectrometry, and mass cytometry, the application of fluorescently tagged mimics brought us one step closer to tracking the intracellular drug content. BODIPY‐Pt is the platinum conjugate that bears characteristics most similar to cDDP: it is active against parental cells but less cytotoxic to resistant cells in both monolayer culture and spheroids, it produces DNA damage at a concentration approximately 1.5‐fold its IC 50 (the same as cDDP), and it accumulates less in cDDP‐resistant cells compared to cDDP‐sensitive cells . Even with such promising attributes, we were fully aware that BODIPY‐Pt might provide only limited information on the real fate of intracellular cDDP.…”

“…BODIPY-Pt is the platinum conjugate that bears characteristics most similar to cDDP: it is active against parental cells but less cytotoxic to resistant cells in both monolayer culture and spheroids, it produces DNA damage at a concentration approximately 1.5fold its IC 50 (the same as cDDP), and it accumulates less in cDDPresistant cells compared to cDDP-sensitive cells. [27][28][29] Even with such promising attributes, we were fully aware that BODIPY-Pt might provide only limited information on the real fate of intracellular cDDP. Despite a preference for the mitochondria, 28 BODIPY-Pt was retained at the cell membrane much longer than expected, as evidenced by strong membrane signals observed even at later time points when overall intracellular intensity started to diminish.…”

Development of a novel carboplatin like cytoplasmic trackable near infrared fluorophore conjugate via strain-promoted azide alkyne cycloaddition

“…[14] Specifically a number of Pt(II) anticancer type compounds have been reported where boron-fluorescent dipyrromethene (BODIPY) moieties have been tethered to Pt centres via prior direct covalent modification of the ammine carrier ligands. For instance Miller et al developed BODIPY tethered Pt complexes for high resolution of cancer in vivo, [15] Hall and coworkers to monitor the fate of cisplatin analogues, [16] [16,17] Furthermore a number of Pt complexes which offer a general synthetic approach to the functionalization of Pt centres have been developed, including those that possess reactive azide handles that facilitate click reactions, Figure 3 (a-c). [6,18] The 6-azidohexanoato ligands in 3 (c) were clicked with azadibenzocyclooctyne (ADIBO, Figure 3d) derivatives for example including the near-infrared fluorescent reporter, Cy5.5, which was used to visualize the cellular uptake of Pt in live prostate cancer cells.…”

Metal-based BODIPY derivatives as multimodal tools for life sciences

“…Thus, in order to observe simply the intracellular accumulation site of metal-based drugs, different fluorescent-labeled analogues have been synthesized and tested. When compared with similar fluorescein-containing platinum complexes, the BODIPY analogues proved to have antiproliferative properties closer by the ones of cisplatin making them more reliable for mechanistic studies [42]. This reason, combined to the attractive photoluminescent properties of BODIPYs, has made them very popular for labeling metallodrugs.…”