Doxorubicin-sensitive and -resistant colorectal cancer spheroid models: assessing tumor microenvironment features for therapeutic modulation

Optimization of Antiproliferative Properties of Triimine Copper(II) Complexes

Cu(II) complexes with 2,2':6',2″-terpyridines (terpy) and 2,6-bis(thiazol-2-yl)pyridines (dtpy) with 1- or 2-naphtyl and methoxy-naphtyl were synthesized to elucidate the impact of the triimine core, naphtyl linking mode, and presence of methoxy groups on the antiproliferative activity of [CuCl2(Ln)]. Their antiproliferative effect was analyzed in ovarian (A2780) and colorectal (HCT116) carcinomas and colorectal carcinoma resistant to doxorubicin (HCT116-DoxR) cell lines and in normal human fibroblasts. Among all complexes, the 1- and 2-naphtyl substituted terpy Cu(II) complexes (Cu1a and Cu1b) showed the strongest cytotoxicity, namely, in HCT116-DoxR 2Dcells and were also capable of inducing the loss of cell viability in 3D HCT116-DoxR spheroids. Their intracellular localization, capability to increase reactive oxygen species (ROS), and interaction with DNA (nonintercalative mode) trigger oxidative DNA cleavage leading to cell death by apoptosis and autophagy. Cu1a and Cu1b do not show in vivo toxicity in a chicken embryo and can interact with bovine serum albumin (BSA).

Effect of Periodate-Induced Cross-linking on Dual Anticancer Drug Release from Poly(2-isopropyl-2-oxazoline)/Tannic Acid-Based Layer-by-Layer Microparticles

This study reports, first, on the preparation and cross-linking of multilayers composed of poly(2-isopropyl-2-oxazoline-co-ethyleneimine) (PiPOX-PEI) and tannic acid (TA). PiPOX was synthesized by cationic ring-opening polymerization (CROP) and partially hydrolyzed, yielding a random copolymer PiPOX-PEI. It was then coassembled at the surface with TA using the layer-by-layer (LbL) technique. Multilayers were exposed to NaIO4 solution to induce covalent bond formation between PEI units of PiPOX-PEI and TA. Cross-linking with NaIO4 enhanced the stability of the multilayers, especially under basic conditions. Second, the potential of PiPOX-PEI and TA multilayers as a stimuli-responsive dual drug-releasing platform was examined using curcumin (CUR) and doxorubicin (DOX) as model drugs. These drugs were chosen as they can act in a combinatorial manner to increase cell death. The surface of CUR-containing CaCO3 microparticles was modified with PiPOX-PEI and TA multilayers and postloaded with DOX. We found that LbL particles could release DOX in a pH-responsive manner, whereas temperature-induced release was observed only when the temperature was raised above 40 °C. The DOX and CUR released from the LbL particles could act synergistically on HCT-116 cells. Cross-linking increased the DOX release from LbL particles but decreased the CUR release from the core. Corroborating the release data, the synergy observed with the non-cross-linked particles was lost with the cross-linked particles, and the decrease in the viability of HCT-116 cells was attributed mainly to the release of DOX. Overall, we describe here NaIO4-induced cross-linking of PiPOX-PEI/TA LbL films, the effects of pH, temperature, and cross-linking on DOX and CUR release from multilayers, and comparison of the combinatorial effect of DOX and CUR for cross-linked and non-cross-linked LbL microparticles through cell viability assays.

Copper(II) Complexes with 2,2':6',2″-Terpyridine Derivatives Displaying Dimeric Dichloro-μ-Bridged Crystal Structure: Biological Activities from 2D and 3D Tumor Spheroids to In Vivo Models

Eight 2,2':6',2″-terpyridines, substituted at the 4'-position with aromatic groups featuring variations in π-conjugation, ring size, heteroatoms, and methoxy groups, were employed to enhance the antiproliferative potential of [Cu2Cl2(R-terpy)2](PF6)2. Assessing the cytotoxicity in A2780 (ovarian carcinoma), HCT116 (colorectal carcinoma), and HCT116DoxR (colorectal carcinoma resistant to doxorubicin) and normal primary fibroblasts revealed that Cu(II) complexes with 4-quinolinyl, 4-methoxy-1-naphthyl, 2-furanyl, and 2-pyridynyl substituents showed superior therapeutic potential in HCT116DoxR cells with significantly reduced cytotoxicity in normal fibroblasts (42-129× lower). Besides their cytotoxicity, the Cu(II) complexes are able to increase intracellular ROS and interfere with cell cycle progression, leading to cell death by apoptosis and autophagy. Importantly, they demonstrated antimetastatic and antiangiogenic properties without in vivo toxicity. In accordance with their nuclear accumulation, the Cu(II) complexes are able to cleave pDNA and interact with bovine serum albumin, which is a good indication of their ability for internalization and transport toward tumor cells.

A Short Post-Reattachment Ultrasensitive Window of Time in Human Cancer Cells as Therapeutic Target of Prolonged Low-Dose Administration of Specific Compounds

Prolonged low-dose administration (PLDA) of several FDA-approved drugs for noncancer conditions or dietary compounds is associated with a lower incidence of specific types of cancers and with the lower formation of metastasis. However, the underlying mechanism is unknown; there is a discrepancy between the concentration of drugs needed to kill cancer cells in vitro and the actual serum levels (10 and >1000 times lower) found in patients. In this study, we evaluated the hypothesis that clonogenicity may be the target of PLDA. We compared the effect of nigericin (NIG) and menadione (MEN) on the human A549 and H460 lung and MCF-7 and MDA-MB-231 breast cancer cell lines using routine MTT and colony forming assays (CFA). The ability of both NIG and MEN to eliminate 100% of cancer cells was at least 2-10 times more potent in CFA compared to MTT assays. Our results revealed the existence of a short post-reattachment window of time when cancer cells growing at low density are more sensitive to PLDA of specific drugs likely by targeting clonogenic rather than proliferation pathways. This short ultrasensitive window of time (SUSWoT) was cell- and drug-type specific: the SUSWoT for NIG was present in H460, A549, and MDA-MB-231 cells but not evident in MCF-7 cells. Conversely, a similar SUSWoT for MEN was present in MCF-7, MDA-MD-231, and A549 cells but not evident in H460 cells. Our findings partially explain the decreased incidence of specific types of cancer by PLDA of FDA-approved drugs (or dietary compounds) for noncancer conditions.