Breast cancer is the most prevalent type of cancer among women worldwide. There are several recommended methods of breast cancer prevention, including chemoprevention. There are several approved drugs used to prevent breast cancer occurrence or recurrence and metastasizing. There are also a number of new substances undergoing clinical trials and at the stage of initial study. Studies suggest that dietary factors play a crucial role in breast cancer etiology. Epidemiological studies indicate that in particular vegetables from the Brassicaceae family are a rich source of chemopreventive substances, with sulforaphane (SFN) being one of the most widely studied and characterized. This review discusses potential applicability of SFN in breast cancer chemoprevention. A comprehensive review of the literature on the impact of SFN on molecular signalling pathways in breast cancer and breast untransformed cells is presented. The presented results of in vitro and in vivo studies show that this molecule has a potential to act as a preventive molecule either to prevent disease development or recurrence and metastasizing, and as a compound protecting normal cells against the toxic effects of cytostatics. Finally, the still scanty attempts to develop an improved analog are also presented and discussed.

Female breast cancer is the most deadly cancer in women worldwide. The triple-negative breast cancer subtype therapies, due to the lack of specific drug targets, are still based on systemic chemotherapy with doxorubicin, which is burdened with severe adverse effects. To enhance therapeutic success and protect against systemic toxicity, drug carriers or combination therapy are being developed. Thus, an innovative liposomal formulation containing doxorubicin and the main nutraceutical, sulforaphane, has been developed. The anticancer efficacy and safety of the proposed liposomal formulation was evaluated in vivo, in a 4T1 mouse model of triple-negative breast cancer, and the mechanism of action was determined in vitro, using triple-negative breast cancer MDA-MB-231 and non-tumorigenic breast MCF-10A cell line. The elaborated drug carriers were shown to efficiently deliver both compounds into the cancer cell and direct doxorubicin to the cell nucleus. Incorporation of sulforaphane resulted in a twofold inhibition of tumor growth and the potential of up to a fourfold reduction in doxorubicin concentration due to the synergistic interaction between the two compounds. Sulforaphane was shown to increase the accumulation of doxorubicin in the nuclei of cancer cells, accompanied by inhibition of mitosis, without affecting the reactive oxygen species status of the cell. In normal cells, an antagonistic effect resulting in less cytotoxicity was observed. In vivo results showed that sulforaphane incorporation yielded not only cardioprotective, but also nephro- and hepatoprotective effects. The results of the research revealed the prospects of applying sulforaphane as a component of liposomal doxorubicin in triple-negative breast cancer chemotherapy.

Combination therapy is based on the beneficial effects of pharmacodynamic interaction (synergistic or additive) between combined drugs or substances. A considerable group of candidates for combined treatments are natural compounds (e.g., isothiocyanates) and their analogs, which are tested in combination with anticancer drugs. We tested the anticancer effect of the combined treatment of isothiocyanate 2-oxohexyl isothiocyanate and 5-fluorouracil in colon and prostate cancer cell lines. The type of interaction was described using the Chou-Talalay method. The cytostatic and cytotoxic activities of the most promising combined treatments were investigated. In conclusion, we showed that combined treatment with 5-fluorouracil and 2-oxohexyl isothiocyanate acted synergistically in colon cancer. This activity is dependent on the cytostatic properties of the tested compounds and leads to the intensification of their individual cytotoxic activity. The apoptotic process is considered to be the main mechanism of cytotoxicity in this combined treatment.

Twelve tricarbonyl rhenium(I) complexes in the ‘2 + 1’ system with the anionic bidentate N,O-donor ligand (deprotonated 8-hydroxyquinoline (HQ) or its 2-methyl (MeHQ) or 5-chloro (ClHQ) derivative) and neutral N-donor diazoles (imidazole (Him), 2-methylimidazole (MeHim), 3,5-dimethylpyrazole (Hdmpz), and 3-phenylpyrazole (HPhpz)) were synthesized: [Re(CO)₃(L_N,O)L_N] (L_N,O = Q⁻, MeQ⁻, ClQ⁻; L_N = Him, MeHim, Hdmpz, HPhpz). Their crystal structures were determined by the scXRD method, compared with the DFT-calculated ones, and characterized by analytical (EA) and spectroscopic techniques (FT-IR, NMR, and UV-Vis) interpreted with DFT and TD-DFT calculations. Most of the Re(I) complexes did not show relevant antibacterial activity against Gram-negative and Gram-positive bacterial strains. Only [Re(CO)₃(MeQ)Him] demonstrated significant action 4-fold better against Gram-negative Pseudomonas aeruginosa than the free MeHQ ligand. The cytotoxicity of the compounds was estimated using human acute promyelocytic leukemia (HL-60), ovarian (SKOV-3), prostate (PC-3), and breast (MCF-7) cancer, and breast non-cancerous (MCF-10A) cell lines. Only HQ and ClHQ ligands and [Re(CO)₃(Q)Hdmpz] complex had good selectivity toward MCF-7 cell line. HL-60 cells were sensitive to all complexes (IC₅₀ = 1.5–14 μM). Still, pure HQ and ClHQ ligands were slightly more active than the complexes.

Triple-negative breast cancer (TNBC) represents aggressive phenotype with limited treatment options due to the lack of drug targets. Natural compounds are extensively studied regarding their potential to alter the efficacy of cancer treatment Among them sulforaphane – an isothiocyanate of natural origin, was shown to be a hormetic compound, that may exert divergent effects: cytoprotective or cytotoxic depending on its concentrations. Thus, the aim of this study was to determine the effect of its low, dietary concentrations on the proliferation and migration of the TNBC cells in the in vivo and in vitro 2D and 3D model. Results of the in vivo experiment showed up to 31% tumor growth inhibition after sulforaphane treatment associated with lowered proliferating potential of cancer cells, reduced areas of necrosis, and changed immune cell type infiltration, showing less malignant type of tumor in contrast to the non-treated group. Also, the study revealed that sulforaphane decreased the number of lung metastases. The in vitro study confirmed that SFN inhibited cell migration, but only in cells derived from 3D spheroids, not from 2D in vitro cultures. The results show a specific role of sulforaphane in the case of cells released from the TNBC primary tumor and its environment.

The understanding of the mechanism of Topo I inhibition by organic ligands is a crucial source of information that has led to the design of more effective and safe pharmaceuticals in oncological chemotherapy. The vast number of inhibitors that have been studied in this respect over the last decades have enabled the creation of a concept of an ‘interfacial inhibitor’, thereby describing the machinery of Topo I inhibition. The central module of action of this machinery is the interface of a Topo I/DNA/inhibitor ternary complex. Most of the ‘interfacial inhibitors’ are primarily kinetic inhibitors that form molecular complexes with an “on–off” rate timing; therefore, all of the contacts between the inhibitor and both the enzyme and the DNA are essential to keep the complex stable and reduce the “off rate”. To test this hypothesis, we designed the compound using a C-9-(N-(2′-hydroxyethyl)amino)methyl substituent in an SN38 core, with a view that a flexible substituent may bind inside the nick of a model of the DNA and stabilize the complex, leading to a reduction in the “off rate” of a ligand in a potential ternary complex in vivo. Using docking analysis and molecular dynamics, free energy calculations on the level of the MM-PBSA and MM-GBSA model, here we presented the in silico-calculated structure of a ternary complex involving the studied compound 1. This confirmed our suggestion that compound 1 is situated in a groove of the nicked DNA model in a few conformations. The number of hydrogen bonds between the components of a ternary complex was established, which strengthens the complex and supports our view. The docking analysis and free energy calculations for the receptor structures which were obtained in the MD simulations of the ternary complex 1/DNA/Topo I show that the binding constant is stronger than it was for similar complexes with TPT, CPT, and SN38, which are commonly considered as strong Topo I inhibitors. The binary complex structure 1/DNA was calculated and compared with the experimental results of a complex that was in a solution. The analysis of the cross-peaks in NOESY spectra allowed us to assign the dipolar interactions between the given protons in the calculated structures. A DOSY experiment in the solution confirmed the strong binding of a ligand in a binary complex, having a K_a of 746 mM⁻¹, which was compared with a K_a of 3.78 mM⁻¹ for TPT. The MALDI-ToF MS showed the presence of the biohybrid, thus evidencing the occurrence of DNA alkylation by compound 1. Because of it having a strong molecular complex, alkylation is the most efficient way to reduce the “on–off” timing as it acts as a tool that causes the cog to brake in a working gear, and this is this activity we want to highlight in our contribution. Finally, the Topo I inhibition test showed a lower IC₅₀ of the studied compound than it did for CPT and SN38.