Cisplatin Protein Binding Partners and Their Relevance for Platinum Drug Sensitivity

Exploring the Potential of Metal-Based Candidate Drugs as Modulators of the Cytoskeleton

During recent years, accumulating evidence suggested that metal-based candidate drugs are promising modulators of cytoskeletal and cytoskeleton-associated proteins. This was substantiated by the identification and validation of actin, vimentin and plectin as targets of distinct ruthenium(II)- and platinum(II)-based modulators. Despite this, structural information about molecular interaction is scarcely available. Here, we compile the scattered reports about metal-based candidate molecules that influence the cytoskeleton, its associated proteins and explore their potential to interfere in cancer-related processes, including proliferation, invasion and the epithelial-to-mesenchymal transition. Advances in this field depend crucially on determining binding sites and on gaining comprehensive insight into molecular drug-target interactions. These are key steps towards establishing yet elusive structure-activity relationships.

The Application of an Extracellular Vesicle-Based Biosensor in Early Diagnosis and Prediction of Chemoresponsiveness in Ovarian Cancer

BACKGROUND

Ovarian cancer (OVCA) is the most fatal gynecological cancer with late diagnosis and plasma gelsolin (pGSN)-mediated chemoresistance representing the main obstacles to treatment success. Since there is no reliable approach to diagnosing patients at an early stage as well as predicting chemoresponsiveness, there is an urgent need to develop a diagnostic platform for such purposes. Small extracellular vesicles (sEVs) are attractive biomarkers given their potential accuracy for targeting tumor sites.

METHODS

We have developed a novel biosensor which utilizes cysteine-functionalized gold nanoparticles that simultaneously bind to cisplatin (CDDP) and plasma/cell-derived EVs, affording us the advantage of predicting OVCA chemoresponsiveness, and early diagnosis using surface-enhanced Raman spectroscopy.

RESULTS

We found that pGSN regulates cortactin (CTTN) content resulting in the formation of nuclear- and cytoplasmic-dense granules facilitating the secretion of sEVs carrying CDDP; a strategy used by resistant cells to survive CDDP action. The clinical utility of the biosensor was tested and subsequently revealed that the sEV/CA125 ratio outperformed CA125 and sEV individually in predicting early stage, chemoresistance, residual disease, tumor recurrence, and patient survival.

CONCLUSION

These findings highlight pGSN as a potential therapeutic target and provide a potential diagnostic platform to detect OVCA earlier and predict chemoresistance; an intervention that will positively impact patient-survival outcomes.

PD-1/PD-L1 and DNA Damage Response in Cancer

The application of immunotherapy for cancer treatment is rapidly becoming more widespread. Immunotherapeutic agents are frequently combined with various types of treatments to obtain a more durable antitumor clinical response in patients who have developed resistance to monotherapy. Chemotherapeutic drugs that induce DNA damage and trigger DNA damage response (DDR) frequently induce an increase in the expression of the programmed death ligand-1 (PD-L1) that can be employed by cancer cells to avoid immune surveillance. PD-L1 exposed on cancer cells can in turn be targeted to re-establish the immune-reactive tumor microenvironment, which ultimately increases the tumor's susceptibility to combined therapies. Here we review the recent advances in how the DDR regulates PD-L1 expression and point out the effect of etoposide, irinotecan, and platinum compounds on the anti-tumor immune response.

Glutathione S-Transferases S1, Z1 and A1 Serve as Prognostic Factors in Glioblastoma and Promote Drug Resistance through Antioxidant Pathways

The glutathione S-transferase (GST) family of detoxification enzymes can regulate the malignant progression and drug resistance of various tumors. Hematopoietic prostaglandin D synthase (HPGDS, also referred to as GSTS1), GSTZ1, and GSTA1 are abnormally expressed in multiple cancers, but their roles in tumorigenesis and development remain unclear. In this study, we used bioinformatics tools to analyze the connections of HPGDS, GSTZ1, and GSTA1 to a variety of tumors in genetic databases. Then, we performed biochemical assays in GBM cell lines to investigate the involvement of HPGDS in proliferation and drug resistance. We found that HPGDS, GSTZ1, and GSTA1 are abnormally expressed in a variety of tumors and are associated with prognoses. The expression level of HPGDS was significantly positively correlated with the grade of glioma, and high levels of HPGDS predicted a poor prognosis. Inhibiting HPGDS significantly downregulated GBM proliferation and reduced resistance to temozolomide by disrupting the cellular redox balance and inhibiting the activation of JNK signaling. In conclusion, this study suggested that HPGDS, GSTZ1, and GSTA1 are related to the progression of multiple tumors, and HPGDS is expected to be a prognostic factor in GBM.

Pt(IV) Prodrugs with Non-Steroidal Anti-inflammatory Drugs in the Axial Position

We report herein the design, synthesis, and biological investigation of a series of novel Pt(IV) prodrugs with non-steroidal anti-inflammatory drugs naproxen, diclofenac, and flurbiprofen, as well as these with stearic acid in the axial position. Six Pt(IV) prodrugs 5-10 were designed, which showed superior antiproliferative activity compared to cisplatin as well as an ability to overcome tumor cell line resistance to cisplatin. By tuning the drug lipophilicity via variation of the axial ligands, the most potent Pt(IV) prodrug 7 was obtained, with an enhanced cellular accumulation of up to 153-fold that of cisplatin and nanomolar cytotoxicity both in 2D and 3D cell cultures. Pt²⁺ species were detected at different depths of MCF-7 spheroids after incubation with Pt(IV) prodrugs using a Pt-coated carbon nanoelectrode. Cisplatin accumulation in vivo in the murine mammary EMT6 tumor tissue of BALB/c mice after Pt(IV) prodrug injection was proved electrochemically as well. The drug tolerance study on BALB/c mice showed good tolerance of 7 in doses up to 8 mg/kg.

Cytotoxic BODIPY-Appended Half-Sandwich Iridium(III) Complex Forms Protein Adducts and Induces ER Stress

Half-sandwich complexes of iridium(III) are currently being developed as anticancer drug candidates. In this context, we introduce IrBDP for which the C^N chelating phenyloxazoline ligand carries a fluorescent and lipophilic BODIPY reporter group, designed for intracellular tracking and hydrophobic compartment tropism. High-resolution analysis of cells cultured with IrBDP showed that it quickly permeates the plasma membrane and accumulates in the mitochondria and endoplasmic reticulum (ER), generating ER stress, dispersal of the Golgi apparatus, cell proliferation arrest and apoptotic cell death. Moreover, IrBDP forms fluorescent adducts with a subset of amino acids, namely histidine and cysteine, via coordination of N or S donor atoms of their side chains. Consistently, in vivo formation of covalent adducts with specific proteins is demonstrated, providing a molecular basis for the observed cytotoxicity and cellular response. Collectively, these results provide a new entry to the development of half-sandwich iridium-based anticancer drugs.

Cisplatin-mediated activation of glucocorticoid receptor induces platinum resistance via MAST1

Agonists of glucocorticoid receptor (GR) are frequently given to cancer patients with platinum-containing chemotherapy to reduce inflammation, but how GR influences tumor growth in response to platinum-based chemotherapy such as cisplatin through inflammation-independent signaling remains largely unclear. Combined genomics and transcription factor profiling reveal that MAST1, a critical platinum resistance factor that reprograms the MAPK pathway, is upregulated upon cisplatin exposure through activated transcription factor GR. Mechanistically, cisplatin binds to C622 in GR and recruits GR to the nucleus for its activation, which induces MAST1 expression and consequently reactivates MEK signaling. GR nuclear translocation and MAST1 upregulation coordinately occur in patient tumors collected after platinum treatment, and align with patient treatment resistance. Co-treatment with dexamethasone and cisplatin restores cisplatin-resistant tumor growth, whereas addition of the MAST1 inhibitor lestaurtinib abrogates tumor growth while preserving the inhibitory effect of dexamethasone on inflammation in vivo. These findings not only provide insights into the underlying mechanism of GR in cisplatin resistance but also offer an effective alternative therapeutic strategy to improve the clinical outcome of patients receiving platinum-based chemotherapy with GR agonists.

Critical factors affecting the albumin binding of half-sandwich Ru(ii) and Rh(iii) complexes of 8-hydroxyquinolines and oligopyridines

There is significant interest today in the interaction of half-sandwich anticancer organometallic complexes with proteins. It is considered as a crucial factor in the transport and mode of action of these compounds; thus it can affect their overall pharmacological and toxicological profiles. Albumin binding of high stability Ru(ii)(η⁶-p-cymene) and Rh(iii)(η⁵-C₅Me₅) complexes formed with 8-hydroxyquinoline, its 5-chloro-7-((proline-1-yl)methyl) substituted derivative, 2,2'-bipyridine and 1,10-phenanthroline is discussed herein. The interaction with human serum albumin in terms of kinetic aspects, binding strength and possible binding sites was studied in detail by means of various methods such as ¹H NMR spectroscopy, UV-visible spectrophotometry, steady-state and time-resolved fluorometry, ultrafiltration and capillary zone electrophoresis. Ru(ii)(η⁶-p-cymene)(2,2'-bipyridine) and Ru(ii)(η⁶-p-cymene)(1,10-phenanthroline) complexes do not bind to the protein measurably, most probably due to kinetic reasons. However, other complexes bind significantly to albumin with fairly different kinetics to albumin. The binding affinity towards hydrophobic binding pockets shows correlation with lipophilicity along with the actual charge of the respective complexes. The studied complexes preserve their original structure upon interaction with albumin. Formation constants computed for the binding of these metal complexes to histidine-containing model oligopeptides demonstrated significant ternary complex formation, pointing out the importance of histidine coordination in the binding of these types of complexes.

Redox modulation of vitagenes via plant polyphenols and vitamin D: Novel insights for chemoprevention and therapeutic interventions based on organoid technology

Polyphenols are chemopreventive through the induction of nuclear factor erythroid 2 related factor 2 (Nrf2)-mediated proteins and anti-inflammatory pathways. These pathways, encoding cytoprotective vitagenes, include heat shock proteins, such as heat shock protein 70 (Hsp70) and heme oxygenase-1 (HO-1), as well as glutathione redox system to protect against cancer initiation and progression. Phytochemicals exhibit biphasic dose responses on cancer cells, activating at low dose, signaling pathways resulting in upregulation of vitagenes, as in the case of the Nrf2 pathway upregulated by hydroxytyrosol (HT) or curcumin and NAD/NADH-sirtuin-1 activated by resveratrol. Here, the importance of vitagenes in redox stress response and autophagy mechanisms, as well as the potential use of dietary antioxidants in the prevention and treatment of multiple types of cancer are discussed. We also discuss the possible relationship between SARS-CoV-2, inflammation and cancer, exploiting innovative therapeutic approaches with HT-rich aqueous olive pulp extract (Hidrox®), a natural polyphenolic formulation, as well as the rationale of Vitamin D supplementation. Finally, we describe innovative approaches with organoids technology to study human carcinogenesis in preclinical models from basic cancer research to clinical practice, suggesting patient-derived organoids as an innovative tool to test drug toxicity and drive personalized therapy.

BODIPY-Appended Pt(II) Complexes with High Toxicities and Anti-chemoresistance Performances in a Cisplatin Resistant In Vivo Model

Two novel fluorophore (BODIPY)-bearing complexes, pyriplatin (mCBP) and pyrimidine-chelated cisplatin (dCBP), were synthesized and characterized. The additional BODIPY-pyridine/pyridimine motifs of the two Pt(II) complexes resulted in stronger interactions with DNA in comparison with those of cisplatin. mCBP and cisplatin caused relative decreases in life span and body length in a cisplatin resistant in vivo model, N2 (wild-type) Caenorhabditis elegans. In contrast, dCBP resulted in a dramatic reduction in the two physiological parameters in N2 C. elegans, indicating high toxicity and sensitivity. The resistance factors (RF) of cisplatin, mCBP, and dCBP were determined to be 2.46, 1.04, and 0.91, respectively. The increasing RF folds for mCBP and dCBP against cisplatin were 2.36 and 2.70, respectively. This suggested they were featured with improved anti-chemoresistance capabilities. It is noteworthy that dCBP showed lowest lethal concentration (LC₅₀) values of 0.56 and 0.61 mM in cisplatin resistant and sensitive in vivo models, respectively. Upregulation of several evolutionary conservation genes that regulate cisplatin chemoresistance through cisplatin effluxing, the DNA damage response, the unfolded protein response, and detoxification (asna-1, parp-1, enpl-1, and skn-1) was observed upon exposure to cisplatin but not to mCBP and dCBP. This could explain the improved anti-chemoresistance performances of synthesized Pt(II) complexes.

Cisplatin alkylating activity in zebrafish causes resistance to chorionic degradation and inhibition of osteogenesis

Zebrafish have gained popularity as a model organism due to their rapid, external, and transparent development, high fecundity, and gene homology with higher vertebrate models and humans. Specifically, drug discovery has had high success in the implementation of zebrafish in studies for target discovery, efficacy, and toxicity. However, a major limitation of the zebrafish model is a dependence on waterborne exposure in order to maintain high throughput capabilities. Dose delivery can be impeded by a matrix of N-linked glycoproteins and other polypeptides called the chorion. This acelluar barrier is protective of the developing embryo, and thus new approaches for assessment have involved their removal. In these studies, we explored the chorionic interference of a well-characterized alkylating chemotherapeutic, cisplatin, known to accumulate in the chorion of zebrafish and cause delayed hatching. Our results indicated that increased exposure of cisplatin due to dechorionation did not alter morphological endpoints, although retained confinement reduced total body length and yolk utilization. Additionally, inhibition of osteogenesis visualized with Alizarian Red staining, was observable in dechorionated and non-dechorionated treatment groups. The chorions of cisplatin-treated embryos showed resistance to degradation unless treated with a pronase solution. This may be may be due to cisplatin covalently crosslinking which reinforces the structure. As such, the chorion may play an advantageous role in studies to determine alkylating activity of novel compounds. Furthermore, the expression of zebrafish hatching enzyme was not affected by cisplatin exposure. These studies demonstrate that not only was recapitulation of mechanistic activity supported in zebrafish, but highly relevant off-target toxicities observed in higher vertebrates were identified in zebrafish, regardless of chorionation. Experimental design in drug discovery should consider preliminary studies without dechorionation in order to determine dose impediment or off-target adducting.

Direct Binding of Cisplatin to p22phox, an Endoplasmic Reticulum (ER) Membrane Protein, Contributes to Cisplatin Resistance in Oral Squamous Cell Carcinoma (OSCC) Cells

Prolonged treatment with cisplatin (CDDP) frequently develops chemoresistance. We have previously shown that p22phox, an endoplasmic reticulum (ER) membrane protein, confers CDDP resistance by blocking CDDP nuclear entry in oral squamous cell carcinoma (OSCC) cells; however, the underlying mechanism remains unresolved. Using a fluorescent dye-labeled CDDP, here we show that CDDP can bind to p22phox in both cell-based and cell-free contexts. Subsequent detection of CDDP-peptide interaction by the Tris-Tricine-based electrophoresis revealed that GA-30, a synthetic peptide matching a region of the cytosolic domain of p22phox, could interact with CDDP. These results were further confirmed by liquid chromatography–mass spectrometry (LC–MS) analysis, from which MA-11, an 11-amino acid subdomain of the GA-30 domain, could largely account for the interaction. Amino acid substitutions at Cys50, Met65 and Met73, but not His72, significantly impaired the binding between CDDP and the GA-30 domain, thereby suggesting the potential CDDP-binding residues in p22phox protein. Consistently, the p22phox point mutations at Cys50, Met65 and Met73, but not His72, resensitized OSCC cells to CDDP-induced cytotoxicity and apoptosis. Finally, p22phox might have binding specificity for the platinum drugs, including CDDP, carboplatin and oxaliplatin. Together, we have not only identified p22phox as a novel CDDP-binding protein, but further highlighted the importance of such a drug-protein interaction in drug resistance.