Improving anticancer activity towards colon cancer cells with a new p53-activating agent

A first-in-class inhibitor of homologous recombination DNA repair counteracts tumour growth, metastasis and therapeutic resistance in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is among the cancer types with poorest prognosis and survival rates primarily due to resistance to standard-of-care therapies, including gemcitabine (GEM) and olaparib. Particularly, wild-type (wt)BRCA tumours, the most prevalent in PDAC, are more resistant to DNA-targeting agents like olaparib, restraining their clinical application. Recently, we disclosed a monoterpene indole alkaloid derivative (BBIT20) as a new inhibitor of homologous recombination (HR) DNA repair with anticancer activity in breast and ovarian cancer. Since inhibition of DNA repair enhances the sensitivity of cancer cells to chemotherapy, we aimed to investigate the anticancer potential of BBIT20 against PDAC, particularly carrying wtBRCA.

METHODS

In vitro and in vivo PDAC models, particularly human cell lines (including GEM-resistant PDAC cells), patient-derived organoids and xenograft mice of PDAC were used to evaluate the anticancer potential of BBIT20, alone and in combination with GEM or olaparib. Disruption of the BRCA1-BARD1 interaction by BBIT20 was assessed by co-immunoprecipitation, immunofluorescence and yeast two-hybrid assay.

RESULTS

The potent antiproliferative activity of BBIT20, superior to olaparib, was demonstrated in PDAC cells regardless of BRCA status, by inducing cell cycle arrest, apoptosis, and DNA damage, while downregulating HR. The disruption of DNA double-strand breaks repair by BBIT20 was further reinforced by non-homologous end joining (NHEJ) suppression. The inhibition of BRCA1-BARD1 heterodimer by BBIT20 was demonstrated in PDAC cells and confirmed in a yeast two-hybrid assay. In GEM-resistant PDAC cells, BBIT20 showed potent antiproliferative, anti-migratory and anti-invasive activity, overcoming GEM resistance by inhibiting the multidrug resistance P-glycoprotein, upregulating the intracellular GEM-transporter ENT1, and downregulating GEM resistance-related microRNA-20a and GEM metabolism enzymes as RRM1/2. Furthermore, BBIT20 did not induce resistance in PDAC cells. It inhibited the growth of patient-derived PDAC organoids, by inducing apoptosis, repressing HR, and potentiating olaparib and GEM cytotoxicity. The enhancement of olaparib antitumor activity by BBIT20 was confirmed in xenograft mice of PDAC. Notably, it hindered tumour growth and liver metastasis formation, improving survival of orthotopic xenograft mice of PDAC. Furthermore, its potential as a stroma-targeting agent, reducing fibrotic extracellular matrix and overcoming desmoplasia, associated with an enhancement of immune cell response by depleting PD-L1 expression in tumour tissues, renders BBIT20 even more appealing for combination therapy, particularly with immunotherapy.

CONCLUSION

These findings underscore the great potential of BBIT20 as a novel multifaceted anticancer drug candidate for PDAC treatment.

Cellular, Structural Basis, and Recent Progress for Targeting Murine Double Minute X (MDMX) in Tumors

Murine double minute X (MDMX) is an oncoprotein that mainly has a negative regulatory effect on the tumor suppressor p53 to induce tumorigenesis. As MDMX is highly expressed in various types of tumor cells, targeting and inhibiting MDMX are becoming a promising strategy for treating cancers. However, the high degree of structural homology between MDMX and its homologous protein murine double minute 2 (MDM2) is a great challenge for the development of MDMX-targeted therapies. This review introduces the structure, distribution, and regulation of the MDMX, summarizes the structural features and structure-activity relationships (SARs) of MDMX ligands, and focuses on the differences between MDMX and MDM2 in these aspects. Our purpose of this work is to propose potential strategies to achieve the specific targeting of MDMX.

Development and Nanoparticle-Mediated Delivery of Novel MDM2/MDM4 Heterodimer Peptide Inhibitors to Enhance 5-Fluorouracil Nucleolar Stress in Colorectal Cancer Cells

Colorectal cancer (CRC) often involves wild-type p53 inactivation by MDM2 and MDM4 overexpression, promoting tumor progression and resistance to 5-fluoruracil (5-FU). Disrupting the MDM2/4 heterodimer can proficiently reactivate p53, sensitizing cancer cells to 5-FU. Herein, we developed 16 peptides based on Pep3 (1), the only known peptide acting through this mechanism. The new peptides, notably 3 and 9, showed lower IC50 values than 1. When incorporated into tumor-targeted biodegradable nanoparticles, these exhibited cytotoxicity against three different CRC cell lines. Notably, NPs/9 caused a significant increase in p53 levels associated with a strong increment of its main downstream target p21 inducing apoptosis. Also, the combined treatment of 9 with 5-FU caused the activation of nucleolar stress and a synergic apoptotic effect. Hence, the co-delivery of MDM2/4 heterodimer disruptors with 5-FU through nanoparticles might be a promising strategy to overcome drug resistance in CRC.

Structure-Activity Relationship Studies of Chalcones and Diarylpentanoids with Antitumor Activity: Potency and Selectivity Optimization

We previously reported that chalcone CM-M345 (1) and diarylpentanoid BP-C4 (2) induced p53-dependent growth inhibitory activity in human cancer cells. Herein, CM-M345 (1) and BP-C4 (2) analogues were designed and synthesized in order to obtain more potent and selective compounds. Compounds 16, 17, 19, 20, and 22-24 caused pronounced in vitro growth inhibitory activity in HCT116 cells (0.09 < GI50 < 3.10 μM). Chemical optimization of CM-M345 (1) led to the identification of compound 36 with increased selectivity for HCT116 cells expressing wild-type p53 compared to its p53-null isogenic derivative and low toxicity to non-tumor HFF-1 cells. The molecular modification of BP-C4 (2) resulted in the discovery of compound 16 with more pronounced antiproliferative activity and being selective for HCT116 cells with p53, as well as 17 with enhanced antiproliferative activity against HCT116 cells and low toxicity to non-tumor cells. Compound 16 behaved as an inhibitor of p53-MDM2 interaction, and compound 17 was shown to induce apoptosis, associated with an increase in cleaved PARP and decreased levels of the anti-apoptotic protein Bcl-2. In silico studies allowed us to predict the druglikeness and ADMET properties for 16 and 17. Docking and molecular dynamics studies predicted that 16 could bind stably to the MDM2 binding pocket.

Counteracting Colon Cancer by Inhibiting Mitochondrial Respiration and Glycolysis with a Selective PKCδ Activator

Metabolic reprogramming is a central hub in tumor development and progression. Therefore, several efforts have been developed to find improved therapeutic approaches targeting cancer cell metabolism. Recently, we identified the 7α-acetoxy-6β-benzoyloxy-12-O-benzoylroyleanone (Roy-Bz) as a PKCδ-selective activator with potent anti-proliferative activity in colon cancer by stimulating a PKCδ-dependent mitochondrial apoptotic pathway. Herein, we investigated whether the antitumor activity of Roy-Bz, in colon cancer, could be related to glucose metabolism interference. The results showed that Roy-Bz decreased the mitochondrial respiration in human colon HCT116 cancer cells, by reducing electron transfer chain complexes I/III. Consistently, this effect was associated with downregulation of the mitochondrial markers cytochrome c oxidase subunit 4 (COX4), voltage-dependent anion channel (VDAC) and mitochondrial import receptor subunit TOM20 homolog (TOM20), and upregulation of synthesis of cytochrome c oxidase 2 (SCO2). Roy-Bz also dropped glycolysis, decreasing the expression of critical glycolytic markers directly implicated in glucose metabolism such as glucose transporter 1 (GLUT1), hexokinase 2 (HK2) and monocarboxylate transporter 4 (MCT4), and increasing TP53-induced glycolysis and apoptosis regulator (TIGAR) protein levels. These results were further corroborated in tumor xenografts of colon cancer. Altogether, using a PKCδ-selective activator, this work evidenced a potential dual role of PKCδ in tumor cell metabolism, resulting from the inhibition of both mitochondrial respiration and glycolysis. Additionally, it reinforces the antitumor therapeutic potential of Roy-Bz in colon cancer by targeting glucose metabolism.

Investigation of Three Morchella Species for Anticancer Activity Against Colon Cancer Cell Lines by UPLC-MS-Based Chemical Analysis

In search of new anticancer agents, natural products including fungal compounds had been used as potential anticancer agents. The aim of this study was to investigate the anticancer activity of Morchella extracts against colon cancer cell line and UPLC-DAD-MS/MS analysis for the identification of compounds. The cytotoxic activity of the three Morchella species was examined for their anti-carcinogenic properties against the colon cancer cell lines. Phytochemical analyses were performed to screen Morchella for the presence of anti-cancerous compounds. All the fungal extracts inhibited the viability of colon cancer cells in a dose-dependent manner. Major compounds identified in Morchella included amino acid, fatty acid, sterol, flavonoid, peptide, glutamic acid, alkaloid, terpenoid, cyclopyrrolones, and coumarin. Several new compounds were detected among all the three Morchella extracts. In conclusion, all the fungal extracts showed potential inhibition of colon cancer cells and actively arrested the cell viability. It was concluded that the identified bioactive compounds might be the main constituents contributing to the anticancer activity of Morchella against human colon cancer cell lines. Thus, Morchella extracts are a potential source of bioactive compounds with cytotoxicity and could potentially be used as functional food supplements. Due to the nature of impressive findings, this investigation should be undertaken further to allow the studies to explore and develop a potential cytotoxic agents against colon cancer.

Supercritical fluid extract of Angelica sinensis promotes the anti-colorectal cancer effect of oxaliplatin

Oxaliplatin-based chemotherapy regimens are recommended for patients with advanced colorectal cancer (CRC). However, oxaliplatin (OXA) can cause toxic side effects at the recommended dosage. Therefore, it is necessary to find new drug candidates that can synergize with OXA and thereby lower the OXA dose while still maintaining its efficacy. Angelica sinensis is a common drug in traditional Chinese medicine and has demonstrated a significant anti-CRC effect in modern pharmacological studies. The active ingredients in Angelica sinensis can be effectively extracted by a supercritical fluid extract. In this study, the supercritical fluid extract of Angelica sinensis (A-SFE) was obtained by a stable extraction process and was chemically characterized by GC/MS. The anti-cancer effect of A-SFE when applied individually was explored in vitro through MTT, scratch, and Transwell assay. The effect of A-SFE on CRC cells under the influence of tumor-associated macrophages (TAMs) was explored by a co-culture model. The results showed that A-SFE could inhibit the viability, metastasis, and invasion of HCT116 cells, especially under the influence of TAMs. When 20-100 μg/ml of A-SFE and 8-64 μg/ml of OXA were used in combination in HCT116 cells, synergistic or additive effects were shown in different concentration combinations. The CT26 syngeneic mouse model was used to explore the anti-CRC effect of OXA combined with A-SFE in vivo. The tumor volume, expression levels of Ki67, MMP9, and CD206 in the OXA + A-SFE group were less than those in the OXA group. In conclusion, A-SFE has the potential to become an adjuvant drug for OXA in the treatment of CRC, which provides new strategies for anti-colorectal cancer research.

Amaryllidaceae-Type Alkaloids from Pancratium maritimum: Apoptosis-Inducing Effect and Cell Cycle Arrest on Triple-Negative Breast Cancer Cells

Aiming to find Amaryllidaceae alkaloids against breast cancer, including the highly aggressive triple-negative breast cancer, the phytochemical study of Pancratium maritimum was carried out. Several Amaryllidaceae-type alkaloids, bearing scaffolds of the haemanthamine-, homolycorine-, lycorine-, galanthamine-, and tazettine-type were isolated (3–11), along with one alkamide (2) and a phenolic compound (1). The antiproliferative effect of compounds (1–11) was evaluated by the sulforhodamine B assay against triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468, breast cancer cells MCF-7, and the non-malignant fibroblast (HFF-1) and breast (MCF12A) cell lines. The alkaloids 3, 5, 7, and 11 showed significant growth inhibitory effects against all breast cancer cell lines, with IC₅₀ (half-maximal inhibitory concentration) values ranging from 0.73 to 16.3 µM. The homolycorine-type alkaloid 7 was selected for further investigation in MDA-MB-231 cells. In the annexin-V assay, compound 7 increased cell death by apoptosis, which was substantiated, in western blot analyses, by the increased expression of the pro-apoptotic protein Bax, and the decreased expression of the anti-apoptotic protein Bcl-xL. Consistently, it further stimulated mitochondrial reactive oxygen species (ROS) generation. The antiproliferative effect of compound 7 was also associated with G2/M cell cycle arrest, which was supported by an increase in the p21 protein expression levels. In MDA-MB-231 cells, compound 7 also exhibited synergistic effects with conventional chemotherapeutic drugs such as etoposide.

Natural Small Molecules Enabled Efficient Immunotherapy through Supramolecular Self-Assembly in P53-Mutated Colorectal Cancer

Nanomedicine, constructed from therapeutics, presents an advantage in drug delivery for cancer therapies. However, nanocarrier-based treatment systems have problems such as interbatch variability, multicomponent complexity, poor drug delivery, and carrier-related toxicity. To solve these issues, the natural molecule honokiol (HK), an anticancer agent in a phase I clinical trial (CTR20170822), was used to form a self-assembly nanoparticle (SA) through hydrogen bonding and hydrophobicity. The preparation of SA needs no molecular precursors or excipients in aqueous solution, and 100% drug-loaded SA exhibited superior tumor-targeting ability due to the enhanced permeability and retention (EPR) effect. Moreover, SA significantly enhanced the antitumor immunity relative to free HK, and the mechanism has notable selectivity to the p53 pathway. Furthermore, SA exhibited excellent physiological stability and inappreciable toxicity. Taken together, this supramolecular self-assembly strategy provides a safe and "molecular economy" model for rational design of clinical therapies and is expected to promote targeted therapy of HK, especially in colorectal cancer patients with obvious p53 status.

BP-M345, a New Diarylpentanoid with Promising Antimitotic Activity

Previously, we reported the in vitro growth inhibitory effect of diarylpentanoid BP-M345 on human cancer cells. Nevertheless, at that time, the cellular mechanism through which BP-M345 exerts its growth inhibitory effect remained to be explored. In the present work, we report its mechanism of action on cancer cells. The compound exhibits a potent tumor growth inhibitory activity with high selectivity index. Mechanistically, it induces perturbation of the spindles through microtubule instability. As a consequence, treated cells exhibit irreversible defects in chromosome congression during mitosis, which induce a prolonged spindle assembly checkpoint-dependent mitotic arrest, followed by massive apoptosis, as revealed by live cell imaging. Collectively, the results indicate that the diarylpentanoid BP-M345 exerts its antiproliferative activity by inhibiting mitosis through microtubule perturbation and causing cancer cell death, thereby highlighting its potential as antitumor agent.

A Diarylpentanoid with Potential Activation of the p53 Pathway: Combination of in silico Screening Studies, Synthesis, and Biological Activity Evaluation

In silico studies of a library of diarylpentanoids led us to the identification of potential new MDM2/X ligands. The diarylpentanoids with the best docking scores obeying the druglikeness and ADMET prediction properties were subsequently synthesized and evaluated for their antiproliferative activity on colon cancer HCT116 and fibroblasts HFF-1 cells. The effect on p53-MDM2/X interactions was evaluated through yeast-based assays for compounds showing potent antiproliferative activity in HCT116 cells and low toxicity in normal cells, resulting in the identification of a potential dual inhibitor. Moreover, its antiproliferative effect was significantly reduced in the absence of p53 and in MDA-MB-231 cells expressing a mutant p53 form. The antiproliferative effect of this compound was associated with induction of cell cycle arrest, apoptosis, PARP cleavage and increased p53 and its transcriptional targets, p21 and PUMA, in HCT116 cells. Docking poses and residues involved in the inhibition of p53-MDM2/X interactions were predicted by docking studies.

BBIT20 inhibits homologous DNA repair with disruption of the BRCA1-BARD1 interaction in breast and ovarian cancer

BACKGROUND AND PURPOSE

Advances in the treatment of triple-negative breast and ovarian cancer remain challenging. In particular, resistance to the available therapy, by restoring or overexpressing the DNA repair machinery, has often been reported. New strategies to improve the therapeutic outcomes of these cancers are needed. Herein, we disclose the dregamine 5-bromo-pyridin-2-ylhydrazone (BBIT20), a natural monoterpene indole alkaloid derivative, as an inhibitor of homologous DNA repair.

EXPERIMENTAL APPROACH

To unveil BBIT20 antitumour activity and underlying molecular mechanism of action, two-dimensional (2D) and three-dimensional (3D) cell cultures, patient-derived cell lines and xenograft mouse models were used.

KEY RESULTS

BBIT20 disrupted the BRCA1-BARD1 interaction, triggering nuclear-to-cytoplasmic BRCA1 translocation, cell cycle arrest and downregulation of homologous DNA repair-related genes and proteins, with subsequent enhancement of DNA damage, reactive oxygen species generation and apoptosis, in triple-negative breast and ovarian cancer cells. BBIT20 also displayed pronounced antitumour activity in patient-derived cells and xenograft mouse models of ovarian cancer, with low toxicity in non-malignant cells and undetectable side effects in mice. Additionally, it did not induce resistance in triple-negative breast and ovarian cancer and displayed marked synergistic effects with cisplatin and olaparib (a poly [ADP-ribose] polymerase inhibitor), on 2D and 3D models of these cancer cells.

CONCLUSION AND IMPLICATIONS

These findings add an inhibitor of the BRCA1-BARD1 interaction to the list of DNA-damaging agents. Importantly, either as a single agent or in combination therapy, BBIT20 reveals great potential in the personalized treatment of aggressive and resistant cancers, particularly triple-negative breast and advanced ovarian cancer.

Platinum Complexes in Colorectal Cancer and Other Solid Tumors

Simple Summary

Cisplatin is successfully used for the treatment of various solid cancers. Unfortunately, it shows no activity in colorectal cancer. The resistance phenotype of colorectal cancer cells is mainly caused by alterations in p53-controlled DNA damage signaling and/or defects in the cellular mismatch repair pathway. Improvement of platinum-based chemotherapy in cisplatin-unresponsive cancers, such as colorectal cancer, might be achieved by newly designed cisplatin analogues, which retain activity in unresponsive tumor cells. Moreover, a combination of cisplatin with biochemical modulators of DNA damage signaling might sensitize cisplatin-resistant tumor cells to the drug, thus providing another strategy to improve cancer therapy.

Abstract

Cisplatin is one of the most commonly used drugs for the treatment of various solid neoplasms, including testicular, lung, ovarian, head and neck, and bladder cancers. Unfortunately, the therapeutic efficacy of cisplatin against colorectal cancer is poor. Various mechanisms appear to contribute to cisplatin resistance in cancer cells, including reduced drug accumulation, enhanced drug detoxification, modulation of DNA repair mechanisms, and finally alterations in cisplatin DNA damage signaling preventing apoptosis in cancer cells. Regarding colorectal cancer, defects in mismatch repair and altered p53-mediated DNA damage signaling are the main factors controlling the resistance phenotype. In particular, p53 inactivation appears to be associated with chemoresistance and poor prognosis. To overcome resistance in cancers, several strategies can be envisaged. Improved cisplatin analogues, which retain activity in resistant cancer, might be applied. Targeting p53-mediated DNA damage signaling provides another therapeutic strategy to circumvent cisplatin resistance. This review provides an overview on the DNA repair pathways involved in the processing of cisplatin damage and will describe signal transduction from cisplatin DNA lesions, with special attention given to colorectal cancer cells. Furthermore, examples for improved platinum compounds and biochemical modulators of cisplatin DNA damage signaling will be presented in the context of colon cancer therapy.

A selective p53 activator and anticancer agent to improve colorectal cancer therapy

Impairment of the p53 pathway is a critical event in cancer. Therefore, reestablishing p53 activity has become one of the most appealing anticancer therapeutic strategies. Here, we disclose the p53-activating anticancer drug (3S)-6,7-bis(hydroxymethyl)-5-methyl-3-phenyl-1H,3H-pyrrolo[1,2-c]thiazole (MANIO). MANIO demonstrates a notable selectivity to the p53 pathway, activating wild-type (WT)p53 and restoring WT-like function to mutant (mut)p53 in human cancer cells. MANIO directly binds to the WT/mutp53 DNA-binding domain, enhancing the protein thermal stability, DNA-binding ability, and transcriptional activity. The high efficacy of MANIO as an anticancer agent toward cancers harboring WT/mutp53 is further demonstrated in patient-derived cells and xenograft mouse models of colorectal cancer (CRC), with no signs of undesirable side effects. MANIO synergizes with conventional chemotherapeutic drugs, and in vitro and in vivo studies predict its adequate drug-likeness and pharmacokinetic properties for a clinical candidate. As a single agent or in combination, MANIO will advance anticancer-targeted therapy, particularly benefiting CRC patients harboring distinct p53 status.

Tryptophanol-Derived Oxazolopyrrolidone Lactams as Potential Anticancer Agents against Gastric Adenocarcinoma

Gastric cancer is one of the deadliest cancers in modern societies, so there is a high level of interest in discovering new drugs for this malignancy. Previously, we demonstrated the ability of tryptophanol-derived polycyclic compounds to activate the tumor suppressor protein p53, a relevant therapeutic target in cancer. In this work, we developed a novel series of enantiomerically pure tryptophanol-derived small molecules to target human gastric adenocarcinoma (AGS) cells. From an initial screening of fourteen compounds in AGS cell line, a hit compound was selected for optimization, leading to two derivatives selective for AGS gastric cells over other types of cancer cells (MDA-MB-231, A-549, DU-145, and MG-63). More importantly, the compounds were non-toxic in normal cells (HEK 293T). Additionally, we show that the growth inhibition of AGS cells induced by these compounds is mediated by apoptosis. Stability studies in human plasma and human liver microsomes indicate that the compounds are stable, and that the major metabolic transformations of these molecules are mono- and di-hydroxylation of the indole ring.

Antimicrobial Peptides as New Combination Agents in Cancer Therapeutics: A Promising Protocol against HT-29 Tumoral Spheroids

Antimicrobial peptides are molecules synthetized by a large variety of organisms as an innate defense against pathogens. These natural compounds have been identified as promising alternatives to widely used molecules to treat infections and cancer cells. Antimicrobial peptides could be viewed as future chemotherapeutic alternatives, having the advantage of low propensity to drug resistance. In this study, we evaluated the efficiency of the antimicrobial peptide gramicidin A (GA) and the anticancer drug, doxorubicin (Doxo) against the spheroids from colorectal cancer cells (HT-29). The two drugs were applied separately against HT-29 spheroids as well as together to determine if they can act synergistically. The spheroid evolution, cell viability, and ATP levels were monitored at 24 and 48 h after the applied treatments. The results show significant drops in cell viability and cellular ATP levels for all the experimental treatments. The simultaneous use of the two compounds (GA and Doxo) seems to cause a synergistic effect against the spheroids.

SLMP53-2 Restores Wild-Type-Like Function to Mutant p53 through Hsp70: Promising Activity in Hepatocellular Carcinoma

Half of human cancers harbor TP53 mutations that render p53 inactive as a tumor suppressor. In these cancers, reactivation of mutant p53 (mutp53) through restoration of wild-type-like function constitutes a valuable anticancer therapeutic strategy. In order to search for mutp53 reactivators, a small library of tryptophanol-derived oxazoloisoindolinones was synthesized and the potential of these compounds as mutp53 reactivators and anticancer agents was investigated in human tumor cells and xenograft mouse models. By analysis of their anti-proliferative effect on a panel of p53-null NCI-H1299 tumor cells ectopically expressing highly prevalent mutp53, the compound SLMP53-2 was selected based on its potential reactivation of multiple structural mutp53. In mutp53-Y220C-expressing hepatocellular carcinoma (HCC) cells, SLMP53-2-induced growth inhibition was mediated by cell cycle arrest, apoptosis, and endoplasmic reticulum stress response. In these cells, SLMP53-2 restored wild-type-like conformation and DNA-binding ability of mutp53-Y220C by enhancing its interaction with the heat shock protein 70 (Hsp70), leading to the reestablishment of p53 transcriptional activity. Additionally, SLMP53-2 displayed synergistic effect with sorafenib, the only approved therapy for advanced HCC. Notably, it exhibited potent antitumor activity in human HCC xenograft mouse models with a favorable toxicological profile. Collectively, SLMP53-2 is a new mutp53-targeting agent with promising antitumor activity, particularly against HCC.

New inhibitor of the TAp73 interaction with MDM2 and mutant p53 with promising antitumor activity against neuroblastoma

TAp73 is a key tumor suppressor protein, regulating the transcription of unique and shared p53 target genes with crucial roles in tumorigenesis and therapeutic response. As such, in tumors with impaired p53 signaling, like neuroblastoma, TAp73 activation represents an encouraging strategy, alternative to p53 activation, to suppress tumor growth and chemoresistance. In this work, we report a new TAp73-activating agent, the 1-carbaldehyde-3,4-dimethoxyxanthone (LEM2), with potent antitumor activity. Notably, LEM2 was able to release TAp73 from its interaction with both MDM2 and mutant p53, enhancing TAp73 transcriptional activity, cell cycle arrest, and apoptosis in p53-null and mutant p53-expressing tumor cells. Importantly, LEM2 displayed potent antitumor activity against patient-derived neuroblastoma cells, consistent with an activation of the TAp73 pathway. Additionally, potent synergistic effects were obtained for the combination of LEM2 with doxorubicin and cisplatin in patient-derived neuroblastoma cells. Collectively, besides its relevant contribution to the advance of TAp73 pharmacology, LEM2 may pave the way to improved therapeutic alternatives against neuroblastoma.

Naphthoylhydrazones: coordination to metal ions and biological screening

V^IVO, Cu^II and Zn^II complexes from three new naphthoylhydrazones were screened towards their ability to bind albumin and their cytotoxicity.

Improving anticancer activity towards colon cancer cells with a new p53-activating agent

BACKGROUND AND PURPOSE

Impairment of the tumour suppressor p53 pathway is a major event in human cancers, making p53 activation one of the most attractive therapeutic strategies to halt cancer. Here, we have identified a new selective p53 activator and investigated its potential as an anticancer agent.

EXPERIMENTAL APPROACH

Anti-proliferative activity of the (R)-tryptophanol-derived bicyclic lactam SYNAP was evaluated in a range of human cancer cells with different p53 status. The anticancer activity and mechanism of action of SYNAP was studied in two- and three-dimensional models of human colon adenocarcinoma HCT116 cells with wild-type p53 and corresponding p53-null isogenic derivative cells, alone and in combination with known chemotherapeutic agents.

KEY RESULTS

SYNAP showed anti-proliferative effect in human cancer cells dependent on p53 status. In HCT116 cells, SYNAP caused p53-dependent growth inhibition, associated with cell cycle arrest and apoptosis, anti-migratory activity and regulation of the expression of p53 transcriptional targets. Data also indicated that SYNAP targeted p53, inhibiting its interaction with its endogenous inhibitors, murine double minute (MDM)2 and MDMX. Moreover, SYNAP sensitized colon cancer cells to the cytotoxic effect of known chemotherapeutic agents. SYNAP did not induce acquired or cross-resistance and re-sensitized doxorubicin-resistant colon cancer cells to chemotherapy. Additionally, SYNAP was non-genotoxic and had low cytotoxicity against normal cells.

CONCLUSION AND IMPLICATIONS

SYNAP revealed encouraging anticancer activity, either alone or in combination with known chemotherapeutic agents, in colon cancer cells. Apart from its promising application in cancer therapy, SYNAP may provide a starting point for improved p53 activators.