Reactivation of TAp73 tumor suppressor by protoporphyrin IX, a metabolite of aminolevulinic acid, induces apoptosis in TP53-deficient cancer cells

Pharmaceutical Nanoplatforms Based on Self-nanoemulsifying Drug Delivery Systems for Optimal Transport and Co-delivery of siRNAs and Anticancer Drugs

Small interfering RNAs (siRNAs) have the ability to induce selective gene silencing, although siRNAs are vulnerable to degradation in vivo. Various active pharmaceutical ingredients (APIs) are currently used as effective therapeutics in the treatment of cancer. However, routes of administration are limited due to their physicochemical and biopharmaceutical properties. This research aimed to develop oral pharmaceutical formulations based on self-nanoemulsifying drug delivery systems (SNEDDS) for optimal transport and co-delivery of siRNAs related to cancer and APIs. Formulations were developed using optimal mixing design (Design-Expert 11 software) for SNEDDS loading with siRNA (water/oil emulsion), API (oil/water emulsion), and siRNA-API (multiphase water/oil/water emulsion). The final formulations were characterized physicochemically and biologically. The nanosystems less than 50 nm in size had a drug loading above 48 %. The highest drug release occurred at intestinal pH, allowing drug protection in physiological fluids. SNEDDS-siRNA-APIs showed a twofold toxicity effect than APIs in solution and higher transfection and internalization of siRNA in cancer cells with respect to free siRNAs. In the duodenum, higher permeability was observed with SNEDDS-API than with the API solution, as determined by ex-vivo fluorescence microscopy. The multifunctional formulation based on SNEDDS was successfully prepared, siRNA, hydrophobic chemotherapeutics (doxorubicin, valrubicin and methotrexate) and photosensitizers (rhodamine b and protoporphyrin IX) agents were loaded, using a chitosan-RNA core, and Labrafil® M 1944 CS, Cremophor® RH40, phosphatidylcholine shell, forming stable hybrid SNEDDS as multiphasic emulsion, suitable as co-delivery system with a potent anticancer activity.

The in vitro anti-cancer synergy of neurokinin-1 receptor antagonist, aprepitant, and 5-aminolevulinic acid in glioblastoma

Glioblastoma multiforme (GBM) is the most malignant type of cerebral neoplasm in adults with a poor prognosis. Currently, combination therapy with different anti-cancer agents is at the forefront of GBM research. Hence, this study aims to evaluate the potential anti-cancer synergy of a clinically approved neurokinin-1 receptor antagonist, aprepitant, and 5-aminolevulinic acid (5-ALA), a prodrug that elicits fluorescent porphyrins in gliomas on U-87 human GBM cells. We found that aprepitant and 5-ALA effectively inhibited GBM cell viability. The combinatorial treatment of these drugs exerted potent synergistic growth inhibitory effects on GBM cells. Moreover, aprepitant and 5-ALA induced apoptosis and altered the levels of apoptotic genes (up-regulation of Bax and P53 along with downregulation of Bcl-2). Furthermore, aprepitant and 5-ALA increased the accumulation of protoporphyrin IX, a highly pro-apoptotic and fluorescent photosensitizer. Aprepitant and 5-ALA significantly inhibited GBM cell migration and reduced matrix metalloproteinases (MMP-2 and MMP-9) activities. Importantly, all these effects were more prominent following aprepitant-5-ALA combination treatment than either drug alone. Collectively, the combination of aprepitant and 5-ALA leads to considerable synergistic anti-proliferative, pro-apoptotic, and anti-migratory effects on GBM cells and provides a firm basis for further evaluation of this combination as a novel therapeutic approach for GBM.

The Therapeutic Potential of the Restoration of the p53 Protein Family Members in the EGFR-Mutated Lung Cancer

Despite the recent development of precision medicine and targeted therapies, lung cancer remains the top cause of cancer-related mortality worldwide. The patients diagnosed with metastatic disease have a five-year survival rate lower than 6%. In metastatic disease, EGFR is the most common driver of mutation, with the most common co-driver hitting TP53. EGFR-positive patients are offered the frontline treatment with tyrosine kinase inhibitors, yet the development of resistance and the lack of alternative therapies make this group of patients only fit for clinical trial participation. Since mutant p53 is the most common co-driver in the metastatic setting, therapies reactivating the p53 pathway might serve as a promising alternative therapeutic approach in patients who have developed a resistance to tyrosine kinase inhibitors. This review focuses on the molecular background of EGFR-mutated lung cancer and discusses novel therapeutic options converging on the reactivation of p53 tumor suppressor pathways.

The p53 family member p73 in the regulation of cell stress response

During oncogenesis, cells become unrestrictedly proliferative thereby altering the tissue homeostasis and resulting in subsequent hyperplasia. This process is paralleled by resumption of cell cycle, aberrant DNA repair and blunting the apoptotic program in response to DNA damage. In most human cancers these processes are associated with malfunctioning of tumor suppressor p53. Intriguingly, in some cases two other members of the p53 family of proteins, transcription factors p63 and p73, can compensate for loss of p53. Although both p63 and p73 can bind the same DNA sequences as p53 and their transcriptionally active isoforms are able to regulate the expression of p53-dependent genes, the strongest overlap with p53 functions was detected for p73. Surprisingly, unlike p53, the p73 is rarely lost or mutated in cancers. On the contrary, its inactive isoforms are often overexpressed in cancer. In this review, we discuss several lines of evidence that cancer cells develop various mechanisms to repress p73-mediated cell death. Moreover, p73 isoforms may promote cancer growth by enhancing an anti-oxidative response, the Warburg effect and by repressing senescence. Thus, we speculate that the role of p73 in tumorigenesis can be ambivalent and hence, requires new therapeutic strategies that would specifically repress the oncogenic functions of p73, while keeping its tumor suppressive properties intact.

MDM2, MDMX, and p73 regulate cell-cycle progression in the absence of wild-type p53

The p53 tumor suppressor protein, known to be critically important in several processes including cell-cycle arrest and apoptosis, is highly regulated by multiple mechanisms, most certifiably the Murine Double Minute 2-Murine Double Minute X (MDM2-MDMX) heterodimer. The role of MDM2-MDMX in cell-cycle regulation through inhibition of p53 has been well established. Here we report that in cells either lacking p53 or expressing certain tumor-derived mutant forms of p53, loss of endogenous MDM2 or MDMX, or inhibition of E3 ligase activity of the heterocomplex, causes cell-cycle arrest. This arrest is correlated with a reduction in E2F1, E2F3, and p73 levels. Remarkably, direct ablation of endogenous p73 produces a similar effect on the cell cycle and the expression of certain E2F family members at both protein and messenger RNA levels. These data suggest that MDM2 and MDMX, working at least in part as a heterocomplex, may play a p53-independent role in maintaining cell-cycle progression by promoting the activity of E2F family members as well as p73, making them a potential target of interest in cancers lacking wild-type p53.

The p53 Protein Family in the Response of Tumor Cells to Ionizing Radiation: Problem Development

Survival mechanisms are activated in tumor cells in response to therapeutic ionizing radiation. This reduces a treatment's effectiveness. The p53, p63, and p73 proteins belonging to the family of proteins that regulate the numerous pathways of intracellular signal transduction play a key role in the development of radioresistance. This review analyzes the p53-dependent and p53-independent mechanisms involved in overcoming the resistance of tumor cells to radiation exposure.

Dalhat M, Abdullah O, Kaleem M, Hosawi S, A Al-Abbasi F, Wu W, Choudhry H, Alhosin M. Targeting Post-Translational Modifications of the p73 Protein: A Promising Therapeutic Strategy for Tumors

The tumor suppressor p73 is a member of the p53 family and is expressed as different isoforms with opposing properties. The TAp73 isoforms act as tumor suppressors and have pro-apoptotic effects, whereas the ΔNp73 isoforms lack the N-terminus transactivation domain and behave as oncogenes. The TAp73 protein has a high degree of similarity with both p53 function and structure, and it induces the regulation of various genes involved in the cell cycle and apoptosis. Unlike those of the p53 gene, the mutations in the p73 gene are very rare in tumors. Cancer cells have developed several mechanisms to inhibit the activity and/or expression of p73, from the hypermethylation of its promoter to the modulation of the ratio between its pro- and anti-apoptotic isoforms. The p73 protein is also decorated by a panel of post-translational modifications, including phosphorylation, acetylation, ubiquitin proteasomal pathway modifications, and small ubiquitin-related modifier (SUMO)ylation, that regulate its transcriptional activity, subcellular localization, and stability. These modifications orchestrate the multiple anti-proliferative and pro-apoptotic functions of TAp73, thereby offering multiple promising candidates for targeted anti-cancer therapies. In this review, we summarize the current knowledge of the different pathways implicated in the regulation of TAp73 at the post-translational level. This review also highlights the growing importance of targeting the post-translational modifications of TAp73 as a promising antitumor strategy, regardless of p53 status.

Knockdown of hsa_circ_0059955 Induces Apoptosis and Cell Cycle Arrest in Nucleus Pulposus Cells via Inhibiting Itchy E3 Ubiquitin Protein Ligase

Background

Circular RNAs (circRNAs) play an important role in the progression of intervertebral disc (IVD) degeneration (IVDD). Using bioinformatics analysis, we have found that the expression of circRNA hsa_circ_0059955 was significantly downregulated in IVDD tissues. However, the relevant mechanism of hsa_circ_0059955 in the progression of IVDD remains unclear.

Methods

CCK-8 and flow cytometry assays were used to evaluate cell proliferation and apoptosis. In addition, Western blot assay was used to detect the expressions of ITCH, p73, CDK2 in nucleus pulposus (NP) cells. Moreover, a puncture-induced IVDD rat model was established to explore the role of hsa_circ_0059955 in IVDD.

Results

The level of hsa_circ_0059955 was significantly decreased in IVDD tissues from IVDD patients. Itchy E3 ubiquitin protein ligase (ITCH) is the host gene of hsa_circ_0059955, and downregulation of hsa_circ_0059955 significantly decreased the expression of ITCH in NP cells. In addition, downregulation of hsa_circ_0059955 markedly inhibited proliferation and induced apoptosis and cell cycle arrest in NP cells. Moreover, in vivo study illustrated that overexpression of hsa_circ_0059955 ameliorated IVDD in rats.

Conclusion

Downregulation of hsa_circ_0059955 could induce apoptosis and cell cycle arrest in NP cells in vitro, while overexpression of hsa_circ_0059955 attenuated the IVDD in a puncture-induced rat model in vivo. Therefore, hsa_circ_0059955 might serve as a therapeutic target for the treatment of IVDD.

The Undervalued Avenue to Reinstate Tumor Suppressor Functionality of the p53 Protein Family for Improved Cancer Therapy-Drug Repurposing

p53 and p73 are critical tumor suppressors that are often inactivated in human cancers through various mechanisms. Owing to their high structural homology, the proteins have many joined functions and recognize the same set of genes involved in apoptosis and cell cycle regulation. p53 is known as the 'guardian of the genome' and together with p73 forms a barrier against cancer development and progression. The TP53 is mutated in more than 50% of all human cancers and the germline mutations in TP53 predispose to the early onset of multiple tumors in Li-Fraumeni syndrome (LFS), the inherited cancer predisposition. In cancers where TP53 gene is intact, p53 is degraded. Despite the ongoing efforts, the treatment of cancers remains challenging. This is due to late diagnoses, the toxicity of the current standard of care and marginal benefit of newly approved therapies. Presently, the endeavors focus on reactivating p53 exclusively, neglecting the potential of the restoration of p73 protein for cancer eradication. Taken that several small molecules reactivating p53 failed in clinical trials, there is a need to develop new treatments targeting p53 proteins in cancer. This review outlines the most advanced strategies to reactivate p53 and p73 and describes drug repurposing approaches for the efficient reinstatement of the p53 proteins for cancer therapy.

Protoporphyrin IX is a dual inhibitor of p53/MDM2 and p53/MDM4 interactions and induces apoptosis in B-cell chronic lymphocytic leukemia cells

p53 is a tumor suppressor, which belongs to the p53 family of proteins. The family consists of p53, p63 and p73 proteins, which share similar structure and function. Activation of wild-type p53 or TAp73 in tumors leads to tumor regression, and small molecules restoring the p53 pathway are in clinical development. Protoporphyrin IX (PpIX), a metabolite of aminolevulinic acid, is a clinically approved drug applied in photodynamic diagnosis and therapy. PpIX induces p53-dependent and TAp73-dependent apoptosis and inhibits TAp73/MDM2 and TAp73/MDM4 interactions. Here we demonstrate that PpIX is a dual inhibitor of p53/MDM2 and p53/MDM4 interactions and activates apoptosis in B-cell chronic lymphocytic leukemia cells without illumination and without affecting normal cells. PpIX stabilizes p53 and TAp73 proteins, induces p53-downstream apoptotic targets and provokes cancer cell death at doses non-toxic to normal cells. Our findings open up new opportunities for repurposing PpIX for treating lymphoblastic leukemia with wild-type TP53.

Activation of TAp73 and inhibition of TrxR by Verteporfin for improved cancer therapy in TP53 mutant pancreatic tumors

Aim:

TAp73 is a tumor suppressor, which compensates for p53 loss and induces apoptosis in tumors in response to genotoxic stress or small-molecule treatments. Pancreatic ductal adenocarcinoma has a late onset of the disease, responds poorly to the existing therapies and has a very low survival rates.

Result:

Here, using drug-repurposing approach, we found that protoporphyrin IX (PpIX) and benzoporphyrin derivative (BPD) monoacid ring A activate TAp73 and induce apoptosis in pancreatic cancer cells. PpIX and BPD induce reactive oxygen species and inhibit thioredoxin reductase 1.

Conclusion:

Thus, PpIX and BPD target cancer cells’ vulnerabilities namely activate TAp73 tumor suppressor and inhibit oncogenic Trx1. Our findings may contribute to faster repurposing of PpIX and BPD to treat pancreatic tumors.

Despite all efforts, pancreatic cancer remains one of the most aggressive tumors. Late diagnoses, often linked with the asymptomatic disease progression, make pancreatic cancer extremely difficult to treat. We have assessed drugs that are already clinically used in the photodynamic therapy of actinic keratosis and age-related macular degeneration and showed that the compounds induce apoptotic death of cancer cells. The mechanism is via activation of the p73 tumor suppressor and inhibition of the oncogenic thioredoxin reductase. Molecules with a complementary mechanism of action inducing cell death might be very promising candidates for improved cancer therapy in pancreatic cancer patients.

Two pathways leading to the induction of potent apoptosis by protoporphyrin IX and Verteporfin in mutant TP53 pancreatic cancer cells. One pathway is through inhibition of TAp73/MDM2 interactions and induction of TAp73-related apoptosis and the second pathway converges on inhibition of oncogenic TrxR and accumulation of reactive oxygen species.