Targeting 14-3-3ε-CDC25A interactions to trigger apoptotic cell death in skin cancer

The Development of CDC25A-Derived Phosphoseryl Peptides That Bind 14-3-3ε with High Affinities

Overexpression of the 14-3-3ε protein is associated with suppression of apoptosis in cutaneous squamous cell carcinoma (cSCC). This antiapoptotic activity of 14-3-3ε is dependent on its binding to CDC25A; thus, inhibiting 14-3-3ε - CDC25A interaction is an attractive therapeutic approach to promote apoptosis in cSCC. In this regard, designing peptide inhibitors of 14-3-3ε - CDC25A interactions is of great interest. This work reports the rational design of peptide analogs of pS, a CDC25A-derived peptide that has been shown to inhibit 14-3-3ε-CDC25A interaction and promote apoptosis in cSCC with micromolar IC50. We designed new peptide analogs in silico by shortening the parent pS peptide from 14 to 9 amino acid residues; then, based on binding motifs of 14-3-3 proteins, we introduced modifications in the pS(174-182) peptide. We studied the binding of the peptides using conventional molecular dynamics (MD) and steered MD simulations, as well as biophysical methods. Our results showed that shortening the pS peptide from 14 to 9 amino acids reduced the affinity of the peptide. However, substituting Gln176 with either Phe or Tyr amino acids rescued the binding of the peptide. The optimized peptides obtained in this work can be candidates for inhibition of 14-3-3ε - CDC25A interactions in cSCC.

14-3-3ε: a protein with complex physiology function but promising therapeutic potential in cancer

Over the past decade, the role of the 14-3-3 protein has received increasing interest. Seven subtypes of 14-3-3 proteins exhibit high homology; however, each subtype maintains its specificity. The 14-3-3ε protein is involved in various physiological processes, including signal transduction, cell proliferation, apoptosis, autophagy, cell cycle regulation, repolarization of cardiac action, cardiac development, intracellular electrolyte homeostasis, neurodevelopment, and innate immunity. It also plays a significant role in the development and progression of various diseases, such as cardiovascular diseases, inflammatory diseases, neurodegenerative disorders, and cancer. These immense and various involvements of 14-3-3ε in diverse processes makes it a promising target for drug development. Although extensive research has been conducted on 14-3-3 dimers, studies on 14-3-3 monomers are limited. This review aimed to provide an overview of recent reports on the molecular mechanisms involved in the regulation of binding partners by 14-3-3ε, focusing on issues that could help advance the frontiers of this field. Video Abstract.

Optimizing Phosphopeptide Structures That Target 14-3-3ε in Cutaneous Squamous Cell Carcinoma

14-3-3ε is involved in various types of malignancies by increasing cell proliferation, promoting cell invasion, or inhibiting apoptosis. In cutaneous squamous cell carcinoma (cSCC), 14-3-3ε is overexpressed and mislocalized from the nucleus to the cytoplasm where it interacts with the cell division cycle 25 A (CDC25A) and suppresses apoptosis. Hence, inhibition of the 14-3-3ε-CDC25A interaction is an attractive target for promoting apoptosis in cSCC. In this work, we optimized the structure of our previously designed inhibitor of the 14-3-3ε-CDC25A interaction, pT, a phosphopeptide fragment corresponding to one of the two binding regions of CDC25A to 14-3-3ε. Starting from pT, we developed peptide analogs that bind 14-3-3ε with nanomolar affinities. Peptide analogs were designed by shortening the pT peptide and introducing modifications at position 510 of the pT(502-510) analog. Both molecular dynamics (MD) simulations and biophysical methods were used to determine peptide binding to 14-3-3ε. Shortening the pT peptide from 14 to 9 amino acid residues resulted in a peptide (pT(502-510)) that binds 14-3-3ε with a KD value of 45.2 nM. Gly to Phe substitution in position 510 of pT(502-510) led to further improvement in affinity (KD: 22.0 nM) of the peptide for 14-3-3ε. Our results suggest that the designed peptide analogs are potential candidates for inhibiting 14-3-3ε-CDC25A interactions in cSCC cells and thus inducing their apoptosis.

Optimizing Phosphopeptide Structures That Target 14-3-3ε in Cutaneous Squamous Cell Carcinoma

14-3-3ε is involved in various types of malignancies by increasing cell proliferation, promoting cell invasion or inhibiting apoptosis. In cutaneous squamous cell carcinoma (cSCC), 14-3-3ε is over expressed and mislocalized from the nucleus to the cytoplasm where it interacts with the cell division cycle 25 A (CDC25A) and suppresses apoptosis. Hence inhibition of the 14-3-3ε - CDC25A interaction is an attractive target for promoting apoptosis in cSCC. In this work, we optimized the structure of our previously designed inhibitor of 14-3-3ε - CDC25A interaction, pT, a phosphopeptide fragment corresponding to one of the two binding regions of CDC25A to 14-3-3ε. Starting from pT, we developed peptide analogs that bind 14-3-3ε with nanomolar affinities. Peptide analogs were designed by shortening the pT peptide, and introducing modifications at position 510 of the pT(502-510) analog. Both molecular dynamics (MD) simulations and biophysical methods were used to determine peptides binding to 14-3-3ε. Shortening the pT peptide from 14 to 9 amino acid residues resulted in a peptide (pT(502-510)) that binds 14-3-3ε with a KD value of 45.2 nM. Gly to Phe substitution in position 510 of pT(502-510) led to further improvement in affinity (KD: 22.0 nM) of the peptide for 14-3-3ε. Our results suggest that the designed peptide analogs are potential candidates for inhibiting 14-3-3ε -CDC25A interactions in cSCC cells; thus, inducing their apoptosis.

Immortalization-upregulated protein promotes pancreatic cancer progression by regulating NPM1/FHL1-mediated cell-cycle-checkpoint protein activity

Immortalization-upregulated protein (IMUP) plays a vital role in cell proliferation and tumor progression. However, its role in pancreatic ductal adenocarcinoma (PDAC) remains unclear. Here, we select IMUP as an alternative gene based on GeneChip analysis of clinical PDAC tissues and transcriptome data from The Cancer Genome Atlas. IMUP expression is upregulated in PDAC tumor tissues. Moreover, high IMUP expression correlates with poor prognosis, while IMUP depletion inhibits PDAC cell proliferation and colony formation capacity in vitro, and decreases xenograft tumor growth in vivo. IMUP downregulation leads to cell-cycle arrest in the S phase. IMUP knockdown increases the expression of four-and-a-half LIM domain protein 1 (FHL1), which regulates the phosphorylation of cell division cycle 25A (CDC25A) by cycle checkpoint kinase 1 (CHK1) and promotes cytoplasmic distribution of CDC25A by interaction with 14-3-3ξ. Furthermore, FHL1 knockdown restores the effects induced by IMUP depletion. Liquid chromatography tandem mass spectrometry and immunoprecipitation analysis further show that IMUP interacts directly with nucleophosmin (NPM1) and enhances its stability. DNA methylation sequencing shows that FHL1 promoter methylation decreases when IMUP is downregulated. Overexpression of NPM1 can increase the methylation level of FHL1, thereby decreasing its expression. Our study provides a novel perspective on IMUP/NPM1/FHL1-mediated cell-cycle arrest by regulating CDC25A phosphorylation in PDAC. These findings may provide a new therapeutic target for PDAC.

TXNDC9 knockdown inhibits lung adenocarcinoma progression by targeting YWHAG

Lung adenocarcinoma (LUAD) is the most common form of lung cancer and with the highest mortality rate. Therefore, the identification and development of effective methods for the treatment of LUAD is of great importance. The present study aimed to investigate the role of thioredoxin domain-containing protein 9 (TXNDC9) and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein γ (YWHAG; also known as 14-3-3γ) in the progression of LUAD. The expression of TXNDC9 and its association with the survival of patients with LUAD was analyzed using Encyclopedia of RNA Interactomes. Reverse transcription-quantitative PCR and western blot analysis were used to detect TXNDC9 mRNA and protein expression levels, respectively, in in vitro studies. To investigate the role of TXNDC9 in the progression of LUAD, TXNDC9 was silenced using small interfering RNA transfection. Furthermore, the viability, proliferation, migration, invasiveness and apoptosis of TXNDC9-silenced A549 cells were detected using Cell Counting Kit (CCK)-8, colony formation, wound healing, Transwell and TUNEL assays, respectively. The association between TXNDC9 and YWHAG was analyzed using STRING and Gene Expression Profiling Interactive Analysis databases, as well as co-immunoprecipitation assays. Subsequently, YWHAG was overexpressed to similarly determine effects of YWHAG on viability, proliferation, migration, invasiveness and apoptosis of A549 cells. TXNDC9 expression was markedly upregulated in lung cancer cells, particularly A549 cells, and silencing of TXNDC9 expression suppressed the viability of the lung cancer cells. The results also revealed that TXNDC9 silencing exerted inhibitory effects on the viability, proliferation, migration and invasiveness of A549 cells, whereas the apoptotic rate was increased. Similar to TXNDC9, YWHAG expression was also upregulated in the A549 cells. Furthermore, TXNDC9 was demonstrated to bind to YWHAG and was positively associated with YWHAG. YWHAG overexpression reversed the inhibitory effects of TXNDC9 silencing on LUAD, as evidenced by increased viability, proliferation, migration and invasiveness, and decreased apoptosis, of A549 cells. The present study demonstrated that the knockdown of TXNDC9 exerted suppressive effects on LUAD, whereas YWHAG overexpression reversed the inhibitory effects of TXNDC9 silencing on LUAD. Therefore, TXNDC9 silencing may exert protective effects against LUAD by targeting YWHAG.

A Comprehensive Overview of the Developments of Cdc25 Phosphatase Inhibitors

Cdc25 phosphatases have been considered promising targets for anticancer development due to the correlation of their overexpression with a wide variety of cancers. In the last two decades, the interest in this subject has considerably increased and many publications have been launched concerning this issue. An overview is constructed based on data analysis of the results of the previous publications covering the years from 1992 to 2021. Thus, the main objective of the current review is to report the chemical structures of Cdc25s inhibitors and answer the question, how to design an inhibitor with better efficacy and lower toxicity?