Structure-Activity Relationship Analysis of YM155 for Inducing Selective Cell Death of Human Pluripotent Stem Cells

Epigenetic repression of CHCHD2 enhances survival from single cell dissociation through attenuated Rho A kinase activity

During in vitro culture, human pluripotent stem cells (hPSCs) often acquire survival advantages characterized by decreased susceptibility to mitochondrial cell death, known as "culture adaptation." This adaptation is associated with genetic and epigenetic abnormalities, including TP53 mutations, copy number variations, trisomy, and methylation changes. Understanding the molecular mechanisms underlying this acquired survival advantage is crucial for safe hPSC-based cell therapies. Through transcriptome and methylome analysis, we discovered that the epigenetic repression of CHCHD2, a mitochondrial protein, is a common occurrence during in vitro culture using enzymatic dissociation. We confirmed this finding through genetic perturbation and reconstitution experiments in normal human embryonic stem cells (hESCs). Loss of CHCHD2 expression conferred resistance to single cell dissociation-induced cell death, a common stress encountered during in vitro culture. Importantly, we found that the downregulation of CHCHD2 significantly attenuates the activity of Rho-associated protein kinase (ROCK), which is responsible for inducing single cell death in hESCs. This suggests that hESCs may survive routine enzyme-based cell dissociation by downregulating CHCHD2 and thereby attenuating ROCK activity. These findings provide insights into the mechanisms by which hPSCs acquire survival advantages and adapt to in vitro culture conditions.

Small Molecule Inhibitors Targeting the "Undruggable" Survivin: The Past, Present, and Future from a Medicinal Chemist's Perspective

Survivin, a homodimeric protein and a member of the IAP family, plays a vital function in cell survival and cycle progression by interacting with various proteins and complexes. Its expression is upregulated in cancers but not detectable in normal tissues. Thus, it has been regarded and validated as an ideal cancer target. However, survivin is "undruggable" due to its lack of enzymatic activities or active sites for small molecules to bind/inhibit. Academic and industrial laboratories have explored different strategies to overcome this hurdle over the past two decades, with some compounds advanced into clinical testing. These strategies include inhibiting survivin expression, its interaction with binding partners and homodimerization. Here, we provide comprehensive analyses of these strategies and perspective on different small molecule survivin inhibitors to help drug discovery targeting "undruggable" proteins in general and survivin specifically with a true survivin inhibitor that will prevail in the foreseeable future.

E3 ubiquitin ligase APC/CCdh1 regulates SLC35F2 protein turnover and inhibits cancer progression in HeLa cells

BACKGROUND

The solute carrier family 35 F2 (SLC35F2), belongs to membrane-bound carrier proteins that control various physiological functions and are activated in several cancers. However, the molecular mechanism regulating SLC35F2 protein turnover and its implication in cancer progression remains unexplored. Therefore, screening for E3 ligases that promote SLC35F2 protein degradation is essential during cancer progression.

METHODS

The immunoprecipitation and Duolink proximity ligation assays (PLA) were used to determine the interaction between APC/CCdh1 and SLC35F2 proteins. A CRISPR/Cas9-mediated knockdown and rescue experiment were used to validate the functional significance of APC/CCdh1 on SLC35F2 protein stabilization. The ubiquitination function of APC/CCdh1 on SLC35F2 protein was validated using in vitro ubiquitination assay and half-life analysis. The role of APC/CCdh1 regulating SLC35F2-mediated tumorigenesis was confirmed by in vitro oncogenic experiments in HeLa cells.

RESULTS

Based on the E3 ligase screen and in vitro biochemical experiments, we identified that APC/CCdh1 interacts with and reduces SLC35F2 protein level. APC/CCdh1 promotes SLC35F2 ubiquitination and decreases the half-life of SLC35F2 protein. On the other hand, the CRISPR/Cas9-mediated depletion of APC/CCdh1 increased SLC35F2 protein levels. The mRNA expression analysis revealed a negative correlation between APC/CCdh1 and SLC35F2 across a panel of cancer cell lines tested. Additionally, we demonstrated that depletion in APC/CCdh1 promotes SLC35F2-mediated cell proliferation, colony formation, migration, and invasion in HeLa cells.

CONCLUSION

Our study highlights that APC/CCdh1 is a critical regulator of SLC35F2 protein turnover and depletion of APC/CCdh1 promotes SLC35F2-mediated tumorigenesis. Thus, we envision that APC/CCdh1-SLC35F2 axis might be a therapeutic target in cancer.

MutSα and MutSβ as size-dependent cellular determinants for prime editing in human embryonic stem cells

Precise genome editing in human pluripotent stem cells (hPSCs) has potential applications in isogenic disease modeling and ex vivo stem cell therapy, necessitating diverse genome editing tools. However, unlike differentiated somatic cells, hPSCs have unique cellular properties that maintain genome integrity, which largely determine the overall efficiency of an editing tool. Considering the high demand for prime editors (PEs), it is imperative to characterize the key molecular determinants of PE outcomes in hPSCs. Through homozygous knockout (KO) of MMR pathway key proteins MSH2, MSH3, and MSH6, we reveal that MutSα and MutSβ determine PE efficiency in an editing size-dependent manner. Notably, MSH2 perturbation disrupted both MutSα and MutSβ complexes, dramatically escalating PE efficiency from base mispair to 10 bases, up to 50 folds. Similarly, impaired MutSα by MSH6 KO improved editing efficiency from single to three base pairs, while defective MutSβ by MSH3 KO heightened efficiency from three to 10 base pairs. Thus, the size-dependent effect of MutSα and MutSβ on prime editing implies that MMR is a vital PE efficiency determinant in hPSCs and highlights the distinct roles of MutSα and MutSβ in its outcome.

TPX2 prompts mitotic survival via the induction of BCL2L1 through YAP1 protein stabilization in human embryonic stem cells

Genetic alterations have been reported for decades in most human embryonic stem cells (hESCs). Survival advantage, a typical trait acquired during long-term in vitro culture, results from the induction of BCL2L1 upon frequent copy number variation (CNV) at locus 20q11.21 and is one of the strongest candidates associated with genetic alterations that occur via escape from mitotic stress. However, the underlying mechanisms for BCL2L1 induction remain unknown. Furthermore, abnormal mitosis and the survival advantage that frequently occur in late passage are associated with the expression of BCL2L1, which is in locus 20q11.21. In this study, we demonstrated that the expression of TPX2, a gene located in 20q11.21, led to BCL2L1 induction and consequent survival traits under mitotic stress in isogenic pairs of hESCs and human induced pluripotent stem cells (iPSCs) with normal and 20q11.21 CNVs. High Aurora A kinase activity by TPX2 stabilized the YAP1 protein to induce YAP1-dependent BCL2L1 expression. A chemical inhibitor of Aurora A kinase and knockdown of YAP/TAZ significantly abrogated the high tolerance to mitotic stress through BCL2L1 suppression. These results suggest that the collective expression of TPX2 and BCL2L1 from CNV at loci 20q11.21 and a consequent increase in YAP1 signaling promote genome instability during long-term in vitro hESC culture.

Establishment of a human induced pluripotent stem cell line, KRIBBi006-A, from peripheral blood mononuclear cells derived from a healthy male donor

Given the advantage of being able to be extracted by a minimally invasive method, blood is regarded as a suitable cell source for reprogramming to establish induced pluripotent stem cells (iPSCs). Therefore, iPSCs established from patient derived peripheral blood mononuclear cells (PBMCs) is widely used to develop disease modeling to elucidate disease development. Here, PBMCs from a healthy man were reprogrammed into iPSCs using the Sendai virus. The established iPSC line, KRIBBi006-A, exhibit pluripotency marker and can differentiate into the three germ layers in vitro with normal karyotype. This iPSC line is a valuable resource as a control line for stem cell research of disease models and drug screening.

Enzymatically Forming Intranuclear Peptide Assemblies for Selectively Killing Human Induced Pluripotent Stem Cells

Tumorigenic risk of undifferentiated human induced pluripotent stem cells (iPSCs), being a major obstacle for clinical application of iPSCs, requires novel approaches for selectively eliminating undifferentiated iPSCs. Here, we show that an l-phosphopentapeptide, upon the dephosphorylation catalyzed by alkaline phosphatase (ALP) overexpressed by iPSCs, rapidly forms intranuclear peptide assemblies made of α-helices to selectively kill iPSCs. The phosphopentapeptide, consisting of four l-leucine residues and a C-terminal l-phosphotyrosine, self-assembles to form micelles/nanoparticles, which transform into peptide nanofibers/nanoribbons after enzymatic dephosphorylation removes the phosphate group from the l-phosphotyrosine. The concentration of ALP and incubation time dictates the morphology of the peptide assemblies. Circular dichroism and FTIR indicate that the l-pentapeptide in the assemblies contains a mixture of an α-helix and aggregated strands. Incubating the l-phosphopentapeptide with human iPSCs results in rapid killing of the iPSCs (=<2 h) due to the significant accumulation of the peptide assemblies in the nuclei of iPSCs. The phosphopentapeptide is innocuous to normal cells (e.g., HEK293 and hematopoietic progenitor cell (HPC)) because normal cells hardly overexpress ALP. Inhibiting ALP, mutating the l-phosphotyrosine from the C-terminal to the middle of the phosphopentapeptides, or replacing l-leucine to d-leucine in the phosphopentapeptide abolishes the intranuclear assemblies of the pentapeptides. Treating the l-phosphopentapeptide with cell lysate of normal cells (e.g., HS-5) confirms the proteolysis of the l-pentapeptide. This work, as the first case of intranuclear assemblies of peptides, not only illustrates the application of enzymatic noncovalent synthesis for selectively targeting nuclei of cells but also may lead to a new way to eliminate other pathological cells that express a high level of certain enzymes.

Luteolin Induces Selective Cell Death of Human Pluripotent Stem Cells

Despite recent advances in clinical stem cell therapy applications based on human pluripotent stem cells (hPSCs), potential teratoma formation due to the presence of residual undifferentiated hPSCs remains a serious risk factor that challenges widespread clinical application. To overcome this risk, a variety of approaches have been developed to eliminate the remaining undifferentiated hPSCs via selective cell death induction. Our study seeks to identify natural flavonoids that are more potent than quercetin (QC), to selectively induce hPSC death. Upon screening in-house flavonoids, luteolin (LUT) is found to be more potent than QC to eliminate hPSCs in a p53-dependent manner, but not hPSC-derived smooth muscle cells or perivascular progenitor cells. Particularly, treating human embryonic stem cell (hESC)-derived cardiomyocytes with LUT efficiently eliminates the residual hESCs and only results in marginal effects on cardiomyocyte (CM) functions, as determined by calcium influx. Considering the technical limitations of isolating CMs due to a lack of exclusive surface markers at the end of differentiation, LUT treatment is a promising approach to minimize teratoma formation risk.

Knockdown of SLC35F2 Inhibits the Proliferation and Metastasis of Bladder Cancer Cells

Background

Many studies have shown that solute carrier family 35 member F2 (SLC35F2) plays a key role in the biological processes of multiple cancers. However, there have been no reports on the role of SLC35F2 in the occurrence and development of bladder cancer (BC).

Methods

SLC35F2 expression data and clinical and prognostic information from BC patients were obtained from databases. SLC35F2 expression in BC was verified by quantitative real-time PCR (qRT-PCR). The influence of SLC35F2 knockdown on the proliferation, apoptosis, migration and invasion in the 5637 and T24 cell lines was studied, and tumor formation experiments were performed in nude mice. Gene set enrichment analysis (GSEA) was used to predict the pathways and functions of SLC35F2 in BC.

Results

SLC35F2 was highly expressed in BC tissues and was associated with invasiveness and T stage in BC patients. SLC35F2 knockdown can inhibit the proliferation, migration and invasion of BC cells and can promote apoptosis. SLC35F2 knockdown significantly reduced tumorigenesis in nude mice. GSEA showed that BC, pathways in cancer, apoptosis and the P53 signaling pathway were significantly enriched in SLC35F2 high expression phenotype.

Conclusion

SLC35F2 can promote malignant progression and is a potential therapeutic target in BC.