Primitive Cancer Cell States: A Target for Drug Screening?

Single-cell and spatial analyses revealed the co-location of cancer stem cells and SPP1+ macrophage in hypoxic region that determines the poor prognosis in hepatocellular carcinoma

In hepatocellular carcinoma (HCC), classical cancer stem cells (CSC) markers were shared by normal stem cells, targeting which may hinder hepatic regeneration and cause liver failure. Additionally, the spatial structure of CSC still remained elusive. To address these limitations, we undertook a comprehensive study combining single-cell data (56,022 cells from 20 samples) and spatial data (38,191 spots from eight samples) to obtain CSC signature and uncover its spatial structure. Utilizing the CytoTRACE algorithm, we discretely identified CSC, which displayed upregulated proliferation pathways regulated by HIF1A. A CSC signature of 107 genes was then developed using Weighted Gene Co-expression Network Analysis (WGCNA). Notably, HCC patients with high CSC levels exhibited an accumulation of SPP1+ macrophages (Macro_SPP1) expressing metalloproteinases (MMP9, MMP12, and MMP7) regulated by HIF1A, suggesting a hypoxic tumor region connecting Macro_SPP1 and CSC. Both CSC and Macro_SPP1 correlated with worse prognosis and undesirable immunotherapy response. Spatial analysis revealed the co-location of CSC and Macro_SPP1, with CD8 T cells excluded from the tumor region. The co-location area and non-tumor area of boundary exhibited a high level of hypoxia, with the HAVRC2 checkpoint highly expressed. Within the co-location area, the SPP1 signaling pathway was most active in cell-cell communication, with SPP1-CD44 and SPP1-ITGA/ITGB identified as the main ligand-receptor pairs. This study successfully constructed a CSC signature and demonstrated the co-location of CSC and Macro_SPP1 in a hypoxic region that exacerbates the tumor microenvironment in HCC.

Tumor microenvironment-based screening repurposes drugs targeting cancer stem cells and cancer-associated fibroblasts

The tumorous niche may drive the plasticity of heterogeneity and cancer stemness, leading to drug resistance and metastasis, which is the main reason of treatment failure in most cancer patients. The aim of this study was to establish a tumor microenvironment (TME)-based screening to identify drugs that can specifically target cancer stem cells (CSCs) and cancer-associated fibroblasts (CAFs) in the TME. Methods: Lung cancer patient-derived cancer cell and CAFs were utilized to mimic the TME and reproduce the stemness properties of CSCs in vitro and develop a high-throughput drug screening platform with phenotypical parameters. Limiting dilution assay, sphere-forming and ALDH activity assay were utilized to measure the cancer stemness characteristics. In vivo patient-derived xenograft (PDX) models and single-cell RNA sequencing were used to evaluate the mechanisms of the compounds in CSCs and CAFs. Results: The TME-based drug screening platform could comprehensively evaluate the response of cancer cells, CSCs and CAFs to different treatments. Among the 1,524 compounds tested, several drugs were identified to have anti-CAFs, anticancer and anti-CSCs activities. Aloe-emodin and digoxin both show anticancer and anti-CSCs activity in vitro and in vivo, which was further confirmed in the lung cancer PDX model. The combination of digoxin and chemotherapy improved therapeutic efficacy. The single-cell transcriptomics analysis revealed that digoxin could suppress the CSCs subpopulation in CAFs-cocultured cancer cells and cytokine production in CAFs. Conclusions: The TME-based drug screening platform provides a tool to identify and repurpose compounds targeting cancer cells, CSCs and CAFs, which may accelerate drug development and therapeutic application for lung cancer patients.

Head and Neck Cancer Stem Cell-Enriched Spheroid Model for Anticancer Compound Screening

Cancer stem cells (CSCs), a rare cell population in tumors, are resistant to conventional chemotherapy and thus responsible for tumor recurrence. To screen for active compounds targeting CSCs, a good CSC-enriched model compatible with high-throughput screening (HTS) is needed. Here, we describe a new head and neck cancer stem cell-enriched spheroid model (SCESM) suitable for HTS analyses of anti-CSC compounds. We used FaDu cells, round-bottom ultra-low adherent (ULA) microplates, and stem medium. The formed spheroids displayed increased expression of all stem markers tested (qRT-PCR and protein analysis) in comparison to the FaDu cells grown in a standard adherent culture or in a well-known HTS-compatible multi-cellular tumor spheroid model (MCTS). Consistent with increased stemness of the cells in the spheroid, confocal microscopy detected fast proliferating cells only at the outer rim of the SCESM spheroids, with poorly/non-proliferating cells deeper in. To confirm the sensitivity of our model, we used ATRA treatment, which strongly reduced the expression of selected stem markers. Altogether, we developed a CSC-enriched spheroid model with a simple protocol, a microplate format compatible with multimodal detection systems, and a high detection signal, making it suitable for anti-CSC compounds' HTS.

Long Term Culture of Human Kidney Proximal Tubule Epithelial Cells Maintains Lineage Functions and Serves as an Ex vivo Model for Coronavirus Associated Kidney Injury

The mechanism of how SARS-CoV-2 causes severe multi-organ failure is largely unknown. Acute kidney injury (AKI) is one of the frequent organ damage in severe COVID-19 patients. Previous studies have shown that human renal tubule cells could be the potential host cells targeted by SARS-CoV-2. Traditional cancer cell lines or immortalized cell lines are genetically and phenotypically different from host cells. Animal models are widely used, but often fail to reflect a physiological and pathogenic status because of species tropisms. There is an unmet need for normal human epithelial cells for disease modeling. In this study, we successfully established long term cultures of normal human kidney proximal tubule epithelial cells (KPTECs) in 2D and 3D culture systems using conditional reprogramming (CR) and organoids techniques. These cells had the ability to differentiate and repair DNA damage, and showed no transforming property. Importantly, the CR KPTECs maintained lineage function with expression of specific transporters (SLC34A3 and cubilin). They also expressed angiotensin-converting enzyme 2 (ACE2), a receptor for SARS-CoV and SARS-CoV-2. In contrast, cancer cell line did not express endogenous SLC34A3, cubilin and ACE2. Very interestingly, ACE2 expression was around twofold higher in 3D organoids culture compared to that in 2D CR culture condition. Pseudovirion assays demonstrated that SARS-CoV spike (S) protein was able to enter CR cells with luciferase reporter. This integrated 2D CR and 3D organoid cultures provide a physiological ex vivo model to study kidney functions, innate immune response of kidney cells to viruses, and a novel platform for drug discovery and safety evaluation.

3D culture technologies of cancer stem cells: promising ex vivo tumor models

Cancer stem cells have been shown to be important in tumorigenesis processes, such as tumor growth, metastasis, and recurrence. As such, many three-dimensional models have been developed to establish an ex vivo microenvironment that cancer stem cells experience under in vivo conditions. Cancer stem cells propagating in three-dimensional culture systems show physiologically related signaling pathway profiles, gene expression, cell-matrix and cell-cell interactions, and drug resistance that reflect at least some of the tumor properties seen in vivo. Herein, we discussed the presently available Cancer stem cell three-dimensional culture models that use biomaterials and engineering tools and the biological implications of these models compared to the conventional ones.

Inhibition of PIM1 attenuates the stem cell-like traits of breast cancer cells by promoting RUNX3 nuclear retention

Finding out the driver gene critical for the maintenance of breast cancer stem cells (BrCSCs) is important for designing a new strategy to eradicate these cells to improve patient's prognosis. Here, in our study, we revealed that PIM1, an oncogenic serine‐threonine kinase and a well‐proven contributor to the tumorigenesis of breast cancer, was involved in BrCSCs regulation and promised to be a new target for eradicating BrCSCs. In brief, PIM1 could enhance the stem cell–like traits of breast cancer cells by promoting the phosphorylation and cytoplasmic localization of RUNX3. The nuclear dislocation of RUNX3 disabled this tumour suppressor and led to breast cancer cells gaining stem cell–like traits. Inhibition of PIM1 significantly induced the nuclear retention of RUNX3, recovered its transcriptional function and attenuated the stem cell–like properties of breast cancer cells. Those findings deepened our understanding of PIM1's oncogenic effect, underlining the significance of PIM1 in designing a new strategy aimed at BrCSCs.

Targeting LA7 breast cancer stem cells of rat through repressing the genes of stemness-related transcription factors using three different biological fluids

Down-regulation of stemness genes expression is important in differentiation therapy against cancer stem cells (CSCs). The aim of this study was to evaluate the Oct4 , Sox2, Nanog, and C-myc expression in rat breast cancer stem cells (LA7) which treated with human ovarian follicular fluid (FF), replicative senescent fibroblast culture supernatant (P14), and 16 h serum starved fibroblast supernatant (16 h-SFS). The cells were exposed to these biological fluids for 24 h, 72 h, and 7 days. Stem-loop RT-qPCR assay was used to quantify the expression of above mentioned genes. Results showed that FF had the least cytotoxic effect on the LA7 cells. Except for Nanog gene, exposure of LA7 cell line to 16 h-SFS and P14 decreased significantly expression of the three other genes after 24 h (P < 0.05). Nanog and Sox2 genes expression was also decreased in LA7 cells which have been already treated with FF for 24 h. Moreover, compared to the control solution, the expression of Oct4 increased significantly after 7 days exposure to FF (P < 0.05). Annexin V-PE /7-AAD-, acridine orange/ethidium bromide staining and doubling time assays revealed apoptosis and necrosis induction by these biological fluids in LA7 cells. Moreover, in an in vitro model of metastasis assay, i.e., scratch test, these fluids exhibited anti-LA7 migration activity which culminated in 16 h-SFS treated cells. Generally, this study showed that FF, 16 h-SFS, and P14 have positive effects on down-regulation of Nanog, Oct4, Sox2 and C-myc expression, and consequently can increase the differentiation of breast cancer stem cells. For the first time, this study provided some evidence indicating that some biological fluids have potential to differentiate the CSCs, show anti- survival, growth-, and cell migration activity.

Integrated analysis of transcriptome-wide m6A methylome of osteosarcoma stem cells enriched by chemotherapy

Aim: To analyze the m⁶A methylome of osteosarcoma stem cells (OSCs). Materials & methods: Chemoresistant OSCs were enriched by doxorubicin treatment. Expression of m⁶A-related enzymes was detected by quantitative real-time-PCR and western blot. MeRIP-seq and RNA-seq were performed to identify differences in m⁶A methylation and gene expression. Data analysis was conducted to explore the modified genes and their clinical significance. Results: Three m⁶A-related enzymes were altered in OSCs. Differentially methylated genes were enriched in some pathways regulating pluripotency of stem cells. The expression of several candidate genes were found consistent with that in GSE33458 dataset, and associated with poor prognosis in osteosarcoma patients. Conclusion: m⁶A may play a role in the emergence and maintaining of OSCs and affect the prognosis.

E2 ubiquitin-conjugating enzymes in cancer: Implications for immunotherapeutic interventions

Despite the medical advances of the 21st century, the incidence of cancer continues to increase and the search for a universal cure remains a major health challenge. Our lack of understanding the complex pathophysiology of the tumor microenvironment has hindered the development and efficiency of anti-cancer therapeutic strategies. The tumor microenvironment, composed of multiple cellular and non-cellular components, enables tumor-promoting processes such as proliferation, angiogenesis, migration and invasion, metastasis, and drug resistance. The ubiquitin-mediated degradation system is involved in several physiologic processes including cell cycling, signal transduction, receptor downregulation, endocytosis and transcriptional regulation. Ubiquitination includes attachment of ubiquitin to target proteins via E1 (activating), E2 (conjugating) and E3 (ligating) enzymes. Several studies have shown that E2 enzymes are dysregulated in variety of cancers. Multiple investigations have demonstrated the involvement of E2s in various tumor-promoting processes including DNA repair, cell cycle progression, apoptosis and oncogenic signaling. E2 enzymes consist of 40 members that facilitate ubiquitin-substrate conjugation thereby modulating the stability and interaction of various proteins. As such, E2s are potential biomarkers as diagnostic, prognostic and therapeutic tools. In this review, we discuss the role of E2s in modulating various types of cancer.