Cellular Hierarchy as a Determinant of Tumor Sensitivity to Chemotherapy

Predicting Survival Signature of Bladder Cancer Related to Cancer-Associated Fibroblast (CAF) Constructed by Intersecting Genes in TCGA and GEO

Bladder cancer was one of the most common carcinomas around the world. However, the mechanism of the disease still remained to be investigated. We expected to establish a prognostic survival model with 9 prognostic genes to predict overall survival (OS) in patients of bladder cancer. The gene expression data of bladder cancer were obtained from TCGA and GEO datasets. TCGA and GEO datasets were used for screening prognostic genes along with developing and validating a 9-gene prognostic survival model by method of weighted gene co-expression network analysis (WGCNA) and LASSO with Cox regression. The relative analysis of evaluate tumor burden mutation (TBM), GO, KEGG, chemotherapy drug and functional pathway were also performed based on CAF-related mRNAs. 151 Overlapping CAF-related genes were distinguished after intersecting differentially expressed genes from 945 genes in TCGA and 491 genes in GEO dataset. 9 Prognostic genes (MSRB2, AGMAT, KLF6, DDAH2, GADD45B, SERPINE2, STMN3, TEAD2, and COMP) were used for construction of prognostic model after LASSO with Cox regression. Receiver operating characteristic (ROC) curves showed a good survival prediction by this model. Functional analysis indicated chemokine, cytokine, ECM interaction, oxidative stress and apoptosis were highly appeared. Potential drugs targeted different CAF-related genes like vemurafenib, irofulven, ghiotepa, and idarubicin were found as well. We constructed a novel 9 CAF-related mRNAs prognostic model and explored the gene expression and potential functional information of related genes, which might be worthy of clinical application. In addition, potential chemotherapy drugs could provide useful insights into the potential clinical treatment of bladder cancer.

WDR76 regulates 5-fluorouracil sensitivity in colon cancer via HRAS

BACKGROUND

WD repeat domain 76 (WDR76) has been reported in multiple tumors, while without relation to chemotherapy resistance. 5-fluorouracil (5-FU) is widely adopted in treating colon cancer. However, the resistance of WDR76 and 5-FU in colon cancer remains unclear.

METHODS

Limma package in R software was employed to analyze the differentially expressed genes. Western blot or quantitative real-time PCR (qRT-PCR) were run to assessed the gene expression. The cytotoxic effect was determined according to cell viability assay, colony formation assay in vitro. Cell apoptosis was assayed using flow cytometry. GSEA analysis was performed to identify pathways related to the target gene. Xenografted mice model was employed to evaluate the tumor growth.

RESULTS

Bioinformatic analysis revealed the higher expression of WDR76 in 5-FU sensitive colon cancer cells compared to resistant colon cancer cells, accompanied by the decreased mRNA expression of WDR76 in 5-FU resistant colon cancer cells. The overexpressed WDR76 resulted in the apoptosis and the downregulated colony numbers in 5-FU resistant colon cancer cells, leading to the elevated sensitivity of 5-FU. Meanwhile, knockdown of WDR76 enhances the resistance of 5-FU in colon cancer both in vitro and vivo, which was reversed by a specific inhibitor of HRAS, Kobe006. An important molecular mechanism of 5-FU resistance lies the degradation of HRAS induced by WDR76.

CONCLUSION

Our findings demonstrated a role of WDR76 as a promising target for reversing the resistance of colon cancer to 5-FU.

Eta polycaprolactone (ε-PCL) implants appear to cause a partial differentiation of breast cancer lung metastasis in a murine model

BACKGROUND

Cells in every epithelium can be roughly divided in three compartments: stem cell (SC) compartment, transient amplifying cell (TA) compartment and terminally differentiated (TD) compartment. Maturation of stem cells is characterized by epithelial stromal interaction and sequential maturational movement of stem cell's progeny through those compartments. In this work we hypothesize that providing an artificial stroma, which murine breast cancer metastatic cells can infiltrate, will induce their differentiation.

METHODS

BALB/c female mice were injected with 10⁶ isogenic 4T1 breast cancer cells labeled with GFP. After 20 days primary tumors were removed, and artificial ε-PCL implants were implanted on the contralateral side. After 10 more days mice were sacrificed and implants along with lung tissue were harvested. Mice were divided in four groups: tumor removal with sham implantation surgery (n = 5), tumor removal with ε-PCL implant (n = 5), tumor removal with VEGF enriched ε-PCL implant (n = 7) and mice without tumor with VEGF enriched ε-PCL implant (n = 3). Differentiational status of GFP + cells was assessed by Ki67 and activated caspase 3 expression, thus dividing the population in SC like cells (Ki67^+/dim aCasp3^-), TA like cells (Ki67^+/dim aCasp3^+/dim) and TD like cells (Ki67^- aCasp3^+/dim) on flow cytometry.

RESULTS

Lung metastatic load was reduced by 33% in mice with simple ε-PCL implant when compared to tumor bearing group with no implant. Mice with VEGF enriched implants had 108% increase in lung metastatic load in comparison to tumor bearing mice with no implants. Likewise, amount of GFP + cells was higher in simple ε-PCL implant in comparison to VEGF enriched implants. Differentiation-wise, process of metastasizing to lungs reduces the average fraction of SC like cells when compared to primary tumor. This effect is made more uniform by both kinds of ε-PCL implants. The opposite process is mirrored in TA like cells compartment when it comes to averages. Effects of both types of implants on TD like cells were negligible. Furthermore, if gene expression signatures that mimic tissue compartments are analyzed in human breast cancer metastases, it turns out that TA signature is associated with increased survival probability.

CONCLUSION

ε-PCL implants without VEGF can reduce metastatic loads in lungs, after primary tumor removal. Both types of implants cause lung metastasis differentiation by shifting cancer cells from SC to TA compartment, leaving the TD compartment unaffected.

Trabectedin suppresses escape from therapy-induced senescence in tumor cells by interfering with glutamine metabolism

Conventional and targeted cancer therapies may induce a cellular senescence program termed therapy-induced senescence. However, unlike normal cells, cancer cells are able to evade the senescence cell cycle arrest and to resume proliferation, driving tumor recurrence after treatments. Cells that escape from therapy-induced senescence are characterized by a plastic, cancer stem cell-like phenotype, and recent studies are beginning to define their unique metabolic features, such as glutamine dependence. Here, we show that the antineoplastic drug trabectedin suppresses escape from therapy-induced senescence in all cell lines studied, and reduces breast cancer stem-like cells, at concentrations that do not affect the viability of senescent tumor cells. We demonstrate that trabectedin downregulates both the glutamine transporter SLC1A5 and glutamine synthetase, thereby interfering with glutamine metabolism. On the whole, our results indicate that trabectedin targets a glutamine-dependent cancer stem-like cell population involved in evasion from therapy-induced senescence and suggest a therapeutic potential for trabectedin combined with pro-senescence chemotherapy in tumor treatment.

Spatial dynamics of feedback and feedforward regulation in cell lineages

Feedback mechanisms within cell lineages are thought to be important for maintaining tissue homeostasis. Mathematical models that assume well-mixed cell populations, together with experimental data, have suggested that negative feedback from differentiated cells on the stem cell self-renewal probability can maintain a stable equilibrium and hence homeostasis. Cell lineage dynamics, however, are characterized by spatial structure, which can lead to different properties. Here, we investigate these dynamics using spatially explicit computational models, including cell division, differentiation, death, and migration / diffusion processes. According to these models, the negative feedback loop on stem cell self-renewal fails to maintain homeostasis, both under the assumption of strong spatial restrictions and fast migration / diffusion. Although homeostasis cannot be maintained, this feedback can regulate cell density and promote the formation of spatial structures in the model. Tissue homeostasis, however, can be achieved if spatially restricted negative feedback on self-renewal is combined with an experimentally documented spatial feedforward loop, in which stem cells regulate the fate of transit amplifying cells. This indicates that the dynamics of feedback regulation in tissue cell lineages are more complex than previously thought, and that combinations of spatially explicit control mechanisms are likely instrumental.

Biomacromolecule-based photo-thermal agents for tumor treatment

Cancer treatment has become one of the biggest challenges in modern medicine. Recently, many efforts have been devoted to treat tumors by surgical resection, radiotherapy, or chemotherapy. In comparison to these methods, photo-thermal therapy (PTT) with noninvasive, controllable, direct, and precise characteristics has received tremendous attention in eliminating tumor cells over the past decades. In particular, PTT based on biomacromolecule-based photo-thermal agents (PTAs) outperforms other systems with high photo-thermal efficiency, simple coating, and low immunogenicity. Considering the unique advantages of biomacromolecule-based PTAs in tumor treatment, it is necessary to summarize the recent progress in the field of biomacromolecule-based PTAs for tumor treatment. Herein, this minireview outlines recent progress in the fabrication and applications of biomacromolecule-based PTAs. Within this framework, various types of biomacromolecule-based PTAs are highlighted, including cell-based agents, protein-based agents, nucleotide-based agents, and polysaccharide-based PTAs. In each section, the functional design, photo-thermal effects, and potential clinical applications of each type of PTA are discussed. Finally, a brief perspective for the development of biomacromolecule-based PTAs is presented.

Evolution of cancer stem cell lineage involving feedback regulation

Tumor emergence and progression is a complex phenomenon that assumes special molecular and cellular interactions. The hierarchical structuring and communication via feedback signaling of different cell types, which are categorized as the stem, progenitor, and differentiated cells in dependence of their maturity level, plays an important role. Under healthy conditions, these cells build a dynamical system that is responsible for facilitating the homeostatic regulation of the tissue. Generally, in this hierarchical setting, stem and progenitor cells are yet likely to undergo a mutation, when a cell divides into two daughter cells. This may lead to the development of abnormal characteristics, i.e. mutation in the cell, yielding an unrestrained number of cells. Therefore, the regulation of a stem cell’s proliferation and differentiation rate is crucial for maintaining the balance in the overall cell population. In this paper, a maturity based mathematical model with feedback regulation is formulated for healthy and mutated cell lineages. It is given in the form of coupled ordinary and partial differential equations. The focus is laid on the dynamical effects resulting from acquiring a mutation in the hierarchical structure of stem, progenitor and fully differentiated cells. Additionally, the effects of nonlinear feedback regulation from mature cells into both stem and progenitor cell populations have been inspected. The steady-state solutions of the model are derived analytically. Numerical simulations and results based on a finite volume scheme underpin various expected behavioral patterns of the homeostatic regulation and cancer evolution. For instance, it has been found that the mutated cells can experience significant growth even with a single somatic mutation, but under homeostatic regulation acquire a steady-state and thus, ensuing healthy cell population to either a steady-state or a lower cell concentration. Furthermore, the model behavior has been validated with different experimentally measured tumor values from the literature.

Effect of feedback regulation on stem cell fractions in tissues and tumors: Understanding chemoresistance in cancer

While resistance mutations are often implicated in the failure of cancer therapy, lack of response also occurs without such mutants. In bladder cancer mouse xenografts, repeated chemotherapy cycles have resulted in cancer stem cell (CSC) enrichment, and consequent loss of therapy response due to the reduced susceptibility of CSCs to drugs. A particular feedback loop present in the xenografts has been shown to promote CSC enrichment in this system. Yet, many other regulatory loops might also be operational and might promote CSC enrichment. Their identification is central to improving therapy response. Here, we perform a comprehensive mathematical analysis to define what types of regulatory feedback loops can and cannot contribute to CSC enrichment, providing guidance to the experimental identification of feedback molecules. We derive a formula that reveals whether or not the cell population experiences CSC enrichment over time, based on the properties of the feedback. We find that negative feedback on the CSC division rate or positive feedback on differentiated cell death rate can lead to CSC enrichment. Further, the feedback mediators that achieve CSC enrichment can be secreted by either CSCs or by more differentiated cells. The extent of enrichment is determined by the CSC death rate, the CSC self-renewal probability, and by feedback strength. Defining these general characteristics of feedback loops can guide the experimental screening for and identification of feedback mediators that can promote CSC enrichment in bladder cancer and potentially other tumors. This can help understand and overcome the phenomenon of CSC-based therapy resistance.

Effect of cellular de-differentiation on the dynamics and evolution of tissue and tumor cells in mathematical models with feedback regulation

Tissues are maintained by adult stem cells that self-renew and also differentiate into functioning tissue cells. Homeostasis is achieved by a set of complex mechanisms that involve regulatory feedback loops. Similarly, tumors are believed to be maintained by a minority population of cancer stem cells, while the bulk of the tumor is made up of more differentiated cells, and there is indication that some of the feedback loops that operate in tissues continue to be functional in tumors. Mathematical models of such tissue hierarchies, including feedback loops, have been analyzed in a variety of different contexts. Apart from stem cells giving rise to differentiated cells, it has also been observed that more differentiated cells can de-differentiate into stem cells, both in healthy tissue and tumors, aspects of which have also been investigated mathematically. This paper analyses the effect of de-differentiation on the basic and evolutionary dynamics of cells in the context of tissue hierarchy models that include negative feedback regulation of the cell populations. The models predict that in the presence of de-differentiation, the fixation probability of a neutral mutant is lower than in its absence. Therefore, if de-differentiation occurs, a mutant with identical parameters compared to the wild-type cell population behaves like a disadvantageous mutant. Similarly, the process of de-differentiation is found to lower the fixation probability of an advantageous mutant. These results indicate that the presence of de-differentiation can lower the rates of tumor initiation and progression in the context of the models considered here.