Decreased mitochondrial priming determines chemoresistance of colon cancer stem cells. Cell Death Differ. 2014;21:1170-1177. [PMID: 24682005 DOI: 10.1038/cdd.2014.37]

The tumor microenvironment: shaping cancer progression and treatment response

The tumor microenvironment (TME) plays a crucial role in cancer progression and treatment response. It comprises a complex network of stromal cells, immune cells, extracellular matrix, and blood vessels, all of which interact with cancer cells and influence tumor behaviour. This review article provides an in-depth examination of the TME, focusing on stromal cells, blood vessels, signaling molecules, and ECM, along with commonly available therapeutic compounds that target these components. Moreover, we explore the TME as a novel strategy for discovering new anti-tumor drugs. The dynamic and adaptive nature of the TME offers opportunities for targeting specific cellular interactions and signaling pathways. We discuss emerging approaches, such as combination therapies that simultaneously target cancer cells and modulate the TME. Finally, we address the challenges and future prospects in targeting the TME. Overcoming drug resistance, improving drug delivery, and identifying new therapeutic targets within the TME are among the challenges discussed. We also highlight the potential of personalized medicine and the integration of emerging technologies, such as immunotherapy and nanotechnology, in TME-targeted therapies. This comprehensive review provides insights into the TME and its therapeutic implications. Understanding the TME's complexity and targeting its components offer promising avenues for the development of novel anti-tumor therapies and improved patient outcomes.

Folate induces stemness and increases oxygen consumption under glucose deprivation by notch-1 pathway activation in colorectal cancer cell

Evidence for folate's protective effects on neural tube defects led the USA and Chile to start mandatory folic acid (FA) fortification programs, decreasing up to 50%. However, ∼30% of the population consuming fortified foods reach supraphysiologic serum levels. Although controversial, several epidemiological and clinical observations suggest that folate increases cancer risk, giving concern about the risks of FA supplementation. The Cancer stem cells (CSCs) model has been used to explain survival to anticancer therapies. The Notch-1 pathway plays a role in several cancers and is associated with the stemness process. Different studies show that modulation of metabolic pathways regulates stemness capacity in cancer. Supraphysiologic concentrations of FA increase the proliferation of HT-29 cells by Notch-1 activation. However, whether folate can induce a stemness-like phenotype in cancer is not known. We hypothesized that FA protects from glucose deprivation-induced cell death through Notch-1 activation. HT-29 cells were challenged with glucose deprivation at basal (20 nM) and supraphysiological (400 nM) FA and 5-MTHF concentrations. We analyzed changes in stemness-like gene expression, cell death and different energetic metabolic functions. Supraphysiological concentrations of FA increased stemness-like genes, and improved survival and oxygen consumption, inducing AMPK phosphorylation and HSP-70 protein expression. We evaluated the Notch-1 pathway using the DAPT and siRNA as inhibitors, decreasing the stemness-like gene expression and preventing the FA protection against glucose deprivation-induced cell death. Moreover, they decreased oxygen consumption and AMPK phosphorylation. These results suggest that FA protects against glucose deprivation. These effects were associated with AMPK activation, a critical metabolic mediator in nutrient consumption and availability that activates the Notch-1 pathway.

Singlet Oxygen-Induced Mitochondrial Reset in Cancer: A Novel Approach for Ovarian Cancer Therapy

Background/Objectives: This study explores the generation of singlet oxygen (SO) through methylene blue (MB) activation as a metabolic intervention for ovarian cancer. We aimed to examine the role of SO in modulating mitochondrial function, cellular metabolism, and proliferation in ovarian cancer cell lines compared to control cells. Methods: The study utilized two ovarian cancer cell lines, OV1369-R2 and TOV1369, along with ARPE-19 control cells. Following MB treatment and light activation, mitochondrial function and ATP synthesis were assessed. Metabolomic analyses were performed to evaluate changes in central carbon metabolism, particularly focusing on markers of the Warburg effect. Results: TOV1369 cells exhibited a pronounced sensitivity to MB treatment, resulting in significant inhibition of ATP synthesis and reduced proliferation. Metabolomic analysis indicated that MB-induced SO production partially reversed the Warburg effect, suggesting a shift from glycolysis to oxidative phosphorylation. These effects were less pronounced in OV1369-R2 and ARPE-19 cells, correlating with their lower MB sensitivity. Conclusions: MB-generated SO selectively modulates mitochondrial energetics in ovarian cancer cells, driving a metabolic reorganization that curtails their proliferative capacity. This approach, leveraging the bacterial-like features of cancer metabolism, offers a promising therapeutic avenue to induce apoptosis and enhance treatment outcomes in ovarian cancer.

In Vitro Methylene Blue and Carboplatin Combination Triggers Ovarian Cancer Cells Death

Ovarian cancer presents a dire prognosis and high mortality rates, necessitating the exploration of alternative therapeutic avenues, particularly in the face of platinum-based chemotherapy resistance. Conventional treatments often overlook the metabolic implications of cancer, but recent research has highlighted the pivotal role of mitochondria in cancer pathogenesis and drug resistance. This study delves into the metabolic landscape of ovarian cancer treatment, focusing on modulating mitochondrial activity using methylene blue (MB). Investigating two epithelial ovarian cancer (EOC) cell lines, OV1369-R2 and OV1946, exhibiting disparate responses to carboplatin, we sought to identify metabolic nodes, especially those linked to mitochondrial dysfunction, contributing to chemo-resistance. Utilizing ARPE-19, a normal retinal epithelial cell line, as a control model, our study reveals MB's distinct cellular uptake, with ARPE-19 absorbing 5 to 7 times more MB than OV1946 and OV1369-R2. Treatment with 50 µM MB (MB-50) effectively curtailed the proliferation of both ovarian cancer cell lines. Furthermore, MB-50 exhibited the ability to quell glutaminolysis and the Warburg effect in cancer cell cultures. Regarding mitochondrial energetics, MB-50 spurred oxygen consumption, disrupted glycolytic pathways, and induced ATP depletion in the chemo-sensitive OV1946 cell line. These findings highlight the potential of long-term MB exposure as a strategy to improve the chemotherapeutic response in ovarian cancer cells. The ability of MB to stimulate oxygen consumption and enhance mitochondrial activity positions it as a promising candidate for ovarian cancer therapy, shedding light on the metabolic pressures exerted on mitochondria and their modulation by MB, thus contributing to a deeper understanding of mitochondrial dysregulation and the metabolic underpinnings of cancer cell proliferation.

Uracil- and Pyridine-Containing HDAC Inhibitors Displayed Cytotoxicity in Colorectal and Glioblastoma Cancer Stem Cells

Cancer stem cells (CSCs) are a niche of highly tumorigenic cells featuring self-renewal, activation of pluripotency genes, multidrug resistance, and ability to cause cancer relapse. Seven HDACi (1-7), showing either hydroxamate or 2'-aminoanilide function, were tested in colorectal cancer (CRC) and glioblastoma multiforme (GBM) CSCs to determine their effects on cell proliferation, H3 acetylation levels and in-cell HDAC activity. Two uracil-based hydroxamates, 5 and 6, which differ in substitution at C5 and C6 positions of the pyrimidine ring, exhibited the greatest cytotoxicity in GBM (5) and CRC (6) CSCs, followed by the pyridine-hydroxamate 2, with 2- to 6-fold higher potency than the positive control SAHA. Finally, increased H3 acetylation as well as HDAC inhibition directly in cells by selected 2'-aminoanilide 4 and hydroxamate 5 confirmed target engagement. Further investigation will be conducted into the broad-spectrum anticancer properties of the most potent derivatives and their effects in combination with approved, conventional anticancer drugs.

Changes in chromatin accessibility and transcriptional landscape induced by HDAC inhibitors in TP53 mutated patient-derived colon cancer organoids

Here we present the generation and characterization of patient-derived organoids (PDOs) from colorectal cancer patients. PDOs derived from two patients with TP53 mutations were tested with two different HDAC inhibitors (SAHA and NKL54). Cell death induction, transcriptome, and chromatin accessibility changes were analyzed. HDACIs promote the upregulation of low expressed genes and the downregulation of highly expressed genes. A similar differential effect is observed at the level of chromatin accessibility. Only SAHA is a potent inducer of cell death, which is characterized by the upregulation of BH3-only genes BIK and BMF. Up-regulation of BIK is associated with increased accessibility in an intronic region that has enhancer properties. SAHA, but not NKL54, also causes downregulation of BCL2L1 and decreases chromatin accessibility in three distinct regions of the BCL2L1 locus. Both inhibitors upregulate the expression of innate immunity genes and members of the MHC family. In summary, our exploratory study indicates a mechanism of action for SAHA and demonstrate the low efficacy of NKL54 as a single agent for apoptosis induction, using two PDOs. These observations need to be validated in a larger cohort of PDOs.

Methylene Blue Metabolic Therapy Restrains In Vivo Ovarian Tumor Growth

Ovarian cancer remains a significant challenge, especially in platinum-resistant cases where treatment options are limited. In this study, we investigated the potential of methylene blue (MB) as a metabolic therapy and complementary treatment approach for ovarian cancer. Our findings demonstrated a significant in vivo reduction in the proliferation of TOV112D-based ovarian-cell-line xenografts. In this preclinical study, which used a carboplatin-resistant ovarian cancer tumor model implanted into mice, MB-mediated metabolic therapy exhibited superior tumor slowdown compared to carboplatin treatment alone. This indicates, for the first time, MB's potential as an alternative or adjuvant treatment, especially for resistant cases. Our in vitro study on TOV112D and ARPE-19 sheds light on the impact of such an MB-based metabolic therapy on mitochondrial energetics (respiration and membrane potential). MB showed a modulatory role in the oxygen consumption rate and the mitochondrial membrane potential. These results revealed, for the first time, that MB specifically targets TOV112D mitochondria and probably induces cell apoptosis. The differential response of normal (ARPE-19) and cancer (TOV112D) cells to the MB treatment suggests potential alterations in cancer cell mitochondria, opening avenues for therapeutic approaches that target the mitochondria. Overall, our findings suggest the efficacy of MB as a possible treatment for ovarian cancer and provide valuable insights into the mechanisms underlying the efficacy of methylene blue metabolic therapy in ovarian cancer treatment.

Tumor microenvironment-induced tumor cell plasticity: relationship with hypoxic stress and impact on tumor resistance

The role of tumor interaction with stromal components during carcinogenesis is crucial for the design of efficient cancer treatment approaches. It is widely admitted that tumor hypoxic stress is associated with tumor aggressiveness and thus impacts susceptibility and resistance to different types of treatments. Notable biological processes that hypoxia functions in include its regulation of tumor heterogeneity and plasticity. While hypoxia has been reported as a major player in tumor survival and dissemination regulation, the significance of hypoxia inducible factors in cancer stem cell development remains poorly understood. Several reports indicate that the emergence of cancer stem cells in addition to their phenotype and function within a hypoxic tumor microenvironment impacts cancer progression. In this respect, evidence showed that cancer stem cells are key elements of intratumoral heterogeneity and more importantly are responsible for tumor relapse and escape to treatments. This paper briefly reviews our current knowledge of the interaction between tumor hypoxic stress and its role in stemness acquisition and maintenance. Our review extensively covers the influence of hypoxia on the formation and maintenance of cancer stem cells and discusses the potential of targeting hypoxia-induced alterations in the expression and function of the so far known stem cell markers in cancer therapy approaches. We believe that a better and integrated understanding of the effect of hypoxia on stemness during carcinogenesis might lead to new strategies for exploiting hypoxia-associated pathways and their targeting in the clinical setting in order to overcome resistance mechanisms. More importantly, at the present time, efforts are oriented towards the design of innovative therapeutical approaches that specifically target cancer stem cells.

Notch receptor/ligand diversity: contribution to colorectal cancer stem cell heterogeneity

Cancer cell heterogeneity is a key contributor to therapeutic failure and post-treatment recurrence. Targeting cell subpopulations responsible for chemoresistance and recurrence seems to be an attractive approach to improve treatment outcome in cancer patients. However, this remains challenging due to the complexity and incomplete characterization of tumor cell subpopulations. The heterogeneity of cells exhibiting stemness-related features, such as self-renewal and chemoresistance, fuels this complexity. Notch signaling is a known regulator of cancer stem cell (CSC) features in colorectal cancer (CRC), though the effects of its heterogenous signaling on CRC cell stemness are only just emerging. In this review, we discuss how Notch ligand-receptor specificity contributes to regulating stemness, self-renewal, chemoresistance and cancer stem cells heterogeneity in CRC.

Tumor-targeted liposomes with platycodin D2 promote apoptosis in colorectal cancer

Conventional chemotherapy for colorectal cancer (CRC), though efficacious, is discouraging due to its limited targeting capability, lack of selectivity, and chemotherapy-associated side effects. With the advent of nanomedicines, a liposomal delivery system making use of a combination of anticancer phytochemicals is fast gaining popularity as one of the most promising nanoplatforms for CRC treatment. Rising evidence supports phytochemicals such as platycosides for their anticancer potency. To this end, a combination therapy including tumor-targeted liposomes along with phytochemicals might have a greater therapeutic potential against cancer. In this study, we developed acidity-triggered rational membrane (ATRAM) along with conjugated platycodin D2 (PCD2) and liposomes (PCD2-Lipo-ATRAM) as a tumor-targeting therapy. The PCD2-Lipo-ATRAM treatment demonstrated a successful tumor-targeting ability in the CRC xenografts, in which PCD2 not only exerted a potent antitumor effect by inducing apoptotic cell death and but also functioned as a liposome membrane stabilizer. Moreover, PCD2-Lipo-ATRAM suppressed antiapoptotic BCL-2 family proteins, resulting in enhanced cytotoxicity toward CRC cells by inducing intrinsic caspase-9/-3 mediated apoptosis. Thus, our data has shown that tumor-targeting PCD2-based liposomal systems represent a promising strategy for CRC therapy, since they directly target the tumors, unlike other therapies that can miss the target.

Prognostic Biomarkers of Cell Proliferation in Colorectal Cancer (CRC): From Immunohistochemistry to Molecular Biology Techniques

Colorectal cancer (CRC) is one of the most common and severe malignancies worldwide. Recent advances in diagnostic methods allow for more accurate identification and detection of several molecular biomarkers associated with this cancer. Nonetheless, non-invasive and effective prognostic and predictive testing in CRC patients remains challenging. Classical prognostic genetic markers comprise mutations in several genes (e.g., APC, KRAS/BRAF, TGF-β, and TP53). Furthermore, CIN and MSI serve as chromosomal markers, while epigenetic markers include CIMP and many other candidates such as SERP, p14, p16, LINE-1, and RASSF1A. The number of proliferation-related long non-coding RNAs (e.g., SNHG1, SNHG6, MALAT-1, CRNDE) and microRNAs (e.g., miR-20a, miR-21, miR-143, miR-145, miR-181a/b) that could serve as potential CRC markers has also steadily increased in recent years. Among the immunohistochemical (IHC) proliferative markers, the prognostic value regarding the patients' overall survival (OS) or disease-free survival (DFS) has been confirmed for thymidylate synthase (TS), cyclin B1, cyclin D1, proliferating cell nuclear antigen (PCNA), and Ki-67. In most cases, the overexpression of these markers in tissues was related to worse OS and DFS. However, slowly proliferating cells should also be considered in CRC therapy (especially radiotherapy) as they could represent a reservoir from which cells are recruited to replenish the rapidly proliferating population in response to cell-damaging factors. Considering the above, the aim of this article is to review the most common proliferative markers assessed using various methods including IHC and selected molecular biology techniques (e.g., qRT-PCR, in situ hybridization, RNA/DNA sequencing, next-generation sequencing) as prognostic and predictive markers in CRC.

Constructing a cancer stem cell related prognostic model for predicting immune landscape and drug sensitivity in colorectal cancer

Background: Colorectal cancer (CRC) ranks the second malignancy with high incidence and mortality worldwide. Cancer stem cells (CSCs) function critically in cancer progression and metastasis via the interplay with immune cells in tumor microenvironment. This study aimed to identify important CSC marker genes and parsed the role of these marker genes in CRC. Materials and methods: CRC samples' single-cell RNA sequencing data and bulk transcriptome data were utilized. Seurat R package annotated CSCs and identified CSC marker genes. Consensus clustering subtyped CRC samples based on CSC marker genes. Immune microenvironment, pathway and oxidative stress analysis was performed using ESTIMATE, MCP-counter analysis and ssGSEA analysis. A prognostic model was established by Lasso and stepAIC. Sensitivity to chemotherapeutic drugs was determined by the biochemical half maximal inhibitory concentration with pRRophetic R package. Results: We identified a total of 29 CSC marker genes related to disease-specific survival (DSS). Two clusters (CSC1 and CSC2) were determined, and CSC2 showed shorter DSS, a larger proportion of late-stage samples, and higher oxidative stress response. Two clusters exhibited differential activation of biological pathways associated with immune response and oncogenic signaling. Drug sensitivity analysis showed that 44 chemotherapy drugs were more sensitive to CSC2 that those in CSC1. We constructed a seven-gene prognostic model (DRD4, DPP7, UCN, INHBA, SFTA2, SYNPO2, and NXPH4) that was effectively to distinguish high-risk and low-risk patients. 14 chemotherapy drugs were more sensitive to high-risk group and 13 chemotherapy drugs were more sensitive to low-risk group. Combination of higher oxidative stress and risk score indicated dismal prognosis. Conclusion: The CSC marker genes we identified may help to further decipher the role of CSCs in CRC development and progression. The seven-gene prognostic model could serve as an indicator for predicting the response to immunotherapy and chemotherapy as well as prognosis of CRC patients.

Mitochondria in colorectal cancer stem cells - a target in drug resistance

Colorectal cancer (CRC) is the third most diagnosed cancer and the second most deadly type of cancer worldwide. In late diagnosis, CRC can resist therapy regimens in which cancer stem cells (CSCs) are intimately related. CSCs are a subpopulation of tumor cells responsible for tumor initiation and maintenance, metastasis, and resistance to conventional treatments. In this scenario, colorectal cancer stem cells (CCSCs) are considered an important key for therapeutic failure and resistance. In its turn, mitochondria is an organelle involved in many mechanisms in cancer, including chemoresistance of cytotoxic drugs due to alterations in mitochondrial metabolism, apoptosis, dynamics, and mitophagy. Therefore, it is crucial to understand the mitochondrial role in CCSCs regarding CRC drug resistance. It has been shown that enhanced anti-apoptotic protein expression, mitophagy rate, and addiction to oxidative phosphorylation are the major strategies developed by CCSCs to avoid drug insults. Thus, new mitochondria-targeted drug approaches must be explored to mitigate CRC chemoresistance via the ablation of CCSCs.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Tumor-associated macrophages promote resistance of hepatocellular carcinoma cells against sorafenib by activating CXCR2 signaling

BACKGROUND

Sorafenib (SOR) is the first line treatment for advanced hepatocellular carcinoma (HCC), but resistance develops frequently. Tumor-associated macrophages (TAMs) have been reported to affect the progression of HCC. We therefore aimed to study the role of TAMs in promoting SOR resistance.

METHODS

Immunofluorescence staining for the M2 marker CD204 and the cancer stem cell (CSC) markers CD44 and CD133 was performed in paired HCC and adjacent noncancerous tissues and HCC tissues stratified by response of SOR treatment. HCC/U937 coculture system and cytokines were used to induce M2 polarization for studying the effects of M2 TAMs on CSC properties and apoptotic death of HCC cells after SOR treatment.

RESULTS

Higher expression of CD204, CD44, and CD133 was observed in patients with SOR nonresponse (SNR) than in those with SOR response (SR), suggesting that SNR is positively correlated to levels of CSCs and M2 TAMs. After coculture, M2 TAMs could increase the level of CSCs but decrease SOR-induced apoptosis. Incubation of HCC cells with coculture conditioned medium increased the formation of spheres that were resistant to SOR. Furthermore, CXCL1 and CXCL2 were found to be the potential paracrine factors released by M2 TAMs to upregulate SOR resistance in HCC cells. Treatment with CXCL1 and CXCL2 could increase HCC CSC activity but decrease SOR-induced apoptosis by affecting BCL-2 family gene expression. Using pharmacological inhibitors, CXCR2/ERK signaling was found to be critical to CXCL1- and CXCL2-mediated SOR resistance.

CONCLUSION

This study identified CXCL1, CXCL2, and their downstream CXCR2/ERK signaling as potential therapeutic targets to overcome SOR resistance in HCC.

Intra‑tumor heterogeneity of cancer stem cell‑related genes and their potential regulatory microRNAs in metastasizing colorectal carcinoma

Intra‑tumor heterogeneity (ITH) is related to cancer progression, therapy resistance and recurrences, and is one of the challenging fields in cancerogenesis research. Cancer stem cells (CSC) are thought to be crucially involved in the pathogenesis of several cancer types, including colorectal carcinoma (CRC), and associated with ITH. In the present study, the expression gradient of four genes related to CSC (L1TD1, SLITRK6, ST6GALNAC1 and TCEA3) and their potential regulatory microRNAs (miRNAs) were investigated in the central part and invasive front of the primary tumor, as well as in lymph node and liver metastases. In total, 63 formalin‑fixed paraffin‑embedded biopsy samples of primary tumor (central part, invasive tumor front), as well as lymph node and liver metastases from 19 patients with CRC, were analyzed. The expression of selected genes (L1TD1, SLITRK6, ST6GALNAC1 and TCEA3) and miRNAs (miR‑199a‑3p, miR‑425‑5p, miR‑1225‑3p, miR‑1233‑3p and miR‑1303) was evaluated using reverse transcription‑quantitative PCR. Significant differences in expression were identified for all investigated genes in lymph node metastasis, but not in the liver metastases. All investigated miRNAs were significantly differentially expressed in lymph node metastasis, and miR‑199a‑3p, miR‑425‑5p and miR‑1233‑3p in liver metastasis. Furthermore, a negative correlation between the expression of miR‑199a‑3p and expression of its potential target gene SLITRK6 was confirmed. The present results provide further evidence that expression of CSC‑related genes and their potential regulatory miRNAs contribute to ITH in CRC, lymph node and liver metastasis. The SLITRK6 gene and its regulatory miRNA miR‑199a‑3p are promising for further validation in functional studies to deepen the present understanding of the regulation of CSC‑related genes in CRC.

Bioinformatics Analysis of RNA-seq Data Reveals Genes Related to Cancer Stem Cells in Colorectal Cancerogenesis

Cancer stem cells (CSC) play one of the crucial roles in the pathogenesis of various cancers, including colorectal cancer (CRC). Although great efforts have been made regarding our understanding of the cancerogenesis of CRC, CSC involvement in CRC development is still poorly understood. Using bioinformatics and RNA-seq data of normal mucosa, colorectal adenoma, and carcinoma (n = 106) from GEO and TCGA, we identified candidate CSC genes and analyzed pathway enrichment analysis (PEI) and protein–protein interaction analysis (PPI). Identified CSC-related genes were validated using qPCR and tissue samples from 47 patients with adenoma, adenoma with early carcinoma, and carcinoma without and with lymph node metastasis and were compared to normal mucosa. Six CSC-related genes were identified: ANLN, CDK1, ECT2, PDGFD, TNC, and TNXB. ANLN, CDK1, ECT2, and TNC were differentially expressed between adenoma and adenoma with early carcinoma. TNC was differentially expressed in CRC without lymph node metastases whereas ANLN, CDK1, and PDGFD were differentially expressed in CRC with lymph node metastases compared to normal mucosa. ANLN and PDGFD were differentially expressed between carcinoma without and with lymph node metastasis. Our study identified and validated CSC-related genes that might be involved in early stages of CRC development (ANLN, CDK1, ECT2, TNC) and in development of metastasis (ANLN, PDGFD).

mRNAsi-related metabolic risk score model identifies poor prognosis, immunoevasive contexture, and low chemotherapy response in colorectal cancer patients through machine learning

Colorectal cancer (CRC) is one of the most fatal cancers of the digestive system. Although cancer stem cells and metabolic reprogramming have an important effect on tumor progression and drug resistance, their combined effect on CRC prognosis remains unclear. Therefore, we generated a 21-gene mRNA stemness index-related metabolic risk score model, which was examined in The Cancer Genome Atlas and Gene Expression Omnibus databases (1323 patients) and validated using the Zhongshan Hospital cohort (200 patients). The high-risk group showed more immune infiltrations; higher levels of immunosuppressive checkpoints, such as CD274, tumor mutation burden, and resistance to chemotherapeutics; potentially better response to immune therapy; worse prognosis; and advanced stage of tumor node metastasis than the low-risk group. The combination of risk score and clinical characteristics was effective in predicting overall survival. Zhongshan cohort validated that high-risk score group correlated with malignant progression, worse prognosis, inferior adjuvant chemotherapy responsiveness of CRC, and shaped an immunoevasive contexture. This tool may provide a more accurate risk stratification in CRC and screening of patients with CRC responsive to immunotherapy.

Depletion of Fibroblast Growth Factor 12 Restrains the Viability, Stemness, and Motility of Colorectal Cancer

Background

Colorectal cancer (CRC) is a leading cause of cancer-related death. CRC patients have a poor prognosis due to tumor metastasis and recurrence. Fibroblast growth factor 12 (FGF12), a member of the FGF family, is highly expressed in several cancers. However, little is known about the roles of FGF12 in CRC progression.

Methods

The overall survival (OS) of CRC patients was detected via Kaplan-Meier analysis. The FGF12 expression in both CRC tissues and cells was analyzed by qRT-PCR, immunohistochemistry (IHC), and western blotting (WB). LoVo and SW480 cells were transfected with shFGF12 lentivirus to silence FGF12. In vivo and in vitro experiments were performed to explore the FGF12 functions in CRC, including CCK-8, Edu, flow cytometry, Transwell, EMT, cancer stemness, and tumor xenograft experiments.

Results

FGF12 was upregulated in both CRC cells and tissues. High expression of FGF12 indicated a shorter OS in CRC patients. FGF12 knockdown inhibited the proliferation, invasion, stemness, and EMT of CRC cells. FGF12 knockdown promoted CRC cell apoptosis in vitro. 740 Y-P (a PI3K/AKT pathway activator) restored the proliferation, stemness, invasion, and EMT in FGF12-deficient cells and reversed LoVo cell apoptosis induced by FGF12 depletion. Depletion of FGF12 inhibited tumor growth, EMT, cancer stemness, and PI3K/AKT pathway in a xenograft mouse model.

Conclusions

FGF12 predicts bad clinical outcome and modulates the viability, stemness, and motility of CRC cells. Our study may provide a new insight for the diagnosis and treatment of CRC.

The Protective Role of 4-Acetylarylquinolinol B in Different Pathological Processes

Antrodia cinnamomea is a traditional plant and a unique fungus native to Taiwan that has been reported to have many biological functions, including anti-inflammatory and anticancer activities. The compound 4-acetylarylquinolinol B (4-AAQB) is one of the main bioactive compounds in the stamens of Antrodia cinnamomea, and has many biological functions, such as anti-inflammatory, antiproliferative, blood sugar reduction, antimetastasis, and vascular tone relaxation. In recent years, the increasing evidences have shown that 4-AAQB is involved in many diseases; however, the relevant mechanisms have not been fully clarified. This review aimed to clarify the improvement by 4-AAQB in different pathological processes, as well as the compound’s molecular mechanisms, in order to provide a theoretical reference for future related research

Endoplasmic Reticulum Stress of Gut Enterocyte and Intestinal Diseases

The endoplasmic reticulum, a vast reticular membranous network from the nuclear envelope to the plasma membrane responsible for the synthesis, maturation, and trafficking of a wide range of proteins, is considerably sensitive to changes in its luminal homeostasis. The loss of ER luminal homeostasis leads to abnormalities referred to as endoplasmic reticulum (ER) stress. Thus, the cell activates an adaptive response known as the unfolded protein response (UPR), a mechanism to stabilize ER homeostasis under severe environmental conditions. ER stress has recently been postulated as a disease research breakthrough due to its significant role in multiple vital cellular functions. This has caused numerous reports that ER stress-induced cell dysfunction has been implicated as an essential contributor to the occurrence and development of many diseases, resulting in them targeting the relief of ER stress. This review aims to outline the multiple molecular mechanisms of ER stress that can elucidate ER as an expansive, membrane-enclosed organelle playing a crucial role in numerous cellular functions with evident changes of several cells encountering ER stress. Alongside, we mainly focused on the therapeutic potential of ER stress inhibition in gastrointestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer. To conclude, we reviewed advanced research and highlighted future treatment strategies of ER stress-associated conditions.

HDAC class I inhibitor domatinostat sensitizes pancreatic cancer to chemotherapy by targeting cancer stem cell compartment via FOXM1 modulation

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) represents an unmet clinical need due to the very poor prognosis and the lack of effective therapy. Here we investigated the potential of domatinostat (4SC-202), a new class I histone deacetylase (HDAC) inhibitor, currently in clinical development, to sensitize PDAC to first line standard gemcitabine (G)/taxol (T) doublet chemotherapy treatment.

METHODS

Synergistic anti-tumor effect of the combined treatment was assessed in PANC1, ASPC1 and PANC28 PDAC cell lines in vitro as well as on tumor spheroids and microtissues, by evaluating combination index (CI), apoptosis, clonogenic capability. The data were confirmed in vivo xenograft models of PANC28 and PANC1 cells in athymic mice. Cancer stem cells (CSC) targeting was studied by mRNA and protein expression of CSC markers, by limiting dilution assay, and by flow cytometric and immunofluorescent evaluation of CSC mitochondrial and cellular oxidative stress. Mechanistic role of forkhead box M1 (FOXM1) and downstream targets was evaluated in FOXM1-overexpressing PDAC cells.

RESULTS

We showed that domatinostat sensitized in vitro and in vivo models of PDAC to chemotherapeutics commonly used in PDAC patients management and particularly to GT doublet, by targeting CSC compartment through the induction of mitochondrial and cellular oxidative stress. Mechanistically, we showed that domatinostat hampers the expression and function of FOXM1, a transcription factor playing a crucial role in stemness, oxidative stress modulation and DNA repair. Domatinostat reduced FOXM1 protein levels by downregulating mRNA expression and inducing proteasome-mediated protein degradation thus preventing nuclear translocation correlated with a reduction of FOXM1 target genes. Furthermore, by overexpressing FOXM1 in PDAC cells we significantly reduced domatinostat-inducing oxidative mitochondrial and cellular stress and abolished GT sensitization, both in adherent and spheroid cells, confirming FOXM1 crucial role in the mechanisms described. Finally, we found a correlation of FOXM1 expression with poor progression free survival in PDAC chemotherapy-treated patients.

CONCLUSIONS

Overall, we suggest a novel therapeutic strategy based on domatinostat to improve efficacy and to overcome resistance of commonly used chemotherapeutics in PDAC that warrant further clinical evaluation.

BCL-XL inhibition induces an FGFR4-mediated rescue response in colorectal cancer

The heterogeneous therapy response observed in colorectal cancer is in part due to cancer stem cells (CSCs) that resist chemotherapeutic insults. The anti-apoptotic protein BCL-XL plays a critical role in protecting CSCs from cell death, where its inhibition with high doses of BH3 mimetics can induce apoptosis. Here, we screen a compound library for synergy with low-dose BCL-XL inhibitor A-1155463 to identify pathways that regulate sensitivity to BCL-XL inhibition and reveal that fibroblast growth factor receptor (FGFR)4 inhibition effectively sensitizes to A-1155463 both in vitro and in vivo. Mechanistically, we identify a rescue response that is activated upon BCL-XL inhibition and leads to rapid FGF2 secretion and subsequent FGFR4-mediated post-translational stabilization of MCL-1. FGFR4 inhibition prevents MCL-1 upregulation and thereby sensitizes CSCs to BCL-XL inhibition. Altogether, our findings suggest a cell transferable induction of a FGF2/FGFR4 rescue response in CRC that is induced upon BCL-XL inhibition and leads to MCL-1 upregulation.

BCL-XL is crucial for progression through the adenoma-to-carcinoma sequence of colorectal cancer

Evasion of apoptosis is a hallmark of cancer, which is frequently mediated by upregulation of the antiapoptotic BCL-2 family proteins. In colorectal cancer (CRC), previous work has highlighted differential antiapoptotic protein dependencies determined by the stage of the disease. While intestinal stem cells (ISCs) require BCL-2 for adenoma outgrowth and survival during transformation, ISC-specific MCL1 deletion results in disturbed intestinal homeostasis, eventually contributing to tumorigenesis. Colon cancer stem cells (CSCs), however, no longer require BCL-2 and depend mainly on BCL-XL for their survival. We therefore hypothesized that a shift in antiapoptotic protein reliance occurs in ISCs as the disease progresses from normal to adenoma to carcinoma. By targeting antiapoptotic proteins with specific BH3 mimetics in organoid models of CRC progression, we found that BCL-2 is essential only during ISC transformation while MCL1 inhibition did not affect adenoma outgrowth. BCL-XL, on the other hand, was crucial for stem cell survival throughout the adenoma-to-carcinoma sequence. Furthermore, we identified that the limited window of BCL-2 reliance is a result of its downregulation by miR-17-5p, a microRNA that is upregulated upon APC-mutation driven transformation. Here we show that BCL-XL inhibition effectively impairs adenoma outgrowth in vivo and enhances the efficacy of chemotherapy. In line with this dependency, expression of BCL-XL, but not BCL-2 or MCL1, directly correlated to the outcome of chemotherapy-treated CRC patients. Our results provide insights to enable the rational use of BH3 mimetics in CRC management, particularly underlining the therapeutic potential of BCL-XL targeting mimetics in both early and late-stage disease.

Metabolic therapy and bioenergetic analysis: The missing piece of the puzzle

BACKGROUND

Aberrant metabolism is recognized as a hallmark of cancer, a pillar necessary for cellular proliferation. Regarding bioenergetics (ATP generation), most cancers display a preference not only toward aerobic glycolysis ("Warburg effect") and glutaminolysis (mitochondrial substrate level-phosphorylation) but also toward other metabolites such as lactate, pyruvate, and fat-derived sources. These secondary metabolites can assist in proliferation but cannot fully cover ATP demands.

SCOPE OF REVIEW

The concept of a static metabolic profile is challenged by instances of heterogeneity and flexibility to meet fuel/anaplerotic demands. Although metabolic therapies are a promising tool to improve therapeutic outcomes, either via pharmacological targets or press-pulse interventions, metabolic plasticity is rarely considered. Lack of bioenergetic analysis in vitro and patient-derived models is hindering translational potential. Here, we review the bioenergetics of cancer and propose a simple analysis of major metabolic pathways, encompassing both affordable and advanced techniques. A comprehensive compendium of Seahorse XF bioenergetic measurements is presented for the first time.

MAJOR CONCLUSIONS

Standardization of principal readouts might help researchers to collect a complete metabolic picture of cancer using the most appropriate methods depending on the sample of interest.

The Targeting of MRE11 or RAD51 Sensitizes Colorectal Cancer Stem Cells to CHK1 Inhibition

Simple Summary

The ATR-CHK1 axis of the DNA damage response is crucial for the survival of most colorectal cancer stem cells (CRC-SCs), but a significant fraction of primary CRC-SCs either is resistant to ATR or CHK1 inhibitors or survives the abrogation of the ATR-CHK1 cascade despite an initial response. Here, we demonstrate that the targeting of RAD51 or MRE11 improves the sensitivity of primary CRC-SCs to the CHK1/2 inhibitor prexasertib by sequentially inducing replication stress, the abrogation of cell cycle checkpoints, and the emergence of mitotic defects. This results in the induction of mitotic catastrophe and CRC-SC killing via a caspase-dependent apoptosis.

Abstract

Cancer stem cells (CSCs) drive not only tumor initiation and expansion, but also therapeutic resistance and tumor relapse. Therefore, CSC eradication is required for effective cancer therapy. In preclinical models, CSCs demonstrated high capability to tolerate even extensive genotoxic stress, including replication stress, because they are endowed with a very robust DNA damage response (DDR). This favors the survival of DNA-damaged CSCs instead of their inhibition via apoptosis or senescence. The DDR represents a unique CSC vulnerability, but the abrogation of the DDR through the inhibition of the ATR-CHK1 axis is effective only against some subtypes of CSCs, and resistance often emerges. Here, we analyzed the impact of druggable DDR players in the response of patient-derived colorectal CSCs (CRC-SCs) to CHK1/2 inhibitor prexasertib, identifying RAD51 and MRE11 as sensitizing targets enhancing prexasertib efficacy. We showed that combined inhibition of RAD51 and CHK1 (via B02+prexasertib) or MRE11 and CHK1 (via mirin+prexasertib) kills CSCs by affecting multiple genoprotective processes. In more detail, these two prexasertib-based regimens promote CSC eradication through a sequential mechanism involving the induction of elevated replication stress in a context in which cell cycle checkpoints usually activated during the replication stress response are abrogated. This leads to uncontrolled proliferation and premature entry into mitosis of replication-stressed cells, followed by the induction of mitotic catastrophe. CRC-SCs subjected to RAD51+CHK1 inhibitors or MRE11+CHK1 inhibitors are eventually eliminated, and CRC-SC tumorspheres inhibited or disaggregated, via a caspase-dependent apoptosis. These results support further clinical development of these prexasertib-based regimens in colorectal cancer patients.

BH3 Mimetic Sensitivity of Colorectal Cancer Cell Lines in Correlation with Molecular Features Identifies Predictors of Response

Colorectal cancer (CRC) is a heterogeneous disease, which in part explains the differential response to chemotherapy observed in the clinic. BH3 mimetics, which target anti-apoptotic BCL-2 family members, have shown potential in the treatment of hematological malignancies and offer promise for the treatment of solid tumors as well. To gain a comprehensive understanding of the response to BH3 mimetics in CRC and the underlying molecular factors predicting sensitivity, we screened a panel of CRC cell lines with four BH3 mimetics targeting distinct anti-apoptotic BCL-2 proteins. Treatment with compounds alone and in combination revealed potent efficacy of combined MCL-1 and BCL-XL inhibition in inducing CRC cell death, irrespective of molecular features. Importantly, expression of the anti-apoptotic protein target of BH3 mimetics on its own did not predict sensitivity. However, the analysis did identify consensus molecular subtype (CMS) specific response patterns, such as higher resistance to single and combined BCL-2 and MCL-1 inhibition in CMS2 cell lines. Furthermore, analysis of mutation status revealed that KRAS mutant cell lines were more resistant to MCL-1 inhibition. Conclusively, we find that CRC cell lines presented with distinct responses to BH3 mimetics that can in part be predicted by their CMS profile and KRAS/BRAF mutations. Overall, almost all CRC lines share sensitivity in the nanomolar range to combined MCL-1 and BCL-XL targeting suggesting that this would be the preferred approach to target these cancers.

Nanog-mediated stem cell properties is critical for MBNL3 associated paclitaxel resistance of ovarian cancer

Paclitaxel (PTX) is the standard first-line treatment of ovarian cancer, but its efficacy is limited by multi-drug resistance. Therefore, it is crucial to identify effective drug targets to facilitate PTX-sensitivity for ovarian cancer treatment. Seventy PTX-administrated ovarian cancer patients were recruited in this study for gene expression and survival rate analyses. Muscleblind-like-3 (MBNL3) gain- and loss-of-function experiments were carried out in ovarian cancer cells (parental and PTX-resistant) and xenograft model. Cancer cell viability, apoptosis, spheroids formation, Nanog gene silencing were examined and conducted to dissect the underlying mechanism of MBNL3-mediated PTX-resistance. High expression of MBNL3 was positively correlated with PTX-resistance and poor prognosis of ovarian cancer. MBNL3 increased cell viability and decreased apoptosis in ovarian stem-like cells, through up-regulating Nanog. This study suggests the MBNL3-Nanog axis is a therapeutic target for the treatment of PTX-resistance in ovarian cancer management.

Identification and Validation of New Cancer Stem Cell-Related Genes and Their Regulatory microRNAs in Colorectal Cancerogenesis

Significant progress has been made in the last decade in our understanding of the pathogenetic mechanisms of colorectal cancer (CRC). Cancer stem cells (CSC) have gained much attention and are now believed to play a crucial role in the pathogenesis of various cancers, including CRC. In the current study, we validated gene expression of four genes related to CSC, L1TD1, SLITRK6, ST6GALNAC1 and TCEA3, identified in a previous bioinformatics analysis. Using bioinformatics, potential miRNA-target gene correlations were prioritized. In total, 70 formalin-fixed paraffin-embedded biopsy samples from 47 patients with adenoma, adenoma with early carcinoma and CRC without and with lymph node metastases were included. The expression of selected genes and microRNAs (miRNAs) was evaluated using quantitative PCR. Differential expression of all investigated genes and four of six prioritized miRNAs (hsa-miR-199a-3p, hsa-miR-335-5p, hsa-miR-425-5p, hsa-miR-1225-3p, hsa-miR-1233-3p and hsa-miR-1303) was found in at least one group of CRC cancerogenesis. L1TD1, SLITRK6, miR-1233-3p and miR-1225-3p were correlated to the level of malignancy. A negative correlation between miR-199a-3p and its predicted target SLITRK6 was observed, showing potential for further experimental validation in CRC. Our results provide further evidence that CSC-related genes and their regulatory miRNAs are involved in CRC development and progression and suggest that some them, particularly miR-199a-3p and its SLITRK6 target gene, are promising for further validation in CRC.

Cell-Permeable Bak BH3 Peptide Induces Chemosensitization of Hematologic Malignant Cells

Hematologic malignancies such as leukemias and lymphomas are among the leading causes of pediatric cancer death worldwide, and although survival rates have improved with conventional treatments, the development of drug-resistant cancer cells may lead to patient relapse and limited possibilities of a cure. Drug-resistant cancer cells in these hematologic neoplasms are induced by overexpression of the antiapoptotic B-cell lymphoma 2 (Bcl-2) protein families, such as Bcl-XL, Bcl-2, and Mcl-1. We have previously shown that peptides from the BH3 domain of the proapoptotic Bax protein that also belongs to the Bcl-2 family may antagonize the antiapoptotic activity of the Bcl-2 family proteins, restore apoptosis, and induce chemosensitization of tumor cells. Furthermore, cell-permeable Bax BH3 peptides also elicit antitumor activity and extend survival in a murine xenograft model of human B non-Hodgkin's lymphoma. However, the activity of the BH3 peptides of the proapoptotic Bak protein of the Bcl-2 family against these hematologic malignant cells requires further characterization. In this study, we report the ability of the cell-permeable Bak BH3 peptide to restore apoptosis and induce chemosensitization of acute lymphoblastic leukemia and non-Hodgkin's lymphoma cell lines, and this event is enhanced with the coadministration of cell-permeable Bax BH3 peptide and represents an attractive approach to improve the patient outcomes with relapsed or refractory hematological malignant cells.

Synergistic antitumor interaction of valproic acid and simvastatin sensitizes prostate cancer to docetaxel by targeting CSCs compartment via YAP inhibition

BACKGROUND

Despite the introduction of several novel therapeutic approaches that improved survival, metastatic castration-resistant prostate cancer (mCRPC) remains an incurable disease. Herein we report the synergistic antitumor interaction between two well-known drugs used for years in clinical practice, the antiepileptic agent with histone deacetylase inhibitory activity valproic acid and the cholesterol lowering agent simvastatin, in mCRPC models.

METHODS

Synergistic anti-tumor effect was assessed on PC3, 22Rv1, DU145, DU145R80, LNCaP prostate cancer cell lines and EPN normal prostate epithelial cells, by calculating combination index (CI), caspase 3/7 activation and colony formation assays as well as on tumor spheroids and microtissues scored with luminescence 3D-cell viability assay. Cancer stem cells (CSC) compartment was studied evaluating specific markers by RT-PCR, western blotting and flow cytometry as well as by limiting dilution assay. Cholesterol content was evaluated by ¹H-NMR. Overexpression of wild-type YAP and constitutively active YAP5SA were obtained by lipofectamine-based transfection and evaluated by immunofluorescence, western blotting and RT-PCR. 22Rv1 R_39 docetaxel resistant cells were selected by stepwise exposure to increasing drug concentrations. In vivo experiments were performed on xenograft models of DU145R80, 22Rv1 parental and docetaxel resistant cells, in athymic mice.

RESULTS

We demonstrated the capacity of the combined approach to target CSC compartment by a novel molecular mechanism based on the inhibition of YAP oncogene via concurrent modulation of mevalonate pathway and AMPK. Because both CSCs and YAP activation have been associated with chemo-resistance, we tested if the combined approach can potentiate docetaxel, a standard of care in mCRCP treatment. Indeed, we demonstrated, both in vitro and in vivo models, the ability of valproic acid/simvastatin combination to sensitize mCRPC cells to docetaxel and to revert docetaxel-resistance, by mevalonate pathway/YAP axis modulation.

CONCLUSION

Overall, mCRPC progression and therapeutic resistance driven by CSCs via YAP, can be tackled by the combined repurposing of two generic and safe drugs, an approach that warrants further clinical development in this disease.

The Roles of Cancer Stem Cells and Therapy Resistance in Colorectal Carcinoma

Cancer stem cells (CSCs) are the main culprits involved in therapy resistance and disease recurrence in colorectal carcinoma (CRC). Results using cell culture, animal models and tissues from patients with CRC suggest the indispensable roles of colorectal CSCs in therapeutic failure. Conventional therapies target proliferating and mature cancer cells, while CSCs are mostly quiescent and poorly differentiated, thereby they can easily survive chemotherapeutic insults. The aberrant activation of Wnt/β-catenin, Notch, Hedgehog, Hippo/YAP (Yes-associated protein) and phosphatidylinositol 3-kinase/protein kinase B facilitates CSCs with excessive self-renewal and therapy resistance property in CRC. CSCs survive the chemo-radiotherapies by escaping therapy mediated DNA damage via altering the cell cycle checkpoints, increasing DNA damage repair capacity and by an efficient scavenging of reactive oxygen species. Furthermore, dysregulations of miRNAs e.g., miR-21, miR-93, miR-203, miR-215, miR-497 etc., modulate the therapeutic sensitivity of colorectal CSCs by regulating growth and survival signalling. In addition, a reversible quiescent G0 state and the re-entering cell cycle capacity of colorectal CSCs can accelerate tumour regeneration after treatment. Moreover, switching to favourable metabolic signatures during a therapeutic regimen will add more complexity in therapeutic outcomes against CSCs. Therapeutic strategies targeting these underlying mechanisms of CSCs' therapy resistance could provide a promising outcome, however, deep understanding and concerted research are necessary to design novel therapies targeting CSCs. To conclude, the understanding of these mechanisms of CSC in CRC could lead to the improved management of patients with CRC.

BCL-2 family deregulation in colorectal cancer: potential for BH3 mimetics in therapy

Apoptosis is a form of programmed cell death that is essential for tissue homeostasis. De-regulation of the balance between proliferation and apoptosis contributes to tumor initiation. Particularly in the colon where apoptosis is a crucial process in intestinal turnover, inhibition of apoptosis facilitates transformation and tumor progression. The BCL-2 family of proteins are key regulators of apoptosis and have been implicated in colorectal cancer (CRC) initiation, progression and resistance to therapy. In this review we outline the current knowledge on the BCL-2 family-regulated intrinsic apoptosis pathway and mechanisms by which it is de-regulated in CRC. We further review BH3 mimetics as a therapeutic opportunity to target this pathway and evaluate their potential for CRC treatment.

Nanostructured toxins for the selective destruction of drug-resistant human CXCR4+ colorectal cancer stem cells

Current therapies fail to eradicate colorectal Cancer Stem Cells (CSCs). One of the proposed reasons for this failure is the selection, by chemotherapy exposure, of resistant cells responsible for tumor recurrence. In this regard, CXCR4 overexpression in tumor associates with resistance and poor prognosis in colorectal cancer (CRC) patients. In this study, the effectiveness of engineered CXCR4-targeted self-assembling toxin nanoparticles has been explored in the selective killing of CXCR4⁺ human colon-CSCs compared to 5-Fluorouracil and Oxaliplatin, both classical CRC chemotherapeutic agents. To assess this, 3D spheroid colon-CSCs cultures directly derived from CRC patients and CRC-CSC spheroid-derived tumor mouse models were developed. In these animal models, nanostructured toxins show highly selective induction of pyroptosis in the absence of apoptosis, thus having a great potential to overcome tumor resistance, since the same tumor models show resistance to chemotherapeutics. Results set the basis for further development of more efficient therapies focused on selective CXCR4⁺ CSCs elimination activating non-apoptotic mechanisms and represent a pre-clinical proof of concept for the use of CSCs-targeted nanostructured toxins as protein drugs for CRC therapy.

Tumor cells hijack enteric glia to activate colon cancer stem cells and stimulate tumorigenesis

BACKGROUND

Colon cancer stem cells (CSCs), considered responsible for tumor initiation and cancer relapse, are constantly exposed to regulatory cues emanating from neighboring cells present in the tumor microenvironment. Among these cells are enteric glial cells (EGCs) that are potent regulators of the epithelium functions in a healthy intestine. However, whether EGCs impact CSC-driven tumorigenesis remains unknown.

METHODS

Impact of human EGC primary cultures or a non-transformed EGC line on CSCs isolated from human primary colon adenocarcinomas or colon cancer cell lines with different p53, MMR system and stemness status was determined using murine xenograft models and 3D co-culture systems. Supernatants of patient-matched human primary colon adenocarcinomas and non-adjacent healthy mucosa were used to mimic tumor versus healthy mucosa secretomes and compare their effects on EGCs.

FINDINGS

Our data show that EGCs stimulate CSC expansion and ability to give rise to tumors via paracrine signaling. Importantly, only EGCs that were pre-activated by tumor epithelial cell-derived soluble factors increased CSC tumorigenicity. Pharmacological inhibition of PGE2 biosynthesis in EGCs or IL-1 knockdown in tumor epithelial cells prevented EGC acquisition of a pro-tumorigenic phenotype. Inhibition of PGE2 receptor EP4 and EGFR in CSCs inhibited the effects of tumor-activated EGCs.

INTERPRETATION

Altogether, our results show that EGCs, once activated by the tumor, acquire a pro-tumorigenic phenotype and stimulate CSC-driven tumorigenesis via a PGE2/EP4/EGFR-dependent pathway.

FUNDING

This work was supported by grants from the French National Cancer Institute, La Ligue contre le Cancer, the 'Région des Pays de la Loire' and the UNC Lineberger Comprehensive Cancer Center.

Linking stemness with colorectal cancer initiation, progression, and therapy

The discovery of cancer stem cells caused a paradigm shift in the concepts of origin and development of colorectal cancer. Several unresolved questions remain in this field though. Are colorectal cancer stem cells the cause or an effect of the disease? How do cancer stem cells assist in colorectal tumor dissemination to distant organs? What are the molecular or environmental factors affecting the roles of these cells in colorectal cancer? Through this review, we investigate the key findings until now and attempt to elucidate the origins, physical properties, microenvironmental niches, as well as the molecular signaling network that support the existence, self-renewal, plasticity, quiescence, and the overall maintenance of cancer stem cells in colorectal cancer. Increasing data show that the cancer stem cells play a crucial role not only in the establishment of the primary colorectal tumor but also in the distant spread of the disease. Hence, we will also look at the mechanisms adopted by cancer stem cells to influence the development of metastasis and evade therapeutic targeting and its role in the overall disease prognosis. Finally, we will illustrate the importance of understanding the biology of these cells to develop improved clinical strategies to tackle colorectal cancer.

Implication for Cancer Stem Cells in Solid Cancer Chemo-Resistance: Promising Therapeutic Strategies Based on the Use of HDAC Inhibitors

Resistance to therapy in patients with solid cancers represents a daunting challenge that must be addressed. Indeed, current strategies are still not effective in the majority of patients; which has resulted in the need for novel therapeutic approaches. Cancer stem cells (CSCs), a subset of tumor cells that possess self-renewal and multilineage differentiation potential, are known to be intrinsically resistant to anticancer treatments. In this review, we analyzed the implications for CSCs in drug resistance and described that multiple alterations in morphogenetic pathways (i.e., Hippo, Wnt, JAK/STAT, TGF-β, Notch, Hedgehog pathways) were suggested to be critical for CSC plasticity. By interrogating The Cancer Genome Atlas (TCGA) datasets, we first analyzed the prevalence of morphogenetic pathways alterations in solid tumors with associated outcomes. Then, by highlighting epigenetic relevance in CSC development and maintenance, we selected histone deacetylase inhibitors (HDACi) as potential agents of interest to target this subpopulation based on the pleiotropic effects exerted specifically on altered morphogenetic pathways. In detail, we highlighted the role of HDACi in solid cancers and, specifically, in the CSC subpopulation and we pointed out some mechanisms by which HDACi are able to overcome drug resistance and to modulate stemness. Although, further clinical and preclinical investigations should be conducted to disclose the unclear mechanisms by which HDACi modulate several signaling pathways in different tumors. To date, several lines of evidence support the testing of novel combinatorial therapeutic strategies based on the combination of drugs commonly used in clinical practice and HDACi to improve therapeutic efficacy in solid cancer patients.

Stemness underpinning all steps of human colorectal cancer defines the core of effective therapeutic strategies

BACKGROUND

Despite their lethality and ensuing clinical and therapeutic relevance, circulating tumor cells (CTCs) from colorectal carcinoma (CRC) remain elusive, poorly characterized biological entities.

METHODS AND FINDINGS

We perfected a cell system of stable, primary lines from human CRC showing that they possess the full complement of ex- and in-vivo, in xenogeneic models, characteristics of CRC stem cells (CCSCs). Here we show how tumor-initiating, CCSCs cells can establish faithful orthotopic phenocopies of the original disease, which contain cells that spread into the circulatory system. While in the vascular bed, these cells retain stemness, thus qualifying as circulating CCSCs (cCCSCs). This is followed by the establishment of lesions in distant organs, which also contain resident metastatic CCSCs (mCCSCs).

INTERPRETATION

Our results support the concept that throughout all the stages of CRC, stemness is retained as a continuous property by some of their tumor cells. Importantly, we describe a useful standardized model that can enable isolation and stable perpetuation of human CRC's CCSCs, cCCSCs and mCCSCs, providing a useful platform for studies of CRC initiation and progression that is suitable for the discovery of reliable stage-specific biomarkers and the refinement of new patient-tailored therapies. FUND: This work was financially supported by grants from "Ministero della Salute Italiano"(GR-2011-02351534, RC1703IC36 and RC1803IC35) to Elena Binda and from "Associazione Italiana Cancro" (IG-14368) Angelo L. Vescovi. None of the above funders have any role in study design, data collection, data analysis, interpretation, writing the project.

Roles of mitochondria in liver cancer stem cells

Primary liver cancer (PLC) is heterogeneous and it is an aggressive malignancy with a poor prognostic outcome. Current evidence suggests that PLC tumorigenesis is driven by rare subpopulations of cancer stem cells (CSCs), which contribute to tumor initiation, progression, and therapy resistance through particular molecular mechanisms. Energy metabolism and mitochondrial function play an important role in the regulation of cancer stemness and stem cell specifications. Since the role of mitochondrial function as central hubs in cell growth and survival, studies on the critical physiological mechanisms of the liver underlying their therapy-resistant phenotype is important. In this review, we focus on liver CSC-related mitochondrial metabolism that contributes to the liver CSC features, in terms of enhanced drug-resistance and increased tumorigenicity, and to discuss their roles on potential therapies windows for PLC therapies.

Mitochondria P-glycoprotein confers paclitaxel resistance on ovarian cancer cells

Background: Subcellular expression of P-glycoprotein (P-gp) may play an essential role in multidrug resistance (MDR) in many cancers. However, the mitochondria expression and functional activity of P-gp in ovarian cancer are still unclear. In this study, we isolated mitochondria from A2780 cell line and its paclitaxel-resistant subline A2780T and investigated the expression and function of mitochondria P-gp. Methods: Immunocytochemistry was used to evaluate P-gp expression and subcellular localization in cancer cells. Immunofluorescence and laser confocal microscopy were used to detect the co-localization of P-gp and mitochondria both in ovarian cancer tissues and in cell lines. Western blotting (WB), transmission electron microscopy and JC-1 kit were used to evaluate the purity, integrity and activity of the isolated mitochondria. P-gp expression in the whole cell and the isolated mitochondria was evaluated by WB. Flow cytometry was used to evaluate the efflux function of mitochondria P-gp. Results: P-gp expression was detected at the membrane, cytoplasm and nuclei of the A2780T cells, but not in the A2780 cells. Co-localization of P-gp and mitochondria was observed in the A2780T cell line and ovarian cancer tissues, but not in A2780 cells. The purity, integration and activity of the isolated mitochondria are high. P-gp was highly expressed in the A2780T cells and the isolated mitochondria, but was not found in A2780 cells. Rho123 efflux rate was significantly increased in isolated A2780T mitochondria compared to those in A2780 (43.2% vs 9.6%), but it was partly reversed by cyclosporin A (CsA, a P-gp inhibitor). Conclusion: P-gp is highly expressed in mitochondria of taxol-resistant ovarian cancer cells and ovarian cancer tissues and mediates the drug efflux, which probably protect cancer cells from chemotherapy.

Mesenchymal Stem Cells and Cancer: Clinical Challenges and Opportunities

Stem cell-based therapies exhibit profound therapeutic potential for treating various human diseases, including cancer. Among the cell types that can be used for this purpose, mesenchymal stem cells (MSCs) are considered as promising source of stem cells in personalized cell-based therapies. The inherent tumor-tropic property of MSCs can be used to target cancer cells. Although the impacts of MSCs on tumor progression remain elusive, they have been genetically modified or engineered as targeted anticancer agents which could inhibit tumor growth by blocking different processes of tumor. In addition, there are close interactions between MSCs and cancer stem cells (CSCs). MSCs can regulate the growth of CSCs through paracrine mechanisms. This review aims to focus on the current knowledge about MSCs-based tumor therapies, the opportunities and challenges, as well as the prospective of its further clinical implications.

Stem cells in homeostasis and cancer of the gut

The intestinal epithelial lining is one of the most rapidly renewing cell populations in the body. As a result, the gut has been an attractive model to resolve key mechanisms in epithelial homeostasis. In particular the role of intestinal stem cells (ISCs) in the renewal process has been intensely studied. Interestingly, as opposed to the traditional stem cell theory, the ISC is not a static population but displays significant plasticity and in situations of tissue regeneration more differentiated cells can revert back to a stem cell state upon exposure to extracellular signals. Importantly, normal intestinal homeostasis provides important insight into mechanisms that drive colorectal cancer (CRC) development and growth. Specifically, the dynamics of cancer stem cells bear important resemblance to ISC functionality. In this review we present an overview of the current knowledge on ISCs in homeostasis and their role in malignant transformation. Also, we discuss the existence of stem cells in intestinal adenomas and CRC and how these cells contribute to (pre-)malignant growth. Furthermore, we will focus on new paradigms in the field of dynamical cellular hierarchies in CRC and the intimate relationship between tumor cells and their niche.

MEK5/ERK5 activation regulates colon cancer stem-like cell properties

Colon cancer has been proposed to be sustained by a small subpopulation of stem-like cells with unique properties allowing them to survive conventional therapies and drive tumor recurrence. Identification of targetable signaling pathways contributing to malignant stem-like cell maintenance may therefore translate into new therapeutic strategies to overcome drug resistance. Here we demonstrated that MEK5/ERK5 signaling activation is associated with stem-like malignant phenotypes. Conversely, using a panel of cell line-derived three-dimensional models, we showed that ERK5 inhibition markedly suppresses the molecular and functional features of colon cancer stem-like cells. Particularly, pharmacological inhibition of ERK5 using XMD8-92 reduced the rate of primary and secondary sphere formation, the expression of pluripotency transcription factors SOX2, NANOG, and OCT4, and the proportion of tumor cells with increased ALDH activity. Notably, this was further associated with increased sensitivity to 5-fluorouracil-based chemotherapy. Mechanistically, ERK5 inhibition resulted in decreased IL-8 expression and NF-κB transcriptional activity, suggesting a possible ERK5/NF-κB/IL-8 signaling axis regulating stem-like cell malignancy. Taken together, our results provide proof of principle that ERK5-targeted inhibition may be a promising therapeutic approach to eliminate drug-resistant cancer stem-like cells and improve colon cancer treatment.

Selective BCL-XL inhibition promotes apoptosis in combination with MLN8237 in medulloblastoma and pediatric glioblastoma cells

Background

CNS tumors, including medulloblastoma and pediatric glioblastoma (pGBM) account for the majority of solid pediatric malignancies. There remains an unmet need to identify novel treatment approaches in poor prognosis and relapsed pediatric brain tumors, where therapeutic options are limited. Small-molecule B-cell lymphoma 2 (BCL-2) family inhibitors may enhance tumor cell killing when combined with conventional and targeted chemotherapeutic agents. We investigated the effect of disrupting BCL-2 and B cell lymphoma-extra large (BCL-XL) protein function using ABT-263, ABT-199 and WEHI-539 in medulloblastoma and pGBM cells following treatment with MLN8237, an Aurora kinase inhibitor under investigation as a novel agent for the treatment of malignant brain tumors.

Methods

Tumor cell growth and viability were determined by MTT/WST-1 assays and flow cytometry. Effects on cell phenotype, cell cycle progression, and ploidy were determined by live cell imaging and DNA content analysis. Apoptosis was determined by annexin V/propidium iodide staining and time-lapse microscopy and confirmed by measuring caspase-3/7 activity and western blotting and by short interfering RNA (siRNA) knockdown of BCL-2 associated X protein/BCL-2 antagonist killer (BAX/BAK).

Results

ABT-263, in combination with MLN8237, reduced mitotic slippage and polyploidy and promoted the elimination of mitotically defective cells via a BAX/BAK-dependent, caspase-mediated apoptotic pathway. The BCL-XL antagonist, WEHI-539, significantly augmented tumor cell killing when used in combination with MLN8237, as well as sensitized resistant brain tumor cells to a novel BAX activator, SMBA1. In addition, siRNA-mediated knockdown of BCL-XL sensitized pGBM and medulloblastoma cells to MLN8237 and mimicked the effect of combination drug treatment.

Conclusion

Selective small-molecule inhibitors of BCL-XL may enhance the efficacy of MLN8237 and other targeted chemotherapeutic agents.

Discovery of a small-molecule inhibitor of specific serine residue BAD phosphorylation

Human BCL-2-associated death promoter (hBAD) is an apoptosis-regulatory protein mediating survival signals to carcinoma cells upon phosphorylation of Ser99, among other residues. Herein, we screened multiple small-molecule databases queried in a Laplacian-modified naive Bayesian-based cheminformatics platform and identified a Petasis reaction product as a site-specific inhibitor for hBAD phosphorylation. Based on apoptotic efficacy against mammary carcinoma cells, N-cyclopentyl-3-((4-(2,3-dichlorophenyl) piperazin-1-yl) (2-hydroxyphenyl) methyl) benzamide (NPB) was identified as a potential lead compound. In vitro biochemical analyses demonstrated that NPB inhibited the phosphorylation of hBAD specifically on Ser99. NPB was observed to exert this effect independently of AKT and other kinase activities despite the demonstration of AKT-mediated BAD-Ser99 phosphorylation. Using a structure-based bioinformatics platform, we observed that NPB exhibited predicted interactions with hBAD in silico and verified the same by direct binding kinetics. NPB reduced phosphorylation of BAD-Ser99 and enhanced caspase 3/7 activity with associated loss of cell viability in various human cancer cell lines derived from mammary, endometrial, ovarian, hepatocellular, colon, prostatic, and pancreatic carcinoma. Furthermore, by use of a xenograft model, it was observed that NPB, as a single agent, markedly diminished BAD phosphorylation in tumor tissue and significantly inhibited tumor growth. Similar doses of NPB utilized in acute toxicity studies in mice did not exhibit significant effects. Hence, we report a site-specific inhibitor of BAD phosphorylation with efficacy in tumor models.

BH3 mimetics induce apoptosis independent of DRP-1 in melanoma

Despite the recent advancement in treating melanoma, options are still limited for patients without BRAF mutations or in relapse from current treatments. BH3 mimetics against members of the BCL-2 family have gained excitement with the recent success in hematological malignancies. However, single drug BH3 mimetic therapy in melanoma has limited effectiveness due to escape by the anti-apoptotic protein MCL-1 and/or survival of melanoma-initiating cells (MICs). We tested the efficacy of the BH3 mimetic combination of A-1210477 (an MCL-1 inhibitor) and ABT-263 (a BCL-2/BCL-XL/BCL-W inhibitor) in killing melanoma, especially MICs. We also sought to better define Dynamin-Related Protein 1 (DRP-1)'s role in melanoma; DRP-1 is known to interact with members of the BCL-2 family and is a possible therapeutic target for melanoma treatment. We used multiple assays (cell viability, apoptosis, bright field, immunoblot, and sphere formation), as well as the CRISPR/Cas9 genome-editing techniques. For clinical relevance, we employed patient samples of different mutation status, including some relapsed from current treatments such as anti-PD-1 immunotherapy. We found the BH3 mimetic combination kill both the MICs and non-MICs (bulk of melanoma) in all cell lines and patient samples irrespective of the mutation status or relapsed state (p < 0.05). Unexpectedly, the major pro-apoptotic proteins, NOXA and BIM, are not necessary for the combination-induced cell death. Furthermore, the combination impedes the activation of DRP-1, and inhibition of DRP-1 further enhances apoptosis (p < 0.05). DRP-1 effects in melanoma differ from those seen in other cancer cells. These results provide new insights into BCL-2 family's regulation of the apoptotic pathway in melanoma, and suggest that inhibiting the major anti-apoptotic proteins is sufficient to induce cell death even without involvement from major pro-apoptotic proteins. Importantly, our study also indicates that DRP-1 inhibition is a promising adjuvant for BH3 mimetics in melanoma treatment.

Two novel SHP-1 agonists, SC-43 and SC-78, are more potent than regorafenib in suppressing the in vitro stemness of human colorectal cancer cells

Signal transducer and activator of transcription 3 (STAT3) has been shown to play a critical role in the maintenance of cancer stem cells (CSCs). Hence, the inhibition of STAT3 signaling has been suggested to be a viable therapeutic approach for cancers. Moreover, the efficacy of combinations of chemotherapeutic drugs and napabucasin, a small-molecule STAT3 inhibitor, have been assessed in various clinical trials, including those involving patients with metastatic colorectal cancer (CRC).

Two recently developed small-molecule STAT3 inhibitors, SC-43 and SC-78, which can stimulate SHP-1 to inactivate STAT3, were found to have anti-tumor activity. In this study, the inhibitory effects of SC-43, SC-78, and regorafenib (a reference drug) on cell viability, STAT3 phosphorylation, and various stemness properties [e.g., sphere-forming and soft agar colony-forming abilities, CD133⁺/CD44⁺ (stem cell-like) subpopulations, and the expression of several CSC markers] were examined for both HCT-116 and HT-29 human CRC cells. We found that SC-43 and SC-78 but not regorafenib inhibited constitutive and IL-6-induced STAT3 phosphorylation in HCT-116 and HT-29 cells, respectively. Moreover, SC-43 and SC-78 were more potent than regorafenib in suppressing the stemness properties (except stem cell-like subpopulations) of these cells. As expected, SHP-1 knockdown almost completely abolished the suppressive effects of SC-43 and SC-78 on the sphere formation in both cell lines. Furthermore, SC-43 and SC-78 showed synergistic inhibitory effects with oxaliplatin and/or irinotecan on sphere formation. Overall, our results suggest that SC-43 and SC-78 are potent STAT3 inhibitors that may potentially be used in combination therapy for CRC.