In vitro and in vivo characterization of stem-like cells from canine osteosarcoma and assessment of drug sensitivity

Chemokine signaling in tumors: potential role of CXC chemokines and their receptors as glioblastoma therapeutic targets

INTRODUCTION

Glioblastoma is the most aggressive brain tumor, typically associated with poor prognosis. Its treatment is challenging due to the peculiar glioblastoma cell biology and its microenvironment complexity. Specifically, a small fraction of glioma stem cells within the tumor mass drives tumor growth and invasiveness by hijacking brain resident and immune cells. This process also involves modification of extracellular matrix components, such as collagen and glycoproteins, where the secretion of soluble mediators, particularly CXC chemokines, plays a significant role.

AREAS COVERED

We analyze the critical role of chemokines in glioblastoma tumorigenesis, proliferation, angiogenesis, tumor progression, and brain parenchyma invasiveness. Recent evidence highlights how chemokines and their receptors impact glioblastoma biology and represent potential therapeutic targets. Several studies show that chemokines modulate glioblastoma development by acting on glioma stem cell proliferation and self-renewal, promoting vasculogenic mimicry, and altering the extracellular matrix to facilitate tumor invasiveness.

EXPERT OPINION

There is clear evidence supporting CXC receptors (such as CXCR1, 2, 3, 4, and ACKR3/CXCR7) and their signaling pathways as promising pharmacological targets. This in-depth review of chemokine roles in glioblastoma development provides a critical evaluation of the possible clinical translation of innovative compounds targeting these ligand/receptor systems, leading to improved therapeutic outcomes for glioblastoma patients.

Synergistic anticancer effects of doxorubicin and metformin combination therapy: A systematic review

INTRODUCTION

Doxorubicin (DOX) a chemotherapy drug often leads to the development of resistance, in cancer cells after prolonged treatment. Recent studies have suggested that using metformin plus doxorubicin could result in synergic effects. This study focuses on exploring the co-treat treatment of doxorubicin and metformin for various cancers.

METHOD

Following the PRISMA guidelines we conducted a literature search using different databases such as Embase, Scopus, Web of Sciences, PubMed, Science Direct and Google Scholar until July 2023. We selected search terms based on the objectives of this study. After screening a total of 30 articles were included.

RESULTS

The combination of doxorubicin and metformin demonstrated robust anticancer effects, surpassing the outcomes of monotherapy drug treatment. In vitro experiments consistently demonstrated inhibition of cancer cell growth and increased rates of cell death. Animal studies confirmed substantial reductions in tumor growth and improved survival rates, emphasizing the synergistic impact of the combined therapy. The research' discoveries collectively emphasize the capability of the co-treat doxorubicin-metformin as a compelling approach in cancer treatment, highlighting its potential to address medicate resistance and upgrade generally helpful results.

CONCLUSION

The findings of this study show that the combined treatment regimen including doxorubicin and metformin has significant promise in fighting cancer. The observed synergistic effects suggest that this combination therapy could be valuable, in a setting. This study highlights the need for clinical research to validate and enhance the application of the doxorubicin metformin regimen.

Alantolactone enhances the sensitivity of melanoma to MAPK pathway inhibitors by targeting inhibition of STAT3 activation and down-regulating stem cell markers

Mitogen-activated protein kinase inhibitors (MAPKi) were the first line drugs for advanced melanoma patients with BRAF mutation. Targeted therapies have significant therapeutic effects; however, drug resistance hinders their long-term efficacy. Therefore, the development of new therapeutic strategies against MAPKi resistance is critical. Our previous results showed that MAPKi promote feedback activation of STAT3 signaling in BRAF-mutated cancer cells. Studies have shown that alantolactone inhibited the activation of STAT3 in a variety of tumor cells. Our results confirmed that alantolactone suppressed cell proliferation and promoted apoptosis by inhibiting STAT3 feedback activation induced by MAPKi and downregulating the expression of downstream Oct4 and Sox2. The inhibitory effect of alantolactone combined with a MAPKi on melanoma cells was significantly stronger than that on normal cells. In vivo and in vitro experiments showed that combination treatment was effective against drug-resistant melanomas. Our research indicates a potential novel combination therapy (alantolactone and MAPKi) for patients with BRAF-mutated melanoma.

Morphologic, phenotypic, and genotypic similarities between primary tumors and corresponding 3D cell cultures grown in a repeatable system-preliminary results

BACKGROUND

Three-dimensional (3D) cell cultures are the new frontier for reproducing the tumor micro-environment in vitro. The aims of the study were (1) to establish primary 3D cell cultures from canine spontaneous neoplasms and (2) to demonstrate the morphological, phenotypic and genotypic similarities between the primary canine neoplasms and the corresponding 3D cultures, through the expression of tumor differentiation markers.

RESULTS

Seven primary tumors were collected, including 4 carcinomas and 3 soft tissue sarcomas. 3D cell cultures reproduced the morphological features of the primary tumors and showed an overlapping immunophenotype of the primary epithelial tumors. Immunohistochemistry demonstrated the growth of stromal cells and macrophages admixed with the neoplastic epithelial component, reproducing the tumor microenvironment. Mesenchymal 3D cultures reproduced the immunophenotype of the primary tumor completely in 2 out of 3 examined cases while a discordant expression was documented for a single marker in one case. No single nucleotide variants or small indel were detected in TP53 or MDM2 genes, both in primary tumors and in 3D cell cultures specimens. In one sample, MDM2 amplicons were preferentially increased in number compared to TP53 ones, indicating amplification of MDM2, detectable both in the primary tumor and in the corresponding cell culture specimen.

CONCLUSION

Here we demonstrate a good cell morphology, phenotype and genetic profile overlap between primary tumors and the corresponding 3D cultures grown in a repeatable system.

Metformin potentiates immunosuppressant activity and adipogenic differentiation of human umbilical cord-mesenchymal stem cells

Metformin, a first-line drug for type-2 diabetes, displays pleiotropic effects on inflammation, aging, and cancer. Obesity triggers a low-grade chronic inflammation leading to insulin resistance, characterized by increased pro-inflammatory cytokines produced by adipocytes and infiltrated immune cells, which contributes to metabolic syndrome. We investigated metformin's differentiation and immunoregulatory properties of human umbilical cord-mesenchymal stem cells (UC-MSC), as cellular basis of its beneficial role in metabolic dysfunctions. Isolation, characterization and multilineage differentiation of UC-MSC were performed using standard protocols and flow-cytometry. Metformin effects on UC-MSC growth was assessed by colony formation and MTT assay, gene and protein expression by qRT-PCR, and western blot analysis. Proliferation of peripheral blood mononuclear cells (PBMCs) co-cultured with metformin-treated UC-MSC-conditioned media was evaluated by dye dilution assay. We show that metformin decreases proliferation and colony formation of UC-MSCs and enhances their adipogenic lineage commitment. Metformin (3 mM) increases PPARγ and downregulates FABP4 mRNA both in basal and in adipogenic culture conditions; however, the modulation of PPARγ expression is unrelated to the antiproliferative effects. Moreover, metformin inhibits UC-MSC inflammatory activity reducing the expression of IL-6, MCP-1, and COX-2. Conditioned media, collected from metformin-treated UC-MSCs, down-regulate CD3+ T lymphocyte growth in stimulated PBMCs and, in particular, reduce the CD8+ T cell population. These results indicate that metformin may favor new adipocyte formation and potentiate immune suppressive properties of UC-MSCs. Thus, adipose tissue regeneration and anti-inflammatory activity may represent possible mechanisms by which metformin exerts its positive effect on lipid metabolism.

Phenotypic and molecular characterization of novel pulmonary adenocarcinoma cell lines established from a dog

Canine pulmonary adenocarcinoma (PAC) resembles human lung tumors in never-smokers, but it is rarer than human pulmonary adenocarcinoma. Therefore, research on canine PAC is challenging. In the present study, we successfully established various novel canine PAC cell lines from a single lesion in a dog, including two parent cell lines and fourteen cloned cell lines, and characterized their cellular properties in vitro. Several of these cell lines showed epithelial-mesenchymal transition (EMT)-like and/or cancer stem cell (CSCs)-like phenotypes. We additionally assessed the sensitivity of the cells to vinorelbine in vitro. Three clonal lines, two of which showed EMT- and CSC-like phenotypes, were resistant to vinorelbine. Furthermore, we evaluated the expression and activation status of EGFR, HER2, and Ras signaling factors. The findings indicated that the cell lines we established preserved the expression and activation of these factors to varying extents. These novel canine PAC cell lines can be utilized in future research for understanding the pathogenesis and development of treatments for canine PAC.

Development and validation of a GC-MS method for determination of metformin in normal brain and in glioblastoma tissues

Metformin hydrochloride (MH) has recently been repurposed as an anticancer agent, showing antiproliferative activity in vitro and in vivo. In particular, experimental evidence has suggested its potential clinical efficacy in glioblastoma (GBM), a very aggressive tumor frequently characterized by gloomy prognosis. Unfortunately, the published literature concerning experimental applications of MH in glioblastoma animal models report no data on metformin levels reached in the brain, which, considering the high hydrophilicity of the drug, are likely very low. Therefore, new sensitive analytical methods to be applied on biological tissues are necessary to improve our knowledge of MH in vivo biodistribution and biological effects on tumors. In this research work, a GC-MS method for MH quantification in brain tissues is proposed. MH has been derivatized using N-methyl-bis(trifluoroacetamide), as already described in the literature, but the derivatization conditions have been optimized; moreover, deuterated MH has been selected as the best internal standard, after a comparative evaluation including other internal standards employed in published methods. After ascertaining method linearity, its accuracy, precision, specificity, repeatability, LOD and LOQ (0.373 µM and 1.242 µM, respectively, corresponding to 0.887 and 2.958 pmol/mg of wet tissue) have been evaluated on mouse brain tissue samples, obtained through a straightforward preparation procedure involving methanolic extraction from lyophilized brain homogenates and solid phase purification. The method has been validated on brain samples obtained from mice, either healthy or xenografted with GBM cells, receiving metformin dissolved in the drinking water. This analytical method can be usefully applied in preclinical studies aiming at clarifying MH mechanism of action in brain tumors.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Smart delivery of poly-peptide composite for effective cancer therapy

In the past decade, multifunctional peptides have attracted increasing attention in the biomedical field. Peptides possess many impressive advantages, such as high penetration ability, low cost, and etc. However, the short half-life and instability of peptides limit their application. In this study, a poly-peptide drug loading system (called HKMA composite) was designed based on the different functionalities of four peptides. The peptide compositions of HKMA composite from N-terminal to C-terminal were HCBP1, KLA, matrix metalloproteinase-2 (MMP-2)-cleavable peptide and albumin-binding domain. The targeting and lethality of HKMA to NSCLC cell line H460 sphere cells and the half-life of the system were measuredin vivo. The results showed that the HKMA composite had a long half-life and specific killing effect on H460 sphere cellsin vitroandin vivo. Our result proposed smart peptide drug loading system and provided a potential methodology for effective cancer treatment.

An Update on Molecular Pathways Regulating Vasculogenic Mimicry in Human Osteosarcoma and Their Role in Canine Oncology

Canine tumors are valuable comparative models for human counterparts, especially to explore novel biomarkers and to understand pathways and processes involved in metastasis. Vasculogenic mimicry (VM) is a unique property of malignant cancer cells which promote metastasis. Thus, it represents an opportunity to investigate both the molecular mechanisms and the therapeutic targets of a crucial phenotypic malignant switch. Although this biological process has been largely investigated in different human cancer types, including osteosarcoma, it is still largely unknown in veterinary pathology, where it has been mainly explored in canine mammary tumors. The presence of VM in human osteosarcoma is associated with poor clinical outcome, reduced patient survival, and increased risk of metastasis and it shares the main pathways involved in other type of human tumors. This review illustrates the main findings concerning the VM process in human osteosarcoma, search for the related current knowledge in canine pathology and oncology, and potential involvement of multiple pathways in VM formation, in order to provide a basis for future investigations on VM in canine tumors.

Metastasis prognostic factors and cancer stem cell-related transcription factors associated with metastasis induction in canine metastatic mammary gland tumors

Background

Canine mammary gland tumor (MGT) is the most common cancer in aged female dogs. Although it's important to identify reliable metastasis or prognostic factors by evaluating related to cell division, adhesion, and cancer stem cell-related transcription factor (TF) in metastasis-induced canine MGT, but there are limited studies.

Objectives

We aimed to identify metastasis prognostic factors and cancer stem cell-TFs in canine MGTs.

Methods

Age-matched female dogs diagnosed with MGT only were classified into metastatic and non-metastatic groups by histopathological staining of MGT tissues. The mRNA levels of cancer prognostic metastasis molecular factors (E-cadherin, ICAM-1, PRR14, VEGF, HPRT1, RPL4 and hnRNP H) and cancer stem cell-related TFs (Oct4, Sox2, and Nanog) were compared between metastatic and non-metastatic canine MGT tissues using qRT-PCR analysis.

Results

The mRNA levels of ICAM-1, PRR14, VEGF, hnRNP H, Oct4, Sox2, and Nanog in metastatic MGT group were significantly higher than those in non-metastatic MGT group. However, mRNA level of RPL4 was significantly lower in metastatic MGT group. Loss of E-cadherin and HPRT1 was observed in the metastatic MGT group but it was not significant.

Conclusions

Consistent expression patterns of all metastasis-related factors showing elevation in ICAM-1, PRR14, VEGF, hnRNP H, Oct4, Sox2, and Nanog, but decreases in RPL4 levels occurred in canine MGT tissues, which was associated with metastasis. Thus, these cancer prognostic metastasis factors and TFs of cancer stem cells, except for E-cadherin and HPRT1, can be used as reliable metastasis factors for canine MGT and therapeutic strategy.

Sphere-forming cells display stem cell-like characteristics and increased xCT expression in a canine hepatocellular carcinoma cell line

Hepatocellular carcinoma (HCC) is the most common type of canine primary liver tumor; however, most chemotherapies against HCC are ineffective due to resistance to anticancer agents. Sphere-forming cells are considered to act as cancer stem cells for various types of solid tumors and have been established for many canine tumor cell lines, yet no studies have reported sphere-forming cells for canine HCC. In this study, we established sphere-forming cells from a canine HCC cell line (AZACH). These cells displayed increased stem cell marker mRNA expression (Nanog, Sox2, c-Myc, and Klf4), aldehyde dehydrogenase activity, and chemoresistance against mitoxantrone, gemcitabine, and doxorubicin. In addition, sphere-forming cells exhibited higher xCT expression and lower intracellular reactive oxygen species levels than adherent cells. Treatment with sulfasalazine, a xCT-specific inhibitor, reduced sphere formation efficiency. Together, these results indicate that sphere-forming cells derived from a canine HCC cell line have similar characteristics to cancer stem cells and that their increased xCT expression and associated resistance to oxidative stress contribute toward sphere formation.

Apoptosis-related gene expression induced by Colombian propolis samples in canine osteosarcoma cell line

Background and Aim

Osteosarcoma (OSA) is the most common bone tumor in canines and humans. This study aimed to assess the cytotoxic and apoptotic effects of Colombian propolis samples on a canine OSA cell line (OSCA-8) by evaluating the expression of BCL-2, BAX, CASPASE 9, CASPASE 8, and TNFR1 genes involved in the apoptosis pathway.

Materials and Methods

After treating the cells with five Colombian propolis samples (Usm, Met, Fus, Sil, and Caj), we evaluated cell viability and lactate dehydrogenase (LDH) release. Early and late apoptosis was determined by flow cytometry using annexin V/propidium iodide. Furthermore, the effects of three selected samples on gene expression were analyzed by real-time polymerase chain reaction.

Results

The Colombian propolis samples reduced OSCA-8 cell viability and increased LDH release. All samples induced apoptosis significantly and upregulated BCL-2 and CASPASE 8 expression. Usm and Sil increased BAX expression, Met and Sil induced CASPASE 9 expression, and Usm increased TNFR1.

Conclusion

Colombian propolis samples exhibited cytotoxic and apoptotic effects on canine OSA cells, and CASPASE 8 upregulation indicated apoptosis induction by the extrinsic pathway.

Octreotide and Pasireotide Combination Treatment in Somatotroph Tumor Cells: Predominant Role of SST2 in Mediating Ligand Effects

Simple Summary

First-generation somatostatin receptor ligands, such as octreotide, are the first-line medical therapy in acromegaly. Octreotide shows preferential binding for somatostatin receptor subtype 2 (SST₂), while the second-generation ligand, pasireotide, has high affinity for multiple SSTs. We aimed to elucidate whether pasireotide acts via other receptors than SST₂ in somatotroph tumors, and to investigate the potential role of the combination therapy octreotide plus pasireotide. We found that octreotide and pasireotide are superimposable in reducing GH secretion in cultured somatotroph tumor cells, as well as in inhibiting cell proliferation and intracellular pathway activity in rat GH4C1 cells (a model of somatotroph tumors). We did not find any additive/synergistic effect for the combination treatment. Furthermore, we observed that co-incubation with a SST₂-selective antagonist reversed the inhibitory effect of both compounds. Therefore, the two drugs act mainly via SST₂ in somatotroph tumor cells, and their combination is not superior to single agent treatment.

Abstract

First-generation somatostatin receptor ligands (fg-SRLs), such as octreotide (OCT), represent the first-line medical therapy in acromegaly. Fg-SRLs show a preferential binding affinity for somatostatin receptor subtype-2 (SST₂), while the second-generation ligand, pasireotide (PAS), has high affinity for multiple SSTs (SST₅ > SST₂ > SST₃ > SST₁). Whether PAS acts via SST₂ in somatotroph tumors, or through other SSTs (e.g., SST₅), is a matter of debate. In this light, the combined treatment OCT+PAS could result in additive/synergistic effects. We evaluated the efficacy of OCT and PAS (alone and in combination) on growth hormone (GH) secretion in primary cultures from human somatotroph tumors, as well as on cell proliferation, intracellular signaling and receptor trafficking in the rat GH4C1 cell line. The results confirmed the superimposable efficacy of OCT and PAS in reducing GH secretion (primary cultures), cell proliferation, cAMP accumulation and intracellular [Ca²⁺] increase (GH4C1 cells), without any additive effect observed for OCT+PAS. In GH4C1 cells, co-incubation with a SST₂-selective antagonist reversed the inhibitory effect of OCT and PAS on cell proliferation and cAMP accumulation, while both compounds resulted in a robust internalization of SST₂ (but not SST₅). In conclusion, OCT and PAS seem to act mainly through SST₂ in somatotroph tumor cells in vitro, without inducing any additive/synergistic effect when tested in combination.

Tideglusib suppresses stem-cell-like features and progression of osteosarcoma by inhibiting GSK-3β/NOTCH1 signaling

Osteosarcoma is the most common primary bone tumor in children, teenagers and adolescents. Cancer stem cells (CSCs) have the function to self-renew and keep the phenotype of tumor, causing clinical treatment failure. Therefore, developing effective therapies to inhibit osteosarcoma progression is urgently necessary. Glycogen synthase kinase 3β (GSK-3β)is highly expressed in osteosarcoma. In the present study, we made an exploration on the anti-tumor effect of tideglusib (TID), a small-molecule inhibitor of GSK-3β, and revealed the underlying mechanisms. Here, we found that TID markedly reduced the cell viability of different osteosarcoma cell lines. Cell cycle arrest distributed in G2/M was markedly up-regulated in TID-incubated osteosarcoma cells through enhancing p21 expression levels. Apoptosis was evidently induced in osteosarcoma cells via blocking Caspase-3 activation. Consistently, tumor growth was effectively suppressed in an established murine xenograft model with few toxicity and side effects in vivo. Furthermore, TID markedly repressed stem-cell-like activity in osteosarcoma cells through down-regulating NOTCH1 expression. Notably, rescuing NOTCH1 significantly abolished the role of TID in reducing cell proliferation and sarcosphere-formation. Mechanistically, we found that TID-inhibited NOTCH1 expression was associated with the blockage of AKT/GSK-3β signaling pathway. In summary, we for the first time provided evidence that TID could effectively inhibit osteosarcoma progression through repressing cell proliferation, inducing apoptosis, suppressing stem-cell-like properties via down-regulating AKT/GSK-3β/NOTCH1 signaling pathway. Thus, TID may be a promising therapeutic strategy for osteosarcoma treatment without side effects.

Altered glycolysis results in drug-resistant in clinical tumor therapy

Cancer cells undergo metabolic reprogramming, including increased glucose metabolism, fatty acid synthesis and glutamine metabolic rates. These enhancements to three major metabolic pathways are closely associated with glycolysis, which is considered the central component of cancer cell metabolism. Increasing evidence suggests that dysfunctional glycolysis is commonly associated with drug resistance in cancer treatment, and aberrant glycolysis plays a significant role in drug-resistant cancer cells. Studies on the development of drugs targeting these abnormalities have led to improvements in the efficacy of tumor treatment. The present review discusses the changes in glycolysis targets that cause drug resistance in cancer cells, including hexokinase, pyruvate kinase, pyruvate dehydrogenase complex, glucose transporters, and lactate, as well the underlying molecular mechanisms and corresponding novel therapeutic strategies. In addition, the association between increased oxidative phosphorylation and drug resistance is introduced, which is caused by metabolic plasticity. Given that aberrant glycolysis has been identified as a common metabolic feature of drug-resistant tumor cells, targeting glycolysis may be a novel strategy to develop new drugs to benefit patients with drug-resistance.

Doxorubicin treatment modulates chemoresistance and affects the cell cycle in two canine mammary tumour cell lines

BACKGROUND

Doxorubicin (DOX) is widely used in both human and veterinary oncology although the onset of multidrug resistance (MDR) in neoplastic cells often leads to chemotherapy failure. Better understanding of the cellular mechanisms that circumvent chemotherapy efficacy is paramount. The aim of this study was to investigate the response of two canine mammary tumour cell lines, CIPp from a primary tumour and CIPm, from its lymph node metastasis, to exposure to EC50(20h) DOX at 12, 24 and 48 h of treatment. We assessed the uptake and subcellular distribution of DOX, the expression and function of P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP), two important MDR mediators. To better understand this phenomenon the effects of DOX on the cell cycle and Ki67 cell proliferation index and the expression of p53 and telomerase reverse transcriptase (TERT) were also evaluated by immunocytochemistry (ICC).

RESULTS

Both cell lines were able to uptake DOX within the nucleus at 3 h treatment while at 48 h DOX was absent from the intracellular compartment (assessed by fluorescence microscope) in all the surviving cells. CIPm, originated from the metastatic tumour, were more efficient in extruding P-gp substrates. By ICC and qRT-PCR an overall increase in both P-gp and BCRP were observed at 48 h of EC50(20h) DOX treatment in both cell lines and were associated with a striking increase in the percentage of p53 and TERT expressing cells by ICC. The cell proliferation fraction was decreased at 48 h in both cell lines and cell cycle analysis showed a DOX-induced arrest in the S phase for CIPp, while CIPm had an increase in cellular death without arrest. Both cells lines were therefore composed by a fraction of cells sensible to DOX that underwent apoptosis/necrosis.

CONCLUSIONS

DOX administration results in interlinked modifications in the cellular population including a substantial effect on the cell cycle, in particular arrest in the S phase for CIPp and the selection of a subpopulation of neoplastic cells bearing MDR phenotype characterized by P-gp and BCRP expression, TERT activation, p53 accumulation and decrease in the proliferating fraction. Important information is given for understanding the dynamic and mechanisms of the onset of drug resistance in a neoplastic cell population.

The Chemosensitizing Role of Metformin in Anti-Cancer Therapy

Chemoresistance, which leads to the failure of chemotherapy and further tumor recurrence, presents the largest hurdle for the success of anti-cancer therapy. In recent years, metformin, a widely used first-line antidiabetic drug, has attracted increasing attention for its anti-cancer effects. A growing body of evidence indicates that metformin can sensitize tumor responses to different chemotherapeutic drugs, such as hormone modulating drugs, anti-metabolite drugs, antibiotics, and DNA-damaging drugs via selective targeting of Cancer Stem Cells (CSCs), improving the hypoxic microenvironment, and by suppressing tumor metastasis and inflammation. In addition, metformin may regulate metabolic programming, induce apoptosis, reverse Epithelial to Mesenchymal Transition (EMT), and Multidrug Resistance (MDR). In this review, we summarize the chemosensitization effects of metformin and focus primarily on its molecular mechanisms in enhancing the sensitivity of multiple chemotherapeutic drugs, through targeting of mTOR, ERK/P70S6K, NF-κB/HIF-1 α, and Mitogen- Activated Protein Kinase (MAPK) signaling pathways, as well as by down-regulating the expression of CSC genes and Pyruvate Kinase isoenzyme M2 (PKM2). Through a comprehensive understanding of the molecular mechanisms of chemosensitization provided in this review, the rationale for the use of metformin in clinical combination medications can be more systematically and thoroughly explored for wider adoption against numerous cancer types.>.

Identification of the hydantoin alkaloids parazoanthines as novel CXCR4 antagonists by computational and in vitro functional characterization

CXCR4 chemokine receptor represents an attractive pharmacological target due to its key role in cancer metastasis and inflammatory diseases. Starting from our previously-developed pharmacophoric model, we applied a combined computational and experimental approach that led to the identification of the hydantoin alkaloids parazoanthines, isolated from the Mediterranean Sea anemone Parazoanthus axinellae, as novel CXCR4 antagonists. Parazoanthine analogues were then synthesized to evaluate the contribution of functional groups to the overall activity. Within the panel of synthesized natural and non-natural parazoanthines, parazoanthine-B was identified as the most potent CXCR4 antagonist with an IC₅₀ value of 9.3 nM, even though all the investigated compounds were able to antagonize in vitro the down-stream effects of CXC12, albeit with variable potency and efficacy. The results of our study strongly support this class of small molecules as potent CXCR4 antagonists in tumoral pathologies characterized by an overexpression of this receptor. Furthermore, their structure-activity relationships allowed the optimization of our pharmacophoric model, useful for large-scale in silico screening.

Understanding of tumourigenesis in canine mammary tumours based on cancer stem cell research

Mammary tumours occur frequently in female dogs, where such tumours exhibit complexity when examined histologically. These tumours are composed not only of proliferative luminal epithelial cells, but also of myoepithelial cells and/or mesenchymal cells with cartilage and osseous tissues in a solitary mass. The origin of this complexed histogenesis remains speculative, but cancer stem cells (CSCs) are likely involved. CSCs possess self-renewing capacity, differentiation potential, high tumourigenicity in immunodeficient mice, and resistance to chemotherapy and radiation. These cells are at the apex of a hierarchy in cancer tissues and are involved in tumour initiation, recurrence, and metastasis. For these reasons, understanding the properties of CSCs is of paramount importance. Analysis of the characteristics of CSCs may contribute to the elucidation of the histogenesis underlying canine mammary tumours, formulation of novel CSC-targeted therapeutic strategies, and development of biomarkers for early diagnostic and prognostic applications. Here, we review research on CSCs in canine mammary tumours, focusing on: (1) identification and properties of CSCs; (2) hypotheses regarding hierarchal structures in simple type, complex type and mixed tumours of the canine mammary gland; and (3) current and prospective studies of CSC metabolism.

SOX2 Expression in Canine Neoplasia

SOX2 is a major transcriptional regulator of stem cell pluripotency and self-renewability. Its expression in cancer stem cells from several different tumor types in humans and rodent models directly implicates SOX2 in tumorigenicity, metastasis, drug resistance, recurrence, and poor survival. Our objective was to investigate the expression of SOX2 in canine neoplasia. Immunohistochemistry for SOX2 was performed in sets of 10 archived formalin-fixed paraffin-embedded tissues from 45 distinct canine neoplasms. Normal expression of SOX2 was evaluated in a canine tissue microarray. Strong and diffuse SOX2 intranuclear immunolabeling was consistently found in the majority of ectodermal (13/15) and endodermal tumors (5/7). Negative, variable, or inconsistent SOX2 intranuclear immunolabeling was detected in the majority of mesodermal tumors (10/16) and in tumors with dual or uncertain origin (5/7). Although further studies are necessary to understand mechanistically how SOX2 contributes to the biology of each tumor type, this study demonstrates the expression of SOX2 in a wide variety of canine cancers. In the future, screening methods based on cellular plasticity and pluripotency biomarkers may provide avenues for the rational design of therapeutic strategies that target vulnerable signals upstream or downstream of SOX2 in different cancers, and possibly offer novel clinical applications for SOX2 as a prognostic indicator.

Experimental Evidence and Clinical Implications of Pituitary Adenoma Stem Cells

Pituitary adenomas, accounting for 15% of diagnosed intracranial neoplasms, are usually benign and pharmacologically and surgically treatable; however, the critical location, mass effects and hormone hypersecretion sustain their significant morbidity. Approximately 35% of pituitary tumors show a less benign course since they are highly proliferative and invasive, poorly resectable, and likely recurring. The latest WHO classification of pituitary tumors includes pituitary transcription factor assessment to determine adenohypophysis cell lineages and accurate designation of adenomas, nevertheless little is known about molecular and cellular pathways which contribute to pituitary tumorigenesis. In malignant tumors the identification of cancer stem cells radically changed the concepts of both tumorigenesis and pharmacological approaches. Cancer stem cells are defined as a subset of undifferentiated transformed cells from which the bulk of cancer cells populating a tumor mass is generated. These cells are able to self-renew, promoting tumor progression and recurrence of malignant tumors, also conferring cytotoxic drug resistance. On the other hand, the existence of stem cells within benign tumors is still debated. The presence of adult stem cells in human and murine pituitaries where they sustain the high plasticity of hormone-producing cells, allowed the hypothesis that putative tumor stem cells might exist in pituitary adenomas, reinforcing the concept that the cancer stem cell model could also be applied to pituitary tumorigenesis. In the last few years, the isolation and phenotypic characterization of putative pituitary adenoma stem-like cells was performed using a wide and heterogeneous variety of experimental models and techniques, although the role of these cells in adenoma initiation and progression is still not completely definite. The assessment of possible pituitary adenoma-initiating cell population would be of extreme relevance to better understand pituitary tumor biology and to identify novel potential diagnostic markers and pharmacological targets. In this review, we summarize the most updated studies focused on the definition of pituitary adenoma stem cell phenotype and functional features, highlighting the biological processes and intracellular pathways potentially involved in driving tumor growth, relapse, and therapy resistance.

Inhibition of M2-like macrophages by all-trans retinoic acid prevents cancer initiation and stemness in osteosarcoma cells

Emerging evidence indicates that M2-polarized tumor-associated macrophages (TAMs) directly participate in tumor initiation, progression and metastasis. However, to date, few studies have investigated novel strategies for inhibiting TAMs in order to overcome osteosarcoma. In this study, we reported that M2 macrophages were enriched in osteosarcoma tissues from patients, and M2-polarized TAMs enhanced cancer initiation and stemness of osteosarcoma cells, thereby establishing M2-polarized TAMs as a therapeutic target for blocking osteosarcoma formation. We also found that all-trans retinoic acid (ATRA) weakened TAM-induced osteosarcoma tumor formation by inhibiting M2 polarization of TAMs in vivo, and inhibited the colony formation, as well as sphere-formation capacity of osteosarcoma cells promoted by M2-type macrophages in vitro. Furthermore, M2-type macrophages enhanced cancer stem cells (CSCs) properties as assessed by increasing the numbers of CD117⁺Stro-1⁺ cells accompanied by the upregulation of CSC markers (CD133, CXCR4, Nanog, and Oct4), which could clearly be reduced by ATRA. Taken together, the results of this study demonstrated the role of M2-polarized TAMs in osteosarcoma initiation and stemness by activating CSCs, and indicated that ATRA treatment is a promising approach for treating osteosarcoma by preventing M2 polarization of TAMs.

Role of OCT4 in cancer stem-like cells and chemotherapy resistance

Cancer stem-like cells (CSCs) contribute to the tumorigenicity, progression, and chemoresistance of cancers. It is not known whether CSCs arise from normal stem cells or if they arise from differentiated cancer cells by acquiring self-renewal features. These CSCs share stem cell markers that normal stem cells express. There is a rising interest in octamer-binding transcription factor 4 (OCT4), one of the stem cell factors that are essential in embryogenesis and pluripotency. OCT4 is also overexpressed in CSCs of various cancers. Although the majority of the studies in CSCs reported a positive association between the expression of OCT4 and chemoresistance and an inverse correlation between OCT4 and clinical prognosis, there are studies rebuking these findings, possibly due to the sparsity of stem cells within tumors and the heterogeneity of tumors. In addition, post-translational modification of OCT4 affects its activity and warrants further investigation for its association with chemoresistance and prognosis.

Repurposed Biguanide Drugs in Glioblastoma Exert Antiproliferative Effects via the Inhibition of Intracellular Chloride Channel 1 Activity

The lack of in-depth knowledge about the molecular determinants of glioblastoma (GBM) occurrence and progression, combined with few effective and BBB crossing-targeted compounds represents a major challenge for the discovery of novel and efficacious drugs for GBM. Among relevant molecular factors controlling the aggressive behavior of GBM, chloride intracellular channel 1 (CLIC1) represents an emerging prognostic and predictive biomarker, as well as a promising therapeutic target. CLIC1 is a metamorphic protein, co-existing as both soluble cytoplasmic and membrane-associated conformers, with the latter acting as chloride selective ion channel. CLIC1 is involved in several physiological cell functions and its abnormal expression triggers tumor development, favoring tumor cell proliferation, invasion, and metastasis. CLIC1 overexpression is associated with aggressive features of various human solid tumors, including GBM, in which its expression level is correlated with poor prognosis. Moreover, increasing evidence shows that modification of microglia ion channel activity, and CLIC1 in particular, contributes to the development of different neuropathological states and brain tumors. Intriguingly, CLIC1 is constitutively active within cancer stem cells (CSCs), while it seems less relevant for the survival of non-CSC GBM subpopulations and for normal cells. CSCs represent GBM development and progression driving force, being endowed with stem cell-like properties (self-renewal and differentiation), ability to survive therapies, to expand and differentiate, causing tumor recurrence. Downregulation of CLIC1 results in drastic inhibition of GBM CSC proliferation in vitro and in vivo, making the control of the activity this of channel a possible innovative pharmacological target. Recently, drugs belonging to the biguanide class (including metformin) were reported to selectively inhibit CLIC1 activity in CSCs, impairing their viability and invasiveness, but sparing normal stem cells, thus representing potential novel antitumor drugs with a safe toxicological profile. On these premises, we review the most recent insights into the biological role of CLIC1 as a potential selective pharmacological target in GBM. Moreover, we examine old and new drugs able to functionally target CLIC1 activity, discussing the challenges and potential development of CLIC1-targeted therapies.

EPEL promotes the migration and invasion of osteosarcoma cells by upregulating ROCK1

E2F-mediated cell proliferation enhancing long non-coding RNA (lncRNA) (EPEL) is a newly identified lncRNA involved in the regulation of lung cancer cell proliferation. However, its association with other types of cancer is unknown. The present study recruited patients with osteosarcoma and healthy controls. Tumor and adjacent healthy tissues were obtained from patients with osteosarcoma, and whole blood was extracted from patients and healthy controls. The expression levels of EPEL in tissues were detected by reverse transcription-quantitative polymerase chain reaction. The diagnostic value of serum EPEL for osteosarcoma was evaluated by receiver operating characteristic curve analysis. The association between serum levels of EPEL and basic clinical patient information was analyzed by χ² test. Subsequently, EPEL overexpression in osteosarcoma cell lines was established, and its effects on cell migration and invasion were explored by Transwell assay. The implications of EPEL overexpression on Rho-associated coiled-coil containing protein kinase 1 (ROCK1) expression were investigated by western blotting. The results revealed that EPEL was upregulated in tumor tissues compared with adjacent tissues. In addition, serum levels of EPEL were higher in patients with osteosarcoma compared with healthy controls, and were positively associated with distant tumor metastasis. Furthermore, EPEL overexpression promoted the migration and invasion of osteosarcoma cells and induced overexpression of ROCK1. In conclusion, these results suggested that EPEL may promote the migration and invasion of osteosarcoma cells by upregulating ROCK1.

Inhibition of Chloride Intracellular Channel 1 (CLIC1) as Biguanide Class-Effect to Impair Human Glioblastoma Stem Cell Viability

The antidiabetic biguanide metformin exerts antiproliferative effects in different solid tumors. However, during preclinical studies, metformin concentrations required to induce cell growth arrest were invariably within the mM range, thus difficult to translate in a clinical setting. Consequently, the search for more potent metformin derivatives is a current goal for new drug development. Although several cell-specific intracellular mechanisms contribute to the anti-tumor activity of metformin, the inhibition of the chloride intracellular channel 1 activity (CLIC1) at G1/S transition is a key events in metformin antiproliferative effect in glioblastoma stem cells (GSCs). Here we tested several known biguanide-related drugs for the ability to affect glioblastoma (but not normal) stem cell viability, and in particular: phenformin, a withdrawn antidiabetic drug; moroxydine, a former antiviral agent; and proguanil, an antimalarial compound, all of them possessing a linear biguanide structure as metformin; moreover, we evaluated cycloguanil, the active form of proguanil, characterized by a cyclized biguanide moiety. All these drugs caused a significant impairment of GSC proliferation, invasiveness, and self-renewal reaching IC₅₀ values significantly lower than metformin, (range 0.054–0.53 mM vs. 9.4 mM of metformin). All biguanides inhibited CLIC1-mediated ion current, showing the same potency observed in the antiproliferative effects, with the exception of proguanil which was ineffective. These effects were specific for GSCs, since no (or little) cytotoxicity was observed in normal umbilical cord mesenchymal stem cells, whose viability was not affected by metformin and moroxydine, while cycloguanil and phenformin induced toxicity only at much higher concentrations than required to reduce GSC proliferation or invasiveness. Conversely, proguanil was highly cytotoxic also for normal mesenchymal stem cells. In conclusion, the inhibition of CLIC1 activity represents a biguanide class-effect to impair GSC viability, invasiveness, and self-renewal, although dissimilarities among different drugs were observed as far as potency, efficacy and selectivity as CLIC1 inhibitors. Being CLIC1 constitutively active in GSCs, this feature is relevant to grant the molecules with high specificity toward GSCs while sparing normal cells. These results could represent the basis for the development of novel biguanide-structured molecules, characterized by high antitumor efficacy and safe toxicological profile.

Development of an Injectable Slow-Release Metformin Formulation and Evaluation of Its Potential Antitumor Effects

Metformin is an antidiabetic drug which possesses antiproliferative activity in cancer cells when administered at high doses, due to its unfavorable pharmacokinetics. The aim of this work was to develop a pharmacological tool for the release of metformin in proximity of the tumor, allowing high local concentrations, and to demonstrate the in vivo antitumor efficacy after a prolonged metformin exposition. A 1.2% w/w metformin thermoresponsive parenteral formulation based on poloxamers P407 and P124, injectable at room temperature and undergoing a sol-gel transition at body temperature, has been developed and optimized for rheological, thermal and release control properties; the formulation is easily scalable, and proved to be stable during a 1-month storage at 5 °C. Using NOD/SCID mice pseudo-orthotopically grafted with MDA-MB-231/luc⁺ human breast cancer cells, we report that multiple administrations of 100 mg of the optimized metformin formulation close to the tumor site cause tissue accumulation of the drug at levels significantly higher than those observed in plasma, and enough to exert antiproliferative and pro-apoptotic activities. Our results demonstrate that this formulation is endowed with good stability, tolerability, thermal and rheological properties, representing a novel tool to be pursued in further investigations for adjuvant cancer treatment.