Cancer Stem Cells and the Tumor Microenvironment: Targeting the Critical Crosstalk through Nanocarrier Systems

Phenyl boronic acid conjugated lipid nanoparticles for targeted delivery of gamma-secretase inhibitor to breast cancer cells

OBJECTIVE

The major objective of the present study is to develop and evaluate phenyl boronic acid (PBA) conjugated solid lipid nanoparticles (PBA-SUL@SLN) for the targeted delivery of sulindac (SUL) to breast cancer (BC) cells.Significance: Utilizing a dual approach that combines PBA-mediated targeting with Notch-1 pathway inhibition by SUL, the study aims to enhance therapeutic selectivity and efficacy against an aggressive BC subtype, triple negative breast cancer (TNBC), which lacks well defined molecular targets.

METHODS

The PBA-SUL@SLN formulation was prepared using emulsification-solvent evaporation method and analysed for the particle size, zeta potential, entrapment efficiency, and pH sensitive drug release. Cellular uptake studies were conducted to examine selective internalization in TNBC cells. The therapeutic efficacy was assessed by evaluating Notch-1expression modulation of epithelial-to-mesenchymal transition (EMT), cancer stem cell (CSC) activity, and cytotoxic effects in TNBC cell compared to normal cells.

RESULTS

The PBA-SUL@SLN formulation exhibited an optimal particle size of (153.35 nm), a zeta potential of (22.87 mV), and an entrapment efficiency of 83.06%, with preferential drug release observed in the acidic tumor microenvironment. Increased cellular uptake in MDA-MB-231 cells led to notable downregulation of Notch-1, inhibition of epithelial-to-mesenchymal transition (EMT), and potential reduction in CSC activity. Cytotoxicity assays revealed strong and selective efficacy against TNBC cells while causing minimal effects on normal cells.

CONCLUSIONS

The PBA-SUL@SLN formulation presents a promising targeted therapeutic strategy for TNBC, addressing key limitations of existing treatments.

Targeting Triple-Negative Breast Cancer: Resistance Mechanisms and Therapeutic Advancements

BACKGROUND

Triple-negative breast cancer (TNBC) is one of the most heterogeneous and menacing forms of breast cancer, with no sustainable cure available in the current treatment landscape. Its lack of targets makes it highly unresponsive to various treatment modalities, which is why chemotherapy continues to be the primary form of treatment, despite the high rates of patients developing chemoresistance. In recent years, however, there has been significant progress in identifying and understanding the role of several aspects that might contribute to genomic instability and other hallmarks of cancer, including cellular proteins, immune targets, and epigenetic mechanisms, which are desirable as they permit reversibility easier than the often-adamant genetic changes.

METHODS

A literature review was conducted on the role of various TNBC associated biomarkers, their therapeutic applications, and their role in tumorigenesis and tumor maintenance, with a focus on linking both the driving biological mechanisms and emerging treatment options for TNBC.

CONCLUSIONS

Shifting the focus of treatment to identify crucial tumor cell subpopulations and associated biomarkers, such as local immune cell populations and cancer stem cells, could potentially solve or simplify decades' worth of problems that are associated with TNBC, bolstering early detection and the evolution of precision medicine and treatment. The techniques that can be used here are epigenetic analysis and RNA sequencing. Biomarkers, such as PD-L1, survivin, and ABC transporters, are implicated in several crucial processes that maintain tumors, such as cell proliferation, metastasis, immunosuppression, and stemness. Complex treatment options such as, immunotherapy, pathway inhibition, PARP inhibition, virotherapy, and RNA targeting have been considered for TNBC. Phytochemicals are also being considered as a treatment modality for TNBC, as a supplement to chemotherapy and radiation therapy, or as sole treatment.

Cancer stem cells in meningiomas: novel insights and therapeutic implications

Meningiomas (MGs), which arise from meningothelial cells of the dura mater, represent a significant proportion of primary tumours of the central nervous system (CNS). Despite advances in treatment, the management of malignant meningioma (MMG) remains challenging due to diagnostic, surgical, and resection limitations. Cancer stem cells (CSCs), a subpopulation within tumours capable of self-renewal and differentiation, are highlighted as key markers of tumour growth, metastasis, and treatment resistance. Identifying additional CSC-related markers enhances the precision of malignancy evaluations, enabling advancements in personalised medicine. The review discusses key CSC biomarkers that are associated with high levels of expression, aggressive tumour behaviour, and poor outcomes. Recent molecular research has identified CSC-related biomarkers, including Oct-4, Sox2, NANOG, and CD133, which help maintain cellular renewal, proliferation, and drug resistance in MGs. This study highlights new therapeutic strategies that could improve patient prognosis with more durable tumour regression. The use of combination therapies, such as hydroxyurea alongside diltiazem, suggests more efficient and effective MG management compared to monotherapy. Signalling pathways such as NOTCH and hedgehog also offer additional avenues for therapeutic development. CRISPR/Cas9 technology has also been employed to create meningioma models, uncovering pathways related to cell growth and proliferation. Since the efficacy of traditional therapies is limited in most cases due to resistance mechanisms in CSCs, further studies on the biology of CSCs are warranted to develop therapeutic interventions that are likely to be effective in MG. Consequently, improved diagnostic approaches may lead to personalised treatment plans tailored to the specific needs of each patient.

Tumor microenvironment as a target for developing anticancer hydrogels

OBJECTIVE

It has been reported that cancer cells get protected by a complex and rich multicellular environment i.e. the tumor microenvironment (TME) consisting of varying immune cells, endothelial cells, dendritic cells, fibroblasts, etc. This manuscript is aimed at the characteristic features of TME considered as potential target(s) for developing smart anticancer hydrogels.

SIGNIFICANCE

The stimuli-specific drug delivery systems especially hydrogels that can respond to the characteristic features of TME are fabricated for treating cancer. For developing anticancer formulations, TME targeting can be considered an alternative way as it enhances the cytotoxic potential and reduces the unwanted effects. This manuscript shall be of quite interest to academicians, researchers, and clinicians engaged in oncology.

METHODS

The manuscript was prepared by using the data available in the public domain in online resources such as Google Scholar, PubMed, Science Direct, Scopus, Web of Science, Research Gate, etc.

RESULTS

Smart hydrogels, sensitive to some specific features of TME such as low pH, high concentration of glutathione, specific enzymes, etc., are promising anticancer formulations as these improve the efficacy and lower the side effects of chemotherapy.

CONCLUSION

The stimuli-responsive hydrogels have been gaining more attention for delivering cytotoxic drugs to the TME in response to specific stimuli. The stimuli-responsive hydrogels, comprising of cytotoxic drug(s) and specific polymers have some special features such as similarity with biological matrix, ability to respond to various internal as well as external stimuli, improved permeability, porosity, biocompatibility, resemblance with soft living tissues, etc.; and are considered as the promising anticancer candidates.

Methylmalonic acid at the serum level in the elderly contributes to cell growth via mitochondrial dysfunction in colorectal cancer cell spheroids

Methylmalonic acid (MMA) is a small molecule produced during the metabolism of propionate and branched-chain amino acids. Recently, it has been reported that the blood concentration of MMA increases with age and promotes lung cancer metastasis. However, little is known regarding its effects on cancers other than lung cancer. In the present study, we examined the effects of MMA on colorectal cancer cell spheroids. We found that MMA promoted the proliferation of colorectal cancer spheroids at physiological concentrations that can be exhibited by the elderly and induced mitochondrial reactive oxygen species generation, which in turn affected the promotion of cell growth. MMA treatment also induces a metabolic shift in the glycolytic system. These results suggest that MMA may promote cancer cell proliferation by decreasing mitochondrial function, inducing a metabolic shift, and provide new insights into the effects of aging on cancer.

Targeting Cancer Stemness Using Nanotechnology in a Holistic Approach: A Narrative Review

Increasing evidence shows that a very small population of cancer stem cells (CSCs) is responsible for cancer recurrence, drug resistance, and metastasis. CSCs usually reside in hypoxic tumor regions and are characterized by high tumorigenicity. Their inaccessible nature allows them to avoid the effects of conventional treatments such as chemotherapy, radiotherapy, and surgery. In addition, conventional chemo- and radiotherapy is potentially toxic and could help CSCs to spread and survive. New therapeutic targets against CSCs are sought, including different signaling pathways and distinct cell surface markers. Recent advances in nanotechnology have provided hope for the development of new therapeutic avenues to eradicate CSCs. In this review, we present newly discovered nanoparticles that can be co-loaded with an apoptosis-inducing agent or differentiation-inducing agent, with high stability, cellular penetration, and drug release. We also summarize the molecular characteristics of CSCs and the signaling pathways responsible for their survival and maintenance. Controlled drug release targeting CSCs aims to reduce stemness-related drug resistance, suppress tumor growth, and prevent tumor relapse and metastases.

Tumor dormancy and relapse: understanding the molecular mechanisms of cancer recurrence

Cancer recurrence, driven by the phenomenon of tumor dormancy, presents a formidable challenge in oncology. Dormant cancer cells have the ability to evade detection and treatment, leading to relapse. This review emphasizes the urgent need to comprehend tumor dormancy and its implications for cancer recurrence. Despite notable advancements, significant gaps remain in our understanding of the mechanisms underlying dormancy and the lack of reliable biomarkers for predicting relapse. This review provides a comprehensive analysis of the cellular, angiogenic, and immunological aspects of dormancy. It highlights the current therapeutic strategies targeting dormant cells, particularly combination therapies and immunotherapies, which hold promise in preventing relapse. By elucidating these mechanisms and proposing innovative research methodologies, this review aims to deepen our understanding of tumor dormancy, ultimately facilitating the development of more effective strategies for preventing cancer recurrence and improving patient outcomes.

In Vitro models of leukemia development: the role of very small leukemic stem-like cells in the cellular transformation cascade

Recent experimental findings indicate that cancer stem cells originate from transformed very small embryonic-like stem cells. This finding represents an essential advancement in uncovering the processes that drive the onset and progression of cancer. In continuously growing cell lines, for the first time, our team's follow-up research on leukemia, lung cancer, and healthy embryonic kidney cells revealed stages that resembles very small precursor stem cells. This review explores the origin of leukemic stem-like cells from very small leukemic stem-like cells establish from transformed very small embryonic-like stem cells. We explore theoretical model of acute myeloid leukemia initiation and progresses through various stages, as well basing the HL60 cell line, present its hierarchical stage development in vitro, highlighting the role of these very small precursor primitive stages. We also discuss the potential implications of further research into these unique cellular stages for advancing leukemia and cancer treatment and prevention.

Wnt signaling in the tumor microenvironment: A driver of brain tumor dynamics

The Wnt signaling pathway is important for cell growth and development in the central nervous system and its associated vasculature. Thus, it is an interesting factor for establishing anti-brain cancer therapy. However, simply inhibiting the Wnt signaling pathway in patients with brain tumors is not an effective anti-cancer therapy. Due to their complex microenvironment, which comprises various cell types and signaling molecules, brain tumors pose significant challenges. It is important to understand the interplay between tumor cells and the microenvironment for developing effective therapeutic strategies for both benign and malignant brain tumors. Thus, this research focused on the role of the tumor microenvironment (TME) in brain tumor progression, particularly the involvement of Wnt-dependent signaling pathways. The brain parenchyma comprises neurons, glia, endothelial cells, and other extracellular matrix elements that can contribute to the TME. The TME components can secrete Wnt ligands or associated molecules, resulting in the aberrant activation of the Wnt signaling pathway, followed by tumor progression and therapeutic resistance. Therefore, it is essential to understand the intricate crosstalk between the Wnt signaling pathway and the TME in developing targeted therapies. This review aimed to elucidate the complexities of the brain TME and its interactions with the Wnt signaling pathways to improve treatment outcomes and our understanding of brain tumor biology.

Inhibition of STAT3: A promising approach to enhancing the efficacy of chemotherapy in medulloblastoma

Medulloblastoma is a type of brain cancer that primarily affects children. While chemotherapy has been shown to be effective in treating medulloblastoma, the development of chemotherapy resistance remains a challenge. One potential therapeutic approach is to selectively inhibit the inducible transcription factor called STAT3, which is known to play a crucial role in the survival and growth of tumor cells. The activation of STAT3 has been linked to the growth and progression of various cancers, including medulloblastoma. Inhibition of STAT3 has been shown to sensitize medulloblastoma cells to chemotherapy, leading to improved treatment outcomes. Different approaches to STAT3 inhibition have been developed, including small-molecule inhibitors and RNA interference. Preclinical studies have shown the efficacy of STAT3 inhibitors in medulloblastoma, and clinical trials are currently ongoing to evaluate their safety and effectiveness in patients with various solid tumors, including medulloblastoma. In addition, researchers are also exploring ways to optimize the use of STAT3 inhibitors in combination with chemotherapy and identify biomarkers that can predict treatment that will help to develop personalized treatment strategies. This review highlights the potential of selective inhibition of STAT3 as a novel approach for the treatment of medulloblastoma and suggests that further research into the development of STAT3 inhibitors could lead to improved outcomes for patients with aggressive cancer.

Adrenergic microenvironment driven by cancer-associated Schwann cells contributes to chemoresistance in patients with lung cancer

Doublecortin (DCX)-positive neural progenitor-like cells are purported components of the cancer microenvironment. The number of DCX-positive cells in tissues reportedly correlates with cancer progression; however, little is known about the mechanism by which these cells affect cancer progression. Here we demonstrated that DCX-positive cells, which are found in all major histological subtypes of lung cancer, are cancer-associated Schwann cells (CAS) and contribute to the chemoresistance of lung cancer cells by establishing an adrenergic microenvironment. Mechanistically, the activation of the Hippo transducer YAP/TAZ was involved in the acquisition of new traits of CAS and DCX positivity. We further revealed that CAS express catecholamine-synthesizing enzymes and synthesize adrenaline, which potentiates the chemoresistance of lung cancer cells through the activation of YAP/TAZ. Our findings shed light on CAS, which drive the formation of an adrenergic microenvironment by the reciprocal regulation of YAP/TAZ in lung cancer tissues.

Inhibition of lysosomal TRPML1 channel eliminates breast cancer stem cells by triggering ferroptosis

Cancer stem cells (CSCs) are a sub-population of cells possessing high tumorigenic potential, which contribute to therapeutic resistance, metastasis and recurrence. Eradication of CSCs is widely recognized as a crucial factor in improving patient prognosis, yet the effective targeting of these cells remains a major challenge. Here, we show that the lysosomal cation channel TRPML1 represents a promising target for CSCs. TRPML1 is highly expressed in breast cancer cells and exhibits sensitivity to salinomycin, a drug known to selectively eliminate CSCs. Pharmacological inhibition and genetic depletion of TRPML1 promote ferroptosis in breast CSCs, reduce their stemness, and enhance the sensitivity of breast cancer cells to chemotherapy drug doxorubicin. The inhibition and knockout of TRPML1 also demonstrate significant suppression of tumor formation and growth in the mouse xenograft model. These findings suggest that targeting TRPML1 to eliminate CSCs may be an effective strategy for the treatment of breast cancer.

QiDongNing induces lung cancer cell apoptosis via triggering P53/DRP1-mediated mitochondrial fission

Non-small-cell lung cancer (NSCLC) is a major cause of worldwide cancer death, posing a challenge for effective treatment. Our previous findings showed that Chinese herbal medicine (CHM) QiDongNing (QDN) could upregulate the expression of p53 and trigger cell apoptosis in NSCLC. Here, our objective was to investigate the mechanisms of QDN-induced apoptosis enhancement. We chose A549 and NCI-H460 cells for validation in vitro, and LLC cells were applied to form a subcutaneous transplantation tumour model for validation in more depth. Our findings indicated that QDN inhibited multiple biological behaviours, including cell proliferation, cloning, migration, invasion and induction of apoptosis. We further discovered that QDN increased the pro-apoptotic BAX while inhibiting the anti-apoptotic Bcl2. QDN therapy led to a decline in adenosine triphosphate (ATP) and a rise in reactive oxygen species (ROS). Furthermore, QDN elevated the levels of the tumour suppressor p53 and the mitochondrial division factor DRP1 and FIS1, and decreased the mitochondrial fusion molecules MFN1, MFN2, and OPA1. The results were further verified by rescue experiments, the p53 inhibitor Pifithrin-α and the mitochondrial division inhibitor Mdivi1 partially inhibited QDN-induced apoptosis and mitochondrial dysfunction, whereas overexpression of p53 rather increased the efficacy of the therapy. Additionally, QDN inhibited tumour growth with acceptable safety in vivo. In conclusion, QDN induced apoptosis via triggering p53/DRP1-mediated mitochondrial fission in NSCLC cells.

Influence of tumor microenvironment on the different breast cancer subtypes and applied therapies

Despite the significant improvements made in breast cancer therapy during the last decades, this disease still has increasing incidence and mortality rates. Different targets involved in general processes, like cell proliferation and survival, have become alternative therapeutic options for this disease, with some of them already used in clinic, like the CDK4/6 inhibitors for luminal A tumors treatment. Nevertheless, there is a demand for novel therapeutic strategies focused not only on tumor cells, but also on their microenvironment. Tumor microenvironment (TME) is a very complex and dynamic system that, more than surrounding and supporting tumor cells, actively participates in tumor development and progression. During the last decades, it has become clear that the cellular and acellular components of TME differ between the various breast cancer subtypes and shape the differences regarding their severity and prognosis. The pivotal role of the TME in controlling tumor growth and influencing responses to therapy represents a potential source for novel targets and therapeutic strategies. In this review, we present a description of the multiple therapeutic options used for different breast cancer subtypes, as well as the influence that the TME may exert on the development of the disease and on the response to the distinct therapies, which in some cases may explain their failure by the occurrence of relapses and resistance. Furthermore, the ongoing studies focused on the use of TME components for developing potential cancer treatments are described.

Tumor microenvironment of cancer stem cells: Perspectives on cancer stem cell targeting

There are few tumor cell subpopulations with stem cell characteristics in tumor tissue, defined as cancer stem cells (CSCs) or cancer stem-like cells (CSLCs), which can reconstruct neoplasms with malignant biological behaviors such as invasiveness via self-renewal and unlimited generation. The microenvironment that CSCs depend on consists of various cellular components and corresponding medium components. Among these factors existing at a variety of levels and forms, cytokine networks and numerous signal pathways play an important role in signaling transduction. These factors promote or maintain cancer cell stemness, and participate in cancer recurrence, metastasis, and resistance. This review aims to summarize the recent molecular data concerning the multilayered relationship between CSCs and CSC-favorable microenvironments. We also discuss the therapeutic implications of targeting this synergistic interplay, hoping to give an insight into targeting cancer cell stemness for tumor therapy and prognosis.

Targeting the "tumor microenvironment": RNA-binding proteins in the spotlight in colorectal cancer therapy

Colorectal cancer (CRC) is the third most common cancer and has the second highest mortality rate among cancers. The development of CRC involves both genetic and epigenetic abnormalities, and recent research has focused on exploring the ex-transcriptome, particularly post-transcriptional modifications. RNA-binding proteins (RBPs) are emerging epigenetic regulators that play crucial roles in post-transcriptional events. Dysregulation of RBPs can result in aberrant expression of downstream target genes, thereby affecting the progression of colorectal tumors and the prognosis of patients. Recent studies have shown that RBPs can influence CRC pathogenesis and progression by regulating various components of the tumor microenvironment (TME). Although previous research on RBPs has primarily focused on their direct regulation of colorectal tumor development, their involvement in the remodeling of the TME has not been systematically reported. This review aims to highlight the significant role of RBPs in the intricate interactions within the CRC tumor microenvironment, including tumor immune microenvironment, inflammatory microenvironment, extracellular matrix, tumor vasculature, and CRC cancer stem cells. We also highlight several compounds under investigation for RBP-TME-based treatment of CRC, including small molecule inhibitors such as antisense oligonucleotides (ASOs), siRNAs, agonists, gene manipulation, and tumor vaccines. The insights gained from this review may lead to the development of RBP-based targeted novel therapeutic strategies aimed at modulating the TME, potentially inhibiting the progression and metastasis of CRC.

Selective inhibition of partial EMT-induced tumour cell growth by cerium valence states of extracellular ceria nanoparticles for anticancer treatment

Targeting specific tumour cells and their microenvironments is essential for enhancing the efficacy of chemotherapy and reducing its side effects. A partial epithelial-to-mesenchymal transition state (pEMT, with a hybrid epithelial/mesenchymal phenotype) in tumour cells is an attractive targeting for anticancer treatment because it potentially provides maximal stemness and metastasis relevant to malignant cancer stem cell-like features. However, treatment strategies to target pEMT in tumour cells remain a challenge. This study demonstrates that extracellular cerium oxide nanoparticles (CNPs) selectively inhibit the growth of pEMT-induced tumour cells, without affecting full epithelial tumour cells. Herein, highly concentrated Ce3+ and Ce4+ ions are formed on CNP-layered poly-L-lactic acid surfaces. Cell cultures of pEMT-induced and uninduced lung cancer cell lines on the CNP-layered substrates allow the effect of extracellular CNPs on tumour cell growth to be investigated. The extracellular CNPs with dominant Ce3+ and Ce4+ ions were able to trap pEMT-induced tumour cells in a growth-arrested quiescent/dormant or cytostatic state without generating redox-related reactive oxygen species (ROS), i.e. non-redox mechanisms. The dominant Ce3+ state provided highly efficient growth inhibition of the pEMT-induced tumour cells. In contrast, the dominant Ce4+ state showed highly selective and appropriate growth regulation of normal and tumour cells, including a mesenchymal phenotype. Furthermore, Ce4+-CNPs readily adsorbed serum-derived fibronectin and laminin. Cerium valence-specific proteins adsorbed on CNPs may influence receptor-mediated cell-CNP interactions, leading to tumour cell growth inhibition. These findings provide new perspectives for pEMT-targeting anticancer treatments based on the unique biointerface of extracellular CNPs with different Ce valence states.

Nanomedicine as a multimodal therapeutic paradigm against cancer: on the way forward in advancing precision therapy

Recent years have witnessed dramatic improvements in nanotechnology-based cancer therapeutics, and it continues to evolve from the use of conventional therapies (chemotherapy, surgery, and radiotherapy) to increasingly multi-complex approaches incorporating thermal energy-based tumor ablation (e.g. magnetic hyperthermia and photothermal therapy), dynamic therapy (e.g. photodynamic therapy), gene therapy, sonodynamic therapy (e.g. ultrasound), immunotherapy, and more recently real-time treatment efficacy monitoring (e.g. theranostic MRI-sensitive nanoparticles). Unlike monotherapy, these multimodal therapies (bimodal, i.e., a combination of two therapies, and trimodal, i.e., a combination of more than two therapies) incorporating nanoplatforms have tremendous potential to improve the tumor tissue penetration and retention of therapeutic agents through selective active/passive targeting effects. These combinatorial therapies can correspondingly alleviate drug response against hypoxic/acidic and immunosuppressive tumor microenvironments and promote/induce tumor cell death through various multi-mechanisms such as apoptosis, autophagy, and reactive oxygen-based cytotoxicity, e.g., ferroptosis, etc. These multi-faced approaches such as targeting the tumor vasculature, neoangiogenic vessels, drug-resistant cancer stem cells (CSCs), preventing intra/extravasation to reduce metastatic growth, and modulation of antitumor immune responses work complementary to each other, enhancing treatment efficacy. In this review, we discuss recent advances in different nanotechnology-mediated synergistic/additive combination therapies, emphasizing their underlying mechanisms for improving cancer prognosis and survival outcomes. Additionally, significant challenges such as CSCs, hypoxia, immunosuppression, and distant/local metastasis associated with therapy resistance and tumor recurrences are reviewed. Furthermore, to improve the clinical precision of these multimodal nanoplatforms in cancer treatment, their successful bench-to-clinic translation with controlled and localized drug-release kinetics, maximizing the therapeutic window while addressing safety and regulatory concerns are discussed. As we advance further, exploiting these strategies in clinically more relevant models such as patient-derived xenografts and 3D organoids will pave the way for the application of precision therapy.

Tumor-derived small extracellular vesicles in cancer invasion and metastasis: molecular mechanisms, and clinical significance

The production and release of tumor-derived small extracellular vesicles (TDSEVs) from cancerous cells play a pivotal role in the propagation of cancer, through genetic and biological communication with healthy cells. TDSEVs are known to orchestrate the invasion-metastasis cascade via diverse pathways. Regulation of early metastasis processes, pre-metastatic niche formation, immune system regulation, angiogenesis initiation, extracellular matrix (ECM) remodeling, immune modulation, and epithelial-mesenchymal transition (EMT) are among the pathways regulated by TDSEVs. MicroRNAs (miRs) carried within TDSEVs play a pivotal role as a double-edged sword and can either promote metastasis or inhibit cancer progression. TDSEVs can serve as excellent markers for early detection of tumors, and tumor metastases. From a therapeutic point of view, the risk of cancer metastasis may be reduced by limiting the production of TDSEVs from tumor cells. On the other hand, TDSEVs represent a promising approach for in vivo delivery of therapeutic cargo to tumor cells. The present review article discusses the recent developments and the current views of TDSEVs in the field of cancer research and clinical applications.

Tumor Microenvironment Heterogeneity, Potential Therapeutic Avenues, and Emerging Therapies

OBJECTIVE

This review describes the comprehensive portrait of tumor microenvironment (TME). Additionally, we provided a panoramic perspective on the transformation and functions of the diverse constituents in TME, and the underlying mechanisms of drug resistance, beginning with the immune cells and metabolic dynamics within TME. Lastly, we summarized the most auspicious potential therapeutic strategies.

RESULTS

TME is a unique realm crafted by malignant cells to withstand the onslaught of endogenous and exogenous therapies. Recent research has revealed many small-molecule immunotherapies exhibiting auspicious outcomes in preclinical investigations. Furthermore, some pro-immune mechanisms have emerged as a potential avenue. With the advent of nanosystems and precision targeting, targeted therapy has now transcended the "comfort zone" erected by cancer cells within TME.

CONCLUSION

The ceaseless metamorphosis of TME fosters the intransigent resilience and proliferation of tumors. However, existing therapies have yet to surmount the formidable obstacles posed by TME. Therefore, scientists should investigate potential avenues for therapeutic intervention and design innovative pharmacological and clinical technologies.

Breast cancer stem cells generate immune-suppressive T regulatory cells by secreting TGFβ to evade immune-elimination

Cancer stem cells (CSCs), being the primary contributors in tumor initiation, metastasis, and relapse, ought to have seminal roles in evasion of immune surveillance. Tumor-promoting CD4+CD25+FOXP3+ T-regulatory cells (Tregs) have been described to abolish host defense mechanisms by impeding the activities of other immune cells including effector T cells. However, whether CSCs can convert effector T cells to immune-suppressive Treg subset, and if yes, the mechanism underlying CSC-induced Treg generation, are limitedly studied. In this regard, we observed a positive correlation between breast CSC and Treg signature markers in both in-silico and immunohistochemical analyses. Mirroring the conditions during tumor initiation, low number of CSCs could successfully generate CD4+CD25+FOXP3+ Treg cells from infiltrating CD4+ T lymphocytes in a contact-independent manner. Suppressing the proliferation potential as well as IFNγ production capacity of effector T cells, these Treg cells might be inhibiting antitumor immunity, thereby hindering immune-elimination of CSCs during tumor initiation. Furthermore, unlike non-stem cancer cells (NSCCs), CSCs escaped doxorubicin-induced apoptosis, thus constituting major surviving population after three rounds of chemotherapy. These drug-survived CSCs were also able to generate CD4+CD25+FOXP3+ Treg cells. Our search for the underlying mechanism further unveiled the role of CSC-shed immune-suppressive cytokine TGFβ, which was further increased by chemotherapy, in generating tumor Treg cells. In conclusion, during initiation as well as after chemotherapy, when NSCCs are not present in the tumor microenvironment, CSCs, albeit present in low numbers, generate immunosuppressive CD4+CD25+FOXP3+ Treg cells in a contact-independent manner by shedding high levels of immune-suppressive Treg-polarizing cytokine TGFβ, thus escaping immune-elimination and initiating the tumor or causing tumor relapse.

Phytochemical-Based Nanomedicine for Targeting Tumor Microenvironment and Inhibiting Cancer Chemoresistance: Recent Advances and Pharmacological Insights

Cancer remains the leading cause of death and rapidly evolving disease worldwide. The understanding of disease pathophysiology has improved through advanced research investigation, and several therapeutic strategies are being used for better cancer treatment. However, the increase in cancer relapse and metastatic-related deaths indicate that available therapies and clinically approved chemotherapy drugs are not sufficient to combat cancer. Further, the constant crosstalk between tumor cells and the tumor microenvironment (TME) is crucial for the development, progression, metastasis, and therapeutic response to tumors. In this regard, phytochemicals with multimodal targeting abilities can be used as an alternative to current cancer therapy by inhibiting cancer survival pathways or modulating TME. However, due to their poor pharmacokinetics and low bioavailability, the success of phytochemicals in clinical trials is limited. Therefore, developing phytochemical-based nanomedicine or phytonanomedicine can improve the pharmacokinetic profile of these phytochemicals. Herein, the molecular characteristics and pharmacological insights of the proposed phytonanomedicine in cancer therapy targeting tumor tissue and altering the characteristics of cancer stem cells, chemoresistance, TME, and cancer immunity are well discussed. Further, we have highlighted the clinical perspective and challenges of phytonanomedicine in filling the gap in potential cancer therapeutics using various nanoplatforms. Overall, we have discussed how clinical success and pharmacological insights could make it more beneficial to boost the concept of nanomedicine in the academic and pharmaceutical fields to counter cancer metastases and drug resistance.

Cancer Stem Cells and Glioblastoma: Time for Innovative Biomarkers of Radio-Resistance?

Despite countless papers in the field of radioresistance, researchers are still far from clearly understanding the mechanisms triggered in glioblastoma. Cancer stem cells (CSC) are important to the growth and spread of cancer, according to many studies. In addition, more recently, it has been suggested that CSCs have an impact on glioblastoma patients' prognosis, tumor aggressiveness, and treatment outcomes. In reviewing this new area of biology, we will provide a summary of the most recent research on CSCs and their role in the response to radio-chemotherapy in GB. In this review, we will examine the radiosensitivity of stem cells. Moreover, we summarize the current knowledge of the biomarkers of stemness and evaluate their potential function in the study of radiosensitivity.

Understanding cancer stem cells and plasticity: Towards better therapeutics

The ability of cancer cells to finally overcome various lines of treatment in due course has always baffled the scientific community. Even with the most promising therapies, relapse is ultimately seen, and this resilience has proved to be a major hurdle in the management of cancer. Accumulating evidence now attributes this resilience to plasticity. Plasticity is the ability of cells to change their properties and is substantial as it helps in normal tissue regeneration or post-injury repair processes. It also helps in the overall maintenance of homeostasis. Unfortunately, this critical ability of cells, when activated incorrectly, can lead to numerous diseases, including cancer. Therefore, in this review, we focus on the plasticity aspect with an emphasis on cancer stem cells (CSCs). We discuss the various forms of plasticity that provide survival advantages to CSCs. Moreover, we explore various factors that affect plasticity. Furthermore, we provide the therapeutic implications of plasticity. Finally, we provide an insight into the future targeted therapies involving plasticity for better clinical outcomes.