TGF-β1-mediated transition of resident fibroblasts to cancer-associated fibroblasts promotes cancer metastasis in gastrointestinal stromal tumor

MiR-206 suppresses the deterioration of intrahepatic cholangiocarcinoma and promotes sensitivity to chemotherapy by inhibiting interactions with stromal CAFs

Background: Intrahepatic cholangiocarcinoma (iCCA) is a highly malignant subtype of cholangiocarcinoma (CCA) with poor prognosis. In iCCA, the interplay between the stroma and tumor cells results in resistance to adjuvant chemotherapy. Increasing evidence indicates that miR-206 participates in tumor progression, but its role in iCCA is still unclear. The aim of this study was to identify dysregulated miR-206 expression in iCCA and to further explore the underlying mechanism.

Methods: MiR-206 expression was proven to be downregulated in iCCA tissues by qPCR, and its correlation with clinical characteristics and prognosis was investigated. iCCA-derived cancer-associated fibroblast cells (CAFs) and normal fibroblast cells (NFs) were isolated and identified. MiR-206 was knocked in or down in CAFs and CCA cells, respectively, to explore the role of miR-206, and coculture of these treated CCAs and CAFs was conducted to explore the effects of miR-206 on their mutual promoting effects. Exosomes carrying miR-206 and an orthotopic mouse model were used to determine the inhibitory effects of miR-206 on iCCA deterioration in vivo.

Results: We confirmed that miR-206 is a suppressor of iCCA. Overexpressing miR-206 in CCA cells inhibited cell proliferation, migration and invasion. When cocultured with CCA cells, NFs downregulated miR-206 expression, and NFs were susceptible to transforming into CAFs. Moreover, CAFs promoted CCA cell malignant behaviors and gemcitabine resistance. Overexpressing miR-206 in CAFs or CCA cells inhibited this mutual promoting effect. Additionally, when delivered by exosomes, miR-206 suppressed tumor deterioration. And combined with gemcitabine, this treatment resulted in a longer survival time.

Conclusion: Our study explained that the interaction between CCA cells and CAFs promoted iCCA deterioration. As a suppressive factor, miR-206 inhibited aggressive characteristics and gemcitabine resistance by interfering with this mutual promoting effect. This research elucidated the molecular mechanism underlying the unfavorable chemotherapeutic response of patients with iCCA, which provided a promising target for iCCA treatment.

Extracellular vesicles in pharmacology: Novel approaches in diagnostics and therapy

Exosomes are nano-sized lipid vesicles that are produced by all eukaryotic cells, and they typically range in size from 30 to 150 nm. Exosomes were discovered almost 40 years ago; however, the last two decades have attracted considerable attention due to exosomes' inherent abilities to shuttle nucleic acids, lipids and proteins between cells, along with their natural affinity to exosome target cells. From a pharmaceutical perspective, exosomes are regarded as naturally produced nanoparticle drug delivery vehicles. The application of exosomes as a means of drug delivery offers critical advantages compared to other nanoparticulate drug delivery systems, such as liposomes and polymeric nanoparticles. These advantages are due to the exosomes' intrinsic features, such as low immunogenicity, biocompatibility, stability, and their ability to overcome biological barriers. Herein, we outline the structure and origin of exosomes, as well as their biological functions. We also touch upon recent advances in exosome labeling, imaging and drug loading. Finally, we discuss exosomes in targeted drug delivery and clinical trial development.

The cancer-inhibitory effects of proliferating tumor-residing fibroblasts

Initiation, local progression, and metastasis of cancer are associated with specific morphological, molecular, and functional changes in the extracellular matrix and the fibroblasts within the tumor microenvironment (TME). In the early stages of tumor development, fibroblasts are an obstacle that cancer cells must surpass or nullify to progress. Thus, in early tumor progression, specific signaling from cancer cells activates bio-pathways, which abolish the innate anticancer properties of fibroblasts and convert a high proportion of them to tumor-promoting cancer-associated fibroblasts (CAFs). Following this initial event, a wide spectrum of gene expression changes gradually leads to the development of a stromal fibroblast population with complex heterogeneity, creating fibroblast subtypes with characteristic profiles, which may alternate between being tumor-promotive and tumor-suppressive, topologically and chronologically in the TME. These fibroblast subtypes form the tumor's histological landscape including areas of cancer growth, inflammation, angiogenesis, invasion fronts, proliferating and non-proliferating fibroblasts, cancer-cell apoptosis, fibroblast apoptosis, and necrosis. These features reflect general deregulation of tissue homeostasis within the TME. This review discusses fundamental and current knowledge that has established the existence of anticancer fibroblasts within the various interacting elements of the TME. It is proposed that the maintenance of fibroblast proliferation is an essential parameter for the activation of their anticancer capacity, similar to that by which normal fibroblasts would be activated in wound repair, thus maintaining tissue homeostasis. Encouragement of research in this direction may render new means of cancer therapy and a greater understanding of tumor progression.

Atorvastatin facilitates chemotherapy effects in metastatic triple-negative breast cancer

BACKGROUND

Metastatic triple-negative breast cancer (mTNBC) is treated mainly with chemotherapy. However, resistance frequently occurs as tumours enter dormancy. Statins have been suggested as effective against cancer but as they prolong and promote dormancy, it is an open question of whether the concomitant use would interfere with chemotherapy in primary and mTNBC. We examined this question in animal models and clinical correlations.

METHODS

We used a xenograft model of spontaneous metastasis to the liver from an ectopic tumour employing a mTNBC cell line. Atorvastatin was provided to sensitise metastatic cells, followed by chemotherapy. The effects of statin usage on outcomes in women with metastatic breast cancer was assessed respectively by querying a database of those diagnosed from 1999 to 2019.

RESULTS

Atorvastatin had limited influence on tumour growth or chemotherapy effects in ectopic primary tumours. Interestingly, atorvastatin was additive with doxorubicin (but not paclitaxel) when targeting liver metastases. E-cadherin-expressing, dormant, breast cancer cells were resistant to the use of either statins or chemotherapy as compared to wild-type cells; however, the combination of both did lead to increased cell death. Although prospective randomised studies are needed for validation, our retrospective clinical analysis suggested that patients on statin treatment could experience prolonged dormancy and overall survival; still once the tumour recurred progression was not affected by statin use.

CONCLUSION

Atorvastatin could be used during adjuvant chemotherapy and also in conjunction with metastatic chemotherapy to reduce mTNBC cancer progression. These preclinical data establish a rationale for the development of randomised studies.

The Multifaceted Role of TGF-β in Gastrointestinal Tumors

Simple Summary

The transforming growth factor β signaling pathway elicits a broad range of physiological re-sponses, and its misregulation has been related to cancer. The secreted cytokine TGFβ exerts a tumor-suppressive effect that counteracts malignant transformation. However, once tumor has developed, TGFβ can support tumor progression regulating epithelial to mesenchymal transition, invasion and metastasis, stimulating fibrosis, angiogenesis and immune suppression. Here we review the dichotomous role of TGF-β in the progression of gastrointestinal tumors, as well as its intricate crosstalk with other signaling pathways. We also discuss about the therapeutic strate-gies that are currently explored in clinical trials to counteract TGF-β functions.

Abstract

Transforming growth factor-beta (TGF-β) is a secreted cytokine that signals via serine/threonine kinase receptors and SMAD effectors. Although TGF-β acts as a tumor suppressor during the early stages of tumorigenesis, it supports tumor progression in advanced stages. Indeed, TGF-β can modulate the tumor microenvironment by modifying the extracellular matrix and by sustaining a paracrine interaction between neighboring cells. Due to its critical role in cancer development and progression, a wide range of molecules targeting the TGF-β signaling pathway are currently under active clinical development in different diseases. Here, we focused on the role of TGF-β in modulating different pathological processes with a particular emphasis on gastrointestinal tumors.

Cancer-Associated Fibroblast Heterogeneity: A Factor That Cannot Be Ignored in Immune Microenvironment Remodeling

Cancer-associated fibroblasts (CAFs) are important, highly heterogeneous components of the tumor extracellular matrix that have different origins and express a diverse set of biomarkers. Different subtypes of CAFs participate in the immune regulation of the tumor microenvironment (TME). In addition to their role in supporting stromal cells, CAFs have multiple immunosuppressive functions, via membrane and secretory patterns, against anti-tumor immunity. The inhibition of CAFs function and anti-TME therapy targeting CAFs provides new adjuvant means for immunotherapy. In this review, we outline the emerging understanding of CAFs with a particular emphasis on their origin and heterogeneity, different mechanisms of their regulation, as well as their direct or indirect effect on immune cells that leads to immunosuppression.

Normalization in tumor ecosystem: Opportunities and challenges

Current research in cancer therapy aims to exploit efficient strategies to have long-lasting effects on tumors and to reduce or even revoke the chance of recurrence. Within the tumor stroma, O₂ and nutrients are abnormally distributed between various cells (preferentially for supplying cancer cells), the immune contexture is abnormally positioned (permissive essentially for cells exhibiting tumor-promoting capacity), the fibroblast and fibrotic content is abnormally distributed (presence of both extracellular matrix [ECM] stiffening and ECM-degrading factors both for tumor-promoting purposes), and the tumor vasculature is abnormally orchestrated (for hindering drug delivery and increasing the chance of tumor metastasis). Resistance is actually an adaptive response to an imbalance in the tumor ecosystem; thus, the key consideration for effective cancer therapy is to bring back the normal status in this ecosystem so as to reach the desired durable outcome. Vascular normalization, metabolic modulation (glucose delivery in particular), balancing cellular dispersion, and balancing the pH rate and O₂ delivery within the tumor microenvironment are suggested strategies to reverse abnormality within the tumor stroma.