Brcal Defective Breast Cancer Cells Induce in vitro Transformation of Cancer Associated Fibroblasts (CAFs) to Metastasis Associated Fibroblasts (MAF)

Define cancer-associated fibroblasts (CAFs) in the tumor microenvironment: new opportunities in cancer immunotherapy and advances in clinical trials

Despite centuries since the discovery and study of cancer, cancer is still a lethal and intractable health issue worldwide. Cancer-associated fibroblasts (CAFs) have gained much attention as a pivotal component of the tumor microenvironment. The versatility and sophisticated mechanisms of CAFs in facilitating cancer progression have been elucidated extensively, including promoting cancer angiogenesis and metastasis, inducing drug resistance, reshaping the extracellular matrix, and developing an immunosuppressive microenvironment. Owing to their robust tumor-promoting function, CAFs are considered a promising target for oncotherapy. However, CAFs are a highly heterogeneous group of cells. Some subpopulations exert an inhibitory role in tumor growth, which implies that CAF-targeting approaches must be more precise and individualized. This review comprehensively summarize the origin, phenotypical, and functional heterogeneity of CAFs. More importantly, we underscore advances in strategies and clinical trials to target CAF in various cancers, and we also summarize progressions of CAF in cancer immunotherapy.

Glucose Enhances Pro-Tumorigenic Functions of Mammary Adipose-Derived Mesenchymal Stromal/Stem Cells on Breast Cancer Cell Lines

Adiposity and diabetes affect breast cancer (BC) progression. We addressed whether glucose may affect the interaction between mammary adipose tissue-derived mesenchymal stromal/stem cells (MAT-MSCs) and BC cells. Two-dimensional co-cultures and spheroids were established in 25 mM or 5.5 mM glucose (High Glucose-HG or Low Glucose-LG) by using MAT-MSCs and MCF7 or MDA-MB231 BC cells. Gene expression was measured by qPCR, while protein levels were measured by cytofluorimetry and ELISA. CD44high/CD24low BC stem-like sub-population was quantified by cytofluorimetry. An in vivo zebrafish model was assessed by injecting spheroid-derived labeled cells. MAT-MSCs co-cultured with BC cells showed an inflammatory/senescent phenotype with increased abundance of IL-6, IL-8, VEGF and p16INK4a, accompanied by altered levels of CDKN2A and LMNB1. BC cells reduced multipotency and increased fibrotic features modulating OCT4, SOX2, NANOG, αSMA and FAP in MAT-MSCs. Of note, these co-culture-mediated changes in MAT-MSCs were partially reverted in LG. Only in HG, MAT-MSCs increased CD44high/CD24low MCF7 sub-population and promoted their ability to form mammospheres. Injection in zebrafish embryos of HG spheroid-derived MCF7 and MAT-MSCs was followed by a significant cellular migration and caudal dissemination. Thus, MAT-MSCs enhance the aggressiveness of BC cells in a HG environment.

TGF-β1 induced autophagy in cancer associated fibroblasts during hypoxia contributes EMT and glycolysis via MCT4 upregulation

The Transforming growth factor-β1(TGF- β1) in the tumor microenvironment(TME) is the major cytokine that acts as a mediator of tumor-stroma crosstalk, which in fact has a dual role in either promoting or suppressing tumor development. The cancer-associated fibroblasts (CAFs) are the major cell types in the TME, and the interaction with most of the epithelial cancers is the prime reason for cancer survival. However, the molecular mechanisms, associated with the TGF- β1 induced tumor promotion through tumor-CAF crosstalk are not well understood. In the Reverse Warburg effect, CAFs feed the adjacent cancer cells by lactate produced during the aerobic glycolysis. We hypothesized that the monocarboxylate transporter, MCT4 which is implicated in lactate efflux from the CAFs, must be overexpressed in the CAFs. Contextually, to explore the role of TGF- β1 in the hypoxia-induced autophagy in CAFs, we treated CoCl₂ and external TGF- β1 to the human dermal fibroblasts and L929 murine fibroblasts. We demonstrated that hypoxia accelerated the TGF- β1 signaling and subsequent transformation of normal fibroblasts to CAFs. Moreover, we elucidated that synergistic induction of autophagy by hypoxia and TGF- β1 upregulate the aerobic glycolysis and MCT4 expression in CAFs. Furthermore, we showed a positive correlation between glucose consumption and MCT4 expression in the CAFs. Autophagy was also found to be involved in the EMT in hypoxic CAFs. Collectively, these findings reveal the unappreciated role of autophagy in TME, which enhances the CAF transformation and that promotes tumor migration and metastasis via the reverse Warburg effect.

Modulation of BRCA1 mediated DNA damage repair by deregulated ER-α signaling in breast cancers

BRCA1 mutation carriers have a greater risk of developing cancers in hormone-responsive tissues like breasts and ovaries. However, this tissue-specific incidence of BRCA1 related cancers remains elusive. The majority of the BRCA1 mutated breast cancers exhibit typical histopathological features of high-grade tumors, with basal epithelial phenotype, classified as triple-negative molecular subtype and have a higher percentage of DNA damage and chromosomal abnormality. Though there are many studies relating BRCA1 with ER-α (Estrogen receptor-α), it has not been reported whether E2 (Estrogen) -ER-α signaling can modulate the DNA repair activities of BRCA1. The present study analyzes whether deregulation of ER-α signaling, arising as a result of E2/ER-α deficiency, could impact the BRCA1 dependent DDR (DNA Damage Response) pathways, predominantly those of DNA-DSB (Double Strand break) repair and oxidative damage response. We demonstrate that E2/E2-stimulated ER-α can augment BRCA1 mediated high fidelity repairs like HRR (Homologous Recombination Repair) and BER (Base Excision Repair) in breast cancer cells. Conversely, a condition of ER-α deficiency itself or any interruption in ligand-dependent ER-α transactivation resulted in delayed DNA damage repair, leading to persistent activation of γH2AX and retention of unrepaired DNA lesions, thereby triggering tumor progression. ER-α deficiency not only limited the HRR in cells but also facilitated the DSB repair through error prone pathways like NHEJ (Non Homologous End Joining). ER-α deficiency associated persistence of DNA lesions and reduced expression of DDR proteins were validated in human mammary tumors.

Biological Mechanisms and Therapeutic Opportunities in Mammographic Density and Breast Cancer Risk

Mammographic density is an important risk factor for breast cancer; women with extremely dense breasts have a four to six fold increased risk of breast cancer compared to women with mostly fatty breasts, when matched with age and body mass index. High mammographic density is characterised by high proportions of stroma, containing fibroblasts, collagen and immune cells that suggest a pro-tumour inflammatory microenvironment. However, the biological mechanisms that drive increased mammographic density and the associated increased risk of breast cancer are not yet understood. Inflammatory factors such as monocyte chemotactic protein 1, peroxidase enzymes, transforming growth factor beta, and tumour necrosis factor alpha have been implicated in breast development as well as breast cancer risk, and also influence functions of stromal fibroblasts. Here, the current knowledge and understanding of the underlying biological mechanisms that lead to high mammographic density and the associated increased risk of breast cancer are reviewed, with particular consideration to potential immune factors that may contribute to this process.

Pan-cancer analysis reveals homologous recombination deficiency score as a predictive marker for immunotherapy responders

The immune context of the tumor microenvironment (TME) is critical for effective immunotherapy. Nonetheless, DNA-based biomarkers for the immune-sensitive TME and the identification of immune checkpoint inhibitor (ICI) responders are under-explored. This study aims to comprehensively landscape the homologous recombination deficiency (HRD) score, an emerging hallmark for tumor genome instability that triggers immune responsiveness across major cancer types, and to unveil their link to the TME and immunotherapeutic response. The HRD-associated genomic scars were characterized in 9088 tumor samples across 32 cancer types from TCGA. We evaluated the HRD score's performance in classifying ICI responders using an independent breast cancer cohort (GSE87049) and 11 in vivo murine mammary tumor models treated with anti-PD1/CTLA4 regimen (GSE124821). This study revealed a broad association between HRD-high genotype and neoantigenesis in the major cancer types including bladder cancer, breast cancer, head and neck squamous carcinoma, lung adenocarcinoma, lung squamous cell carcinoma, ovarian cancer, and sarcoma. Tumors with high HRD score bears increased leukocyte infiltration and lymphocyte fraction and demonstrated immune-sensitive microenvironment. The tumor immune dysfunction and exclusion (TIDE) model further confirmed HRD score-high genotype as a potential predictor for ICI immunotherapy responders in breast cancer. In conclusion, tumors with high HRD score exhibit an immune-sensitive TME. The HRD-high genotype is a promising marker for identifying ICI therapy responders among breast cancer patients.

Paracrine TGF-β1 from breast cancer contributes to chemoresistance in cancer associated fibroblasts via upregulation of the p44/42 MAPK signaling pathway

Conventionally, Cancer-associated fibroblasts (CAFs) are considered as an inducer of chemoresistance in cancer cells. However, the underlying mechanism by which carcinomas induce chemoresistance in CAFs through tumor-stroma cross-talk is largely unknown. Henceforth, we uncovered a network of paracrine signals between carcinoma and CAFs that drives chemoresistance in CAFs. Acquired tamoxifen and 5-Fu resistant cell lines MCF-7 and MDA-MB-468 respectively showed higher apoptotic resistance compared to the parental cell. Besides, chemoresistant breast cancer cells showed overexpression of TGF-β1 and have the higher potential to induce CAF phenotype in the normal dermal fibroblasts in a paracrine manner through the TGF-β1 cytokine, compared to their parental cell. Moreover, the chemoresistant cancer cells augmented the EMT markers with a reduction of E-cadherin in the CAFs. Importantly we found out that the TGF- β1 enriched conditioned media from both of the resistant cells triggered chemoresistance in the CAFs by p44/42 MAPK signaling axis. Mechanistically, pharmacological and genetic blockade of TGF-β1 inhibits p44/42 MAPK activation with the subsequent restoration of chemosensitivity in the CAFs. Altogether we ascertained that chemoresistant cancer cells have tremendous potential to modulate the CAFs compared to the parental counterpart. Targeting TGF-β1 and p44/42 MAPK signaling in the future may help to abrogate the chemoresistance in the CAFs.

The Role of BRCA1/2-Mutated Tumor Microenvironment in Breast Cancer

Taking into account the factors of high incidence rate, prevalence and mortality, breast cancer represents a crucial social and economic burden. Most cases of breast cancer develop as a consequence of somatic mutations accumulating in mammary epithelial cells throughout lifetime and approximately 5-10% can be ascribed to monogenic predispositions. Even though the role of genetic predispositions in breast cancer is well described in the context of genetics, very little is known about the role of the microenvironment carrying the same aberrant cells impaired by the germline mutation in the breast cancer development and progression. Based on the clinical observations, carcinomas carrying mutations in hereditary tumor-suppressor genes involved in maintaining genome integrity such as BRCA1/2 have worse prognosis and aggressive behavior. One of the mechanisms clarifying the aggressive nature of BRCA-associated tumors implies alterations within the surrounding adipose tissue itself. The objective of this review is to look at the role of BRCA1/2 mutations in the context of breast tumor microenvironment and plausible mechanisms by which it contributes to the aggressive behavior of the tumor cells.

Site-specific metastasis: A cooperation between cancer cells and the metastatic microenvironment

The conclusion derived from the information provided in this review is that disseminating tumor cells (DTC) collaborate with the microenvironment of a future metastatic organ site in the establishment of organ‐specific metastasis. We review the basic principles of site‐specific metastasis and the contribution of the cross talk between DTC and the microenvironment of metastatic sites (metastatic microenvironment [MME]) to the establishment of the organ‐specific premetastatic niche; the targeted migration of DTC to the endothelium of the future organ‐specific metastasis; the transmigration of DTC to this site and the seeding and colonization of DTC in their future MME. We also discuss the role played by DTC‐MME interactions on tumor dormancy and on the differential response of tumor cells residing in different MMEs to antitumor therapy. Finally, we summarize some studies dealing with the effects of the MME on a unique site‐specific metastasis—brain metastasis.

Influence of Fibroblasts on Mammary Gland Development, Breast Cancer Microenvironment Remodeling, and Cancer Cell Dissemination

The stromal microenvironment regulates mammary gland development and tumorigenesis. In normal mammary glands, the stromal microenvironment encompasses the ducts and contains fibroblasts, the main regulators of branching morphogenesis. Understanding the way fibroblast signaling pathways regulate mammary gland development may offer insights into the mechanisms of breast cancer (BC) biology. In fact, the unregulated mammary fibroblast signaling pathways, associated with alterations in extracellular matrix (ECM) remodeling and branching morphogenesis, drive breast cancer microenvironment (BCM) remodeling and cancer growth. The BCM comprises a very heterogeneous tissue containing non-cancer stromal cells, namely, breast cancer-associated fibroblasts (BCAFs), which represent most of the tumor mass. Moreover, the different components of the BCM highly interact with cancer cells, thereby generating a tightly intertwined network. In particular, BC cells activate recruited normal fibroblasts in BCAFs, which, in turn, promote BCM remodeling and metastasis. Thus, comparing the roles of normal fibroblasts and BCAFs in the physiological and metastatic processes, could provide a deeper understanding of the signaling pathways regulating BC dissemination. Here, we review the latest literature describing the structure of the mammary gland and the BCM and summarize the influence of epithelial-mesenchymal transition (EpMT) and autophagy in BC dissemination. Finally, we discuss the roles of fibroblasts and BCAFs in mammary gland development and BCM remodeling, respectively.

The Metastasis Potential Promoting Capacity of Cancer-Associated Fibroblasts Was Attenuated by Cisplatin via Modulating KRT8

Background

Cancer-associated fibroblasts (CAFs) are an essential component of tumor microenvironment. They are attracting increasing attentions due to their crucial role in tumor growth, drug-resistance and metastasis. Cisplatin is a first-line chemotherapy drug applying in various types of cancer. There are intensive studies on cisplatin's effect on tumor cells, however, its effect on CAFs remains poorly understood. In the present study, we investigated the effect of cisplatin on CAFs.

Methods

Cell migration was detected by wound healing assay. Cell invasion was performed by the transwell assay. mRNA expression was detected by quantitative PCR, and protein expression was detected by Western blotting. Tumor growth was measured using BALB/c nude mice tumor models.

Results

Cisplatin attenuated the promoting capacity of CAFs on lung cancer cell migration and invasion, via suppressing CAFs' effect on metastasis-related genes including Twist1, vascular endothelial growth factor receptor (VEGFR), MMP2, and AKT signaling pathway. Keratin 8 (KRT8) was identified as a target of cisplatin. KRT8 upregulation in CAFs is responsible for the inhibitory effect of cisplatin on lung cancer cells metastasis potential through AKT pathway suppression. The stimulation of AKT by AKT activator SC79 reversed KRT8's effect on cell migration. Importantly, in vivo study also showed that CAFs enhanced tumor growth significantly, and cisplatin effectively abrogated the promoting effect of CAFs on tumor growth.

Conclusion

Our results revealed a novel mechanism that cisplatin attenuated the metastasis promoting effect of CAFs via KRT8/AKT signaling pathway. This finding highlights KRT8 in CAFs as a potential therapeutic candidate for metastasis treatment.

Cancer associated fibroblasts as novel promising therapeutic targets in breast cancer

Breast cancer is one of the most important women-related malignancies, which is incurable (particularly in advanced stages) and tumor microenvironment is a number one accused part in the inefficiency of current anti-breast cancer therapeutic strategies. The tumor microenvironment is composed of various cellular and acellular components, which provide an optimum condition for freely expanding cancer cells in various cancer types, particularly breast cancer. Cancer-associated fibroblasts (CAFs) are one of the main cell types in the breast tumor region, which can promote various tumor-promoting processes such as expansion, angiogenesis, metastasis and drug resistance. CAFs directly (by cell-to-cell communication) and indirectly (through secreting soluble factors) can exert their tumorigenic functions. We try to elucidate the immunobiology of CAFs, their origin, function, and heterogeneity in association with their role in various cancer-promoting processes in breast cancer. Based on current knowledge, we believe that the origin of CAFs, their subsets, and their specific expressed biomarkers determine their pro- or anti-tumor functions. Therefore, targeting CAF without considering their specific functions may lead to a deleterious outcome. We propose to find and characterize each subtype of CAFs in association with its specific function in different stages of breast cancer to develop novel promising therapeutic approaches against the right CAF subtype.