Cancer-Associated Adipocytes and Breast Cancer: Intertwining in the Tumor Microenvironment and Challenges for Cancer Therapy

Dissecting the emerging role of cancer-associated adipocyte-derived cytokines in remodeling breast cancer progression

Breast cancer has been reported to transcend lung cancer as the most commonly diagnosed cancer in women all over the world. Adipocytes, serving as energy storage and endocrine cells, are the major stromal cells in the breast. Cancer-associated adipocytes (CAAs) are adjacent and dedifferentiated adipocytes located at the invasive front of human breast tumors. Adipocytes can transform into CAA phenotype with morphological and biological changes under the remodeling of breast cancer cells. CAAs play an essential role in breast cancer progression, including remodeling the tumor microenvironment (TME), regulating immunity, and interacting with breast cancer cells. CAAs possess peculiar secretomes and are accordingly capable to promote proliferation, invasiveness, angiogenesis, metastasis, immune escape, and drug resistance of breast cancer cells. There is a complex and coordinated crosstalk among CAAs, immune cells, and breast cancer cells. CAAs can release a variety of cytokines, including IL-6, IL-8, IL-1β, CCL5, CCL2, VEGF, G-CSF, IGF-1, and IGFBP, thereby promoting immune cell recruitment and macrophage polarization, and ultimately stimulating malignant behaviors in breast cancer cells. Here, we aim to provide a comprehensive description of CAA-derived cytokines, including their impact on cancer cell behaviors, immune regulation, breast cancer diagnosis, and treatment. A deeper understanding of CAA performance and interactions with specific TME cell populations will provide better strategies for cancer treatment and breast reconstruction after mastectomy.

Hesperidin PLGA nanoparticles potentiate the efficacy of aPD-1 in treating triple negative breast cancer by regulating CCL2 and ADPN expression in cancer-associated adipocytes

Triple negative breast cancer (TNBC) represents a heterogeneous subtype of breast cancer characterized by an unfavorable prognosis due to its aggressive biology. Cancer-associated adipocytes (CAAs) play an active role in tumor development, invasion and metastasis, and response to treatment by secreting various cytokines. CAAs secrete CCL2 and ADPN which significantly affect the efficacy of aPD-1 in treating breast cancer. Our recent research has demonstrated that Hesperidin, a natural phenolic compound, significantly inhibits CCL2, elevates ADPN secreted by CAAs in vitro and in vivo, remodels the immune microenvironment, and potentiates the efficacy of aPD-1 in triple-negative breast cancer. We used Oil red staining, Bodipy 493/503 staining and quantitative real-time PCR to verify the formation of CAAs. ELISA was used to detect levels of CCL2, ADPN secreted by CAAs. Changes in the number of immune cells in mouse tumor tissues were detected using flow cytometry and immunofluorescence. Our data suggest that Hesperidin PLGA nanoparticles significantly reduced CCL2 and increased ADPN secreted by CAAs, which concurrently decreased the recruitment of M2 macrophages, Tregs and MDSCs while increased the infiltration of CD8+T cells, M1 macrophages and DCs into tumor, thus significantly potentiated the efficacy of aPD-1 in vivo. This study provides a new combined strategy for the clinical treatment of triple-negative breast cancer by interfering with CCL2, ADPN secreted by CAAs to enhance the efficacy of immunotherapy.

A keratinocyte-adipocyte signaling loop is reprogrammed by loss of BTG3 to augment skin carcinogenesis

Obesity is endemic to many developed countries. Overweight or obesity is associated with an increased risk of developing cancer. Dysfunctional adipose tissue alters cancer cell proliferation and migration; however, whether and how neoplastic epithelial cells communicate with adipose tissue and the underlying mechanism are less clear. BTG3 is a member of the anti-proliferative BTG/Tob family and functions as a tumor suppressor. Here, we demonstrated that BTG3 levels are downregulated in basal cell carcinoma and squamous cell carcinoma compared to normal skin tissue, and Btg3 knockout in mice augmented the development of papilloma in a mouse model of DMBA/TPA-induced skin carcinogenesis. Mechanistically, BTG3-knockout keratinocytes promoted adipocyte differentiation mainly through the release of IL1α, IL10, and CCL4, as a result of elevated NF-κB activity. These adipocytes produced CCL20 and FGF7 in a feedback loop to promote keratinocyte migration. Thus, our findings showcased the role of BTG3 in guarding the interplay between keratinocytes and adjacent adipocytes, and identified the underlying neoplastic molecular mediators that may serve as possible targets in the treatment of skin cancer.

The relationship between Stroma AReactive Invasion Front Areas (SARIFA), Warburg-subtype and survival: results from a large prospective series of colorectal cancer patients

BACKGROUND

Stroma AReactive Invasion Front Areas (SARIFA) is a recently identified haematoxylin & eosin (H&E)based histopathologic biomarker in gastrointestinal cancers, including colorectal cancer (CRC), defined as direct contact between tumour cells and adipocytes at the tumour invasion front. The current study aimed at validating the prognostic relevance of SARIFA in a large population-based CRC series as well as at investigating the relationship between SARIFA-status and previously established Warburg-subtypes, both surrogates of the metabolic state of the tumour cells.

METHODS

SARIFA-status (positive versus negative) was determined on H&E slides of 1,727 CRC specimens. Warburg-subtype (high versus moderate versus low) data was available from our previous study. The associations between SARIFA-status, Warburg-subtype, clinicopathological characteristics and CRC-specific as well as overall survival were investigated.

RESULTS

28.7% (n=496) CRC were SARIFA-positive. SARIFA-positivity was associated with more advanced disease stage, higher pT category, and more frequent lymph node involvement (all p<0.001). SARIFA-positivity was more common in Warburg-high CRC. 44.2% (n=219) of SARIFA-positive CRCs were Warburg-high compared to 22.8% (n=113) being Warburg-low and 33.1% (n=164) being Warburg-moderate (p<0.001). In multivariable-adjusted analysis, patients with SARIFA-positive CRCs had significantly poorer CRC-specific (HRCRC-specific 1.65; 95% CI 1.41-1.93) and overall survival (HRoverall survival 1.46; 95% CI 1.28-1.67) independent of clinically known risk factors and independent of Warburg-subtype. Combining the SARIFA-status and the Warburg-subtype to a combination score (SARIFA-negative/Warburg-high versus SARIFA-positive/Warburg-low versus SARIFA-positive/Warburg-high, and so on) did not improve the survival prediction compared to the use of SARIFA-status alone (SARIFA-negative + Warburg-high: HRCRC-specific 1.08; 95% CI 0.84-1.38; SARIFA-positive + Warburg-low: HRCRC-specific 1.79; 95% CI 1.32-2.41; SARIFA-positive + Warburg-high: HRCRC-specific 1.58; 95% CI 1.23-2.04).

CONCLUSIONS

Our current study is the by far largest external validation of SARIFA-positivity as a novel independent negative prognostic H&E-based biomarker in CRC. In addition, our study shows that SARIFA-positivity is associated with the Warburg-high subtype. Further research is warranted to provide a more mechanistic understanding of the underlying tumour biology. Based on our data, we conclude SARIFA-status should be implemented in pathologic routine practice to stratify CRC patients.

A review concerning the breast cancer-related tumour microenvironment

Breast cancer (BC) is currently the most common malignant tumour in women and one of the leading causes of their death around the world. New and increasingly personalised diagnostic and therapeutic tools have been introduced over the last few decades, along with significant advances regarding the study and knowledge related to BC. The tumour microenvironment (TME) refers to the tumour cell-associated cellular and molecular environment which can influence conditions affecting tumour development and progression. The TME is composed of immune cells, stromal cells, extracellular matrix (ECM) and signalling molecules secreted by these different cell types. Ever deeper understanding of TME composition changes during tumour development and progression will enable new and more innovative therapeutic strategies to become developed for targeting tumours during specific stages of its evolution. This review summarises the role of BC-related TME components and their influence on tumour progression and the development of resistance to therapy. In addition, an account on the modifications in BC-related TME components associated with therapy is given, and the completed or ongoing clinical trials related to this topic are presented.

Breast Cancer: Extracellular Matrix and Microbiome Interactions

Breast cancer represents the most prevalent form of cancer and the leading cause of cancer-related mortality among females worldwide. It has been reported that several risk factors contribute to the appearance and progression of this disease. Despite the advancements in breast cancer treatment, a significant portion of patients with distant metastases still experiences no cure. The extracellular matrix represents a potential target for enhanced serum biomarkers in breast cancer. Furthermore, extracellular matrix degradation and epithelial-mesenchymal transition constitute the primary stages of local invasion during tumorigenesis. Additionally, the microbiome has a potential influence on diverse physiological processes. It is emerging that microbial dysbiosis is a significant element in the development and progression of various cancers, including breast cancer. Thus, a better understanding of extracellular matrix and microbiome interactions could provide novel alternatives to breast cancer treatment and management. In this review, we summarize the current evidence regarding the intricate relationship between breast cancer with the extracellular matrix and the microbiome. We discuss the arising associations and future perspectives in this field.

Role of cancer stem cell ecosystem on breast cancer metastasis and related mouse models

Breast cancer metastasis is responsible for most breast cancer-related deaths and is influenced by many factors within the tumor ecosystem, including tumor cells and microenvironment. Breast cancer stem cells (BCSCs) constitute a small population of cancer cells with unique characteristics, including their capacity for self-renewal and differentiation. Studies have shown that BCSCs not only drive tumorigenesis but also play a crucial role in promoting metastasis in breast cancer. The tumor microenvironment (TME), composed of stromal cells, immune cells, blood vessel cells, fibroblasts, and microbes in proximity to cancer cells, is increasingly recognized for its crosstalk with BCSCs and role in BCSC survival, growth, and dissemination, thereby influencing metastatic ability. Hence, a thorough understanding of BCSCs and the TME is critical for unraveling the mechanisms underlying breast cancer metastasis. In this review, we summarize current knowledge on the roles of BCSCs and the TME in breast cancer metastasis, as well as the underlying regulatory mechanisms. Furthermore, we provide an overview of relevant mouse models used to study breast cancer metastasis, as well as treatment strategies and clinical trials addressing BCSC-TME interactions during metastasis. Overall, this study provides valuable insights for the development of effective therapeutic strategies to reduce breast cancer metastasis.

Dysfunctional adipocytes promote tumor progression through YAP/TAZ-dependent cancer-associated adipocyte transformation

Obesity has emerged as a prominent risk factor for the development of malignant tumors. However, the existing literature on the role of adipocytes in the tumor microenvironment (TME) to elucidate the correlation between obesity and cancer remains insufficient. Here, we aim to investigate the formation of cancer-associated adipocytes (CAAs) and their contribution to tumor growth using mouse models harboring dysfunctional adipocytes. Specifically, we employ adipocyte-specific BECN1 KO (BaKO) mice, which exhibit lipodystrophy due to dysfunctional adipocytes. Our results reveal the activation of YAP/TAZ signaling in both CAAs and BECN1-deficient adipocytes, inducing adipocyte dedifferentiation and formation of a malignant TME. The additional deletion of YAP/TAZ from BaKO mice significantly restores the lipodystrophy and inflammatory phenotypes, leading to tumor regression. Furthermore, mice fed a high-fat diet (HFD) exhibit decreased BECN1 and increased YAP/TAZ expression in their adipose tissues. Treatment with the YAP/TAZ inhibitor, verteporfin, suppresses tumor progression in BaKO and HFD-fed mice, highlighting its efficacy against mice with metabolic dysregulation. Overall, our findings provide insights into the key mediators of CAA and their significance in developing a TME, thereby suggesting a viable approach targeting adipocyte homeostasis to suppress cancer growth.

Nf1 deficiency modulates the stromal environment in the pretumorigenic rat mammary gland

Background

Neurofibromin, coded by the NF1 tumor suppressor gene, is the main negative regulator of the RAS pathway and is frequently mutated in various cancers. Women with Neurofibromatosis Type I (NF1)-a tumor predisposition syndrome caused by a germline NF1 mutation-have an increased risk of developing aggressive breast cancer with poorer prognosis. The mechanism by which NF1 mutations lead to breast cancer tumorigenesis is not well understood. Therefore, the objective of this work was to identify stromal alterations before tumor formation that result in the increased risk and poorer outcome seen among NF1 patients with breast cancer.

Approach

To accurately model the germline monoallelic NF1 mutations in NF1 patients, we utilized an Nf1-deficient rat model with accelerated mammary development before presenting with highly penetrant breast cancer.

Results

We identified increased collagen content in Nf1-deficient rat mammary glands before tumor formation that correlated with age of tumor onset. Additionally, gene expression analysis revealed that Nf1-deficient mature adipocytes in the rat mammary gland have increased collagen expression and shifted to a fibroblast and preadipocyte expression profile. This alteration in lineage commitment was also observed with in vitro differentiation, however, flow cytometry analysis did not show a change in mammary adipose-derived mesenchymal stem cell abundance.

Conclusion

Collectively, this study uncovered the previously undescribed role of Nf1 in mammary collagen deposition and regulating adipocyte differentiation. In addition to unraveling the mechanism of tumor formation, further investigation of adipocytes and collagen modifications in preneoplastic mammary glands will create a foundation for developing early detection strategies of breast cancer among NF1 patients.

Glutathione-Responsive Organosilica Hybrid Nanosystems for Targeted Dual-Starvation Therapy in Luminal Breast Cancer

Starvation therapy is an innovative approach in cancer treatment aimed at depriving cancer cells of necessary resources by impeding tumor angiogenesis or blocking the energy supply. In addition to the commonly observed anaerobic glycolysis energy supply mode, adipocyte-rich tumor tissue triggers the fatty acid energy supply pathway, which fuels the proliferation and metastasis of cancer cells. To completely disrupt these dual-energy-supply pathways, we developed an exceptional nanoreactor. This nanoreactor consisted of yolk-shell mesoporous organosilica nanoparticles (YSMONs) loaded with a fatty acid transport inhibitor (Dox), conjugated with a luminal breast-cancer-specific targeting aptamer, and integrated with a glucose oxidation catalyst (GOx). Upon reaching cancer cells with the assistance of the aptamer, the nanoreactor underwent a structural collapse of the shell triggered by the high concentration of glutathione within cancer cells. This collapse led to the release of GOx and Dox, achieving targeted delivery and exhibiting significant efficacy in starving therapy. Additionally, the byproducts of glucose metabolism, gluconic acid and H2O2, enhanced the acidity and reactive oxygen species levels of the intracellular microenvironment, inducing oxidative damage to cancer cells. Simultaneously, released Dox acted as a potent broad-spectrum anticancer drug, inhibiting the activity of carnitine palmitoyltransferase 1A and exerting marked effects. Combining these effects ensures high anticancer efficiency, and the "dual-starvation" nanoreactor has the potential to establish a novel synergistic therapy paradigm with considerable clinical significance. Furthermore, this approach minimizes damage to normal organs, making it highly valuable in the field of cancer treatment.

p53 deficient breast cancer cells reprogram preadipocytes toward tumor-protective immunomodulatory cells

The TP53 gene is mutated in approximately 30% of all breast cancer cases. Adipocytes and preadipocytes, which constitute a substantial fraction of the stroma of normal mammary tissue and breast tumors, undergo transcriptional, metabolic, and phenotypic reprogramming during breast cancer development and play an important role in tumor progression. We report here that p53 loss in breast cancer cells facilitates the reprogramming of preadipocytes, inducing them to acquire a unique transcriptional and metabolic program that combines impaired adipocytic differentiation with augmented cytokine expression. This, in turn, promotes the establishment of an inflammatory tumor microenvironment, including increased abundance of Ly6C+ and Ly6G+ myeloid cells and elevated expression of the immune checkpoint ligand PD-L1. We also describe a potential gain-of-function effect of common p53 missense mutations on the inflammatory reprogramming of preadipocytes. Altogether, our study implicates p53 deregulation in breast cancer cells as a driver of tumor-supportive adipose tissue reprogramming, expanding the network of non-cell autonomous mechanisms whereby p53 dysfunction may promote cancer. Further elucidation of the interplay between p53 and adipocytes within the tumor microenvironment may suggest effective therapeutic targets for the treatment of breast cancer patients.

Metabolites and Immune Response in Tumor Microenvironments

The remodeled cancer cell metabolism affects the tumor microenvironment and promotes an immunosuppressive state by changing the levels of macro- and micronutrients and by releasing hormones and cytokines that recruit immunosuppressive immune cells. Novel dietary interventions such as amino acid restriction and periodic fasting mimicking diets can prevent or dampen the formation of an immunosuppressive microenvironment by acting systemically on the release of hormones and growth factors, inhibiting the release of proinflammatory cytokines, and remodeling the tumor vasculature and extracellular matrix. Here, we discuss the latest research on the effects of these therapeutic interventions on immunometabolism and tumor immune response and future scenarios pertaining to how dietary interventions could contribute to cancer therapy.