The role of exosomes in cancer biology by shedding light on their lipid contents

Exosomes are extracellular bilayer membrane nanovesicles released by cells after the fusion of multivesicular bodies (MVBs) with the plasma membrane. One of the interesting features of exosomes is their ability to carry and transfer various molecules, including lipids, proteins, nucleic acids, and therapeutic cargoes among cells. As intercellular signaling organelles, exosomes participate in various signaling processes such as tumor growth, metastasis, angiogenesis, epithelial-to-mesenchymal transition (EMT), and cell physiology such as cell-to-cell communication. Moreover, these particles are considered good vehicles to shuttle vaccines and drugs for therapeutic applications regarding cancers and tumor cells. These bioactive vesicles are also rich in various lipid molecules such as cholesterol, sphingomyelin (SM), glycosphingolipids, and phosphatidylserine (PS). These lipids play an important role in the formation, release, and function of the exosomes and interestingly, some lipids are used as biomarkers in cancer diagnosis. This review aimed to focus on exosomes lipid content and their role in cancer biology.

The role and application of small extracellular vesicles in breast cancer

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related deaths in women worldwide. Currently, patients’ survival remains a challenge in BC due to the lack of effective targeted therapies and the difficult condition of patients with higher aggressiveness, metastasis and drug resistance. Small extracellular vesicles (sEVs), which are nanoscale vesicles with lipid bilayer envelopes released by various cell types in physiological and pathological conditions, play an important role in biological information transfer between cells. There is growing evidence that BC cell-derived sEVs may contribute to the establishment of a favorable microenvironment that supports cancer cells proliferation, invasion and metastasis. Moreover, sEVs provide a versatile platform not only for the diagnosis but also as a delivery vehicle for drugs. This review provides an overview of current new developments regarding the involvement of sEVs in BC pathogenesis, including tumor proliferation, invasion, metastasis, immune evasion, and drug resistance. In addition, sEVs act as messenger carriers carrying a variety of biomolecules such as proteins, nucleic acids, lipids and metabolites, making them as potential liquid biopsy biomarkers for BC diagnosis and prognosis. We also described the clinical applications of BC derived sEVs associated MiRs in the diagnosis and treatment of BC along with ongoing clinical trials which will assist future scientific endeavors in a more organized direction.

Early metabolic response of breast cancer to neoadjuvant endocrine therapy: comparison to morphological and pathological response

Background

Neoadjuvant endocrine therapy (NET) has shown efficacy in terms of clinical response and surgical outcome in postmenopausal patients with estrogen receptor-positive / HER2-negative breast cancer (ER+/HER2- BC) but monitoring of tumor response is challenging. The aim of the present study was to investigate the value of an early metabolic response compared to morphological and pathological responses in this population.

Methods

This was an ancillary study of CARMINA 02, a phase II clinical trial evaluating side-by-side the efficacy of 4 to 6 months of anastrozole or fulvestrant. Positron Emission Tomography/Computed Tomography using 2-deoxy-2-[¹⁸F]fluoro-D-glucose (FDG-PET/CT) scans were performed at baseline (M0), early after 1 month of treatment (M1) and pre-operatively in 11 patients (74.2 yo ± 3.6). Patients were classified as early “metabolic responders” (mR) when the decrease of SUVmax was higher than 40%, and “metabolic non-responders” (mNR) otherwise. Early metabolic response was compared to morphological response (palpation, US and MRI), variation of Ki-67 index, pathological response according to the Sataloff classification and also to Preoperative Endocrine Prognostic Index (PEPI) score. It was also correlated with overall survival (OS) and recurrence-free survival (RFS).

Results

Tumor size measured on US and on MRI was smaller in mR than mNR, with the highest statistically significant difference at M1 (p = 0.01 and 7.1 × 10^− 5, respectively). No statistically significant difference in the variation of tumor size between M0 and M1 assessed on US or MRI was observed between mR and mNR. mR had a better clinical response: no progressive disease in mR vs 2 in mNR and 2 partial response in mR vs 1 partial response in mNR. One patient with a pre-operative complete metabolic response had the best pathological response. Pathological response did not show any statistically significant difference between mR and mNR. mR had better OS and RFS (Kaplan-Meier p = 0.08 and 0.06, respectively). All cancer-related events occurred in mNR: 3 patients died, 2 of them from progressive disease.

Conclusions

FDG-PET/CT imaging could become a “surrogate marker” to monitor tumor response, especially as NET is a valuable treatment option in postmenopausal women with ER+/HER2- BC.

Young Patients with Hormone Receptor-Positive Breast Cancer Have a Higher Long-Term Risk of Breast Cancer Specific Death

Purpose

Although it is widely accepted that hormone receptor (HR) status is associated with later post-diagnostic periods, a debate exists as to whether the association is independent of age. The aim of our study was to confirm the impact of HR status on later period breast cancer-specific death (LP-BCSD) and later period non-breast cancer-specific death (LP-non-BCSD) in different age subgroups.

Methods

Surveillance, Epidemiology, and End Results databases were utilized to identify 181,108 breast cancer patients with > 5 years survival. The cumulative incidence of LP-BCSD and LP-non-BCSD was calculated using the Gray method. The subdistribution hazard ratio (SHR) of variables was estimated via the Fine and Gray proportional hazard regression model. Subgroup analyses for LP-BCSD and LP-non-BCSD were performed according to the HR status.

Results

The risk of LP-BCSD was exceeded by that of LP-non-BCSD at > 5 years since the diagnosis, particularly in old women. The competing risk regression model indicated that hormone receptor-positive (HR+) was an independent factor for more LP-BCSD (hazard ratio, 1.54; 95% confidence interval, 1.44–1.54; p < 0.001). However, stratified analysis indicated that HR+ was only associated with more LP-BCSD in the young women subgroup. Although HR+ was associated with more LP-non-BCSD, the predictive value of HR+ for LP-non-BCSD was eliminated after adjusting for age.

Conclusions

HR+ was related to LP-BCSD in the premenopausal population. LP-BCSD should be an optimal endpoint in future trials designed to evaluate the role of extended adjuvant endocrine therapy.

Fulvestrant in management of hormone receptor-positive metastatic breast cancer

Fulvestrant is a steroidal selective estrogen receptor degrader that was approved by the US FDA in 2002 for treatment of ER-positive metastatic breast cancer (ER + MBC) post-progression on aromatase inhibitors. In 2017, the label was updated to include endocrine therapy naive ER + MBC. While initially fulvestrant was thought to be equivalent to aromatase inhibitors with monthly dose of 250 mg intramuscular injection, several postmarketing trials challenged this understanding. Subsequently, the recommended dose changed to 500 mg monthly plus loading dose, and this was proven to be superior to anastrozole in efficacy. Most recently the results of FALCON trial have further challenged the way fulvestrant is viewed and used. This report provides a historical perspective on this compound, its evolving role in management of ER + MBC and what the future may hold for this drug.

Tumor-derived exosomes: Potential biomarker or therapeutic target in breast cancer?

Exosomes are released by normal and tumour cells, including those involved in breast cancer, and provide a means of intercellular communications. Exosomes with diameters ranging between 30-150 nm are involved in transferring biological information, via various lipids, proteins, different forms of RNAs, and DNA from one cell to another, and this can result in reprogramming of recipient cell functions. These vesicles are present in all body fluids, for example, blood plasma/serum, semen, saliva, cerebrospinal fluid, breast milk, and urine. It has been recently reported that these particles are involved in the development and progression of different tumor types, including breast cancer. Furthermore, it has been suggested that exosomes have the potential to be used as drug transporters, or as biomarkers. This review highlights the potential roles of exosomes in normal and breast cancer cells and their potential applications as biomarkers with special focus on their potential applications in treatment of breast cancer.

Harnessing benefit from targeting tumor associated carbohydrate antigens

Integrating additive or synergistic antitumor effects that focus on distinct elements of tumor biology are the most rational strategies for cancer treatment. Treatments for breast cancer have increased overall survival, but remain limited by lack of efficacy in a subset of breast cancer patients. The real challenge is to define what elements of tumor biology make the most sense to be integrated. An emerging strategy is to consider a systems biology approach to impact multiple interactions in networks as compare with hitting a specific protein-protein interaction target. In this review, we consider how targeting tumor associated carbohydrate antigens (TACA) that are fundamental to signal pathways might be tailored to harness benefit from combination therapy of sustained immunity with chemotherapy. An approach we are developing makes use of a carbohydrate mimetic peptide (CMP) to induce polyspecific antibodies, which by their nature have numerous on and off target effects. Linking multi-target TACA recognition with mechanisms affecting tumor growth in the context of network heterogeneity and concepts of immune surveillance to tumor cells and the type of breast cancer patients that would benefit from such an approach provides a novel integrative treatment.

[Molecular pathology for breast cancer: Importance of the gene expression profile]

Gene expression arrays are currently used to guide therapy decisions in breast cancer. The indications for gene expression tests are especially important in the group of hormone receptor negative, HER2 positive tumors to decide whether endocrine therapy alone is sufficient or additional chemotherapy is necessary. In this group of luminal tumors conventional clinicopathological parameters are often not suitable to select patients who would benefit from an endocrine therapy alone. Gene expression tests can provide additional information and, therefore, support decision-making and avoid unnecessary chemotherapy. There are a variety of test systems available which poses the questions of which tests should be selected for which patients and how the test results should be evaluated in a direct comparison. This report provides information about three currently available gene expression tests (i.e. OncotypeDx®, Endopredict® and PAM50/Prosigna®), comments on similarities and differences and discusses the impact on therapy decisions. The focus of this article is on a discussion of clinical studies that have compared the different molecular tests in the same clinical study cohort. These investigations allow a first comparative evaluation of the various assays for breast cancer.

Extracellular vesicles in breast cancer drug resistance and their clinical application

Drug resistance currently represents a daunting challenge in the treatment of breast cancer patients. With an increased understanding of the underlying mechanisms of drug resistance, the role of extracellular vesicles (EVs) in the development of chemo-insensitivity attracts extensive attention. EVs are membrane-limited, cell type-dependent vesicles that are secreted by normal or malignant cells. EVs comprise various types of contents, including genetic cargoes, proteins, and specific lipids. The characteristics of the contents determine their specific functions in not only physiological but also pathological conditions. It has been demonstrated that miRNAs and proteins in EVs are strongly correlated with breast cancer drug resistance. Additionally, they may exert an influence on de novo and acquired resistance bioprocesses. With the advances in extraction and detection technologies, EVs have also been employed to precisely diagnose and predict the outcome of therapy in breast cancer. On the other hand, they can also be exploited as efficient delivery system in future anticancer applications. In this paper, we summarized relative mechanisms concerning the relationship between EVs and breast cancer drug resistance, and then, we provide up-to-date research advances in the clinical application of EVs.