CCL2 mediates cross-talk between cancer cells and stromal fibroblasts that regulates breast cancer stem cells

Tumor-stromal interactions in breast tumor progression--significance of histological heterogeneity of tumor-stromal fibroblasts

INTRODUCTION

Existing pathological diagnostic protocols for breast cancer do not fully reflect the biological characteristics of tumor stromata. To improve the pathological diagnosis of breast cancer, a new pathological diagnostic method capable of assessing the degree of breast cancer malignancy based on the histological features of the tumor stroma is needed.

AREAS COVERED

The presence of a fibrotic focus (FF), which consists of fibroblasts or collagen fibers, and the presence of atypical tumor-stromal fibroblasts are significantly associated with nodal metastasis or distant-organ metastasis in patients with invasive ductal carcinoma (IDC) of the breast. FF is the only factor that is significantly associated with an increase in tumor angiogenesis. The importance of FF and atypical tumor-stromal fibroblasts clearly indicates that the malignant potential of IDC does not depend only on the biological characteristics of the tumor cell, but also on those of the tumor stroma.

EXPERT OPINION

The biological characteristics of fibroblasts forming an FF or atypical tumor-stromal fibroblasts probably differ from those of fibroblasts located outside an FF or ordinary tumor-stromal fibroblasts. Thus, similar to tumor cells, the heterogeneity of tumor-stromal fibroblasts probably influences the outcome of patients with IDC of the breast.

Oxidative stress and cancer: an overview

Reactive species, which mainly include reactive oxygen species (ROS), are products generated as a consequence of metabolic reactions in the mitochondria of eukaryotic cells. In normal cells, low-level concentrations of these compounds are required for signal transduction before their elimination. However, cancer cells, which exhibit an accelerated metabolism, demand high ROS concentrations to maintain their high proliferation rate. Different ways of developing ROS resistance include the execution of alternative pathways, which can avoid large amounts of ROS accumulation without compromising the energy demand required by cancer cells. Examples of these processes include the guidance of the glycolytic pathway into the pentose phosphate pathway (PPP) and/or the generation of lactate instead of employing aerobic respiration in the mitochondria. Importantly, ROS levels can be used as a thermostat to monitor the damage that cells can bear. The implications for ROS regulation are highly significant for cancer therapy because commonly used radio- and chemotherapeutic drugs influence tumor outcome through ROS modulation. Moreover, the discovery of novel biomarkers that are able to predict the clinical response to pro-oxidant therapies is a crucial challenge to overcome to allow for the personalization of cancer therapies.

Cancer stem cell and stromal microenvironment

BACKGROUND

Chemotherapeutic resistance and local recurrence or distant organ metastasis are the major causes of cancer mortality. Conventional cancer treatments do not consistently prevent cancer recurrence.

METHODS

We illustrate the key roles that cancer stem cells and the tumor microenvironment-particularly the lymph node stromal microenvironment-play in tumor drug resistance, metastasis, and recurrence in 2 representative cancers: colorectal cancer and follicular lymphoma.

CONCLUSION

We believe that combination treatment with chemotherapeutic agents in conjunction with targeted therapies, such as stromal/cancer stem cell signaling-targeted therapy, may effectively minimize cancer recurrence.

Biomarkers to Target Heterogeneous Breast Cancer Stem Cells

Breast cancer is the most common cancer and the second leading cause of death in U.S. women. Due to early detection and advanced treatment, the breast cancer death rate has been declining since 1990. However, disease recurrence is still the major obstacle in moving from therapy to truly curative treatments. Recent evidence has indicated that breast cancer recurrence is often caused by a subpopulation of breast cancer cells. This subset of cancer cells, usually referred to as breast cancer stem cells (BCSCs), exhibits stem cell phenotypes. They can self-renew and asymmetrically divide to more differentiated cancer cells. These cells are also highly resistant to conventional therapeutic reagents. Therefore, identifying and characterizing these BCSC subpopulations within the larger population of breast cancer cells is essential for developing new strategies to treat breast cancer and prevent recurrence. In this review article, we discuss the current proposed model for the origin of tumor heterogeneity, summarize the recent findings of cell surface and cytoplasmic markers for BCSC identification, review the regulatory mechanisms by which BCSCs maintain or non-cancer stem cells acquire BCSC characteristics, describe the proposed strategies to eliminate BCSCs, and highlight the current limitations and challenges to translate basic BCSC research to clinical application including establishment of clinical biomarkers and therapeutic treatments specifically targeting BCSCs.

Conservative surgery in the Zollinger-Ellison syndrome

Breast cancer stem cells have been known to contribute immensely to the carcinogenesis of the breast and therapeutic resistance in the clinic. Current studies show that the population of breast cancer stem cells is heterogeneous, involving various cellular markers and regulatory signaling pathways. In addition, different subtypes of breast cancer exhibit distinct subtypes and frequencies of breast cancer stem cells. In this review, we provide an overview of the characteristics of breast cancer stem cells, including their various molecular markers, prominent regulatory signaling, and complex microenvironment. The cellular origins of breast cancer are discussed to understand the heterogeneity and diverse differentiations of stem cells. Importantly, we also outline the recent advances and controversies in the therapeutic implications of breast cancer stem cells in different subtypes of breast cancer.