Breast Cancer Advances: From Traditional Treatments to the Promise of MSC-Derived Exosomes

Breast cancer (BC) remains a significant global health challenge, representing the most common cancer type in women and a leading cause of cancer-related death worldwide. While traditional treatments like radiotherapy and chemotherapy have been the gold standard for decades, their limitations – including treatment resistance and significant side effects – are driving research into novel therapeutic approaches. Recent attention has turned to mesenchymal stem cell (MSC)-derived exosomes as a promising next-generation intervention, though challenges remain before widespread clinical application.

Understanding Breast Cancer: Incidence, Mortality, and Disparities

In 2022, approximately 2.3 million new cases of breast cancer were reported globally, resulting in 670,000 deaths [1]. Considering both sexes, breast cancer is the second most common cancer diagnosis and the fourth leading cause of cancer-related mortality [1]. However, the burden of the disease is not evenly distributed. Incidence rates vary dramatically, ranging from 5.0 per 100,000 in Bhutan to 113.2 per 100,000 in Belgium [1]. Mortality rates also exhibit significant disparities, ranging from 2.6 per 100,000 in Bhutan to 42.2 in Barbados [1]. These regional differences are attributed to factors like age structure, risk factor prevalence, lifestyle, and healthcare infrastructure.

Limitations of Traditional Treatments

Despite the effectiveness of radiotherapy and chemotherapy, these treatments often face challenges. The development of treatment resistance can lead to disease progression and recurrence. Both modalities are associated with a substantial burden of adverse effects. Approximately 90% of patients undergoing breast radiotherapy experience acute dermatitis [1], and chemotherapy-induced peripheral neuropathy affects up to 72.9% of breast cancer patients, with symptoms persisting in around 31% even two months post-treatment [1]. These side effects, stemming from the non-specific targeting of rapidly proliferating cells, can significantly impact a patient’s quality of life.

Mesenchymal Stem Cells and Exosomes: A New Frontier

Mesenchymal stem cells (MSCs) have garnered interest due to their immunomodulatory and tissue repair capabilities [1]. MSCs can be sourced from adult and perinatal tissues, with umbilical cord-derived MSCs often exhibiting superior biological characteristics. However, concerns regarding the administration of whole MSCs – including potential tumor proliferation and adverse effects like thromboembolism and fibrosis – have shifted focus towards MSC-derived exosomes.

Exosomes are nano-sized vesicles containing proteins, lipids, and nucleic acids that mediate intercellular communication and influence the tumor microenvironment. Preclinical studies suggest that MSC-derived exosomes can suppress angiogenesis and halt cancer growth by inhibiting vascular endothelial growth factor (VEGF) [1]. However, research also indicates that MSC-derived exosomes can, paradoxically, promote tumor growth depending on their tissue origin and cargo.

Challenges and Future Directions

The dual functionality of MSC-derived exosomes – both tumor-suppressing and tumor-promoting – highlights the need for further research to identify and isolate exosomes with consistent therapeutic effects. Before clinical integration, it is crucial to distinguish between exosomes that inhibit tumor progression and those that accelerate it. Continued investigation into the specific cargo of exosomes and their impact on the tumor microenvironment is essential to unlock their full potential as a targeted therapy for breast cancer.

Breast Cancer Incidence in Younger Women

While most breast cancers are diagnosed in women over 45, incidence rates are slowly increasing among younger women. In 2022, 27,136 new cases of breast cancer were reported in women under 45 in the United States [3]. From 2001 to 2022, incidence among younger women increased by an average of 0.7% per year, with a more pronounced increase of 1.1% per year from 2012 to 2022 [3]. Incidence rates have increased across all racial and ethnic groups, with the most significant increases observed among non-Hispanic American Indian or Alaska Native women (2.1%) and non-Hispanic Asian and Pacific Islander women (1.3%) [3]. Despite this, breast cancer mortality rates have decreased among most racial and ethnic groups.