Cutaneous metastases of breast cancer during adjuvant chemotherapy correlates with increasing CD44+/CD24- and ALDH-1 expression: a case report and literature review

The Significance of Aldehyde Dehydrogenase 1 in Cancers

The goal of this paper is to discuss the role of ALDH isozymes in different cancers, review advances in ALDH1-targeting cancer therapies, and explore a mechanism that explains how ALDH expression becomes elevated during cancer development. ALDH is often overexpressed in cancer, and each isoform has a unique expression pattern and a distinct role in different cancers. The abnormal expression of ALDHs in different cancer types (breast, colorectal, lung, gastric, cervical, melanoma, prostate, and renal) is presented and correlated with patient prognosis. ALDH plays a significant role in various cellular functions, such as metabolism, oxidative stress response, detoxification, and cellular differentiation. Among the ALDH families, ALDH1 has gained considerable attention as a cancer stem cell (CSC) marker due to its significant role in the maintenance of stemness and the differentiation of stem cells (SCs), along with its involvement in tumorigenesis. A description of the cellular mechanisms and physiology of ALDH1 that underlies cancer development is provided. Moreover, current advances in ALDH1-targeting cancer therapies are discussed.

ALDH1: A potential therapeutic target for cancer stem cells in solid tumors

Solid tumors can be divided into benign solid tumors and solid malignant tumors in the academic community, among which malignant solid tumors are called cancers. Cancer is the second leading cause of death in the world, and the global incidence of cancer is increasing yearly New cancer patients in China are always the first. After the concept of stem cells was introduced in the tumor community, the CSC markers represented by ALDH1 have been widely studied due to their strong CSC cell characteristics and potential to be the driving force of tumor metastasis. In the research results in the past five years, it has been found that ALDH1 is highly expressed in various solid cancers such as breast cancer, lung cancer, colorectal cancer, liver cancer, gastric cancer, cervical cancer, esophageal cancer, ovarian cancer, head,and neck cancer. ALDH1 can activate and transform various pathways (such as the USP28/MYC signaling pathway, ALDH1A1/HIF-1α/VEGF axis, wnt/β-catenin signaling pathway), as well as change the intracellular pH value to promote formation and maintenance, resulting in drug resistance in tumors. By targeting and inhibiting ALDH1 in tumor stem cells, it can enhance the sensitivity of drugs and inhibit the proliferation, differentiation, and metastasis of solid tumor stem cells to some extent. This review discusses the relationship and pathway of ALDH1 with various solid tumors. It proposes that ALDH1 may serve as a diagnosis and therapeutic target for CSC, providing new insights and new strategies for reliable tumor treatment.

The Role of Breast Cancer Stem Cells in Chemoresistance and Metastasis in Triple-Negative Breast Cancer

Triple negative breast cancer (TNBC) remains an aggressive disease due to the lack of targeted therapies and low rate of response to chemotherapy that is currently the main treatment modality for TNBC. Breast cancer stem cells (BCSCs) are a small subpopulation of breast tumors and recognized as drivers of tumorigenesis. TNBC tumors are characterized as being enriched for BCSCs. Studies have demonstrated the role of BCSCs as the source of metastatic disease and chemoresistance in TNBC. Multiple targets against BCSCs are now under investigation, with the considerations of either selectively targeting BCSCs or co-targeting BCSCs and non-BCSCs (majority of tumor cells). This review article provides a comprehensive overview of recent advances in the role of BCSCs in TNBC and the identification of cancer stem cell biomarkers, paving the way for the development of new targeted therapies. The review also highlights the resultant discovery of cancer stem cell targets in TNBC and the ongoing clinical trials treating chemoresistant breast cancer. We aim to provide insights into better understanding the mutational landscape of BCSCs and exploring potential molecular signaling pathways targeting BCSCs to overcome chemoresistance and prevent metastasis in TNBC, ultimately to improve the overall survival of patients with this devastating disease.