Clinical relevance of stem cells in lung cancer

Abstract

Lung cancer is the major cause of cancer-related deaths worldwide, it has one of the lowest 5-year survival rate, mainly because it is diagnosed in the late stage of the disease. Lung cancer is classified into two groups, small cell lung cancer (SCLC) and non-SCLC (NSCLC). In turn, NSCLC is categorized into three distinct cell subtypes: Adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. NSCLC is the most common lung cancer, accounting for 85% of all lung cancers. Treatment for lung cancer is linked to the cell type and stage of the disease, involving chemotherapy, radiation therapy, and surgery. Despite improvements in therapeutic treatments, lung cancer patients show high rates of recurrence, metastasis, and resistance to chemotherapy. Lung stem cells (SCs) are undifferentiated cells capable of self-renewal and proliferation, are resistant to chemotherapy and radiotherapy and, due to their properties, could be involved in the development and progression of lung cancer. The presence of SCs in the lung tissue could be the reason why lung cancer is difficult to treat. The identification of lung cancer stem cells biomarkers is of interest for precision medicine using new therapeutic agents directed against these cell populations. In this review, we present the current knowledge on lung SCs and discuss their functional role in the initiation and progression of lung cancer, as well as their role in tumor resistance to chemotherapy.

Keywords: Biomarkers; Cancer stem cells; Chemoresistance; Lung cancer.

Figure 1

Classification and main characteristics of lung cancer. Lung cancer is classified into two histological types, small cell lung cancer (SCLC) derived from cells of the neuroendocrine lineage and non-SCLC (NSCLC) derived from epithelial cells. NSCLC is classified into three subtypes: Adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. SCLC: Small cell lung cancer; NSCLC: Non-SCLC; AD: Adenocarcinoma; SCC: Squamous cell carcinoma; LCC: Large cell carcinoma.

Figure 2

Stem cell biomarkers in lung cancer. Biomarkers identified in cancer stem cells in lung tissue include clusters of differentiation, cell adhesion molecules, cell membrane transporters, enzymes of cell metabolism, and transcription factors. CSCs: Cancer stem cells; ABCG2: ATP-binding cassette subfamily G member 2; ALDH: Aldehyde dehydrogenase.