Lung cancer stem cells and low-intensity laser irradiation: a potential future therapy?

Lung cancer is notably a significant threat when considering worldwide cancer-related deaths. Despite significant advances in treatment modalities, death rates as a result of cancer relapse remain high. Relapse can occur as a result of metastasis. Cancer stem cells (CSCs) have been implicated as an important contributory factor in the development of metastasis. CSCs have the same characteristics as normal stem cells; that is, they can proliferate indefinitely and are capable of both self-renewal and differentiating into specialized cells. The molecular and cellular characteristics of stem cells and CSCs are coded for by cell-specific genes, which can be analyzed by using molecular assays setting the standard to work from. Low-intensity laser irradiation (LILI) has been applied in the treatment of numerous diseases and pathological conditions. LILI has been shown to stimulate proliferation of cells, capillary growth, and cellular metabolism as observed by adenosine triphosphate activation. It has been shown, by using different dosing levels of LILI, to either stimulate or inhibit cellular functions. One treatment strategy used on cancer cells is photodynamic therapy (PDT), in which cancer cells are treated with a photosensitizer (PS) in combination with laser irradiation. PSs are nontoxic by themselves but, with light activation, cause reactive oxygen species generation, which causes cancer cell death. Cell-specific PSs are being developed for future cancer treatment. In this review, we look at the potential effects of LILI and PDT on lung CSCs.