Cancer stem cells (CSCs) are a specific type of cancer cell that can both self-renew and differentiate, playing a key role in cancer development and progression. Existing clinical biomarkers, however, are insufficient as robust biomarkers to be used in clinical practice for cancer patients due to their limited confirmation and contested prognostic relevance. Therefore, there is a large pool of potential biomarkers that have not been thoroughly explored. CSC surface biomarkers have recently been the focus of many studies in the clinical practice of cancer patients due to their potential utility in characterising the aetiology of cancer initiation, development, and metastasis. In this chapter, we discuss the most popular surface biomarkers of CSCs and provide their potential utility in cancer diagnosis and prognosis.

Nanobodies (Nbs) are great molecular tools that can circumvent the limitations of traditional antibodies such as large size, low stability, slow clearance, and high immunogenicity. Recent studies identified several clinical applications of Nbs targeting various cancers. Cancer stem cells (CSCs) comprise a limited subpopulation of cancer cells that can reproduce autonomously and differentiate into diverse cancer lineages. CSCs are responsible for providing resistance against chemotherapy and radiotherapy. Various studies focused on targeting these CSCs via Nbs to selectively reduce the cancer burden. Nbs have the potential to reduce the CSCs and thereby could halt the progression of specific cancers.