For example, recently studies show that CD271, a cancer stem cell biomarker of HPC, can be a promising therapeutic target.57 However, CSCs can be involved in cancer recurrence owing to their tumorigenic properties and supposed resistance to many conventional therapies.54 Breast CSCs grown in culture are resistant to chemotherapeutic agents 58 and are much harder to be eliminated than other cancer cells.59 This evidence concerns the gene NGFR and cancer.