HDAC9 and cancer: Because cancer is often a systemic rather than isolated problem and a dynamic rather than static process, we propose that anti-CSC treatments which control a whole CSC network rather than a single CSC signal pathway, such as those targeting CSC-related micro-RNA (miRNA) and histone deacetylase (HDAC), may be just as efficacious and safe as, and can be more cost-effective than, conventional salvage treatments when used at the right time in the right patients with the right cancer subtypes, and monitored with appropriate CSC biomarkers.