Most chemotherapeutic drugs today are targeting mature cancer cells… are these cancer drugs targeted at the wrong kinds of cells?
This is a pretty tough problem. While we know that currently available cancer drugs dramatically reduce the size of tumors, we also know that MOST cancers will eventually recur. There is some amazing, pioneering work being done in universities, non-profits (like HudsonAlpha), and biopharma to address this issue. Some research we’ve reviewed points toward small populations of cells — “cancer stem cells” or “CSC”s — that are ultimately responsible for the growth of tumors and are resistant to current therapies.
Most of our existing cancer treatments have been developed based on animal models, where therapies that can show ability to promote tumor shrinkage were considered effective. Most mice do not live beyond 1-2 years so using that model to assess relapse is not practical.
Also, the efficacy of cancer treatments is, in the initial stages of testing, often measured by the ablation fraction of tumor mass (fractional kill). Since the theory is that CSCs form a very small proportion of a given tumor, this may not necessarily select for drugs that act specifically on the cancer stem cells. Since conventional chemotherapies kill differentiated or differentiating cells – which form the bulk of the tumor but are unable to generate new cells – a population of CSCs, which gave rise to it, could remain untouched and cause a relapse of the disease.
More next time…
