Cancer News, Good and Bad
One of the reasons cancer therapy is effective is that conventional drugs are somewhat indiscriminate toxins. Thus, they kill lots of tumor cells, even if those cells are not similar in their molecular properties. This is a good thing since most tumor masses are thought to be heterogeneous at the cell and molecular levels.
The bad news is that indiscriminate toxins can also damage normal tissues. Hence, the agony of awful side effects that accompanies cancer treatment.
A new study (with 30 authors from several research centers in Canada and Britain) describes an incredibly detailed look at how a single tumor—metastatic breast cancer—acquires genetic heterogeneity over time (Nature 461 [8 October 2009], 809–813).
Starting from the initial diagnosis, the research team measured genetic changes over nine years that eventually led to spread of the cancer to other body sites.
The result? Significant molecular evolution occurs as a tumor grows and then spreads. This is the source for tumor cell heterogeneity and ultimately is why some cancer cells will be eradicated by therapy and others not.
It is also a real challenge to personalized medicine to create drugs that will target every variant cell type rather than indiscriminately carpet-bombing them all. Luckily, this new work is a starting point for doing just that.