A new era of cancer therapy: cancer cell targeted therapies are coming of age.

The large majority of today's cancer therapies are based on the removal of solid tumor masses (for example by surgery when possible) and a plethora of chemical or physical treatments such as chemo- and radiotherapy which induce death of particularly sensitive or rapidly growing cells. These approaches are variously combined in order to optimize therapeutic indices. While in some cases, such as childhood leukemia, these treatments may cure patients, it is common knowledge that they are associated with serious side effects. The main conceptual reason for this is that neither cancer cells nor the cancer cause(s) are directly targeted. In addition to a high toxicity and a low quality of life, these traditional therapies can give rise to therapy-induced secondary cancers. Here we will neither discuss the various optimization possibilities nor arguments for and against established therapies. Rather we want to reflect about recent advances, challenges and perspectives of cancer therapeutic concepts which aim at increasing cancer-selectivity. More precisely, we will discuss two such concepts from a cell biological and molecular oncology perspective, namely to (i) target the cause of the cancer and (ii) to (re)activate specific endogenous pathways for cancer cell-selective apoptosis.