New Insights into the Role of Infection,Immunity and Apoptosis in the Genesis of the Cancer Stem Cell

Understanding the pathomechanism of cancer is of primary interest in medical research (Trosko and Rauch, 1998; Bjerkvig et al., 2005). In the past century, several mechanisms were proposed. It was hypothesized that cancer arises from a single cell that loses its differentiated state through sequential mutations. This initiation-promotion-progression concept explains the steps in a sequential process. Later, this hypothesis led to the mutagenic and recently the oncogenic theories, which hypothesize that defects in tumor suppressor genes are responsible for the development of cancer. The impairment of cell-to-cell communication as a cause of cancer has also been postulated.

One fascinating finding is that immunosuppressive cytotoxic antineoplastic therapies may, on occasion, cause the regression of a clinically established cancer. At first, applying this as a therapeutic strategy may seem counterintuitive, considering the fundamental role of the immune system in protecting the body against infectious organisms and aberrant cells. In addition, cancer itself is frequently immunosuppressive, so exacerbating a pre-existing immunosuppression may not seem like a rational strategy.