This article from the NY Times describes new ways to treat blood cancers (cancers of blood cells). Some of these may be approved in a few months. They involve manipulating immune system cells (also a form of blood cells) to get them to attack the cancer cells, while trying to avoid unintended concequences (like immune responses against the patient). The immune system has research advantages since the cells are very easy to obtain (just get blood) and culture (grow in a dish) compared to solid tissues. Although many blood cells look alike, there are many different kinds of immune cells based on their molecular differences and stages of development. These are among the easiest human cells to work with. The exposed position of blood cancer cells (just floating around in the blood mostly) also makes them very accessible to attack by immune cell (also floating around in the blood) approaches, whereas solid tumors might not allow such access. Trials of similar approaches are also being attempted on solid tumors.