Cancer immunologists and cancer biologists: Why we didn't talk then but need to now

Abstract

What is cancer? Cancer is a disease initiated by a series of cumulative genetic and epigenetic changes that occur in a normal cell. However, in addition to the malignant cell itself, cancer is a disease of microenvironment and immunity. Although genetic and epigenetic alterations drive cellular transformation, genomic plasticity, and evolution, it has become increasingly apparent that multiple signals delivered within the tumor microenvironment by modifier genes, stromal and endothelial cells, and immune cells are critical factors in determining the progression versus dormancy or destruction of an initiated lesion and also whether metastasis may occur. With regard to the important roles of immune cells in cancer, a chasm exists between immunologists and biologists: although sharing a common disease interest, there is little history for workers to draw on based on shared perspectives or understanding. How did this disconnect arise? Here, we look at how these workers became separated in the past and address why it has now become critical to spur greater cross-fertilization. In particular, we highlight three ideas that we believe are important for discussion and debate. The first idea is that therapeutic strategies that fail to harness the immune system will always be defeated by tumor resistance, due to the large "genomic space" that genetically plastic tumor cells can readily access to evolve resistance mechanisms. Because all therapies drive tumor progression by imposing a selection for resistant cells, harnessing the adaptivity of the immune system will be indispensable to ultimately stanching the deadly adaptability of the tumor cell. The second idea is that using molecular targeted agents to reverse tumoral immune suppression may offer a powerful method to leverage the efficacy of most if not all therapeutic agents. We suggest that the mechanisms that support evolution of a "smoldering" inflammatory environment in cancer overlap with those that support evolution of tumoral immune escape. If true, relieving immune suppression will switch the inflammatory state from supportive to destructive for the tumor. The third idea is that by ablating immunosuppression mechanisms, cytotoxic chemotherapy might synergize with, rather than antagonize, active immunotherapy. Provocative preclinical studies in this area prompt clinical attention. We believe that increased efforts to intermingle the perspectives and work of cancer immunologists with cancer biologists and pharmacologists will be needed to realize the National Cancer Institute's goal of managing cancer in the clinic by 2015. ©2007 American Association for Cancer Research.