Int J Hyperthermia, 2010 vol. 26(3) pp. 232-46
Lee, CT; Mace, T; Repasky, EA
Hypoxia within the tumor microenvironment is correlated with poor treatment outcome after radiation and chemotherapy, and with decreased overall survival in cancer patients. Several molecular mechanisms by which hypoxia supports tumor growth and interferes with effective radiation and chemotherapies are now well established. However, several new lines of investigation are pointing to yet another ominous outcome of hypoxia in the tumor microenvironment: suppression of anti-tumor immune effector cells and enhancement of tumor escape from immune surveillance. This review summarizes this important information, and highlights mechanistic data by which hypoxia incapacitates several different types of immune effector cells, enhances the activity of immunosuppressive cells and provides new avenues which help “blind” immune cells to the presence of tumor cells. Finally, we discuss data which indicates that mild thermal therapy, through its physiologically-regulated ability to alter vascular perfusion and oxygen tensions within the tumor microenvironment, as well as its ability to enhance the function of some of the same immune effector activities that are inhibited by hypoxia,, could be used to rapidly and safely release the tight grip of hypoxia in the tumor microenvironment thereby reducing barriers to more effective immune-based therapies.