A large body of evidence supports the notion that a high numbers of tumor-infiltrating neutrophils predict a poor clinical outcome in cancer patients, and current evidence strongly suggests that infiltrating neutrophils promote cancer progression primarily by stimulating tumor angiogenesis.43, 46 VEGF, IL-8, and MMP-9 are three of the most important factors responsible for tumor angiogenesis,47 and our present results indicate that under the influence of low pH and fever-range hyperthermia, neutrophils markedly increase their ability to release these proangiogenic factors. This evidence concerns the gene MMP9 and cancer.