Tumor Microenvironmental Factors and Acridine Orange Intensity Can Predict Clinical Outcome in Soft Tissue Sarcoma Patients

Introduction: The extracellular pH (pHe) in malignant tumors is lower than in benign tumors as a result of the high metabolism of tumor cells [1]. Furthermore, high metabolism causes a lack of nutrition and oxygen in solid tumors [2]. Tumor cells grown under acidic and hypoxic conditions exhibit a more proliferative phenotype than cells grown under typical neutral conditions. However, the use of the physiological conditions of a tumor as a biomarker for malignancy has not been previously examined. Here, we assessed the effect of tumor microenvironmental factors, especially pHe, on the clinical outcome of musculoskeletal sarcomas. We also assessed the effect of tumor microenvironmental factors on the accumulation of acridine orange (AO) photodynamic agent, which has been used in intraoperative photodynamic therapy during reduction surgery in musculoskeletal sarcoma patients [3-5].