Unfortunately, these therapies have not been confirmed to be clinically beneficial. Mitochondria play important roles in cellular energy metabolism and apoptosis. Alterations in respiratory activity and mtDNA mutations have been reported in various malignant tumors. Cancer cells produce their energy through the glycolytic pathway under anaerobic conditions. We targeted the differences of mitochondrial energy metabolism between normal and cancer cells, and hypothesized that improving hypoxic and aerobic conditions should be useful and important for cancer treatment. Although mitochondria proliferate independently from cancer cells, the speed of cancer cell division and proliferation is more likely faster than mitochondria under hypoxic conditions. Therefore, while cancer cells exhibit abnormal proliferation,, the number of mitochondria decreases in cancer cells under hypoxic conditions, and mitochondrial dysfunction results in avoiding apoptosis in tumor tissue. Apoptosis, a genetically encoded program for cell death that can be activated under physiological conditions, may be an important safeguard against tumor development. Therefore, a current focus in cancer therapy research is improving understanding of apoptotic pathways and development of agents that target them. We have also reported that an increased number of mitochondria induces apoptosis in sarcoma cells, and we speculate this phenomenon does not occur in normal tissue without cancer cell proliferation. In this study, we examined that transcutaneous CO2 inhibits SCC tumor growth in vivo by increasing the number of mitochondria and activating mitochondrial apoptosis by reducing intra-tumoral hypoxia. We have previously shown that transcutaneous CO2 system causes absorption of CO2 and increase in O2 MRS 1845 pressure in treated tissue, potentially causing an ����Artificial Bohr Effect����. CO2 therapy significantly decreases MRS 1191 expressions of both HIF-1a and VEGF in human MFH, which suggests that CO2 therapy reduces hypoxia in the treated tumor tissue. Based on these findings, we investigated whether making the environment of SCCs less hypoxic by using transcutaneous CO2 induces tumor cell apoptosis and suppresses lymphogenous metastasis to the regional lymph nodes by a mitochondrial pathway.