Previous studies have not determined the sequential mechanism by which transcutaneous CO2 suppresses growth of epithelial tumors, including SCCs. Moreover, there is no report that transcutaneous CO2 suppresses lymphogenous metastasis using human cancer cell xenografts. MFH and osteosarcoma mainly metastasize hematogenously, however both hematogenous and lymphogenous metastases occur from SCCs. Lymphogenous metastasis, rather than hematogenous metastasis, is often observed in SCCs in clinical settings. Here, we suggest that transcutaneous CO2 may reduce hypoxia and induce mitochondrial pathways in SCC. In this study, we investigated whether transcutaneous CO2 can induce tumor cell apoptosis and suppress lymphogenous metastatic spread to the regional lymph nodes in human SCC. The prognosis of patients with advanced SCC remains poor because it is often hard to control lymph node metastasis. Therefore, to improve prognosis, it is important not only to suppress tumor growth at the primary site but also to prevent lymph node metastasis. Surgical excision is the most effective therapy for SCC patients; however, resection of advanced disease can have serious cosmetic and functional consequences, making it difficult for these patients to be rehabilitated in a social sense. On the other hand, although chemotherapy and radiotherapy may cause less dysfunction, these therapies are often ineffective and associated with a poor prognosis because of local recurrence and metastasis. NSC308848 Furthermore, when oral cancer has metastasized to lung, bone, or other distant organs, it is difficult to both achieve radical cure and maintain quality of life. Although various combinations of surgery, chemo-radiotherapy and other treatments have been studied, there are numerous problems regarding effectiveness and adverse effects: further LY-294,002 hydrochloride research is needed. Hypoxia is common in solid tumors, including SCCs, and can increase the invasiveness and metastatic ability of tumor cells. A hypoxic microenvironment induces various molecular pathways that allow tumor cells to become resistant to chemotherapy and radiotherapy.