Formaldehyde and Cancer Pain Figure 7. Inhibition of TRPV1 antagonists or formaldehyde scavengers on rat MRMT-1 bone cancer pain behaviors. (A) Radiological confirmation of tumor development in the tibia of MRMT-1 pain model rats. (B) Scores related to the tibia (bone) in different treatment groups. n = 4. (C) Thermal hyperalgesia. Formaldehyde scavengers resveratrol (Res, 0.4 mg/ml) and glutathione (GSH, 25 mg/ml), TRPV1 antagonists capsazepine (CPZ, 0.1 mg/ml) and melatonin (MT, 5 mg/ml) increased hot plate latency. (D) Mechanical allodynia. Res, GSH, CPZ and MT increased mechanical threshold. * p,0.05, ** p,0.01; # p,0.05, ## p,0.01, $ p,0.05, compared with respective PBS groups. n = 10. Killed: heat-killed group. doi:10.1371/journal.pone.0010234.g007 patients with breast pain [66]. Nineteen breast cancer pain patients and 6 normal women carried out the clinical pain assessment by doctors. Tumor samples from 19 breast cancer patients and clinic data were provided by the Department of General Surgery, Peking University Third Hospital. Tissues adjacent to breast cancer were adipose tissue and were not used in this study. Tumor samples from 10 lung cancer patients which included adenocarcinoma, squamous cell carcinoma and pulmo- nary lymphoma were provided by the Department of Thoracic Surgery, Peking University People’s Hospital, tissues adjacent to cancer were obtained from 4 lung cancer patients. Both cancer tissues and tissues adjacent to cancer were frozen immediately with and stored in liquid nitrogen until they were used for evaluation of formaldehyde concentration. Bone cancer pain rat model A rat bone cancer pain model was established using Sprague- Dawley rats with MRMT-1 rat mammary gland carcinoma in a manner similar to that in a previous report [67]. After anesthesia, the tibia was carefully exposed and a 23-gauge needle was inserted into the intramedullary canal of the bone. It was then removed and replaced with a long thin blunt needle attached to a 10-ml Hamilton syringe containing carcinoma cells. A volume of 4 ml containing MRMT-1 cancer cells (46104), heat-killed cancer cells PLoS ONE | www.plosone.org 11 April 2010 | Volume 5 | Issue 4 | e10234