| Canine breast tumor occured frequently in the veterinary clinics. At present, breast cancer is always treated by surgery, long-term survival rate hasn't been improved. With the development of the modern technology, photodynamictherapy (PDT) Becomes a new choice to treat malignant tumor. By photosensitizer, light and oxygen molecule. Photosensitizer can be absorbed electively by pathological target tissue. Active oxygen will be produced if it is stimulated by light with suitable wavelength and treated by energy transform, and it injures the target tissue, so it is a tumor therapy method with good developing prospect which can induce apoptosis and necrosis. Hematoporphyrin monomethyl ether (HMME) is a new photosensitizer and has been proved its high performance in foundational and clinical experiments. But now, researches about the effect with HMME-PDT on canine breast tumor cell are still less at home and abroad. the new HMME, the He-Ne laser of wavelengh of 632.8nm irradiate the breast tumor cell line was used in this study to investigate mechanism of PDT on canine breast cancer CHMm cell in order to provide a basis for the treatment of canine breast cancer disease.Cell lines were collected and isolated from the clinical metastatic breast cancer, and cultured normally. Cells during exponential phase of growth were divided into groups:blank control, laser group, photosensitizer group and combined group (laser illumination and photosensitizer). HMME-PDT experiment was used for canine breast cancer CHMm cells and the OD490 was detected with MTT, also effect of PDT on the culture of canine breast tumor cells in vitro was detected and inhibition curve was drawn; then cells rate were detected with trypan blue exclusion test; apoptosis was detected with Hochest33258 stainning and electrophoretic technique; cell cycle was detected with flow cytometry; content of MDA, NO and activity of SOD, GSH-PX were detected with chromatometry; content of IL-2 and IL-6 was detected with radiommunoassay.The Were as follows: blank control, photosensitizer group (HMME20μg/mL) and laser group(2.8J/cm2) had no obvious effect on the cell multiplication, but the HMME-PDT (HMME20μg/mL+2.8J/cm2) group Cell multiplication was obviously inhibited, so it proved canine breast cancer CHMm cells in vitro were inhibited with HMME-PDT, within certain premises, photodynamic effect, photosensitizer density and illumination doses had relations; after HMME-PDT, there was obvious cellular apoptosis, and apoptosis was more obvious as time prolonging; at different time in cell cycle, rate increase of G0/G1 phrase had significant difference at 12h, 24h and 48h compared with the control group (P<0.01), however rate decrease of S phrase and G2/M phrase had obvious difference at 24h and 48h compared with the control group (P<0.01), they were all related to time, but S and G2/M was no than G0/G1 phrase. It proved mechanism of action of HMME-PDT on inhabiting cancer may be related to regulation of cell cycle, embodying block of G0/G1 cell cycle can be induced with HMME-PDT; content of MDA and NO increased, and activity of SOD and GSH-PX in different time except 0h had obvious difference compared with control group(P<0.01), this result suggested HMME-PDT might increase the content of free radical in cells to kill canine breast cancer cells by breaking oxidation-reduction equilibrium; the increase of IL-2 and decrease of IL-6 had obvious difference respectively compared with control group (P<0.01), it proved IL-2 and IL-6 might participate the kill process of HMME-PDT.
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