title: Suppressive effects of a proton beam on tumor growth and lung metastasis through the inhibition of metastatic gene expression in 4T1 orthotopic breast cancer model.
abstract: A proton beam is a next generation tool to treat intractable cancer. Although the therapeutic effects of a proton beam are well known, the effect on tumor metastasis is not fully described. Here, we investigated the effects of a proton beam on metastasis in highly invasive 4T1 murine breast cancer cells and their orthotopic breast cancer model. Cells were irradiated with 2, 4, 8 or 16 Gy proton beam, and changes in cell proliferation, survival, and migration were observed by MTT, colony forming and wound healing assays. 4T1 breast cancer cell-implanted BALB/c mice were established and the animals were randomly divided into 4 groups when tumor size reached 200 mm3. Breast tumors were selectively irradiated with 10, 20 or 30 Gy proton beam. Breast tumor sizes were measured twice a week, and breast tumor and lung tissues were pathologically observed. Metastasis-regulating gene expression was assessed with quantitative RT-PCR. A proton beam dose-dependently decreased cell proliferation, survival and migration in 4T1 murine breast cancer cells. Also, growth of breast tumors in the 4T1 orthotopic breast cancer model was significantly suppressed by proton beam irradiation without significant change of body weight. Furthermore, fewer tumor nodules metastasized from breast tumor into lung in mice irradiated with 30 Gy proton beam, but not with 10 and 20 Gy, than in control. We observed correspondingly lower expression levels of urokinase plasminogen activator (uPA), uPA receptor, cyclooxygenase (COX)-2, and vascular endothelial growth factor (VEGF), which are important factors in cancer metastasis, in breast tumor irradiated with 30 Gy proton beam. Proton beam irradiation did not affect expressions of matrix metalloproteinase (MMP)-9 and MMP-2. Taken together, the data suggest that, although proton beam therapy is an effective tool for breast cancer treatment, a suitable dose is necessary to prevent metastasis-linked relapse and poor prognosis.
authors.affiliation: Intractable Disease Research Center and Department of Pharmacology, School of Medicine, Dongguk University, 38066 Gyeongju, Republic of Korea.
authors.forename: Yun-Suk
authors.initials: YS
authors.lastname: Kwon
authors.affiliation: Intractable Disease Research Center and Department of Pharmacology, School of Medicine, Dongguk University, 38066 Gyeongju, Republic of Korea.
authors.forename: Kyu-Shik
authors.initials: KS
authors.lastname: Lee
authors.affiliation: Intractable Disease Research Center and Department of Pharmacology, School of Medicine, Dongguk University, 38066 Gyeongju, Republic of Korea.
authors.forename: So-Young
authors.initials: SY
authors.lastname: Chun
authors.affiliation: Department of Pathology, School of Medicine, Dongguk University, 38066 Gyeongju, Republic of Korea.
authors.forename: Tae Jung
authors.initials: TJ
authors.lastname: Jang
authors.affiliation: Intractable Disease Research Center and Department of Pharmacology, School of Medicine, Dongguk University, 38066 Gyeongju, Republic of Korea.
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Nam
mesh_terms: D000818:Animals; D001835:Body Weight / Q000528:radiation effects; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D002465:Cell Movement / Q000528:radiation effects*; D049109:Cell Proliferation / Q000528:radiation effects; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D051379:Mice; D009362:Neoplasm Metastasis / Q000473:pathology / Q000532:radiotherapy; D055293:Receptors, Urokinase Plasminogen Activator / Q000096:biosynthesis; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis
chemical_list: D055293:Receptors, Urokinase Plasminogen Activator; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D014568:Urokinase-Type Plasminogen Activator; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9