title: Involvement of autophagy in oncogenic K-Ras-induced malignant cell transformation.
abstract: Autophagy has recently been implicated in both the prevention and progression of cancer. However, the molecular basis for the relationship between autophagy induction and the initial acquisition of malignancy is currently unknown. Here, we provide the first evidence that autophagy is essential for oncogenic K-Ras (K-Ras(V12))-induced malignant cell transformation. Retroviral expression of K-Ras(V12) induced autophagic vacuole formation and malignant transformation in human breast epithelial cells. Interestingly, pharmacological inhibition of autophagy completely blocked K-Ras(V12)-induced, anchorage-independent cell growth on soft agar. Both mRNA and protein levels of ATG5 and ATG7 (autophagy-specific genes 5 and 7, respectively) were increased in cells overexpressing K-Ras(V12). Targeted suppression of ATG5 or ATG7 expression by short hairpin (sh) RNA inhibited cell growth on soft agar and tumor formation in nude mice. Moreover, inhibition of reactive oxygen species (ROS) with antioxidants clearly attenuated K-Ras(V12)-induced ATG5 and ATG7 induction, autophagy, and malignant cell transformation. MAPK pathway components were activated in cells overexpressing K-Ras(V12), and inhibition of JNK blunted induction of ATG5 and ATG7 and subsequent autophagy. In addition, pretreatment with antioxidants completely inhibited K-Ras(V12)-induced JNK activation. Our results provide novel evidence that autophagy is critically involved in malignant transformation by oncogenic K-Ras and show that reactive oxygen species-mediated JNK activation plays a causal role in autophagy induction through up-regulation of ATG5 and ATG7.
authors.affiliation: Department of Chemistry and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea.
authors.forename: Min-Jung
authors.initials: MJ
authors.lastname: Kim
authors.forename: Soo-Jung
authors.initials: SJ
authors.lastname: Woo
authors.forename: Chang-Hwan
authors.initials: CH
authors.lastname: Yoon
authors.forename: Jae-Seong
authors.initials: JS
authors.lastname: Lee
authors.forename: Sungkwan
authors.initials: S
authors.lastname: An
authors.forename: Yung-Hyun
authors.initials: YH
authors.lastname: Choi
authors.forename: Sang-Gu
authors.initials: SG
authors.lastname: Hwang
authors.forename: Gyesoon
authors.initials: G
authors.lastname: Yoon
authors.forename: Su-Jae
authors.initials: SJ
authors.lastname: Lee
mesh_terms: D000818:Animals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D000071193:Autophagy-Related Protein 7; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology / Q000637:transplantation; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014183:Transplantation, Heterologous; D044764:Ubiquitin-Activating Enzymes / Q000096:biosynthesis / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics
chemical_list: C502778:ATG5 protein, human; D000071187:Autophagy-Related Protein 5; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D016283:Proto-Oncogene Proteins p21(ras); C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes