title: Selective inhibition of cell growth by activin in SNU-16 cells.
abstract: OBJECTIVE
  To investigate whether activin regulates the cell proliferation of human gastric cancer cell line SNU-16 through the mRNA changes in activin receptors, Smads and p21(CIP1/WAF1).
  
  
  METHODS
  The human gastric cancer cell lines were cultured, RNAs were purified, and RT-PCRs were carried out with specifically designed primer for each gene. Among them, the two cell lines SNU-5 and SNU-16 were cultured with activin A for 24, 48 and 72 h. The cell proliferation was measured by MTT assay. For SNU-16, changes in ActRIA, ActRIB, ActRIIA, ActRIIB, Smad2, Smad4, Smad7, and p21(CIP1/WAF1) mRNAs were detected with RT-PCR after the cells were cultured with activin A for 24, 48 and 72 h.
  
  
  RESULTS
  The proliferation of SNU-16 cells was down regulated by activin A whereas other cells showed no change. Basal level of inhibin/activin subunits, activin receptors, Smads, and p21(CIP1/WAF1) except for activin betaB mRNAs was observed to have differential expression patterns in the human gastric cancer cell lines, AGS, KATO III, SNU-1, SNU-5, SNU-16, SNU-484, SNU-601, SNU-638, SNU-668, and SNU-719. Interestingly, significantly higher expressions of ActR IIA and IIB mRNAs were observed in SNU-16 cells when compared to other cells. After activin treatment, ActR IA, IB, and IIA mRNA levels were decreased whereas ActR IIB mRNA level increased in SNU-16 cells. Smad4 mRNA increased for up to 48 h whereas Smad7 mRNA increased sharply at 24 h and returned to the initial level at 48 h in SNU-16 cells. In addition, expression of the p21(CIP1/WAF1), the mitotic inhibitor, peaked at 72 h after activin treatment in SNU-16 cells.
  
  
  CONCLUSIONS
  Our results suggest that inhibition of cell growth by activin is regulated by the negative feedback effect of Smad7 on the activin signaling pathway, and is mediated through p21(CIP1/WAF1) activation in SNU-16 cells.
authors.affiliation: East-West Medical Research Institute, Kyung Hee University, Seoul, South Korea.
authors.forename: Young-Il
authors.initials: YI
authors.lastname: Kim
authors.forename: Hee-Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Inkoo
authors.initials: I
authors.lastname: Khang
authors.forename: Byung-Nam
authors.initials: BN
authors.lastname: Cho
authors.forename: Ha Kyu
authors.initials: HK
authors.lastname: Lee
mesh_terms: D029404:Activin Receptors / Q000032:analysis / Q000235:genetics; D028341:Activins / Q000502:physiology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000502:physiology; D005246:Feedback; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D051785:Smad Proteins / Q000235:genetics / Q000502:physiology; D013274:Stomach Neoplasms / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D013997:Time Factors
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D012333:RNA, Messenger; D051785:Smad Proteins; D028341:Activins; D029404:Activin Receptors